全文获取类型
收费全文 | 2515篇 |
免费 | 80篇 |
国内免费 | 9篇 |
专业分类
化学 | 1653篇 |
晶体学 | 26篇 |
力学 | 58篇 |
数学 | 307篇 |
物理学 | 560篇 |
出版年
2023年 | 16篇 |
2022年 | 38篇 |
2021年 | 81篇 |
2020年 | 55篇 |
2019年 | 56篇 |
2018年 | 53篇 |
2017年 | 41篇 |
2016年 | 77篇 |
2015年 | 87篇 |
2014年 | 82篇 |
2013年 | 153篇 |
2012年 | 162篇 |
2011年 | 175篇 |
2010年 | 111篇 |
2009年 | 108篇 |
2008年 | 154篇 |
2007年 | 122篇 |
2006年 | 108篇 |
2005年 | 105篇 |
2004年 | 88篇 |
2003年 | 55篇 |
2002年 | 72篇 |
2001年 | 44篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 35篇 |
1997年 | 34篇 |
1996年 | 29篇 |
1995年 | 31篇 |
1994年 | 32篇 |
1993年 | 27篇 |
1992年 | 32篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 23篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有2604条查询结果,搜索用时 15 毫秒
101.
A. M. Amorim Da Costa H. D. Burrows C. F. G. C. Geraldes J. J. C. Teixeira-dias C. G. Bazuin D. Guillon 《Liquid crystals》2013,40(3):215-226
Abstract Structures of the thermotropic mesophases of lead(II) decanoate are reassigned following optical and X-ray diffraction studies. These results, and those of D.S.C., Raman and 207Pb N.M.R. spectroscopy, indicate formation of a lower temperature mesophase involving mainly increased lateral disorder, and a higher temperature Lα (smectic A) phase resulting from chain disordering and decreased lead-carboxylate interaction. Comparison of experimental thermodynamic data for the phase transitions with theoretical data in the literature indicates that the entropy change for the lower to higher mesophase transition is dominated by the increase in chain disorder. 相似文献
102.
de Oliveira Elcio Cruz de Santana Maia Lúcio Abdala da Costa Lívio Garcia Lourenço Túlio Campos 《Accreditation and quality assurance》2018,23(6):365-369
Accreditation and Quality Assurance - In any commercial transaction, the presence of tolerances from specification limits is essential to ensure that the true value of the property of interest is... 相似文献
103.
Maria N. Tamaño‐Machiavello Benjamin Bracke Carlos M. Costa Senentxu Lanceros‐Mendez Roser Sabater i Serra José Luis Gómez Ribelles 《Journal of Polymer Science.Polymer Physics》2016,54(6):672-679
Polymer blend membranes have been obtained consisting of a hydrophilic and a hydrophobic polymers distributed in co‐continuous phases. In order to obtain stable membranes in aqueous environments, the hydrophilic phase is formed by a poly(hydrohyethyl acrylate), PHEA, network while the hydrophobic phase is formed by poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE). To obtain the composites, in a first stage, P(VDF‐TrFE) is blended with poly(ethylene oxyde) (PEO), the latter used as sacrificial porogen. P(VDF‐TrFE)/PEO blend membranes were prepared by solvent casting at 70°C followed by cooling to room temperature. Then PEO is removed from the membrane by immersion in water obtaining a P(VDF‐TrFE) porous membrane. After removing of the PEO polymer, a P(VDF‐TrFE) membrane results in which pores are collapsed. Nevertheless the pores reopen when a mixture of hydroxethyl acrylate (HEA) monomer, ethyleneglycol dimethacrylate (as crosslinker) and ethanol (as diluent) is absorbed in the membrane and subsequent polymerization yields hybrid hydrophilic/hydrophobic membranes with controlled porosity. The membranes are thus suitable for lithium‐ion battery separator membranes and/or biostable supports for cell culture in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 672–679 相似文献
104.
105.
Rafael Dias do Espírito Santo Rosineide Costa Simas Alviclér Magalhães Vanessa Gonçalves dos Santos Thais Regiani Ana Cristina Isler Natiza Graziele Martins Marcos Nogueira Eberlin Eduardo René Pérez González 《Journal of Physical Organic Chemistry》2013,26(4):315-321
Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI‐MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (1H‐13C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple‐Bond Correlation (HMBC), 1H‐15N HMBC, 1H‐1H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p‐Cl and p‐Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p‐NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
106.
Marie-Claire Giel Dr. Christopher J. Smedley Emily R. R. Mackie Taijie Guo Prof. Dr. Jiajia Dong Dr. Tatiana P. Soares da Costa Prof. Dr. John E. Moses 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1197-1202
The boom in growth of 1,4-disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the CuI-catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1-substituted-1,2,3-triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click-inspired protocol for the synthesis of 1-substituted-1,2,3-triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal-free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1-substituted-1,2,3-triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1-substituted triazolium sulfonyl fluoride salts. 相似文献
107.
Determination of fexofenadine in Hank's balanced salt solution by high‐performance liquid chromatography with ultraviolet detection: application to Caco‐2 cell permeability studies
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)
Marco Antônio dos. Reis Júnior Ana Cláudia Miranda de Faria Eudes da. Silva Velozo Teresa Dalla Costa Frank Pereira de Andrade Whocely Victor de Castro 《Biomedical chromatography : BMC》2015,29(4):537-544
The drug‐transporting proteins can affect the pharmacokinetics and pharmacodymanics of many drugs, resulting in an erratic and unpredictable pharmacological response. The Caco‐2 monolayer is routinely applied to investigate the carrier‐mediated transport of drugs. Therefore, the selection of a marker compound able to characterize the activity of such transporters is crucial. Fexofenadine (FEX), a P‐gp/OATP substrate, can be considered a suitable probe. However, in order to use be used as a marker compound, it is mandatory to develop an analytical method able to quantify this drug during the in vitro permeability assay. An HPLC method with ultraviolet detection was developed; the mobile phase consisted of phosphate buffer (pH 3.2) containing 10 m m of sodium octanosulphonate and acetonitrile (60:40) and the flow rate was set at 1.2 mL/min. Fexofenadine was eluted at 40°C, the retention time was about 4.6 min. The LOD and LOQ values were 1.9 and 6.2 ng/mL, respectively. Verapamil and ketoconazole, the most common P‐gp inhibitors, were eluted as distinct peaks of that corresponding to fexofenadine The method was successfully applied to quantify the amount of FEX transported across the Caco‐2 monolayer and could be an additional tool for those investigating the role of membrane transporters on drug absorption. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
108.
109.
110.