简介：and Quarterly Journal of Economics).[5] The median age of authors in the 1980s and 1990s was 36. Scholars over age 50 when their studies are published are a minute fraction of all authors in these journals. Creative economics at the highest levels is mainly for the young. That is as true in the 1990s as it was in the 1960s,The evidence in section I documents the decline in productivity at the sample means. Information on the age-productivity relationship at the extremes of the sample is interesting in its own right and might help shed some light on the possible causes of the apparent decline in productivity with age. The simplest test compares productivity losses among the top early performers with that of the entire sample of economists at elite institutions. Among the top 10% of early producers the mean values of I1,Abstract--Economists' productivity over their careers and as measured by publication in leading journals declines very sharply with age. There is no difference by age in the probability that an article submitted to a leading journal will be accepted. Rates of declining productivity are no greater among the very top publishers than among others

简介：and Quarterly Journal of Economics).[5 The median age of authors in the 1980s and 1990s was 36. Scholars over age 50 when their studies are published are a minute fraction of all authors in these journals. Creative economics at the highest levels is mainly for the young. That is as true in the 1990s as it was in the 1960s,The evidence in section I documents the decline in productivity at the sample means. Information on the age-productivity relationship at the extremes of the sample is interesting in its own right and might help shed some light on the possible causes of the apparent decline in productivity with age. The simplest test compares productivity losses among the top early performers with that of the entire sample of economists at elite institutions. Among the top 10%26#37,the decline appears to be quite substantial. Between years 9-10 and 14-15 elite economists as a group lose 29 to 32%26#37

简介：and Quarterly Journal of Economics).[5 The median age of authors in the 1980s and 1990s was 36. Scholars over age 50 when their studies are published are a minute fraction of all authors in these journals. Creative economics at the highest levels is mainly for the young. That is as true in the 1990s as it was in the 1960s,The evidence in section I documents the decline in productivity at the sample means. Information on the age-productivity relationship at the extremes of the sample is interesting in its own right and might help shed some light on the possible causes of the apparent decline in productivity with age. The simplest test compares productivity losses among the top early performers with that of the entire sample of economists at elite institutions. Among the top 10%26#37,the decline appears to be quite substantial. Between years 9-10 and 14-15 elite economists as a group lose 29 to 32%26#37

简介：and Quarterly Journal of Economics).[5 The median age of authors in the 1980s and 1990s was 36. Scholars over age 50 when their studies are published are a minute fraction of all authors in these journals. Creative economics at the highest levels is mainly for the young. That is as true in the 1990s as it was in the 1960s,The evidence in section I documents the decline in productivity at the sample means. Information on the age-productivity relationship at the extremes of the sample is interesting in its own right and might help shed some light on the possible causes of the apparent decline in productivity with age. The simplest test compares productivity losses among the top early performers with that of the entire sample of economists at elite institutions. Among the top 10%26#37,the decline appears to be quite substantial. Between years 9-10 and 14-15 elite economists as a group lose 29 to 32%26#37

简介：宝利通公司日前宣布,为全新SoundPointIP桌面电话推出一套软件应用程序,采用开放式接口和日益壮大的应用合作伙伴生态系统,帮助企业实现更有效的通讯和提高工作效率,适用于普通企业和特殊行业应用。

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简介：Developinglow-carboneconomyandenhancingcarbonproductivityarebasicapproachestocoordinatingeconomicdevelopmentandprotectingglobalenvironment,whicharealsothemajorwaystoaddressclimatechangeundertheframeworkofsustainabledevelopment.Inthispaper,theauthorsanalyzetheannualrateofcarbonproductivitygrowth,thedifferencesofcarbonproductivityofdifferentcountries,andthefactorsforenhancingcarbonproductivity.Consequently,theauthorsclarifytheirviewpointthattheannualrateofcarbonproductivitygrowthcanbeusedtoweightheeffortsthatacountrytakestoaddressclimatechange,andproposepoliciesandsuggestionsonpromotingcarbonproduction.

简介：Thisarticledevelopedadecompositionmodelofenergyproductivityonthebasisoftheeconomicgrowthmodel.FourfactorswereconsideredwhichmayinfluenceChina’senergyproductivityaccordingtothismodel:technologyimprovement,resourceallocationstructure,industrialstructureandinstitutearrangement.Then,aneconometricmodelwasemployedtotestthefourfactorsempiricallyonthebasisofChina’sstatisticaldatafrom1978to2004.Resultsindicatedthatcapitaldeepeningcon-tributesthemost(207%)toenergyefficiencyimprovement,andimpactfromlaborforces(13%)istheweakestoneinresourcefactor;industrialstructure(7%)andinstituteinnovation(9.5%)positivelyimprovetheenergyproductivity.

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简介：在这份报纸，在椰子(Cocusnucifera)的一个agroforestry系统骑车的生物资源生产率和营养素与菠萝(波罗comosus)在实行套种被学习了。结果证明这个生态系统的生物资源生产率是47460kg...hm2...一?1，它4.3倍于纯椰子种植园的。在N的生物骑车，P。K元素，全部的年度保留是559.470kg...hm?2，年度回来是410.745kg...hm?2，年度举起是970.475kg...hm?2分别地。在三个滋养的元素的平均发行量率(N，P，K)是42.32%，它在纯椰子看台多于那是27.53%。椰子与菠萝在实行套种被证明是最佳之一文化模式，它有更高的生物资源生产率，和在热带区域的环境资源的更好的用法效率。

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简介：Inthisresearch,fiveplotsareselectedbasedonstandstorageandproductivityofplantedforestofLarixkaempferi(Japaneselarch)aswellastheirrelationshipwithfactorssuchasforestage,siteconditionandstandden-sity.Throughstandardplotinvestigationandmethodoftrunkanalysis,systematicresearchisconductedonstorageandproductivityoftheplantedforestandtheirrelationshipwithsitecondition.Asshownintheresearch,produc-tivityofplantedforestofLarixkaempferiinlowlatitudeareaishigherthanthatinhighlatitudeareawhilestandproductivityishigherinslightacidsoil.Contentsofpotassiumelementinthesoilhaveconsiderablein?uenceonproductivityoftheLarixkaempferiforest.

