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   1931篇
  免费   39篇
  国内免费   5篇
电工技术   104篇
综合类   10篇
化学工业   469篇
金属工艺   59篇
机械仪表   45篇
建筑科学   45篇
矿业工程   2篇
能源动力   69篇
轻工业   136篇
水利工程   6篇
石油天然气   5篇
无线电   213篇
一般工业技术   287篇
冶金工业   334篇
原子能技术   62篇
自动化技术   129篇
  2022年   13篇
  2021年   31篇
  2020年   12篇
  2019年   18篇
  2018年   20篇
  2017年   23篇
  2016年   27篇
  2015年   19篇
  2014年   50篇
  2013年   89篇
  2012年   65篇
  2011年   107篇
  2010年   75篇
  2009年   58篇
  2008年   74篇
  2007年   84篇
  2006年   68篇
  2005年   72篇
  2004年   55篇
  2003年   70篇
  2002年   61篇
  2001年   42篇
  2000年   40篇
  1999年   57篇
  1998年   131篇
  1997年   73篇
  1996年   73篇
  1995年   61篇
  1994年   51篇
  1993年   34篇
  1992年   19篇
  1991年   23篇
  1990年   27篇
  1989年   32篇
  1988年   14篇
  1987年   13篇
  1986年   18篇
  1985年   17篇
  1984年   16篇
  1983年   21篇
  1982年   17篇
  1981年   12篇
  1980年   15篇
  1979年   11篇
  1978年   11篇
  1977年   16篇
  1976年   16篇
  1975年   4篇
  1973年   4篇
  1972年   3篇
排序方式: 共有1975条查询结果,搜索用时 15 毫秒
1.
2.
3.
We studied on realization of short pulse gamma ray and X-ray simultaneously induced by a femtosecond laser on NewSUBARU storage ring. Based on the fact that the transverse dimensions of electron beam are much shorter than the longitudinal one, the laser light is arranged to collide the electron beam at a right angle to generate femtosecond pulse gamma ray, furthermore, the modulated part of the electron bunch gives rise to short pulse X-ray by synchrotron radiation from a downstream bending magnet. The temporal characteristic of the radiation is analyzed in this paper, as well as the performances are estimated.  相似文献   
4.
The porcine antral follicles, 3-6 mm in diameter, were dissected from the ovaries of mature pigs, and then granulosa and cumulus cells were isolated from each follicle. In atretic follicles, high activity of neutral Ca2+/Mg2+-dependent endonuclease and DNA ladder formation, estimated by electrophoresis, were noted in granulosa cells but not in cumulus cells. Extremely low activity of the endonuclease and no DNA ladder formation were observed in both types of cells obtained from healthy follicles. Moreover, apoptotic cells were observed histochemically among granulosa cells only. A good correlation (r = 0.987) between the endonuclease activity of granulosa cells and the progesterone/estradiol ratio of follicular fluid in each follicle was found. These results suggest that apoptosis occurs in granulosa cells but not cumulus cells in the atretic antral follicles in pigs.  相似文献   
5.
液闪效率示踪法校正效果的评价   总被引:1,自引:0,他引:1  
本文评价了Aloka商品液闪仪效率示踪法dpm校正的效果。轻,中度猝灭校正效果理想,具有简便、实用和适用性广泛的特点。严重化学和颜色猝灭样品的校正结果分别随猝灭增加而向增大和减小的方向偏离,形成喇叭状曲线,文中对这一现象给出初步解释。  相似文献   
6.
7.
The leakage mechanism for a top-gate thin-film transistor (TFT) produced using the fewest process steps in the industry is analyzed in order to achieve a high-contrast liquid crystal display (LCD). Using a T-shaped TFT structure, the OFF and ON channel lengths are defined independently, so that the leakage can be reduced with no ON current decrease  相似文献   
8.
A single-ended amplifier using small packaged GaN-FETs exhibits a record 2.14 GHz W-CDMA output power. The amplifier, composed of paralleled 48 mm gate periphery FET die, delivers a peak saturated output power of 371 W with a linear gain of 11.2 dB at a drain voltage of 45 V under 2.14 GHz 3GPP W-CDMA signal input. The output power density (output power/package size) of 1.1 W/mm/sup 2/ is twice as high as that of the existing over 300 W GaAs-FET amplifiers. A low 5 MHz offset ACLR of -36 dBc with a drain efficiency of 24% is also obtained at 8 dB power back off from the saturated output power.  相似文献   
9.
Specimens of partially stabilized zirconia were slip cast from aqueous suspensions and sintered at 1500°C for 3 h. The relative density of the cast specimens and the firing shrinkage of the sintered specimens depend on the milling time for the suspension. Vickers hardness and KIC values of 11.46±s0.07 GN/m2 and 6.10 ±0.04 MN.m3/2, respectively, were obtained for all sintered specimens. The dispersion of the suspension is important in increasing the relative density of the cast specimens.  相似文献   
10.
Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints. The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints.  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