全文获取类型
收费全文 | 359354篇 |
免费 | 3800篇 |
国内免费 | 1361篇 |
专业分类
化学 | 173086篇 |
晶体学 | 5129篇 |
力学 | 18205篇 |
综合类 | 5篇 |
数学 | 65107篇 |
物理学 | 102983篇 |
出版年
2021年 | 2411篇 |
2020年 | 2657篇 |
2019年 | 2977篇 |
2018年 | 13497篇 |
2017年 | 13226篇 |
2016年 | 11469篇 |
2015年 | 4749篇 |
2014年 | 5952篇 |
2013年 | 13759篇 |
2012年 | 14294篇 |
2011年 | 22673篇 |
2010年 | 14158篇 |
2009年 | 14296篇 |
2008年 | 17857篇 |
2007年 | 19806篇 |
2006年 | 11071篇 |
2005年 | 11026篇 |
2004年 | 10238篇 |
2003年 | 9565篇 |
2002年 | 8378篇 |
2001年 | 8281篇 |
2000年 | 6533篇 |
1999年 | 5072篇 |
1998年 | 4306篇 |
1997年 | 4125篇 |
1996年 | 4161篇 |
1995年 | 3644篇 |
1994年 | 3557篇 |
1993年 | 3656篇 |
1992年 | 3699篇 |
1991年 | 3762篇 |
1990年 | 3527篇 |
1989年 | 3371篇 |
1988年 | 3407篇 |
1987年 | 3298篇 |
1986年 | 3140篇 |
1985年 | 4224篇 |
1984年 | 4446篇 |
1983年 | 3525篇 |
1982年 | 3772篇 |
1981年 | 3644篇 |
1980年 | 3534篇 |
1979年 | 3628篇 |
1978年 | 3711篇 |
1977年 | 3605篇 |
1976年 | 3718篇 |
1975年 | 3367篇 |
1974年 | 3363篇 |
1973年 | 3430篇 |
1972年 | 2396篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
A. J. Maroulis P. D. Akrivos C. P. Hadjiantoniou-Maroulis 《Journal of heterocyclic chemistry》1993,30(4):913-916
Oxidation of the title compounds yields, besides the reported isoimides 3 and/or the amides 4 , also the imides 5 . The observed product dichotomy is considered as the result of an intramolecular nucleophilic attack on the aroyl group, of the pressumed zwitterionic intermediate 2 , by O or N present in the ambident N-aroylimine site of 2 . The results of AM1 calculations agree with the product studies and both permit the formulation of a set of rules correlating structure and selectivity. 相似文献
32.
33.
Eduard Feireisl Antonín Novotný Hana Petzeltov 《Mathematical Methods in the Applied Sciences》2002,25(12):1045-1073
We prove a general compactness result for the solution set of the compressible Navier–Stokes equations with respect to the variation of the underlying spatial domain. Among various corollaries, we then prove a general existence theorem for the system in question with no restrictions on smoothness of the spatial domain. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
34.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
35.
36.
37.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems. 相似文献
38.
39.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis 相似文献
40.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献