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   351篇
  免费   7篇
电工技术   17篇
综合类   1篇
化学工业   81篇
金属工艺   10篇
机械仪表   9篇
建筑科学   1篇
能源动力   7篇
轻工业   49篇
水利工程   2篇
无线电   14篇
一般工业技术   97篇
冶金工业   25篇
原子能技术   21篇
自动化技术   24篇
  2022年   8篇
  2019年   3篇
  2018年   3篇
  2017年   5篇
  2016年   8篇
  2015年   6篇
  2014年   9篇
  2013年   15篇
  2012年   14篇
  2011年   17篇
  2010年   22篇
  2009年   20篇
  2008年   27篇
  2007年   12篇
  2006年   6篇
  2005年   7篇
  2004年   11篇
  2003年   9篇
  2002年   9篇
  2001年   8篇
  2000年   5篇
  1999年   6篇
  1998年   20篇
  1997年   8篇
  1996年   11篇
  1995年   3篇
  1994年   4篇
  1993年   6篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1989年   4篇
  1987年   7篇
  1985年   1篇
  1984年   6篇
  1983年   2篇
  1982年   1篇
  1981年   5篇
  1980年   3篇
  1979年   6篇
  1978年   4篇
  1977年   5篇
  1976年   4篇
  1975年   3篇
  1974年   5篇
  1973年   2篇
  1972年   6篇
  1971年   3篇
  1970年   1篇
  1969年   2篇
排序方式: 共有358条查询结果,搜索用时 15 毫秒
31.
Making use of the Ginzburg-Landau free energy, singularities such as disgyrations and vortex lines and stable textures in the planar (or two-dimensional) texture are studied. Here both % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaaieqaceWFSbGbaK% aaaaa!3883!\[{\hat l}\] and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaaieqaceWFKbGbaK% aaaaa!387B!\[{\hat d}\] vectors, characterizing the texture in 3He-A, are assumed parallel to each other and lie always in a plane. The dynamics of disgyrations is also considered.Work supported by the National Science Foundation under grant number DMR76-21032.  相似文献   
32.
Directional interpolation plays an important role in robust control, system realization and model reduction. Several solutions to various directional interpolation problems have been proposed. In this paper, we consider the directional interpolation problem in a general setting and present a statespace based new approach to solving the problem. The solution is simple, and its exposition is as self‐contained as possible. We describe all the (strictly) bounded real rational matrix functions that satisfy the directional interpolation requirements by means of linear fractional transformation. Moreover, we give a necessary and sufficient condition for the interpolating function to be unique and show that the unique interpolating function is an inner (a co‐inner). The main procedures used to generate the interpolating function consist of standard matrix operations consisting of easy numerical computations, so the present solution is significant from the numerical viewpoint as well as the analytical viewpoint.  相似文献   
33.
34.
Recently, along with the growth in economic development, there has been a dramatic accompanying increase in the amount of sludge and organic waste. The disposal of such is a significant problem. Moreover, there is also an increased in the consumption of electricity along with economic growth. Although new energy development, such as fuel cells, has been promoted to solve the problem of power consumption, there has been little corresponding promotion relating to the disposal of sludge and organic waste. Generally, methane fermentation comprises the primary organic waste fuel used in gasification systems. However, the methane fermentation method takes a long time to obtain the fuel gas, and the quality of the obtained gas is unstable. On the other hand, gasification by molten salt is undesirable because the molten salt in the gasification gas corrodes the piping and turbine blades. Therefore, a gasification system is proposed by which the sludge and organic waste are gasified by molten salt. Moreover, molten carbonate fuel cells (MCFC) are needed to refill the MCFC electrolyte volatilized in the operation. Since the gasification gas is used as an MCFC fuel, MCFC electrolyte can be provided with the fuel gas. This paper elucidates the fundamental characteristics of sludge and organic waste gasification. A crucible filled with the molten salt comprising 62 Li2CO3/38 K2CO3, is installed in the reaction vessel, and can be set to an arbitrary temperature in a gas atmosphere. In this instance, the gasifying agent gas is CO2. Sludge or the rice is supplied as organic waste into the molten salt, and is gasified. The chemical composition of the gasification gas is analyzed by a CO/CO2 meter, a HC meter, and a SOx meter gas chromatography. As a result, although sludge can generate CO and H2 near the chemical equilibrium value, all of the sulfur in the sludge is not fixed in the molten salt, because the sludge floats on the surface of the carbonate by the specific gravity of sludge lighter than the carbonate, and is not completely converted into CO and H2. Moreover, the rice also shows good characteristics as a gasifying agent. Consequently, there is high expectation to using the organic waste as a molten salt gasifying agent. However, this requires lengthening the contact time between the organic waste and the molten salt.  相似文献   
35.
