全文获取类型
收费全文 | 1864篇 |
免费 | 31篇 |
国内免费 | 9篇 |
专业分类
化学 | 996篇 |
晶体学 | 18篇 |
力学 | 62篇 |
数学 | 204篇 |
物理学 | 624篇 |
出版年
2020年 | 13篇 |
2019年 | 11篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 15篇 |
2013年 | 68篇 |
2012年 | 81篇 |
2011年 | 87篇 |
2010年 | 38篇 |
2009年 | 39篇 |
2008年 | 79篇 |
2007年 | 83篇 |
2006年 | 78篇 |
2005年 | 83篇 |
2004年 | 68篇 |
2003年 | 41篇 |
2002年 | 69篇 |
2001年 | 46篇 |
2000年 | 35篇 |
1999年 | 19篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 26篇 |
1995年 | 29篇 |
1994年 | 44篇 |
1993年 | 48篇 |
1992年 | 41篇 |
1991年 | 38篇 |
1990年 | 26篇 |
1989年 | 35篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 29篇 |
1980年 | 25篇 |
1979年 | 29篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1972年 | 22篇 |
1971年 | 12篇 |
1968年 | 11篇 |
1967年 | 10篇 |
排序方式: 共有1904条查询结果,搜索用时 46 毫秒
131.
132.
An understanding of the phenomena associated with cavitation is important in many areas of science and engineering. This paper is concerned with the influence of viscoelasticity on the dynamics of cavitation bubbles near rigid boundaries. Viscoelastic effects are modelled using a Maxwell constitutive equation, and a generalized Bernoulli equation is derived. The governing equations are solved using the boundary element method in which both the bubble surface and the potential are represented by cubic splines. The numerical scheme is validated through comparisons with results in the literature for the inviscid case. The introduction of viscoelasticity introduces some interesting bubble dynamics including the occurrence of oscillations during collapse. Most importantly, it is shown that viscoelasticity can serve to suppress the formation of a liquid jet. The subsequent reduced pressures compared with the inviscid case suggest that viscoelasticity has a mitigating effect on cavitation damage. 相似文献
133.
134.
The structure and bonding of the chlorine atom/carbon disulfide (CS(2)/Cl) complex involved in selective photochlorination reactions with alkanes was directly probed using transient resonance Raman spectroscopy. The experimental Raman vibrational frequencies were compared to those computed from density functional theory calculations for probable structures of the CS(2)/Cl complex. Our results indicate that the S [double bond] C [double bond] S...Cl complex species is responsible for the approximately 370 nm transient absorption band observed after ultraviolet photolysis of CCl(4) in the presence of CS(2). We discuss the structure and properties of the S [double bond] C [double bond] S...Cl complex and compare them with those for the related benzene/Cl and pyridine/Cl complexes. 相似文献
135.
136.
In the quantum rotor model with random exchange interactions having a nonzero mean, three phases, a (i) phase (Bose) glass, (ii) superfluid, and (iii) Mott insulator, meet at a bicritical point. We demonstrate that proximity to the bicritical point and the coupling between the energy landscape and the dissipative degrees of freedom of the phase glass lead to a metallic state at T = 0. Consequently, the phase glass is unique in that it represents a concrete example of a metallic state that is mediated by disorder, even in 2D. We propose that the experimentally observed metallic phase which intervenes between the insulator and the superconductor in a wide range of thin films is in actuality a phase glass. 相似文献
137.
McKenzie C Hecker Denschlag J Häffner H Browaeys A de Araujo LE Fatemi FK Jones KM Simsarian JE Cho D Simoni A Tiesinga E Julienne PS Helmerson K Lett PD Rolston SL Phillips WD 《Physical review letters》2002,88(12):120403
We form ultracold Na2 molecules by single-photon photoassociation of a Bose-Einstein condensate, measuring the photoassociation rate, linewidth, and light shift of the J = 1, v = 135 vibrational level of the A1 Sigma (+)(u) molecular state. The photoassociation rate constant increases linearly with intensity, even where it is predicted that many-body effects might limit the rate. Our observations are in good agreement with a two-body theory having no free parameters. 相似文献
138.
Che CM Mao Z Miskowski VM Tse MC Chan CK Cheung KK Phillips DL Leung KH 《Angewandte Chemie (International ed. in English)》2000,39(22):4084-4088
139.
On the effects of doping calamitic and discotic nematics with materials of the opposite aspect ratio
In this paper the inter-mixing of calamitic and discotic materials is discussed. The systems are found to be immiscible near the middle of the phase diagram, as was predicted theoretically. However, a degree of miscibility is seen at each end of the phase diagram, allowing some interesting effects to be explored. A negative permittivity anisotropy is induced in a discotic material by dissolution of a polar calamitic dopant. The relaxation behaviour of the dopant in the material is studied and found to be similar to that in the pure calamitic, as far as can be determined in this experiment. The elastic constants of a calamitic mixture are enhanced by addition of a discotic dopant. This is believed to be due to the packing of the discotic molecules in such a way as to hinder director distortions, and may be useful for changing the values of calamitic elastic constants. 相似文献
140.
The reaction 40Ca(13C, 12C)41Ca leading to the ground and low-lying ? levels has been studied at bombarding energies of 18.5 and 19.0 MeV, close to the Coulomb barrier. The cross sections have been analysed using the DWBA with previously measured calibrations to obtain the rms radii of 1f and 2p orbits in the 41Ca levels. The rms radius of the 1f point neutron orbit in the ground state relative to the 40Ca core was determined to be 3.89 ± 0.12 fm. This is compared with various theoretical predictions based on Hartree-Fock theory. The 1f orbit radius gives the point neutron excess size to a good approximation for comparison with the value of 3.45 fm deduced from Coulomb energy differences. The consistency of the results with 40Ca(t, d)41Ca experiments using a (t/d), zero-range normalization of 3.26 × 104 MeV2 · fm3 is demonstrated, and trends in neutron size parameters through the Ca isotopes are discussed. 相似文献