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   218129篇
  免费   1909篇
  国内免费   637篇
化学   120345篇
晶体学   3284篇
力学   8383篇
综合类   6篇
数学   23602篇
物理学   65055篇
  2020年   2015篇
  2019年   2301篇
  2018年   3229篇
  2017年   3133篇
  2016年   4362篇
  2015年   2468篇
  2014年   3902篇
  2013年   9414篇
  2012年   7102篇
  2011年   8663篇
  2010年   6201篇
  2009年   6020篇
  2008年   8328篇
  2007年   8380篇
  2006年   7784篇
  2005年   7091篇
  2004年   6325篇
  2003年   5777篇
  2002年   5611篇
  2001年   6016篇
  2000年   4736篇
  1999年   3512篇
  1998年   3053篇
  1997年   3073篇
  1996年   2862篇
  1995年   2351篇
  1994年   2440篇
  1993年   2475篇
  1992年   2620篇
  1991年   2674篇
  1990年   2573篇
  1989年   2548篇
  1988年   2486篇
  1987年   2447篇
  1986年   2369篇
  1985年   3053篇
  1984年   3213篇
  1983年   2563篇
  1982年   2836篇
  1981年   2716篇
  1980年   2512篇
  1979年   2730篇
  1978年   2849篇
  1977年   2864篇
  1976年   2837篇
  1975年   2693篇
  1974年   2666篇
  1973年   2815篇
  1972年   1879篇
  1967年   1832篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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   
82.
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   
83.
84.
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   
85.
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   
86.
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   
87.
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   
88.
89.
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   
90.
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