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   300202篇
  免费   7095篇
  国内免费   1859篇
电工技术   5750篇
技术理论   5篇
综合类   1197篇
化学工业   49818篇
金属工艺   11700篇
机械仪表   8595篇
建筑科学   7921篇
矿业工程   1736篇
能源动力   6567篇
轻工业   31211篇
水利工程   3280篇
石油天然气   6149篇
武器工业   249篇
无线电   30098篇
一般工业技术   56055篇
冶金工业   56141篇
原子能技术   5812篇
自动化技术   26872篇
  2021年   3531篇
  2020年   2481篇
  2019年   2907篇
  2018年   4906篇
  2017年   4890篇
  2016年   5298篇
  2015年   3918篇
  2014年   6052篇
  2013年   14156篇
  2012年   10091篇
  2011年   12513篇
  2010年   9884篇
  2009年   10327篇
  2008年   11301篇
  2007年   11173篇
  2006年   9637篇
  2005年   8365篇
  2004年   7576篇
  2003年   7018篇
  2002年   6924篇
  2001年   6754篇
  2000年   6337篇
  1999年   6421篇
  1998年   15688篇
  1997年   11256篇
  1996年   8386篇
  1995年   6208篇
  1994年   5644篇
  1993年   5506篇
  1992年   4141篇
  1991年   3946篇
  1990年   4025篇
  1989年   3957篇
  1988年   3700篇
  1987年   3167篇
  1986年   3213篇
  1985年   3592篇
  1984年   3487篇
  1983年   3197篇
  1982年   2837篇
  1981年   3055篇
  1980年   2784篇
  1979年   2959篇
  1978年   2840篇
  1977年   3009篇
  1976年   4060篇
  1975年   2534篇
  1974年   2356篇
  1973年   2388篇
  1972年   2023篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
Photonic Network Communications - Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous...  相似文献   
52.
53.
54.
55.
Metallurgical and Materials Transactions A - The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y...  相似文献   
56.
Fefelov  S. A.  Kazakova  L. P.  Bogoslovskiy  N. A.  Bylev  A. B.  Yakubov  A. O. 《Semiconductors》2020,54(4):450-453
Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...  相似文献   
57.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided.  相似文献   
58.
The Journal of Supercomputing - Infrastructure-as-a-service container-based virtualization is gaining interest as a platform for running distributed applications. With increasing scale of cloud...  相似文献   
59.
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation.  相似文献   
60.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  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