全文获取类型
收费全文 | 536228篇 |
免费 | 4583篇 |
国内免费 | 1194篇 |
专业分类
化学 | 256474篇 |
晶体学 | 8263篇 |
力学 | 28884篇 |
综合类 | 10篇 |
数学 | 73664篇 |
物理学 | 174710篇 |
出版年
2021年 | 5074篇 |
2020年 | 5401篇 |
2019年 | 6313篇 |
2018年 | 9008篇 |
2017年 | 9292篇 |
2016年 | 12322篇 |
2015年 | 6446篇 |
2014年 | 11446篇 |
2013年 | 24046篇 |
2012年 | 19109篇 |
2011年 | 22612篇 |
2010年 | 17578篇 |
2009年 | 17858篇 |
2008年 | 21014篇 |
2007年 | 20766篇 |
2006年 | 18949篇 |
2005年 | 16486篇 |
2004年 | 15608篇 |
2003年 | 14082篇 |
2002年 | 14204篇 |
2001年 | 15636篇 |
2000年 | 11926篇 |
1999年 | 9145篇 |
1998年 | 8039篇 |
1997年 | 7722篇 |
1996年 | 7162篇 |
1995年 | 6322篇 |
1994年 | 6296篇 |
1993年 | 6178篇 |
1992年 | 6518篇 |
1991年 | 7049篇 |
1990年 | 6761篇 |
1989年 | 6696篇 |
1988年 | 6321篇 |
1987年 | 6501篇 |
1986年 | 6073篇 |
1985年 | 7391篇 |
1984年 | 7671篇 |
1983年 | 6468篇 |
1982年 | 6637篇 |
1981年 | 6212篇 |
1980年 | 6001篇 |
1979年 | 6624篇 |
1978年 | 6661篇 |
1977年 | 6806篇 |
1976年 | 6818篇 |
1975年 | 6383篇 |
1974年 | 6199篇 |
1973年 | 6383篇 |
1972年 | 4988篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
James V. Crivello Umut Bulut 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5217-5231
Curcumin, a naturally occurring, intensely yellow dye extracted from the spice turmeric, is an efficient photosensitizer for diaryliodonium salt photoinitiators at wavelengths ranging from 340 to 535 nm. With curcumin as a photosensitizer, it is possible to carry out the cationic photopolymerization of a wide variety of epoxide, oxetane, and vinyl monomers with long‐wavelength UV and visible light. An example of the photopolymerization of an epoxide monomer with ambient solar irradiation is provided. Several other curcumin analogues were synthesized, and their use as photosensitizers is examined. With such photosensitizers, the range of spectral sensitivity can be extended well into the visible region of the electromagnetic spectrum. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5217–5231, 2005 相似文献
992.
993.
994.
We introduce a random perturbed version of the classical fidelity and we show that it converges with the same rate of decay
of correlations, but not uniformly in the noise. This makes the classical fidelity unstable in the zero-noise limit. 相似文献
995.
Neutral Community Theory: How Stochasticity and Dispersal-Limitation Can Explain Species Coexistence
Neutral community theory explains biodiversity, i.e. the coexistence of several species, as the result of a stochastic balance
between immigration and extinction on a local level, and between speciation and extinction on a regional level. The most popular
model, presented by Hubbell in 2001, has seen many analytical developments in recent years, which can be used in model analysis,
model testing and model comparison. We review these developments here, and present alternative derivations and shine previously
unnoticed lights on them. 相似文献
996.
In this paper we describe the design and manufacture of an axial-torsion test specimen, and provide relationships needed when
conducting stress-strain characterization experiments with the specimen. The specimen is a short hollow cylinder of rubber
bonded between two steel mounting rings, in which simultaneous axial and shear strains are produced via independently controlled
axial and twist displacements. We present calculations for the strain-displacement and stress-load relationships, and strain
energy density. These relationships have been established and validated via a combination of analytical and experimental techniques,
and finite element analysis. We have investigated the extent and effects of strain and stress field non-uniformity in the
test specimen. The specimen design is sufficiently simple that a closed-form expression for the strain-displacement relationship
has been successfully developed. 相似文献
997.
The hyperfine constants for muonium in elemental and binary inorganic solids suggest formation of three different families
of defect centre, with distinct electronic structures. The overall range of values, spanning nearly five orders of magnitude,
and their correlation with host properties such as band gap and electron affinity, reveal a deep-to-shallow instability which
has profound implications for the electrical properties of hydrogen impurity in electronic materials, both semiconducting
and dielectric. 相似文献
998.
V. V. Lozhkarev S. G. Garanin R. R. Gerke V. N. Ginzburg E. V. Katin A. V. Kirsanov G. A. Luchinin A. N. Mal’shakov M. A. Mart’yanov O. V. Palashov A. K. Poteomkin N. N. Rukavishnikov A. M. Sergeev S. A. Sukharev G. I. Freidman E. A. Khazanov A. V. Charukhchev A. A. Shaikin I. V. Yakovlev 《JETP Letters》2005,82(4):178-180
In experiments on the parametrical amplification of femtosecond pulses in wide-aperture DKDP crystals, a power of more than 100 TW has been reached, which is much higher than the record level achieved in such lasers. The energy efficiency obtained for the parametric amplifier is equal to 27%. The energy of a 72-fs pulse is equal to 10 J. 相似文献
999.
The change in the intensity of light scattering in a colloidal solution of magnetite particles in kerosene under the simultaneous action of coaxial and mutually perpendicular electric and magnetic fields has been studied. It has been found that, at certain strengths of mutually perpendicular fields, the change in the scattering intensity is maximal. The effect observed has been interpreted on the basis of the Rayleigh-Debye-Gans anisotropic approximation within the model of orientation of aggregates of magnetite particles under the joint action of the fields. 相似文献
1000.
Maxim V. Pavlov 《Communications in Mathematical Physics》2007,272(2):469-505
The algebro-geometric approach for integrability of semi-Hamiltonian hydrodynamic type systems is presented. The class of
symmetric hydrodynamic type systems is defined and the calculation of the associated Riemann surfaces is greatly simplified for this
class. Many interesting and physically motivated examples are investigated. 相似文献