全文获取类型
收费全文 | 201586篇 |
免费 | 2685篇 |
国内免费 | 746篇 |
专业分类
化学 | 109185篇 |
晶体学 | 3245篇 |
力学 | 7903篇 |
综合类 | 3篇 |
数学 | 24741篇 |
物理学 | 59940篇 |
出版年
2021年 | 1605篇 |
2020年 | 1881篇 |
2019年 | 2003篇 |
2018年 | 2326篇 |
2017年 | 2426篇 |
2016年 | 3963篇 |
2015年 | 2575篇 |
2014年 | 3859篇 |
2013年 | 9292篇 |
2012年 | 7493篇 |
2011年 | 9075篇 |
2010年 | 6093篇 |
2009年 | 5937篇 |
2008年 | 8406篇 |
2007年 | 8303篇 |
2006年 | 7935篇 |
2005年 | 7210篇 |
2004年 | 6547篇 |
2003年 | 5859篇 |
2002年 | 5627篇 |
2001年 | 5590篇 |
2000年 | 4232篇 |
1999年 | 3306篇 |
1998年 | 2794篇 |
1997年 | 2720篇 |
1996年 | 2685篇 |
1995年 | 2439篇 |
1994年 | 2369篇 |
1993年 | 2252篇 |
1992年 | 2558篇 |
1991年 | 2468篇 |
1990年 | 2377篇 |
1989年 | 2313篇 |
1988年 | 2326篇 |
1987年 | 2303篇 |
1986年 | 2192篇 |
1985年 | 2942篇 |
1984年 | 2996篇 |
1983年 | 2605篇 |
1982年 | 2783篇 |
1981年 | 2603篇 |
1980年 | 2566篇 |
1979年 | 2688篇 |
1978年 | 2697篇 |
1977年 | 2597篇 |
1976年 | 2626篇 |
1975年 | 2550篇 |
1974年 | 2531篇 |
1973年 | 2693篇 |
1972年 | 1703篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
21.
22.
E. V. Shadrina O. N. Malinkina T. G. Khonina A. B. Shipovskaya V. I. Fomina E. Yu. Larchenko N. A. Popova I. G. Zyryanova L. P. Larionov 《Russian Chemical Bulletin》2015,64(7):1633-1639
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications. 相似文献
23.
24.
25.
26.
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
27.
S. V. Panin I. V. Vlasov V. P. Sergeev B. B. Ovechkin P. O. Marushchak Sunder Ramasubbu P. S. Lyubutin V. V. Titkov 《Physical Mesomechanics》2015,18(3):261-272
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method. 相似文献
28.
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
29.
30.