全文获取类型
收费全文 | 32536篇 |
免费 | 3293篇 |
国内免费 | 2810篇 |
专业分类
化学 | 13890篇 |
晶体学 | 58篇 |
力学 | 2327篇 |
综合类 | 548篇 |
数学 | 13891篇 |
物理学 | 7925篇 |
出版年
2024年 | 45篇 |
2023年 | 363篇 |
2022年 | 565篇 |
2021年 | 683篇 |
2020年 | 916篇 |
2019年 | 896篇 |
2018年 | 886篇 |
2017年 | 1125篇 |
2016年 | 1286篇 |
2015年 | 1125篇 |
2014年 | 1619篇 |
2013年 | 2116篇 |
2012年 | 1943篇 |
2011年 | 2107篇 |
2010年 | 1790篇 |
2009年 | 2134篇 |
2008年 | 2054篇 |
2007年 | 2175篇 |
2006年 | 1926篇 |
2005年 | 1826篇 |
2004年 | 1563篇 |
2003年 | 1381篇 |
2002年 | 1125篇 |
2001年 | 963篇 |
2000年 | 864篇 |
1999年 | 743篇 |
1998年 | 663篇 |
1997年 | 596篇 |
1996年 | 473篇 |
1995年 | 414篇 |
1994年 | 347篇 |
1993年 | 253篇 |
1992年 | 218篇 |
1991年 | 186篇 |
1990年 | 181篇 |
1989年 | 132篇 |
1988年 | 116篇 |
1987年 | 100篇 |
1986年 | 87篇 |
1985年 | 100篇 |
1984年 | 85篇 |
1983年 | 60篇 |
1982年 | 81篇 |
1981年 | 72篇 |
1980年 | 43篇 |
1979年 | 39篇 |
1978年 | 33篇 |
1977年 | 26篇 |
1976年 | 31篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In [5] Phillips proved that one can obtain the additive group of any nonstandard model *? of the ring ? of integers by using a linear mod 1 function h : F ?, where F is the α-dimensional vector space over ? when α is the cardinality of *?. In this connection it arises the question whether there are linear mod 1 functions which are neither addition nor quasi-linear. We prove that this is the case. 相似文献
102.
SINGULARBOUNDARYPROPERTIESOFHARMONICFUNCTIONSANDFRACTALANALYSISWENZHIYINGZHANGYIPINGManuscriptreceivedJanuary11,1995.Revi... 相似文献
103.
B. Sadashive Gowda G.S.V.L. Narasimham M.V. Krishna Murthy 《International Journal of Heat and Fluid Flow》1997,18(6):613-624
In this paper, a mathematical model for forced-air precooling of spherical food products in bulk is developed. The foods are arranged in horizontal layers stacked one above the other to form a rectangular parallelepiped with a vertical gap in between the product layers. The foods are cooled by chilled air blown along the height of the package. The governing equations for the conduction heat transfer in the foods, simultaneous heat and mass transfer at the food-air interface and in the air stream are solved numerically using finite-difference methods. A comprehensive numerical study is performed by varying the process parameters over a wide range. Typical results showing the variation of moist air properties along the height of the package and the effect of each parameter on the process time are presented. The ranges of parameters for advantageous operation of the precooling system are identified. Correlations are obtained for the process time based on the product center and mass-averaged temperatures in terms of process parameters. 相似文献
104.
105.
n进制中非零数字之积函数的均值公式 总被引:8,自引:0,他引:8
设 N =a1nk1+ a2 nk2 +… + asnks( 1 aik2 >… >ks 0 ) ,a( N,n) =a1a2 … as,本文给出了均值 Ar( N ,n) =∑m相似文献
106.
G. Carelli N. Ioli A. Messina A. Moretti S. Schepis F. Strumia 《International Journal of Infrared and Millimeter Waves》1998,19(9):1191-1199
We measured the dependence of the reflectivity of InSb crystals upon temperature in the submillimeter region using monochromatic radiation from an optically pumped far infrared (FIR) laser. The measures allowed us to determine the value of the electron effective mass at low temperatures with radiations of different frequencies. Our measurements extend the results obtained recently on pure crystals with magneto-optical methods to the low temperatures region where only old measures were available. 相似文献
107.
108.
本文提出了一类特殊的n人合作对策模型─—弱1—凸对策,研究了弱1—凸对策的解的性质,并证明弱1—凸对策的解满足所有常见的公理化特征. 相似文献
109.
Ralf Jäger Anatolij I. Saprykin J. Sabine Becker Hans -Joachim Dietze José A. C. Broekaert 《Mikrochimica acta》1997,125(1-4):41-44
The analytical capabilities of a high-resolution mass spectrometer in combination with a 13.56 MHz glow discharge ion source for the analysis of semiconducting materials (silicon carbide and gallium arsenide) were studied. It was shown that single positively charged ions of sample material have about 10 eV higher average energy than the ions of the discharge and residual gas. Therefore effective energy separation of the ions of analyte from the ions of the discharge and residual gas was achieved by adjusting the ion transfer optics (breadth and position of energy slit), which improves the analytical capabilities of the developed method.Some analytical applications are presented to illustrate the performance of r.f. GDMS for the bulk analysis of semiconducting materials. The results of the trace element analysis of gallium arsenide and silicon carbide samples are compared with data of independent methods (LIMS, ICP-AES, SIMS).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayOn leave from the Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia 相似文献
110.
H. R. Ebrahimi-Vishki M. A. Pourabdollah 《Proceedings of the American Mathematical Society》1997,125(7):2171-2174
The purpose of this paper is to introduce an algebra of functions on a semitopological semigroup and to study these functions from the point of view of universal semigroup compactification. We show that the corresponding semigroup compactification of this algebra is universal with respect to the property of being a nilpotent group.