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   37539篇
  免费   701篇
  国内免费   77篇
系统科学   1217篇
丛书文集   717篇
教育与普及   82篇
理论与方法论   467篇
现状及发展   14645篇
研究方法   1431篇
综合类   19351篇
自然研究   407篇
  2018年   756篇
  2017年   773篇
  2016年   521篇
  2012年   719篇
  2011年   1851篇
  2010年   1013篇
  2009年   590篇
  2008年   1093篇
  2007年   1493篇
  2006年   641篇
  2005年   683篇
  2004年   688篇
  2003年   811篇
  2002年   699篇
  2001年   987篇
  2000年   904篇
  1999年   602篇
  1992年   580篇
  1991年   468篇
  1990年   487篇
  1989年   489篇
  1988年   494篇
  1987年   500篇
  1986年   496篇
  1985年   617篇
  1984年   506篇
  1983年   406篇
  1982年   348篇
  1981年   345篇
  1980年   453篇
  1979年   974篇
  1978年   863篇
  1977年   851篇
  1976年   583篇
  1975年   632篇
  1974年   937篇
  1973年   788篇
  1972年   807篇
  1971年   1019篇
  1970年   1344篇
  1969年   1008篇
  1968年   948篇
  1967年   991篇
  1966年   833篇
  1965年   613篇
  1959年   360篇
  1958年   522篇
  1957年   444篇
  1956年   366篇
  1954年   363篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
Duhem’s concept of ‘good sense’ is central to his philosophy of science, given that it is what allows scientists to decide between competing theories. Scientists must use good sense and have intellectual and moral virtues in order to be neutral arbiters of scientific theories, especially when choosing between empirically adequate theories. I discuss the parallels in Duhem’s views to those of virtue epistemologists, who understand justified belief as that arrived at by a cognitive agent with intellectual and moral virtues, showing how consideration of Duhem as a virtue epistemologist offers insights into his views, as well as providing possible answers to some puzzles about virtue epistemology. The extent to which Duhem holds that the intellectual and moral virtues of the scientist determine scientific knowledge has not been generally noticed.  相似文献   
24.
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   
25.
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   
26.
27.
28.
  相似文献   
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