全文获取类型
收费全文 | 1900篇 |
免费 | 15篇 |
国内免费 | 11篇 |
专业分类
化学 | 1098篇 |
晶体学 | 15篇 |
力学 | 65篇 |
数学 | 442篇 |
物理学 | 306篇 |
出版年
2020年 | 16篇 |
2019年 | 16篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 101篇 |
2012年 | 43篇 |
2011年 | 56篇 |
2010年 | 43篇 |
2009年 | 54篇 |
2008年 | 60篇 |
2007年 | 57篇 |
2006年 | 83篇 |
2005年 | 71篇 |
2004年 | 55篇 |
2003年 | 63篇 |
2002年 | 47篇 |
2001年 | 43篇 |
2000年 | 48篇 |
1999年 | 30篇 |
1998年 | 45篇 |
1997年 | 37篇 |
1996年 | 45篇 |
1995年 | 26篇 |
1994年 | 35篇 |
1993年 | 26篇 |
1992年 | 29篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 38篇 |
1984年 | 35篇 |
1983年 | 33篇 |
1982年 | 30篇 |
1981年 | 17篇 |
1980年 | 44篇 |
1979年 | 19篇 |
1978年 | 34篇 |
1977年 | 41篇 |
1976年 | 27篇 |
1975年 | 20篇 |
1974年 | 39篇 |
1973年 | 34篇 |
1972年 | 21篇 |
1971年 | 21篇 |
1969年 | 29篇 |
1968年 | 15篇 |
排序方式: 共有1926条查询结果,搜索用时 678 毫秒
1.
Ahmed Waqar Chowdhury Z. Z. Kazi S. N. Johan MR. Akram Naveed Oon C. S. Abdelrazek Ali H. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1517-1534
Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers... 相似文献
2.
3.
4.
In cricket, a rain-affected pitch can make batting more difficult than normal. Several other conditions such as poor light or an initially lively pitch, may also result in difficulties for the batsmen. In this note, we refer to all of them as ‘sticky wickets’. On sticky wickets, lower order batsmen are often sent into ‘hold the fort’ until conditions improve. In this paper, a stochastic dynamic programming model is used to examine the appropriateness of this policy. The model suggests that the tactic is often optimal when the sticky wicket persists until the end of the day's play, but not often when the sticky wicket is transitory. In some circumstances, it is worthwhile, on a normal wicket near the end of the day, to send in a lower order batsman to hold the fort (a night watchman): when the wicket is sticky, this tactic is even more worthwhile. 相似文献
5.
The critical group of a graph is an abelian group that arisesin several contexts, and there are some similarities with thegroups that are used in cryptography. We construct a familyof graphs with critical groups that are cyclic, and discussthe associated computational problems using algorithms basedon the theory of chip-firing. 相似文献
6.
7.
In this article, the question is considered whether there exist finite translation planes with arbitrarily small kernels admitting nonsolvable collineation groups. For any integerN, it is shown that there exist translation planes of dimension >N and orderq
3 admittingGL(2,q) as a collineation group. 相似文献
8.
A theoretical equation has been developed to described the rate of slow crack growth in an ethylene-hexene copolymer in terms of the basic morphological parameters. These parameters are spacing of the butyl branches, number of tie molecules, and the thickness of the lamellar crystal. Experimentally, the thickness of the lamellae and the long period were determined as functions of the branch density. The calculation of the number of tie molecules is based on the values of the molecular weight and the long period. The model of slow crack growth is based on the rate of disentanglement of the tie molecules. The rate of disentanglement varies inversely with the number of tie molecules and directly with the number of tie molecules that are not pinned by the branches. 相似文献
9.
In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate. 相似文献
10.
It is well known that S 12 cannot prove the injective weak pigeonhole principle for polynomial time functions unless RSA is insecure. In this note we investigate the provability of the surjective (dual) weak pigeonhole principle in S 12 for provably weaker function classes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献