全文获取类型
收费全文 | 280513篇 |
免费 | 4121篇 |
国内免费 | 1125篇 |
专业分类
化学 | 154700篇 |
晶体学 | 3335篇 |
力学 | 10737篇 |
综合类 | 4篇 |
数学 | 34919篇 |
物理学 | 82064篇 |
出版年
2021年 | 2019篇 |
2020年 | 2430篇 |
2019年 | 2728篇 |
2018年 | 3049篇 |
2017年 | 2956篇 |
2016年 | 5022篇 |
2015年 | 3649篇 |
2014年 | 5160篇 |
2013年 | 13384篇 |
2012年 | 10505篇 |
2011年 | 12724篇 |
2010年 | 8185篇 |
2009年 | 7888篇 |
2008年 | 11341篇 |
2007年 | 11302篇 |
2006年 | 10429篇 |
2005年 | 9694篇 |
2004年 | 8625篇 |
2003年 | 7574篇 |
2002年 | 7499篇 |
2001年 | 7768篇 |
2000年 | 5949篇 |
1999年 | 4725篇 |
1998年 | 4025篇 |
1997年 | 3984篇 |
1996年 | 3427篇 |
1995年 | 3411篇 |
1994年 | 3277篇 |
1993年 | 3288篇 |
1992年 | 3598篇 |
1991年 | 3568篇 |
1990年 | 3375篇 |
1989年 | 3289篇 |
1988年 | 3350篇 |
1987年 | 3225篇 |
1986年 | 3074篇 |
1985年 | 4356篇 |
1984年 | 4497篇 |
1983年 | 3654篇 |
1982年 | 4090篇 |
1981年 | 3927篇 |
1980年 | 3810篇 |
1979年 | 3840篇 |
1978年 | 4037篇 |
1977年 | 3865篇 |
1976年 | 4073篇 |
1975年 | 3623篇 |
1974年 | 3731篇 |
1973年 | 3980篇 |
1972年 | 2440篇 |
排序方式: 共有10000条查询结果,搜索用时 715 毫秒
91.
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
92.
93.
94.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry 下载免费PDF全文
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
95.
Tanja Vidaković-Koch Tamara Miličić Luka A. Živković Hoon Seng Chan Ulrike Krewer Menka Petkovska 《Current Opinion in Electrochemistry》2021
The nonlinear frequency response analysis (NFRA) can be seen as an extension of electrochemical impedance spectroscopy. NFRA gives a full and detailed representation of the system response and can establish a connection between model parameters and the experimentally observed phenomena. In this article, different theoretical NFRA approaches and the most recent application examples are discussed. A simple electrochemical example is used to showcase the benefits and disadvantages of analyzing the system response by using different approaches. In addition, it was shown how to extract experimental harmonic values and analyze them. 相似文献
96.
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
97.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
98.
99.
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
100.