全文获取类型
收费全文 | 260131篇 |
免费 | 6038篇 |
国内免费 | 3142篇 |
专业分类
化学 | 142859篇 |
晶体学 | 3583篇 |
力学 | 10972篇 |
综合类 | 120篇 |
数学 | 29734篇 |
物理学 | 82043篇 |
出版年
2021年 | 2157篇 |
2020年 | 2599篇 |
2019年 | 2788篇 |
2018年 | 3132篇 |
2017年 | 3018篇 |
2016年 | 4757篇 |
2015年 | 3468篇 |
2014年 | 4927篇 |
2013年 | 12554篇 |
2012年 | 9695篇 |
2011年 | 11705篇 |
2010年 | 7767篇 |
2009年 | 7541篇 |
2008年 | 10187篇 |
2007年 | 10202篇 |
2006年 | 9314篇 |
2005年 | 8684篇 |
2004年 | 7660篇 |
2003年 | 6798篇 |
2002年 | 6782篇 |
2001年 | 7718篇 |
2000年 | 5783篇 |
1999年 | 4635篇 |
1998年 | 3880篇 |
1997年 | 3881篇 |
1996年 | 3611篇 |
1995年 | 3412篇 |
1994年 | 3175篇 |
1993年 | 3159篇 |
1992年 | 3455篇 |
1991年 | 3478篇 |
1990年 | 3261篇 |
1989年 | 3190篇 |
1988年 | 3211篇 |
1987年 | 3083篇 |
1986年 | 2993篇 |
1985年 | 4030篇 |
1984年 | 4177篇 |
1983年 | 3423篇 |
1982年 | 3718篇 |
1981年 | 3595篇 |
1980年 | 3471篇 |
1979年 | 3511篇 |
1978年 | 3736篇 |
1977年 | 3573篇 |
1976年 | 3784篇 |
1975年 | 3359篇 |
1974年 | 3483篇 |
1973年 | 3788篇 |
1972年 | 2300篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
81.
82.
Jigneshkumar P. Patel Zou Guo Xiang Shaw Ling Hsu Andrew B. Schoch Sena Ada Carleen Dean Matsumoto 《Journal of Polymer Science.Polymer Physics》2015,53(21):1519-1526
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1519–1526 相似文献
83.
84.
85.
Brian R. Holder Colleen A. McNaney David Luchetti Eric Schaeffer Dieter M. Drexler 《Biomedical chromatography : BMC》2015,29(9):1375-1379
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
86.
87.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Victor A. Kusuma Elliot A. Roth William P. Clafshenkel Steven S. Klara Xu Zhou Surendar R. Venna Erik Albenze David R. Luebke Meagan S. Mauter Richard R. Koepsel Alan J. Russell David Hopkinson Hunaid B. Nulwala 《Journal of polymer science. Part A, Polymer chemistry》2015,53(13):1548-1557
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557 相似文献
88.
Valiullina Z. R. Galeeva A. M. Miftakhov M. S. 《Russian Journal of Organic Chemistry》2021,57(9):1461-1465
Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave... 相似文献
89.
90.
Afzal Asif Mohammed Samee A. D. Abdul Razak R. K. Ramis M. K. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1271-1285
Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway... 相似文献