全文获取类型
收费全文 | 349篇 |
免费 | 7篇 |
国内免费 | 4篇 |
专业分类
化学 | 198篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 43篇 |
物理学 | 113篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2019年 | 5篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 16篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 10篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 30篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1986年 | 4篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1962年 | 7篇 |
1938年 | 2篇 |
1934年 | 2篇 |
1928年 | 2篇 |
1896年 | 2篇 |
1869年 | 2篇 |
排序方式: 共有360条查询结果,搜索用时 15 毫秒
1.
Tony Forbes. 《Mathematics of Computation》2002,71(237):449-452
We describe a successful search for a sequence of fifteen consecutive integers, each the product of exactly four prime factors. Fifteen is best possible.
2.
Emily S. Tepe Ellen S. Deutsch MD Quiana Sampson Stephen Lawless James S. Reilly Robert Thayer Sataloff 《Journal of voice》2002,16(2):244-250
The objective of this study was to determine the incidence of vocal problems in young choir singers and to correlate vocal problems with demographic and behavioral information. A questionnaire addressing vocal habits and hygiene was offered to 571 young choir singers, up to 25 years of age, who sing at least weekly; 129 (22.6%) responded. More than one-half of the respondents had experienced vocal difficulty, particularly older adolescents. Detrimental behaviors and circumstances surveyed were not reflective of the incidence of vocal difficulty, except for morning hoarseness, chronic fatigue, insomnia, and female gender after puberty. Voice care professionals should be aware that self-reported voice difficulties are common among young choral singers, especially postpubescent girls, and children with symptoms consistent with reflux (morning hoarseness) and emotional stress (insomnia). Laryngologists should communicate with choral conductors and singing teachers to enhance early identification and treatment of children with voice complaints, and to develop choral educational strategies that help decrease their incidence. 相似文献
3.
4.
Richard G. Forbes 《Surface science》1981,108(2):311-328
The effects of imaging-gas hyperpolarisability and field-gradient polarisabuity terms on field-adsorption binding energies have been explored. At best image fields for the noble imaging gases and molecular hydrogen, the correction to long-range binding energy is at most a few percent and may be neglected. At the tungsten evaporation field the correction is significant in the cases of Ar, Kr, H2, and especially Xe. The system He on W(111) has been used as a paradigm in the investigation of short-range binding energy. The largest correction here is due to one of the field-gradient polarisabuity terms. In the field range of most relevance to the field-ion techniques the total correction is about 15–20%, and should not be neglected in detailed treatments. 相似文献
5.
Abstract— Skin tumors were induced in hairless mutant mice following a single exposure to ultraviolet radiation (UV). Tumors were first noted as early as 7 weeks following irradiation. The UV, emitted by FS20/40T12 fluorescent lamps, was principally in the 280–320 nm spectral region with a peak at 313 nm. Single (skin surface) doses of 3 times 104 J/m2 to 24 times 104 J/m2 were delivered in 3 h or less. The higher doses resulted in more severe acute damage as well as greater tumor yield. Most of the tumors were benign hyperplastic epithelial papillomas; 4 out of 96 tumors examined histologically proved to be squamous cell carcinomas. This appears to be the first report of experimental carcinogenesis due to a single UV exposure, not requiring exogenous chemical promotion. 相似文献
6.
The combination of ethyl diazoacetate with aryl aldehydes in the presence of copper(I) or rhodium(II) catalysts results in
the formation of 1,3-dioxolane products in moderate to good yields. These reactions occur through a pathway that involves
ylide intermediates. Catalyst-dependent diastereocontrol is observed and suggests that metal-associated ylides are involved
in the product-determining step. The influence of aryl aldehyde substituents has been determined.
Current address.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 961–965, May, 1998. 相似文献
7.
Tarasov VF Forbes MD 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(2):245-263
A new approach to the theory of the EPR of spin correlated radical pairs (SCRP) is formulated. It is based on spectral exchange methods as applied to the two-site model and takes into account explicitly both the motion of one quantum (transverse magnetization) and two quantum coherences (polarizations) of SCRPs. This innovation allows for the interpretation of anti phase structure (APS) spectral shape asymmetry and for the transformation of the initially created ST0RPM polarization into the APS spectral pattern. The results of this method as applied to micellized spin correlated radical pairs have been compared with the exact numerical solution of the corresponding stochastic Liouville equation and is commented on. 相似文献
8.
The total synthesis of rac-sceletium alkaloid A41a and of its 3'-demethoxy analogue 1b via the annulation of endocyclic enamines 4a–b is presented. The Michael acceptor 5a is a useful synthon for the two-step synthesis of 2,3-disubstituted pyridines from Δ2-pyrrolines. 相似文献
9.
An action spectrum for UV photocarcinogenesis 总被引:5,自引:0,他引:5
10.