全文获取类型
收费全文 | 125189篇 |
免费 | 20654篇 |
国内免费 | 16307篇 |
专业分类
化学 | 89246篇 |
晶体学 | 1647篇 |
力学 | 7210篇 |
综合类 | 1084篇 |
数学 | 15792篇 |
物理学 | 47171篇 |
出版年
2024年 | 276篇 |
2023年 | 2339篇 |
2022年 | 3455篇 |
2021年 | 4237篇 |
2020年 | 4924篇 |
2019年 | 4813篇 |
2018年 | 4306篇 |
2017年 | 4061篇 |
2016年 | 5900篇 |
2015年 | 5830篇 |
2014年 | 7117篇 |
2013年 | 9384篇 |
2012年 | 11169篇 |
2011年 | 11671篇 |
2010年 | 8366篇 |
2009年 | 8080篇 |
2008年 | 8592篇 |
2007年 | 7595篇 |
2006年 | 7221篇 |
2005年 | 6130篇 |
2004年 | 4820篇 |
2003年 | 3901篇 |
2002年 | 3729篇 |
2001年 | 3066篇 |
2000年 | 2654篇 |
1999年 | 2585篇 |
1998年 | 2130篇 |
1997年 | 1823篇 |
1996年 | 1818篇 |
1995年 | 1605篇 |
1994年 | 1482篇 |
1993年 | 1200篇 |
1992年 | 1034篇 |
1991年 | 940篇 |
1990年 | 778篇 |
1989年 | 585篇 |
1988年 | 451篇 |
1987年 | 383篇 |
1986年 | 380篇 |
1985年 | 326篇 |
1984年 | 214篇 |
1983年 | 185篇 |
1982年 | 145篇 |
1981年 | 101篇 |
1980年 | 71篇 |
1979年 | 38篇 |
1978年 | 29篇 |
1976年 | 24篇 |
1975年 | 25篇 |
1957年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Wei‐Lie Xiao Jian‐Xin Pu Rui‐Rui Wang Liu‐Meng Yang Xiao‐Li Li Sheng‐Hong Li Rong‐Tao Li Sheng‐Xiong Huang Yong‐Tang Zheng Han‐Dong Sun 《Helvetica chimica acta》2007,90(8):1505-1513
Seven new highly oxygenated nortriterpenoids, rubriflorins D–J ( 1 – 7 ), were isolated from the leaves and stems of Schisandra rubriflora, and their structures were elucidated on the basis of extensive analysis of spectroscopic data. These new compounds feature the opening of ring A compared with related known nortriterpenoids isolated from the genus Schisandra and showed weak activity against HIV‐1. 相似文献
992.
993.
Zhao‐Peng Deng Shan Gao Li‐Hua Huo Hui Zhao 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m225-m227
In the title complex, [Mn(SO4)(C3H7NO)(H2O)2]n, each MnII ion has a distorted octahedral geometry formed by three O atoms of three different sulfate groups, one O atom of a dimethylformamide ligand and two water molecules. The sulfate groups act as tridentate bridging ligands connecting the MnII ions into a two‐dimensional layer structure which can be regraded as a 4.82 network. 相似文献
994.
995.
996.
Guan Wu WANG* Li Juan JIAO Er Hong HAO Yong Ming LU You Jun YANG Department of Chemistry University of Science Technology of China Hefei 《中国化学快报》2004,15(5)
Water-soluble fullerenes not only have a number of important applications in biological chemistry1, but also form ordered aggregate structures that can be utilized in materials science2. There are reports that some water-soluble fullerene derivatives can form ordered structures in water, such as vesicle, nanorod and nanoparticle2-5. However, relatively few reports on the aggregation process have been reported. Knowledge of factors that affect the cluster formation in solution is of consider… 相似文献
997.
X-ray absorption spectra of plasmas 总被引:1,自引:0,他引:1
In this paper we present a theoretical method to calculate the absorption spectra of hot dense plasmas. Based on our fully relativistic treatment incorporated with the quantum defect theory to handle the huge number of transition arrays from many configurations with high principal quantum number, we can calculate the absorption spectra for any element or multi-element plasmas with little computational efforts. We calculate the absorption spectra of C10H1605 plasmas, which are in good agreement with the experimental spectra. We can then provide diagnostic analysis for plasmas in relevant inertial confinement fusion (lCF) experiments; namely not only to determine plasmas' temperatures and densities, but also to provide the population densities of various ionic stages. Our theoretical method verified by "benchmark experiments" will be a basic tool to provide "precise" opacity data for the ICF research.`` 相似文献
998.
Jian-Shu Li 《Mathematische Annalen》1992,292(1):747-761
Supported in part by NSF grant No. DMS-9003999 相似文献
999.
The yield and stereoselectivity of the Diels-Alder reactions between furan(or 2-methylfuran)and different dienophiles are markedly enhanced by the catalysis of anhydrous YbCl3. 相似文献
1000.
用ESR方法研究了红薯淀粉在γ射线预辐照下,产生的淀粉自由基特性及其室温下的自由基衰减动力学反应。结果表明在室温条件下,淀粉自由基的相对浓度随辐射剂量的增大而增加。自由基相对浓度的室温衰减用二级反应动力学处理,求得了衰减速率常数和淀粉自由基反应的半衰期。 相似文献