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   63820篇
  免费   2943篇
  国内免费   229篇
电工技术   976篇
综合类   106篇
化学工业   12285篇
金属工艺   2228篇
机械仪表   3344篇
建筑科学   1433篇
矿业工程   55篇
能源动力   2435篇
轻工业   4644篇
水利工程   282篇
石油天然气   212篇
武器工业   1篇
无线电   11335篇
一般工业技术   12598篇
冶金工业   6564篇
原子能技术   713篇
自动化技术   7781篇
  2023年   587篇
  2022年   929篇
  2021年   1564篇
  2020年   1115篇
  2019年   1155篇
  2018年   1530篇
  2017年   1493篇
  2016年   1855篇
  2015年   1491篇
  2014年   2308篇
  2013年   3965篇
  2012年   3558篇
  2011年   4370篇
  2010年   3344篇
  2009年   3563篇
  2008年   3313篇
  2007年   2795篇
  2006年   2528篇
  2005年   2189篇
  2004年   2074篇
  2003年   1905篇
  2002年   1827篇
  2001年   1451篇
  2000年   1357篇
  1999年   1350篇
  1998年   2481篇
  1997年   1644篇
  1996年   1363篇
  1995年   1080篇
  1994年   814篇
  1993年   757篇
  1992年   546篇
  1991年   542篇
  1990年   466篇
  1989年   454篇
  1988年   356篇
  1987年   316篇
  1986年   298篇
  1985年   264篇
  1984年   222篇
  1983年   178篇
  1982年   159篇
  1981年   148篇
  1980年   148篇
  1979年   113篇
  1978年   107篇
  1977年   141篇
  1976年   183篇
  1975年   90篇
  1974年   78篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
62.
1. Occupational health nurses need a general knowledge of psychiatric medications to work effectively with clients and their off site health providers. 2. Acquiring an understanding of the major classes of medications--anti-psychotic, anti-anxiety, anti-depressant, and antimanic--is important. 3. It is helpful to understand under what conditions and with which conditions psychotropic medications are helpful.  相似文献   
63.
64.
65.
66.
High performance enhancement mode InP MISFET's have been successfully fabricated by using the sulfide passivation for lower interface states and with photo-CVD grown P3N5 film used as gate insulator. The MISFET's thus fabricated exhibited exhibited pinch-off behavior with essentially no hysteresis. Furthermore the device showed a superior stability of drain current. Specifically under the gate bias of 2 V for 104 seconds the room temperature drain current was shown to reduce from the initial value merely by 2.9% at the drain voltage of 4 V. The effective electron mobility and extrinsic transconductance are found to be about 2300 cm 2/V·s and 2.7 mS/mm, respectively. The capacitance-voltage characteristics of the sulfide passivated InP MIS diodes show little hysteresis and the minimum density of interface trap states as low as 2.6×1014/cm2 eV has been attained  相似文献   
67.
Several distributed power control algorithms that can achieve carrier-to-interference ratio (CIR) balancing with probability one have been proposed previously for cellular mobile systems. In these algorithms, only local information is used to adjust transmitting power. However, a normalization procedure is required in each iteration to determine transmitting power and, thus, these algorithms are not fully distributed. In this paper, we present a distributed power control algorithm which does not need the normalization procedure. We show that the proposed algorithm can achieve CIR balancing with probability one. Moreover, numerical results reveal our proposed scheme performs better than the algorithm presented in Grandhi et al. [1994]. The excellent performance and the fully distributed property make our proposed algorithm a good choice for cellular mobile systems  相似文献   
68.
The matrix pencil (MP) method, based on the singular value decomposition (SVD), is applied to quantitative NMR spectroscopy. Its relationship to other SVD-based methods is also presented. Simulations and applications are given to demonstrate the capability of superior performance.©1993 John Wiley & Sons Inc  相似文献   
69.
The effect of DC flux on the core loss is examined for the practical range of power and frequency. Relevant core loss equations are derived and applied to an optimization algorithm to determine the minimum core loss at a given ratio of s (DC flux density to AC peak flux density). It has been found that the curves of hysteresis loss density versus the ratio of s exhibit a peak at a critical ratio. Below or above this critical ratio, the loss density decreases drastically. On the other hand, the curves of eddy-current loss density versus the ratio of s exhibits a minimum point at a critical ratio. Below or above this critical ratio, the loss density increases gradually  相似文献   
70.
In addition to providing electrical connections, solder is useful in the formation of passive, precision alignments for optoelectronic packaging. Different designs have demonstrated micrometer-level alignment accuracies, and the aligned structures are becoming more and more complex. Solder engineering has been successfully introduced into the field of optoelectronics, and it is expected to be applied to many other areas demanding low-cost, precision alignments.  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