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   111729篇
  免费   2055篇
  国内免费   516篇
电工技术   1138篇
综合类   2544篇
化学工业   16579篇
金属工艺   5368篇
机械仪表   3609篇
建筑科学   3116篇
矿业工程   651篇
能源动力   2052篇
轻工业   7505篇
水利工程   1484篇
石油天然气   492篇
武器工业   6篇
无线电   11420篇
一般工业技术   20193篇
冶金工业   8903篇
原子能技术   511篇
自动化技术   28729篇
  2023年   160篇
  2022年   559篇
  2021年   845篇
  2020年   575篇
  2019年   637篇
  2018年   14982篇
  2017年   13989篇
  2016年   10596篇
  2015年   1167篇
  2014年   1110篇
  2013年   1657篇
  2012年   4381篇
  2011年   10921篇
  2010年   9352篇
  2009年   6709篇
  2008年   7796篇
  2007年   8644篇
  2006年   899篇
  2005年   2030篇
  2004年   2027篇
  2003年   1972篇
  2002年   1326篇
  2001年   786篇
  2000年   711篇
  1999年   582篇
  1998年   2097篇
  1997年   1362篇
  1996年   974篇
  1995年   615篇
  1994年   491篇
  1993年   541篇
  1992年   230篇
  1991年   306篇
  1990年   226篇
  1989年   192篇
  1988年   215篇
  1987年   160篇
  1986年   166篇
  1985年   180篇
  1984年   133篇
  1983年   93篇
  1982年   116篇
  1981年   120篇
  1980年   114篇
  1979年   90篇
  1978年   75篇
  1977年   140篇
  1976年   226篇
  1975年   83篇
  1954年   70篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
Thomas Fincke (January 6th, 1561–April 24th, 1656), born in Flensburg (Germany), was one of the very most important and significant scientists in Denmark during the seventeenth century, a mathematician and astrologer and physician in the beginning of modern science, a representative of humanism and an influentual academic organizer. He studied in Strasbourg (since 1577) and Padua (since 1583) and received his M.D. in Basel (1587), he practised as a physician throughout his life (since 1587 or 1590) and became a professor at Copenhagen (1591). But he was best known because of his Geometriae rotundi libri XIIII (1583), a famous book on plane and spherical trigonometry, based not on Euclid but on Petrus Ramus. In this influentual work, in which Fincke introduced the terms tangent and secant and probable first noticed the Law of Tangents and the so-called Newton-Oppel-Mauduit-Simpson-Mollweide-Gauss-formula, he showed himself to be „abreast of the mathematics of his time“.   相似文献   
82.
As feature sizes shrink, transient failures of on-chip network links become a critical problem. At the same time, many applications require guarantees on both message arrival probability and response time. We address the problem of transient link failures by means of temporally and spatially redundant transmission of messages, such that designer-imposed message arrival probabilities are guaranteed. Response time minimisation is achieved by a heuristic that statically assigns multiple copies of each message to network links, intelligently combining temporal and spatial redundancy. Concerns regarding energy consumption are addressed in two ways. First, we reduce the total amount of transmitted messages, and, second, we minimise the application response time such that the resulted time slack can be exploited for energy savings through voltage reduction. The advantages of the proposed approach are guaranteed message arrival probability and guaranteed worst case application response time.  相似文献   
83.
The present studies demonstrated the moderation of self-construal orientation on mimicry. Recent research has indicated that an interdependent self-construal is associated with assimilation of the other to the self whereas an independent self-construal is associated with minimizing the influence of others on the self (H. R. Markus & S. Kitayama, 1991; D. Stapel & W. Koomen, 2001). Therefore, the authors hypothesized that an interdependent self-construal would be associated with more mimicry than an independent self-construal. When self-construal orientations were experimentally primed. as in Studies 1 and 2, independent self-construals produced less nonconscious mimicry than interdependent self-construals. When self-construals were examined as cultural differences with either a chronically dominant independent (Americans) or interdependent (Japanese) construal of the self, these results were replicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
84.
A fully-dense Cu-75 vol pct ZrW2O8 metal matrix composite was fabricated by hot isostatic pressing of Cu-coated ZrW2O8 particles. A small amount of the high-pressure γ-ZrW2O8 phase was created during the cooldown and depressurization following densification; near complete transformation to γ-ZrW2O8 was achieved by subsequent cold isostatic pressing. The thermal expansion behavior of the composite between 25°C and 325°C was altered by the cold isostatic pressing treatment, and also depended on the length of time that had passed between thermal cycles. The measured thermal expansion coefficients within specific temperature ranges varied from −6·10−6 K−1 to far above the thermal expansion coefficient of the copper matrix. The complex temperature-dependent expansion/contraction behavior could be justified by considering the evolution of phase transformations taking place in the ZrW2O8 phase, which were observed by in-situ synchrotron X-ray diffraction measurements.  相似文献   
85.
The DNA molecule is modeled as an elastic rod with bending and twisting rigidities, subjected to external tension and twist applied at one end, the other end being clamped. We study the plectonemic equilibrium of such a rod, taking into account the impenetrability constraint. Numerical solutions of this boundary value problem have previously shown that purely elastic models can reproduce the supercoiling response of the DNA molecule. Using a variational approach, we derive analytical formulae for the elastic response of the filament, and extend former numerical results.  相似文献   
86.
87.
Critical Shear Stress of Bimodal Sediment in Sand-Gravel Rivers   总被引:1,自引:0,他引:1  
A new model for the critical shear stress and the transport of graded sediment is presented. The model is based on the size distribution of the bed surface and can be used to compute sediment transport rates in numerical simulations with an active layer model. This model makes a distinction between unimodal and bimodal sediments. It is assumed that all size fractions of unimodal sediments have the same critical shear stress while there is selective transport for the gravel fractions of bimodal sediments. A recently published laboratory transport data set is used to calibrate our model.  相似文献   
88.
89.
90.
We show new upper bounds for problems in the W-hierarchy of fixed-parameter complexity. A crucial ingredient of our proofs is an extension to the W-RAM model, which permits more-powerful operations but remains equivalent to the original. We use the extended model to give new upper bounds for Subsetsum, Maximum Irredundant Set, and various problems concerning intersection of finite-state machines.  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