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   62705篇
  免费   3487篇
  国内免费   88篇
电工技术   496篇
综合类   82篇
化学工业   13493篇
金属工艺   1229篇
机械仪表   1261篇
建筑科学   2125篇
矿业工程   142篇
能源动力   1782篇
轻工业   9392篇
水利工程   555篇
石油天然气   265篇
武器工业   7篇
无线电   2915篇
一般工业技术   10283篇
冶金工业   12461篇
原子能技术   384篇
自动化技术   9408篇
  2023年   489篇
  2022年   940篇
  2021年   1809篇
  2020年   1262篇
  2019年   1446篇
  2018年   2075篇
  2017年   2033篇
  2016年   2209篇
  2015年   1779篇
  2014年   2271篇
  2013年   4427篇
  2012年   3598篇
  2011年   4004篇
  2010年   3039篇
  2009年   2888篇
  2008年   2740篇
  2007年   2518篇
  2006年   1931篇
  2005年   1699篇
  2004年   1471篇
  2003年   1362篇
  2002年   1262篇
  2001年   872篇
  2000年   844篇
  1999年   914篇
  1998年   3395篇
  1997年   2342篇
  1996年   1611篇
  1995年   1013篇
  1994年   838篇
  1993年   910篇
  1992年   398篇
  1991年   358篇
  1990年   326篇
  1989年   341篇
  1988年   300篇
  1987年   293篇
  1986年   265篇
  1985年   315篇
  1984年   256篇
  1983年   207篇
  1982年   258篇
  1981年   267篇
  1980年   261篇
  1979年   167篇
  1978年   159篇
  1977年   423篇
  1976年   804篇
  1975年   118篇
  1973年   117篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of...  相似文献   
102.
103.
104.
105.
106.
Due to the systematic increase in the production of nanomaterials (NMs) and their applications in many areas of life, issues associated with their toxicity are inevitable. In particular, the performance of heterogeneous NMs, such as nanocomposites (NCs), is unpredictable as they may inherit the properties of their individual components. Therefore, the purpose of this work was to assess the biological activity of newly synthesized Cu/TiO2-NC and the parent nanoparticle substrates Cu-NPs and TiO2-NPs on the bacterial viability, antioxidant potential and fatty acid composition of the reference Escherichia coli and Bacillus subtilis strains. Based on the toxicological parameters, it was found that B. subtilis was more sensitive to NMs than E. coli. Furthermore, Cu/TiO2-NC and Cu-NPs had an opposite effect on both strains, while TiO2-NPs had a comparable mode of action. Simultaneously, the tested strains exhibited varied responses of the antioxidant enzymes after exposure to the NMs, with Cu-NPs having the strongest impact on their activity. The most considerable alternations in the fatty acid profiles were found after the bacteria were exposed to Cu/TiO2-NC and Cu-NPs. Microscopic images indicated distinct interactions of the NMs with the bacterial outer layers, especially in regard to B. subtilis. Cu/TiO2-NC generally proved to have less distinctive antimicrobial properties on B. subtilis than E. coli compared to its parent components. Presumably, the biocidal effects of the tested NMs can be attributed to the induction of oxidative stress, the release of metal ions and specific electrochemical interactions with the bacterial cells.  相似文献   
107.
108.
109.

This paper presents a PVS development of relevant results of the theory of rings. The PVS theory includes complete proofs of the three classical isomorphism theorems for rings, and characterizations of principal, prime and maximal ideals. Algebraic concepts and properties are specified and formalized as generally as possible allowing in this manner their application to other algebraic structures. The development provides the required elements to formalize important algebraic theorems. In particular, the paper presents the formalization of the general algebraic-theoretical version of the Chinese remainder theorem (CRT) for the theory of rings, as given in abstract algebra textbooks, proved as a consequence of the first isomorphism theorem. Also, the PVS theory includes a formalization of the number-theoretical version of CRT for the structure of integers, which is the version of CRT found in formalizations. CRT for integers is obtained as a consequence of the general version of CRT for the theory of rings.

  相似文献   
110.
In this study, we have proposed an automated classification approach to identify meaningful patterns in wind field data. Utilizing an extensive simulated wind database, we have demonstrated that the proposed approach can identify low‐level jets, near‐uniform profiles, and other patterns in a reliable manner. We have studied the dependence of these wind profile patterns on locations (eg, offshore vs onshore), seasons, and diurnal cycles. Furthermore, we have found that the probability distributions of some of the patterns depend on the underlying planetary boundary layer schemes in a significant way. The future potential of the proposed approach in wind resource assessment and, more generally, in mesoscale model parameterization improvement is touched upon in this paper.  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