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   23247篇
  免费   1462篇
  国内免费   2448篇
林业   2138篇
农学   2189篇
基础科学   1537篇
  2928篇
综合类   9377篇
农作物   1654篇
水产渔业   1296篇
畜牧兽医   3519篇
园艺   1362篇
植物保护   1157篇
  2024年   113篇
  2023年   360篇
  2022年   820篇
  2021年   920篇
  2020年   882篇
  2019年   881篇
  2018年   616篇
  2017年   1050篇
  2016年   845篇
  2015年   1166篇
  2014年   1190篇
  2013年   1434篇
  2012年   1883篇
  2011年   1983篇
  2010年   1797篇
  2009年   1664篇
  2008年   1590篇
  2007年   1524篇
  2006年   1311篇
  2005年   1011篇
  2004年   686篇
  2003年   551篇
  2002年   653篇
  2001年   588篇
  2000年   474篇
  1999年   258篇
  1998年   163篇
  1997年   133篇
  1996年   79篇
  1995年   88篇
  1994年   96篇
  1993年   60篇
  1992年   60篇
  1991年   59篇
  1990年   34篇
  1989年   24篇
  1988年   31篇
  1987年   20篇
  1986年   9篇
  1985年   9篇
  1984年   6篇
  1983年   3篇
  1981年   6篇
  1980年   3篇
  1979年   5篇
  1975年   2篇
  1967年   2篇
  1966年   2篇
  1962年   2篇
  1956年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
201.
水稻条纹叶枯病自20世纪90年代末以来在江苏全省大面积发生,现已成为江苏省水稻生产上发生最为严重的病害之一。分析其暴发原因:灰飞虱虫量和带毒率高;耕作栽培制度有利于发病;水稻品种不抗病等。通过调查试验明确了:利用锐劲特等药剂进行稻种处理;适当推迟水稻播栽期;选用抗耐病品种等措施的主要防治对策。  相似文献   
202.
In vitro cultured vascular endothelial cells (VEC) and mouse 3T3 fibroblasts (3T3) on the acellular dermal matrix , which were made of porcine skins. We made the cell proliferation test with MTT assay and the histological observation after cells were seeded on the acelluar dermis for 1 week with histological section. The cell growth curves showed VEC and 3T3 grew much rapidly on the acelluar dermis.The histological observation revealed VEC had formed a monolayer, some places even had formed 2 to 3 layer. The results suggest that the acelluar porcine dermal matrix have good biocompatibility , it will be widely applied.  相似文献   
203.
204.
205.
Compared with the traditional full-bridge(FB)zero-voltage-switched(ZVS) pulsewidth-modulated(PWM) converter, the FB-ZVS-PWM converter with a saturable inductor has a wider load range with ZVS and smaller circulating energy as well as smaller duty cycle loss. By analyzing the operation principle of the converter, this paper studies design considerations of the parameter bringing about ZVS and dead time of the switch, and gives out the design method, finally simulation testing has been carried out.  相似文献   
206.
The process of actin polymerization and depolymerization have some relation with its function,the activation of such process is compatible to its functions. The polymerization progress is divided into four steps: The first step is the activation of the monomer actin. The nucleation of actin nucleus forms in the second step which limits the polymerization speed. The elongation of the F-actin filaments happens in the following step. In the last step, a steady-state is attained, the length of the filament does not change because the polymerizing rate in the barbed end is the same with the depolymerizing rate in the pointed end. Some factors which affect the polymerizing process, such as nucleotide, actin related proteins are discussed. The aim is to know more about how to assemble the complicated system with biomacromolecule and what to function.  相似文献   
207.
208.
The stimulation and the optimal design for bus ride comfort have played an importable roles in design and reform of automobile products. The new vibration comfort coefficient is applied to evaluate the ride comfort of automobile, and the software is developed. It is verified that the study has theoretical and practical value significantly.  相似文献   
209.
After the completion of the Three Gorges project,the navigation conditions of the reservoir region will be improved evidently,which has laid the foundation for straight run of the 10,000-ton-class fleet to Chongqing Port,and is the promotion of the development of shipping in Yangtze River.But according to the standard of the 10,000-ton-class fleet,there are still some reaches of the reservoir region can not meet the requirements of the waterway on smooth and safe navigation.Therefore,some regulation measures should be adopted to eliminate these obstructions.It is one of the important parts in the reservoir region waterway regulation work for the Fuling to Tongluo canyon reach blasting project.30 reef obstacle blocks of 14 reaches in this project were removed by blasting.Based on the analysis of obstruct features of various rocks,according to the standard of the 10,000-ton-class fleet,the design parameters and blasting regulation program were put forward,and the regulation effect is analyzed and forecasted.  相似文献   
210.
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