全文获取类型
收费全文 | 391829篇 |
免费 | 4787篇 |
国内免费 | 1685篇 |
专业分类
化学 | 211118篇 |
晶体学 | 4983篇 |
力学 | 17914篇 |
综合类 | 53篇 |
数学 | 43895篇 |
物理学 | 120338篇 |
出版年
2020年 | 3223篇 |
2019年 | 3503篇 |
2018年 | 4478篇 |
2017年 | 4446篇 |
2016年 | 6767篇 |
2015年 | 4219篇 |
2014年 | 6586篇 |
2013年 | 16378篇 |
2012年 | 12522篇 |
2011年 | 15443篇 |
2010年 | 10857篇 |
2009年 | 10609篇 |
2008年 | 14160篇 |
2007年 | 14385篇 |
2006年 | 13501篇 |
2005年 | 12223篇 |
2004年 | 11009篇 |
2003年 | 9925篇 |
2002年 | 9840篇 |
2001年 | 10761篇 |
2000年 | 8402篇 |
1999年 | 6560篇 |
1998年 | 5715篇 |
1997年 | 5660篇 |
1996年 | 5276篇 |
1995年 | 4914篇 |
1994年 | 5034篇 |
1993年 | 4596篇 |
1992年 | 5275篇 |
1991年 | 5369篇 |
1990年 | 5114篇 |
1989年 | 4992篇 |
1988年 | 5015篇 |
1987年 | 4846篇 |
1986年 | 4480篇 |
1985年 | 5949篇 |
1984年 | 6323篇 |
1983年 | 5257篇 |
1982年 | 5545篇 |
1981年 | 5376篇 |
1980年 | 5280篇 |
1979年 | 5373篇 |
1978年 | 5818篇 |
1977年 | 5649篇 |
1976年 | 5739篇 |
1975年 | 5354篇 |
1974年 | 5478篇 |
1973年 | 5586篇 |
1972年 | 3886篇 |
1971年 | 3333篇 |
排序方式: 共有10000条查询结果,搜索用时 363 毫秒
81.
82.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献
83.
84.
85.
86.
87.
88.
G. Grätzer 《Algebra Universalis》2015,74(3-4):351-359
89.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
90.