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   524995篇
  免费   7674篇
  国内免费   1467篇
电工技术   9563篇
综合类   526篇
化学工业   78723篇
金属工艺   19964篇
机械仪表   15192篇
建筑科学   12682篇
矿业工程   2269篇
能源动力   14536篇
轻工业   47076篇
水利工程   5219篇
石油天然气   9334篇
武器工业   37篇
无线电   59920篇
一般工业技术   101781篇
冶金工业   103581篇
原子能技术   10558篇
自动化技术   43175篇
  2022年   3169篇
  2021年   4900篇
  2020年   3489篇
  2019年   4556篇
  2018年   7811篇
  2017年   7613篇
  2016年   7938篇
  2015年   5565篇
  2014年   9247篇
  2013年   24074篇
  2012年   14639篇
  2011年   20155篇
  2010年   15810篇
  2009年   17705篇
  2008年   18095篇
  2007年   17782篇
  2006年   15509篇
  2005年   14215篇
  2004年   13604篇
  2003年   13400篇
  2002年   12634篇
  2001年   12830篇
  2000年   11867篇
  1999年   12597篇
  1998年   32832篇
  1997年   22905篇
  1996年   17454篇
  1995年   13038篇
  1994年   11289篇
  1993年   10975篇
  1992年   7915篇
  1991年   7420篇
  1990年   7265篇
  1989年   7018篇
  1988年   6472篇
  1987年   5769篇
  1986年   5658篇
  1985年   6266篇
  1984年   5903篇
  1983年   5171篇
  1982年   4900篇
  1981年   4968篇
  1980年   4705篇
  1979年   4613篇
  1978年   4410篇
  1977年   5336篇
  1976年   6976篇
  1975年   3797篇
  1974年   3550篇
  1973年   3665篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The results of theoretical and experimental studies for the kinetics of separating dichlorosilane from a mixture of volatile chlorosilanes and ultrapurifying the dichlorosilane concentrate by batch distillation are reported. A mathematical model of the process is proposed. It is shown that the model and computational algorithm adequately describe both processes. The obtained experimental and theoretical data made it possible to design a concentration and ultrapurification process with a maximal productivity at a specified product purity.  相似文献   
992.
A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics.  相似文献   
993.
This paper presents data relating to the performance of sprinklers and detectors in real office fire situations. For sprinklers, these data are additional to that associated with the standardized testing used to determine the design delivery density and pressure requirements for various occupancy situations, and provide a useful insight into the effect of sprinklers on developing fires with various office situations. The data given in this paper include the times for activation of various types of sprinkler heads (normal and fast response), the efficacy of the systems as far as extinguishment is concerned, estimates of the maximum size of the fires prior to commencement of extinguishment and associated air temperatures at various locations within the office enclosures. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
994.
The capabilities of x-ray spectral instruments for fast analysis of raw materials and glass and ceramics were demonstrated. The range of the content of determinable elements in a sample ranges from 1 ppm to 100%. The measurement time is 10–15 sec.  相似文献   
995.
The saturation capacity of n-alkanes in CHA, AFX and ERI zeolites, that consist of cages separated by windows, decreases with increasing carbon number. The major aim of the present communication is to demonstrate the possibility of separating n-alkane mixtures relying on differences in saturation capacities. To investigate this possibility, Configurational-Bias Monte Carlo simulations for adsorption of C3–nC6, nC4–nC6, and nC5–nC6 mixtures in CHA, AFX and ERI were carried out for equimolar bulk fluid phase. These mixture simulations show that for operation at fluid phase fugacities below about 1 MPa, the adsorbed phase in equilibrium with the bulk vapor phase is predominantly the alkane with the longer chain length, i.e. nC6. However, for operation at pressures in excess of 1 MPa, the adsorbed phase in equilibrium with the bulk liquid phase is richer in the component with the smaller chain length. In some cases, the nC6 is practically excluded from the zeolite.  相似文献   
996.
The recent researches and technological developments of middle and long wavelength infrared HgCdTe photovoltaic detectors are presented. Structure, topology, design and performance of HgCdTe photodiodes, silicon readout electronics, Focal Plane Arrays both staring and time delay and integration types, thermal imagers are discussed. Negative differential conductance, bistability and high frequency oscillations under background infrared radiation in HgCdTe photodiodes are reported.  相似文献   
997.
998.
This article is devoted to work done in 2002–2006 as part of the unified project Reabilitatsiya to rehabilitate radiation hazardous objects and sections of the radioactively contaminated territory of the Russian Science Center Kurchatov Institute. The main objects of the rehabilitation work were old storage sites built for radioactive wastes on the territory of the Institute when military and civilian nuclear technologies were under development. The structural features of the storage sites, including the volumes and characteristics of the wastes stored, are presented. The salient aspects of the disposal sites, taken into account during the rehabilitation work, are discussed. The organization of the rehabilitation operations and the sequence in which they are performed, the special features of the technical design solutions used, the technological methods, and ways for conducting the work are described. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 300–306, May, 2007.  相似文献   
999.
Bestehen ausreichende Anhaltspunkte für die Hochwassergef?hrdung, ist die Gemeinde verpflichtet, sich durch Nachforschungen Gewissheit über das Vorliegen oder Nichtvorliegen eines Hochwasserabflussgebietes gem § 38 Abs 3 WRG zu verschaffen. Liegt ein solches vor, hat sie gem § 12 Abs 1 Z 2 krnt GplG dieses im Fl?chenwidmungsplan ersichtlich zu machen. Erteilt die Gemeinde eine Baubewilligung ohne diese von der Erteilung einer wasserrechtlichen Bewilligung abh?ngig zu machen, haftet sie für die Kosten der Bauführung, die bei gesetzes-konformer Vorgangsweise unterlassen worden w?re.  相似文献   
1000.
We present the results of electric discharge treatment of zeolites for purifying the waste water from the manufacture of polymers. By application of the thermostimulated relaxation method, it has been revealed that in the zeolites, superficial and volumetric charges accumulate. It is shown that the electric discharge effects considerably enhance the efficiency of the adsorptive purification of waste water.  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