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   80037篇
  免费   7603篇
  国内免费   4220篇
电工技术   5241篇
技术理论   4篇
综合类   5598篇
化学工业   12682篇
金属工艺   4303篇
机械仪表   4487篇
建筑科学   5709篇
矿业工程   1956篇
能源动力   2225篇
轻工业   8683篇
水利工程   1725篇
石油天然气   2915篇
武器工业   779篇
无线电   8304篇
一般工业技术   9272篇
冶金工业   4740篇
原子能技术   844篇
自动化技术   12393篇
  2024年   357篇
  2023年   1222篇
  2022年   2567篇
  2021年   3384篇
  2020年   2546篇
  2019年   2050篇
  2018年   2429篇
  2017年   2634篇
  2016年   2536篇
  2015年   3448篇
  2014年   4224篇
  2013年   5370篇
  2012年   6108篇
  2011年   6666篇
  2010年   5797篇
  2009年   5483篇
  2008年   5625篇
  2007年   5191篇
  2006年   4480篇
  2005年   3626篇
  2004年   2629篇
  2003年   2245篇
  2002年   2125篇
  2001年   1731篇
  2000年   1255篇
  1999年   967篇
  1998年   696篇
  1997年   592篇
  1996年   484篇
  1995年   444篇
  1994年   338篇
  1993年   293篇
  1992年   213篇
  1991年   174篇
  1990年   201篇
  1989年   159篇
  1988年   107篇
  1987年   115篇
  1986年   127篇
  1985年   110篇
  1984年   99篇
  1983年   83篇
  1982年   103篇
  1981年   106篇
  1980年   97篇
  1979年   78篇
  1978年   65篇
  1977年   78篇
  1976年   68篇
  1975年   47篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
刘家山排土场为民采排弃形成,已经出现大规模滑坡。为了保证上下游生产生活设施的安全,依据现场实际情况,结合现场调查,提出了削坡处理的方案。经过治理后,刘家山排土场平稳地渡过了雨季,目前处于稳定状态,达到了治理目的。  相似文献   
62.
The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves.  相似文献   
63.
The ability of bacterial species to colonize and infect host organisms is critically dependent upon their capacity to adhere to cellular surfaces of the host. Adherence to cell surfaces is known to be essential for the activation and delivery of certain virulence factors, but can also directly affect host cell signaling to aid bacterial spread and survival. In this review we will discuss the recent advances in the field of bacterial adhesion, how we are beginning to unravel the effects adhesins have on host cell signaling, and how these changes aid the bacteria in terms of their survival and evasion of immune responses. Finally, we will highlight how the exploitation of bacterial adhesins may provide new therapeutic avenues for the treatment of a wide range of bacterial infections.  相似文献   
64.
Role stress has received a lot of research attention in psychological, sociological, and organizational studies over the last several decades. Based on a literature review of about 300 journal articles, this article examines prominent consequences of role stress. Specific focus is on researching differences in relationships between facets of role stress (i.e., role ambiguity, role conflict, and role overload) and frequently cited consequences using techniques of meta-analysis. Findings indicate that each role stress facet has a different relationship with the eight consequences studied. Role stress research can benefit from looking at each facet individually in addition to role stress generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
The applicability of the identical elements (IE) model of arithmetic fact retrieval (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994) to cued recall from episodic (image and sentence) memory was explored in 3 transfer experiments. In agreement with results from arithmetic, speedup following even minimal practice recalling a missing word from an episodically bound word triplet did not transfer positively to other cued recall items involving the same triplet. The shape of the learning curve further supported a shift from episode-based to IE-based recall, extending some models of skill learning to cued recall practice. In contrast with previous findings, these results indicate that a form of representation that is independent of the original episodic memory underlies cued-recall performance following minimal practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
66.
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry  相似文献   
67.
We perform a systematic measurement of the degree-of-polarization (DOP) and eye-closure penalty for optical signals with orthogonal polarizations. We find that the symmetry of DOP is maintained for the orthogonal polarizations under both first and higher order polarization-mode dispersion (PMD), whereas the symmetry of eye-closure penalty is broken under second-order PMD. An orthogonal polarization pair can have large disparity of eye-closure penalty despite an identical DOP. We also demonstrate a novel approach to estimate the maximum eye-closure penalty asymmetry with three orthogonal polarizations on the Poincare/spl acute/ sphere.  相似文献   
68.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
69.
介绍如何利用AutoCAD开发适合电气专业使用的CAD系统,通过编制电气CAD的功能菜单,构造电气元件库,增强CAD的专业性能。编制电气CAD可以有效地统一本单位电气制图标准,方便电气工程师使用CAD进行专业设计。  相似文献   
70.
吴辉 《现代显示》2006,(5):46-48
介绍液晶显示器EDM12864B的原理及其在单片机控制下的简单应用。  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