全文获取类型
收费全文 | 21519篇 |
免费 | 4181篇 |
国内免费 | 3190篇 |
专业分类
化学 | 15692篇 |
晶体学 | 299篇 |
力学 | 1336篇 |
综合类 | 302篇 |
数学 | 2590篇 |
物理学 | 8671篇 |
出版年
2024年 | 55篇 |
2023年 | 386篇 |
2022年 | 749篇 |
2021年 | 760篇 |
2020年 | 910篇 |
2019年 | 893篇 |
2018年 | 768篇 |
2017年 | 730篇 |
2016年 | 1014篇 |
2015年 | 1092篇 |
2014年 | 1327篇 |
2013年 | 1634篇 |
2012年 | 1971篇 |
2011年 | 2062篇 |
2010年 | 1484篇 |
2009年 | 1497篇 |
2008年 | 1595篇 |
2007年 | 1388篇 |
2006年 | 1307篇 |
2005年 | 1088篇 |
2004年 | 910篇 |
2003年 | 695篇 |
2002年 | 704篇 |
2001年 | 601篇 |
2000年 | 470篇 |
1999年 | 420篇 |
1998年 | 329篇 |
1997年 | 332篇 |
1996年 | 287篇 |
1995年 | 241篇 |
1994年 | 224篇 |
1993年 | 161篇 |
1992年 | 113篇 |
1991年 | 129篇 |
1990年 | 110篇 |
1989年 | 76篇 |
1988年 | 75篇 |
1987年 | 64篇 |
1986年 | 46篇 |
1985年 | 33篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1959年 | 5篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The interactions between bovine serum albumin (BSA) and polymer (poly (METAC-co-NIPAm-co-Eu(AA)3Phen), PMNEu) containing rare earth element (Europium) were detailedly investigated by both of experimental techniques, such as fluorescence spectroscopic analysis, zeta-potential characterization, hydrodynamic size measurements and transmission electron microscopy (TEM) observation, and theoretical calculations. As a result, we concluded that PMNEu could interact with BSA through electrostatic force and quench the fluorescence of BSA, which was regarded as the static quenching mechanism. In addition, the binding constant and binding sites number of BSA with PMNEu were calculated, and the distance between PMNEu and BSA was also estimated to be 1.9?nm based on Föster’s theory. Furthermore, the two fluorescence peaks of PMNEu at 594?nm and 618?nm were detected, and the density of them increased with the more BSA being added to couple with PMNEu. Additionally, The zeta-potential results confirmed the electrostatic interaction mode between BSA and PMNEu, which was concluded with the previous thermodynamic analysis. At last, the results from the hydrodynamic size measurement had a good agreement with those from the TEM observation about the structure and size variation during the complexation of PMNEu with different concentrations of BSA. 相似文献
992.
In this paper, the existence and multiplicity of positive solutions is established for Schrödinger‐Poisson system of the form where 0 ∈ Ω is a smooth bounded domain in , , and λ > 0 is a real parameter. Combining with the variational method and Nehari manifold method, two positive solutions of the system are obtained. 相似文献
993.
Rui Feng Zi-Ying Li Zhao-Quan Yao Zi-Ang Guo Yi-Nan Zhang Hao-Xiang Sun Wei Li Xian-He Bu 《中国科学:化学(英文版)》2022,65(1):128-134
The rational designability and chemical tunability of metal-organic frameworks(MOFs)are enabling tributes to efficaciously enhance their room temperature phosphorescence(RTP)performance.A family of stable anionic MOFs,[Zn2(4,5-ImDC)2]M2(NKU-132,M=(CH3)2NH2or(CH2CH3)2NH2),featuring significant RTP have been synthesized.By rational cation selection and in-situ replacement from dimethylammonium to diethylammonium,the phosphorescence lifetime is increased from 30.88 to126.3 ms,along with less sensitivity to air.This work provides an anti-quenching and lifetime tuning example for RTP-MOFmaterials via facile host-guest chemistry. 相似文献
994.
Fangyuan Zhou Lesong Li Kao Lin Feng Zhang Prof. Dr. Guo-Jun Deng Dr. Hang Gong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4246-4250
The radical–radical coupling reaction is an important synthetic strategy. In this study, the iron-catalyzed radical–radical cross-coupling reaction based on the decarboxylation of keto acids and decarbonylation of aliphatic aldehydes to obtain valuable aryl ketones is reported for the first time. Remarkably, when tertiary aldehydes were used as carbonyl sources, ketone esters were selectively obtained instead of ketones. The gram-scale preparation of aryl ketone through this strategy was easily achieved by using only 3 mol % of the iron catalyst. As a proof-of-concept, the bioactive molecule flurprimidol was synthesized in two steps by using this strategy. 相似文献
995.
996.
997.
998.
999.
1000.
Yu‐Feng Liang Ning Jiao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(2):558-562
A transition‐metal‐free Cs2CO3‐catalyzed α‐hydroxylation of carbonyl compounds with O2 as the oxygen source is described. This reaction provides an efficient approach to tertiary α‐hydroxycarbonyl compounds, which are highly valued chemicals and widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very environmentally friendly and practical. This transformation is highly efficient and highly selective for tertiary C(sp3) H bond cleavage. 相似文献