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   4586篇
  免费   82篇
  国内免费   3篇
电工技术   44篇
综合类   4篇
化学工业   956篇
金属工艺   95篇
机械仪表   108篇
建筑科学   195篇
矿业工程   11篇
能源动力   96篇
轻工业   377篇
水利工程   39篇
石油天然气   16篇
武器工业   2篇
无线电   401篇
一般工业技术   686篇
冶金工业   927篇
原子能技术   46篇
自动化技术   668篇
  2021年   42篇
  2020年   38篇
  2019年   51篇
  2018年   73篇
  2017年   50篇
  2016年   59篇
  2015年   49篇
  2014年   107篇
  2013年   243篇
  2012年   152篇
  2011年   206篇
  2010年   131篇
  2009年   147篇
  2008年   196篇
  2007年   172篇
  2006年   164篇
  2005年   147篇
  2004年   121篇
  2003年   111篇
  2002年   121篇
  2001年   78篇
  2000年   89篇
  1999年   88篇
  1998年   239篇
  1997年   143篇
  1996年   105篇
  1995年   85篇
  1994年   64篇
  1993年   80篇
  1992年   56篇
  1991年   54篇
  1990年   55篇
  1989年   45篇
  1988年   49篇
  1987年   51篇
  1986年   72篇
  1985年   59篇
  1984年   58篇
  1983年   54篇
  1982年   49篇
  1981年   63篇
  1980年   53篇
  1979年   54篇
  1978年   50篇
  1977年   54篇
  1976年   53篇
  1975年   45篇
  1974年   32篇
  1973年   30篇
  1972年   33篇
排序方式: 共有4671条查询结果,搜索用时 15 毫秒
11.
Abstract: Enterprise production is becoming more and more knowledge oriented nowadays and knowledge management is playing a key role in making commercial profit and maintaining enterprise competence. Knowledge characterization and measurement are the bases of knowledge management, and this paper aims to develop a method for characterizing and measuring knowledge in a comprehensive and practical way. Knowledge in its static state is modelled as a vector, whose values vary with the situation, and changes in state are modelled as a finite state machine.  相似文献   
12.
A real time control strategy for fuel cell hybrid vehicles is proposed. The objective is to reduce the hydrogen consumption by using an efficient power sharing strategy between the fuel cell system (FCS) and the energy buffer (EB). The energy buffer (battery or supercapacitor) is charge-sustained (no plug-in capabilities). The real time control strategy is derived from a non-causal optimization algorithm based on optimal control theory. The strategy is validated experimentally with a hardware-in-the-loop (HiL) test bench based on a 600 W fuel cell system.  相似文献   
13.
Soluble amyloid β (Aβ) oligomers have been shown to be highly toxic to neurons and are considered to be a major cause of the neurodegeneration underlying Alzheimer’s disease (AD). That makes soluble Aβ oligomers a promising drug target. In addition to eliminating these toxic species from the patients’ brain with antibody-based drugs, a new class of drugs is emerging, namely Aβ aggregation inhibitors or modulators, which aim to stop the formation of toxic Aβ oligomers at the source. Here, pharmacological data of the novel Aβ aggregation modulator GAL-201 are presented. This small molecule (288.34 g/mol) exhibits high binding affinity to misfolded Aβ1-42 monomers (KD = 2.5 ± 0.6 nM). Pharmacokinetic studies in rats using brain microdialysis are supportive of its oral bioavailability. The Aβ oligomer detoxifying potential of GAL-201 has been demonstrated by means of single cell recordings in isolated hippocampal neurons (perforated patch experiments) as well as in vitro and in vivo extracellular monitoring of long-term potentiation (LTP, in rat transverse hippocampal slices), a cellular correlate for synaptic plasticity. Upon preincubation, GAL-201 efficiently prevented the detrimental effect on LTP mediated by Aβ1-42 oligomers. Furthermore, the potential to completely reverse an already established neurotoxic process could also be demonstrated. Of particular note in this context is the self-propagating detoxification potential of GAL-201, leading to a neutralization of Aβ oligomer toxicity even if GAL-201 has been stepwise removed from the medium (serial dilution), likely due to prion-like conformational changes in Aβ1-42 monomer aggregates (trigger effect). The authors conclude that the data presented strongly support the further development of GAL-201 as a novel, orally available AD treatment with potentially superior clinical profile.  相似文献   
14.
15.
