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   311311篇
  免费   23366篇
  国内免费   12152篇
电工技术   16678篇
技术理论   36篇
综合类   19144篇
化学工业   53739篇
金属工艺   18074篇
机械仪表   19717篇
建筑科学   24625篇
矿业工程   10176篇
能源动力   8470篇
轻工业   19085篇
水利工程   5157篇
石油天然气   21352篇
武器工业   2382篇
无线电   34031篇
一般工业技术   36621篇
冶金工业   16209篇
原子能技术   3053篇
自动化技术   38280篇
  2024年   1348篇
  2023年   5079篇
  2022年   8675篇
  2021年   12455篇
  2020年   9263篇
  2019年   7917篇
  2018年   8851篇
  2017年   9946篇
  2016年   8675篇
  2015年   12074篇
  2014年   14916篇
  2013年   17734篇
  2012年   19188篇
  2011年   20792篇
  2010年   18002篇
  2009年   17086篇
  2008年   16595篇
  2007年   16176篇
  2006年   17029篇
  2005年   14995篇
  2004年   9717篇
  2003年   8765篇
  2002年   8422篇
  2001年   7368篇
  2000年   7698篇
  1999年   9007篇
  1998年   7140篇
  1997年   6093篇
  1996年   5703篇
  1995年   4708篇
  1994年   3907篇
  1993年   2745篇
  1992年   2216篇
  1991年   1672篇
  1990年   1238篇
  1989年   973篇
  1988年   789篇
  1987年   537篇
  1986年   408篇
  1985年   272篇
  1984年   189篇
  1983年   124篇
  1982年   134篇
  1981年   91篇
  1980年   80篇
  1979年   24篇
  1978年   2篇
  1965年   2篇
  1959年   2篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Li  Yongming  Zhang  Xinyue  Wang  Pin  Zhang  Xiaoheng  Liu  Yuchuan 《Neural computing & applications》2021,33(15):9733-9750
Neural Computing and Applications - Speech diagnosis of Parkinson’s disease (PD) as a non-invasive and simple diagnosis method is particularly worth exploring. However, the number of samples...  相似文献   
142.
We present a simple and efficient approach for continuous collision detection of deforming triangles based on conservative advancement. The efficiency of our approach is due to a sequence of simple collision-free conditions for deforming triangles. In our experiment, we show that our CCD algorithm achieves 2-30 times performance improvement over existing algorithms for triangle primitives.  相似文献   
143.
Interactive genetic algorithms are effective methods of solving optimization problems with implicit (qualitative) criteria by incorporating a user's intelligent evaluation into traditional evolution mechanisms. The heavy evaluation burden of the user, however, is crucial and limits their applications in complex optimization problems. We focus on reducing the evaluation burden by presenting a semi-supervised learning assisted interactive genetic algorithm with large population. In this algorithm, a population with many individuals is adopted to efficiently explore the search space. A surrogate model built with an improved semi-supervised learning method is employed to evaluate a part of individuals instead of the user to alleviate his/her burden in evaluation. Incorporated with the principles of the improved semi-supervised learning, the opportunities of applying and updating the surrogate model are determined by its confidence degree in estimation, and the informative individuals reevaluated by the user are selected according to the concept of learning from mistakes. We quantitatively analyze the performance of the proposed algorithm and apply it to the design of sunglasses lenses, a representative optimization problem with one qualitative criterion. The empirical results demonstrate the strength of our algorithm in searching for satisfactory solutions and easing the evaluation burden of the user.  相似文献   
144.
长寿老人,高血压患者及健康学生头发中微量元素的分析   总被引:2,自引:1,他引:1  
吴小凤  张钰蓉 《核技术》1989,12(4):243-245
  相似文献   
145.
Morphology and geometry of melted zones, cooling rates, microstructure and microhardness in the laser-glazed Fe-4%C-10%Sn alloy have been investigated. The computer simulation on the basis of the moving gaussian source model was used successfully to predict the maximum width and depth of the melted zone and the cooling rate. The microstructure from the surface to the bottom of the laser-melted zone is a non-crystalline phase, dendritic grains and a microcrystalline zone successively. Values of the averaged-spacing of the non-crystalline phase are 0.2056 and 0.1219nm, respectively; twinned martensites, having an axial ratioc/a of 1.128, existed in dendritic grains, and carbides of Fe3 C at the interdendritic regions; the microcrystalline zone was composed of -Fe and a new bet (a=0.415 nm,c=0.955 nm) phase. The different microstructure in the melted zone can be explained by the results of the heat flow calculation. A fine eutectic structure (-Fe + Fe3C) was observed in heat-affected zones. Microhardness of the eutectic structure can be predicted by the empirical relation of fracture stress to the interlamellar spacing of pearlite.  相似文献   
146.
经食道心房调搏的放射性核素心血管造影   总被引:1,自引:0,他引:1  
本文应用反符合电路剔除调搏脉冲干扰的方法,制成经食道心房调搏心电心音门电路触发装置,用于经食道心房调搏的核素心血管造影。参考Tzivoni标准,当逐级增加调搏心率至140次/min或亚极量心率后发现:冠心病人有调搏后EF降低;急性心肌梗塞病人EF减低更为明显,并呈室壁反向运动。因此,心房调搏核素心血管造影有助于冠心病,特别是心肌梗塞的诊断。  相似文献   
147.
The equilibrium Ca3P2(s) = 3[Ca] + 2[P] was studied at 1600 ° by equilibrating liquid iron, saturated with Ca3P2, and contained in a TiN crucible, with Ca vapor. The source of Ca was liquid Ca contained in an Mo crucible, and the vapor pressure of Ca was varied by varying the position of the Mo crucible in the temperature gradient of a vertical tube furnace. A least-squares analysis of the data gave and. The simultaneous equilibria CaO(s) = [Ca] + [O] and CaS(s) = [Ca] + [S] were studied at 1600 ° by equilibrating liquid iron, contained in a pressed and sintered CaO-CaS crucible with Ca vapor. The advantage of this technique is that two equilibrium constants,K cas andK cao, and two interaction coefficients, and can be determined from one set of experiments. It was determined that, at 1600 °,K cas = 5.9 × 10−8 K cao = 5.5 × 10−9,, and. Formerly Graduate Students  相似文献   
148.
本文应用自动控制理论“自适应在线辨识”解决了混凝土大坝混凝土一、二期冷却的自动控制问题。通过预埋的电阻温度计实时量测温度,实时调节循环冷却水系统的流量和水温或是毋须进行通水,以便达到良好的冷却质量和经济节约的目的。  相似文献   
149.
主要介绍了利用多媒体手段可以促进物理课堂教学。提高教学质量。  相似文献   
150.
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