全文获取类型
收费全文 | 22258篇 |
免费 | 1009篇 |
国内免费 | 1287篇 |
专业分类
化学 | 12735篇 |
晶体学 | 229篇 |
力学 | 1665篇 |
综合类 | 181篇 |
数学 | 3243篇 |
物理学 | 6501篇 |
出版年
2021年 | 316篇 |
2020年 | 371篇 |
2019年 | 440篇 |
2018年 | 494篇 |
2017年 | 535篇 |
2016年 | 614篇 |
2015年 | 416篇 |
2014年 | 634篇 |
2013年 | 908篇 |
2012年 | 837篇 |
2011年 | 873篇 |
2010年 | 888篇 |
2009年 | 875篇 |
2008年 | 883篇 |
2007年 | 870篇 |
2006年 | 712篇 |
2005年 | 634篇 |
2004年 | 557篇 |
2003年 | 539篇 |
2002年 | 604篇 |
2001年 | 603篇 |
2000年 | 442篇 |
1999年 | 328篇 |
1998年 | 274篇 |
1997年 | 255篇 |
1996年 | 251篇 |
1993年 | 252篇 |
1992年 | 260篇 |
1991年 | 263篇 |
1990年 | 281篇 |
1989年 | 271篇 |
1987年 | 247篇 |
1985年 | 282篇 |
1984年 | 286篇 |
1983年 | 263篇 |
1982年 | 276篇 |
1980年 | 257篇 |
1979年 | 303篇 |
1978年 | 329篇 |
1977年 | 320篇 |
1976年 | 404篇 |
1975年 | 359篇 |
1974年 | 388篇 |
1973年 | 397篇 |
1972年 | 369篇 |
1971年 | 332篇 |
1970年 | 314篇 |
1969年 | 298篇 |
1968年 | 253篇 |
1967年 | 250篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
Theoretical and Experimental Chemistry - The latest research on photocatalytic systems based on graphite-like carbon nitride (g-C3N4) for decontamination of air pollutants, in particular, volatile... 相似文献
963.
Yu. A. Titov A. M. Sych A. N. Sokolov V. Ya. Markiv N. M. Belyavina A. A. Kapshuk 《高压研究》2013,33(3-4):175-181
Abstract The crystal structure of the metastable LaNbO4 high-pressure modification (HPM) has been studied by X-ray powder diffraction. It was found that the crystal structure of HPM LaNbO4 belongs to- the room temperature BaMCF4 -type structure (space group Cmc21, a = 3,941(1)Å, b= 14,460(4) Å, c = 5,681(2) Å, Z = 4). 相似文献
964.
965.
Simultaneous determination of calycosin‐7‐O‐β‐d‐glucoside,calycosin, formononetin,astragaloside IV and schisandrin in rat plasma by LC‐MS/MS: application to a pharmacokinetic study after oral administration of Shenqi Wuwei chewable tablets
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xuehui Sun Pingping Zhang Xiujun Wu Qiong Wu Mengmeng Zhang Ye An Guobing Shi 《Biomedical chromatography : BMC》2014,28(8):1118-1125
A rapid, sensitive and reliable high‐performance liquid chromatography–mass spectrometry (LC‐MS/MS) method was developed and validated for simultaneous quantification of the five main bioactive components, calycosin, calycosin‐7‐O‐β‐d ‐glucoside, formononetin, astragaloside IV and schisandrin in rat plasma after oral administration of Shenqi Wuwei chewable tablets. Plasma samples were extracted using solid‐phase extraction separated on a CEC18 column and detected by MS with an electrospray ionization interface in multiple‐reaction monitoring mode. Calibration curves offered linear ranges of two orders of magnitude with r > 0.995. The method had a lower limit of quantitation of 0.1, 0.02, 0.1, 1 and 0.1 ng/mL for calycosin, calycosin‐7‐O‐β‐d ‐glucoside, formononetin, astragaloside IV and schisandrin, respectively. Intra‐ and inter‐day precisions (relative standard deviation) for all analytes ranged from 0.97 to 7.63% and from 3.45 to 10.89%, respectively. This method was successfully applied to the pharmacokinetic study of the five compounds in rats after oral administration of Shenqi Wuwei chewable tablets. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
966.
Dr. Konstantin I. Galkin Bogdan Ya. Karlinskii Dr. Alexander Yu. Kostyukovich Dr. Evgeniy G. Gordeev Prof. Dr. Valentine P. Ananikov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(39):8567-8571
This work reveals ambident nucleophilic reactivity of imidazolium cations towards carbonyl compounds at the C2 or C4 carbene centers depending on the steric properties of the substrates and reaction conditions. Such an adaptive behavior indicates the dynamic nature of organocatalysis proceeding via a covalent interaction of imidazolium carbenes with carbonyl substrates and can be explained by generation of the H-bonded ditopic carbanionic carbenes. 相似文献
967.
968.
969.
The Bayesian model are established for the VaR and related risk measurements. The relationship between VaR and other risk measurements including expect shortfall, tail condition expectation and conditional value at risk are discussed. Furthermore, the Bayesian estimates and Bayesian predictors of these risk measurement are derived. Thirdly, the consistency and asymptotic normality in the exponential risk model are proved. Finally, the numerical simulation method is used to verify the convergence rate under different sample sizes. 相似文献
970.
Meng-Meng Zhao Lin Zhou Ping-Ping Shi Xuan Zheng Xiao-Gang Chen Ji-Xing Gao Lei He Prof. Dr. Qiong Ye Prof. Dr. Cai-Ming Liu Prof. Dr. Da-Wei Fu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(25):6447-6454
Organic–inorganic hybrid perovskite-type multiferroics have attracted considerable research interest owing to their fundamental scientific significance and promising technological applications in sensors and multiple-state memories. The recent achievements with divalent metal dicyanamide compounds revealed such malleable frameworks as a unique platform for developing novel functional materials. Herein, two 3D organic–inorganic hybrid perovskites [Et3P(CH2)2F][Mn(dca)3] ( 1 ) and [Et3P(CH2)2Cl][Mn(dca)3] ( 2 ) (dca=dicyanamide, N(CN)2−) are presented. Accompanying the sequential phase transitions, they display a broad range of intriguing physical properties, including above room temperature ferroelastic behavior, switchable dielectricity, and low-temperature antiferromagnetic ordering (Tc=2.4 K for both 1 and 2 ). It is also worth noting that the spontaneous strain value of 1 is far beyond that of 2 in the first ferroelastic phase, as a result of the precise halogen substitution. From the point view of molecular design, this work should inspire further exploration of multifunctional molecular materials with desirable properties. 相似文献