全文获取类型
收费全文 | 2781篇 |
免费 | 147篇 |
国内免费 | 10篇 |
专业分类
化学 | 2319篇 |
晶体学 | 12篇 |
力学 | 26篇 |
数学 | 306篇 |
物理学 | 275篇 |
出版年
2023年 | 21篇 |
2022年 | 36篇 |
2021年 | 34篇 |
2020年 | 51篇 |
2019年 | 41篇 |
2018年 | 28篇 |
2017年 | 25篇 |
2016年 | 101篇 |
2015年 | 103篇 |
2014年 | 91篇 |
2013年 | 143篇 |
2012年 | 212篇 |
2011年 | 236篇 |
2010年 | 140篇 |
2009年 | 85篇 |
2008年 | 186篇 |
2007年 | 171篇 |
2006年 | 157篇 |
2005年 | 168篇 |
2004年 | 162篇 |
2003年 | 127篇 |
2002年 | 114篇 |
2001年 | 68篇 |
2000年 | 37篇 |
1999年 | 34篇 |
1998年 | 27篇 |
1997年 | 32篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 13篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1969年 | 5篇 |
排序方式: 共有2938条查询结果,搜索用时 15 毫秒
951.
952.
Christine Bessenrodt 《Annals of Combinatorics》2002,6(2):119-124
Recently Stembridge obtained the classification of multiplicity-free products of Schur functions, and thus of multiplicity-free outer products of irreducible characters of the symmetric groups. In this paper, the multiplicity-free products of Schur P-functions are classified, and then this is applied to the case of projective outer products of spin characters of the double covers of the symmetric groups. 相似文献
953.
Christine K. F. Hermann Yesh P. Sachdeva James F. Wolfe 《Journal of heterocyclic chemistry》1987,24(4):1061-1065
Reaction of halogenated pyridines, quinolines, pyrimidines, and pyrazines with potassiophenylacetonitrile ( 5 ) in liquid ammonia under near-uv irradiation affords secondary nitriles, which then undergo oxidative decyanation under phase-transfer catalytic conditions to afford aryl hetaryl ketones in excellent yields. 相似文献
954.
Christine Bessenrodt 《Archiv der Mathematik》2002,79(6):401-403
We prove a character degree property of the alternating groups, recently conjectured by Huppert. 相似文献
955.
956.
Judith M. Wingate Bari Hoffman Ruddy Donna S. Lundy Jeffrey Lehman Roy Casiano Savita P. Collins Gayle E. Woodson Christine Sapienza 《Journal of voice》2005,19(1):124-131
Adductor spasmodic dysphonia (ADSD) adversely affects a speaker's ability to effectively communicate. For many individuals suffering with ADSD, botulinum toxin (Botox) is the chosen treatment to remediate the symptoms. Although Botox's effects on symptom remediation have been examined before, patient perception of improvement post-Botox has been examined less frequently. Further, no studies have addressed the symptomatic changes in older adults that occur after Botox treatment. The Voice Handicap Index (VHI) was used as the instrument to assess older patient's (>65 years) perception of how ADSD impacts certain areas of their life pre- and post-Botox injection. The outcome of the VHI was related to a clinical judgment of voice severity. Participants also completed the Social Readjustment Rating Scale (SRRS) to examine overall stress level, and the outcome of the SRRS was correlated to postinjection VHI scores. Results indicated no significant correlation between VHI scores and voice severity or SRRS ratings. The current study suggests further study of voice outcomes with older adults with ADSD is needed. 相似文献
957.
958.
How the various organic and inorganic arsenic species affect the nitrogen metabolism of a model plant, Tropaeolum majus, was studied in order to evaluate the toxicological impact of the various chemical forms of arsenic. For this purpose, the effects on the (a) entire nitrogen pool, (b) protein fraction, and (c) non‐protein fraction were distinguished. The arsenic‐dependent effects on the nitrogen cycle were assessed by using 15N‐labelled KNO3 as a nutritive substance and optical emission spectroscopy to analyse how 15N is incorporated into the nitrogen cycle. In addition to the 15N‐tracer experiments, the uptake and metabolization of the arsenic compounds were examined. The work shows that biochemical indicator systems like 15N‐tracer studies are able to characterize the degree of the influence of metabolic processes by arsenic species. For example, the incorporated 15N concentration decreased linearly and independently of the 15N fraction with increasing dimethylarsinate (DMA) concentrations. This behaviour indicates that DMA has prevented the uptake of 15N and hence the formation of amino acids and proteins. Arsenite‐treated plants exhibited an elevated concentration of non‐protein 15N, which could be an indication either for a stimulated uptake of nitrate or for an interrupted amino acid/protein synthesis. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
959.
The reductive decision procedure for unavoidable strings was recently shown to have an exponential lower bound. Hence, as a special case of generalized pattern matching, the existence of an efficient algorithm deciding string unavoidability remains an interesting open question. It has been hypothesized that some combination of the four necessary conditions implied by the known decidability results would be sufficient. Three of these criteria are determined in polynomial time, and the fourth provides the needed recursion. In this paper, however, we demonstrate the existence of arbitrarily many avoidable strings meeting any extended conjunction of the four necessary conditions. These insufficiency results are achieved by analyzing the appropriate graphical interpretations of the given algorithms. We provide a new combinatorial operation on the corresponding strings and generate arbitrary counterexamples from an empirically located minimal set. Thus, string unavoidability cannot be efficiently decided by the known reductive method or its immediate implications. 相似文献
960.
We investigate the sensitivity of hydrostatic pressure of flows through porous media with respect to the position of the soil layers. Indeed, these induce discontinuities of the porosity which is a piecewise constant coefficient κ of the partial differential equation satisfied by the pressure u and it leads to the computation of the derivative of u with respect to changes in position of discontinuity surfaces of κ. The analysis relies on a mixed formulation of the problem. Preliminary numerical simulations are given to illustrate the theory. An application to a simple inverse problem is also given. To cite this article: C. Bernardi, O. Pironneau, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 661–666. 相似文献