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   14846篇
  免费   399篇
  国内免费   21篇
电工技术   204篇
综合类   12篇
化学工业   3147篇
金属工艺   244篇
机械仪表   314篇
建筑科学   688篇
矿业工程   101篇
能源动力   404篇
轻工业   1050篇
水利工程   136篇
石油天然气   167篇
武器工业   1篇
无线电   947篇
一般工业技术   2160篇
冶金工业   3771篇
原子能技术   163篇
自动化技术   1757篇
  2022年   119篇
  2021年   174篇
  2020年   146篇
  2019年   161篇
  2018年   190篇
  2017年   186篇
  2016年   224篇
  2015年   171篇
  2014年   240篇
  2013年   848篇
  2012年   467篇
  2011年   654篇
  2010年   423篇
  2009年   460篇
  2008年   596篇
  2007年   570篇
  2006年   566篇
  2005年   464篇
  2004年   377篇
  2003年   381篇
  2002年   394篇
  2001年   260篇
  2000年   248篇
  1999年   271篇
  1998年   330篇
  1997年   305篇
  1996年   297篇
  1995年   282篇
  1994年   283篇
  1993年   328篇
  1992年   281篇
  1991年   212篇
  1990年   222篇
  1989年   237篇
  1988年   181篇
  1987年   235篇
  1986年   213篇
  1985年   273篇
  1984年   243篇
  1983年   215篇
  1982年   198篇
  1981年   209篇
  1980年   172篇
  1979年   189篇
  1978年   190篇
  1977年   151篇
  1976年   172篇
  1975年   185篇
  1974年   139篇
  1973年   135篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
With the goal of improving process efficiency and reducing risk, this article describes a pollution-prevention analysis technique that can be applied to most secondary steel heat-treating operations involving quenching. Costs, risk assessments, and pollution-prevention options are discussed, as are the effects of quenching on two subsequent processes—parts cleaning and tempering. In contrast to many process comparisons, the issues of worker exposure, material safety and toxicity, liability, waste reduction, reclamation, and disposal are emphasized.  相似文献   
92.
93.
94.
Evaluated 120 healthy, sedentary, middle-aged adults randomly assigned to either a 6-mo home-based aerobic exercise training program or to an assessment-only control condition. Adherence across the 6-mo period by the exercise group was demonstrated by self-report and heart rate microprocessor methods to exceed 75%. A 14-item Likert rating scale was used to measure a variety of psychological variables. Significant between-groups differences favoring the exercise group were found on scale items closely associated with actual physical changes that occurred with exercise (satisfaction with shape/appearance, perceived fitness). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
95.
A new type of radiative cooling system is described. The radiator makes use of nonimaging optics and evacuated-tube technology to radiate significant amounts of heat to the 3 K environment of outer space. The nonimaging optics are used to direct the radiation overhead, through the most transparent part of the 8–13 μm atmospheric window. The required optical concentration is small, and relatively simple mirror geometries are possible. The evacuated-tube technology is used to attain storage temperatures at or below the freezing point, even when dewpoint temperatures are well above the freezing point.  相似文献   
96.
The dependence of the cetane number of hydrotreated light cycle oil on chemical composition has been investigated. Cetane number was related to hydrogen content and aromaticity. The latter was determined by high performance liquid chromatography and also by carbon-13 n.m.r. spectroscopy. Specific correlations were developed in each case and a regression coefficient of 0.99 and a standard error of 1.25 were obtained for the best case. The usefulness of predicting cetane number from fuel composition is discussed.  相似文献   
97.
A nicotinic cholinergic antagonist, mecamylamine (MEC), was administered to rabbits tested on eyeblink classical conditioning (EBCC) in the 750-msec delay paradigm for 10 90-trial sessions. Nicotinic receptors were measured in 3 brain regions in S treatment groups: paired conditioned stimulus–unconditioned stimulus (CS–UCS) presentations with (1) vehicle, young; (2) vehicle, older; (3) 0.5 mg/kg MEC, young; unpaired CS–UCS with (4) 0.5 mg/kg MEC, young; and (5) vehicle, young. Daily MEC injections disrupted acquisition in young rabbits (769 trials to learning criterion vs 323 trials for vehicle-treated young rabbits). MEC-treated young rabbits learned similarly to older rabbits. Brain nicotinic receptors were not affected by 10 daily MEC injections. To our knowledge, this experimental protocol, using a low MEC dose to selectively inhibit nicotinic cholinergic receptors, is the first to demonstrate a role for nicotinic cholinergic receptors in EBCC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
99.
Arginine–8 vasopressin (AVP) was administered to rat fetuses on Embryonic Day 20 via intracisternal (IC), intrahemispheric (IH), or intrathecal (IT) injection. The IC administration of AVP promoted a 4-fold increase in motor activity, including the uncommon patterns of mouthing, licking, and facial wiping. The IH injection of AVP had little effect on fetal behavior, but IT injection resulted in pronounced increases in fetal activity, including mouthing, licking, and wiping. The IT administration of a V? antagonist blocked AVP effects, whereas IH injection potentiated AVP-induced changes in fetal behavior. The IC blockade of V? receptors suppressed facial wiping to a chemosensory fluid (lemon) and reduced oral grasping of an artificial nipple, whereas IH injection of the V? antagonist promoted facial wiping responses and increased grasping of the nipple. These data suggest that AVP may play a role in the development of responsiveness to stimuli encountered in the context of suckling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
100.
Intraoral infusion of milk to the rat fetus promoted changes in behavior (mouth and rearlimb movements), reduced responsiveness to perioral cutaneous stimulation, and resulted in expression of a fetal stretch response. Milk also altered the temporal organization of fetal movements over periods up to 30 min. The orosensory characteristics of milk, in the absence of ingestion, was sufficient to evoke these behavioral effects. Reduced responsiveness to a perioral stimulus had a rapid onset (  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