全文获取类型
收费全文 | 1354766篇 |
免费 | 33954篇 |
国内免费 | 12227篇 |
专业分类
化学 | 680463篇 |
晶体学 | 20844篇 |
力学 | 76242篇 |
综合类 | 421篇 |
数学 | 244066篇 |
物理学 | 378911篇 |
出版年
2021年 | 14544篇 |
2020年 | 16995篇 |
2019年 | 17251篇 |
2018年 | 14415篇 |
2017年 | 12705篇 |
2016年 | 29133篇 |
2015年 | 22054篇 |
2014年 | 31841篇 |
2013年 | 76258篇 |
2012年 | 39700篇 |
2011年 | 36666篇 |
2010年 | 39008篇 |
2009年 | 41432篇 |
2008年 | 35646篇 |
2007年 | 31172篇 |
2006年 | 36265篇 |
2005年 | 29559篇 |
2004年 | 30151篇 |
2003年 | 28427篇 |
2002年 | 29494篇 |
2001年 | 27471篇 |
2000年 | 24478篇 |
1999年 | 22679篇 |
1998年 | 21358篇 |
1997年 | 21194篇 |
1996年 | 21450篇 |
1995年 | 19465篇 |
1994年 | 18884篇 |
1993年 | 18392篇 |
1992年 | 18110篇 |
1991年 | 18408篇 |
1990年 | 17621篇 |
1989年 | 17579篇 |
1988年 | 17137篇 |
1987年 | 17138篇 |
1986年 | 16039篇 |
1985年 | 22449篇 |
1984年 | 23724篇 |
1983年 | 19926篇 |
1982年 | 21600篇 |
1981年 | 20832篇 |
1980年 | 20190篇 |
1979年 | 20294篇 |
1978年 | 21621篇 |
1977年 | 21209篇 |
1976年 | 20901篇 |
1975年 | 19635篇 |
1974年 | 19241篇 |
1973年 | 19772篇 |
1972年 | 14259篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using... 相似文献
3.
Inas A. Abdallah Sherin F. Hammad Alaa Bedair Mohamed A. Abdelaziz Neil D. Danielson Ahmed H. Elshafeey Fotouh R. Mansour 《Biomedical chromatography : BMC》2022,36(6):e5365
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma. 相似文献
4.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
5.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We... 相似文献
6.
Chuprin A. S. Belova S. A. Bugaenko M. G. Vologzhanina A. V. Loktev A. S. Voloshin Ya. Z. Buznik V. M. Dedov A. G. 《Kinetics and Catalysis》2022,63(1):108-116
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the... 相似文献
7.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed. 相似文献
8.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
9.
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The... 相似文献
10.
Lin Yu Wu Yeyu Tan Xuecai Wu Jiawen Huang Kejing Mi Yan Ou Panpan Wei Fucun 《Journal of Solid State Electrochemistry》2022,26(4):959-971
Journal of Solid State Electrochemistry - An ultrasensitive “signal-off–on” electrochemiluminescence (ECL) biosensor is constructed based on f1-TiO2/g-C3N4/PDA for thrombin... 相似文献