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   242664篇
  免费   2734篇
  国内免费   430篇
电工技术   4337篇
综合类   259篇
化学工业   39667篇
金属工艺   9395篇
机械仪表   7415篇
建筑科学   5504篇
矿业工程   1393篇
能源动力   5201篇
轻工业   24933篇
水利工程   2483篇
石油天然气   5095篇
武器工业   32篇
无线电   25174篇
一般工业技术   45116篇
冶金工业   45538篇
原子能技术   5957篇
自动化技术   18329篇
  2021年   2177篇
  2019年   2066篇
  2018年   3534篇
  2017年   3458篇
  2016年   3751篇
  2015年   2298篇
  2014年   3958篇
  2013年   10269篇
  2012年   6269篇
  2011年   8448篇
  2010年   6652篇
  2009年   7299篇
  2008年   7671篇
  2007年   7796篇
  2006年   6946篇
  2005年   6091篇
  2004年   5859篇
  2003年   5632篇
  2002年   5698篇
  2001年   5576篇
  2000年   5396篇
  1999年   5309篇
  1998年   12578篇
  1997年   8904篇
  1996年   6863篇
  1995年   5341篇
  1994年   4739篇
  1993年   4628篇
  1992年   3669篇
  1991年   3389篇
  1990年   3595篇
  1989年   3474篇
  1988年   3305篇
  1987年   2898篇
  1986年   2932篇
  1985年   3375篇
  1984年   3220篇
  1983年   2893篇
  1982年   2740篇
  1981年   2823篇
  1980年   2721篇
  1979年   2624篇
  1978年   2685篇
  1977年   2948篇
  1976年   3805篇
  1975年   2368篇
  1974年   2242篇
  1973年   2377篇
  1972年   1972篇
  1971年   1859篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
The simple method of polarographical testing of the peripheral blood serum is recommended as a part of the complex cancer diagnosis for the evaluation of the effectivity of cancer treatment and for the mass preventive examination. This method modified by I. A. Pelishenko (POISK-test) has permitted detecting a protein substance in the serum of cancer patients as well as in the serum both of the rats bearing Pliss sarcoma and in the serum of the irradiated dogs. It was proved that this protein indicates the presence of malignancy and represents polarographically active fraction of the alpha 1-unstable glycoprotein. This substance was designated as "Informative Pelishenko Protein" (IPP), and may be revealed by the polarographic indicator (IPM-01) made in Leningrad.  相似文献   
995.
Summary The MATMOD-4V-DISTORTION model has been derived [1] with the intent of improving the MATMOD-4V model by adding the capability to predict distortions of small strain offset yield surfaces. This model is compared against a variety of experimental data to verify its behavior. Model simulations are compared with experimental data for proportional and nonproportional prestress histories and the effect of yield definition is also investigated. Finally, the same model which predicts a flattening of the yield surface in space is used to predict a rotation of the yield surface in 1-2 coordinates.With 9 Figures  相似文献   
996.
Summary By resorting to both microscopic and macroscopic considerations, including the concept of single slip, dislocation stress, and a scale invariance argument we show that the notion and formalism of the relative spin introduced in Part I reduces to that of plastic spin previously recognized in the literature. The central feature of this reduction is the possibility of obtaining physically based constitutive equations for the plastic spin along with appropriate evolution equations for the dislocation or back stress. When these constitutive models are incorporated in the analysis of existing data on tension-torsion tests, we find satisfactory agreement between theory and experiment. In particular, a theoretical interpretation of the torsionally induced axial strain, as observed for example by Swift, Bailey et al., Hart and Chang, and others, is provided. Moreover, the recent experiments of Montheillet et al. on torsionally induced axial stresses are discussed in the light of the presently proposed models of large inelastic deformation inelasticity accounting for anisotropy and texture effects.

With 12 Figures  相似文献   
997.
Risk-taking behavior by drivers is put within the context of a general model of utility maximization by speed choice. It is shown that so-called "risk homeostasis" is possible only under very restrictive conditions. Under more general conditions, risk compensation can occur; that is, the safety effects expected from engineering measures will be discounted to a considerable degree by shifts in behavior.  相似文献   
998.
A simplified approach, based on the concept of an overall heat loss coefficient, is described for the estimation of time-variant temperature profiles. The computation of the loss coefficient from experimental temperature maxima under programmed power input is also discussed.  相似文献   
999.
1.  The installation of a conical transitional segment between a tower (shaft)-type water intake-outlet and penstock affects a significant reduction in head loss in the pump mode, but has virtually no effect on the magnitude of the latter in the pump mode.
2.  The existence of a conical transitional element in the pump mode appreciably lowers the discharge velocities of the flow and increases the effective height of the water-passing openings by 1.5–1.7 times when the height of the intake openings h0.5dp.
3.  The head losses in the intake-outlet decrease in the pump mode of operation with increasing degree of expansion of the transitional diffusor segment.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 21–23, November, 1992.  相似文献   
1000.
Blaco CE 《Textile rental》1992,75(6):24-6, 28, 30 passim
Get ready to update and improve your company's safety program. On pages 24-38, you'll find a comprehensive guide to safe industry practices to enhance your operation and help you stay in compliance with OSHA regulations such as the General Duty Clause and the Right-to-Know law. Achieving a safe, healthy, productive, and profitable business doesn't happen by accident. It takes upper-management commitment to improve equipment, procedures, and employee training. Managers have a personal and a legal responsibility for employees' safety on the job. Don't delay safety improvements!  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