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   28240篇
  免费   2451篇
  国内免费   1476篇
电工技术   1768篇
技术理论   1篇
综合类   2004篇
化学工业   4644篇
金属工艺   1505篇
机械仪表   1810篇
建筑科学   2207篇
矿业工程   913篇
能源动力   772篇
轻工业   2499篇
水利工程   545篇
石油天然气   1772篇
武器工业   210篇
无线电   2807篇
一般工业技术   3033篇
冶金工业   1327篇
原子能技术   323篇
自动化技术   4027篇
  2024年   145篇
  2023年   513篇
  2022年   896篇
  2021年   1219篇
  2020年   876篇
  2019年   743篇
  2018年   853篇
  2017年   939篇
  2016年   833篇
  2015年   1114篇
  2014年   1479篇
  2013年   1798篇
  2012年   1876篇
  2011年   2154篇
  2010年   1849篇
  2009年   1780篇
  2008年   1798篇
  2007年   1637篇
  2006年   1559篇
  2005年   1396篇
  2004年   926篇
  2003年   767篇
  2002年   721篇
  2001年   627篇
  2000年   622篇
  1999年   588篇
  1998年   455篇
  1997年   420篇
  1996年   354篇
  1995年   291篇
  1994年   266篇
  1993年   181篇
  1992年   155篇
  1991年   86篇
  1990年   68篇
  1989年   38篇
  1988年   47篇
  1987年   28篇
  1986年   15篇
  1985年   7篇
  1984年   14篇
  1983年   8篇
  1982年   8篇
  1981年   7篇
  1980年   6篇
  1979年   2篇
  1959年   2篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
To deal with the planarization problem widely used in many applications including routing very-large-scale integration (VLSI) circuits, this paper points out that only when its vertices are arranged in some specific order in a line can a planar graph be embedded on a line without any cross connections or cross edges. Energy function is proposed to meet the need of embedding a graph on a single line and route it correctly. A Hopfield network is designed according to the proposed energy function for such embedding and routing. The advantage of the proposed method is that it not only can detect if a graph is a planar one or not, but also can embed a planar graph or the maximal planar subgraph of a non-planar graph on a single line. In addition, simulated annealing is employed for helping the network to escape from local minima during the running of the Hopfield network. Experiments of the proposed method and its comparison with some existent conventional methods were performed and the results indicate that the proposed method is of great feasibility and effectiveness especially for the planarization problem of large graphs.  相似文献   
42.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity.  相似文献   
43.
The prototype of a CO2 sensor made of CuO–BaTiO3, which has capacitance sensitive effect, is designed based on the pn heterojunctions of CuO and BaTiO3 semiconductors. The preparation of BaTiO3 semiconductor powders is pointed out, using the coprecipitation and semiconducting techniques. The characteristic quantities relating to the capacitance sensitive effect of the sensor are studied systematically with the aid of a gas tester. A reasonable mechanism of the sensor is proposed.  相似文献   
44.
高速公路联网系统车道收费软件的设计与实现   总被引:1,自引:0,他引:1  
张明  舒勤  潘宏 《计算机工程》2001,27(12):130-131,134
通过对当前常用的车道收费软件的分析对比,提出了一种基于Mini Server战术的车道收费软件的体系结构,并就其实现技术及性能特点进行了详细的论述,还对Mini Server控制下多Agent通信策略等方面进行了较深入的描述。  相似文献   
45.
首先对CIMS进行了简述,然后介绍了某研究所科研生产的现状,最后提出某研究所实现CIMS的可能途径。  相似文献   
46.
Acoustic emission (AE) experiments have been performed on gas-saturated coal specimens under conventional triaxial compression. The AE characteristics were investigated for a methane gas flow through the coal specimen. One AE parameter, AE count, when normalized by the total count number was used to represent the damage evolution in the gassy coal. It is shown that this AE parameter is a reasonable indicator for damage occurring within the coal specimen since its envelope has almost the same shape as the complete stress–strain curve, except for a short time delay. In addition, the change in AE count is highly consistent with the change in coal permeability. Test results also show that methane containing coal emits a small number of AE events before entering the yield stage. AE activity gradually increases during the yield process up to the peak stress. The lowest permeability corresponds to the highest AE activity, implying failure will soon occur. An AE based constitutive model was constructed and the theoretical results agree well with those of experiments.  相似文献   
47.
48.
采用遗传算法建立贝叶斯网络的优化学习结构,一直是贝叶斯网络研究倍受关注的课题.传统遗传算法的个体设计存在需要反复进行无环性检验的问题,降低了进化效率.针对这个问题,提出一种新的个体编码方式.考虑到进化过程中家族得分的可继承性,提出基于家族继承的结构评分改进算法,进而设计相应的改进遗传算法.实验结果表明,改进算法在BN建网精度与效率上都得到明显提升.  相似文献   
49.
林宗义 《化工时刊》2005,19(8):67-69
通过对FIX-450型强制循环泵操作环境、工作状况和结构参数的分析,找出其运行电流高的原因,并采取改进措施,使其运行电流恢复至正常水平。  相似文献   
50.
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