全文获取类型
收费全文 | 12433篇 |
免费 | 2198篇 |
国内免费 | 1551篇 |
专业分类
化学 | 9014篇 |
晶体学 | 97篇 |
力学 | 815篇 |
综合类 | 95篇 |
数学 | 1311篇 |
物理学 | 4850篇 |
出版年
2024年 | 49篇 |
2023年 | 316篇 |
2022年 | 461篇 |
2021年 | 525篇 |
2020年 | 566篇 |
2019年 | 522篇 |
2018年 | 416篇 |
2017年 | 353篇 |
2016年 | 622篇 |
2015年 | 587篇 |
2014年 | 668篇 |
2013年 | 943篇 |
2012年 | 1121篇 |
2011年 | 1092篇 |
2010年 | 749篇 |
2009年 | 747篇 |
2008年 | 838篇 |
2007年 | 744篇 |
2006年 | 643篇 |
2005年 | 559篇 |
2004年 | 434篇 |
2003年 | 383篇 |
2002年 | 318篇 |
2001年 | 262篇 |
2000年 | 261篇 |
1999年 | 280篇 |
1998年 | 235篇 |
1997年 | 209篇 |
1996年 | 221篇 |
1995年 | 189篇 |
1994年 | 151篇 |
1993年 | 136篇 |
1992年 | 103篇 |
1991年 | 84篇 |
1990年 | 95篇 |
1989年 | 69篇 |
1988年 | 53篇 |
1987年 | 47篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
X. Y. Li G. J. Wang J. G. Sun Y. T. Zheng B. Yan H. T. Xie X. Wang 《Chromatographia》2007,65(1-2):13-18
To support preclinical pharmacokinetic investigation of 1-[4-[2-(4-bromobenzene-sulfonaminoethyl)phenylsufonyl]-3-(trans-4-methylcyclohexyl)urea
(G004), a rapid, sensitive and specific high-performance liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS)
method was developed and validated. Glibenclamide was employed as internal standard. After liquid–liquid extraction the analyte
was analyzed on a Kromasil C18 column (150 × 2.0 mm i.d.) with a mobile phase consisted of acetonitrile–water (0.05% acetic acid), 30:70 (v/v). The flow
rate was 0.2 mL min−1. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion
monitoring (SIM) mode. The retention time was about 3.5 and 4.2 min for Glibenclamide and G004, respectively. The assay was
linear over the concentration range of 2.0–500.0 ng mL−1. Extraction Recovery of G004 in rat plasma was more than 87%. The intra- and inter-assay precision was lower than 11.5% (CV).
This validated method was successfully applied to the pharmacokinetics of G004 in rats. 相似文献
102.
103.
104.
105.
Estimation of an important constant in sieve method 总被引:1,自引:0,他引:1
Xie Sheng-gang 《数学学报(英文版)》1994,10(1):1-3
ζ
k
is one of the most important constant in the sieve methods. This paper gives the relatively accurate lower bound and upper
bound on it, that is,
, wherec=1.22... andk>16. 相似文献
106.
107.
108.
109.
Xie Z Sielemann S Schmidt H Li F Baumbach JI 《Analytical and bioanalytical chemistry》2002,372(5-6):606-610
A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1). 相似文献
110.
Application of mono (6A-N-ethylenediamine-6A-deoxy) perphenylcarbamoylated β-cyclodextrin (β-CD) bonded stationary phase (CSP) in micro-high performance liquid chromatography (micro-HPLC) and pressurized capillary electrochromatography (p-CEC) was firstly presented. A series of racemic α-amidophosphonates were resolved in reversed- and normal-phase modes on this CSP. The investigated chromatographic parameters include retention factor (k′), separation factor (α) and resolution (Rs) of solutes. In addition, the structural variation of the solutes and the experimental factors affecting chiral separations have been examined, including the percentage of alcohol modifier, the linear velocity (u) of the mobile phase, electrical field strength, etc. Baseline separation was achieved for most of the entities. Hydrophobic interaction, steric effect and π-π interaction contribute to the possible mechanism. Comparative results indicate that higher Rs value up to 3.1 was found in micro-HPLC, higher efficiency up to 29,970 in p-CEC. 相似文献