全文获取类型
收费全文 | 376700篇 |
免费 | 4406篇 |
国内免费 | 1251篇 |
专业分类
化学 | 203927篇 |
晶体学 | 6076篇 |
力学 | 15221篇 |
综合类 | 12篇 |
数学 | 43388篇 |
物理学 | 113733篇 |
出版年
2019年 | 2950篇 |
2018年 | 3608篇 |
2017年 | 3626篇 |
2016年 | 6135篇 |
2015年 | 4190篇 |
2014年 | 6092篇 |
2013年 | 16401篇 |
2012年 | 11970篇 |
2011年 | 14400篇 |
2010年 | 10033篇 |
2009年 | 9812篇 |
2008年 | 13265篇 |
2007年 | 13213篇 |
2006年 | 12586篇 |
2005年 | 11421篇 |
2004年 | 10491篇 |
2003年 | 9314篇 |
2002年 | 8986篇 |
2001年 | 10671篇 |
2000年 | 8147篇 |
1999年 | 6414篇 |
1998年 | 5170篇 |
1997年 | 5109篇 |
1996年 | 5006篇 |
1995年 | 4658篇 |
1994年 | 4611篇 |
1993年 | 4441篇 |
1992年 | 5154篇 |
1991年 | 4834篇 |
1990年 | 4768篇 |
1989年 | 4734篇 |
1988年 | 4650篇 |
1987年 | 4694篇 |
1986年 | 4355篇 |
1985年 | 5933篇 |
1984年 | 5970篇 |
1983年 | 5057篇 |
1982年 | 5332篇 |
1981年 | 5104篇 |
1980年 | 5034篇 |
1979年 | 5295篇 |
1978年 | 5532篇 |
1977年 | 5375篇 |
1976年 | 5246篇 |
1975年 | 5026篇 |
1974年 | 4979篇 |
1973年 | 5134篇 |
1972年 | 3361篇 |
1968年 | 3177篇 |
1967年 | 3355篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found. 相似文献
92.
93.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of simpler linear differentialoperators and a nonlinear term. 相似文献
94.
95.
Rare earths exhibit complex magnetic phase diagrams resulting from the competition between various contributions to the magnetic
energy: exchange, anisotropy and magnetostriction. The epitaxy of a rare-earth film on a substrate induces (i) a clamping
to the substrate and (ii) pseudomorphic strains. Both these effects are shown to lead to modifications of the magnetic properties
in (0 0 1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular variations of the Curie temperature have been
evidenced. Additionally, Tb films exhibit a new large wavelength magnetic modulation. In Eu films, one of the helical magnetic
domains disappears at low temperature whereas the propagation vectors of the other helices are tilted. The link between structural
and magnetic properties is underlined via magnetoelastic models. Moreover, molecular beam epitaxy permits the growth of Sm
in a metastable dhcp phase. The magnetic structure of dhcp Sm has been elucidated for the first time. In this review, neutron
scattering is shown to be a powerful technique to reveal the magnetic structures of rare-earth films. 相似文献
96.
The electro-optic response of ferroelectric smectic C* liquid crystals has been studied. Anomalous switching behaviour of such materials which possess a negative dielectric anisotropy has been reported. These materials show a minimum in response time at a sufficiently high field. We present results showing the dependency of this minimum upon spontaneous polarisation and the effect of AC bias. Calculations based upon the equation of motion of the director around the cone are presented which describe this effect and its dependence on the relative magnitudes of the spontaneous polarization and dielectric anisotropy of the material. Good agreement with the experimental results is found. 相似文献
97.
H. Katsurada 《Journal of Number Theory》2004,104(1):100-117
We introduce a formula for the p-adic Siegel-Eisenstein series which demonstrates a connection with the genus theta series and the twisted Eisenstein series with level p. We then prove a generalization of Serre's formula in the elliptic modular case. 相似文献
98.
The sub-millisecond protonation dynamics of the chromophore in S65T mutant form of the green fluorescent protein (GFP) was
tracked after a rapid pH jump following laser-induced proton release from the caged photolabile compoundo-nitrobenzaldehyde. Following a jump in pH from 8 to 5 (which is achieved within 2 μs), the fluorescence of S65T GFP decreased
as a single exponential with a time constant of ∼90 μs. This decay is interpreted as the conversion of the deprotonated fluorescent
GFP chromophore to a protonated non-fluorescent species. The protonation kinetics showed dependence on the bulk viscosity
of the solvent, and therefore implicates bulk solvent-controlled protein dynamics in the protonation process. The protonation
is proposed to be a sequential process involving two steps: (a) proton transfer from solvent to the chromophore, and (b) internal
structural rearrangements to stabilize a protonated chromophore. The possible implications of these observations to protein
dynamics in general is discussed 相似文献
99.
H. Okumura T. Takahagi N. Nagai S. Shingubara 《Journal of Polymer Science.Polymer Physics》2003,41(17):2071-2078
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003 相似文献
100.