全文获取类型
收费全文 | 104401篇 |
免费 | 6671篇 |
国内免费 | 6161篇 |
专业分类
化学 | 60817篇 |
晶体学 | 1367篇 |
力学 | 5894篇 |
综合类 | 567篇 |
数学 | 12645篇 |
物理学 | 35943篇 |
出版年
2023年 | 779篇 |
2022年 | 1377篇 |
2021年 | 2084篇 |
2020年 | 2517篇 |
2019年 | 2730篇 |
2018年 | 3044篇 |
2017年 | 3014篇 |
2016年 | 3757篇 |
2015年 | 2696篇 |
2014年 | 3833篇 |
2013年 | 5437篇 |
2012年 | 5574篇 |
2011年 | 5921篇 |
2010年 | 4790篇 |
2009年 | 4728篇 |
2008年 | 5083篇 |
2007年 | 4717篇 |
2006年 | 4321篇 |
2005年 | 3846篇 |
2004年 | 3408篇 |
2003年 | 3010篇 |
2002年 | 3085篇 |
2001年 | 2800篇 |
2000年 | 2190篇 |
1999年 | 1753篇 |
1998年 | 1647篇 |
1997年 | 1400篇 |
1996年 | 1316篇 |
1995年 | 1131篇 |
1994年 | 1210篇 |
1993年 | 1153篇 |
1992年 | 1108篇 |
1991年 | 1164篇 |
1990年 | 1140篇 |
1989年 | 1054篇 |
1988年 | 926篇 |
1987年 | 921篇 |
1986年 | 886篇 |
1985年 | 923篇 |
1984年 | 916篇 |
1983年 | 819篇 |
1982年 | 804篇 |
1979年 | 808篇 |
1978年 | 810篇 |
1977年 | 807篇 |
1976年 | 918篇 |
1975年 | 813篇 |
1974年 | 844篇 |
1973年 | 844篇 |
1972年 | 751篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
951.
A modified criterion of the SM perturbative consistency is proposed. It is based on the analytic properties of the two-loop SM running couplings. Under the criterion adopted, the Higgs mass up to 380 GeV might not give rise to strong coupling prior to the Planck scale. This means that the light Higgs boson is possibly preferred for reasons other than the SM perturbative consistency, i.e., for reasons beyond the SM. 相似文献
952.
A. A. Kuznetsova V. I. Mikhailenko A. Yu. Popovskii 《Journal of Applied Spectroscopy》2004,71(5):648-653
Two types of absorption centers, one being related to monomers and the other to dimers, have been revealed by the method of statistical analysis of the normalized absorption spectra of a superthin interlayer of nitrobenzene of variable thickness formed on activated surfaces of quartz and barium fluoride and measured for different thicknesses of the interlayer. On a decrease in the interlayer thickness the concentration of dimers increases. 相似文献
953.
Elena Yu. FursovaVictor I. Ovcharenko Galina V. RomanenkoEugene V. Tretyakov 《Tetrahedron letters》2003,44(34):6397-6399
Reduction of nitronyl nitroxides using hexamethylenetetramine is a very convenient method for preparing the corresponding imino nitroxides and 2-imidazoline N-oxides. 相似文献
954.
A novel algorithm, alternatively minimizing coupled vector (COV) resolution error and PARAFAC error algorithm, is proposed in this paper. This algorithm can overcome the problem of slow convergence and is insensitive to the estimation of component number, such problems are unavoidable while using the traditional parallel factors analysis (PARAFAC) algorithm. In other words, this algorithm is capable of improving the computing speed and providing accurate resolutions provided that the number of factors used in the computation is no less than that of the actual underlying ones. The characteristic performances were demonstrated with a novel fluorescence data array. 相似文献
955.
R. F. Mamin S. A. Migachev M. F. Sadykov I. V. Lunev V. V. Izotov Yu. A. Gusev 《JETP Letters》2003,78(11):718-721
The action of illumination on the conducting and dielectric properties of lead magnoniobate was investigated. The photostimulated currents were examined and the spectral dependence of photoconductivity in the region of diffuse phase transition was obtained. It was found that the illumination affects the dielectric properties and that its action is memorized at temperatures below room temperature. The role of defect states in the formation of relaxor properties is discussed on the basis of the obtained data. 相似文献
956.
957.
We develop a general method for the construction of a probability structure on the space F of random sets in ℝ. For this purpose, by using the introduced notion of c-system, we prove a theorem on the unique extension of a finite measure from a c-system to the minimal c-algebra. The obtained structure of measurability enables one to determine probability distributions of the c-algebra of random events sufficient, e.g., for the so-called fractal dimensionality of random realizations to be considered as a measurable functional on F.__________Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 56, No. 11, pp. 1467–1483, November, 2004. 相似文献
958.
Combining color imaging with phase shifting, a technique named five-step color phase shifting is presented to determine the whole-field isoclinic parameter. Relevant theory is derived and explicit conditions for directly determining the isoclinic parameter in the range of [0,π/2] are given. The unloaded light intensity of the model is systematically studied. A color camera recorded five isoclinic images coupled with isochromatics from a plane polariscope with five different settings, respectively. Experiments have been carried out with a circular disk under diametral compression and errors have been analyzed and estimated. This technique utilizes white light, which avoids undefined isoclinics near the locations where the isochromatics exist and will have active effect on experimental stress analysis and structural strength design. 相似文献
959.
Bobik V. V. Bobonich F. M. Belokopytov Yu. V. 《Theoretical and Experimental Chemistry》2003,39(6):364-368
We have used potentiometric titration with tetrabutylammonium hydroxide to determine the acid center content on the outer surface of dealuminated natural and synthetic mordenites. We have established a symbatic relationship between the 2,2-dimethylbutane content in the hydroisomerization products of n-hexane on dealuminated palladium-containing mordenites and the number of their external acid centers. We have studied the possibility of partial deactivation of such centers during ion-exchange deposition of palladium on the catalysts, using a tetraammine palladium solution. 相似文献
960.
S. Yu. Ketkov H. L. Selzle E. W. Schlag S. N. Titova L. V. Kalakutskaya 《Optics and Spectroscopy》2004,97(4):567-571
Two-color photoionization of nickelocene molecules cooled in a supersonic jet is performed using a tunable nanosecond pulsed laser. The first stage of the multiphoton excitation is the transition from the highest occupied molecular orbital of nickelocene to the lowest Rydberg level. Conditions are found under which molecular ions (η 5-C5H5)2Ni+ are the only product of the multiphoton ionization in the one-color experiment. Irradiation of an excited molecule by an intense pulse of another laser increases significantly the yield of molecular ions. The dependence of the yield of (η5-C5H5)2Ni+ ions on the frequency of the second laser makes it possible to determine the adiabatic ionization potential of nickelocene as 6.138±0.012eV. 相似文献