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   2960篇
  免费   116篇
  国内免费   3篇
电工技术   62篇
综合类   8篇
化学工业   680篇
金属工艺   49篇
机械仪表   30篇
建筑科学   181篇
矿业工程   6篇
能源动力   74篇
轻工业   267篇
水利工程   30篇
石油天然气   5篇
无线电   324篇
一般工业技术   543篇
冶金工业   343篇
原子能技术   25篇
自动化技术   452篇
  2023年   43篇
  2022年   50篇
  2021年   108篇
  2020年   56篇
  2019年   60篇
  2018年   59篇
  2017年   59篇
  2016年   87篇
  2015年   73篇
  2014年   131篇
  2013年   145篇
  2012年   168篇
  2011年   203篇
  2010年   121篇
  2009年   133篇
  2008年   143篇
  2007年   133篇
  2006年   128篇
  2005年   117篇
  2004年   89篇
  2003年   60篇
  2002年   68篇
  2001年   39篇
  2000年   53篇
  1999年   45篇
  1998年   89篇
  1997年   64篇
  1996年   72篇
  1995年   48篇
  1994年   46篇
  1993年   31篇
  1992年   20篇
  1991年   24篇
  1990年   18篇
  1989年   19篇
  1988年   11篇
  1987年   13篇
  1986年   12篇
  1985年   16篇
  1984年   18篇
  1983年   18篇
  1982年   12篇
  1981年   23篇
  1980年   14篇
  1979年   11篇
  1978年   16篇
  1977年   12篇
  1976年   23篇
  1975年   9篇
  1972年   11篇
排序方式: 共有3079条查询结果,搜索用时 15 毫秒
1.
Mammalian homologues of the Drosophila trp gene have been invoked as the structural basis for the currents associated with capacitative Ca2+ entry (CCE) in many cell types. Trp homologues are members of a large protein family that may associate as channel subunits providing an explanation for the functional diversity of store-operated channels observed in these cells. However, there is little information as to which of these genes are co-expressed at the cellular level. We have examined the tissue specific expression of five mammalian trp genes and determined which are co-expressed in five different cell lines. The results show tissue- and cell-specific co-expression of multiple trp forms. This implies that the subunit composition of a particular CCE channel may vary depending on the cell type.  相似文献   
2.
3.
4.
The authors reply to the comments by Koppelaar and Tolhuizen (see ibid. vol.46, no.9, p.573, 1998). They state that the optimum choice of the slopes used to perform the encoding process in a projection code always results in maximizing the minimum Hamming distance so that d=2 r  相似文献   
5.
The most recent attempts in raising Tc of cuprate superconductors were successful by synthesizing new Hg-based cuprate materials. We discuss some properties of materials from this series with varying numbers of Cu-O planes per unit cell, including the considerable rise of the critical temperature under the influence of external pressure.In the second part of this contribution, various attempts to directly determine the symmetry of the superconducting order parameter of high-Tc cuprates are mentioned and set into perspective. The experimental approaches are all based on probing the phase of the order parameter in suitably connected closed superconducting loops. The evidence for unconventional order-parameter symmetry in these materials is growing.  相似文献   
6.
7.
Multipath propagation in a broadband CDMA environment is described. A propagation model for broadband spread-spectrum signals is presented. Experimental results relating to the sharing of the band by fixed service microwave users and mobile personal communications network (PCN) users are discussed. Field tests indicate that PCN systems can provide high-quality communications when sharing the spectrum with fixed-service microwave systems in suburban and urban areas  相似文献   
8.
Placing the radiators of antenna arrays closer than aggravates the problem of power mismatch. Based on efficiency considerations, a general analysis of this effect is presented, putting forward a simple tool to quantify, compare, and optimize the performance of antenna arrays. This analysis is not restricted with respect to the number of radiators or the degree of compactness. In order to improve power matching, a systematic approach for the design of lossless decoupling and matching networks based on 180 directional couplers is suggested for up to eight radiators. Implications of network losses, which have not yet received appropriate attention by researchers in the past, will be analyzed and discussed by means of a manufactured three-element prototype array.  相似文献   
9.
Cone-beam type X-ray computed tomography (CBCT) is a potential method to measure three-dimensional phase distributions in vessels. An example for that is the measurement of gas profiles in stirred chemical reactors. Such data are highly valuable for the assessment and evaluation of chemical processes, for optimisation of the reactor and stirrer design, and for evaluation of computational fluid dynamics codes used to model the fluid flow and heat transfer in reactive systems. However, there are considerable difficulties for accurate quantitative measurements due to beam hardening and radiation scattering effects. In a theoretical and experimental work we have investigated the non-linear effects of both physical phenomena and developed a suitable measurement setup as well as calibration and software correction methods to achieve a highly accurate measurement of void fraction profiles with CBCT.  相似文献   
10.
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