The risk of disease from microbiological organisms far surpasses any chemical risk associated with water treatment by chemical oxidation. Giardia lamblia and Cryptosporidium parvum, common microbiological contaminants, sometimes have fatal consequences to individuals with weak immune systems. Because effective environmentally friendly oxidants are available and accessible for treating drinking water, utilities throughout the industrialized world are investigasting alternative disinfection/oxidation practices. Chlorine dioxide and ozone are frequently used to remove taste and odor problems, color and to inactive problem microbiological species. To understand the unique value of ozone and chlorine dioxide in water treatment, one must start with the chemistry.  相似文献   
16.
(1) Objective: Considering that current knowledge of mechanisms involved in the molecular pathogenesis of Social Anxiety Disorder (SAD) is limited, we conducted a systematic review to evaluate cumulative data obtained by Proton Magnetic Resonance Spectroscopic (1H MRS) studies. (2) Methods: A computer-based literature search of Medline, EMBASE, PsycInfo, and ProQuest was performed. Only cross-sectional studies using 1H MRS techniques in participants with SAD and healthy controls (HCs) were selected. (3) Results: The search generated eight studies. The results indicated regional abnormalities in the ‘fear neurocircuitry’ in patients with SAD. The implicated regions included the anterior cingulate cortex (ACC), dorsomedial prefrontal cortex (dmPFC), dorsolateral prefrontal cortex (dlPFC), insula, occipital cortex (OC), as well as the subcortical regions, including the thalamus, caudate, and the putamen. (4) Conclusions: The evidence derived from eight studies suggests that possible pathophysiological mechanisms of SAD include impairments in the integrity and function of neurons and glial cells, including disturbances in energy metabolism, maintenance of phospholipid membranes, dysregulations of second messenger systems, and excitatory/inhibitory neurocircuitry. Conducting more cross-sectional studies with larger sample sizes is warranted given the limited evidence in this area of research.  相似文献   
17.
New ordered Laves phases RENi4Mg (RE = Sc, Sm, Tb–Lu) were synthesized from the elements in sealed tantalum ampoules in an induction furnace. Six of the structures were refined on the basis of X-ray single crystal data. The diffraction experiments gave hint for small homogeneity ranges RE1+xNi4Mg1?x. Magnetic susceptibility measurements show Curie–Weiss behavior for RE = Gd, Dy, Ho, Tm, Yb and the resulting effective magnetic moments suggest both stable trivalent states for all RE and a non-magnetic state for Ni. Gd1+xNi4Mg1?x (x ≈ 0.12) orders antiferromagnetically at a Néel temperature of TN = 4.6(5) K. Resistivity measurements reflect the metallic nature of these compounds.  相似文献   
18.
We introduce and investigate a natural extension of Dung's well-known model of argument systems in which attacks are associated with a weight, indicating the relative strength of the attack. A key concept in our framework is the notion of an inconsistency budget, which characterises how much inconsistency we are prepared to tolerate: given an inconsistency budget β, we would be prepared to disregard attacks up to a total weight of β. The key advantage of this approach is that it permits a much finer grained level of analysis of argument systems than unweighted systems, and gives useful solutions when conventional (unweighted) argument systems have none. We begin by reviewing Dung's abstract argument systems, and motivating weights on attacks (as opposed to the alternative possibility, which is to attach weights to arguments). We then present the framework of weighted argument systems. We investigate solutions for weighted argument systems and the complexity of computing such solutions, focussing in particular on weighted variations of grounded extensions. Finally, we relate our work to the most relevant examples of argumentation frameworks that incorporate strengths.  相似文献   
19.
The digestibilities of amino acids in duodenal digesta of steers were measured using a precision-fed cecectomized rooster assay. Freeze-dried duodenal digesta from steers fed five different diets were utilized. Amino acids present in digesta of steers fed diets supplemented with corn gluten meal were more digestible than those from digesta of steers fed diets supplemented with soybean meal, blood meal, fish meal, or no true protein source. Measurements of amino acid digestibility in the cecectomized rooster were similar to those obtained previously when measured with reference to chromic oxide in steers fitted with duodenal and ileal cannulae, suggesting that the precision-fed cecectomized rooster assay is an appropriate technique for estimating small intestinal digestibility of amino acids in cattle.  相似文献   
20.
对于绝大多数微控制器时钟电路而言,硅振荡器是一种简单且有效的解决方案。与晶体和陶瓷谐振器不同,基于硅材料的定时器具有抗振动、抗撞击和抗电磁干扰的优点。同时,硅振荡器不需要严格匹配的定时元件和线路板走线。  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