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   718387篇
  免费   16804篇
  国内免费   5858篇
电工技术   17036篇
技术理论   2篇
综合类   6228篇
化学工业   108414篇
金属工艺   28479篇
机械仪表   23489篇
建筑科学   23225篇
矿业工程   4407篇
能源动力   18792篇
轻工业   67197篇
水利工程   7726篇
石油天然气   12205篇
武器工业   703篇
无线电   88520篇
一般工业技术   131635篇
冶金工业   122096篇
原子能技术   12884篇
自动化技术   68011篇
  2021年   7750篇
  2020年   5602篇
  2019年   6093篇
  2018年   9158篇
  2017年   9620篇
  2016年   9772篇
  2015年   8764篇
  2014年   13389篇
  2013年   34096篇
  2012年   21297篇
  2011年   28328篇
  2010年   22811篇
  2009年   24993篇
  2008年   25994篇
  2007年   25897篇
  2006年   23504篇
  2005年   21312篇
  2004年   19222篇
  2003年   18353篇
  2002年   18052篇
  2001年   17732篇
  2000年   16612篇
  1999年   17187篇
  1998年   37189篇
  1997年   27579篇
  1996年   21508篇
  1995年   16826篇
  1994年   14913篇
  1993年   14310篇
  1992年   10841篇
  1991年   10432篇
  1990年   9883篇
  1989年   9549篇
  1988年   9207篇
  1987年   7792篇
  1986年   7746篇
  1985年   9190篇
  1984年   8730篇
  1983年   7709篇
  1982年   7261篇
  1981年   7331篇
  1980年   6950篇
  1979年   6795篇
  1978年   6608篇
  1977年   7816篇
  1976年   10343篇
  1975年   5745篇
  1974年   5491篇
  1973年   5403篇
  1972年   4582篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Lin  Jun-You  Yang  Chih-Hai 《Scientometrics》2020,122(1):1-2
Scientometrics - University–industry R&;amp;D collaboration is a key driver of participating firms’ technological capability. However, there is still debate on the determinants of a...  相似文献   
102.
103.
Theoretical Foundations of Chemical Engineering - A set of measures to establish the technology for manufacturing highly active sources of γ radiation with an active part from...  相似文献   
104.
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of...  相似文献   
105.
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   
106.
107.
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   
108.
109.

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

  相似文献   
110.
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