全文获取类型
收费全文 | 267752篇 |
免费 | 2395篇 |
国内免费 | 627篇 |
专业分类
化学 | 142039篇 |
晶体学 | 4034篇 |
力学 | 11950篇 |
综合类 | 9篇 |
数学 | 29723篇 |
物理学 | 83019篇 |
出版年
2019年 | 2301篇 |
2018年 | 3121篇 |
2017年 | 3120篇 |
2016年 | 4494篇 |
2015年 | 2670篇 |
2014年 | 4292篇 |
2013年 | 10712篇 |
2012年 | 8096篇 |
2011年 | 9928篇 |
2010年 | 7107篇 |
2009年 | 6902篇 |
2008年 | 9349篇 |
2007年 | 9541篇 |
2006年 | 8914篇 |
2005年 | 8096篇 |
2004年 | 7436篇 |
2003年 | 6751篇 |
2002年 | 6678篇 |
2001年 | 7335篇 |
2000年 | 5674篇 |
1999年 | 4363篇 |
1998年 | 3864篇 |
1997年 | 3849篇 |
1996年 | 3591篇 |
1995年 | 3341篇 |
1994年 | 3503篇 |
1993年 | 3199篇 |
1992年 | 3675篇 |
1991年 | 3673篇 |
1990年 | 3616篇 |
1989年 | 3465篇 |
1988年 | 3576篇 |
1987年 | 3469篇 |
1986年 | 3297篇 |
1985年 | 4371篇 |
1984年 | 4643篇 |
1983年 | 3888篇 |
1982年 | 4020篇 |
1981年 | 3945篇 |
1980年 | 3917篇 |
1979年 | 3887篇 |
1978年 | 4200篇 |
1977年 | 4123篇 |
1976年 | 4185篇 |
1975年 | 3808篇 |
1974年 | 3872篇 |
1973年 | 4011篇 |
1972年 | 2826篇 |
1971年 | 2354篇 |
1970年 | 2171篇 |
排序方式: 共有10000条查询结果,搜索用时 983 毫秒
951.
952.
Steven G. From 《Annals of the Institute of Statistical Mathematics》1991,43(1):167-179
In this paper, a family of estimators for estimating means when mixing two independent Poisson samples is proposed. This family is based on the probability-generating function of the Poisson distribution and is offered as an alternative to the maximum likelihood estimators, which have some drawbacks. These estimators include the method of moments estimators as a special limiting case. 相似文献
953.
954.
E. L. Belokoneva A. G. Ivanova S. Yu. Stefanovich O. V. Dimitrova V. S. Kurazhkovskaya 《Crystallography Reports》2004,49(4):603-613
Crystals of new rare earth borates of the composition Ln[B6O9 (OH)3] (Ln = Sm-Lu), sp. gr. R3c are synthesized under hydrothermal conditions. Their crystal structures are determined on single crystals with Ln = Ho, Gd without preliminary determination of their chemical formulas. The polar anionic framework of the crystals consists
of BO3 triangles and BO4 tetrahedra and has wide channels along the threefold axis of the structure, which are similar to the channels along the a, b, and c axes in cubic Li4[B7O12]Cl boracite with Li conductivity. Rare earth atoms are arranged in the structure over the cubic F pseudolattice, whereas
the analogous positions in Li boracites are filled with Cl anions. The squared optical nonlinearity of the new crystals is
comparable with the nonlinearity of quartz, whereas the electrical conductivity in borates at 300°C exceeds 10−6 S/cm.
__________
Translated from Kristallografiya, Vol. 49, No. 4, 2004, pp. 681–691.
Original Russian Text Copyright ? 2004 by Belokoneva, Ivanova, Stefanovich, Dimitrova, Kurazhkovskaya. 相似文献
955.
956.
K. J. Ellis R. J. Shypailo H. -P. Sheng W. G. Pond 《Journal of Radioanalytical and Nuclear Chemistry》1992,157(1):159-168
Characteristic gamma-rays are emitted promptly by elements during exposure to neutrons. These emissions enable a radioanalytical analysis of the body's composition of protein (nitrogen), water (hydrogen), and fat (carbon). We have used this method in vivo to determine the body composition of obese and lean pigs (10 to 20 kg body wt) fed an altered cholesterol diet. 相似文献
957.
958.
G A van't Klooster F M Woutersen-van Nijnanten H J Kolker J Noordhoek A S van Miert 《Journal of chromatography. A》1992,579(1):158-164
Ethylmorphine N-demethylation is used as a marker pathway in studies of rat cytochrome P450 3A and 2C11 biotransformations. At present, microsomal activities are generally measured by a colorimetric determination of the formed formaldehyde. In the present study, a high-performance liquid chromatographic method of separating and quantifying both the N-demethylated (norethylmorphine) and the O-de-ethylated (morphine) metabolites is described. Either samples are extracted with ethyl acetate or proteins are precipitated with zinc sulphate-barium hydroxide. Separation is achieved on a CN reversed-phase column, using a mobile phase of phosphate buffer (pH 4.5)-acetonitrile (90:10, v/v). At a flow-rate of 1.5 ml/min, the analysis time is 30 min. The limit of detection (ultraviolet, 210 nm) for ethylmorphine and its metabolites is 0.5 micrograms/ml. 相似文献
959.
L. P. Smol'skaya S. P. Panova S. G. Kuznetsova V. P. Il'kin L. S. Danyushkin 《Journal of Applied Spectroscopy》1992,56(2):170-173
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 2, pp. 259–263, February, 1992. 相似文献
960.
Paul Van Der Meeren Jan Vanderdeelen Leon Baert 《Particle & Particle Systems Characterization》1994,11(4):320-326
Using a monodisperse PMMA dispersion, it was shown that light reflection at the sample cuvette walls may greatly influence the results of both static (SLS) and dynamic (DLS) light scattering experiments. Considering SLS, this reflection phenomenon mostly causes an overestimation of the scattered intensity at high scattering angles, which may give rise to the emergence of an additional, artificial peak in the lower region of the particle size distribution. On the other hand, the influcence of reflection on DLS measurements was shown to be particularly important in the upper region of the particle size distribution. The experimentally observed phenomena were explained from the basic principles of both particle sizing methods. Finally, it was shown that the disturbing effect of reflection could be avoided by modifying either the hardware or the software of the static and dynamic light scattering technique. 相似文献