全文获取类型
收费全文 | 46344篇 |
免费 | 1541篇 |
国内免费 | 12篇 |
专业分类
化学 | 28281篇 |
晶体学 | 237篇 |
力学 | 759篇 |
综合类 | 1篇 |
数学 | 8760篇 |
物理学 | 9859篇 |
出版年
2023年 | 332篇 |
2022年 | 281篇 |
2021年 | 461篇 |
2020年 | 670篇 |
2019年 | 609篇 |
2018年 | 953篇 |
2017年 | 869篇 |
2016年 | 1693篇 |
2015年 | 1394篇 |
2014年 | 1342篇 |
2013年 | 3048篇 |
2012年 | 2874篇 |
2011年 | 2693篇 |
2010年 | 1799篇 |
2009年 | 1504篇 |
2008年 | 2365篇 |
2007年 | 2142篇 |
2006年 | 1920篇 |
2005年 | 1977篇 |
2004年 | 1706篇 |
2003年 | 1423篇 |
2002年 | 1236篇 |
2001年 | 951篇 |
2000年 | 957篇 |
1999年 | 663篇 |
1998年 | 514篇 |
1997年 | 433篇 |
1996年 | 579篇 |
1995年 | 414篇 |
1994年 | 486篇 |
1993年 | 448篇 |
1992年 | 478篇 |
1991年 | 397篇 |
1990年 | 444篇 |
1989年 | 361篇 |
1988年 | 373篇 |
1987年 | 336篇 |
1986年 | 323篇 |
1985年 | 448篇 |
1984年 | 411篇 |
1983年 | 325篇 |
1982年 | 327篇 |
1981年 | 342篇 |
1980年 | 281篇 |
1979年 | 274篇 |
1978年 | 270篇 |
1977年 | 260篇 |
1976年 | 278篇 |
1974年 | 251篇 |
1973年 | 263篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Sándor G?r?g 《Analytical sciences》2004,20(5):767-782
The development during the last 15 years and the state-of-the-art in the analysis of bulk steroid hormone drugs and hormone-like structures and pharmaceutical formulations made thereof are summarized. Other steroids (sterols, bile acids, cardiac glycosides, vitamins D) as well as biological-clinical aspects and pharmacokinetic and metabolic studies are excluded from this review. The state-of-the-art is summarized based on comparisons of monographs in the latest editions of the European Pharmacopoeia, United States Pharmacopoeia and the Japanese Pharmacopoeia. This is followed by sections dealing with new developments in the methodology for the fields of spectroscopic and spectrophotometric, chromatographic, electrophoretic and hyphenated techniques as well electroanalytical methods. The review is terminated by two problem-oriented sections: examples on impurity and degradation profiling as well as enantiomeric analysis. 相似文献
52.
53.
The influence of the sample orientation on the effective value of the hydrostatic piezoelectric coefficients d
h
(i)
of Sn2P2S6 crystals has been studied. The hydrostatic piezoelectric coefficients d
h
(1)
and d′
h
(3)
, were measured, d
h
(1)
=(244±3) pC/N and d′
h
(3)
=(92±1) pC/N. The hydrostatic piezoelectric coefficient d
h
(3)
for orthogonal axis system was calculated to be d
h
(3)
=(87±2) pC/N. The, optimal orientation of the sample has been found as (Xy l)−20°-cut. Maximal value of the effective hydrostatic piezoelectric coefficient d
h
(1)
equals 260 pC/N. Double rotated samples were also studied. The orientation of the samples insensitive to the pressure has
been found. The theoretical mean value of hydrostatic piezoelectric coefficient (d
h
)
mean
corresponding to randomly oriented Sn2P2S6 grains in a poled composite has been calculated to be (d
h
)
mean
=136 pC/N. 相似文献
54.
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
55.
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
56.
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
57.
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
58.
59.
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
60.
In this paper, we apply a three-stage-DEA model to the Spanish Professional Football League, which means separating the teams’
economic behaviour into three components: operating efficiency—of the offence and defence—athletic or operating effectiveness,
and social effectiveness. The results showed that the technical inefficiency of the defence is greater than that of the offence,
both being caused by aspects linked to the poor management of players’ abilities and by the football team’s size. Teams showed
a favourable evolution of their offensive and defensive efficiency during the 2004/2005 season and to a lesser extent in the
season before. The point system assigned by the professional football league regulations evaluates the teams’ athletic effectiveness,
but we detected that the teams with the most experience perform athletically in a more effective manner. Their social effectiveness
is strongly related to the level of play in itself and to factors linked to their PFL ranking: participation in international
competitions for important football teams; or the struggle of minor football teams to stay in the first division. 相似文献