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   450601篇
  免费   7191篇
  国内免费   2311篇
电工技术   8773篇
技术理论   5篇
综合类   1442篇
化学工业   70161篇
金属工艺   18175篇
机械仪表   13316篇
建筑科学   11437篇
矿业工程   2940篇
能源动力   10430篇
轻工业   42560篇
水利工程   4971篇
石油天然气   9192篇
武器工业   254篇
无线电   47936篇
一般工业技术   86518篇
冶金工业   84373篇
原子能技术   9762篇
自动化技术   37858篇
  2021年   4261篇
  2020年   3048篇
  2019年   3733篇
  2018年   6200篇
  2017年   6195篇
  2016年   6714篇
  2015年   4971篇
  2014年   7806篇
  2013年   20454篇
  2012年   12807篇
  2011年   16959篇
  2010年   13665篇
  2009年   14831篇
  2008年   15749篇
  2007年   15893篇
  2006年   13704篇
  2005年   12270篇
  2004年   11215篇
  2003年   10690篇
  2002年   10353篇
  2001年   10365篇
  2000年   9945篇
  1999年   10149篇
  1998年   24135篇
  1997年   17366篇
  1996年   13403篇
  1995年   9908篇
  1994年   9004篇
  1993年   8743篇
  1992年   6754篇
  1991年   6419篇
  1990年   6294篇
  1989年   6344篇
  1988年   5981篇
  1987年   5173篇
  1986年   5087篇
  1985年   5865篇
  1984年   5605篇
  1983年   5184篇
  1982年   4569篇
  1981年   4887篇
  1980年   4476篇
  1979年   4723篇
  1978年   4607篇
  1977年   5040篇
  1976年   6813篇
  1975年   4057篇
  1974年   3821篇
  1973年   3889篇
  1972年   3213篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described.  相似文献   
63.
A fiber optic ring network, such as fiber distributed data interface (FDDI), can be operated over multiple wavelengths on its existing fiber plant consisting of point-to-point fiber links. Using wavelength division multiplexing (WDM) technology, FDDI nodes can be partitioned to operate over multiple subnetworks, with each subnetwork operating independently on a different wavelength, and inter-subnetwork traffic forwarding performed by a bridge. For this multiwavelength version of FDDI, which we refer to as wavelength distributed data interface (WDDI), we examine the necessary upgrades to the architecture of a FDDI node, including its possibility to serve as a bridge. The main motivation behind this study is that, as network traffic scales beyond (the single-wavelength) FDDI's information-carrying capacity, its multiwavelength version, WDDI, can gracefully accommodate such traffic growth. A number of design choices exist in constructing a good WDDI network. Specifically, we investigate algorithms using which, based on prevailing traffic conditions, partitioning of nodes into subnetworks can be performed in an optimized fashion. Our algorithms partition the nodes into subrings, such that the total traffic flow in the network and/or the network-wide average packet delay is minimized  相似文献   
64.
A CEC-funded project has been performed to tackle the problem of producing an advanced Life Monitoring System (LMS) which would calculate the creep and fatigue damage experienced by high temperature pipework components. Four areas were identified where existing Life Monitoring System technology could be improved:
1. 1. the inclusion of creep relaxation
2. 2. the inclusion of external loads on components
3. 3. a more accurate method of calculating thermal stresses due to temperature transients
4. 4. the inclusion of high cycle fatigue terms.

The creep relaxation problem was solved using stress reduction factors in an analytical in-elastic stress calculation. The stress reduction factors were produced for a number of common geometries and materials by means of non-linear finite element analysis. External loads were catered for by producing influence coefficients from in-elastic analysis of the particular piping system and using them to calculate bending moments at critical positions on the pipework from load and displacement measurements made at the convenient points at the pipework. The thermal stress problem was solved by producing a completely new solution based on Green's Function and Fast Fourier transforms. This allowed the thermal stress in a complex component to be calculated from simple non-intrusive thermocouple measurements made on the outside of the component. The high-cycle fatigue problem was dealt with precalculating the fatigue damage associated with standard transients and adding this damage to cumulative total when a transient occurred.

The site testing provided good practical experience and showed up problems which would not otherwise have been detected.  相似文献   

65.
Summary The synthesis of new high optical abrasion resistance coating materials has been undertaken by functionalizing melamine and tris(m-aminophenyl)phosphine oxide with a triethoxysilane containing reagent. These highly functionalized compounds have been used for coating a bis-phenol-A polycarbonate substrate by the sol-gel method. Preliminary data shows the abrasion resistance of the polymer substrate is considerably improved when it is coated by these optically clear materials.  相似文献   
66.
67.
68.
Functional Properties and Food Applications of Rapeseed Protein Concentrate   总被引:1,自引:0,他引:1  
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone.  相似文献   
69.
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.  相似文献   
70.
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