全文获取类型
收费全文 | 581293篇 |
免费 | 6328篇 |
国内免费 | 1633篇 |
专业分类
化学 | 314149篇 |
晶体学 | 9032篇 |
力学 | 25047篇 |
综合类 | 22篇 |
数学 | 66303篇 |
物理学 | 174701篇 |
出版年
2021年 | 4747篇 |
2020年 | 5385篇 |
2019年 | 5857篇 |
2018年 | 7348篇 |
2017年 | 7338篇 |
2016年 | 11260篇 |
2015年 | 7057篇 |
2014年 | 11036篇 |
2013年 | 26916篇 |
2012年 | 20203篇 |
2011年 | 24879篇 |
2010年 | 17505篇 |
2009年 | 17296篇 |
2008年 | 22607篇 |
2007年 | 22382篇 |
2006年 | 20834篇 |
2005年 | 18683篇 |
2004年 | 17258篇 |
2003年 | 15367篇 |
2002年 | 15083篇 |
2001年 | 17232篇 |
2000年 | 13079篇 |
1999年 | 10290篇 |
1998年 | 8447篇 |
1997年 | 8231篇 |
1996年 | 7928篇 |
1995年 | 7183篇 |
1994年 | 7051篇 |
1993年 | 6708篇 |
1992年 | 7774篇 |
1991年 | 7812篇 |
1990年 | 7472篇 |
1989年 | 7322篇 |
1988年 | 7426篇 |
1987年 | 7278篇 |
1986年 | 6874篇 |
1985年 | 8984篇 |
1984年 | 9116篇 |
1983年 | 7290篇 |
1982年 | 7444篇 |
1981年 | 7451篇 |
1980年 | 6872篇 |
1979年 | 7515篇 |
1978年 | 7687篇 |
1977年 | 7661篇 |
1976年 | 7455篇 |
1975年 | 6853篇 |
1974年 | 6800篇 |
1973年 | 6773篇 |
1972年 | 4775篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Plasma B-6 vitamer and plasma and urinary 4-pyridoxic acid concentrations of 21 young white women, 21-27 years, having radiomonitored pyridoxal 5'-phosphate and coenzyme stimulation of erythrocyte alanine aminotransferase activities indicative of adequate vitamin B-6 status were determined in an effort to establish normal ranges for plasma B-6 vitamers. B-6 vitamers and 4-pyridoxic acid were quantitated using reversed phase high performance liquid chromatography with fluorometric and ultraviolet detection. Pyridoxal phosphate values obtained by radioenzymatic and chromatographic, fluorometric and ultraviolet, assays were highly correlated as were pyridoxine phosphate values determined using both detectors. The B-6 vitamer and 4-pyridoxic acid values of these subjects should be of use in the establishment of normal ranges of these congeners in women. 相似文献
962.
963.
We show by general considerations that it is not possible to test violation of the existing versions of Bell’s inequality
in entangled neutral kaons system using experimentally accessible thin regenerators. We point out the loophole in the recent
argument (A Bramon and M Nowakowski, Phys. Rev. Lett.
83, 1 (1999)) that claimed such a test to be possible. 相似文献
964.
It is an important challenge to analyze a three-dimensional thermal flow field in engineering, science, and agriculture. For such an analysis, it is essential to measure physical quantities such as temperature and velocity over the entire thermal flow field. This paper presents a measurement system based on color image processing for temperature and velocity vector distributions in a three-dimensional thermal flow field. Flow visualization is accomplished by the use of thermo-sensitive liquid crystal tracers. An algorithm for the color-to-temperature transformation using a multi-layer feed-forward neural network is applied to three-dimensional natural convection in a rotating cylindrical cell. Two-dimensional temperature distributions in a slit plane are obtained by using the algorithm. A three-dimensional temperature distribution is consequently constructed by interpolating the two-dimensional distributions using the B-spline function. In addition, the Spatio-Temporal correlation method is applied to the natural convection to obtain a three-dimensional velocity vector distribution. 相似文献
965.
966.
A new microscopic model of anomalous muonium for the elemental semiconductors is proposed. The relevant configuration consisting
of both a diamagrentic molecule Si−Mu and an unpaired orbital e− is contained into a semivacancy of the real lattice. By using the unrestricted Hartree-Fock computational method the principal
properties of the system are established. A dynamical version of the model together with a question on the formation of such
system are discussed. 相似文献
967.
968.
969.
Images of the surface ordering of 4-n-octyl-4'-cyanobiphenyl, a room temperature smectic liquid crystal deposited upon graphite, have been obtained by scanning tunnelling microscopy. The microscope was operated in air using the constant-current mode. Under certain tunnelling conditions it has been possible to resolve both the aliphatic and aromatic parts of the molecule, and to observe individual benzene rings. Two previously unreported conformations have been observed: an overlapping bilayer structure with spacing 3.7 nm, and a monolayer structure with spacing 2.4 nm. The latter structure may represent the first visual evidence for a surface polar ordered structure. 相似文献
970.