首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7978篇
  免费   496篇
  国内免费   736篇
林业   656篇
农学   548篇
基础科学   332篇
  853篇
综合类   4037篇
农作物   611篇
水产渔业   391篇
畜牧兽医   1000篇
园艺   430篇
植物保护   352篇
  2024年   38篇
  2023年   152篇
  2022年   301篇
  2021年   334篇
  2020年   328篇
  2019年   277篇
  2018年   229篇
  2017年   393篇
  2016年   226篇
  2015年   340篇
  2014年   387篇
  2013年   477篇
  2012年   606篇
  2011年   637篇
  2010年   621篇
  2009年   505篇
  2008年   555篇
  2007年   499篇
  2006年   441篇
  2005年   378篇
  2004年   200篇
  2003年   186篇
  2002年   223篇
  2001年   214篇
  2000年   172篇
  1999年   87篇
  1998年   48篇
  1997年   38篇
  1996年   39篇
  1995年   50篇
  1994年   36篇
  1993年   31篇
  1992年   45篇
  1991年   19篇
  1990年   32篇
  1989年   16篇
  1988年   21篇
  1987年   7篇
  1986年   8篇
  1985年   3篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1963年   1篇
  1956年   5篇
排序方式: 共有9210条查询结果,搜索用时 734 毫秒
91.
Employing the standpoint of irrational investors in the behavior finance, the authors study the relation on the irrational behavior of medium and small Investors and underpricing of IPO in our country. The paper premises that a revenue-maximizing issuer will be regarded as the target function, and the rational institutional investors can be delegated the task of holding the stocks in the after-market for resale to the irrational medium and small investors--thereby extracting surplus from them, finally the issuer can maximize their expected revenue. We model the process mentioned above and find that the high underpricing of IPO in our country has the direct relation with numerous the irrational medium and small investors existing in our country who cause the underpricing.  相似文献   
92.
The following details are discussed in the present paper, after high titanium slag and H3PO4 is put in the closed system,the .reaction takes place under controlled temperature conditions, and the gas produced is collected. The two phases of gas liquid attain kinetic equilibrium, ihe gas above the liquid is used to make GC analysis with the aid of chromatographic column of 5A molecular sieve, TCD and N2 30ml/min. Satisfactory quantitative results can be achieved with simple instruments and uncomplicated operation technique.  相似文献   
93.
94.
The relationship of investors and venture capitalists is an important part in venture capital. Based on asymmetric information, this paper analyzes the principal agent relationship between investors and venture capitalists with game theory. And this paper mainly discusses the choosing, controlling and incentive problem. It suggests that only the capable and self confident venture capitalists could accept the terms of the limited partnership. It also indicates that recompense mechanism which holds the interest of investors and that of venture capitalists tightly is the center of the limited partnership. Rate of yield is the key of recompense mechanism, it not only reflects the incentive on venture capitalists, also reflects the share of risk between investors and venture capitalists. At last, the market credit play an important role in venture capital.  相似文献   
95.
Data warehouse is not the simply data accumulation of operational database. For exerting the function of data warehouse, the construction of data warehouse should be convenient for the data mining and business intelligent work, supply information access, analyze, and share for decision maker. The key to constructing a successful data warehouse is to fully understand the demand of end users from beginning to the end, search and storage data surround users motive closely. This paper first analyzes the data warehouse characteristic and the sort of data component, emphasizes in effective data loading methods and strategies from operational database to data warehouse, gives five sorts data loading methods.  相似文献   
96.
The research theme of this paper is about how third-party logistics provider design a kind of effective incentive mechanism which can not only avoid the moral hazard behavior of the subcontractor , but also promote subcontractor to raise the serving performance constantly, until obtaining the best TPL performance .Through building bilevel programming model where constructing the Nash equilibrium model this paper, the anthors assume subcontract decision variable as endogenetic variable first, and then analyze the optimal solution with the restraint of Nash equilibrium at the time of decision variable as exogenous variable, push the subcontract relationship research at the principal-agent level into the lay that principal-agent combining with whole contract performance optimal decision.  相似文献   
97.
The implement of enterprise knowledge management gives rise to extensive research on its measurement. Based on the existing measurement theories and evaluation index systems of enterprise knowledge management during the past three years in China, this paper analyzes the problems in measuring target and designing the evaluation index system in the existing research findings, and explains detailedly why measurement target of enterprise knowledge management should be "level evaluation" instead of "performance evaluation", and definitely points out the meanings of enterprise knowledge management level and significance of its evaluation. This paper also indicates that the design of the evaluation index system should be complete, reasonable, proper and operable.  相似文献   
98.
The standard Linux is a typical time-sharing system, it has a poor real-time performance. But according to the applications of the Linux OS are expanding on real-time domain, it becomes necessary to enhance the performance of the Linux system. This paper analyses the schedule policies and schedule algorithms of the Linux kernel, and discusses several different kinds of methods about enhancing real-time performance of the Linux system from the total Linux system. They authors summarizes the current research's developments of the Linux system.  相似文献   
99.
In this paper, based on the discussion of orthogonal decomposition method for the buckling mode of unsymmetrical structure, taking the variable-section beam-column as an example, a simple and direct method of the second order analysis is presented. In the new method, the conception of enlargement coefficient brought forward by Timoshenko is developed. To begin with the curvature of the variable-section beam-column, the linear equations are set up. With their solution, a group of orthogonal buckling mode can be obtained. The primary deflection can be decomposed to a group of homomorphic deflection similar to buckling mode. Then, the group of deflection is multiplied by corresponding enlargement coefficient and plus the result, finally, the second-order total deflection can be obtained.  相似文献   
100.
The term Cleaner Production(CP)and Estimation of Cleaner Production Potential are introduced, meanwhile their importance are pointed out. Three kinds of cleaner technologies are put forward-Best Available Technology(BAT), Best Economic Attractive Technology(BEAT), and usually used new technology, combined with some CP casesat home and abroad. several cleaner technologies are compared, and the results show that the implementation of CP can greatly reduce consumption of resource and energy and pollution emission, There are obvious environmental, economic and social benefits. The great potential of CP in industrial pollution control are estimated and demonstrated ultimately.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号