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   270280篇
  免费   4470篇
  国内免费   1829篇
电工技术   5508篇
技术理论   5篇
综合类   1168篇
化学工业   43769篇
金属工艺   11212篇
机械仪表   7983篇
建筑科学   6905篇
矿业工程   1714篇
能源动力   5828篇
轻工业   26455篇
水利工程   2941篇
石油天然气   6020篇
武器工业   244篇
无线电   28551篇
一般工业技术   50792篇
冶金工业   49860篇
原子能技术   5682篇
自动化技术   21942篇
  2021年   2590篇
  2019年   2221篇
  2018年   3510篇
  2017年   3462篇
  2016年   3822篇
  2015年   2911篇
  2014年   4716篇
  2013年   11797篇
  2012年   7966篇
  2011年   10535篇
  2010年   8441篇
  2009年   8962篇
  2008年   9819篇
  2007年   9911篇
  2006年   8699篇
  2005年   7658篇
  2004年   6878篇
  2003年   6414篇
  2002年   6425篇
  2001年   6497篇
  2000年   6100篇
  1999年   6040篇
  1998年   13545篇
  1997年   10021篇
  1996年   7623篇
  1995年   5808篇
  1994年   5326篇
  1993年   5197篇
  1992年   4056篇
  1991年   3840篇
  1990年   3933篇
  1989年   3891篇
  1988年   3640篇
  1987年   3106篇
  1986年   3127篇
  1985年   3510篇
  1984年   3434篇
  1983年   3169篇
  1982年   2771篇
  1981年   2978篇
  1980年   2728篇
  1979年   2920篇
  1978年   2835篇
  1977年   2974篇
  1976年   3904篇
  1975年   2518篇
  1974年   2363篇
  1973年   2381篇
  1972年   2023篇
  1971年   1828篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989.  相似文献   
42.
Intense irradiation (25–40 A/cm2) at intermediate energy (400 keV) has been found to cause “metallisation” of tungsten oxide and titanium niobate crystal surfaces. The possible mechanisms and the likely consequences for high-resolution imaging of clean oxide surfaces are briefly discussed.  相似文献   
43.
44.
We consider three types of near-boundary elements: curvilinear quadrangles and families of arcs and points, and their application to a two-dimensional problem of the static theory of elasticity with boundary conditions in displacements. The comparison of the theoretical and numerical aspects of the obtained solutions is performed. It is shown that the accuracy of evaluation of the components of the vector of displacements increases in the following cases: in the case of complete quantization of the near-boundary region (but not in the case of its partial quantization or quantization with overlapping), in the case where the numbers of arcs and points increase, and in the case of simultaneous application of different types of near-boundary elements (specifically, quadrangles and families of arcs).  相似文献   
45.
Poiseuille, known for his law of fluid flow, which is the analog of Ohm's law, introduced the units (mmHg) by which we measure blood pressure by using the mercury manometer, which he described in his medical school thesis in 1828. For 50 years, mean blood pressure was all that could be measured because of the long response time of the mercury manometer. It is true that the height of the mercury column displayed pulsatile oscillations, but their amplitude was much less than that of pulse pressure. It is interesting to note that the slowly responding mercury manometer was made to display first systolic then diastolic pressure by means of an ingenious device that contained two oppositely directed check valves. It took from 1828 to 1903 for high-fidelity graphic recordings of blood pressure to appear in which systolic and diastolic pressures were believable. However, systolic and diastolic pressures were measurable since 1878 when Golz and Gaule created their ingenious valved device that permitted use of the slowly responding mercury manometer to display these pressures accurately  相似文献   
46.
巴西的一个重要电力公司COPEL最近开发了一个水电站高级控制系统,这是在电力部门经受重大变革时期,提高水电竞争力的里程碑。  相似文献   
47.
48.
In temperate seas such as the North Sea harmful (toxic) algal blooms will probably increase as a result of climate change. This conclusion was reached after investigating the projected effect of climate change for the year 2100 in Dutch coastal waters (4 degrees C temperature rise and increased water column stratification) on the growth rates of six harmful and two non-harmful phytoplankton species. Micro algae form the basis of the marine food chain. However, toxin-producing species may seriously disrupt the food web and lead to fish kills and human intoxication. Two species with estimated doubled growth rates in 2100, F. japonica and C. antiqua, entered Europe via ship's ballast water or shellfish imports. This stresses the need to legally regulate such invasion routes in order to prevent the import of novel species. Future toxic phytoplankton blooms may further devaluate ecosystem deliverables such as fish production or recreational use. This devaluation can be estimated by monetary value assessments that are needed in cost-benefit analyses for policy guidance. The lack of understanding of future climate, ecosystem functioning and its response to climate change calls for a scientific effort to improve our knowledge on present day coastal ecosystem functioning and its resilience.  相似文献   
49.
50.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability.  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