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   217740篇
  免费   1842篇
  国内免费   626篇
化学   119162篇
晶体学   3286篇
力学   8427篇
综合类   6篇
数学   23887篇
物理学   65440篇
  2020年   2021篇
  2019年   2302篇
  2018年   3280篇
  2017年   3184篇
  2016年   4375篇
  2015年   2442篇
  2014年   3950篇
  2013年   9505篇
  2012年   7016篇
  2011年   8566篇
  2010年   6159篇
  2009年   5996篇
  2008年   8219篇
  2007年   8286篇
  2006年   7695篇
  2005年   6971篇
  2004年   6196篇
  2003年   5669篇
  2002年   5550篇
  2001年   5977篇
  2000年   4715篇
  1999年   3502篇
  1998年   3047篇
  1997年   3056篇
  1996年   2851篇
  1995年   2341篇
  1994年   2444篇
  1993年   2473篇
  1992年   2619篇
  1991年   2679篇
  1990年   2591篇
  1989年   2562篇
  1988年   2494篇
  1987年   2464篇
  1986年   2385篇
  1985年   3066篇
  1984年   3216篇
  1983年   2585篇
  1982年   2855篇
  1981年   2728篇
  1980年   2539篇
  1979年   2747篇
  1978年   2876篇
  1977年   2894篇
  1976年   2873篇
  1975年   2721篇
  1974年   2697篇
  1973年   2829篇
  1972年   1892篇
  1967年   1841篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Gurbatov  S. N.  Pelinovsky  E. N. 《Doklady Physics》2020,65(8):269-272
Doklady Physics - In this paper, we study the statistical characteristics of the Riemann wave and the integral of it. Such problems arise in the physics of fronts’ propagation, in particular,...  相似文献   
102.
The preparation of new ring opening metathesis polymerization (ROMP) monomers using a 1,3‐dipolar cycloaddition between aryl azides and norbornadiene is described. Various norbornenetriazolines, obtained through a solvent‐and catalyst‐free reaction, can subsequently be incorporated into polymer backbones through ROMP reactions. Furthermore, thermal decomposition of the triazoline moiety can allow for further polymer functionalization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2357–2362  相似文献   
103.
104.
G.E. Farr 《Discrete Mathematics》2019,342(5):1510-1519
This paper continues the study of combinatorial properties of binary functions — that is, functions f:2E? such that f(0?)=1, where E is a finite set. Binary functions have previously been shown to admit families of transforms that generalise duality, including a trinity transform, and families of associated minor operations that generalise deletion and contraction, with both these families parameterised by the complex numbers. Binary function representations exist for graphs (via the indicator functions of their cutset spaces) and indeed arbitrary matroids (as shown by the author previously). In this paper, we characterise degenerate elements – analogues of loops and coloops – in binary functions, with respect to any set of minor operations from our complex-parameterised family. We then apply this to study the relationship between binary functions and Tutte’s alternating dimaps, which also support a trinity transform and three associated minor operations. It is shown that only the simplest alternating dimaps have binary representations of the form we consider, which seems to be the most direct type of representation. The question of whether there exist other, more sophisticated types of binary function representations for alternating dimaps is left open.  相似文献   
105.
Ganenkova  E. G.  Starkov  V. V. 《Mathematical Notes》2019,105(1-2):216-226

Differential inequalities for polynomials generalizing the well-known Smirnov, Rahman, Schmeisser, and Bernstein inequalities are obtained.

  相似文献   
106.
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar...  相似文献   
107.
Journal of Structural Chemistry - An analysis is presented for the results obtained in the studies initiated by A. E. Shvelashivili, Corresponding Member, Academy of Sciences of Georgia, and...  相似文献   
108.
109.
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis.  相似文献   
110.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  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