全文获取类型
收费全文 | 5196篇 |
免费 | 790篇 |
国内免费 | 345篇 |
专业分类
化学 | 4340篇 |
晶体学 | 58篇 |
力学 | 524篇 |
综合类 | 48篇 |
数学 | 331篇 |
物理学 | 1030篇 |
出版年
2024年 | 8篇 |
2023年 | 48篇 |
2022年 | 228篇 |
2021年 | 299篇 |
2020年 | 241篇 |
2019年 | 150篇 |
2018年 | 185篇 |
2017年 | 165篇 |
2016年 | 285篇 |
2015年 | 268篇 |
2014年 | 311篇 |
2013年 | 523篇 |
2012年 | 336篇 |
2011年 | 318篇 |
2010年 | 228篇 |
2009年 | 319篇 |
2008年 | 282篇 |
2007年 | 310篇 |
2006年 | 282篇 |
2005年 | 263篇 |
2004年 | 233篇 |
2003年 | 214篇 |
2002年 | 147篇 |
2001年 | 89篇 |
2000年 | 84篇 |
1999年 | 60篇 |
1998年 | 57篇 |
1997年 | 58篇 |
1996年 | 64篇 |
1995年 | 38篇 |
1994年 | 28篇 |
1993年 | 31篇 |
1992年 | 41篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有6331条查询结果,搜索用时 31 毫秒
121.
F. Munari A. Trisciani G. Mapelli S. Trestianu K. Grob J. M. Colin 《Journal of separation science》1985,8(9):601-606
Two-dimensional chromatography of gasoline by on-line coupled HPLC-HRGC, as described in this paper, allows separate GC analysis of paraffins and aromatics. The GC system contains a retention gap of only 10 m length for introducing HPLC fractions of 100 μl volume. This becomes possible through evaporation of part of the solvent during introduction of the HPLC eluent. This “partially concurrent solvent evaporation” technique allows transfer of large volumes of HPLC eluent into relatively short retention gaps, maintaining the full efficiency of the solvent effects in reconcentrating the bands of the early eluted solutes. 相似文献
122.
An air-segmented continuous-flow method has been developed for the determination of molybdenum at ultra trace levels using
the catalytic effect of molybdate during the oxidation of L-ascorbic acid by hydrogen peroxide. Incorporation of an on-line
ion exchange column improved the tolerance limit for various ions. The detection limits with and without the column were 64 pmol L−1 and 17 pmol L−1, and the reproducibilities at 10 nmol L−1 were 2.1% and 0.2%, respectively. The proposed method was applied to the determination of molybdenum in seawater and lake
water as well as in rock and sediment samples. This method has the highest sensitivity among the available literature to our
knowledge, and is also convenient for routine analysis of molybdenum in various natural samples.
Author for correspondence. E-mail: masahito.sugiyama@ sojin0206.mbox.media.kyoto-u.ac.jp
Received October 23, 2002; accepted January 28, 2003
Published online May 19, 2003 相似文献
123.
The full configuration interaction method in the space of fractionally occupied unrestricted natural orbitals (UNO-CAS method)
is extended to excited states as well as to strongly correlated and reactive systems with large active spaces. This is accomplished
by␣using restricted active space (RAS) wave functions introduced by Olsen et al. [(1988) J Chem Phys 89: 2185] and using the
UNOs without the expensive orbital optimization step. In RAS, the space of active orbitals is subdivided into three groups:
a group with essentially doubly occupied orbitals (RAS1), the usual CAS space (RAS2), and a space with weakly occupied active
orbitals (RAS3). We select these spaces on the basis of the occupation numbers of the UNOs. All possible electron distributions
are allowed in the usual CAS space, but the number of vacancies is limited in RAS1 and the number of electrons is limited
in RAS3. We discuss an efficient algorithm for generating a RAS wave function. This is based on the Handy-Knowles determinantal
expansion with an addressing scheme adopted for the restricted expansion. Results for both ground and excited states of azulene
and free base porphyrin are presented.
Received: 16 July 1998 / Accepted: 7 August 1998 / Published online: 19 October 1998 相似文献
124.
125.
126.
A new synthetic method for the preparation of allyl amines has been developed. The key steps of this method are enantioselective addition of diethylzinc and [1,3]-chirality transfer through the [3.3] sigmatropic rearrangement of allyl cyanates. Stereocontrolled syntheses of lentiginosine (1) and polyoxamic acid derivative 2 from a common intermediate 7 derived from D-tartaric acid (8), have been accomplished. 相似文献
127.
128.
129.
Consider a kind of Hermit interpolation for scattered data of 3D by trivariate polynomial natural spline,such that the objective energy functional (with natural boundary conditions) is minimal.By the s... 相似文献
130.