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   206095篇
  免费   2214篇
  国内免费   565篇
电工技术   3510篇
综合类   141篇
化学工业   31821篇
金属工艺   10265篇
机械仪表   7010篇
建筑科学   3995篇
矿业工程   2161篇
能源动力   4631篇
轻工业   12876篇
水利工程   2920篇
石油天然气   7726篇
武器工业   22篇
无线电   21498篇
一般工业技术   45174篇
冶金工业   34383篇
原子能技术   6620篇
自动化技术   14121篇
  2021年   2052篇
  2019年   1999篇
  2018年   3678篇
  2017年   3716篇
  2016年   3998篇
  2015年   2232篇
  2014年   3781篇
  2013年   8737篇
  2012年   5677篇
  2011年   7213篇
  2010年   5854篇
  2009年   6486篇
  2008年   6609篇
  2007年   6491篇
  2006年   5569篇
  2005年   5116篇
  2004年   4629篇
  2003年   4554篇
  2002年   4366篇
  2001年   4472篇
  2000年   4184篇
  1999年   4197篇
  1998年   10184篇
  1997年   7181篇
  1996年   5501篇
  1995年   4131篇
  1994年   3598篇
  1993年   3838篇
  1992年   2983篇
  1991年   2995篇
  1990年   2892篇
  1989年   2852篇
  1988年   2865篇
  1987年   2509篇
  1986年   2569篇
  1985年   2854篇
  1984年   2688篇
  1983年   2554篇
  1982年   2300篇
  1981年   2269篇
  1980年   2345篇
  1979年   2359篇
  1978年   2382篇
  1977年   2487篇
  1976年   2876篇
  1975年   2188篇
  1974年   2068篇
  1973年   2166篇
  1972年   1940篇
  1971年   1756篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
A new equation is derived for the rotational oscillations of a deep massive foundation flexibly restrained in the ground. An error in the corresponding equation published in the literature is indicated. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 7–8, November–December, 1996.  相似文献   
82.
Cellulose diacetate and triacetate films 6–55 µm thick with a total porosity of 0.8–2% were prepared by pouring a solution on an immobile surface and by calendering. Sorption of H2S and CO2 gases and acetone vapors on these films was investigated in static and dynamic conditions. It was shown that films 6–10 µm thick prepared by calendering should be used for purification of air from H2S and CO2 and films 15–20 µm thick prepared by pouring should be used for removal of acetone vapors.Engels Institute of Technology, Saratov State University. Translated from Khimicheskie Volokna, No. 6, pp. 44–46, November–December, 1995.  相似文献   
83.
Known examples of the positive influence of electrohydroimpulse treatment on the quality of weld joints of various steels, particularly including an increase in their long-term and cyclic strength and also corrosion resistance, are analyzed. It is shown that in this case there is a reduction in residual macro- and micro-stresses and also a change in the parameters of the dislocation structure of the joint metal in the direction of stabilization of it.Translated from Problemy Prochnosti, No. 4, pp. 119–123, April, 1996.  相似文献   
84.
85.
Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis.  相似文献   
86.
The authors have fabricated 1.3-μm InAsP-InP separate-confinement-heterostructure (SCH) strained-layer double-quantum-well (SL-DQW) laser diodes (LDs) by metalorganic chemical vapor deposition (MOCVD). A low threshold current density of 410 A/cm 2 was obtained. The CW threshold current was as low as 1.8 mA at 20°C, and maximum CW operating temperature of 120°C was obtained. These characteristics are almost the same as those of well-designed GaInAsP-InP SL-QW LDs. Further improvement of the characteristics of InAsP-InP LDs is expected by optimizing the device structure  相似文献   
87.
A low threshold current density of ~100 A/cm2 has been obtained at 1.55 μm using a graded-index separate-confinement-heterostructure strained InGaAsP single-quantum-well laser. The design of the laser structure is based on results calculated from the viewpoint of effective carrier injection into the well  相似文献   
88.
We present the performance of a high-speed gateable vacuum image pipeline, which permits individual images to be delayed and selected from continuous non-repetitive image stream. This device is composed of a vacuum tube equipped with a photocathode at one end, a phosphor screen at the other end, and a system of metal grids in between. Photoelectrons produced by the images focused on the photocathode, are guided by a uniform magnetic field, parallel to the tube axis. By changing the grid potentials, the drift time of the photoelectrons inside the tube can be varied from 0.35 to 1.5 μs. An image can then be selected by an external trigger with a time resolution in the range of 4–30 ns, depending on the delay time. The selected photoelectrons are finally accelerated onto the phosphor screen, set at 10 kV, where they reproduce the desired image. With a magnetic field of 0.1 T, a spatial resolution of 33 lp/mm was obtained. The high spatial and time resolution make this device an interesting tool for high-energy physics and astrophysics experiments, and for high-speed photography.  相似文献   
89.
90.
The article describes the experience of implementing patient-focused care from a physician's perspective. Pitfalls that guarantee failure are presented, many of which are avoidable with early participation by all parties involved: administrators, nursing staff, physicians, and patients. Contamination of the process with downsizing needs, lack of support for staff in dealing with necessary change, loss of administrative commitment, and withholding of appropriated funds are among the key errors to be avoided.  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