全文获取类型
收费全文 | 5046篇 |
免费 | 184篇 |
国内免费 | 40篇 |
专业分类
化学 | 3586篇 |
晶体学 | 44篇 |
力学 | 228篇 |
数学 | 758篇 |
物理学 | 654篇 |
出版年
2022年 | 40篇 |
2021年 | 53篇 |
2020年 | 83篇 |
2019年 | 88篇 |
2018年 | 62篇 |
2017年 | 54篇 |
2016年 | 118篇 |
2015年 | 111篇 |
2014年 | 102篇 |
2013年 | 218篇 |
2012年 | 326篇 |
2011年 | 398篇 |
2010年 | 160篇 |
2009年 | 166篇 |
2008年 | 330篇 |
2007年 | 299篇 |
2006年 | 341篇 |
2005年 | 307篇 |
2004年 | 253篇 |
2003年 | 244篇 |
2002年 | 209篇 |
2001年 | 69篇 |
2000年 | 54篇 |
1999年 | 39篇 |
1998年 | 48篇 |
1997年 | 61篇 |
1996年 | 86篇 |
1995年 | 45篇 |
1994年 | 52篇 |
1993年 | 36篇 |
1992年 | 44篇 |
1991年 | 27篇 |
1990年 | 37篇 |
1989年 | 27篇 |
1988年 | 35篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 59篇 |
1984年 | 53篇 |
1983年 | 27篇 |
1982年 | 50篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 42篇 |
1978年 | 26篇 |
1977年 | 28篇 |
1976年 | 29篇 |
1975年 | 28篇 |
1974年 | 27篇 |
1973年 | 33篇 |
排序方式: 共有5270条查询结果,搜索用时 15 毫秒
91.
Eric Bach Richard Lukes Jeffrey Shallit H. C. Williams. 《Mathematics of Computation》1996,65(216):1737-1747
Let be a positive integer. We say looks like a power of 2 modulo a prime if there exists an integer such that . First, we provide a simple proof of the fact that a positive integer which looks like a power of modulo all but finitely many primes is in fact a power of . Next, we define an -pseudopower of the base to be a positive integer that is not a power of , but looks like a power of modulo all primes . Let denote the least such . We give an unconditional upper bound on , a conditional result (on ERH) that gives a lower bound, and a heuristic argument suggesting that is about for a certain constant . We compare our heuristic model with numerical data obtained by a sieve. Some results for bases other than are also given.
92.
93.
94.
95.
96.
Jeffrey Bub 《Foundations of Physics Letters》1993,6(1):21-35
Elby (1993) has raised certain problems that appear to be devastating for modal interpretations of quantum mechanics, but do not arise for Bohm's pilot wave theory. Here I show that the features Elby identifies as objectionable in my version of the modal interpretation have their counterpart in Bohm's theory. To the extent that Bohm's theory works as a no collapse solution to the measurement problem - and I think it does - so does my modal interpretation. 相似文献
97.
98.
The time-resolved ESR signal of a triplet radical pair was detected upon excitation of a solid mixture of acridine and acridan at room temperature. The ZFS parameters of the triplet radical pair were determined to be D=−0.0100 cm−1 and E=0.00053 cm−1. The structure of the radical pair is discussed on the basis of the data. 相似文献
99.
The tracer diffusion coefficient of unentangled poly(ethylene oxide) (PEO, M=1000 gmol) in a matrix of poly(methyl methacrylate) (PMMA, M=10 000 gmol) has been measured over a temperature range from 125 to 220 degrees C with forced Rayleigh scattering. The dynamic viscosities of blends of two different high molecular weight PEO tracers (M=440 000 and 900 000 gmol) in the same PMMA matrix were also measured at temperatures ranging from 160 to 220 degrees C; failure of time-temperature superposition was observed for these systems. The monomeric friction factors for the PEO tracers were extracted from the diffusion coefficients and the rheological relaxation times using the Rouse model. The friction factors determined by diffusion and rheology were in good agreement, even though the molecular weights of the tracers differed by about three orders of magnitude. The PEO monomeric friction factors were compared with literature data for PEO segmental relaxation times measured directly with NMR. The monomeric friction factors of the PEO tracer in the PMMA matrix were found to be from two to six orders of magnitude greater than anticipated based on direct measurements of segmental dynamics. Additionally, the PEO tracer terminal dynamics are a much stronger function of temperature than the corresponding PEO segmental dynamics. These results indicate that the fastest PEO Rouse mode, inferred from diffusion and rheology, is completely separated from the bond reorientation of PEO detected by NMR. This result is unlike other blend systems in which global and local motions have been compared. 相似文献
100.
A convenient, multigram-scale synthesis of arylene ethynylene macrocycles near room temperature is described. Driven by the precipitation of a diarylacetylene byproduct, alkyne metathesis produces the desired macrocycles in one step from monomers in high yields. 相似文献