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   74974篇
  免费   717篇
  国内免费   689篇
电工技术   1455篇
综合类   47篇
化学工业   11215篇
金属工艺   3447篇
机械仪表   2643篇
建筑科学   1647篇
矿业工程   504篇
能源动力   1853篇
轻工业   6397篇
水利工程   846篇
石油天然气   2303篇
武器工业   41篇
无线电   7218篇
一般工业技术   16459篇
冶金工业   12461篇
原子能技术   2630篇
自动化技术   5214篇
  2022年   577篇
  2021年   909篇
  2020年   703篇
  2019年   782篇
  2018年   1557篇
  2017年   1565篇
  2016年   1766篇
  2015年   949篇
  2014年   1559篇
  2013年   3568篇
  2012年   2363篇
  2011年   2826篇
  2010年   2380篇
  2009年   2644篇
  2008年   2621篇
  2007年   2557篇
  2006年   2185篇
  2005年   1916篇
  2004年   1840篇
  2003年   1789篇
  2002年   1706篇
  2001年   1681篇
  2000年   1684篇
  1999年   1565篇
  1998年   3698篇
  1997年   2606篇
  1996年   1942篇
  1995年   1527篇
  1994年   1330篇
  1993年   1353篇
  1992年   996篇
  1991年   1051篇
  1990年   1075篇
  1989年   1051篇
  1988年   942篇
  1987年   876篇
  1986年   878篇
  1985年   934篇
  1984年   777篇
  1983年   767篇
  1982年   675篇
  1981年   690篇
  1980年   661篇
  1979年   646篇
  1978年   624篇
  1977年   774篇
  1976年   933篇
  1975年   580篇
  1974年   551篇
  1973年   543篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
The interaction of hydrogen with the zinc-containing electrometallurgical slime of the Severstal’ metallurgical works has been studied. The sequence of transformations in the slime heated to 1100°C in hydrogen or air has been established. The experimental and calculated weight losses coincide. Some of the carbonates are shown to decompose in the temperature range 300–700°C, and most iron and zinc oxides are reduced to a metal. In the temperature range 650–850°C, zinc is almost completely sublimated. At temperatures above 800°C, complex oxides are reduced and calcium and magnesium carbonates and sulfates are likely to decompose. Experimental digital data on the zinc sublimation rate are processed by the least squares method with approximating equations used in thermal analysis. The kinetics of nonisothermal zinc sublimation is comprehensively analyzed using a unique procedure developed for taking into account the background of a peak and the effect of accompanying processes. An equation for the calculation of the zinc sublimation rate under experimental conditions (fluidized bed) is given and tested.  相似文献   
63.
64.
Present-day worldwide water problems require new management tools and sustainable system innovations. At Delft University of Technology research is being carried out into water resources and management development aimed at forming such tools and innovations, focused on Integrated River Basin Management (IRBM). One of the case-studies deals with Dutch water management and technology in the context of European IRBM in the form of the 2000 Water Frame Directive. The Netherlands experience many water problems and European IRBM could bring help by offering a framework for both international cooperation and technological innovations. To work as an adequate management tool European IRBM should be tailored to the Dutch water tradition, which recently culminated in Integrated Water Management. Both approaches are in some respects contradicting. Europe pursues, for example, centralized control; while the Dutch have their strongly water boards based decentralized administration. The tensions between both approaches require mutual adaptation, for which the concept of subsidiarity might offer points of departure. This paper describes the first results of the case-research into Dutch water management and technology in the context of Europe as well as the backgrounds and the set-up of the research as a whole.  相似文献   
65.
In this study, the effects of the phosphonic acid based sequestering agent EDTMPA used in the textile dye baths on colour and organic matter removal by ozone oxidation was experimentally investigated. Procion Navy HEXL dyestuff that has been commonly used for the reactive dyeing of cellulose fibers was selected as the model component. The organic matter oxidation by ozone was determined to obey the pseudo-first order kinetics as they are treated singly or in combination. COD removal rates obtained from pseudo-first order reaction kinetics showed that oxidation of Navy HEXL alone (0.0947 L/min) was faster than that of EDTMPA (0.0171 L/min) and EDTMPA with dye (0.0155 L/min) at pH 3.0. It was also found that reaction rates of single EDTMPA removal and EDTMPA and dye mixture removal increased as the reaction pH was increased from 3.0 to 10.5.  相似文献   
66.
The paper describes a few modifications of the classification tree construction algorithm that have proved to be useful for solving tasks of noise spectra processing with reference to NPP diagnostics. The article was translated by the authors.  相似文献   
67.
A method for measuring the characteristics of tunneling and impact ionization in thin-film electroluminescent emitters is suggested. This method makes it possible to find time dependences of the space-charge layer thickness near the anode and the length of the impact ionization region, to determine more exactly the time dependence of the field in the potential barrier at the cathode interface, the maximum depth of the surface states from which electron tunneling occurs, the minimum thickness of the barrier, and the electron tunneling probability, as well as the impact ionization rate for the deep centers related to structural defects of the phosphor layer.  相似文献   
68.
We introduce functions for relative maximization in a general context: the beta and alpha applications. After a systematic study of different kinds of regularities, we investigate how to approximate certain values of these functions using periodic orbits. We also show that the differential of an alpha application determines the asymptotic behavior of the optimal trajectories.  相似文献   
69.
We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays.  相似文献   
70.
A simple model of flange behavior during cup drawing was used to predict the earing profile of deep-drawn cups. The relationship between yield surface shape and earing tendency was established, with plane stress yielding corresponding to no hold-down pressure on the flange and plane strain corresponding to no thickening. Using the Schmid law, the earing model was applied to the case of a single crystal in cube position and compared to Tucker’s well-known results.[6] For the plane strain case, good agreement was obtained with the experiment; but for plane stress, the predicted profile did not agree with the experimental one. Using the Taylor/ Bishop and Hill (TBH) theory[8,9] and measured crystallite orientation distribution functions (CODF), the model was applied to the case of high-purity aluminum sheet with various cold-rolling reductions (35, 60, 80, and 90 pct). The major experimental trends were again correctly predicted by the plane strain case.  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