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   721939篇
  免费   12000篇
  国内免费   2332篇
电工技术   13172篇
综合类   738篇
化学工业   109283篇
金属工艺   28340篇
机械仪表   20534篇
建筑科学   18338篇
矿业工程   2713篇
能源动力   19387篇
轻工业   67178篇
水利工程   6712篇
石油天然气   10343篇
武器工业   44篇
无线电   82609篇
一般工业技术   136828篇
冶金工业   144721篇
原子能技术   13217篇
自动化技术   62114篇
  2021年   6504篇
  2020年   4809篇
  2019年   6017篇
  2018年   10317篇
  2017年   10099篇
  2016年   10669篇
  2015年   7563篇
  2014年   12192篇
  2013年   33698篇
  2012年   19737篇
  2011年   26660篇
  2010年   21117篇
  2009年   23304篇
  2008年   24359篇
  2007年   23953篇
  2006年   21061篇
  2005年   19263篇
  2004年   18443篇
  2003年   18162篇
  2002年   17468篇
  2001年   17302篇
  2000年   16048篇
  1999年   17238篇
  1998年   45352篇
  1997年   31677篇
  1996年   24268篇
  1995年   18106篇
  1994年   15753篇
  1993年   15371篇
  1992年   10935篇
  1991年   10501篇
  1990年   9981篇
  1989年   9717篇
  1988年   9190篇
  1987年   8004篇
  1986年   7967篇
  1985年   9022篇
  1984年   8402篇
  1983年   7408篇
  1982年   7007篇
  1981年   7131篇
  1980年   6733篇
  1979年   6468篇
  1978年   6236篇
  1977年   7738篇
  1976年   10643篇
  1975年   5433篇
  1974年   5076篇
  1973年   5179篇
  1972年   4259篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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   
92.
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   
93.
94.
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   
95.
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   
96.
97.
Programming and Computer Software - Image segmentation using a hierarchical sequence of piecewise constant approximations that minimally differ from the original image in terms of the total squared...  相似文献   
98.
99.
100.
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