全文获取类型
收费全文 | 26905篇 |
免费 | 5163篇 |
国内免费 | 6967篇 |
专业分类
化学 | 20249篇 |
晶体学 | 818篇 |
力学 | 1773篇 |
综合类 | 517篇 |
数学 | 3413篇 |
物理学 | 12265篇 |
出版年
2024年 | 54篇 |
2023年 | 453篇 |
2022年 | 873篇 |
2021年 | 977篇 |
2020年 | 1116篇 |
2019年 | 1143篇 |
2018年 | 970篇 |
2017年 | 1167篇 |
2016年 | 1178篇 |
2015年 | 1406篇 |
2014年 | 1662篇 |
2013年 | 2211篇 |
2012年 | 2414篇 |
2011年 | 2534篇 |
2010年 | 2097篇 |
2009年 | 2224篇 |
2008年 | 2380篇 |
2007年 | 2100篇 |
2006年 | 2028篇 |
2005年 | 1662篇 |
2004年 | 1296篇 |
2003年 | 937篇 |
2002年 | 896篇 |
2001年 | 841篇 |
2000年 | 903篇 |
1999年 | 581篇 |
1998年 | 381篇 |
1997年 | 335篇 |
1996年 | 307篇 |
1995年 | 258篇 |
1994年 | 236篇 |
1993年 | 245篇 |
1992年 | 196篇 |
1991年 | 148篇 |
1990年 | 145篇 |
1989年 | 122篇 |
1988年 | 109篇 |
1987年 | 89篇 |
1986年 | 68篇 |
1985年 | 52篇 |
1984年 | 38篇 |
1983年 | 41篇 |
1982年 | 25篇 |
1981年 | 28篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1971年 | 8篇 |
1965年 | 15篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
The study of ionic organotin compounds is of current attention owing to their diversified molecular structures and wide range of applications.[1~3] In this paper, we concluded our works on ionic organotin compounds. 相似文献
73.
74.
A G 4.0 dendrimer-like poly (amido amine) (PAMAM) based on silica nanoparticles was fabricated via a divergent approach.It was built from γ-aminopropyi silica nanoparfides (APSN) core via repetitive addition of acrylate (MA) and hexylenediamine (HDA). FT-IR and EA were used to monitor the progress of dendrimer during each step. The amino group content of the resulting product increased from 0.49 to 3.72 mmol/g after the 4th generation. In addition, the percentage of grafting increased with increasing generation and reached to 65.9% after 4th generation. It was found that the resulting silica nanoparticles could be dispersed in methanol with a mean hydrodynamic particle diameter of 152.7 nm although the silica nanoparticles had agglomerated during the storage period. 相似文献
75.
Deposition of Hydrogen-Free Silicon Nitride Thin Films by Microwave ECR plasma Enhanced Magnetron Sputtering at Room Temperature 下载免费PDF全文
Hydrogen-free silicon nitride (SiNx) films were deposited at room temperature by microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalance magnetron sputtering system. Both Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy are used to study the bonding type and the change of bonding structures of the silicon nitride films. The results indicate that the chemical structure and composition of SiNx films deposited by this technique depend strongly on the N2 flow rates, the stoichiometric SiNx film, which has the highest hardness of 22.9 GPa, could be obtained at lower N2 flow rate of 4 sccm. 相似文献
76.
弱拓扑和强可容许拓扑之间的一个关系 总被引:2,自引:0,他引:2
本文对局部凸空间X及其对偶X′,建立了弱拓扑σ(X,X′)和强拓扑β(X,X′)之间的一个新关系,改进了有关(X,X′)--可容许拓扑全体上的不变性结果。 相似文献
77.
两部美国大学物理教材对我们教学改革的启示 总被引:9,自引:1,他引:8
介绍了美国两部大学物理教材的特点,分析了美国教材在教学内容、教学方法、教学手段现代化方面的特色,为我们的教学改革提供一些可供借鉴的经验。 相似文献
78.
Wang Qing-Lun Zhao Bin Liao Dai-Zheng Yan Shi-Ping Cheng Peng Jiang Zong-Hui 《Transition Metal Chemistry》2003,28(3):326-330
The copper(II) complex Na2[Cu(pba)] · 6H2O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na+ bridge in the same layer. 相似文献
79.
80.
SUN Qiyu 《数学年刊B辑(英文版)》2003,24(3):367-386
In this paper, the author at first develops a method to study convergence of the cascade algorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), and then applies the previous result on the convergence to characterizing compactly supported refinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems 3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriate initial to guarantee the convergence of the cascade algorithm (see Theorem 4.2). 相似文献