全文获取类型
收费全文 | 269039篇 |
免费 | 2202篇 |
国内免费 | 695篇 |
专业分类
化学 | 137443篇 |
晶体学 | 4375篇 |
力学 | 12244篇 |
综合类 | 5篇 |
数学 | 29761篇 |
物理学 | 88108篇 |
出版年
2021年 | 2343篇 |
2020年 | 2539篇 |
2019年 | 2862篇 |
2018年 | 3953篇 |
2017年 | 3916篇 |
2016年 | 5513篇 |
2015年 | 3150篇 |
2014年 | 5016篇 |
2013年 | 11802篇 |
2012年 | 9598篇 |
2011年 | 11414篇 |
2010年 | 8193篇 |
2009年 | 8061篇 |
2008年 | 10360篇 |
2007年 | 10438篇 |
2006年 | 9963篇 |
2005年 | 8843篇 |
2004年 | 8267篇 |
2003年 | 7363篇 |
2002年 | 7262篇 |
2001年 | 8267篇 |
2000年 | 6290篇 |
1999年 | 4828篇 |
1998年 | 3994篇 |
1997年 | 3926篇 |
1996年 | 3569篇 |
1995年 | 3342篇 |
1994年 | 3180篇 |
1993年 | 3052篇 |
1992年 | 3442篇 |
1991年 | 3474篇 |
1990年 | 3365篇 |
1989年 | 3170篇 |
1988年 | 3162篇 |
1987年 | 3105篇 |
1986年 | 2909篇 |
1985年 | 3722篇 |
1984年 | 4032篇 |
1983年 | 3325篇 |
1982年 | 3525篇 |
1981年 | 3402篇 |
1980年 | 3252篇 |
1979年 | 3386篇 |
1978年 | 3591篇 |
1977年 | 3610篇 |
1976年 | 3566篇 |
1975年 | 3334篇 |
1974年 | 3318篇 |
1973年 | 3412篇 |
1972年 | 2268篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
21.
Jun-tao Chang Joerg Evers Marian O. Scully M. Suhail Zubairy 《量子光学学报》2006,12(B08):77-77
We propose a scheme to obtain the distance of two identical atoms placed inside the standing wave field by monitoring the collective resonance fluorescence spectrum emitted by the two particles. We find three different parameter ranges, depending on the distance of the atoms as compared to the transition wavelength. For large interparticle distances, dipole-dipole coupling is negligible, and the main system evolution arises from the interaction with the standing wave field. In the small-distance limit, the dynamics is dominated by the dipole-dipole interaction. Finally, in the intermediate region, a rich interplay of the various couplings arises, which however is lifted for strong driving laser fields. The present measurement procedure allows us to distinguish the three cases. In each of the cases, we show how to determine the distance of the two particles and their respective positions relative to the nodes of the standing wave field with fractional-wavelength precision. 相似文献
22.
General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
D.T. Son 《Annals of Physics》2006,321(1):197-224
We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants. 相似文献
23.
The spatial structure of Bragg angles and the transfer functions of an acousto-optic cell are calculated for the cases of isotropic and anisotropic light diffraction in a uniaxial crystal. Their change with ultrasound frequency is traced. The possibility of image processing by acousto-optic filtration of the spatial spectrum of an image is considered. The results of experimental visualization of the transfer functions of a calcium molybdate crystal cell are presented. 相似文献
24.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems. 相似文献
25.
26.
27.
Sanzharov N. A. Yarovoi A. T. Bekhtereva E. S. Ulenikov O. N. 《Russian Physics Journal》2002,45(10):1024-1031
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C
3v
symmetry on the rotational quantum numbers. 相似文献
28.
A. D. Smirnov 《Journal of Applied Spectroscopy》1991,54(1):33-38
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 46–50, January, 1991. 相似文献
29.
In intonation research, prominence-lending pitch movements have either been described on a linear or on a logarithmic frequency scale. An experiment has been carried out to check whether pitch movements in speech intonation are perceived on one of these two scales or on a psychoacoustic scale representing the frequency selectivity of the auditory system. This last scale is intermediary between the other two scales. Subjects matched the excursion size of prominence-lending pitch movements in utterances resynthesized in different pitch registers. Their task was to adjust the excursion size in a comparison stimulus in such a way that it lent equal prominence to the corresponding syllable in a fixed test stimulus. The comparison stimulus and the test stimulus had pitches running parallel on either the logarithmic frequency scale, the psychoacoustic scale, or the linear frequency scale. In one-half of the experimental sessions, the test stimulus was presented in the low register, while the comparison stimulus was presented in the high register, and, conversely, for the other half of the sessions. The result is that, in all cases, stimuli are matched in such a way that the average excursion sizes in different registers are equal on the psychoacoustic scale. 相似文献
30.
We analyze diffusion from a periodic array of hemispherical droplets through a membrane. We find that the multiple sources do not interact strongly, even when the droplets are closely spaced, so that the flux through the membrane appears nearly additive. 相似文献