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   299952篇
  免费   5080篇
  国内免费   2549篇
电工技术   6378篇
技术理论   5篇
综合类   1554篇
化学工业   48033篇
金属工艺   13588篇
机械仪表   9084篇
建筑科学   7753篇
矿业工程   2036篇
能源动力   6865篇
轻工业   27855篇
水利工程   3301篇
石油天然气   7309篇
武器工业   260篇
无线电   31649篇
一般工业技术   58063篇
冶金工业   53718篇
原子能技术   6267篇
自动化技术   23863篇
  2021年   2942篇
  2020年   2027篇
  2019年   2552篇
  2018年   4051篇
  2017年   3994篇
  2016年   4402篇
  2015年   3428篇
  2014年   5470篇
  2013年   13571篇
  2012年   9057篇
  2011年   11983篇
  2010年   9545篇
  2009年   10332篇
  2008年   11016篇
  2007年   11215篇
  2006年   9754篇
  2005年   8609篇
  2004年   7752篇
  2003年   7208篇
  2002年   7214篇
  2001年   7343篇
  2000年   6810篇
  1999年   6824篇
  1998年   14802篇
  1997年   11043篇
  1996年   8600篇
  1995年   6445篇
  1994年   5779篇
  1993年   5656篇
  1992年   4493篇
  1991年   4269篇
  1990年   4291篇
  1989年   4201篇
  1988年   3860篇
  1987年   3370篇
  1986年   3365篇
  1985年   3727篇
  1984年   3577篇
  1983年   3310篇
  1982年   2934篇
  1981年   3131篇
  1980年   2940篇
  1979年   3097篇
  1978年   2964篇
  1977年   3180篇
  1976年   4232篇
  1975年   2703篇
  1974年   2529篇
  1973年   2569篇
  1972年   2188篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The effect of the composition of sensitizing–activating solutions on the activation efficiency and the chemical coppering of diamond powders is studied. The results demonstrate that stabilizing additives improve the stability of the solutions, influence the average coppering rate, and play a key role in determining the morphology and quality of the resultant coatings. The most effective stabilizing additive is synthamid-10, which ensures the deposition of high-quality copper coatings.  相似文献   
72.
The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10?3 to 1 s?1.  相似文献   
73.
74.
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.  相似文献   
75.
Polystyrene packaging material taint was sensorily evaluated in cocoa powder for drinks and chocolate flakes using short-cut signal detection measures on differences between control and test samples and on recognition of styrene. No differences were observed in cocoa powder for drinks and plain chocolate flakes treated with 0.5 dm2 polystyrene of 1 mm thickness. However, differences were detected in milk chocolate flakes and plain chocolate flakes, which were in contact with a larger area or thicker polystyrene packaging material. The latter results were confirmed by the styrene recognition test, so polystyrene is a potential source of off-flavour for chocolate products. The amount of residual styrene in the polystyrene used was about 320 ppm, while the amounts of styrene ranged from 7 to 132 ppb in cocoa drinks and from 414 to 1447 ppb in chocolate flakes.  相似文献   
76.
77.
This paper proposes a new Kalman-filter-based recursive frequency estimator for discrete-time multicomponent sinusoidal signals whose frequencies may be time-varying. The frequency estimator is based on the linear prediction approach and it employs the Kalman filter to track the linear prediction coefficients (LPCs) recursively. Frequencies of the sinusoids can then be computed using the estimated LPCs. Due to the coloredness of the linear prediction error, an iterative algorithm is employed to estimate the covariance matrix of the prediction error and the LPCs alternately in the Kalman filter in order to improve the tracking performance. Simulation results show that the proposed Kalman-filter-based iterative frequency estimator can achieve better tracking results than the conventional recursive least-squares-based estimators.  相似文献   
78.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress.  相似文献   
79.
Technology is developed for preparing refractory components made of partially stabilized zirconium dioxide using an isostatic compaction press. Technology is provided for manufacturing dispensing nozzles using combined and separately stabilized zirconium dioxide, and also indices of the refractories obtained and imported materials are compared. __________ Translated from Novye Ogneupory, No. 3, pp. 127–131, March 2008.  相似文献   
80.
Compositions have been developed for nonshrinking vibrocast thermally insulating light refractory concretes with densities of 1.0, 1.3, 1.5, and 1.8 g/cm3 for temperatures of use up to 1400°C. The structure and properties have been examined for the concrete of density 1.3 g/cm3. __________ Translated from Novye Ogneupory, No. 4, pp. 29–32, April, 2008.  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