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   109656篇
  免费   8601篇
  国内免费   4839篇
电工技术   6437篇
技术理论   5篇
综合类   7450篇
化学工业   18603篇
金属工艺   6453篇
机械仪表   6788篇
建筑科学   9450篇
矿业工程   3044篇
能源动力   2957篇
轻工业   7587篇
水利工程   2017篇
石油天然气   6057篇
武器工业   923篇
无线电   11774篇
一般工业技术   12673篇
冶金工业   5401篇
原子能技术   1375篇
自动化技术   14102篇
  2024年   436篇
  2023年   1818篇
  2022年   3005篇
  2021年   4112篇
  2020年   3212篇
  2019年   2666篇
  2018年   3035篇
  2017年   3498篇
  2016年   2980篇
  2015年   4078篇
  2014年   5262篇
  2013年   6318篇
  2012年   6994篇
  2011年   7442篇
  2010年   6524篇
  2009年   6374篇
  2008年   6184篇
  2007年   5950篇
  2006年   6100篇
  2005年   5363篇
  2004年   3692篇
  2003年   3224篇
  2002年   3071篇
  2001年   2702篇
  2000年   2776篇
  1999年   3016篇
  1998年   2419篇
  1997年   1943篇
  1996年   1980篇
  1995年   1608篇
  1994年   1322篇
  1993年   913篇
  1992年   765篇
  1991年   590篇
  1990年   442篇
  1989年   364篇
  1988年   287篇
  1987年   192篇
  1986年   129篇
  1985年   89篇
  1984年   59篇
  1983年   40篇
  1982年   44篇
  1981年   36篇
  1980年   27篇
  1979年   7篇
  1978年   2篇
  1965年   2篇
  1959年   1篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm.  相似文献   
32.
PURPOSE: To evaluate the accuracy of measuring intraocular pressure by handheld non-contact applanation tonometer. METHOD: 58 patients' (113 eyes) intraocular pressure were measured by Keeler, non-contact tonometer and R 900 Goldmann applanation tonometer and the results of measurement of intraocular pressure by the two kinds of tonometers were compared. RESULT: The mean intraocular pressure measured by non-contact is 16.31 +/- 5.59 mmHg and 17.49 +/- 6.13 mmHg (1 mmHg = 0.1333 kPa) by Goldmann applanation tonometer, respectively. There was no statistical significance to be found (P > 0.05) between the two methods. By linear correlation and regression analysis, a positive correlation was found between the two methods (r = 0.8942, b = 0.8154). CONCLUSION: The handheld non-contact tonometer has the same accuracy and reliability of measurement of intraocular pressure comparing with Goldmann applanation tonometer, and it can be used in glaucoma clinic and screening.  相似文献   
33.
本文提出在安替比林存在下,以3,5-diBr-PADAP为显色剂,分光光度测定微量锆的新方法。在pH1~2的HCl介质中,锆(W)与试剂和安替比林形成配合比为1:1:1的红色三元配合物,最大吸收值在615nm波长处,摩尔吸光系数ε=1.35×10~5。锆(Ⅳ)量在0~25μg/25ml范围内,遵守比尔定律。方法简单、快速、准确。若采用钽试剂—苯萃取法分离共存离子,可适用于钽铌矿和合金中痕量锆的测定。  相似文献   
34.
In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks.  相似文献   
35.
本文着重介绍了构成《现代勘探决策理论系统》的5个主要计算机模块,即:生油岩热演化处理、求任意曲边形面积、数学模拟预测资源量、勘探经济评价分析及决策、辅助处理等模块。该系统曾在塔里木盆地和准噶尔盆地的油气资源评价和勘探决策中发挥了作用,受到了专家和用户的好评。  相似文献   
36.
An analytical method is presented for calculating the resonant frequency andQ-factor of a superconducting dielectric disk resonator operating in millimeter-wave regime with whispering-gallery mode. Resonant frequency shift due to the optical generation of quasi-particles in superconducting film is investigated as a function of photon flux. An optically tunable resonant frequency of about 500 MHz is estimated, and good agreement is found between numerical results and experimental ones.  相似文献   
37.
PURPOSE: The purpose of this research is to obtain the tablet coating distribution from weight distributions of uncoated and coated tablets. METHODS: The method of deconvolution with digital smoothing was used to calculate the distribution of coating applied to a tablet population from separate random measurements of individual uncoated and coated tablets. RESULTS: It was demonstrated that the calculated coating weight distribution agrees well with the measured distribution. The effect of the smoothing factor on the solution is illustrated. CONCLUSIONS: This method can be used during development to facilitate process scale-up/optimization. In routine production, the method can assess the reproducibility and consistency of a coating process.  相似文献   
38.
根据我国专利法的原则,在对我国催化重整和芳烃生产专利检索过程和结果进行分析的基础上,阐述了对目前我国催化重整工艺专利市场的几点看法并提出对策。  相似文献   
39.
Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results.  相似文献   
40.
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