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   148870篇
  免费   1476篇
  国内免费   351篇
化学   79423篇
晶体学   1478篇
力学   6587篇
综合类   7篇
数学   15083篇
物理学   48119篇
  2020年   1111篇
  2019年   1169篇
  2018年   1468篇
  2017年   1436篇
  2016年   2392篇
  2015年   1518篇
  2014年   2381篇
  2013年   6256篇
  2012年   4861篇
  2011年   6170篇
  2010年   4219篇
  2009年   4220篇
  2008年   5626篇
  2007年   5660篇
  2006年   5363篇
  2005年   4936篇
  2004年   4351篇
  2003年   3767篇
  2002年   3577篇
  2001年   4162篇
  2000年   3100篇
  1999年   2341篇
  1998年   2039篇
  1997年   2028篇
  1996年   1828篇
  1995年   1838篇
  1994年   1840篇
  1993年   1670篇
  1992年   1940篇
  1991年   2073篇
  1990年   1867篇
  1989年   1872篇
  1988年   1822篇
  1987年   1717篇
  1986年   1656篇
  1985年   2154篇
  1984年   2299篇
  1983年   1866篇
  1982年   2051篇
  1981年   1937篇
  1980年   1857篇
  1979年   2009篇
  1978年   2177篇
  1977年   2050篇
  1976年   2090篇
  1975年   2004篇
  1974年   2059篇
  1973年   2044篇
  1972年   1341篇
  1971年   1197篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the...  相似文献   
2.
Physics of Atomic Nuclei - The results of complex calculation of the solution pulsed nuclear reactor (PNR) VIR-2M are presented. The simulation of the fuel solution dynamics is described, and...  相似文献   
3.
Berny  M.  Archer  T.  Beauchêne  P.  Mavel  A.  Hild  F. 《Experimental Mechanics》2021,61(5):771-790

Background Uncertainty quantifications are required for any measurement result to be meaningful.

Objective The present work aims at deriving and comparing a priori estimates of displacement uncertainties in T3-stereocorrelation for a setup to perform high temperature tests.

Methods Images acquired prior to the actual experiment (i.e.,at room temperature) were registered using 3-noded triangular elements (T3-stereocorrelation) to determine displacement uncertainties for different positions of the experimental setup.

Results The displacement uncertainties were then compared to their a priori estimates.

Conclusions For the analyzed experiment, it is shown that noise floor estimates only differed by a factor 2 when compared to a posteriori measurements of standard displacement uncertainties.

  相似文献   
4.
Taherian  A.  Toutounian  F. 《Numerical Algorithms》2021,88(4):1831-1850
Numerical Algorithms - In this paper, the block generalized product-type bi-conjugate gradient (GPBi-CG) method for solving large, sparse nonsymmetric linear systems of equations with multiple...  相似文献   
5.
Marconi  J.  Tiso  P.  Quadrelli  D. E.  Braghin  F. 《Nonlinear dynamics》2021,104(4):3039-3063
Nonlinear Dynamics - We present an enhanced version of the parametric nonlinear reduced-order model for shape imperfections in structural dynamics we studied in a previous work. In this model, the...  相似文献   
6.
Mechanics of Composite Materials - Aiming at the phenomenon of delamination and serious tool wear when processing carbon-carbon composite materials by traditional mechanical tools, an abrasive...  相似文献   
7.
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have...  相似文献   
8.
Ferrarini  A.  Finotello  A.  Salsano  G.  Auricchio  F.  Palombo  D.  Spinella  G.  Pane  B.  Conti  M. 《Acta Mechanica Sinica》2021,37(7):1192-1192
Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2  相似文献   
9.
Low-pressure gas discharge plasmas are known to be strongly affected by the presence of small dust particles. This issue plays a role in the investigations of dust particle-forming plasmas, where the dust-induced instabilities may affect the properties of synthesized dust particles. Also, gas discharges with large amounts of microparticles are used in microgravity experiments, where strongly coupled subsystems of charged microparticles represent particle-resolved models of liquids and solids. In this field, deep understanding of dust–plasma interactions is required to construct the discharge configurations which would be able to model the desired generic condensed matter physics as well as, in the interpretation of experiments, to distinguish the plasma phenomena from the generic condensed matter physics phenomena. In this review, we address only physical aspects of dust–plasma interactions, that is, we always imply constant chemical composition of the plasma as well as constant size of the dust particles. We also restrict the review to two discharge types: dc discharge and capacitively coupled rf discharge. We describe the experimental methods used in the investigations of dust–plasma interactions and show the approaches to numerical modelling of the gas discharge plasmas with large amounts of dust. Starting from the basic physical principles governing the dust–plasma interactions, we discuss the state-of-the-art understanding of such complicated, discharge-type-specific phenomena as dust-induced stratification and transverse instability in a dc discharge or void formation and heartbeat instability in an rf discharge.  相似文献   
10.
In this paper we analyze some classes of abstract simplicial complexes relying on algebraic models arising from module theory. To this regard, we consider a left-module on a unitary ring and find models of abstract complexes and related set operators having specific regularity properties, which are strictly interrelated to the algebraic properties of both the module and the ring.Next, taking inspiration from the aforementioned models, we carry out our analysis from modules to arbitrary sets. In such a more general perspective, we start with an abstract simplicial complex and an associated set operator. Endowing such a set operator with the corresponding properties obtained in our module instances, we investigate in detail and prove several properties of three subclasses of abstract complexes.More specifically, we provide uniformity conditions in relation to the cardinality of the maximal members of such classes. By means of the notion of OSS-bijection, we prove a correspondence theorem between a subclass of closure operators and one of the aforementioned families of abstract complexes, which is similar to the classic correspondence theorem between closure operators and Moore systems. Next, we show an extension property of a binary relation induced by set systems when they belong to one of the above families.Finally, we provide a representation result in terms of pairings between sets for one of the three classes of abstract simplicial complexes studied in this work.  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