全文获取类型
收费全文 | 19793篇 |
免费 | 3432篇 |
国内免费 | 2433篇 |
专业分类
化学 | 14607篇 |
晶体学 | 194篇 |
力学 | 1392篇 |
综合类 | 124篇 |
数学 | 2245篇 |
物理学 | 7096篇 |
出版年
2024年 | 38篇 |
2023年 | 400篇 |
2022年 | 430篇 |
2021年 | 618篇 |
2020年 | 761篇 |
2019年 | 726篇 |
2018年 | 652篇 |
2017年 | 592篇 |
2016年 | 1043篇 |
2015年 | 914篇 |
2014年 | 1179篇 |
2013年 | 1458篇 |
2012年 | 1814篇 |
2011年 | 1770篇 |
2010年 | 1287篇 |
2009年 | 1183篇 |
2008年 | 1337篇 |
2007年 | 1186篇 |
2006年 | 1100篇 |
2005年 | 956篇 |
2004年 | 712篇 |
2003年 | 617篇 |
2002年 | 716篇 |
2001年 | 599篇 |
2000年 | 440篇 |
1999年 | 441篇 |
1998年 | 353篇 |
1997年 | 288篇 |
1996年 | 315篇 |
1995年 | 303篇 |
1994年 | 232篇 |
1993年 | 157篇 |
1992年 | 169篇 |
1991年 | 172篇 |
1990年 | 149篇 |
1989年 | 117篇 |
1988年 | 100篇 |
1987年 | 83篇 |
1986年 | 61篇 |
1985年 | 52篇 |
1984年 | 39篇 |
1983年 | 26篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1972年 | 3篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We developed two DNA-conjugated polymers, one based on polyallylamine and the other on polyacrylic acid, for use in DNA chips. A 30-mer single-stranded DNA probe and thioctic acid were covalently attached to polyallylamine as sidechains. The same single-stranded DNA and 3-(pyridyldithio)propionyl hydrazide were covalently attached to polyacrylic acid as sidechains. Both DNA-conjugated polymers could be specifically immobilized onto a gold sensor substrate by a self-assembly technique. The interactions between fully matched DNA and each DNA-conjugated polymer were investigated by surface plasmon resonance. A gold surface modified with either DNA-conjugated polymer recognized fully matched DNA much better than unmatched DNA. The hybridization selectivity and efficiency of DNA-conjugated polyallylamine was optimized by adjusting the pH so as to reduce the effects of cationic polymer sidechains. The hybridization selectivity and efficiency of DNA-conjugated polymers were higher than those of a conventional immobilized thiol-based DNA. The coating of DNA-conjugated polymers reduced nonspecific adsorption of DNA by the gold substrate. DNA-conjugated polyacrylic acid was more selective toward fully matched DNA than was DNA-conjugated polyallylamine. Therefore, DNA-conjugated polymers show promise for application in novel DNA chips. 相似文献
62.
63.
64.
以PCl3为脱水剂,将邻氨基硫酚与水杨酸脱水环化合成出2-(2-羟基苯基)苯并噻唑,并进一步将所得产物与乙酸锌反应合成出2-(2-羟基苯基)苯并噻唑螯合锌(Zn(BTZ)2)材料。以该配合物作为发光层制备出结构为ITO/PVK:TPD/Zn(BTZ)2/Al近白色电致发光器件,其色坐标位于白场之内(x=0.242,y=0.359),在驱动电压为16V时,亮度达3200cdm2,对应的量子效率为0.32%。进一步在Zn(BTZ)2中掺入橙红色染料Rubrene,制成ITO/PVK:TPD/Zn(BTZ)2:Rubrene/Al结构器件,实现了纯白色发光(色坐标值:x=0.324,y=0.343),非常接近于白色等能点,且量子效率达0.47%。最后对上述器件的发光和电学性能进行了深入的研究和探讨。 相似文献
65.
Baker‘s yeast mediated reduction of optically active diketone is described. The two keto groups are efficiently differentiated and the ee value of the recovered material is considerably raised. It affords highly optically active key intermediates efficiently for the synthesis of natural polyhydroxylated agarofuran products. 相似文献
66.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
67.
Continuous dependence on a modelling parameter is established for solutions of a problem for a complex Ginzburg–Landau equation. A homogenizing boundary condition is also used to discuss the continuous dependence results. We derive a priori estimates that indicate that solutions depend continuously on a parameter in the governing differential equation. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
68.
69.
70.