全文获取类型
收费全文 | 2066篇 |
免费 | 79篇 |
国内免费 | 42篇 |
专业分类
化学 | 1257篇 |
晶体学 | 13篇 |
力学 | 38篇 |
综合类 | 3篇 |
数学 | 222篇 |
物理学 | 654篇 |
出版年
2022年 | 14篇 |
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 13篇 |
2018年 | 24篇 |
2016年 | 32篇 |
2015年 | 34篇 |
2014年 | 43篇 |
2013年 | 82篇 |
2012年 | 95篇 |
2011年 | 136篇 |
2010年 | 54篇 |
2009年 | 55篇 |
2008年 | 109篇 |
2007年 | 106篇 |
2006年 | 111篇 |
2005年 | 120篇 |
2004年 | 107篇 |
2003年 | 94篇 |
2002年 | 89篇 |
2001年 | 65篇 |
2000年 | 58篇 |
1999年 | 24篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 33篇 |
1995年 | 18篇 |
1994年 | 36篇 |
1993年 | 39篇 |
1992年 | 42篇 |
1991年 | 39篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1973年 | 23篇 |
1967年 | 10篇 |
排序方式: 共有2187条查询结果,搜索用时 46 毫秒
131.
Hendrik F. Hameka Silvio L. Emery George R. Famini James O. Jensen Joseph M. Leonard Dennis J. Reutter 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):373-388
Abstract We report the computed equilibrium geometries and vibrational infrared frequencies of a group of thirteen mercaptans and sulfides. The computations were based on the Gaussian 86 Program Package utilizing 3-21G basis sets. The theoretical bond distances and bond angles are in agreement with the available experimental data. The agreement between computed frequencies and available experimental values seems reasonable. We also used the computations as guidelines for the assignment of available experimental infrared frequencies. We believe that it is possible to make reliable frequency predictions by combining computations with available experimental data for groups of similar molecules. However, it is necessary to introduce different correction factors for different types of vibrational modes if we use 3-21G basis sets. 相似文献
132.
发展和设计高效、廉价和稳定的光催化剂用于抗生素污染物降解仍然存在巨大的挑战。 本文通过一种便捷的水热方法制备了Bi4V2O11/石墨烯复合材料并用于可见光下抗生素污染物光催化降解。 通过自由基追踪实验,确认了光催化降解过程中活性物质为h+和·OH基团。 根据实验结果,提出了相应的反应机理。 石墨烯的引入可以有效地促进光生电子-空穴对的分离,从而增强光催化活性。 该复合催化剂展现出良好的活性和稳定性。 该方法以石墨烯为载体制备了光催化降解材料,为高性能光催化剂的制备提供了参考。 相似文献
133.
134.
K E Jensen T Grube C Thomsen P G S?rensen P Christoffersen H Karle O Henriksen 《Magnetic resonance imaging》1988,6(3):291-292
In vitro as well as in vivo studies have shown prolonged T1 relaxation times in patients with acute leukemia. The mechanism behind this finding is not known. In order to evaluate if this was specific for leukemia we examined eight patients with polycythemia vera, representing a condition with a rather benign bone marrow neoplasia. In this group of patients we found prolonged T1 relaxation times but normal T2 relaxation times. This may indicate that the prolonged T1 relaxation time seen in leukemic bone marrow is not due to the malignant cell per se. 相似文献
135.
To solve the problem of passive ranging of a moving sound source,a method of estimating the initial distance of target is presented by using the measured inform... 相似文献
136.
Herbarumin Ⅲ的立体选择性全合成 总被引:1,自引:1,他引:0
以正丁醛和1,5-戊二醇为起始原料, 以不对称烯丙基化、改良的Julia成烯反应和Yamaguchi内酯化为关键步骤, 通过13步反应, 立体选择性地合成了具有植物毒性的天然十元内酯化合物Herbarumin Ⅲ(3)及其差向异构体22. 相似文献
137.
Frontispiece: Enantioselective Organocatalytic Cascade Approach to Different Classes of Benzofused Acetals
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
138.
139.
C. R.H. Bahl J. Garde K. Lefmann T. B.S. Jensen P.-A. Lindgård D. E. Madsen S. Mørup 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):53-57
In magnetic nanoparticles the uniform precession
(q = 0 spin wave) mode gives the predominant contribution
to the magnetic excitations. We have calculated the energy of the
uniform mode in antiferromagnetic nanoparticles with uncompensated
magnetic moments, using the coherent potential approximation. In
the presence of uncompensated moments, an antiferromagnetic
nanoparticle must be considered as a kind of a ferrimagnet. Two
magnetic anisotropy terms are considered, a planar term confining
the spins to the basal plane, and an axial term determining an
easy axis in this plane. Excitation energies are calculated for
various combinations of these two anisotropy terms, ranging from
the simple uniaxial case to the planar case with a strong
out-of-plane anisotropy. In the simple uniaxial case, the
uncompensated moment has a large influence on the excitation
energy, but in the planar case it is much less important. The
calculations explain recent neutron scattering measurements on
nanoparticles of antiferromagnetic α-Fe2O3 and NiO. 相似文献
140.
Robert Jensen Maciej Kocan Andrzej Swiech 《Proceedings of the American Mathematical Society》2002,130(2):533-542
We introduce the notion of a ``good" solution of a fully nonlinear uniformly elliptic equation. It is proven that ``good" solutions are equivalent to -viscosity solutions of such equations. The main contribution of the paper is an explicit construction of elliptic equations with strong solutions that approximate any given fully nonlinear uniformly elliptic equation and its -viscosity solution. The results also extend some results about ``good" solutions of linear equations.