全文获取类型
收费全文 | 4583篇 |
免费 | 218篇 |
国内免费 | 140篇 |
专业分类
化学 | 3096篇 |
晶体学 | 53篇 |
力学 | 102篇 |
综合类 | 12篇 |
数学 | 628篇 |
物理学 | 1050篇 |
出版年
2023年 | 28篇 |
2022年 | 35篇 |
2021年 | 41篇 |
2020年 | 72篇 |
2019年 | 72篇 |
2018年 | 58篇 |
2017年 | 61篇 |
2016年 | 121篇 |
2015年 | 101篇 |
2014年 | 124篇 |
2013年 | 222篇 |
2012年 | 240篇 |
2011年 | 246篇 |
2010年 | 156篇 |
2009年 | 169篇 |
2008年 | 198篇 |
2007年 | 232篇 |
2006年 | 177篇 |
2005年 | 199篇 |
2004年 | 159篇 |
2003年 | 117篇 |
2002年 | 126篇 |
2001年 | 81篇 |
2000年 | 107篇 |
1999年 | 102篇 |
1998年 | 75篇 |
1997年 | 89篇 |
1996年 | 86篇 |
1995年 | 57篇 |
1994年 | 78篇 |
1993年 | 78篇 |
1992年 | 78篇 |
1991年 | 53篇 |
1990年 | 44篇 |
1989年 | 46篇 |
1988年 | 43篇 |
1987年 | 56篇 |
1986年 | 69篇 |
1985年 | 60篇 |
1984年 | 48篇 |
1983年 | 50篇 |
1982年 | 67篇 |
1981年 | 41篇 |
1980年 | 63篇 |
1979年 | 46篇 |
1978年 | 42篇 |
1977年 | 45篇 |
1976年 | 47篇 |
1975年 | 46篇 |
1974年 | 27篇 |
排序方式: 共有4941条查询结果,搜索用时 15 毫秒
31.
32.
33.
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
34.
Mironov YV Yarovoi SS Naumov DY Kozlova SG Ikorsky VN Kremer RK Simon A Fedorov VE 《The journal of physical chemistry. B》2005,109(50):23804-23807
The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect. 相似文献
35.
Baolong Li Jiangang Ding Jianping Lang Zheng Xu Jiutong Chen 《Journal of Molecular Structure》2002,616(1-3)
The complex [Ni(tn)2{N(CN)2}]ClO4 (tn=trimethylenediamine) has been synthesized and the structure has been determined. The complex forms a one-dimensional chain structure via the bidentate bridging ligand dicyanamide. A two-dimensional networks is formed via interchain hydrogen bond interactions. 相似文献
36.
CuAl2Cl8. Preparation and Crystal Structure. Crystals of CuAl2Cl8 have been prepared. Their remission spectrum agrees with that of gaseous CuAl2Cl8. The crystal structure (P21/c;a = 6.614, b = 7.376, c = 12.319 Å; β = 94.11°) shows a molecular lattice with Cu in square planar coordination, which is completed to a stretched octahedron (as in solid CuCl2) by two Cl atoms from neighbour molecules. Al has tetrahedral coordination. 相似文献
37.
LIU Langa JI Ya-Lia JIA Dian-Zenga② YU Kai-Beib a 《结构化学》2003,22(5):568-572
1 INTRODUCTION In recent years, investigations on the com- pounds containing hydrazide or hydrazone moieties have been increased considerably because of their potentially biological activities, especially as poten- tial inhibitors for many enzymes[1~5]. The presence of weak molecular interactions such as hydrogen- bonding controls the conformational and structural features which are important to the drug action[6, 7]. We have synthesized the photochromic compounds of pyrazolone thiosemi… 相似文献
38.
39.
40.
γ-Lactone-cis-annulation to Δ2- and Δ3- Cholestene. From Δ2- and Δ3- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The 13C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported. 相似文献