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   172105篇
  免费   12406篇
  国内免费   6396篇
电工技术   9177篇
技术理论   9篇
综合类   9273篇
化学工业   27767篇
金属工艺   10315篇
机械仪表   10380篇
建筑科学   10202篇
矿业工程   4201篇
能源动力   3806篇
轻工业   10052篇
水利工程   3289篇
石油天然气   9678篇
武器工业   1141篇
无线电   18239篇
一般工业技术   27100篇
冶金工业   11305篇
原子能技术   4899篇
自动化技术   20074篇
  2024年   720篇
  2023年   2323篇
  2022年   4651篇
  2021年   6258篇
  2020年   4738篇
  2019年   4048篇
  2018年   5168篇
  2017年   5626篇
  2016年   5202篇
  2015年   5782篇
  2014年   7561篇
  2013年   9246篇
  2012年   9983篇
  2011年   10757篇
  2010年   9221篇
  2009年   9094篇
  2008年   8989篇
  2007年   8515篇
  2006年   7880篇
  2005年   6752篇
  2004年   5067篇
  2003年   4871篇
  2002年   4853篇
  2001年   4435篇
  2000年   3858篇
  1999年   3331篇
  1998年   2623篇
  1997年   2209篇
  1996年   1972篇
  1995年   1733篇
  1994年   1465篇
  1993年   1242篇
  1992年   1216篇
  1991年   1074篇
  1990年   1089篇
  1989年   1009篇
  1988年   896篇
  1987年   841篇
  1986年   763篇
  1985年   715篇
  1984年   701篇
  1981年   668篇
  1979年   736篇
  1978年   777篇
  1977年   739篇
  1976年   755篇
  1975年   713篇
  1974年   719篇
  1973年   723篇
  1972年   705篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We develop a theoretical model of the development of a temperature jump across the boundary between phases during a phase transition in pure liquids.Notation G1 mass flux of molecules of the liquid into the liquid - G2 mass flux of molecules of the liquid into the vapor - Gv mass flux of vapor molecules - T1 vapor temperature near the liquid surface - T2 temperature of the liquid - Tv vapor temperature - R universal gas constant - cp, cv specific heats - r heat of vaporization - q heat flux density - K ratio cp/cv - parameter of the phase transition - F0 area of the interface - P1 pressure of the liquid - P2 phase transition pressure - Pv vapor pressure Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 793–797, May, 1988.  相似文献   
992.
Experimental data are presented for the local heat liberation coefficient for flow of a liquid film on a smooth horizontal tube, permitting refinement of the concept of the heat exchange mechanism.Notation , , ,a kinematic viscosity, thermal conductivity, density, and thermal diffusivity of liquid - liquid film thickness - irrigation density Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 736–739, May, 1988.  相似文献   
993.
1.  The combined theoretical and experimental investigation of the thermal and stress state of the nozzle vane of a gas turbine confirmed the possibility of using the newly devised experimental strain gauges in the range of working temperatures 293–973°K.
2.  In modeling the pin system of the outlet channel by thin continuous baffles we obtained satisfactory agreement of calculation and experiment at all points of measurement uniformly distributed over the surface of the vane.
A. A. Blagonravov Institute of Engineering Science, Academy of Sciences of the USSR. F. É. Dzerzhinskii All-Union Institute of Heat Engineering, Moscow. Translated from Problemy Prochnosti, No. 4, pp. 8–11, April, 1988.  相似文献   
994.
This paper describes the synthesis and cation-radical polymerization of 1,5-bis(1-naphthoxy)-3-oxapentane. This monomer contains a flexible diethylene oxide unit between two 1-naphthalene rings. The FT-IR analysis of the resulted polymer indicates that it contains 1,4-disubstituted naphthalene structural units, i.e. 4,4-disubstituted-1,1-binaphthalene units. The polymer is crystalline with a melting point of 236 °C.Part IX: V. Percec and J. H. Wang: J. Mater. Chem., in press  相似文献   
995.
1.  Deformation of pseudo--alloy in the upper part of the (+)-region (from tm to tp.t –50°C) which provides occurrence of dynamic recrystallization independent of the deformation scheme leads to preparation of a multicomponent texture. Here the structure consists of recrystallized -grains with a lamellar intergranular structure and individual round -grains with toothed boundaries. This structure provides quasi-anisotropy of properties in the plane of the sheet, and also high and isotropic values for corrosion-mechanical strength.
2.  Deformation in the lower part of the (+)-region (from tp.t –100°C to tp.t –150°C), which does not provide occurrence of dynamic recrystallization processes, leads independent of the deformation scheme to preparation either of a predominantly prismatic texture, or a texture of the inclined basal type with a structure consisting mainly of -phase plates. In alloy with this texture and a predominantly prismatic texture marked anisotropy of strength properties and a reduction in low-cycle fatigue endurance in a corrosive medium is observed for transverse specimens.
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 35–39, January, 1992.  相似文献   
996.
1.  The installation of a conical transitional segment between a tower (shaft)-type water intake-outlet and penstock affects a significant reduction in head loss in the pump mode, but has virtually no effect on the magnitude of the latter in the pump mode.
2.  The existence of a conical transitional element in the pump mode appreciably lowers the discharge velocities of the flow and increases the effective height of the water-passing openings by 1.5–1.7 times when the height of the intake openings h0.5dp.
3.  The head losses in the intake-outlet decrease in the pump mode of operation with increasing degree of expansion of the transitional diffusor segment.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 21–23, November, 1992.  相似文献   
997.
提出并研制成一种新型硅三端负阻器件。该器件由一n沟耗尽型MOS管、一横向pnp双极晶体管和一个电阻集成而得。它具有“双负阻”特性和正阻区阻值易于控制等特点。由理论计算出的器件I_c—V_(CB)特性和负阻参数与实验结果符合良好。  相似文献   
998.
Results are presented for tests on 27 foundations in punched (tamped-out) trenches (including some tested under repeated loading and when a long period had elapsed after their construction), which showed high technical-economic indices. Experience with their operation permits recommending wider use of this foundation construction method.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 18–21, March–April, 1992.  相似文献   
999.
曝光数据流优化问题的蒙特卡罗算法   总被引:1,自引:0,他引:1  
袁为民  余学鸣 《微电子学》1992,22(1):23-26,13
集成工艺中控制图形发生器产生掩模图形的数据流文件的数据排列顺序优化,是一个其结点数可达数千个之多的大规模旅行商问题(从镜头架的位置,即每个矩形的矩心为结点),常规算法早已不适用。本文采用多阶段蒙特卡罗算法并加以改进,补充了“分层优化模式”,邻接结点的预合并和在各个阶段末提取共同子路径并删去相关结点等一系列逐步缩小问题规模的措施,形成了一个实用的优化算法。相应的软件已成功地应用于薄膜磁头的数据流文件的优化。  相似文献   
1000.
Scientific-Research Construction Institute of Power Engineering. Russian Scientific Center Kurchatov Institute. Special Design Office of Industrial Organization Izhorskii Plant. All-Union Scientific-Research and Design Institute of Power Engineering Scientific-Industrial Organization. Translated from Atomnaya Énergiya, Vol. 73, No. 1, pp. 13–19, July, 1992.  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