全文获取类型
收费全文 | 205095篇 |
免费 | 1983篇 |
国内免费 | 600篇 |
专业分类
化学 | 103146篇 |
晶体学 | 3357篇 |
力学 | 9325篇 |
综合类 | 5篇 |
数学 | 22574篇 |
物理学 | 69271篇 |
出版年
2021年 | 1663篇 |
2020年 | 1807篇 |
2019年 | 2010篇 |
2018年 | 2708篇 |
2017年 | 2603篇 |
2016年 | 3784篇 |
2015年 | 2324篇 |
2014年 | 3634篇 |
2013年 | 9137篇 |
2012年 | 7288篇 |
2011年 | 8789篇 |
2010年 | 6070篇 |
2009年 | 5949篇 |
2008年 | 7960篇 |
2007年 | 8147篇 |
2006年 | 7775篇 |
2005年 | 6963篇 |
2004年 | 6485篇 |
2003年 | 5707篇 |
2002年 | 5559篇 |
2001年 | 6469篇 |
2000年 | 4964篇 |
1999年 | 3814篇 |
1998年 | 3050篇 |
1997年 | 3056篇 |
1996年 | 2814篇 |
1995年 | 2625篇 |
1994年 | 2476篇 |
1993年 | 2359篇 |
1992年 | 2708篇 |
1991年 | 2692篇 |
1990年 | 2615篇 |
1989年 | 2410篇 |
1988年 | 2455篇 |
1987年 | 2461篇 |
1986年 | 2286篇 |
1985年 | 2981篇 |
1984年 | 3236篇 |
1983年 | 2646篇 |
1982年 | 2815篇 |
1981年 | 2786篇 |
1980年 | 2648篇 |
1979年 | 2740篇 |
1978年 | 2831篇 |
1977年 | 2839篇 |
1976年 | 2900篇 |
1975年 | 2681篇 |
1974年 | 2659篇 |
1973年 | 2786篇 |
1972年 | 1765篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
J. S. Vrentas D. C. Venerus C. M. Vrentas 《Journal of Polymer Science.Polymer Physics》1991,29(5):537-545
An integral constitutive equation which includes strain-coupling effects is proposed. The constitutive equation is more general than the K-BKZ equation, and it is shown that this equation can explain various important aspects of double-step stress-relaxation data. 相似文献
992.
Summary The RHF and geometry optimization sections of the ab initio quantum chemistry code, GAMESS, have been optimized for a network of parallel microprocessors, Inmos T800-20 transputers, using both indirect and direct SCF techniques. The results indicate great scope for implementation of such codes on small parallel computer systems, very high efficiencies having been achieved, particularly in the cases of direct SCF and geometry optimization with large basis sets.The work, although performed upon one particular parallel system, the Meiko Computing Surface, is applicable to a wide range of parallel systems with both shared and distributed memory. 相似文献
993.
F. I. Vybornov E. E. Mityakova A. V. Rakhlin N. D. Krupenya 《Radiophysics and Quantum Electronics》1997,40(12):980-986
We present the results of analysis of the data of vertical ionospheric sounding at the Zimenki test site (Nizhny Novgorod).
The January and July ionograms are used to plot the dependences of the number of “sickle” type disturbances on the time of
the day for the period from 1996 to 1992. A comparison with the scattering in an ionospheric F-layer for the same period is
performed. A trend in the time series of the phenomenon observed is recorded.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 40, No. 12, pp. 1455–1462, December, 1997. 相似文献
994.
Muonium in liquid SiCl has been observed for the first time at low temperature (−65°C) The observed polarization of muonium
is as much as 25% of the total spin polarization and shows a fast relaxation rate. 相似文献
995.
Studies of breakdown threshold intensity for air at various pressures in the range of 24–760 torr using 0.355, 0.532 and 1.06
μm radiation are reported. We observep
−0.8 scaling ofI
th at 1.06 μm and a weak scaling ofp
−0.4 at 0.532 and 0.355 μm radiation. Strong dependence of breakdown spot size on laser power but weak dependence on air pressure
is observed. 相似文献
996.
In this paper a statistical multiplexer that processes a mixture of real-time and non-real-time traffic is studied under bursts of traffic. Different scheduling algorithms are compared under conditions when one of the classes of traffic has a sudden increase in its arrival rate during a short period of time. The results show a difference in the way the scheduling disciplines studied behave under short overloads of traffic even though the scheduling algorithms had been set up to give similar performance under steady-state arrivals. The lifetime of real-time packets is shown to have a great effect on the way in which the performance of the scheduling algorithms compare.Robert Lackman is an IBM employee in the IBM Resident Study Program. 相似文献
997.
M A Alliegro K D Dyer E J Cragoe B M Glaser M C Alliegro 《Journal of chromatography. A》1992,582(1-2):217-223
An assay for amiloride was devised for efficient use with the wide variety of analogues available. Amiloride was extracted from 1-ml plasma samples by elution from a C8 preparative column with 6% acetonitrile-45% methanol-5.4% acetic acid, adjusted to pH 4.0 with trimethylamine. Samples were lyophilized, resuspended in 50% methanol, filtered through 0.22-microns Spin-X cartridges, applied to a reversed-phase C18 column, and eluted in a 0-50% acetonitrile gradient in 0.4% acetic acid, pH 4.5 (1.2 ml/min). Detection by ultraviolet absorbance at 360 nm was linear from 1 to 1000 ng. Versatility of the method was demonstrated with the analogues benzamil, 6-hydro-, 6-iodo-, 5-hexamethylene-, and 5-chlorobenzyl-2',4'-dimethylbenzyl-amiloride. 相似文献
998.
999.
W. D. Hutchison A. V. J. Edge N. Yazidjoglou D. H. Chaplin 《Hyperfine Interactions》1992,75(1-4):291-298
The high resolution hyperfine spectroscopy, modulated adiabatic passage of oriented nuclei (MAPON), has been applied for the
first time to high purity, elemental systems. Detailed comparisons between the electric quadrupole hyperfine interactions
(EQI’s) and, in particular, their distributions, are obtained for60CoCo where the hosts are a single crystal of hcp cobalt and a polycrystalline cobalt foil of predominantly fcc character. For
hcp Co, with the electronic magnetization, M, parallel to the c-axis, the mode value P/h=3e2qQ/4I(2I−1)h=−48.5(5) kHz. This fractional distribution implies the sharpest electric field gradient (efg) measured in a metal
to date, using MAPON spectroscopy, in excess of two times sharper than that of the most dilute impurity efg in a crystallographically
cubic ferromagnetic host. The mode efg is Vzz=−27.3(32)×1019 Vm−2. For the polycrystalline, predominantly fcc foil, prepared by quenching, the EQI mode value is P/h=−6.2(4) kHz with a FWHM
of 12.0(7) kHz yielding a mode efg of Vzz=−3.5(5)×1019 Vm−2. 相似文献
1000.
The use of a direct liquid introduction type liquid chromatographic-mass spectrometric interface to study highly thermally labile rifamycin antibiotics is described. Using negative ionization, abundant molecular ions were observed, and the spectra, also contained structurally significant fragments. Variation of the high-performance liquid chromatographic parameters did not change the spectra, thus making it easy to change chromatographic conditions. In quantitative studies, a surprising correlation was found, indicating that the mass spectrometric signal was proportional to the square of the sample concentration. 相似文献