全文获取类型
收费全文 | 4891篇 |
免费 | 84篇 |
国内免费 | 11篇 |
专业分类
化学 | 2799篇 |
晶体学 | 9篇 |
力学 | 56篇 |
综合类 | 1篇 |
数学 | 505篇 |
物理学 | 1616篇 |
出版年
2020年 | 51篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2016年 | 55篇 |
2015年 | 53篇 |
2014年 | 61篇 |
2013年 | 98篇 |
2012年 | 121篇 |
2011年 | 159篇 |
2010年 | 102篇 |
2009年 | 75篇 |
2008年 | 138篇 |
2007年 | 172篇 |
2006年 | 166篇 |
2005年 | 155篇 |
2004年 | 150篇 |
2003年 | 133篇 |
2002年 | 115篇 |
2001年 | 114篇 |
2000年 | 92篇 |
1999年 | 86篇 |
1998年 | 76篇 |
1997年 | 68篇 |
1996年 | 85篇 |
1995年 | 91篇 |
1994年 | 97篇 |
1993年 | 94篇 |
1992年 | 110篇 |
1991年 | 73篇 |
1990年 | 60篇 |
1989年 | 53篇 |
1988年 | 66篇 |
1987年 | 68篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 61篇 |
1983年 | 48篇 |
1982年 | 68篇 |
1981年 | 58篇 |
1980年 | 52篇 |
1979年 | 53篇 |
1978年 | 53篇 |
1977年 | 50篇 |
1976年 | 43篇 |
1975年 | 48篇 |
1974年 | 48篇 |
1973年 | 63篇 |
1972年 | 31篇 |
1971年 | 40篇 |
1956年 | 31篇 |
排序方式: 共有4986条查询结果,搜索用时 15 毫秒
101.
102.
J. Rico B. Rubio J. L. Tain A. Gadea J. Bea L. M. Garcia-Raffi O. Tengblad P. Kleinheinz R. Menegazzo R. Wirowski P. von Brentano G. Siems J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(2):245-246
In a high sensitivity (,2n) in-beam study of
62
144
Sm82, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d
5
2/–2
, d
5
2/–1
g
7
2/–1
, g
7
2/–2
, h11/2d
5
2/–1
and the 9– to 4– members of the h11·/2g
7
2/–1
multiplet.Work partially supported by CICYT (Spain). 相似文献
103.
104.
105.
106.
107.
C(alpha)-Formylglycine, the catalytic amino acid residue in the active site of sulfatases, is generated by post-translational modification of a cysteine or serine residue. We describe a highly sensitive procedure for the detection of C(alpha)-formylglycine-containing peptides in tryptic digests of sulfatase proteins. The protocol is based on the formation of hydrazone derivatives of C(alpha)-formylglycine-containing peptides when using dinitrophenylhydrazine as a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The hydrazone derivatives desorb and ionize with high efficiency and can be detected in the sub-femtomole range. The presence of C(alpha)-formylglycine is indicated by a mass increment of 180.13 u, corresponding to the hydrazone moiety, and also by a unique C-terminal fragment ion, characteristic of sulfatases, that becomes prominent in MALDI post-source decay mass spectra of the hydrazone derivatives. 相似文献
108.
Omar Deeb Prof. Monika Leibscher Dr. Jörn Manz Prof. Wulf von Muellern Tamar Seideman Prof. 《Chemphyschem》2007,8(2):322-328
We propose an approach for separating nuclear spin isomers with coherent light and illustrate it by numerical calculations using fulvene as a model system. The scheme employs the equivalence of torsion and interchange of equivalent H-atoms in a class of molecules of which fulvene is a simple example. The exchange symmetry couples with the rotational symmetry to produce a spatial distinction between the two photo-excited nuclear spin isomers, and wavepacket interferometry is applied to separate the species. 相似文献
109.
M. Rutzen S. Kakar C. Rienecker R. von Pietrowski T. Möller 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,38(1):89-90
A new method for the production of cold free clusters is presented. A beam of large rare gas clusters is passed through a low pressure atomic gas. The gas atoms are picked up by the rare gas clusters whereby they condense. A complete evaporation of rare gas atoms from the newly formed clusters then follows once the number of captured particles becomes sufficiently large. The method is demonstrated for Xe clusters with size up to 500 atoms per cluster but it should work for most materials, including the refractory materials. 相似文献
110.
Fokin AA Kiran B Bremer M Yang X Jiao H von Rague Schleyer P Schreiner PR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(9):1615-1628
A series of charged and neutral four-center n-electron (4c-ne, n = 1-4) molecules based on the adamantane framework, but which include combinations of boron, nitrogen, and phosphorus atoms at bridgehead positions, were studied computationally at the B3LYP/6-31G* level of density functional theory (DFT). The three-dimensional aromaticity, observed earlier for the 1,3,5,7-bisdehydroadamantane dication (1), is found to be general for 4c-2e electron systems. The degree of electron delocalization, evaluated by energetic, geometric, and various magnetic criteria, is quite independent of the molecular symmetry (point groups vary from Td to Cs), the degeneracy of the orbitals, the molecular charges, and the nature of the atoms participating in the delocalized bonding. Although the multiple positive (e.g., in 1 and some of the heteroatom systems) and multiple negative charges are strongly repulsive, the rigid adamantane frameworks help hold the bridgehead atoms within bonding distances with the fewer available electrons. The corresponding 4c-1e doublets are approximately half as aromatic as the 4c-2e singlets based on the same criteria. However, the three-electron systems may either adopt distorted but still four-center delocalized structures, or alternative 3c-2e two-dimensional arrangements in which the fourth bridgehead atom is more distant. There is no need to derive special rules for each point group for 4c-ne systems. Although the three-dimensional stabilization is computed to be quite appreciable, ranging between 10 and 50 kcalmol(-1), this delocalization energy is generally not sufficient to overcome distortion due to strain in higher homologues of 1 and in analogous noncage systems. Among the various 4c-2e homoadamantanedehydro dications studied, only the 1,8-dehydrohomoadamandiyl-3,6-dication forms a three-dimensional aromatic system. 相似文献