全文获取类型
收费全文 | 468814篇 |
免费 | 5722篇 |
国内免费 | 2063篇 |
专业分类
电工技术 | 8855篇 |
技术理论 | 5篇 |
综合类 | 1243篇 |
化学工业 | 75067篇 |
金属工艺 | 23491篇 |
机械仪表 | 16349篇 |
建筑科学 | 10247篇 |
矿业工程 | 4902篇 |
能源动力 | 9050篇 |
轻工业 | 33577篇 |
水利工程 | 6351篇 |
石油天然气 | 16182篇 |
武器工业 | 269篇 |
无线电 | 44821篇 |
一般工业技术 | 102136篇 |
冶金工业 | 73704篇 |
原子能技术 | 14621篇 |
自动化技术 | 35729篇 |
出版年
2021年 | 4883篇 |
2019年 | 4458篇 |
2018年 | 7972篇 |
2017年 | 8234篇 |
2016年 | 8757篇 |
2015年 | 5452篇 |
2014年 | 9055篇 |
2013年 | 20072篇 |
2012年 | 13878篇 |
2011年 | 17734篇 |
2010年 | 14287篇 |
2009年 | 15538篇 |
2008年 | 16390篇 |
2007年 | 16167篇 |
2006年 | 13751篇 |
2005年 | 12049篇 |
2004年 | 11253篇 |
2003年 | 10663篇 |
2002年 | 10619篇 |
2001年 | 10470篇 |
2000年 | 10024篇 |
1999年 | 9464篇 |
1998年 | 18989篇 |
1997年 | 14444篇 |
1996年 | 11015篇 |
1995年 | 8595篇 |
1994年 | 8001篇 |
1993年 | 8028篇 |
1992年 | 6590篇 |
1991年 | 6452篇 |
1990年 | 6594篇 |
1989年 | 6469篇 |
1988年 | 6147篇 |
1987年 | 5651篇 |
1986年 | 5565篇 |
1985年 | 6099篇 |
1984年 | 5937篇 |
1983年 | 5623篇 |
1982年 | 5146篇 |
1981年 | 5320篇 |
1980年 | 5113篇 |
1979年 | 5441篇 |
1978年 | 5552篇 |
1977年 | 5676篇 |
1976年 | 6889篇 |
1975年 | 5058篇 |
1974年 | 4973篇 |
1973年 | 5002篇 |
1972年 | 4400篇 |
1971年 | 4023篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
103.
104.
R.V.R. PandyaF. Mashayek 《International Journal of Heat and Mass Transfer》2002,45(24):4753-4759
In this paper, effects of particles on the subgrid scales of turbulence are properly accounted for during the modeling of subgrid scale stresses in the large-eddy simulation (LES) of fluid phase. In doing so, we propose closed filtered kinetic equations for phase space density of the particle. The various moments of these equations give the `fluid' equations which can be considered as the LES equations for the particle phase. The influence of subgrid scales motion on the particles is included in these `fluid' equations. 相似文献
105.
106.
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
107.
L A Geddes 《IEEE engineering in medicine and biology magazine》2002,21(3):102-103
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
108.
Validity on the well-known Onsager reciprocal relations L 12=L 21 is verified in the kinetic theory of gases taking into account mass and heat transfer near the surface. Using an analytical solution to the ellipsoidal statistical equation (providing for the true Prandtl number), it is demonstrated that the Onsager relations are obeyed, at least to within exponential corrections of the type exp(−1/Kn) in the Knudsen number. 相似文献
109.
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
110.