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   92824篇
  免费   7151篇
  国内免费   3944篇
电工技术   4944篇
技术理论   7篇
综合类   5989篇
化学工业   15761篇
金属工艺   5397篇
机械仪表   5854篇
建筑科学   7164篇
矿业工程   3171篇
能源动力   2751篇
轻工业   5408篇
水利工程   1604篇
石油天然气   6492篇
武器工业   656篇
无线电   10076篇
一般工业技术   10963篇
冶金工业   4922篇
原子能技术   1072篇
自动化技术   11688篇
  2024年   409篇
  2023年   1524篇
  2022年   2526篇
  2021年   3620篇
  2020年   2701篇
  2019年   2432篇
  2018年   2702篇
  2017年   2967篇
  2016年   2643篇
  2015年   3446篇
  2014年   4465篇
  2013年   5214篇
  2012年   5520篇
  2011年   5969篇
  2010年   5391篇
  2009年   4997篇
  2008年   4809篇
  2007年   4801篇
  2006年   4916篇
  2005年   4323篇
  2004年   3032篇
  2003年   3050篇
  2002年   3357篇
  2001年   2841篇
  2000年   2476篇
  1999年   2638篇
  1998年   2011篇
  1997年   1742篇
  1996年   1734篇
  1995年   1352篇
  1994年   1051篇
  1993年   778篇
  1992年   613篇
  1991年   475篇
  1990年   354篇
  1989年   281篇
  1988年   245篇
  1987年   137篇
  1986年   104篇
  1985年   64篇
  1984年   53篇
  1983年   43篇
  1982年   47篇
  1981年   27篇
  1980年   25篇
  1979年   6篇
  1978年   2篇
  1977年   2篇
  1959年   2篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Amphotericin B (AMB) was often used in intra-articular injection administration for fungal arthritis, because it could often bring a satisfactory therapeutic efficacy and a minimum systemic toxic side effect. However, because of the multiple operations and the frequent injections, the compliance of the patients was bad. Therefore, to develop a long-term sustained-released preparation of AMB for mycotic arthritis intra-articular administration is of great significance. The purpose of present study was to develop a long-term sustained-released in situ gel of a water-insoluble drug AMB for mycotic arthritis intra-articular administration. Based on the evaluations of the in vitro properties of the formulations, the formulation containing 10% (w/w) ethanol, 15% (w/w) PG, 0.75% (w/w) HA, 5% (w/w) purified soybean oil, 0.03% (w/w) α-tocopherol, 15% (w/w) water and 55% (w/w) glyceryl monooleate was selected as a suitable intra-articular injectable in situ gel drug delivery system for water-insoluble drug AMB. Furthermore, the results of the in vivo study on rabbits showed that the selected formulation was a safe and effective long-term sustained-released intra-articular injectable AMB preparation. Therefore, the presented in situ AMB gel could reduce the frequency of the administration in the AMB treatment of fungal arthritis, and then would get a good patient compliance.  相似文献   
2.
3.
4.
5.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
6.
7.
8.
程俊琦  郭勇 《电子测试》2015,(2):60-61,59
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。  相似文献   
9.
Effects of Rare Earths on Toughness of 31Mn2SiRE Wear-Resistance Cast Steel   总被引:1,自引:0,他引:1  
The toughness of 31Mn2SiRE wear-resistance cast steel were increased by means of RE compound modification and high temperature austenitizing. The results show that the microstructures can be refined, needle and network ferrite are eliminated, the dislocation density and the quantity of dislocated martensite are increased remarkably, and the shape and distribution of inclusions are improved by the addition of RE. Therefore, the mechanical properties of the modified steel can be greatly increased, especially the toughness (αK) by 44%, yield strength (σs) by 10%, and elongation (δ5) by 42%.  相似文献   
10.
Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(tγ), shows a decreasing trend with step strain. The experimental results indicate that G(tγ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(tγ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(tγ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior.  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