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   329607篇
  免费   27508篇
  国内免费   16001篇
电工技术   20737篇
技术理论   51篇
综合类   41541篇
化学工业   40966篇
金属工艺   15938篇
机械仪表   18316篇
建筑科学   43801篇
矿业工程   16655篇
能源动力   16439篇
轻工业   20436篇
水利工程   14896篇
石油天然气   14089篇
武器工业   3226篇
无线电   20073篇
一般工业技术   26460篇
冶金工业   19111篇
原子能技术   3952篇
自动化技术   36429篇
  2024年   1103篇
  2023年   3446篇
  2022年   6676篇
  2021年   7956篇
  2020年   8462篇
  2019年   7159篇
  2018年   6734篇
  2017年   8168篇
  2016年   9562篇
  2015年   10403篇
  2014年   18829篇
  2013年   17956篇
  2012年   22237篇
  2011年   23548篇
  2010年   18414篇
  2009年   19116篇
  2008年   17373篇
  2007年   22966篇
  2006年   21539篇
  2005年   18731篇
  2004年   15971篇
  2003年   14325篇
  2002年   12065篇
  2001年   10157篇
  2000年   8560篇
  1999年   6993篇
  1998年   5381篇
  1997年   4771篇
  1996年   4267篇
  1995年   3631篇
  1994年   3167篇
  1993年   2419篇
  1992年   2127篇
  1991年   1567篇
  1990年   1358篇
  1989年   1211篇
  1988年   949篇
  1987年   657篇
  1986年   498篇
  1985年   409篇
  1984年   409篇
  1983年   304篇
  1982年   281篇
  1981年   184篇
  1980年   153篇
  1979年   118篇
  1978年   67篇
  1977年   74篇
  1975年   57篇
  1959年   72篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
We present a method that is useful in the estimate and assessment of heat capacity data. The approach is based on an analysis of the logarithmic average of the phonon frequencies. In this quantity, that may be easily derived from experimental data on the vibrational entropy, the influence of atomic masses can be exactly accounted for even in polyatomic solids. Our method is applied to Li2O, Na2O, K2O, Rb2O, and Cs2O. In particular, literature data for K2O are critically examined.  相似文献   
52.
论述复合脱氧剂的一般化学特性,并以碳化硅和硅铝铁两种复合脱氧剂为例,讨论其对改善钢的质量,进行纯净钢生产的影响。  相似文献   
53.
Preparation of photoreactive Langmuir-Blodgett (LB) films was carried out using polymers/oligomers prepared from long-chain dialkyl esters of di-and tetra-olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y-type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo-reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings.  相似文献   
54.
The Error-in-Variables Model (EVM) applies to a large class of problems in parameter estimation in which there is error in all the variables. This property makes it of more general applicability than the widely used technique of ordinary Least Squares. While there is a voluminous literature on EVM there is nothing on a general method for designing experiments when EVM applies. In this paper we present an extension of the concept of D-optimality to provide such a general method. It is illustrated by applying it to the estimation of copolymer reactivity ratios and to fitting an ellipse.  相似文献   
55.
淀粉液化液灭酶方法的研究   总被引:5,自引:1,他引:4  
某些情况下淀粉液化液需要严格控制液化的程度 ,因此需要及时终止残余淀粉酶的活性。实验用降低液化液 pH值、升高温度、以及两者并用等 3种方法结束液化反应过程 ,实验结果可作为工业生产过程参考。  相似文献   
56.
门式脚手架在已建高层建筑外装修中的应用   总被引:1,自引:0,他引:1  
介绍门式脚手架在已建高层建筑外排栅中的整体搭设和应用实例。  相似文献   
57.
化工企业环境因素的评价   总被引:1,自引:0,他引:1  
牛锋 《安徽化工》2003,29(5):36-38
化工企业环境因素评价是建立环境管理体系的核心任务,化工企业生产过程的特点决定了其环境因素数量多、环境影响大、识别评价难、控制难度大。本文介绍了化工企业环境因素评价的技术方法和过程,可以为提高环境因素评价的科学性、客观性和充分性提供参考。  相似文献   
58.
Multilayer calculations by conventional matrix methods for dielectricum/noble metal/dielectricum systems on glass have been performed. The aim has been to maximize the integrated parameters for solar transmission, Tsol, and transmission of visible light, Teye We have found that Ag is superior for maximizing the transmittance over the narrow visible wavelength range owing to the low internal absorptance. When solar energy transmission is considered multilayers based on Au are the best choice for metal film thicknesses above 15 nm. For thinner films, Ag is still to be preferred.  相似文献   
59.
In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I1 and I2 whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I1 and I2 with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007  相似文献   
60.
We analyze the wear resistance of plasma coatings for a constant work of friction. The dependences of the wear resistance of the coatings are obtained for a broad range of loading conditions. It is shown that the minimum sensitivity to loading conditions is exhibited by the molybdenum coatings. It is also established that the wear resistance of the coatings decreases as the amplitude of displacements increases and the cyclic frequency of the tests decreases due to the intensification of fatigue processes on the surfaces. The comparative characteristics of coatings are presented. __________ Translated from Problemy Prochnosti, No. 5, pp. 94–100, September–October, 2007.  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