全文获取类型
收费全文 | 144833篇 |
免费 | 11583篇 |
国内免费 | 8353篇 |
专业分类
化学 | 71911篇 |
晶体学 | 1538篇 |
力学 | 10761篇 |
综合类 | 628篇 |
数学 | 39335篇 |
物理学 | 40596篇 |
出版年
2024年 | 174篇 |
2023年 | 1287篇 |
2022年 | 1663篇 |
2021年 | 2253篇 |
2020年 | 2693篇 |
2019年 | 2725篇 |
2018年 | 12162篇 |
2017年 | 11836篇 |
2016年 | 8957篇 |
2015年 | 3938篇 |
2014年 | 4268篇 |
2013年 | 5401篇 |
2012年 | 9770篇 |
2011年 | 16576篇 |
2010年 | 9777篇 |
2009年 | 10088篇 |
2008年 | 11088篇 |
2007年 | 12722篇 |
2006年 | 4171篇 |
2005年 | 4533篇 |
2004年 | 4020篇 |
2003年 | 3968篇 |
2002年 | 3115篇 |
2001年 | 1853篇 |
2000年 | 1703篇 |
1999年 | 1646篇 |
1998年 | 1438篇 |
1997年 | 1323篇 |
1996年 | 1438篇 |
1995年 | 1099篇 |
1994年 | 931篇 |
1993年 | 803篇 |
1992年 | 743篇 |
1991年 | 643篇 |
1990年 | 535篇 |
1989年 | 438篇 |
1988年 | 333篇 |
1987年 | 291篇 |
1986年 | 299篇 |
1985年 | 248篇 |
1984年 | 172篇 |
1983年 | 146篇 |
1982年 | 111篇 |
1981年 | 98篇 |
1980年 | 78篇 |
1979年 | 67篇 |
1978年 | 67篇 |
1977年 | 44篇 |
1975年 | 46篇 |
1914年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS 下载免费PDF全文
Wenli Cao Xinguo Wang Haojie Li Xuliang Shi Wencheng Fan Shaohua Zhao Minyan Liu Liying Niu 《Biomedical chromatography : BMC》2015,29(11):1769-1779
Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
92.
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
93.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
94.
Huang Huaijing Wu Zhaoqi Zhu Chuanxi Fei Shao-Ming 《International Journal of Theoretical Physics》2021,60(7):2368-2379
International Journal of Theoretical Physics - Quantifying the quantumness of ensembles is a vital and practical task in quantum information theory. In this paper, we quantify the quantumness of... 相似文献
95.
Guangrui Chen Yuxing Yan Dr. Jie Wang Prof. Yong Sik Ok Guiyuan Zhong Prof. Bu Yuan Guan Prof. Yusuke Yamauchi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19831-19836
Mesoporous core–shell nanostructures with controllable ultra-large open channels in their nanoshells are of great interest. However, soft template-directed cooperative assembly to mesoporous nanoshells with highly accessible pores larger than 30 nm, or even above 50 nm into macroporous range, remains a significant challenge. Herein we report a general approach for precisely tailored coating of hierarchically macro-/mesoporous polymer and carbon shells, possessing highly accessible radial channels with extremely wide pore size distribution from ca. 10 nm to ca. 200 nm, on diverse functional materials. This strategy creates opportunities to tailor the interfacial assembly of irregular mesostructured nanounits on core materials and generate various core–shell nanomaterials with controllable pore architectures. The obtained Fe,N-doped macro-/mesoporous carbon nanoshells show enhanced electrochemical performance for the oxygen reduction reaction in alkaline condition. 相似文献
96.
Jin Xie Yun-Wei Song Dr. Bo-Quan Li Dr. Hong-Jie Peng Prof. Jia-Qi Huang Prof. Qiang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22334-22339
Polysulfide intermediates (PSs), the liquid-phase species of active materials in lithium–sulfur (Li-S) batteries, connect the electrochemical reactions between insulative solid sulfur and lithium sulfide and are key to full exertion of the high-energy-density Li-S system. Herein, the concept of sulfur container additives is proposed for the direct modification on the PSs species. By reversible storage and release of the sulfur species, the container molecule converts small PSs into large organosulfur species. The prototype di(tri)sulfide-polyethylene glycol sulfur container is highly efficient in the reversible PS transformation to multiply affect electrochemical behaviors of sulfur cathodes in terms of liquid-species clustering, reaction kinetics, and solid deposition. The stability and capacity of Li-S cells was thereby enhanced. The sulfur container is a strategy to directly modify PSs, enlightening the precise regulation on Li-S batteries and multi-phase electrochemical systems. 相似文献
97.
98.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
99.
100.