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   34167篇
  免费   697篇
  国内免费   158篇
系统科学   1182篇
丛书文集   499篇
教育与普及   42篇
理论与方法论   363篇
现状及发展   14225篇
研究方法   1285篇
综合类   17029篇
自然研究   397篇
  2018年   770篇
  2017年   804篇
  2016年   526篇
  2013年   271篇
  2012年   669篇
  2011年   1719篇
  2010年   976篇
  2009年   576篇
  2008年   1027篇
  2007年   1322篇
  2006年   578篇
  2005年   575篇
  2004年   658篇
  2003年   647篇
  2002年   556篇
  2001年   938篇
  2000年   866篇
  1999年   618篇
  1992年   595篇
  1991年   419篇
  1990年   488篇
  1989年   496篇
  1988年   466篇
  1987年   548篇
  1986年   475篇
  1985年   599篇
  1984年   485篇
  1983年   365篇
  1982年   340篇
  1981年   369篇
  1980年   462篇
  1979年   891篇
  1978年   761篇
  1977年   744篇
  1976年   612篇
  1975年   634篇
  1974年   846篇
  1973年   758篇
  1972年   779篇
  1971年   840篇
  1970年   1073篇
  1969年   813篇
  1968年   820篇
  1967年   796篇
  1966年   681篇
  1965年   472篇
  1959年   249篇
  1958年   440篇
  1957年   292篇
  1956年   259篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
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   
14.
1 Results In the coordination system by using complexation with organic ligand, the ff emission of lanthanide(Ⅲ) (Ln(Ⅲ)) is induced the excitation energy transfer form the organic chromophore under the light-irradiation. However, there are not so much number of reports to discuss the energy relaxation mechanism in such complexes with Ln(Ⅲ). Recently, we succeeded firstly to estimate the rate constant of the energy transfer between the ligand and Ln(Ⅲ) in Pr(Ⅲ)-phenanthroline analogs[1]. Here, we will di...  相似文献   
15.
16.
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   
17.
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   
18.
19.
20.
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