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   36052篇
  免费   106篇
  国内免费   131篇
系统科学   307篇
丛书文集   600篇
教育与普及   87篇
理论与方法论   98篇
现状及发展   15469篇
研究方法   1409篇
综合类   17734篇
自然研究   585篇
  2013年   228篇
  2012年   476篇
  2011年   1062篇
  2010年   194篇
  2008年   589篇
  2007年   690篇
  2006年   697篇
  2005年   679篇
  2004年   656篇
  2003年   672篇
  2002年   572篇
  2001年   1144篇
  2000年   1128篇
  1999年   668篇
  1994年   366篇
  1992年   688篇
  1991年   533篇
  1990年   618篇
  1989年   538篇
  1988年   550篇
  1987年   589篇
  1986年   561篇
  1985年   754篇
  1984年   562篇
  1983年   504篇
  1982年   429篇
  1981年   441篇
  1980年   510篇
  1979年   1152篇
  1978年   933篇
  1977年   875篇
  1976年   732篇
  1975年   807篇
  1974年   994篇
  1973年   882篇
  1972年   877篇
  1971年   1045篇
  1970年   1394篇
  1969年   1053篇
  1968年   990篇
  1967年   980篇
  1966年   909篇
  1965年   663篇
  1959年   384篇
  1958年   609篇
  1957年   431篇
  1956年   393篇
  1955年   359篇
  1954年   379篇
  1948年   282篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
121.
This paper is concerned with the development of ‘Systems Thinking.’ In particular, it considers and critiques ‘traditional Systems Thinking’ within the framework of Critical Systems Thinking. Before embarking on such a venture it is necessary to derive a base context from which to develop argument and analysis. Therefore the outline of this paper is as follows: A contextual setting for Systems Thinking, Theoretical Considerations, Soft Systems Thinking and Methodology, and A Critical Systems Thinking (CST) approach. The account of the development of Systems Thinking is followed by a synopsis of a theoretical framework for Systems Thinking which will allow us to gain an understanding of contemporary views. The paper then goes on to review SSM and CST in order to provide a platform for a critique of traditional forms of Systems Thinking. The final section briefly discusses the applicability of CST to the ‘real-world’ context by outlining some current studies being undertaken by the author.  相似文献   
122.
The effects of alcohol consumption, cigarette smoking and age on sister chromatid exchange (SCE) frequency in human lymphocytes were assessed by means of multiple linear regression. An increase in SCE rates was associated with alcohol consumption (p = 0.0001), smoking (p = 0.0231), and, to a small extent (p = 0.057), age. These three confounding factors explain 48% of the inter-personal variation in SCE rates among subjects studied.  相似文献   
123.
After a brief recall of the Sidelobe Canceler (SLC) working principle, including the derivation of a general formula for the Cancellation Ratio (CR), the effects of channel mismatching are investigated. In particular, curves providing CRvalues as a function of amplitude and phase channel mismatching, radar bandwidth, and jammer direction of arrival (JDOA) are provided for the cases of one and two auxiliary antennas. Subsequently, a time -space processor for performance restoration is analyzed in detail. In addition to the above mentioned quantities, the attainable CR value is expressed as a function of the space-time processor parameters. The contribution of the paper is related to the derivation of a number of mathematical equations of CR for several cases of practical interest for the radar engineer. In addition, several curves are presented to assist design of SLC systems.  相似文献   
124.
以B2O3粉扩NH3为原料,用脉冲等离子体反应器合成BN,所得产品经X射线衍射,红外光谱分析表明,产品中除含六方氮化硼外,还含有少量立方氮化硼,生产工艺简单。  相似文献   
125.
126.
127.
M McClelland  A S Bhagwat 《Nature》1992,355(6361):595-596
  相似文献   
128.
Karyotypes of seven species of bats from Thailand (Chiroptera,Mammalia)   总被引:2,自引:0,他引:2  
Summary Karyotypes ofMyotis siligorensis, Myotis mystacinus, Pipistrellus pulveratus, Tylonycteris robustula, Miniopterus schreibersi fuliginosus, Hipposideros fulvus andAselliscus stoliczkanus from Thailand are investigated.Acknowledgment. The authors are very grateful to Dr N. Ratanawarabhan, Mrs S. Sittilert, P. Noonpakdee and S. Kuanchalern of Thailand Institute of Scientific and Technological Research for their valuable advice and assistance during our field survey in Thailand.  相似文献   
129.
On going trend of miniaturization in electronic rel at ed parts, which is an average of two times in every 5~7 years introduce grindin g challenges. In grinding process, the surface waviness control of thin parts is an ardent task due to its warpage, induced by the high specific grinding energy (2~10 J/mm 3). Therefore, coolant is often used to avoid thermal damage, obtai n better surface integrity and to prolong wheel life. However coolant, the incomp ressibility media introduce high forces at the gri...  相似文献   
130.
With a unique corporate culture based on ancient Ch in ese wisdom being implemented at workplace for more than 10 years, we have been e ncountering various issue of managing conflicts, in particular at organization r estructure period, although we perceive that conflict does not necessarily have dysfunctional effect on our group performance. However, conflicts between and am ong various levels of the organization hierarchy are inevitably creating certain impact on our organization cohesiveness, performa...  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