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   30057篇
  免费   685篇
  国内免费   57篇
系统科学   1317篇
丛书文集   493篇
教育与普及   45篇
理论与方法论   369篇
现状及发展   11684篇
研究方法   1032篇
综合类   15436篇
自然研究   423篇
  2018年   762篇
  2017年   768篇
  2016年   505篇
  2012年   619篇
  2011年   1714篇
  2010年   957篇
  2009年   552篇
  2008年   912篇
  2007年   1191篇
  2006年   484篇
  2005年   512篇
  2004年   570篇
  2003年   591篇
  2002年   423篇
  2001年   736篇
  2000年   731篇
  1999年   436篇
  1992年   430篇
  1991年   383篇
  1990年   410篇
  1989年   340篇
  1988年   382篇
  1987年   390篇
  1986年   355篇
  1985年   502篇
  1984年   383篇
  1983年   312篇
  1982年   262篇
  1981年   267篇
  1980年   365篇
  1979年   756篇
  1978年   641篇
  1977年   626篇
  1976年   485篇
  1975年   557篇
  1974年   742篇
  1973年   639篇
  1972年   671篇
  1971年   759篇
  1970年   999篇
  1969年   800篇
  1968年   674篇
  1967年   734篇
  1966年   653篇
  1965年   483篇
  1959年   270篇
  1958年   409篇
  1957年   310篇
  1956年   269篇
  1954年   269篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
22.
The method of extracting and describing the intended behavior of software precisely has become one of the key points in the fields of software behavior's dynamic and trusted authentication. In this paper, the author proposes a specified measure of extracting SIBDS (software intended behaviors describing sets) statically from the binary executable using the software's API functions invoking, and also introduces the definition of the structure used to store the SIBDS in detail. Experimental results demonstrate that the extracting method and the storage structure definition offers three strong properties: (i) it can describe the software's intended behavior accurately; (ii) it demands a small storage expense; (iii) it provides strong capability to defend against mimicry attack.  相似文献   
23.
In this experiment, using the methods of drought-stress in the pot and PEG simulative drought-stress, three native rocky-slope grasses Pogonatherum panideum(Lam.) Hack, Erioophorum comosum nees and Cynodon dactylon cultivated in the pots were selected as materials to study their drought-resistance by analyzing the indexes such as the leaf area index, the drying roots accumulation, the holding water ability of leaf, the relative conductance of leaf, the soluble protein, chlorophyll. At the same time, by comparing with membership function value of each index, the order of each grass drought-resistance was decided. The results showed that the drought-resistance of Erioophorum comosum nees was stronger than Cynodon dactylon and drought-resistance of Cynodon dactylon was stronger than Pogonatherum panideum (Lam.) Hack. The purpose of the experimental results was to find theoretical foundations for selecting and cultivating native protecting-slope vegetations to adapt to rocky slopes.  相似文献   
24.
μC/OS-Ⅱ is an open source real-time kernel adopting priority preemptive schedule strategy. Aiming at the problem of μC/OS-Ⅱ failing to support homology priority tasks scheduling, an approach for solution is proposed. The basic idea is adding round-robin scheduling strategy in its original scheduler in order to schedule homology priority tasks through time slice roundrobin. Implementation approach is given in detail. Firstly, the Task Control Block (TCB) is extended. And then, a new priority index table is created, in which each index pointer points to a set of homology priority tasks. Eventually, on the basis of reconstructing μC/OS-Ⅱ real-time kernel, task scheduling module is rewritten. Otherwise, schedulability of homology task supported by modified kernel had been analyzed, and deadline formula of created homology tasks is given. By theoretical analysis and experiment verification, the modified kernel can support homology priority tasks scheduling, meanwhile, it also remains preemptive property of original μC/OS-Ⅱ.  相似文献   
25.
Summary Intravenous or subcutaneous administration of pyribenzamine and other antihistaminics is able to decrease, and to delay the appearance of chemosis produced by mustard oils in the eye of the rabbit. Simultaneously occurring vascular reactions, on the other hand, are but slightly affected by antihistaminics. Intravenous or subcutaneous administration of rutin has no clear-cut effect on chemosis; it is however able to inhibit the vascular reaction.  相似文献   
26.
27.
28.
29.
30.
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