The antioxidant activities of 9H-xanthene-2,7-diols and α-tocopherol were studied during the oxidation of linoleic acid in a homogeneous solution and in an aqueous micelle dispersion. The antioxidant activities of 9H-xanthene-2,7-diols for both systems were 1.0–2.4 times greater relative to α-tocopherol. In addition, the 1,3,4,5,6,8-hexamethylxanthene-2,7-diol showed less cytotoxicity toward human fibroblasts than did 2,6-di-t-butyl-4-methylphenol.  相似文献   
36.
We devised a new physical training program on the basis of anaerobic threshold for rehabilitation in the early phase of acute myocardial infarction. Forty-four patients were divided into two groups, control and training. We measured the left ventricular ejection fraction using nuclear stethoscopy during the treadmill test and calculating radioactive cardiac output. In the training group, anaerobic threshold and exercise time to the anaerobic threshold point were significantly increased, and stroke volume at rest measured by the dye dilution method increased significantly. Radioactive cardiac output during exercise also increased after the exercise therapy. These results indicate that the rehabilitation program consisting of physical training based on the anaerobic threshold is effective.  相似文献   
37.
Tumor necrosis factor-alpha (TNF-alpha) levels were measured in the serum (sTNF-alpha) or bone marrow (BM) biopsies of 43 patients with myelodysplastic syndromes (MDS) who subsequently received therapy with a combination of pentoxifylline and ciprofloxacin (PC) with or without dexamethasone (PCD). All 43 patients received only PC therapy for 12 weeks, after which 18 of 36 nonresponders received PCD. A total of 18 of 43 patients showed a hematologic or cytogenetic response or both. BM TNF-alpha levels were semiquantitatively assessed using immunohistochemistry on a scale of 0-8+ and in the serum using enzyme linked immunoassay. The median TNF-alpha for the entire group was 3.0 in BM and 6.9 pg/ml in the serum, and 14 patients had no detectable levels. Responders had higher BM levels (median 3.5 vs. 2.0) than nonresponders, although this was not statistically significant. During PC therapy, a decline in BM TNF-alpha level was seen in the entire group, which was significant at 2 weeks (p = 0.02), 8 weeks (p = 0.001), and 12 weeks (p = 0.0001). Both responders (p = 0.01) and nonresponders (p = 0.03) had a decline at 8 weeks, but at 12 weeks, only the responders continued to show a significant decline (p = 0.03). We conclude that MDS patients with high BM TNF-alpa levels have a better chance of responding to PCD therapy and that the therapy is quite successful in reducing the TNF-alpha levels in a sustained fashion. Future studies need to be directed at identifying agents that would be more potent suppressors of the proapoptotic cytokines in these patients.  相似文献   
38.
The ultrasonic attenuation of the excitonic state in pure Bi in high magnetic fields is studied theoretically. Use is made of the mean-field approximation to describe the excitonic state in pure Bi in the extreme quantum limit, where the motion of the electron and the hole is limited only in the direction parallel to the magnetic field. The attenuation constant of the longitudinal sound has a broad peak below the excitonic transition temperatureT c and then decreases rapidly as the temperature decreases, which agrees qualitatively with a recent observation by Sakaiet al.  相似文献   
39.
Monotonic and cyclic loading tests on strain rate changes are conducted on — 1Mo steel at 600°C. The examination of the tensile stress-strain response suggests that the viscosity function which characterizes the rate-dependency in the viscosity theory used previously at room temperature should not only depend on the overstress but also on the strain. A new extended viscosity control function is introduced to represent such strain dependency.The material constants of this modified viscoplasticity model are determined at temperatures of 25°C to 600°C and the model is applied to deformation tests on — 1Mo steel carried out under time-varying temperature conditions and other conditions.The extended viscoplasticity theory is shown to reproduce such various experimentally observed stress-strain behavior at elevated temperatures.  相似文献   
40.
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