全文获取类型
收费全文 | 132835篇 |
免费 | 2858篇 |
国内免费 | 1116篇 |
专业分类
化学 | 74012篇 |
晶体学 | 2113篇 |
力学 | 5439篇 |
综合类 | 41篇 |
数学 | 13081篇 |
物理学 | 42123篇 |
出版年
2020年 | 1001篇 |
2016年 | 1673篇 |
2015年 | 1380篇 |
2014年 | 1767篇 |
2013年 | 5343篇 |
2012年 | 4132篇 |
2011年 | 5113篇 |
2010年 | 3242篇 |
2009年 | 2986篇 |
2008年 | 4456篇 |
2007年 | 4380篇 |
2006年 | 4469篇 |
2005年 | 4281篇 |
2004年 | 3705篇 |
2003年 | 3356篇 |
2002年 | 3217篇 |
2001年 | 3697篇 |
2000年 | 2809篇 |
1999年 | 2367篇 |
1998年 | 2029篇 |
1997年 | 1989篇 |
1996年 | 1930篇 |
1995年 | 1884篇 |
1994年 | 1640篇 |
1993年 | 1611篇 |
1992年 | 1829篇 |
1991年 | 1820篇 |
1990年 | 1719篇 |
1989年 | 1715篇 |
1988年 | 1721篇 |
1987年 | 1708篇 |
1986年 | 1615篇 |
1985年 | 2154篇 |
1984年 | 2281篇 |
1983年 | 1907篇 |
1982年 | 2220篇 |
1981年 | 2037篇 |
1980年 | 2081篇 |
1979年 | 2058篇 |
1978年 | 2190篇 |
1977年 | 2095篇 |
1976年 | 2123篇 |
1975年 | 2060篇 |
1974年 | 1900篇 |
1973年 | 2107篇 |
1972年 | 1286篇 |
1971年 | 978篇 |
1969年 | 925篇 |
1968年 | 1054篇 |
1967年 | 1101篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
41.
42.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
43.
44.
45.
46.
47.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
48.
The γcmc values of CTAB-SDS decrease from 63.67 mN/m at 10‡C to 36.38 mN/m at 90‡C, slightly lower than those of either CTAB or SDS.
Correspondingly, the CMC of CTAB-SDS decreases almost by half. The increase of surface activity of CTAB-SDS can be attributed
to the relatively weak electrostatic interaction at high temperature, which is supported by the increase of solubility of
CTAB-SDS with rise in temperature. Catalytic effect on oxidation of toluene derivatives with potassium permanganate follows
the order CTAB-SDS > SDS > CTAB. This is not caused by the dissociative effect of CTAB-SDS with low surface activity at low
temperature, as seen from the fact that almost all oxidative products can be retrieved for different toluene derivatives and
surfactants by mimicking the conditions of reaction. In the emulsifications of toluene derivatives at 90‡C, the time that
turbid water layers of surfactant solutions take to become clear is the same as that of the catalytic effect on oxidation
of toluene derivatives. Thus, it can be inferred that surfactants can improve the oxidation yields of toluene derivatives
by increasing the contact between two reacting phases. 相似文献
49.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献
50.
P. Seelig A. Dax S. Faber M. Gerlach G. Huber T. Kühl D. Marx P. Merz W. Quint F. Schmitt H. Winter M. Würtz 《Hyperfine Interactions》1998,114(1-4):135-139
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric
and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique
using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics
from an ion beam at relativistic velocities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献