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   83274篇
  免费   4383篇
  国内免费   6343篇
林业   9349篇
农学   7063篇
基础科学   4308篇
  10909篇
综合类   41109篇
农作物   4015篇
水产渔业   2506篇
畜牧兽医   8117篇
园艺   2524篇
植物保护   4100篇
  2024年   403篇
  2023年   1101篇
  2022年   1781篇
  2021年   1915篇
  2020年   1967篇
  2019年   2538篇
  2018年   1423篇
  2017年   2545篇
  2016年   3149篇
  2015年   2829篇
  2014年   3977篇
  2013年   4123篇
  2012年   5996篇
  2011年   6354篇
  2010年   5216篇
  2009年   5138篇
  2008年   4799篇
  2007年   5751篇
  2006年   5076篇
  2005年   4265篇
  2004年   3220篇
  2003年   2836篇
  2002年   2164篇
  2001年   1939篇
  2000年   1798篇
  1999年   1456篇
  1998年   1250篇
  1997年   1133篇
  1996年   1091篇
  1995年   1047篇
  1994年   1025篇
  1993年   891篇
  1992年   826篇
  1991年   684篇
  1990年   612篇
  1989年   560篇
  1988年   424篇
  1987年   294篇
  1986年   143篇
  1985年   54篇
  1984年   28篇
  1983年   25篇
  1982年   24篇
  1981年   21篇
  1980年   27篇
  1979年   19篇
  1978年   17篇
  1976年   10篇
  1962年   9篇
  1955年   8篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
811.
812.
In order to overcome some technical difficulties,we adopt ingenously the grey models combined with the quantitative analog method,and select the Dan Jiangkou Project which has accumulated practical operation data for a long time as the analog project to predict the economic influence for the circumjacent reservoir region of the Longtan hydropower project.On the basis of analog we have built various industrial economic grey models,and compare them with the corresponding predictions for the unconstructed reservoir case.The predictions of the former are greatly larger than the later ones.and hence provides a certain scientific basis for the central leaders to make a decision for constructing the huge hydropower project ultimateiy.  相似文献   
813.
814.
This paper presents the application of sand-gravel-cushion technique in thefoundation of mountainous area inhomogeneity and analyges non-uniformity of the foundation inmountainous,It is different from the traditional theory of sand-cushion,This is a new developmentand able to make a full use of the rock debris fill and the combinational soil-rock foundation in the mountainous areas.  相似文献   
815.
816.
817.
818.
Flowing dynamic characteristics and its temperature dynamic characteristics of a three-level sewage pipe network in Chongqing were analyzed. A mall's building whole year load was simulated. In the adverse condition of wastewater flow, the market construction peak discharge heat was compared with the sewage heat load, the balance between the most adverse flow and the building demand was found. Explored supply and demand matching method between urban sewage and city building load in flow adverse condition to take full advantage of the urban sewage cold and hot resources. the composite system was adeptcd to make up the most unfavorable flow time of sewage average heat load and the construction load difference; it also puts forward principle of load sharing and control strategy aimed at compound system.  相似文献   
819.
By review of region study in recent development of history science, geography and Sciences of Human Settlements, this paper points out that material collecting without interrelated analyzing as well as focusing on main question and assumption without enough argumentation are main problems in this field now. The method renovation & combination with related subjects are discussed, this paper concludes that strengthen interdisciplinary study with Geography is a key issue in the future development of region study in Sciences of Human Settlements and possible approach to "technical development' and "humanity concern'.  相似文献   
820.
The modernization has been the dream that Chinese nation has wished eagerly to realize all the time. In some sense, the modernization of China means urbanization. The reform and opening - up over the past 20 years , built and made the enormous achievement in urbanization of China, have changed the appearance of the city of China greatly. But to numerous traditional historical zones, what kind of urbanization way should on earth be taken, it has been the question long - term in dispute of the planning circles all the time. In this paper, Ciqikou community of Chongqing as an example, doing some discussions from sociology on this question, the author hopes, that for such difficult problem, by this settlement a piece of breach can be found as soon as possible.  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