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   119384篇
  免费   9887篇
  国内免费   4989篇
电工技术   7187篇
技术理论   7篇
综合类   7665篇
化学工业   20541篇
金属工艺   6550篇
机械仪表   7396篇
建筑科学   9806篇
矿业工程   3487篇
能源动力   3529篇
轻工业   7779篇
水利工程   2130篇
石油天然气   7365篇
武器工业   894篇
无线电   13481篇
一般工业技术   14371篇
冶金工业   5539篇
原子能技术   1305篇
自动化技术   15228篇
  2024年   556篇
  2023年   2048篇
  2022年   3557篇
  2021年   4906篇
  2020年   3766篇
  2019年   3165篇
  2018年   3412篇
  2017年   3960篇
  2016年   3321篇
  2015年   4728篇
  2014年   5748篇
  2013年   6840篇
  2012年   7497篇
  2011年   8032篇
  2010年   7019篇
  2009年   6703篇
  2008年   6495篇
  2007年   6136篇
  2006年   6403篇
  2005年   5568篇
  2004年   3808篇
  2003年   3323篇
  2002年   3102篇
  2001年   2828篇
  2000年   2981篇
  1999年   3197篇
  1998年   2701篇
  1997年   2289篇
  1996年   2115篇
  1995年   1846篇
  1994年   1494篇
  1993年   1075篇
  1992年   874篇
  1991年   691篇
  1990年   499篇
  1989年   438篇
  1988年   354篇
  1987年   245篇
  1986年   169篇
  1985年   98篇
  1984年   65篇
  1983年   49篇
  1982年   63篇
  1981年   39篇
  1980年   36篇
  1979年   10篇
  1978年   3篇
  1965年   3篇
  1959年   4篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
磁控溅射Ge/Si多层膜X射线低角衍射界面结构分析   总被引:5,自引:1,他引:5  
本文对磁控溅射不同结构的Ge/Si多层膜样品进行了X射线衍射的测试和分析,并进一步采用有过渡层的光学多层膜衍射模型对衍射谱进行了拟合;获得了扩散层厚度和分层厚度等多层膜的结构参数,定性讨论了多层膜中互扩散与分层厚度铁关系。计算结果与实验结果符合较好。  相似文献   
992.
深入教育改革探索培养创新人才的新思路   总被引:2,自引:0,他引:2  
为培养适应21世纪飞速发展的科技竞争需要的优秀人才,我们对现有培养模式所进行的教育改革中,作了一些尝试。吸取MIT等国外著名大学的成功办学经验,总结我院在原有教改试点班工作中所取得的成绩,组建了MIT电子信息试点班,并以此为突破口.寻求培养宽厚型创新人才的新思路,形成以信息为主线涉及多个学科基础理论的课程体系,带动面上教学。并论述了设立MIT电子信息试点班的必要性和可能性,介绍了该试点班的培养目标和培养特色。  相似文献   
993.
介绍了键控特技的基本原理及分类,论述了键控特技应用于电视播出系统的必要性,并指出如何选择和使用适合于电视播出系统的键控混合器.  相似文献   
994.
针对放电型 S2 激光管的设计中始终未能很好解决电极可拆卸性及可靠性的难题 ,首次提出了一个以不锈钢材料作激光管管壳 ,借助于燕尾槽实现电极可拆卸的设计方案 ,从而为横向脉冲快放电型 S2 激光器实现激光振荡创造了条件。  相似文献   
995.
Nonuniform sampling can be encountered in various practical processes because of random events or poor timebase. The analysis and applications of the nonuniform sampling for deterministic signals related to the linear canonical transform (LCT) have been well considered and researched, but up to now no papers have been published regarding the various nonuniform sampling theorems for random signals related to the LCT. The aim of this article is to explore the nonuniform sampling and reconstruction of random signals associated with the LCT. First, some special nonuniform sampling models are briefly introduced. Second, based on these models, some reconstruction theorems for random signals from various nonuniform samples associated with the LCT have been derived. Finally, the simulation results are made to prove the accuracy of the sampling theorems. In addition, the latent real practices of the nonuniform sampling for random signals have been also discussed.  相似文献   
996.
