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   16176篇
  免费   733篇
  国内免费   1058篇
林业   2206篇
农学   1175篇
基础科学   1802篇
  1745篇
综合类   7032篇
农作物   796篇
水产渔业   292篇
畜牧兽医   1896篇
园艺   448篇
植物保护   575篇
  2024年   79篇
  2023年   262篇
  2022年   416篇
  2021年   480篇
  2020年   518篇
  2019年   605篇
  2018年   297篇
  2017年   504篇
  2016年   661篇
  2015年   650篇
  2014年   985篇
  2013年   933篇
  2012年   1293篇
  2011年   1303篇
  2010年   950篇
  2009年   914篇
  2008年   899篇
  2007年   1220篇
  2006年   869篇
  2005年   687篇
  2004年   652篇
  2003年   523篇
  2002年   312篇
  2001年   309篇
  2000年   281篇
  1999年   198篇
  1998年   166篇
  1997年   149篇
  1996年   142篇
  1995年   119篇
  1994年   109篇
  1993年   88篇
  1992年   91篇
  1991年   70篇
  1990年   70篇
  1989年   58篇
  1988年   41篇
  1987年   24篇
  1986年   16篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   2篇
  1978年   3篇
  1977年   1篇
  1973年   1篇
  1963年   1篇
  1962年   1篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
161.
黑龙江省水稻单产增长潜力预测方法研究   总被引:1,自引:0,他引:1  
水稻是黑龙江省的主要粮食作物。加入WTO后,水稻生产、贸易、进出口等方面都面临新的形势,同时水稻产量的稳定和增长对于国家粮食安全、人民生活水平提高以及农民奔小康都有着重要意义。因此,探讨了应用Peal曲线函数模型对黑龙江省水稻单产进行预测的方法。  相似文献   
162.
孙政才 《华北农学报》1995,10(3):103-108
在人工气候室中,对盆栽条件下不同熟期的紧凑型与平展型玉米比较研究表明,单株玉米对土壤养分的反应株型间无规律性差异;不同熟期玉米间存在明显的规律性差异。植株苗期生长速率及高低土壤肥力下的差异与叶片N、K含量,光俣速率及不同光强,不同CO2浓度与的反应差异间存在明显的相关性。不同品种间苗期光合速率差异明显,土壤肥力高低对玉米苗期光合速率影响很大。  相似文献   
163.
The engineering design of sewage treatment plant for the Chongqing city, P. R. China is analyzed in this paper. Considering the situation of China and other projects, the characteristics of falling water reactor for the environment protection project and economy of investment is introduced ; the application and foreground of falling water aeration in the process of sewage treatment is discussed, such as Oxidation - ditch, SBR, and so on. The conclusion indicated that the falling water aeration can be designed and used as an independent aeration, and, it is an upgraded technology of sewage treatment which is adaptive for city water environment control in middle and small towns in China. The falling water aeration may reduce running cost of the sewage treatment plant, is adaptive for foothill and the mountainous areas, and reduces project investment and environments damage.  相似文献   
164.
Su Su 《保鲜与加工》1993,(4):125-129
This paper points out the shortcoming of the existing project break-even analysis method. A new improved method-the dynamic project break-even analysis method has been put forward.  相似文献   
165.
Investment on construction projects has become an important factor in improving the development of economy in China.The non-price bottom bidding is a representation that the investment on projects is becoming standardized.During the years of trying out the non-price bottom bidding,the colluding in bidding or bidding below the cost has happened several times,which have damaged the benefits of owners.To solve theses problems,this paper firstly studies the reason of these problems-the failure in the normal relationship between principal and agent.Then,some measures have been presented as follows: building systematic and scientific system of qualification prejudication,judging behaviors of colluding in bidding and bidding below the cost with reason and providing a surety mechanism of the project.The authors hope that these measures are beneficial to non-price bottom bidding.  相似文献   
166.
Earning report is a main accounting report that transmits earning information to users. It is the core of financial reports system. Earning information is significant to users' decision making. This paper studies the respond of stock trading volume to earning report and draws the curve of trading volume before and after earning report. This paper further does a regression analysis of accidental earning and abnormal return rate, and draws the relation curve of them on the earning report date to prove stock trading volume does have remarkable respond to earning report. This research is significant to either lessen small investors blindness investment and help them make reasonable forecast to markets and regulate the disclosure of listed companies.  相似文献   
167.
168.
In this paper, the historical reasons of formation of the village inside the city are analyzed. It is indicated that such situation for the villages inside the city are the result of joint action of both the villagers and the government. The foundation of villages inside the city laid on the simple compensation for farmers in confiscating the rural land and lack of intelligence aids. In this paper, the ideas and measures for their reconstruction are put forward based on consideration of the reasons of their formation and difficulties in the reconstruction.  相似文献   
169.
Housing industry is a prop industry with great potential, but it is restricted by shortage of funds. So it is necessary to probe the financing system of housing industrialization in China. This paper puts forward a financing plan for the international cooperative project in industrialized housing in Chongqing. Furthermore, it investigates the concrete financing system of the whole housing industry.  相似文献   
170.
The society-economy-environment appraisal for construction project can help our government to control macro-economy, make correlation policy and formulate laws and draw up city plan.It has great influence on the sustainable development of our society and it is the demand of the law for the environment evaluation in China.This paper introduced the basic structure of society-economy-environment appraisal system for construction project and the thought of elements transaction.Using the method of AHP, the model of project analyzing and optimizing selection is designed.For the more, the methods of the optimizing models on the selected schemes are put forward.Finally, the integrative analysis has been made on the system design and appliance of this appraisal system.  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