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   61658篇
  免费   3618篇
  国内免费   71篇
电工技术   446篇
综合类   43篇
化学工业   13227篇
金属工艺   1125篇
机械仪表   1301篇
建筑科学   1899篇
矿业工程   128篇
能源动力   1582篇
轻工业   10829篇
水利工程   609篇
石油天然气   263篇
武器工业   8篇
无线电   2456篇
一般工业技术   9771篇
冶金工业   12788篇
原子能技术   316篇
自动化技术   8556篇
  2024年   95篇
  2023年   499篇
  2022年   858篇
  2021年   1670篇
  2020年   1267篇
  2019年   1444篇
  2018年   2225篇
  2017年   2230篇
  2016年   2385篇
  2015年   1804篇
  2014年   2258篇
  2013年   4702篇
  2012年   3574篇
  2011年   3693篇
  2010年   2937篇
  2009年   2725篇
  2008年   2622篇
  2007年   2319篇
  2006年   1726篇
  2005年   1508篇
  2004年   1360篇
  2003年   1259篇
  2002年   1162篇
  2001年   834篇
  2000年   807篇
  1999年   870篇
  1998年   4072篇
  1997年   2708篇
  1996年   1805篇
  1995年   1030篇
  1994年   838篇
  1993年   891篇
  1992年   327篇
  1991年   326篇
  1990年   239篇
  1989年   268篇
  1988年   268篇
  1987年   244篇
  1986年   204篇
  1985年   256篇
  1984年   205篇
  1983年   151篇
  1982年   184篇
  1981年   208篇
  1980年   225篇
  1979年   111篇
  1978年   112篇
  1977年   404篇
  1976年   836篇
  1973年   103篇
排序方式: 共有10000条查询结果,搜索用时 270 毫秒
91.
92.
An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.  相似文献   
93.
94.
Abstract

Relative populations of four energy-lowest IPR (isolated-pentagon-rule) isomers of Eu@C86 are computed using the Gibbs energy based on characteristics from density functional theory calculations (M06-2X/3-21G?~?SDD entropy term, M06-2X/6-31G*~SDD or B2PLYP(D)/6-31G*~SDD energetics). The calculations confirm that the recently isolated Eu@C1(7)-C86 species is a major isomer in a relevant temperature region. Relationship to the empty C86 cages is discussed, too.  相似文献   
95.
96.
97.

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   
98.
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   
99.
100.
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules.  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