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   5935篇
  免费   210篇
  国内免费   6篇
电工技术   55篇
综合类   10篇
化学工业   1236篇
金属工艺   92篇
机械仪表   104篇
建筑科学   293篇
矿业工程   23篇
能源动力   186篇
轻工业   420篇
水利工程   44篇
石油天然气   39篇
武器工业   2篇
无线电   557篇
一般工业技术   964篇
冶金工业   1298篇
原子能技术   24篇
自动化技术   804篇
  2022年   56篇
  2021年   102篇
  2020年   65篇
  2019年   87篇
  2018年   98篇
  2017年   94篇
  2016年   101篇
  2015年   98篇
  2014年   152篇
  2013年   401篇
  2012年   251篇
  2011年   329篇
  2010年   217篇
  2009年   252篇
  2008年   253篇
  2007年   278篇
  2006年   227篇
  2005年   183篇
  2004年   146篇
  2003年   148篇
  2002年   147篇
  2001年   121篇
  2000年   97篇
  1999年   107篇
  1998年   224篇
  1997年   169篇
  1996年   136篇
  1995年   131篇
  1994年   85篇
  1993年   83篇
  1992年   72篇
  1991年   64篇
  1990年   82篇
  1989年   58篇
  1988年   60篇
  1987年   56篇
  1986年   51篇
  1985年   67篇
  1984年   71篇
  1983年   56篇
  1982年   53篇
  1981年   47篇
  1980年   59篇
  1979年   61篇
  1978年   61篇
  1977年   53篇
  1976年   71篇
  1975年   41篇
  1974年   38篇
  1973年   44篇
排序方式: 共有6151条查询结果,搜索用时 15 毫秒
21.
With the aid of automated reasoning techniques, we show that all previously known short single axioms for odd exponent groups are special cases of one general schema. We also demonstrate how to convert the proofs generated by an automated reasoning system into proofs understandable by a human.Authors supported by NSF Grant DMS-9100665  相似文献   
22.
Measuring knowledge transfer between fields of science   总被引:4,自引:2,他引:2  
In this paper we report on the results of an exploratory study of knowledge exchange between disciplines and subfields of science, based on bibliometric methods. The goal of this analysis is twofold. Firstly, we consider knowledge exchange between disciplines at a global level, by analysing cross-disciplinary citations in journal articles, based on the world publication output in 1999. Among others a central position of the Basic Life Sciences within the Life Sciences and of Physics within the Exact Sciences is shown. Limitations of analyses of interdisciplinary impact at the journal level are discussed. A second topic is a discussion of measures which may be used to quantify the rate of knowledge transfer between fields and the importance of work in a given field or for other disciplines. Two measures are applied, which appear to be proper indicators of impact of research on other fields. These indicators of interdisciplinary impact may be applied at other institutional levels as well. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
23.
In this work, a method is developed for smoothing three‐dimensional contact surfaces. The method can be applied to both regular and irregular meshes. The algorithm employs Gregory patches to interpolate finite element nodes and provide tangent plane continuity between adjacent patches. The resulting surface interpolation is used to calculate gaps and contact forces, in a variationally consistent way, such that contact forces due to normal and frictional contact vary smoothly as slave nodes transition from one patch to the next. This eliminates the ‘chatter’ which typically occurs in a standard contact algorithm when a slave node is situated near a master facet edge. The elimination of this chatter provides a significant improvement in convergence behaviour, which is illustrated by a number of numerical examples. Furthermore, smoothed surfaces also provide a more accurate representation of the actual surface, such that resulting stresses and forces can be more accurately computed with coarse meshes in many problems. This fact is also demonstrated by the numerical examples. Published in 2002 by John Wiley & Sons, Ltd.  相似文献   
24.
