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   9006篇
  免费   317篇
  国内免费   40篇
电工技术   121篇
综合类   22篇
化学工业   2100篇
金属工艺   167篇
机械仪表   231篇
建筑科学   573篇
矿业工程   31篇
能源动力   171篇
轻工业   772篇
水利工程   54篇
石油天然气   11篇
武器工业   1篇
无线电   594篇
一般工业技术   1444篇
冶金工业   1525篇
原子能技术   70篇
自动化技术   1476篇
  2023年   58篇
  2022年   120篇
  2021年   144篇
  2020年   105篇
  2019年   119篇
  2018年   168篇
  2017年   110篇
  2016年   191篇
  2015年   191篇
  2014年   249篇
  2013年   565篇
  2012年   397篇
  2011年   544篇
  2010年   410篇
  2009年   389篇
  2008年   432篇
  2007年   423篇
  2006年   363篇
  2005年   312篇
  2004年   291篇
  2003年   221篇
  2002年   227篇
  2001年   173篇
  2000年   165篇
  1999年   157篇
  1998年   260篇
  1997年   195篇
  1996年   160篇
  1995年   140篇
  1994年   123篇
  1993年   136篇
  1992年   130篇
  1991年   75篇
  1990年   92篇
  1989年   79篇
  1988年   94篇
  1987年   66篇
  1986年   54篇
  1985年   79篇
  1984年   94篇
  1983年   60篇
  1982年   66篇
  1981年   83篇
  1980年   68篇
  1979年   85篇
  1978年   68篇
  1977年   67篇
  1976年   57篇
  1975年   58篇
  1973年   47篇
排序方式: 共有9363条查询结果,搜索用时 15 毫秒
51.
Concurrent Constraint Programming (CCP) has been used over the last two decades as an elegant and expressive model for concurrent systems. It models systems of agents communicating by posting and querying partial information, represented as constraints over the variables of the system. This covers a vast variety of systems as those arising in biological phenomena, reactive systems, net-centric computing and the advent of social networks and cloud computing. In this paper we survey the main applications, developments and current trends of CCP.  相似文献   
52.
要证实哪个国家的博物馆的密度最高是很困难的,因为这在很大程度上取决于所使用的标准。然而,荷兰确实进入了世界前10名的行列。——荷兰博物馆学家彼得·冯·门斯奇  相似文献   
53.
54.
55.
PROven(R)系统的开发为了减少焦炉的排放,过去已进行了多种技术的开发.但是从焦炉炉门、装料孔边缘等处逸散物的减少,已受到工艺技术的制约.一个基本的制约因素是,在集气总管内的压力和联接到总管的所有碳化室内的压力之间有着密不可分的关系.  相似文献   
56.
The quality of visual perception with retinal prostheses strongly depends on the local selectivity. Electrode arrays at the surface of the retina should excite exclusively cells within a local area but they are expected to co-stimulate bypassing axons originating from ganglion cells of the outer regions. Long electrodes parallel to these axons are shown to be good candidates for avoiding the co-stimulation phenomenon. Efficiency of focal excitation depends on the length and resistance of the electrodes.  相似文献   
57.
讨论了斜坡电流测试的相关参数如电流斜坡速率、步长及电流倍增速率对测试结果击穿电荷具有的严重影响。指出斜坡电流测试中各个参数的设定、影响及其相关性,使斜坡电流测试的结果具有可比较性。同时,讨论了由于斜坡电流测试本身的特性,击穿电荷具有非连续性,针对击穿电荷的非连续性,提供了一种统计上的数据处理方法,并且根据工程上不同的定性比较结果提供了不同的统计比较方法,可以对非连续的斜坡电流测试结果进行定量的统计比较。在产品验证或生产线出现异常时,能够进行统计上的比较,给出定量的结果。据此能对生产线的稳定性或异常事件对产品的影响给出明确的结论,为受影响的产品的处置提供定量的数据支持。这是首次对斜坡电流测试数据的统计定量分析。  相似文献   
58.
For applications ranging from phase equilibria to the processing of second-generation high T c superconductor-coated-conductors, phase diagrams constructed under carbonate-free conditions are needed. Subsolidus phase equilibria of BaO-R2O3-CuO z (R = Ho) have been investigated at (810°C), 21 kPa (875°C) and 0.1 MPa (850 and 930°C) by applying controlled atmosphere methods to minimize the presence of carbonate and CO2 and H2O contamination. Under carbonate-free conditions, most of these phase diagrams are different from those reported in the literature. In this paper, we also review and compare the phase diagrams of ten BaO-R2O3-CuO z systems (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm and Yb) that were previously determined in this laboratory under Among these diagrams, a distinct trend of phase formation and tie-line relationships is observed.  相似文献   
59.
The criteria used to determine electrical failure was explored during accelerated testing of underfilled flip chip joints as a function of both different thermal cycling conditions and different sampling methods. The criteria was based on resistance measurements of daisy-chained solder joints monitored in situ and by endpointing. The sensitivity of the resistance criteria was found to depend strongly on test conditions and often could not be categorized into simple pass/fail groupings. Also, extremely small resistance changes were measured for joints with through-cracks generated by fatigue. Experimental error associated with fixing the cycles to failure was minimized by monitoring the absolute changes in resistance as a function of cycling time while simultaneously measuring the temperature dependence of resistance as the joints degrade. Failure times derived from interval part monitoring closely approximated in situ monitoring, but the resistance measurements for mild cycling conditions required a high degree of accuracy. Finally, a tunneling model is proposed to explain the resistance behavior of cracked joints.  相似文献   
60.
An image analysis technique has been developed to quantitatively describe the fine vascular patterns observed in ligament tissue. The longitudinal orientational distribution and total vessel volume of India-ink-perfused blood vessel segments in normal and healing ligaments were determined. The methods involved special vascular preparation of adult rabbit knee medial collateral ligaments (MCL) by India-ink perfusion. Black and white microscope images of ink-perfused tissue sections were subjected to a thresholding procedure to binarize digitized ligament images, which were then skeletonized and analyzed for directional distribution based on the least-squares technique. Analysis of medial collateral ligaments in New Zealand White rabbits using this method has shown that scarred tissue is more vascular and has a more chaotic angular distribution of blood-vessel segments than normal ligament tissue.  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