全文获取类型
收费全文 | 37555篇 |
免费 | 6103篇 |
国内免费 | 5004篇 |
专业分类
化学 | 26760篇 |
晶体学 | 591篇 |
力学 | 2336篇 |
综合类 | 453篇 |
数学 | 4307篇 |
物理学 | 14215篇 |
出版年
2024年 | 106篇 |
2023年 | 664篇 |
2022年 | 1190篇 |
2021年 | 1259篇 |
2020年 | 1411篇 |
2019年 | 1399篇 |
2018年 | 1189篇 |
2017年 | 1218篇 |
2016年 | 1731篇 |
2015年 | 1718篇 |
2014年 | 2073篇 |
2013年 | 2681篇 |
2012年 | 3246篇 |
2011年 | 3260篇 |
2010年 | 2316篇 |
2009年 | 2314篇 |
2008年 | 2565篇 |
2007年 | 2353篇 |
2006年 | 2262篇 |
2005年 | 1807篇 |
2004年 | 1545篇 |
2003年 | 1279篇 |
2002年 | 1303篇 |
2001年 | 1111篇 |
2000年 | 907篇 |
1999年 | 903篇 |
1998年 | 691篇 |
1997年 | 561篇 |
1996年 | 559篇 |
1995年 | 492篇 |
1994年 | 442篇 |
1993年 | 411篇 |
1992年 | 318篇 |
1991年 | 274篇 |
1990年 | 274篇 |
1989年 | 198篇 |
1988年 | 144篇 |
1987年 | 106篇 |
1986年 | 116篇 |
1985年 | 83篇 |
1984年 | 43篇 |
1983年 | 43篇 |
1982年 | 39篇 |
1981年 | 25篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1957年 | 5篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
Ionics - This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solid-state potentiometric sensor on an yttria-stabilized zirconia (YSZ)... 相似文献
13.
14.
15.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry 下载免费PDF全文
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
16.
17.
Yaping Chen Dr. Kun Rui Prof. Jixin Zhu Prof. Shi Xue Dou Dr. Wenping Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):703-713
Developing clean and sustainable energies as alternatives to fossil fuels is in strong demand within modern society. The oxygen evolution reaction (OER) is the efficiency-limiting process in plenty of key renewable energy systems, such as electrochemical water splitting and rechargeable metal–air batteries. In this regard, ongoing efforts have been devoted to seeking high-performance electrocatalysts for enhanced energy conversion efficiency. Apart from traditional precious-metal-based catalysts, nickel-based compounds are the most promising earth-abundant OER catalysts, attracting ever-increasing interest due to high activity and stability. In this review, the recent progress on nickel-based oxide and (oxy)hydroxide composites for water oxidation catalysis in terms of materials design/synthesis and electrochemical performance is summarized. Some underlying mechanisms to profoundly understand the catalytic active sites are also highlighted. In addition, the future research trends and perspectives on the development of Ni-based OER electrocatalysts are discussed. 相似文献
18.
Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by NaNO2 and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics. 相似文献
19.
20.
We employ a first-principles plane wave method with the
relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter
(HGH) scheme in the frame of DFT to calculate
the equilibrium lattice parameters and the thermodynamic properties of
AlB2 compound with hcp structure. The obtained lattice parameters are in
good agreement with the available experimental data and those calculated by
others. Through the quasi-harmonic Debye model, obtained successfully are
the dependences of the
normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized
primitive cell volume V/V0 on pressure P, the variation of the thermal
expansion α with pressure P and temperature T, as well as the Debye
temperature \ThetaD and the heat capacity CV on pressure P and
temperature T. 相似文献