Two studies examined the relationship between the content of a self-threat and the attractiveness of available self-affirmations (C. M. Steele, 1988). After self-threat was induced by means of a cognitive dissonance procedure, participants' choices for affirmations were examined in order to explore whether the attractiveness of a given affirmation depends on its relevance to the threatened domain of the self-concept. The authors hypothesized that when faced with a threat to a specific self-conception or standard, individuals may forego affirmations within the threatened self-concept domain in favor of affirmations of unrelated, compensatory domains. Both studies supported this hypothesis and further suggested that such selective self-affirmation can lead individuals to modify their self-concepts by identifying with self-aspects that justify dissonant behavior and by disidentifying with the standards that such behavior violates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
Merging uncertain information with semantic heterogeneity in XML   总被引:1,自引:1,他引:0  
Semistructured information can be merged in a logic-based framework [6, 7]. This framework has been extended to deal with uncertainty, in the form of probability values, degrees of beliefs, or necessity measures, associated with leaves (i.e. textentries) in the XML documents [3]. In this paper we further extend this approach to modelling and merging uncertain information that is defined at different levels of granularity of XML textentries, and to modelling and reasoning with XML documents that contain semantically heterogeneous uncertain information on more complex elements in XML subtrees. We present the formal definitions for modelling, propagating and merging semantically heterogeneous uncertain information and explain how they can be handled using logic-based fusion techniques. Anthony Hunter received a B.Sc. (1984) from the University of Bristol and an M.Sc. (1987) and Ph.D. (1992) from Imperial College, London. He is currently a reader in the Department of Computer Science at University College London. His main research interests are: Knowledge representation and reasoning, Analysing inconsistency, Argumentation, Default reasoning and Knowledge Fusion. Weiru Liu is a senior lecturer at the School of Computer Science, Queen's University Belfast. She received her B.Sc. and M.Sc. degrees in Computer Science from Jilin University, P.R China, and her Ph.D. degree in Artificial Intelligence from the University of Edinburgh. Her main research interests include reasoning under uncertainty, knowledge representation and reasoning, uncertain knowledge and information fusion, and knowledge discovery in databases. She has published over 50 journal and conference papers in these areas.  相似文献   
26.
Nonpharmacological cues associated with drug intake may influence subjective and reinforcing effects of those drugs. Social drinkers (N = 80) participated in 2 sessions in which they rated and then consumed ad lib their preferred beer (with participants blind to brand). Visual and olfactory stimuli were obscured during 1 session (blocked) and not obscured during the other (unblocked). Dependent measures included ratings of "liking", "want another", and "desire to drink"; subjective mood; and ad lib beer consumption (reinforcement). Most ratings and ad lib consumption were lower during the blocked versus the unblocked condition. There were no interactions of blockade condition with sex and no effect of blockade on mood. These findings show that nonpharmacological stimuli associated with alcohol consumption influence alcohol's subjective and reinforcing effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
27.
We explain why the methods in Langridge, Hart and Crampin [Comput. Phys. Commun. 134 (2001) 78] suffice for the evaluation of the lattice sums entering the Madelung matrix describing multipole interactions in systems with one-dimensional translational periodicity.  相似文献   
28.
OBJECTIVE: To determine the effect of area postrema AP on DOCA-salt induced hypertension in rat, with emphasis on renal hemodynamics. METHOD: Blood pressure, salt and water balances and renal hemodynamics were observed in AP ablated and sham-operated rats treated with DOCA-salt. RESULTS: In AP intact (API) rats, after one week of DOCA-salt treatment BP began elevating to statistical significance at the end of the second week (MAP 15.9 +/- 0.7 vs. 13.5 +/- 0.5 kPa), followed by a plateau period from the third to fifth week. In AP ablated (APX) rats, BP raised during the first week of DOCA-salt treatment. However, the elevation gradually disappeared and BP returned to baseline at the fifth week. Sodium balance study showed that DOCA-salt treatment induced significant sodium retention in API rat, while the sodium metabolism remained stable in APX group except in the first week. Basal renal hemodynamic parameters (GFR, RPF, UNaV, UV) were not changed at neither the beginning nor the end of the study. However, a small dose of hypertonic saline (7% NaCl 0.3 ml) injection caused a brisk rising of these four parameters in APX but not API group. CONCLUSION: AP plays an important role in normal salt and water metabolism and might be involved in pathogenesis of DOCA-salt hypertension through regulation for renal hemodynamics and body fluid homeostasis.  相似文献   
29.
We studied 100 healthy children looking for lactose malabsortion. We performed in all of them the lactose breath test. We found a 10% with lactose malabsortion. There was no correlation between lactose breath test and fecal reducing substances.  相似文献   
30.
BACKGROUND: Primary care has an important role to play in the prevention and management of the human immunodeficiency virus (HIV). It has been suggested that homosexual men experience a variety of problems in relation to primary care. AIM: As part of a larger study, it was decided to examine the extent to which a sample of homosexually active men experienced difficulties in general practice and whether they consulted their general practitioner for problems related to HIV or the acquired immune deficiency syndrome (AIDS). METHOD: Homosexual men were recruited for interview in 1991-92 from a variety of sources including genitourinary clinics and homosexual organizations. RESULTS: Of 623 men registered with a general practitioner 44% had not informed their general practitioner of their sexual orientation and 44% of the 77 men who were HIV antibody positive, as confirmed by the study, had not informed their general practitioner of this fact. Men who viewed their practice as unsympathetic towards homosexual men were less likely to have informed their general practitioner of their sexual orientation or HIV status. The majority of men (87%) nevertheless viewed primary care as an appropriate source of HIV/AIDS advice. CONCLUSION: There is considerable scope for improvement in the acceptability of general practice to homosexual men.  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