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   223530篇
  免费   13059篇
  国内免费   7927篇
电工技术   10435篇
综合类   9869篇
化学工业   25842篇
金属工艺   12178篇
机械仪表   9616篇
建筑科学   8877篇
矿业工程   4180篇
能源动力   5901篇
轻工业   20640篇
水利工程   3933篇
石油天然气   3851篇
武器工业   1603篇
无线电   25490篇
一般工业技术   33689篇
冶金工业   43023篇
原子能技术   2956篇
自动化技术   22433篇
  2024年   720篇
  2023年   2094篇
  2022年   4314篇
  2021年   5849篇
  2020年   4297篇
  2019年   3320篇
  2018年   4412篇
  2017年   4601篇
  2016年   4570篇
  2015年   5711篇
  2014年   7288篇
  2013年   12149篇
  2012年   11104篇
  2011年   12621篇
  2010年   11375篇
  2009年   11311篇
  2008年   11784篇
  2007年   11721篇
  2006年   10057篇
  2005年   8283篇
  2004年   6860篇
  2003年   5735篇
  2002年   5116篇
  2001年   5179篇
  2000年   4492篇
  1999年   4237篇
  1998年   14222篇
  1997年   8978篇
  1996年   6641篇
  1995年   4284篇
  1994年   3705篇
  1993年   3664篇
  1992年   1905篇
  1991年   1874篇
  1990年   1780篇
  1989年   1585篇
  1988年   1401篇
  1987年   1092篇
  1986年   1096篇
  1985年   1176篇
  1984年   988篇
  1983年   876篇
  1982年   861篇
  1981年   890篇
  1980年   808篇
  1979年   609篇
  1978年   527篇
  1977年   907篇
  1976年   1709篇
  1975年   397篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Physically based simulation of human hair is a well studied and well known problem. But the “pure” physically based representation of hair (and other animation elements) is not the only concern of the animators, who want to “control” the creation and animation phases of the content. This paper describes a sketch-based tool, with which a user can both create hair models with different styling parameters and produce animations of these created hair models using physically and key frame-based techniques. The model creation and animation production tasks are all performed with direct manipulation techniques in real-time.  相似文献   
95.
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   
96.
20世纪以来,人类采用技术工程治理、法律制裁和经济惩罚等措施,一定意义上改善了局部的生态环境,但是未能遏制住全球环境问题的恶化态势。生态危机的根本解决,关键在于人类自身必须进行深刻的利益观念和价值观念的变革。重新审视人与自然界的关系,对自然进行伦理关怀,寻求和建立以保护地球环境和人类生存与可持续发展的生态平衡理念。  相似文献   
97.
To gain a better understanding of the ultra-high molecular weight polyethylene (UHMWPE) wear mechanism in the physiological environment, the effects of protein and lipid constituents of synovial fluid on the specific wear rate of UHMWPE were examined experimentally. The multidirectional sliding pin-on-plate wear tester was employed to simulate the simplified sliding condition of hip joint prostheses. Bovine serum γ-globulin and synthetic l--DPPC were used as model protein and lipid constituents of synovia, respectively. Results of the wear test indicated that the UHMWPE wear rate primarily depended on the protein concentration of the test lubricant. Lipids acted as a boundary lubricant and reduced polyethylene wear in the low protein lubricants. However, the polyethylene wear rate increased with increasing lipid concentrations if the protein concentration was within the physiological level. Increased interactions between protein and lipid molecules and lipid diffusion to polyethylene surface might be responsible for the increased wear.  相似文献   
98.
99.
100.
This is part II of a study reported earlier on a method to characterize the air flow and water removal characteristics during vacuum dewatering. This article presents experimental data and analysis of results from the use of a cyclically actuated vacuum dewatering device for removing moisture from wetted porous materials such as paper with the intermittent application of vacuum and accompanying air flow though the material. Results presented include sheet moisture content as a function of residence time and hence water removal rate under a variety of process conditions. Also, experimental results on air flow through the wet porous structure and hence the role and importance of air flow during vacuum dewatering are presented. Vacuum dewatering process conditions include exit solids content between 11 and 20% solid under applied vacuum conditions of 13.5 to 67.7 kPa (4 to 20 in. Hg). Regression analysis indicated that the exit sheet moisture content exhibited a nonlinear relationship with residence time with exit solids reaching a plateau after a certain residence time. Final moisture content correlated linearly with the average overall flow rate of air through the paper sample and the basis weight of the material.  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