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   1943篇
  免费   53篇
  国内免费   13篇
电工技术   28篇
综合类   2篇
化学工业   249篇
金属工艺   64篇
机械仪表   50篇
建筑科学   125篇
矿业工程   7篇
能源动力   27篇
轻工业   133篇
水利工程   22篇
石油天然气   9篇
无线电   143篇
一般工业技术   251篇
冶金工业   552篇
原子能技术   28篇
自动化技术   319篇
  2021年   21篇
  2020年   19篇
  2019年   23篇
  2018年   30篇
  2017年   17篇
  2016年   40篇
  2015年   26篇
  2014年   28篇
  2013年   82篇
  2012年   52篇
  2011年   58篇
  2010年   62篇
  2009年   65篇
  2008年   70篇
  2007年   65篇
  2006年   60篇
  2005年   53篇
  2004年   40篇
  2003年   40篇
  2002年   31篇
  2001年   44篇
  2000年   43篇
  1999年   45篇
  1998年   171篇
  1997年   116篇
  1996年   82篇
  1995年   58篇
  1994年   53篇
  1993年   53篇
  1992年   12篇
  1991年   23篇
  1990年   24篇
  1989年   21篇
  1988年   20篇
  1987年   20篇
  1986年   27篇
  1985年   27篇
  1984年   24篇
  1983年   15篇
  1982年   26篇
  1981年   20篇
  1980年   24篇
  1979年   15篇
  1978年   10篇
  1977年   19篇
  1976年   33篇
  1975年   13篇
  1974年   10篇
  1973年   11篇
  1971年   9篇
排序方式: 共有2009条查询结果,搜索用时 312 毫秒
1.
2.
可重定位的基于事务的系统级验证   总被引:2,自引:0,他引:2  
功能验证已经成为开发SoC的主要问题。随着一些复杂SoC的规模超过两千万门,以及对开发和集成嵌入式软件的需求持续增加,软件模拟器已经力所不及。在设计过程需要几百万个时钟周期来充分测试和验证软件功能的情况下,软件仿真器的性能下降到1-5Hz。按照这种速率,软件调试需要几年的时  相似文献   
3.
The NMR solution structure of an immunoglobulin superfamily module of twitchin (Ig 18') has been determined and the kinetic and equilibrium folding behaviour characterised. Thirty molecular coordinates were calculated using a hybrid distance geometry-simulated annealing protocol based on 1207 distance and 48 dihedral restraints. The atomic rms distributions about the mean coordinate for the ensemble of structures is 0.55( +/- 0.09) A for backbone atoms and 1.10( +/- 0.08) A for all heavy atoms. The protein has a topology very similar to that of telokin and the titin Ig domains and thus it falls into the I set of the immunoglobulin superfamily. The close agreement between the predicted and observed structures of Ig 18' demonstrates clearly that the I set profile can be applied in the structure prediction of immunoglobulin-like domains of diverse modular proteins. Folding studies reveal that the protein has relatively low thermodynamic stability, deltaG(H2O)U-F = 4.0 kcal mol(-1) at physiological pH. Unfolding studies suggest that the protein has considerable kinetic stability, the half life of the unfolding is greater than 40 minutes in the absence of denaturant.  相似文献   
4.
Several methodological and ethical issues are addressed in the context of 3 related school-based studies of the primary and targeted prevention of depressive symptoms and disorder in high school adolescents. These issues include obtaining S consent and the protection of confidentiality, minimizing attrition over long-term follow-up periods, the "unit of assignment" issue common to most school-based research, and ensuring therapist fidelity to the intervention protocol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
5.
6.
A study was carried out using simulation to investigate driver responses to lineside signals and signs at various approach speeds. The objectives of the study were: (1) to find out whether train speed would significantly affect signal/sign reading; (2) to examine at which point certain types of signs or signals could be detected or recognised, and (3) to determine a speed cut-off level above which certain types of signs or signals are no longer recognisable or detectable. Fifty-seven train drivers from 12 Train Operating Companies in the UK participated in the trials. Twenty different types of lineside signs and ten types of signals were tested under six different approach speeds ranging from 100 to 350 km/h (62–218 mph). Driver performance measures were ‘time remaining to the signal/sign’ at the point of detection or recognition, and reading error rate. The results showed a significant influence of train speed on driver responses to lineside signals/signs and demonstrated a non-linear relationship between driver responses to signals/signs and approach speed. This has been used to estimate a maximum approach speed limit within which a specific signal or sign can be correctly detected or recognised. The findings and implications of the study are discussed in the paper.  相似文献   
7.
David E. Clarke  Harry Marsh 《Fuel》1985,64(9):1204-1207
This article is a brief summary of the Discussion session held after the presentation of the preceding papers at the conference organized by the Industrial Carbon and Graphite Group of the Society of Chemical Industry, London, March 1984.  相似文献   
8.
This paper describes a module that was introduced into a civil engineering degree program with the help of professional engineers. The aim was to develop a bridge between the world of learning and professional practice by putting students in the role of consulting engineers working with industry to produce a feasible solution to a real inquiry from a client. The module is placed in context by comparing the goals of accredited civil engineering programs in the United Kingdom and America, by describing how it is linked to the degree program and by explaining the matrix developed to identify the skills the students needed to demonstrate their ability to practice as professional engineers. Details of the module are given with examples of student work and feedback.  相似文献   
9.
Exposure to cocaine during fetal development has been demonstrated to produce a variety of brain and behavioral changes. Cocaine is a potent releaser of a variety of neurotransmitters, such as serotonin, which act as developmental signals. Since serotonin plays an important role in astroglial maturation, migration, and growth factor production (e.g. S-100 beta), we proposed that these properties of astroglial cells will be altered in a brain prenatally exposed to cocaine. To observe cocaine's effects on astroglial development, we performed immunocytochemical analyses of a variety of developmental protein makers including BrdU, Gap-43, vimentin, and S100 beta. Our results demonstrate that prenatal cocaine administration produces decreased cell proliferation as measured by BrdU staining, retarded neurite outgrowth as ascertained by increased Gap-43 immunoreactivity, increased density of vimentin-positive radial glial cells, and diminished tissue S100 beta immunoreactivity. Overall, these results suggest that cocaine delays astroglial development. This delay would have profound effects on neuronal development and outgrowth and, thus, development of the entire brain.  相似文献   
10.
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