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简介：网络主要生产率(NPP)是代表生态系统的结构和函数的最重要的索引。NPP能被动态全球植被模型(DGVM)模仿，它被设计相对环境变化代表植被动力学。这研究在气候，土壤，和地形学上与数据基于DGVM综合生物圈模拟器(朱鹭)模仿了瓷器生态系统的NPP。在瓷器陆上的生态系统的NPP模拟的朱鹭的适用性首先被验证。有另外的相关研究的比较显示范围和模拟的吝啬的价值通常在观察的限制以内；全面模式和全部的年度NPP接近与另外的模型一起进行的模拟。模拟基于遥感离NPP评价也靠近。确认证明那朱鹭能在瓷器自然生态系统在NPP的大规模模拟被利用。我们然后从1961～2005与气候变化数据模仿了NPP，当温暖是特别地惹人注目的时。下列是模拟的结果。(1)全部的NPP在过去的45年里从3.61GtC/yr变化了到4.24GtC/yr并且展出了最小的重要线性增加或减少。(2)在增加的地区性的差别或在NPP的减少大，但是展出了一个不足道的全面线性趋势。NPP在大多数部分衰退了东方并且华中，特别在黄土高原。(3)类似于年度NPP的变化法律，季节的NPP也显示了不足道的增加或减少；趋势线在一般水平以内。(4)在季节的NPP变化的地区性的差别大。NPP在黄土高原在春天，夏天，和秋天衰退了，但是在西藏的高原的大多数部分增加了。

简介：为了确定黄土高原地区现有刺槐林改造的最佳间伐强度，１９９５年秋季对密度为２２２０株／公顷的９年生刺槐林进行了三种不同强度的间伐．通过间伐，降低了群落密度，减少了林冠截留率，增加了植树带内的汇流量，根系层内的土壤水分条件得到明显的改善．当间伐后的林分密度为１１１０株／公顷时，生长季内植树带土壤水分提高约４０％．随着间伐强度的增大，林木的水分生产函数曲线由直线上升变为以对数曲线上升；当间伐强度达到某一值时（保留密度为１１１０株／公顷），林木水分生产力随蒸腾量的变化曲线为抛物线．这表明此时水分已不再是林木生产的限制因子，在这种间伐强度条件下，单株林木和整个林分的水分生产力分别达到６０１７１ｇ·ｋｇ－１·ｍｍ－１和１４９７７７ｋｇ·ｈｍ－２·ｍｍ－１，因此将这一强度定为黄土高原地区刺槐林间伐的最佳强度．

简介：Plantationresourceisanimportantcomponentofforestresources.OverallplantationqualityisnothighinChina,andtheproblemslikelowgrowth,lowpreservingrateandlowproductivityarecommonlyobserved.Thispaperreviewedthehistoricalbackgroundoftheresearchonplantationproductivity,describedfactorsaffectingplantationproductivityincludingsiteconditions,initialplantingdensity,thinningmeasures,groundclearance,andcontinuousplantedalgebraandfertilization.Finally,itwasproposedtocarryoutkeytechnologysystemresearchonplantationproductivitymaintenanceandstrengthentheresearchonthelong-termness,systematicdevelopmentandmulti-purposeofplantationproductivity.

简介：China'seasternareaisatmiddleandlaterstageofindustrializationduringwhichtherelationbetweenurbanandruralareas,industryandagricultureappearsmaladjusted.Themainproblemsareshrinkageinagriculturalcomparativeearningandlackofdrivingforceofagriculturaldevelopment.BasedoncalculatingagriculturallaborproductivityineastChinafrom1996to2005,thispaperanalyzescontributingdegreeofmotiveforcesofagriculturedevelopintenprovincesandcitiesofeastChinaapplyingGCA(Greycorrelativeanalysis).TheresultsshowthatthereisnoabsolutecorrespondencebetweenthelevelofindustrializationandagriculturallaborproductivityinChina'seasternarea.Thereisnosynchronousdevelopmentbetweenindustryandagriculturallaborproductivityinsomeareas.Fertilizerandagriculturalmachineryinputhadhighcontributingdegreefortenyears;however,contributingdegreeinlandandirrigationworkinputwaslow.Non-materializationinputsbecametheleadingroleinmostprovincesandcities'increaseofagriculturallaborproductivity.Modernagriculturaldevelopmentneednon-materializationinputsasprimarymotiveforce,atthesametime,directmaterialinputandfacilityinputasguaranteedfunction.Forsomereasons,agriculturaldevelopmentischaracterizedby'moredirectmaterialinput,lessfacilityinput'ineastChinanow.OptimaldrivingforcemodeloffutureagriculturaldevelopmentineastChinaisthatnon-materializationinputsaredominant,thatperfectedfacilityinputareguarantee,andthatcertainsubstanceinputsarenecessary.

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