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   403820篇
  免费   4696篇
  国内免费   1364篇
电工技术   7572篇
综合类   316篇
化学工业   59839篇
金属工艺   16424篇
机械仪表   13488篇
建筑科学   8354篇
矿业工程   2154篇
能源动力   11531篇
轻工业   28475篇
水利工程   4270篇
石油天然气   7915篇
武器工业   17篇
无线电   49251篇
一般工业技术   82990篇
冶金工业   74958篇
原子能技术   9181篇
自动化技术   33145篇
  2022年   2556篇
  2021年   3888篇
  2020年   2947篇
  2019年   3808篇
  2018年   6490篇
  2017年   6485篇
  2016年   6928篇
  2015年   4320篇
  2014年   7143篇
  2013年   20032篇
  2012年   11418篇
  2011年   15275篇
  2010年   12152篇
  2009年   13718篇
  2008年   14052篇
  2007年   13820篇
  2006年   12416篇
  2005年   11112篇
  2004年   10506篇
  2003年   10417篇
  2002年   9829篇
  2001年   9733篇
  2000年   9134篇
  1999年   9522篇
  1998年   24328篇
  1997年   16708篇
  1996年   12797篇
  1995年   9517篇
  1994年   8362篇
  1993年   8379篇
  1992年   6055篇
  1991年   5695篇
  1990年   5679篇
  1989年   5318篇
  1988年   5043篇
  1987年   4419篇
  1986年   4299篇
  1985年   4812篇
  1984年   4422篇
  1983年   3994篇
  1982年   3654篇
  1981年   3730篇
  1980年   3429篇
  1979年   3326篇
  1978年   3334篇
  1977年   3750篇
  1976年   4847篇
  1975年   2850篇
  1974年   2663篇
  1973年   2730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Flour blends of quinoa-wheat containing 0, 5, 10, 15, and 20% of manually dehulled quinoa meal or flour were evaluated for dough mixing and breadmaking properties and liking of the bread by a small panel. Increasing amounts of quinoa meal or flour increased farinograph absorption and dislike of bread for most of the panel. Dough development time increased with increase in meal but decreased with increase in quinoa flour. At 10% inclusion levels differences in liking from control 100% wheat flour bread were smaller for flour or water extracted meal to most of the panel, than with 10% non-extracted meal. This suggests that 10% inclusion of flour or water extracted meal may have potential for further investigation.  相似文献   
922.
The electrical conductivity of solution-grown ethyl cellulose (EC) films, 5–30 μm thick, has been studied in the sandwich configuration (metal–EC–metal) as a function of iodine concentration from 0.5 to 5.0 wt% ratio. The studies were conducted in the temperature range 333–383 K, while the field was varied over the range (3.0–5.5) × 104V/cm. Aluminium was used as the lower electrode, while the upper electrode was of Al, Ag, Cu, Au or Sn. Certain transient effects such as a large burst of current immediately after the application of field were observed. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories of electrical conduction. The results show that the electrical conduction follows Ohm's law at lower fields, while at higher fields, space-charge limited current (SCLC) was observed. It was also found that Richardson–Schottky emission was responsible, to some extent, for the transport of charge carriers in the polymer. The conductivity of the films increased on doping with iodine. The dopant molecules are considered to act as additional trapping centes and provide links between the polymer molecules in the amorphous region, thus resulting in the formation of charge transfer complexes.  相似文献   
923.
The change to lead-free solders means that circuit board inspection will become more important than ever. The author investigates differences between lead and lead-free solders.  相似文献   
924.
A new method for simulation of truncated random variables is described. Several similar methods are considered. It is shown that a substantial reduction in computation time is achieved by utilizing the proposed method.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 12–13, April, 1995.  相似文献   
925.
It was shown that, under thermal loads that are sufficiently larger (smaller) than a certain value, the heat transfer coefficient for porous-sublimation cooling increases (decreases) with an increase in the thermal load.Physico-Technical Low Temperatures Institute, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Inzlieneron-Fizicheskii Zhurnal, Vol. 62, No. 6, pp. 783–785, June, 1992.  相似文献   
926.
927.
The work examines the problem of constructing an admissible operation condition domain for a well-stirred reactor which would satisfy restrictions in conversion, selectivity, heat removal and stability. The domain is very important and must be known during the reactor design and control stages because it yields visual information for analyzing the reactor operations and makes it possible to find the variation intervals of decision variables, necessary to calculate and optimize the reactor. Being known, the admissible operation condition domain makes it possible to estimate the limiting restrictions and to choose the necessary reserves. The domain has completely been studied analytically for chemical processes with arbitrary kinetics.  相似文献   
928.
929.
The regular associated solution model for binary systems has been modified by incorporating the size of the complex as an explicit variable. The thermodynamic properties of the liquid alloy and the interactions between theA μB type of complex and the unassociated atoms in anA-B binary have been evaluated as a function of relative size of the complex using the activity coefficients at infinite dilution and activity data at one other composition in the binary. The computational procedure adopted for determining the concentration of clusters and interaction energies in the associated liquid is similar to that proposed by Lele and Rao. The analysis has been applied to the thermodynamic mixing functions of liquid Al-Ca alloys believed to contain Al2Ca associates. It is found that the size of the cluster significantly affects the interaction energies between the complex and the unassociated atoms, while the equilibrium constant and enthalpy change for the association reaction exhibit only minor variation, when the equations are fitted to experimental data. The interaction energy between unassociated free atoms remains virtually unaltered as the size of the complex is varied between extreme values. Accurate data on free energy, enthalpy, and volume of mixing at the same temperature on alloy systems with compound forming tendency would permit a rigorous test of the proposed model.  相似文献   
930.
Intelligent assistance for software development and maintenance   总被引:2,自引:0,他引:2  
An environment is described, called Professor Marvel, that provides early error checking and answers questions about the program under development. The environment has a certain understanding of the systems being developed and how to use tools to produce software. It aids individual programmers and helps coordinate programming teams. The key components of Marvel are a database that stores data represented as objects, as in object-oriented languages, and a model of the development process that imposes a structure on programming activities. Marvel's support of insight and of opportunistic processing is discussed at length, as is the handling of side effects. A sample session is described  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