全文获取类型
收费全文 | 634870篇 |
免费 | 5229篇 |
国内免费 | 1660篇 |
专业分类
化学 | 296675篇 |
晶体学 | 7256篇 |
力学 | 35639篇 |
综合类 | 17篇 |
数学 | 110569篇 |
物理学 | 191603篇 |
出版年
2021年 | 4787篇 |
2020年 | 5542篇 |
2019年 | 6284篇 |
2018年 | 20965篇 |
2017年 | 21082篇 |
2016年 | 18557篇 |
2015年 | 7274篇 |
2014年 | 10854篇 |
2013年 | 23934篇 |
2012年 | 23657篇 |
2011年 | 36676篇 |
2010年 | 24670篇 |
2009年 | 25014篇 |
2008年 | 31546篇 |
2007年 | 35080篇 |
2006年 | 19056篇 |
2005年 | 21092篇 |
2004年 | 18438篇 |
2003年 | 17477篇 |
2002年 | 14559篇 |
2001年 | 14556篇 |
2000年 | 11248篇 |
1999年 | 8321篇 |
1998年 | 7240篇 |
1997年 | 7146篇 |
1996年 | 6716篇 |
1995年 | 6299篇 |
1994年 | 6287篇 |
1993年 | 6033篇 |
1992年 | 6348篇 |
1991年 | 6883篇 |
1990年 | 6557篇 |
1989年 | 6466篇 |
1988年 | 6331篇 |
1987年 | 6155篇 |
1986年 | 5878篇 |
1985年 | 7452篇 |
1984年 | 7830篇 |
1983年 | 6577篇 |
1982年 | 6878篇 |
1981年 | 6368篇 |
1980年 | 6044篇 |
1979年 | 6584篇 |
1978年 | 6817篇 |
1977年 | 6664篇 |
1976年 | 6628篇 |
1975年 | 6329篇 |
1974年 | 6132篇 |
1973年 | 6492篇 |
1972年 | 4726篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
101.
102.
Eid Eldesouki I. Khalaf-Allah Reda A. Albadry Asmaa I. Easa Ammar S. 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7523-7538
Journal of Thermal Analysis and Calorimetry - The Stirling cycle is regarded as one alternative to the compressive cooling cycle. The current study examines the performance of a beta Stirling... 相似文献
103.
Russian Journal of Applied Chemistry - In September 1975, the head of Russian electrochemists, Academician A.N. Frumkin (1895–1976), in his report at the XI Mendeleev Congress on General and... 相似文献
104.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
105.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,... 相似文献
106.
Susan C. Scott Nicole M. Anders Ping He Avelina Hemingway Steven D. Gore Christine L. Hann Michelle A. Rudek 《Biomedical chromatography : BMC》2022,36(3):e5289
The Bcl-2 family small molecule inhibitor navitoclax is being clinically evaluated to treat multiple cancers including lymphoid malignancies and small cell lung cancer. A sensitive and reliable method was developed to quantitate navitoclax in human plasma using liquid chromatography with tandem mass spectrometry with which to perform detailed pharmacokinetic studies. Sample preparation involved protein precipitation using acetonitrile. Separation of navitoclax and the internal standard, navitoclax-d8, was achieved with a Waters Acquity UPLC BEH C18 column using isocratic flow over a 3 min total analytical run time. A SCIEX 4500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of navitoclax. The assay range was 5–5,000 ng/ml and proved to be accurate (89.5–104.9%) and precise (CV ≤ 11%). Long-term frozen plasma stability for navitoclax at −70°C was at least 43 months. The method was applied for the measurement of total plasma concentration of navitoclax in a patient receiving a 250 mg daily oral dose. 相似文献
107.
Sakhautdinova G. F. Sakhautdinov I. M. Mustafin A. G. Yunusov M. S. 《Chemistry of Natural Compounds》2022,58(1):185-186
Chemistry of Natural Compounds - 相似文献
108.
Rastsvetaeva R. K. Chukanov N. V. Pekov I. V. Varlamov D. A. Kazheva O. N. 《Crystallography Reports》2022,67(2):166-171
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been... 相似文献
109.
Herraiz A. Gutierrez M. Ortega-Mier M. 《Central European Journal of Operations Research》2022,30(4):1427-1450
Central European Journal of Operations Research - We define a geometric transformation of Euclidean Travelling Salesman Problem (TSP) tours that leads to a new formulation of the TSP. For every... 相似文献
110.
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