全文获取类型
收费全文 | 173336篇 |
免费 | 18671篇 |
国内免费 | 18677篇 |
专业分类
化学 | 127158篇 |
晶体学 | 2920篇 |
力学 | 8527篇 |
综合类 | 1654篇 |
数学 | 32705篇 |
物理学 | 37720篇 |
出版年
2024年 | 251篇 |
2023年 | 1532篇 |
2022年 | 2972篇 |
2021年 | 3241篇 |
2020年 | 3722篇 |
2019年 | 5343篇 |
2018年 | 4690篇 |
2017年 | 5689篇 |
2016年 | 6267篇 |
2015年 | 7975篇 |
2014年 | 8916篇 |
2013年 | 15022篇 |
2012年 | 11012篇 |
2011年 | 11035篇 |
2010年 | 9281篇 |
2009年 | 10742篇 |
2008年 | 11338篇 |
2007年 | 11015篇 |
2006年 | 10328篇 |
2005年 | 9160篇 |
2004年 | 8253篇 |
2003年 | 7588篇 |
2002年 | 7527篇 |
2001年 | 5353篇 |
2000年 | 5090篇 |
1999年 | 3844篇 |
1998年 | 3041篇 |
1997年 | 2531篇 |
1996年 | 2240篇 |
1995年 | 2076篇 |
1994年 | 1897篇 |
1993年 | 1584篇 |
1992年 | 1533篇 |
1991年 | 1178篇 |
1990年 | 925篇 |
1989年 | 794篇 |
1988年 | 718篇 |
1987年 | 538篇 |
1986年 | 455篇 |
1985年 | 531篇 |
1984年 | 502篇 |
1983年 | 243篇 |
1982年 | 396篇 |
1981年 | 469篇 |
1980年 | 357篇 |
1979年 | 344篇 |
1978年 | 256篇 |
1977年 | 235篇 |
1976年 | 180篇 |
1973年 | 129篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
本文首先将文[1]中的BLD映射推广为弱(L1,L2)-BLD映射,并证明了如下正则性结果:存在两个可积指数 P1=P1(n,L1,L2)<n<q1=q1(n,L1,L2),使得对任意弱(L1,L2)-BLD映射f∈(Ω,Rn),都有f∈(Ω,Rn),即f为(L1,L2)-BLD映射. 相似文献
102.
In this note we show how coverings induced by voltage assignments can be used to produce packings of disjoint copies of the Hoffman‐Singleton graph into K50. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 408–412, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10049 相似文献
103.
A. D. Matveev 《Journal of Applied Mechanics and Technical Physics》2003,44(5):721-726
Modified three-dimensional formulations of bending problems of homogeneous elastic plates and beams are considered. Modification of the known three-dimensional formulations reduces to using additional constraints imposed on displacement functions. An advantage of the formulations proposed is that complex fixing conditions of plates and beams can be taken into account. 相似文献
104.
Fillmore在[1]中得到一个定理:设A,T是Banach空间X上的线性变换,A有界,若Lat(A) Lat(T)且AT=TA,则T是A的多项式.在本文里,以此作为引理,讨论了Banach空间上可逆线性变换A在什么情况下,A-1可表示为A的多项式.本文最主要的结论是定理3.4:设X是Banach空间,A是X上的有界线性变换,且可逆,则A-1是A的多项式当且仅当A-1是A的局部多项式. 相似文献
105.
A. Khrennikov 《Annalen der Physik》2003,12(10):575-585
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations. 相似文献
106.
We investigate the dynamics of the Λ system driven by two resonant laser fields in presence of dissipation for coupling strengths where the rotating‐wave approximation starts to break down. This regime is characterised by Rabi frequencies being approximately equal or smaller than the field frequencies. A systematic procedure to obtain an expansion for the solution of the Bloch evolution equations of the system is presented. The lowest contribution results to be the well‐known rotating‐wave approximation. The method is based on a semi‐classical treatment of the problem, and its predictions are interpreted fully quantum mechanically. The theory is illustrated by a detailed study of the disappearance of coherent population trapping as the intensities of the fields increase. 相似文献
107.
A (w,r) cover‐free family is a family of subsets of a finite set such that no intersection of w members of the family is covered by a union of r others. A (w,r) superimposed code is the incidence matrix of such a family. Such a family also arises in cryptography as the concept of key distribution pattern. In the present paper, we give some new results on superimposed codes. First we construct superimposed codes from super‐simple designs which give us results better than superimposed codes constructed by other known methods. Next we prove the uniqueness of the (1,2) superimposed code of size 9 × 12, the (2,2) superimposed code of size 14 × 8, and the (2,3) superimposed code of size 30 × 10. Finally, we improve numerical values of upper bounds for the asymptotic rate of some (w,r) superimposed codes. © 2004 Wiley Periodicals, Inc. 相似文献
108.
What Is Its Real Existing Form?——Theoretical and Experimental Studies on 2-Mercaptobenzothiazole 总被引:1,自引:0,他引:1
1 INTRODUCTION The study of heterocyclic molecules with aroma- tic rings and their absorptions on metals is of con- siderable importance from both theoretical and te- chnological points of view. These molecules are in- teresting because of their applications as corrosion inhibitors and flotation collectors, and their abilities to form self-assembly layers[1]. 2-Mercaptobenzo- thiazole (C7H5NS2, in the following MBT) is an important heterocyclic molecule, which can be used as corrosion … 相似文献
109.
110.
Various 2-substituted indoles were prepared by heteroannulation of o-iodoanilines and terminal alkynes in a one-pot reaction with a Pd(II)-NaY zeolite catalyst. The product formation largely depended on the solvent, base, and reaction temperature. The recycled catalyst showed good reusability in the heteroannulation reaction. 相似文献