全文获取类型
收费全文 | 27773篇 |
免费 | 1055篇 |
国内免费 | 160篇 |
专业分类
化学 | 18733篇 |
晶体学 | 260篇 |
力学 | 958篇 |
综合类 | 1篇 |
数学 | 2422篇 |
物理学 | 6614篇 |
出版年
2023年 | 153篇 |
2022年 | 310篇 |
2021年 | 495篇 |
2020年 | 446篇 |
2019年 | 463篇 |
2018年 | 351篇 |
2017年 | 330篇 |
2016年 | 762篇 |
2015年 | 664篇 |
2014年 | 833篇 |
2013年 | 1554篇 |
2012年 | 2016篇 |
2011年 | 2222篇 |
2010年 | 1337篇 |
2009年 | 1174篇 |
2008年 | 1787篇 |
2007年 | 1695篇 |
2006年 | 1573篇 |
2005年 | 1477篇 |
2004年 | 1293篇 |
2003年 | 1012篇 |
2002年 | 1003篇 |
2001年 | 690篇 |
2000年 | 583篇 |
1999年 | 343篇 |
1998年 | 257篇 |
1997年 | 299篇 |
1996年 | 336篇 |
1995年 | 262篇 |
1994年 | 276篇 |
1993年 | 307篇 |
1992年 | 271篇 |
1991年 | 210篇 |
1990年 | 161篇 |
1989年 | 145篇 |
1988年 | 144篇 |
1987年 | 122篇 |
1986年 | 97篇 |
1985年 | 171篇 |
1984年 | 113篇 |
1983年 | 100篇 |
1982年 | 124篇 |
1981年 | 88篇 |
1980年 | 80篇 |
1978年 | 82篇 |
1977年 | 86篇 |
1976年 | 95篇 |
1975年 | 103篇 |
1974年 | 79篇 |
1973年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
Mathiazhagan C Molzon WR Cousins RD Konigsberg J Kubic J Melese P Rubin P Slater WE Wagner D Hart GW Kinnison WW Lee DM McKee RJ Milner EC Sanders GH Ziock HJ Arisaka K Knibbe P Urheim J Axelrod S Biery KA Irwin GM Lang K Margulies J Ouimette DA Ritchie JL Trang QH Wojcicki SG Auerbach LB Buchholz P Highland VL McFarlane WK Sivertz M Chapman MD Eckhause M Ginkel JF Hancock AD Joyce D Kane JR Kenney CJ Vulcan WF Welsh RE Whyley RJ Winter RG 《Physical review letters》1989,63(20):2181-2184
183.
184.
Lee SH 《Physical review D: Particles and fields》1989,40(7):2484-2486
185.
The effect of CuO on the thermal behaviour of Zr/KClO4 primer mixtures was studied by thermoanalytical techniques, and the Bruceton method and its related calculation. It was found that the CuO catalytically promoted the decomposition of Zr/KClO4 primer mixtures and shifted the exothermic peak of DSC curves to lower temperatures. In addition, the Zr/KClO4 primer mixture containing CuO had a significant effect on the firing characteristics of electro-explosive devices. 相似文献
186.
A new caffeoyl quinic acid from aster scaber and its inhibitory activity against human immunodeficiency virus-1 (HIV-1) integrase 总被引:1,自引:0,他引:1
Kwon HC Jung CM Shin CG Lee JK Choi SU Kim SY Lee KR 《Chemical & pharmaceutical bulletin》2000,48(11):1796-1798
The phytochemical study of the aerial parts of Aster scaber Thunb. (Asteraceae) yielded a new caffeoyl quinic acid, (-) 3,5-dicaffeoyl-muco-quinic acid (2) and three known compounds, (-) 3,5-dicaffeoyl quinic acid (1), (-) 4,5-dicaffeoyl quinic acid (3), (-) 5-caffeoyl quinic acid (4). The structures were established by high resolution spectroscopic methods. The antiviral effects against HIV-1 integrase of the compounds was evaluated. (-) 3,5-Dicaffeoyl-muco-quinic acid (2) exhibited potent antiviral activity with an IC50 value of 7.0 +/- 1.3 microg/ml. 相似文献
187.
