全文获取类型
收费全文 | 174354篇 |
免费 | 29676篇 |
国内免费 | 19139篇 |
专业分类
化学 | 118550篇 |
晶体学 | 1869篇 |
力学 | 10942篇 |
综合类 | 1147篇 |
数学 | 22143篇 |
物理学 | 68518篇 |
出版年
2024年 | 575篇 |
2023年 | 3412篇 |
2022年 | 5920篇 |
2021年 | 6154篇 |
2020年 | 6949篇 |
2019年 | 6440篇 |
2018年 | 6059篇 |
2017年 | 5538篇 |
2016年 | 8346篇 |
2015年 | 8155篇 |
2014年 | 10009篇 |
2013年 | 13033篇 |
2012年 | 15539篇 |
2011年 | 15909篇 |
2010年 | 10943篇 |
2009年 | 10624篇 |
2008年 | 11275篇 |
2007年 | 10109篇 |
2006年 | 9437篇 |
2005年 | 7815篇 |
2004年 | 6080篇 |
2003年 | 4879篇 |
2002年 | 4485篇 |
2001年 | 3810篇 |
2000年 | 3352篇 |
1999年 | 3623篇 |
1998年 | 3092篇 |
1997年 | 2907篇 |
1996年 | 2944篇 |
1995年 | 2502篇 |
1994年 | 2264篇 |
1993年 | 1906篇 |
1992年 | 1678篇 |
1991年 | 1497篇 |
1990年 | 1233篇 |
1989年 | 948篇 |
1988年 | 705篇 |
1987年 | 623篇 |
1986年 | 615篇 |
1985年 | 491篇 |
1984年 | 318篇 |
1983年 | 260篇 |
1982年 | 216篇 |
1981年 | 132篇 |
1980年 | 90篇 |
1979年 | 39篇 |
1978年 | 23篇 |
1976年 | 25篇 |
1975年 | 22篇 |
1957年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
52.
Wenpin Wang Qing Yao Jianhui Song Binbin Yao Hui Wang Zhibo Li 《Journal of Polymer Science.Polymer Physics》2019,57(11):662-669
The PeakForce Quantitative Nanomechanical Mapping based on atomic force microscope (AFM) is employed to first visualize and then quantify the elastic properties of a model nitrile rubber/poly(vinyl chloride) (NBR/PVC) blend at the nanoscale. This method allows us to consistently observe the changes in mechanical properties of each phase in polymer blends. Beyond measuring and discriminating elastic modulus and adhesion forces of each phase, we tune the AFM tips and the peak force parameters in order to reliably image samples. In view of viscoelastic difference in each phase, a three‐phase coexistence of an unmixed NBR phase, the mixed phase, and PVC microcrystallites is directly visualized in NBR/PVC blends. The nanomechanical investigation is also capable of recognizing the crosslinked rubber phase in cured rubber. The contribution of the mixed phase was quantified and it was found that the mechanical properties of blends are mainly determined by the homogeneity and stiffness of the mixed phase. This study furthers our understanding the structure–mechanical property relationship of thermoplastic elastomers, which is important for their potential design and applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 662–669 相似文献
53.
Xinghua Li Yuqin Yang Junjie Miao Zhendong Yin Yijing Zhai Hongmei Shi Zengning Li 《Electrophoresis》2020,41(18-19):1584-1591
In the present research, field-amplified sample injection–CZE (FASI–CZE) coupled with a diode array detector was established to determine trace level sulfa antibiotic. Sulfathiazole, sulfadiazine, sulfamethazine, sulfadimethoxine, sulfamethoxazole, and sulfisoxazole were selected as analytes for the experiments. The background electrolyte solution consisted of 70.0 mmol/L borax and 60.0 mmol/L boric acid (including 10% methanol, pH 9.1). The plug was 2.5 mmol/L borax, which was injected into the capillary at a pressure of 0.5 psi for 5 s. Then the sample was injected into the capillary at an injection voltage of –10 kV for 20 s. The electrophoretic separation was carried out under a voltage of +19 kV. The capillary temperature was maintained at 20˚C throughout the analysis, and six sulfonamides were completely separated within 35 min. Compared with pressure injection-CZE, the sensitivity of FASI-CZE was increased by 6.25–10.0 times, and the LODs were reduced from 0.2–0.5 to 0.02–0.05 μg/mL. The method was applied to the determination of sulfonamides in river water and particulate matter samples. The recoveries were 78.59–106.59%. The intraday and interday precisions were 2.89–7.35% and 2.77–7.09%, respectively. This provides a simpler and faster method for the analysis of sulfa antibiotic residues in environmental samples. 相似文献
54.
55.
A Savitzky–Golay filtering for smoothing and peak search written in Python is presented in this paper alongside its applications in the list-mode digital data acquisition dual gamma–gamma coincidence bismuth germanate (BGO) detector. The study has demonstrated that the software provides a reliable and effective way to quantify trace amounts of 22Na and 7Be in aerosol samples collected at Resolute Bay, Canada with a critical limit of 3 mBq and 5 Bq respectively for a 20 h counting interval, which are believed to be the inherent limitations of the dual-BGO system.
相似文献56.
57.
Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ting Li Shuangfei Xiang Piming Ma Huiyu Bai Weifu Dong Mingqing Chen 《Journal of Polymer Science.Polymer Physics》2015,53(14):1020-1026
A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026 相似文献
58.
Analysis and pharmacokinetic study of polyphyllin H in beagle dog plasma after oral administration of Rhizoma Paridis Extracts by LC‐MS/MS
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)
59.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
60.