全文获取类型
收费全文 | 50013篇 |
免费 | 1620篇 |
国内免费 | 60篇 |
专业分类
化学 | 30649篇 |
晶体学 | 275篇 |
力学 | 829篇 |
综合类 | 1篇 |
数学 | 9427篇 |
物理学 | 10512篇 |
出版年
2023年 | 342篇 |
2022年 | 369篇 |
2021年 | 630篇 |
2020年 | 754篇 |
2019年 | 712篇 |
2018年 | 999篇 |
2017年 | 906篇 |
2016年 | 1791篇 |
2015年 | 1478篇 |
2014年 | 1473篇 |
2013年 | 3204篇 |
2012年 | 3063篇 |
2011年 | 2972篇 |
2010年 | 2000篇 |
2009年 | 1721篇 |
2008年 | 2580篇 |
2007年 | 2393篇 |
2006年 | 2115篇 |
2005年 | 2150篇 |
2004年 | 1857篇 |
2003年 | 1550篇 |
2002年 | 1356篇 |
2001年 | 1031篇 |
2000年 | 1023篇 |
1999年 | 719篇 |
1998年 | 553篇 |
1997年 | 463篇 |
1996年 | 632篇 |
1995年 | 448篇 |
1994年 | 525篇 |
1993年 | 469篇 |
1992年 | 491篇 |
1991年 | 425篇 |
1990年 | 479篇 |
1989年 | 384篇 |
1988年 | 388篇 |
1987年 | 348篇 |
1986年 | 335篇 |
1985年 | 462篇 |
1984年 | 427篇 |
1983年 | 345篇 |
1982年 | 345篇 |
1981年 | 359篇 |
1980年 | 284篇 |
1979年 | 281篇 |
1978年 | 278篇 |
1977年 | 265篇 |
1976年 | 280篇 |
1974年 | 256篇 |
1973年 | 266篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
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
103.
104.
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
105.
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
106.
107.
Some of the motivations for as well as the main points of the quantization of the Nappi-Witten string in the light-cone gauge are reviewed. 相似文献
108.
Entropy analysis and wavelet transforms are used to study the Southern Oscillation index (SOI) and multivariate ENSO index (MEI) indexes for the El Niño–Southern Oscillation. Trends to large decreasing symbolic chains responsible for La Niña and interrupted increasing chains for El Niño are found in the MEI persistence series. These are all located in regions where the wavelet transforms of both indexes reveal the existence of mid-range correlations. The SOI and MEI indexes are mutually correlated in a non-trivial manner in the time. 相似文献
109.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
110.
Using dynamic data exchange to exchange information between Visual Basic and Matlab : Application to a diode array spectrophotometer 总被引:1,自引:0,他引:1
Photodiode array spectrometers are increasingly being coupled to flow analysis and separation techniques. Computer programs are needed to control the data acquisition from each photodiode and to handle the data. The Microsoft Visual Basic programming language is used along with a DLL library and dynamic data exchange (DDE) to allow communication with the MATLAB computational environment. 相似文献