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排序方式: 共有109条查询结果,搜索用时 15 毫秒
101.
选取全国各省粮食生产指标面板数据,对数据进行灰色拟合处理,采用数据包络分析(DEA)法,测算各区域的粮食生产效率,得到投入产出体系的要素冗余值;同时测算了各区域的全要素生产率,并对Malmquist指数进行分解,分析各区域的效率变化和技术变化趋势.结果显示:东、西部地区粮食生产投入要素大量冗余,要素配置效率不高,中部地区要素利用率较高,要素配置趋于合理;效率变化对全要素生产率的作用不明显,而技术进步是全要素生产率增长的关键驱动因素. 相似文献
102.
均匀流量假设下分枝水平井的产能公式 总被引:4,自引:0,他引:4
将分枝水平井视为垂直裂缝,在均匀流量假设下,利用复变函数理论推导出了当分枝数分别为1和2时的分枝水平井产能公式。证明了在均匀流量假设下垂直裂缝相当的折算半径与导流能力为无限大的相比减少12%。 相似文献
103.
《Journal of separation science》2018,41(6):1346-1354
By generating 1500 random chiral separation systems, assuming two‐site Langmuir interactions, we investigated numerically how the maximal productivity (PR,max) was affected by changes in stationary phase adsorption properties. The relative change in PR,max, when one adsorption property changed 10%, was determined for each system and for each studied parameter the corresponding productivity change distribution of the systems was analyzed. We could conclude that there is no reason to have columns with more than 500 theoretical plates and larger selectivity than 3. More specifically, we found that changes in selectivity have a major impact on PR,max if it is below ∼2 and, interestingly, increasing selectivity when it is above ∼3 decreases PR,max. Increase in relative saturation capacity will have a major impact on PR,max if it is below ∼40%, but only modest above this percent. Increasing total monolayer saturation capacity, or decreasing the first eluting enantiomer's retention factor, will have a modest effect on PR,max and increased efficiency will have almost no effect at all on PR,max unless it is below ∼500 theoretical plates. Finally, we showed that chiral columns with superior analytic performance might have inferior preparative performance, or vice versa. It is, therefore, not possible to assess columns based on their analytical performance alone. 相似文献
104.
Lu Zhaoxin
Takashi Fujimura
《Radiation Physics and Chemistry》1993,42(4-6):923-926Polymer carriers, poly(hydroxyethyl acrylate(HEA)-methoxy polyethylene glycol methylacrylate (M-23G)) and poly (hydroxyethyl accrylate(HEA)-glycidyl methlacrylate(GMA)) using for immobilization of yeast cells were prepared by radiation polymerization at low temperature. Yeast cells were immobilized through adhesion and multiplication of yeast cells themselves. The ethanol productivity of immobilized yeast cells with these carriers was related to the monomer composition of polymers and the optimum monomer composition was 20% : 10% in poly(HEA-M-23G) and 17%: 6% in poly(HEA-GMA). In this case, the ethanol productivity of immobilized yeast cells was 29mg/ml/h which was about 4 times that of cells in free system. The relationship between the activity of immobilized yeast cells and the water content of polymer carrier were also discussed. 相似文献
105.
RONALD G. FELTHOVEN CATHERINE J. MORRISON PAUL MARCELO TORRES 《Natural Resource Modeling》2009,22(1):105-136
Abstract Traditional productivity measures have been much less prevalent in fisheries economics than other measures of economic and biological performance. It has been increasingly recognized, however, that modeling and measuring fisheries' production relationships is central to understanding and ultimately correcting the repercussions of externalities and poorly designed regulations. We use a transformation function production model to estimate productivity and its components for catcher–processors in the Bering Sea and Aleutian Islands pollock fishery, before and after the introduction of a cooperative system that grants exclusive harvesting privileges and allows quota exchange. We also recognize the roles of externalities from pollock harvesting by incorporating data on climate, bycatch, and fish biomass. We find that productivity has been increasing over time, that many productive contributions and interactions of climate, bycatch, and fishing strategies are statistically significant, and that regulatory changes have had both direct and indirect impacts on catch patterns and productivity. 相似文献
106.
W. Rödder E. Reucher 《European Journal of Operational Research》2011,212(1):148-154
Data Envelopment Analysis DEA is a method for estimating (in-)efficiencies of Decision Making Units DMUs by means of weighted output - to input - ratios, being the weights optimal virtual prices of such ex-post activities for all units. The cross-efficiency matrix then evaluates these output - to input - relations with respect to all optimal price systems, and hence permits efficiency rankings for the DMUs by aggregating the matrix entries line - and/or columnwise. In this contribution the classical input oriented DEA approach is generalized twofold: its first aim is an optimal efficiency improving input allocation rather than a mere radial input reduction. The second aim is the choice of a peer-DMU, the price system of which is acceptable for the remaining units. As free input allocation permits substitutional effects and so rises productivities in view of possible peers and for all units, it supports such consensual choice. Numerical examples show the positive effects of the new concept. 相似文献
107.
用DEA估计生产力进步的探讨 总被引:1,自引:0,他引:1
有关生产力进步的概念与计算,文[1]、[2]基于规模报酬不变的生产前沿面来研究,本文推广到基于一般生产前沿面来研究.因此本文在讨论中用面向输出的C2GS2模型而不是文[1]、[2]中所用的面向输入的C2R模型. 相似文献
108.
109.
以生产核燃料为主要目的的聚变-裂变混合堆包层,可采用两种不同的设计方案:快裂变包层和抑制裂变包层。它们各具有其长处和不足。本文以两个典型的包层结构为例,作了快裂变包层和抑制裂变包层的中子学计算和对比分析。其结果可作为包层选型设计及技术可行性、安全性、经济性分析的参考。 相似文献