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   8095篇
  免费   124篇
  国内免费   1篇
电工技术   140篇
综合类   4篇
化学工业   913篇
金属工艺   109篇
机械仪表   146篇
建筑科学   180篇
矿业工程   33篇
能源动力   108篇
轻工业   707篇
水利工程   42篇
石油天然气   22篇
无线电   807篇
一般工业技术   1008篇
冶金工业   3164篇
原子能技术   109篇
自动化技术   728篇
  2021年   55篇
  2020年   38篇
  2019年   47篇
  2018年   53篇
  2017年   61篇
  2016年   80篇
  2015年   62篇
  2014年   89篇
  2013年   197篇
  2012年   169篇
  2011年   241篇
  2010年   205篇
  2009年   218篇
  2008年   232篇
  2007年   244篇
  2006年   205篇
  2005年   206篇
  2004年   189篇
  2003年   168篇
  2002年   144篇
  2001年   148篇
  2000年   166篇
  1999年   209篇
  1998年   743篇
  1997年   459篇
  1996年   375篇
  1995年   235篇
  1994年   216篇
  1993年   265篇
  1992年   151篇
  1991年   145篇
  1990年   141篇
  1989年   160篇
  1988年   143篇
  1987年   116篇
  1986年   138篇
  1985年   124篇
  1984年   89篇
  1983年   89篇
  1982年   81篇
  1981年   67篇
  1980年   67篇
  1979年   78篇
  1978年   81篇
  1977年   112篇
  1976年   178篇
  1975年   60篇
  1974年   56篇
  1973年   54篇
  1972年   37篇
排序方式: 共有8220条查询结果,搜索用时 31 毫秒
981.
982.
The read length for DNA sequencing using capillary electrophoresis and replaceable linear polyacrylamide (LPA) solutions has been extended to more than 1000 bases with a run time of 80 min. This result was successfully achieved through the combined use of cycle sequencing with dye-labeled primers, improved matrix and separation conditions, and enhanced base-calling software. The influences of LPA molecular weight and concentration on separation were investigated. Additionally, the separation buffer, column temperature, and electric field were adjusted to increase the number of resolvable DNA fragments per run while maintaining an enhanced separation speed. Using low concentrations [2% (w/v)] of high molecular weight LPA polymers (> 5.5 x 10(6) Da), elevated column temperature (50 degrees C) and moderately high field (150 V/cm), rapid sequencing analysis for more than 1000 bases on a model ssM13mp18 template was obtained with 96.8% accuracy.  相似文献   
983.
Previous studies have shown that galvanic stimulation of semicircular canal organs can modulate their afferent discharge. However, it has not been resolved whether this modulation derived from direct stimulation of hair cells, afferent nerve fibers, some combination of the two, or some as yet unknown path. This problem is addressed in the present study. Experiments were designed first to determine the gross current path necessary for the DC current to modulate afferent firing. These led to the conclusion that the current path had to flow between endolymph and perilymph across the neuroepithelium. Next, the various components in this established path were considered: the afferents, the hair cells, between the hair cells, or some combination of the three. These experiments led to the conclusion that the current pathway was across the hair cells causing transmitter release and thus affecting afferent activity.  相似文献   
984.
The need for keeping the package at acceptable temperatures has become a critical issue in recent years. To aid in the cooling of their modules, many electronics manufacturers have implemented the use of heat sinks. Thermal interfaces placed between the package and the heat sink to aid in heat dissipation have become increasingly more important and the demands on these interfaces have increased significantly. During the selection of interface materials many factors must be considered. Compliance, conformability, modulus, ease of installation, and cut-through resistance are all important  相似文献   
985.
A sample of 443 Pakistani infants from four different socioeconomic areas was followed longitudinally study the emergence of the primary teeth. The mean ages of emergence of the primary teeth, without regard what kind of tooth and dental ages of the primary teeth were calculated. The subjects showed no sexual dimorphism in the emergence times of the primary teeth. The children from poor areas. were ahead by statistically significant differences from upper middle class, for emergence of the primary teeth 17-20. On comparison with Swedish standards (H?gg & Taranger, 1985) Pakistani children are delayed, by a statistically significant difference, in the emergence of primary teeth 1-16, however, they were at par in the emergence of 17-20 primary teeth.  相似文献   
986.
We find the rate of a typical code from the regular low-density parity-check (LDPC) ensemble. We then show that the rate of a code from the ensemble converges to the design rate in quadratic mean and almost surely.  相似文献   
987.
The effects of niflumic acid on whole-cell membrane currents and mechanical activity were examined in the rat portal vein. In freshly dispersed portal vein cells clamped at -60 mV in caesium (Cs+)-containing solutions, niflumic acid (1-100 microM) inhibited calcium (Ca2+)-activated chloride currents (IC1(Ca)) induced by caffeine (10 mM) and by noradrenaline (10 microM). In a potassium (K+)-containing solution and at a holding potential of - 10 mV, niflumic acid (10-100 microM) induced an outward K+ current (IK(ATP)) which was sensitive to glibenclamide (10-30 microM). At concentrations < 30 microM and at a holding potential of -2 mV, niflumic acid had no effect on the magnitude of the caffeine- or noradrenaline-stimulated current (IBK(Ca)) carried by the large conductance, Ca(2+)-sensitive K+ channel (BKCa). However, at a concentration of 100 microM, niflumic acid significantly inhibited IBK(Ca)) evoked by caffeine (10 mM) but not by NS1619 (1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3 H) benzimidazolone; 20 microM). In Cs(+)-containing solutions, niflumic acid (10-100 microM) did not inhibit voltage-sensitive Ca2+ currents. In intact portal veins, niflumic acid (1-300 microM) inhibited spontaneous mechanical activity, an action which was partially antagonised by glibenclamide (1-10 microM), and contractions produced by noradrenaline (10 microM), an effect which was glibenclamide-insensitive. It is concluded that inhibition of ICl(Ca) and stimulation of IK(ATP) both contribute to the mechano-inhibitory actions of niflumic acid in the rat portal vein.  相似文献   
988.
Closed subcutaneous rupture of the anterior tibial tendon is a relatively uncommon injury that requires a thorough clinical examination to diagnose correctly. The authors report a case of this disorder and provide a review of the relevant literature. A method of surgical repair not previously described in the literature is also presented.  相似文献   
989.
In 4 conditioned lick suppression experiments with rats, the combined effects of latent inhibition treatment followed by overshadowing treatment were assessed as a test of the comparator hypothesis's (R.R. Miller & L.D. Matzel, 1988) explanations of overshadowing and latent inhibition. Experiments 1 and 2 confirmed the prediction of the comparator hypothesis that combined latent inhibition and overshadowing treatments attenuate the response deficit produced by either treatment alone. Furthermore, consistent with the comparator hypothesis, posttraining changes in the associative status of the putative comparator stimulus altered responding to the target conditioned stimulus (Experiment 3), and switching contexts between latent inhibition and overshadowing treatments (Experiment 4) eliminated the interaction between the latent inhibition and overshadowing treatments.  相似文献   
990.
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