首页 | 官方网站   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   204074篇
  免费   2427篇
  国内免费   554篇
工业技术   207055篇
  2021年   1981篇
  2019年   2004篇
  2018年   3680篇
  2017年   3718篇
  2016年   3998篇
  2015年   2231篇
  2014年   3786篇
  2013年   8745篇
  2012年   5686篇
  2011年   7222篇
  2010年   5861篇
  2009年   6495篇
  2008年   6613篇
  2007年   6498篇
  2006年   5582篇
  2005年   5122篇
  2004年   4634篇
  2003年   4560篇
  2002年   4257篇
  2001年   4298篇
  2000年   3968篇
  1999年   4033篇
  1998年   10032篇
  1997年   7024篇
  1996年   5340篇
  1995年   4106篇
  1994年   3589篇
  1993年   3828篇
  1992年   2958篇
  1991年   2977篇
  1990年   2887篇
  1989年   2832篇
  1988年   2852篇
  1987年   2480篇
  1986年   2554篇
  1985年   2839篇
  1984年   2679篇
  1983年   2535篇
  1982年   2283篇
  1981年   2254篇
  1980年   2339篇
  1979年   2351篇
  1978年   2368篇
  1977年   2483篇
  1976年   2886篇
  1975年   2186篇
  1974年   2065篇
  1973年   2157篇
  1972年   1934篇
  1971年   1744篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Duchenne muscular dystrophy (DMD) is a severe hereditary disease caused by a lack of dystrophin, a protein essential for myocyte integrity. Mitochondrial dysfunction is reportedly responsible for DMD. This study examines the effect of glucocorticoid deflazacort on the functioning of the skeletal-muscle mitochondria of dystrophin-deficient mdx mice and WT animals. Deflazacort administration was found to improve mitochondrial respiration of mdx mice due to an increase in the level of ETC complexes (complexes III and IV and ATP synthase), which may contribute to the normalization of ATP levels in the skeletal muscle of mdx animals. Deflazacort treatment improved the rate of Ca2+ uniport in the skeletal muscle mitochondria of mdx mice, presumably by affecting the subunit composition of the calcium uniporter of organelles. At the same time, deflazacort was found to reduce the resistance of skeletal mitochondria to MPT pore opening, which may be associated with a change in the level of ANT2 and CypD. In this case, deflazacort also affected the mitochondria of WT mice. The paper discusses the mechanisms underlying the effect of deflazacort on the functioning of mitochondria and contributing to the improvement of the muscular function of mdx mice.  相似文献   
72.
Bunruangses  M.  Youplao  P.  Amiri  I. S.  Pornsuwancharoen  N.  Yupapin  P. 《SILICON》2020,12(12):3057-3057
Silicon - The original version of this article unfortunately contained a mistake in the “Acknowledgments” section.  相似文献   
73.
Amorphous silicon carbide (a-SiC:H) thin films were synthesized using trichloromethylsilane by a hot wire chemical vapor deposition process. The deposited films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy to confirm its chemical bonding, structural network and composition of the a-SiC:H films. The optical microscopy images reveal that hydrogen dilution increased the surface roughness and pore density of a-SiC:H thin film. The Raman spectroscopy and FTIR spectra reveal chemical network consisting of Si-Si, C-C and Si-C bonds, respectively. The XRD spectroscopy and Raman spectroscopy indicate a-SiC:H still has short-range order. In addition, in vitro cytotoxicity test ensures the behavior of cell–semiconductor hybrid to monitor the proper coordination. The live–dead assays and MTT assay reveal an increase in green nucleus cell, and cell viability is greater than 88%, respectively, showing non-toxic nature of prepared a-SiC:H film. Moreover, the result indicated by direct contact assay, and cell prefers to adhere and proliferate on a-SiC:H thin films having a positive effect as artificial heart valve coating material.  相似文献   
74.
Nanosized particles of CoAlxFe2-xO4, where 0?≤?x?≤?2, were synthesized by the sol–gel combustion method and the magnetic properties of these compounds were investigated. According to X-ray diffractograms, the samples are single phase and the crystallite size is between 7 and 25?nm. The room temperature saturation magnetization of the samples was estimated from the cation distribution and ferromagnetic resonance spectra were used to determine the magnetocrystalline anisotropy. The results show that the saturation magnetization and the magnetocrystalline anisotropy vary over a wide range, from maxima of Ms =?0.42?MA/m and K?=?0.39?kJ/m3 for x?=?1.0 to minima of almost zero for x?≈?1.4, a result that could be useful for practical applications of these materials.  相似文献   
75.
Narrow band emissions at 2.6–2.8 THz are observed out of liquid helium cooled 1 mm disk chips prepared of a wafer with the very low n type doped weak barrier GaAs–GaAlAs superlattice of 1000 periods. The emissions are at about 8.0–18.0 V pulsed voltage applied to the chips in region of the chips positive DC differential conductivity that guaranties absence of inhomogeneous electric field domains in the chips. The emission frequency bands are estimated with a cyclotron resonance filter; the measurements show that the band width is of about that of the THz quantum cascade laser. By using long voltage pulses the chip heating above 100 K is achieved without substantial change in emission power. We speculate that the emission is super luminescence (amplification) of whispering gallery modes in the chips as a result of inverted Wannier-Stark level transitions under bias. The results are the first world demonstration of THz stimulated emission in a simple superlattice within region of positive DC differential conductivity; they give strong impetus for development of THz and higher frequency sources based on such simple superlattices; the sources should well compete with the THz quantum cascade lasers in particular at elevated temperatures.  相似文献   
76.
77.
78.
79.
80.
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-23

京公网安备 11010802026262号