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   4801篇
  免费   210篇
  国内免费   503篇
林业   397篇
农学   531篇
基础科学   703篇
  908篇
综合类   2264篇
农作物   152篇
水产渔业   71篇
畜牧兽医   185篇
园艺   56篇
植物保护   247篇
  2024年   21篇
  2023年   85篇
  2022年   126篇
  2021年   140篇
  2020年   119篇
  2019年   178篇
  2018年   135篇
  2017年   171篇
  2016年   290篇
  2015年   214篇
  2014年   245篇
  2013年   275篇
  2012年   379篇
  2011年   380篇
  2010年   335篇
  2009年   289篇
  2008年   272篇
  2007年   283篇
  2006年   283篇
  2005年   238篇
  2004年   162篇
  2003年   119篇
  2002年   124篇
  2001年   83篇
  2000年   68篇
  1999年   60篇
  1998年   59篇
  1997年   52篇
  1996年   58篇
  1995年   47篇
  1994年   37篇
  1993年   36篇
  1992年   44篇
  1991年   29篇
  1990年   31篇
  1989年   23篇
  1988年   12篇
  1987年   6篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1976年   1篇
排序方式: 共有5514条查询结果,搜索用时 218 毫秒
41.
The structure and properties of fuzzy matroids are investigated further. By generalizing the idea of fuzzy subgraph and fuzzy subspace to fuzzy matroid, some smaller fuzzy matroids are derived from a fuzzy matroid M in the different ways. Moreover, the properties of these new fuzzy matroids are studied, and the relationships among them are also presented.  相似文献   
42.
This paper analyses the importance of the suppliers' evaluation in automobile industry. Based the conception of system, all the corporations' suppliers are regarded as an integer. On condition that the corporation has evaluated the single supplier's performance, the model for evaluate the performance of supplier's system is established, the performance by two-level fuzzy method is evaluated. Finally, the method sets with an example as the illustration.  相似文献   
43.
Polyaluminum silicate is a new type of inorganic macromolecular flocculants, which is developed as a complex product in recent years on the base of polyalumium flocculant and polysilicic acid flocculant. Sodium silicate is diluted to the concentration of 3.0% SiO 2 with distilled water. The solution was adjusted to pH 4.5 with sulphate acid and kept at quiescency for different time to get polysilicic acid with different polymerization degrees. Using polysilicic acid prepared and aluminium chloride as materials, a series of polyaluminium silicate chlorides(PASC) with different basicities(B), Al/Si molar ratios and polymerization degree of silicic acid are prepared by copolymerization technique. The Al-Ferron timed complex colorimetric method is applied to characterize species distribution of PASC and to study its influence factors. The interaction between hydrolyzed aluminum species and polysilicic acid with different polymerization degrees in PASC is discussed.The flocculant prepared is applied to the treatment of commercial concrete wastewater. The turbidity removal of commercial concrete wastewater is up to 97% when a PASC, prepared with polysilicic acid of 145 min polymerization degree.  相似文献   
44.
This paper analyzes the limitation of regarding the weighted average cost of capital as the optimal standard of capital structure in the traditional capital structure decision-making method, and analyzes the view that the capital structure is affected by many factors,such as earning power, long-term stability of operating, the attitudes held by owners and operators, the attitudes held by creditors and financial risk. With the example, the affecting factors of the capital structure is analyzed. The fuzzy synthetic evaluation model are employed to decision-making of the capital structure. This article also shows the key point of its application.  相似文献   
45.
46.
Complexity of mutual act and different sensation of different tourists are important factors influencing regional tourism resources evaluation. Fuzzy mathematic method can be used to up quantitative evaluation method on tourism resources evaluation. Taking Wushan Small Three Gorges as an example, the author carries out the evaluation of the tourism resources in the Three Gorges Reservoir. At the same time, the authors consider that five factors, such as improvement of the comunication of tourism resources, quickening the Steps of urbanization in reservior area, must be done well.  相似文献   
47.
According to the needs of setting up a professional system based on motorcycle design,the CBR(case based reasoning) and RBR(rule based reasoning) methods are introduced.After discussing the difference between the two kinds of reasoning,a method of integrating them into the motorcycle design flow is put forward to realize the design reusable technology and improve the design efficiency,by using the CBR in the step of selecting the similar motorcycle and the RBR in project's modification according to correlative rules.  相似文献   
48.
The authors determine the index system and the index weight of capability of real estate by applying Delphi method and AHP method, and found the fuzzy comprehensive evaluation model of capability of real estate. They creates the model of capability Vs. price based on value engineering theory. The authors analysis detailedly deciding method of capability Vs. price of real estate combined with a practice example and application. The method adapts to a house as well as the type of the house. The method resolves the problem which capability Vs. price of real estate was only described by qualitatively for ages, which supplies theory basis to developer and consumer.  相似文献   
49.
At present, in the evaluation process of the real estate value the material form is mainly concentrated on, while the value brought by the real estate brand are usually neglected. In this paper, considering the particularity of the real estate brand evaluation, the method of network analysis is adopted. In the evaluation process, the evaluation method of excess income law are developed by leading the thoughts and methods of the fuzzy set theory, and a systematic assess model is found. Then, an example is given as illustration. At last, the appraise about the application of the model is made.  相似文献   
50.
With the rapid development of the manufacture, the technology of information and net, the traditional management of enterprise cannot meet the demands of the market, to get a better development and benefit, enterprises have to keep a competitive and cooperative relation with each other. Thus is the beginning of the dynamic union. Combining the theory of dynamic union with BPR, this thesis proposes the BPR facing the dynamic union and expounds the principle of it, the re-engineering of the full life cycle and the evaluation method of re-engineering on the base of analyzing the characteristic of dynamic and demands of process.  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