Song Hyung Keun Lee Hwaung Choi Jae-Wook Na Byung-ki 《Plasma Chemistry and Plasma Processing》2004,24(1):57-72
Methane conversion using an electric discharge has been studied for many years. Recently, many research groups have developed high-frequency pulsed plasma reaction for methane conversion to higher hydrocarbons and synthesis gas. CO2 reforming of methane to synthesis gas has also attracted considerable interest as a method of utilization of the greenhouse gases, CO2 and CH4, which occupy most of man-made greenhouse gases. In this study, the influence of pulse form of applied voltage on methane and carbon dioxide conversions and product selectivity has been investigated using a cylindrical type DBD reactor. For this purpose, two kinds of power supply were compared, that is, AC power supply which has a high-frequency sinusoidal wave form, and AC pulse power supply which has modified AC pulse wave form. The conversions of methane and carbon dioxide were enhanced using pulsed plasma. The lower pulse width was more profitable economically. 相似文献
188.
Yun SH Sohn BH Jung JC Zin WC Lee JK Song O 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6548-6552
Hexagonal arrangement of iron oxide nanoparticles was fabricated by utilizing a single-layered film of diblock copolymer micelles. The synthesis was directly performed on the solid substrate by oxygen plasma with preserving the dimensional order of micelles so that separate procedures for synthesis and deposition of nanoparticles were not necessary. Since the oxygen plasma treatment also eliminated polymers, pure patterns of iron oxide nanoparticles were obtained. Moreover, easy control over the size of nanoparticles enabled us to selectively create a ferrimagnetic or a superparamagnetic pattern of iron oxide nanoparticles without altering the fabrication process. 相似文献
189.
Appleby I Boulton LT Cobley CJ Hill C Hughes ML de Koning PD Lennon IC Praquin C Ramsden JA Samuel HJ Willis N 《Organic letters》2005,7(10):1931-1934
Two methods to produce (2S)-5-amino-2-(1-n-propyl-1H-imidazol-4-ylmethyl)-pentanoic acid were investigated. Diastereoisomeric salt resolution, using the quinidine salt, gave the desired intermediate in 98% ee and 33% yield. Asymmetric hydrogenation of various substrates gave high conversions, with up to 83% ee. Integration of these two approaches via asymmetric hydrogenation of a quinidine salt substrate followed by crystallization provided the desired intermediate in 94% ee and 76% yield. 相似文献
190.
Ji-Hyun Seo Ju-Woon Lee Jae-Hun Kim Eui-Baek Byun Soo-Young Lee Il-Jun Kang Myung-Woo Byun 《Radiation Physics and Chemistry》2007,76(11-12):1855-1857
Egg allergy is one of the most serious of the immediate hypersensitivity reactions to foods. Such an allergic disorder is mediated by IgE antibodies stimulated by T-helper type 2 (Th2) lymphocytes. This study was undertaken to evaluate changes of allergenicity and cytokine profiles by exposure of irradiated ovalbumin (OVA), a major allergen of egg white, in the OVA-allergic mice model. OVA solutions (2 mg/ml in 0.01 M phosphate buffered saline (PBS) were gamma-irradiated to 50 and 100 kGy. The allergenicity in the OVA-allergy-induced mice model was remarkably reduced when challenged with irradiated OVA. Cultures of spleen cells harvested from OVA-sensitized mice showed a significant decrease in Th2 cytokine levels of ILs-4 and -5 with a concomitant increase in Th1 cytokine levels of IL-12 when co-cultured with irradiated OVA. However, IFN-γ level decreased dependant on the radiation dose of co-cultured OVA. The levels of IgEs and Th2-cytokine were reduced dependant on the radiation dose. These data show that the irradiated OVA could downregulate the activity of Th2 lymphocytes in OVA-sensitized mice. 相似文献