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   347771篇
  免费   3677篇
  国内免费   1488篇
电工技术   6216篇
综合类   202篇
化学工业   54204篇
金属工艺   14604篇
机械仪表   10684篇
建筑科学   8269篇
矿业工程   2259篇
能源动力   8248篇
轻工业   31140篇
水利工程   3856篇
石油天然气   8781篇
武器工业   55篇
无线电   37296篇
一般工业技术   70068篇
冶金工业   61510篇
原子能技术   9524篇
自动化技术   26020篇
  2021年   2851篇
  2019年   2588篇
  2018年   4905篇
  2017年   4864篇
  2016年   5294篇
  2015年   3246篇
  2014年   5462篇
  2013年   14957篇
  2012年   8715篇
  2011年   11505篇
  2010年   9432篇
  2009年   10794篇
  2008年   11007篇
  2007年   10819篇
  2006年   9527篇
  2005年   8846篇
  2004年   8325篇
  2003年   8017篇
  2002年   8014篇
  2001年   7875篇
  2000年   7562篇
  1999年   7529篇
  1998年   17831篇
  1997年   13208篇
  1996年   10140篇
  1995年   7778篇
  1994年   6994篇
  1993年   6919篇
  1992年   5279篇
  1991年   5275篇
  1990年   5135篇
  1989年   5134篇
  1988年   5008篇
  1987年   4303篇
  1986年   4311篇
  1985年   4893篇
  1984年   4582篇
  1983年   4224篇
  1982年   3957篇
  1981年   4110篇
  1980年   3910篇
  1979年   3854篇
  1978年   3930篇
  1977年   4506篇
  1976年   5777篇
  1975年   3609篇
  1974年   3440篇
  1973年   3431篇
  1972年   3016篇
  1971年   2806篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
Mathematical models of thermomechanical processes which are based on the laws of rational thermodynamics of irreversible processes are treated. Singular features of the unsteady-state behavior of a continuous medium are demonstrated within different models, such as a medium with internal parameters of state, a medium with memory, and a medium of the velocity type.  相似文献   
62.
Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase.  相似文献   
63.
64.
65.
A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994.  相似文献   
66.
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval.  相似文献   
67.
Serum vanadium, aluminum, silicon and beta 2-microglobulin levels as well as the red cell count, hemoglobin and systolic blood pressure were simultaneously measured in 80 chronic hemodialysis patients. The serum vanadium level was positively correlated with the serum levels of aluminum, silicon and beta 2-microglobulin as well as the systolic blood pressure, and was inversely correlated with the red cell count and hemoglobin. The mean serum vanadium level was 18.4 +/- 7.6 ng/ml before hemodialysis and decreased to 13.0 +/- 5.30 ng/ml at the completion of dialysis. The dialysate vanadium level increased from 0.4 +/- 0.2 (inflow) to 1.0 +/- 0.4 ng/ml (outflow). It was concluded that vanadium was transferred from blood to dialysate when purified water was used in the preparation of the dialysate.  相似文献   
68.
The immunological agglutination reactions of physically absorbed F(ab')2 molecules onto anionic and cationic latex particles have been investigated by means of optical absorbance measurements. These measurements have been conducted under different conditions to determine the most influential factors. Surface F(ab')2 and BSA densities, particle concentration in the reaction medium and polyethylene glycol concentration are some of these factors. Sensitized cationic and anionic latexes differ considerably with respect to their colloidal stability and reactivity. As a general rule, the sensitized cationic latex has a relatively higher colloidal stability and hence, it provides reagents with a better optical response. Less than 0.025 microgram/ml of C-reactive protein has been detected using this particle enhanced optical immunoassay.  相似文献   
69.
For pt.I see ibid., vol.43, no.6, pp.1150-9 (1996). An exact solution of the electrostatic problem for calculating the surface charge and electric field distributions in an arbitrary periodic interdigital transducer (IDT) is given using the results of our companion paper. An arbitrary external electric field may be specified along the electrode structure with the unit cell containing one electrode, or several electrodes, of different widths. The potentials of the electrodes that may be specified are also arbitrary. It is shown that in the case without an external field, the solution includes all the known results as special cases. The case of shorted electrodes in the external electric field is investigated in detail. The surface charge and electric field distributions are calculated for a spatially harmonic external field with an arbitrary wavenumber. The results of the calculations are represented graphically for various ratios between the period of the electrode structure and the wavelength of the external field for the case of a unit cell containing one or two electrodes of different widths  相似文献   
70.
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