全文获取类型
收费全文 | 48380篇 |
免费 | 1657篇 |
国内免费 | 13篇 |
专业分类
化学 | 29556篇 |
晶体学 | 249篇 |
力学 | 834篇 |
综合类 | 1篇 |
数学 | 8961篇 |
物理学 | 10449篇 |
出版年
2023年 | 353篇 |
2022年 | 295篇 |
2021年 | 484篇 |
2020年 | 697篇 |
2019年 | 619篇 |
2018年 | 962篇 |
2017年 | 900篇 |
2016年 | 1744篇 |
2015年 | 1445篇 |
2014年 | 1399篇 |
2013年 | 3121篇 |
2012年 | 2978篇 |
2011年 | 2825篇 |
2010年 | 1856篇 |
2009年 | 1554篇 |
2008年 | 2475篇 |
2007年 | 2258篇 |
2006年 | 2013篇 |
2005年 | 2065篇 |
2004年 | 1776篇 |
2003年 | 1492篇 |
2002年 | 1299篇 |
2001年 | 998篇 |
2000年 | 987篇 |
1999年 | 679篇 |
1998年 | 530篇 |
1997年 | 449篇 |
1996年 | 595篇 |
1995年 | 433篇 |
1994年 | 506篇 |
1993年 | 471篇 |
1992年 | 494篇 |
1991年 | 418篇 |
1990年 | 466篇 |
1989年 | 379篇 |
1988年 | 385篇 |
1987年 | 349篇 |
1986年 | 338篇 |
1985年 | 470篇 |
1984年 | 430篇 |
1983年 | 340篇 |
1982年 | 349篇 |
1981年 | 364篇 |
1980年 | 301篇 |
1979年 | 289篇 |
1978年 | 296篇 |
1977年 | 277篇 |
1976年 | 299篇 |
1974年 | 265篇 |
1973年 | 281篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The function lattice, or generalized Boolean algebra, is the set of ℓ-tuples with the ith coordinate an integer between 0 and a bound ni. Two ℓ-tuples t-intersect if they have at least t common nonzero coordinates. We prove a Hilton–Milner type theorem for systems of t-intersecting ℓ-tuples.Received September 29, 2004 相似文献
82.
Sufficient conditions which guarantee that certain linear integro-differential equation cannot have a positive solution are
established. 相似文献
83.
Máté Matolcsi 《Acta Mathematica Hungarica》2005,108(1-2):129-136
Summary He present work deals with estimations of the n-th linear polarization constant c(H)n of an n-dimensional real Hilbert space H. We provide some new lower bounds on the value of sup║y║=1 │1,y> ... n,y>│, where x1, ... ,xn are unit vectors in H. In particular, the results improve an earlier estimate of Marcus. However, the intriguing conjecture c(H) n= nn/2 remains open. 相似文献
84.
85.
No analytic solutions of the Schrödinger equation are known for the quartic anharmonic oscillator. We show in this paper that there are closely related modified quartic oscillators with the potential depending on |x| for which analytic solutions for some states exist. These results can be extended to the higher order oscillators 相似文献
86.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献
87.
Impact of the internucleotide linkage modification by inserting a methylene group to the P-O bond (—O—PO
2
—
—O— chain changed for —O—PO
2
—
—CH2—O—), on the modified oligonucleotide binding ability to the natural DNA strand was studied by molecular dynamics simulation. Complex of (dT)11 with a deoxyadenosine undecamer containing alternating modified and natural internucleotide linkage was studied as a model system. The Amber force field was completed by a set of new parameters needed to model the modified part of the nucleotide. The simulations confirmed existence of a double-helical complex the melting point of which is considerably higher than 300 K. While the thymidine (unmodified) strand possesses a B-type secondary structure, the conformation of the adenosine (modified) strand is not stable at 300 K. The -ggt conformation of the modified linkages is highly preferred, temporary jumps to the -g-gt and ggt conformations were, however, observed. 相似文献
88.
The purpose of this paper is to give the Reid ``Roundabout Theorem' for quadratic functionals with general boundary conditions.
In particular, we describe the so-called coupled point and regularity condition introduced in [16] in terms of Riccati equation
solutions.
Accepted 27 February 1996 相似文献
89.
A. Sánchez-Lavega A. Salazar A. Ocariz L. Pottier E. Gomez L.M. Villar E. Macho 《Applied Physics A: Materials Science & Processing》1997,65(1):15-22
Received: 16 September 1996/Accepted: 6 January 1997 相似文献
90.
A. Bonilla F. Pérez-González A. Stray R. Trujillo-González 《Journal d'Analyse Mathématique》1997,73(1):65-89
This paper is concerned with several approximation problems in the weighted Hardy spacesH
p(Ω) of analytic functions in the open unit disc D of the complex plane ℂ. We prove that ifX is a relatively closed subset of D, the class of uniform limits onX of functions inH
p(Ω) coincides, moduloH
p(Ω), with the space of uniformly continuous functions on a certain hull ofX which are holomorphic on its interior. We also solve the simultaneous approximation problems of describing Farrell and Mergelyan
sets forH
p(Ω), giving geometric characterizations for them. By replacing approximating polynomials by polynomial multipliers of outer
functions, our results lead to characterizations of the same sets with respect to cyclic vectors in the classical Hardy spacesH
p(D), 1 ⪯p < ∞.
Dedicated to Professor Nácere Hayek on the occasion of his 75th birthday. 相似文献