Based on a memristive diode bridge cascaded with series resistor and inductor filter, a modified memristive canonical Chua’s circuit is presented in this paper. With the modelling of the memristive circuit, a normalised system model is built. Stability analyses of the equilibrium points are performed and bifurcation behaviours are investigated by numerical simulations and hardware experiments. Most extraordinary in the memristive circuit is that within a parameter region, coexisting phenomenon of multiple bifurcation modes is emerged under six sets of different initial values, resulting in the coexistence of four sets of topologically different and disconnected attractors. These coexisting attractors are easily captured by repeatedly switching on and off the circuit power supplies, which well verify the numerical simulations.  相似文献   
997.
Graphene aerogel microlattices (GAMs) hold great prospects for many multifunctional applications due to their low density, high porosity, designed lattice structures, good elasticity, and tunable electrical conductivity. Previous 3D printing approaches to fabricate GAMs require either high content of additives or complex processes, limiting their wide applications. Here, a facile ion‐induced gelation method is demonstrated to directly print GAMs from graphene oxide (GO) based ink. With trace addition of Ca2+ ions as gelators, aqueous GO sol converts to printable gel ink. Self‐standing 3D structures with programmable microlattices are directly printed just in air at room temperature. The rich hierarchical pores and high electrical conductivity of GAMs bring admirable capacitive performance for supercapacitors. The gravimetric capacitance (Cs) of GAMs is 213 F g?1 at 0.5 A g?1 and 183 F g?1 at 100 A g?1, and retains over 90% after 50 000 cycles. The facile, direct 3D printing of neat graphene oxide can promote wide applications of GAMs from energy storage to tissue engineering scaffolds.  相似文献   
998.
The aggressive downscaling of complementary metal–oxide–semiconductor (CMOS) technology to the sub-21-nm technology node is facing great challenges. Innovative technologies such as metal gate/high-k dielectric integration, source/drain engineering, mobility enhancement technology, new device architectures, and enhanced quasiballistic transport channels serve as possible solutions for nanoscaled CMOS. Among them, mobility enhancement technology is one of the most promising solutions for improving device performance. Technologies such as global and process-induced strain technology, hybrid-orientation channels, and new high-mobility channels are thoroughly discussed from the perspective of technological innovation and achievement. Uniaxial strain is superior to biaxial strain in extending metal–oxide–semiconductor field-effect transistor (MOSFET) scaling for various reasons. Typical uniaxial technologies, such as embedded or raised SiGe or SiC source/drains, Ge pre-amorphization source/drain extension technology, the stress memorization technique (SMT), and tensile or comprehensive capping layers, stress liners, and contact etch-stop layers (CESLs) are discussed in detail. The initial integration of these technologies and the associated reliability issues are also addressed. The hybrid-orientation channel is challenging due to the complicated process flow and the generation of defects. Applying new high-mobility channels is an attractive method for increasing carrier mobility; however, it is also challenging due to the introduction of new material systems. New processes with new substrates either based on hybrid orientation or composed of group III–V semiconductors must be simplified, and costs should be reduced. Different mobility enhancement technologies will have to be combined to boost device performance, but they must be compatible with each other. The high mobility offered by mobility enhancement technologies makes these technologies promising and an active area of device research down to the 21-nm technology node and beyond.  相似文献   
999.
徐玉 《电信科学》2011,27(12):62-66
云计算的出现,改变了传统IT基础设施的使用方式和软件部署模式,并带来了大型云计算数据中心的建设热潮。本文阐述了全球数据中心的发展趋势,总结了数据中心发展的特点,并对我国数据中心发展的情况做了分析。  相似文献   
1000.
We combine interferometric lithography and inductively coupled plasma etching to fabricate GaAs subwavelength grating (SWG) which mimics the moth eye structures. Through the modification of morphology parameters, including profile, height and packing fraction, tapered, high-aspect-ratio and closely-packed GaAs SWGs are obtained. The measurement of spectral reflectance of the fabricated SWGs shows that reflection has been dramatically reduced compared to the polished GaAs surface. Particularly, the optimized SWG structures exhibit an average reflection below 5% in the wavelengths ranging from 350 to 900 nm. Furthermore, the angular-independent property is demonstrated by measuring the reflectance versus varying angles of incidence at 532 and 632.8 nm wavelengths.  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