全文获取类型
收费全文 | 344785篇 |
免费 | 3776篇 |
国内免费 | 1074篇 |
专业分类
化学 | 186492篇 |
晶体学 | 5950篇 |
力学 | 14327篇 |
综合类 | 7篇 |
数学 | 36902篇 |
物理学 | 105957篇 |
出版年
2018年 | 3107篇 |
2017年 | 3139篇 |
2016年 | 5193篇 |
2015年 | 3429篇 |
2014年 | 5264篇 |
2013年 | 14796篇 |
2012年 | 10312篇 |
2011年 | 12664篇 |
2010年 | 8912篇 |
2009年 | 8838篇 |
2008年 | 11737篇 |
2007年 | 11762篇 |
2006年 | 11179篇 |
2005年 | 10170篇 |
2004年 | 9397篇 |
2003年 | 8433篇 |
2002年 | 8227篇 |
2001年 | 10130篇 |
2000年 | 7680篇 |
1999年 | 6055篇 |
1998年 | 4875篇 |
1997年 | 4820篇 |
1996年 | 4634篇 |
1995年 | 4313篇 |
1994年 | 4213篇 |
1993年 | 4054篇 |
1992年 | 4757篇 |
1991年 | 4568篇 |
1990年 | 4506篇 |
1989年 | 4484篇 |
1988年 | 4416篇 |
1987年 | 4448篇 |
1986年 | 4142篇 |
1985年 | 5578篇 |
1984年 | 5638篇 |
1983年 | 4791篇 |
1982年 | 5042篇 |
1981年 | 4843篇 |
1980年 | 4751篇 |
1979年 | 5020篇 |
1978年 | 5271篇 |
1977年 | 5085篇 |
1976年 | 5019篇 |
1975年 | 4830篇 |
1974年 | 4780篇 |
1973年 | 4963篇 |
1972年 | 3244篇 |
1971年 | 2702篇 |
1968年 | 3040篇 |
1967年 | 3179篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
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
2.
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
3.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of... 相似文献
4.
Hassan E. A. M. Elabid A. E. A. Bashier E. O. Elagib T. H. H. 《Mechanics of Composite Materials》2022,58(2):261-270
Mechanics of Composite Materials - Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial... 相似文献
5.
Petrov P. A. Filippova E. A. Kompankov N. B. Sukhikh T. S. Sokolov M. N. 《Journal of Structural Chemistry》2022,63(3):470-475
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the... 相似文献
6.
Chetan Bhadaliya Bala Krishna Panigrahy Dipanjan Goswami Sovan Maiti Sanjay Jagannath Gurule Arshad H. Khuroo 《Biomedical chromatography : BMC》2022,36(4):e5337
A selective, highly sensitive, precise, and novel bioanalytical method has been developed and validated to quantify sinococuline, an active constituent present in the phytopharmaceutical drug product containing Cocculus hirsutus plant extract, in vivo. Chromatographic separation was achieved on a Luna Omega Polar-C18 bonded analytical column maintained at 45°C. The isocratic mobile phase consisted of methanol and ammonium formate buffer (60:40, v/v) at acidic pH with a low flow rate of 0.250 mL/min. Detection was performed on an API 4000 mass spectrometer using electrospray ionization in positive polarity and multiple reaction monitoring mode to achieve a lower limit of quantification of 1.50 ng/mL. Excellent accuracy and precision were obtained after extracting the analyte from plasma samples using a chemical analogue as an internal standard in the absence of an isotope-labeled compound. The extraction efficacy was evidenced from recovery study, and the analyte was found to be stable in plasma. Validation study demonstrated linearity with coefficient of correlation, r ≥ 0.99, and minimal matrix effect. This bioanalytical method was successfully applied to evaluate pharmacokinetic parameters of sinococuline from a phase I clinical trial of an aqueous extract of C. hirsutus in healthy human volunteers. 相似文献
7.
8.
Aequationes mathematicae - In this paper, we establish a new class of dynamic inequalities of Hardy’s type which generalize and improve some recent results given in the literature. More... 相似文献
9.
Tsyganova S. I. Fetisova O. Yu. Mazurova E. N. Taran O. P. Kuznetsov B. N. 《Russian Journal of Applied Chemistry》2022,95(3):408-416
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed.... 相似文献
10.
Roopa K. P. Keshavamurthy K. Mahesh B. Veena K. P. Shankara B. S. Basavaiah K. 《Journal of Applied Spectroscopy》2022,89(4):809-818
Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The... 相似文献