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   287578篇
  免费   3065篇
  国内免费   817篇
电工技术   5030篇
综合类   162篇
化学工业   45403篇
金属工艺   11895篇
机械仪表   8604篇
建筑科学   6846篇
矿业工程   1835篇
能源动力   6734篇
轻工业   25905篇
水利工程   3190篇
石油天然气   7087篇
武器工业   16篇
无线电   31448篇
一般工业技术   56929篇
冶金工业   51361篇
原子能技术   7532篇
自动化技术   21483篇
  2021年   2098篇
  2018年   3672篇
  2017年   3622篇
  2016年   3903篇
  2015年   2465篇
  2014年   4230篇
  2013年   12019篇
  2012年   6826篇
  2011年   9212篇
  2010年   7565篇
  2009年   8642篇
  2008年   8929篇
  2007年   8813篇
  2006年   7827篇
  2005年   7309篇
  2004年   6800篇
  2003年   6553篇
  2002年   6627篇
  2001年   6497篇
  2000年   6176篇
  1999年   6229篇
  1998年   14749篇
  1997年   11029篇
  1996年   8566篇
  1995年   6523篇
  1994年   5914篇
  1993年   5787篇
  1992年   4479篇
  1991年   4440篇
  1990年   4284篇
  1989年   4301篇
  1988年   4255篇
  1987年   3598篇
  1986年   3595篇
  1985年   4161篇
  1984年   3965篇
  1983年   3620篇
  1982年   3422篇
  1981年   3558篇
  1980年   3422篇
  1979年   3365篇
  1978年   3445篇
  1977年   3923篇
  1976年   5037篇
  1975年   3158篇
  1974年   3007篇
  1973年   3024篇
  1972年   2651篇
  1971年   2473篇
  1970年   2104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
963.
964.
The density of molten Pb–Bi eutectic is measured by the pycnometer method in a temperature range of 410–726 K. The confidence of error of measurement, made up by the systematic and random components, does not exceed 0.1%. The experimental results are compared with the experimental data on the density of a liquid lead–bismuth alloy of eutectic composition available in the literature.  相似文献   
965.
This paper discusses the need for interface management within construction, with particular reference to building facade interfaces. It categorizes the three different types of interface management—physical, contractual, and organizational. The implication of interface management in construction contracting is discussed; it is explained how the U.K. procurement trends have changed, affecting the interface management within projects. U.K. cladding procurement is very fragmented, and the paper maps the development of a typical cladding system showing the complexities of interface management. Finally, the paper discusses CladdISS, a U.K. government funded research project to develop a standardized strategy for the design and management of window and cladding interfaces. It explains the principles of CladdISS with reference to process maps, action plans, management strategy, bibliography, advice on standards, materials, maintenance, joints, movement, and tolerances. This will enable strategies to be developed to avoid the endemic interface problems occurring on-site. It will also guide the management of the interfaces throughout the project.  相似文献   
966.
The method of reverberation ray matrix is applied to analyze the dynamic behavior of structural members in trusses with pinned joints subjected to suddenly applied force. The results are compared with those in planar trusses with rigid joints. Detailed calculations are made with two types of trusses, a small laboratory model made of slender aluminum bars, and a hypothetical real size Pratt truss made of structural steel. It is found that the maximum dynamic bending strains in the members of both types of trusses are very large, comparable with the dynamic axial strains in the same member. The magnitudes of bending strains in the pinned truss differs little from those in the truss with rigid joints for both types of trusses. Such a large dynamic bending strain in a structure member, which is contradictory to the static behavior of the same truss, could be caused by the inertial force of the mass in structural members of the truss.  相似文献   
967.
Chernorukov  N. G.  Kortikov  V. E. 《Radiochemistry》2003,45(5):469-474
Previously unknown alkaline-earth metal uranogermanates of the general formula MII[HGeUO6]2·nH2O (MII = Mg, Ca) were prepared in the form of higher and intermediate hydrates and anhydrous compounds. The compounds were studied by X-ray diffraction, IR spectroscopy, and thermal analysis.  相似文献   
968.
969.
The deformation behavior of pure recrystallized molybdenum under cyclic and static loads was investigated in the temperature range between 30°C and 10O°C, for stress amplitudes between 100 MPa and 250 MPa and for static loads up to 200 MPa. The results show that in spite of the low test temperatures and stress levels the Mo material exhibits considerable plastic strains which depend sensitively on frequenez and small changes in temperature.The activation energy deduced for the static and dynamic deformation is less than 0.98 eV which indicates thermally activated processes, to be explained by a dislocation kink model as described in the literature. The low-temperature fatigue behavior appears strongly influenced by creep-fatigue interaction phenomena.  相似文献   
970.
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