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   309818篇
  免费   3711篇
  国内免费   714篇
电工技术   6193篇
综合类   560篇
化学工业   46743篇
金属工艺   10325篇
机械仪表   8820篇
建筑科学   7897篇
矿业工程   862篇
能源动力   8571篇
轻工业   31080篇
水利工程   2532篇
石油天然气   3669篇
武器工业   8篇
无线电   39696篇
一般工业技术   58446篇
冶金工业   56661篇
原子能技术   5458篇
自动化技术   26722篇
  2021年   2278篇
  2019年   2139篇
  2018年   3609篇
  2017年   3448篇
  2016年   3539篇
  2015年   2541篇
  2014年   4441篇
  2013年   14275篇
  2012年   7366篇
  2011年   10113篇
  2010年   7900篇
  2009年   9134篇
  2008年   9601篇
  2007年   9578篇
  2006年   8505篇
  2005年   7889篇
  2004年   7760篇
  2003年   7498篇
  2002年   7336篇
  2001年   7543篇
  2000年   7207篇
  1999年   7549篇
  1998年   17665篇
  1997年   12838篇
  1996年   10099篇
  1995年   7874篇
  1994年   7204篇
  1993年   6906篇
  1992年   5287篇
  1991年   5066篇
  1990年   4933篇
  1989年   4779篇
  1988年   4673篇
  1987年   3887篇
  1986年   4009篇
  1985年   4717篇
  1984年   4275篇
  1983年   4022篇
  1982年   3601篇
  1981年   3761篇
  1980年   3456篇
  1979年   3418篇
  1978年   3227篇
  1977年   3814篇
  1976年   4847篇
  1975年   2780篇
  1974年   2660篇
  1973年   2675篇
  1972年   2215篇
  1971年   1963篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
A rheological equation of state for wood which allows for the running values of its porosity and humidity is considered.  相似文献   
122.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes.  相似文献   
123.
This paper presents results of reliability investigation of 20 V N-Drift MOS transistor in 0.13 μm CMOS technology. Due to high performances required for CMOS applications, adding high voltage devices becomes a big challenge to guarantee the reliability criteria. In this context, new reliability approaches are needed. Safe Operating Area are defined for switch, Vds limited and Vgs limited applications in order to improve circuit designs. For Vds limited applications, deep doping dose effects in drift area are investigated in correlation to lifetime evaluations based on device parameter shifts under hot carrier stressing. To further determine the amount and locations of hot carriers injections, accurate 2D technological and electrical simulations are performed and permit to select the best compromise between performance and reliability for N-Drift MOS transistor.  相似文献   
124.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method.  相似文献   
125.
Inference of message sequence charts   总被引:1,自引:0,他引:1  
Software designers draw message sequence charts for early modeling of the individual behaviors they expect from the concurrent system under design. Can they be sure that precisely the behaviors they have described are realizable by some implementation of the components of the concurrent system? If so, can we automatically synthesize concurrent state machines realizing the given MSCs? If, on the other hand, other unspecified and possibly unwanted scenarios are "implied" by their MSCs, can the software designer be automatically warned and provided the implied MSCs? In this paper, we provide a framework in which all these questions are answered positively. We first describe the formal framework within which one can derive implied MSCs and then provide polynomial-time algorithms for implication, realizability, and synthesis.  相似文献   
126.
127.
The editors of this special issue asked Todd LaPorte to reflect on the issues that emerge from the discussions in this special issue and, more in general, from the discussions that have proliferated in the wake of recent crises and disasters. In his contribution, Professor LaPorte contemplates what political leaders can do to prepare for catastrophic surprises. A crucial initiative, he argues, would be the initiation of a public discussion about the level of distress that a society is willing to accept in the pursuit of efficient, reliable critical infrastructures.  相似文献   
128.
129.
130.
The US Centers for Disease Control and Prevention (CDC) created the Public Health Information Network to advance fully capable, interoperable information systems in public health organizations. PHIN prioritizes public health information systems' functional requirements, capabilities, performance measures, and operational characteristics while letting the architects of those systems choose enabling approaches, methods, and concepts to meet the requirements. PHIN also provides a certification process for public health administrators to evaluate their information infrastructure's quality. The certification process is important because affected organizations often depend on certification for continued funding.  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