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   728773篇
  免费   10597篇
  国内免费   2058篇
电工技术   13154篇
综合类   680篇
化学工业   110836篇
金属工艺   28251篇
机械仪表   21393篇
建筑科学   17849篇
矿业工程   3769篇
能源动力   19253篇
轻工业   64559篇
水利工程   7430篇
石油天然气   13987篇
武器工业   49篇
无线电   81422篇
一般工业技术   142091篇
冶金工业   140557篇
原子能技术   15308篇
自动化技术   60840篇
  2021年   6244篇
  2020年   4626篇
  2019年   5809篇
  2018年   10514篇
  2017年   10314篇
  2016年   10837篇
  2015年   7418篇
  2014年   12041篇
  2013年   32696篇
  2012年   19165篇
  2011年   26366篇
  2010年   20891篇
  2009年   23455篇
  2008年   24017篇
  2007年   23523篇
  2006年   20696篇
  2005年   20398篇
  2004年   18909篇
  2003年   18329篇
  2002年   17219篇
  2001年   17175篇
  2000年   16034篇
  1999年   16766篇
  1998年   42715篇
  1997年   30482篇
  1996年   23441篇
  1995年   17555篇
  1994年   15387篇
  1993年   15070篇
  1992年   11068篇
  1991年   10558篇
  1990年   10262篇
  1989年   10089篇
  1988年   9559篇
  1987年   8411篇
  1986年   8306篇
  1985年   9378篇
  1984年   8825篇
  1983年   7960篇
  1982年   7456篇
  1981年   7680篇
  1980年   7292篇
  1979年   7110篇
  1978年   6999篇
  1977年   8307篇
  1976年   10936篇
  1975年   6210篇
  1974年   5811篇
  1973年   5880篇
  1972年   4978篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Hussien  O. S.  Elamy  M. I. 《Strength of Materials》2020,52(3):470-479
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which...  相似文献   
92.
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...  相似文献   
93.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
94.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models.  相似文献   
95.
96.
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   
97.
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   
98.
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   
99.
100.
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