全文获取类型
收费全文 | 17595篇 |
免费 | 594篇 |
国内免费 | 104篇 |
专业分类
化学 | 11273篇 |
晶体学 | 80篇 |
力学 | 385篇 |
综合类 | 2篇 |
数学 | 3646篇 |
物理学 | 2907篇 |
出版年
2023年 | 113篇 |
2022年 | 212篇 |
2021年 | 397篇 |
2020年 | 349篇 |
2019年 | 318篇 |
2018年 | 692篇 |
2017年 | 475篇 |
2016年 | 581篇 |
2015年 | 468篇 |
2014年 | 496篇 |
2013年 | 1001篇 |
2012年 | 1035篇 |
2011年 | 1100篇 |
2010年 | 732篇 |
2009年 | 694篇 |
2008年 | 986篇 |
2007年 | 980篇 |
2006年 | 890篇 |
2005年 | 842篇 |
2004年 | 648篇 |
2003年 | 600篇 |
2002年 | 513篇 |
2001年 | 300篇 |
2000年 | 341篇 |
1999年 | 214篇 |
1998年 | 170篇 |
1997年 | 178篇 |
1996年 | 197篇 |
1995年 | 145篇 |
1994年 | 149篇 |
1993年 | 136篇 |
1992年 | 130篇 |
1991年 | 119篇 |
1990年 | 125篇 |
1989年 | 109篇 |
1988年 | 84篇 |
1987年 | 86篇 |
1986年 | 85篇 |
1985年 | 102篇 |
1984年 | 125篇 |
1983年 | 95篇 |
1982年 | 105篇 |
1981年 | 101篇 |
1980年 | 86篇 |
1979年 | 57篇 |
1978年 | 80篇 |
1977年 | 66篇 |
1976年 | 72篇 |
1975年 | 55篇 |
1973年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
Peralta Cecilia Mariana Acosta Gimena Henestrosa Cecilia Gil Raúl Andrés Fernández Liliana Patricia 《Journal of Analytical Chemistry》2022,77(3):308-317
Journal of Analytical Chemistry - The present development involved a flow injection strategy using a mini-column of multiwalled carbon nanotubes and fluorescent detection (λex of 283 nm,... 相似文献
2.
Ana-Maria Udrea Andra Dinache Jean-Marie Pags Ruxandra Angela Pirvulescu 《Molecules (Basel, Switzerland)》2021,26(8)
Multidrug resistance of bacteria is a worrying concern in the therapeutic field and an alternative method to combat it is designing new efflux pump inhibitors (EPIs). This article presents a molecular study of two quinazoline derivatives, labelled BG1189 and BG1190, proposed as EPIs. In silico approach investigates the pharmacodynamic and pharmacokinetic profile of BG1189 and BG1190 quinazolines. Molecular docking and predicted ADMET features suggest that BG1189 and BG1190 may represent attractive candidates as antimicrobial drugs. UV-Vis absorption spectroscopy was employed to study the time stability of quinazoline solutions in water or in dimethyl sulfoxide (DMSO), in constant environmental conditions, and to determine the influence of usual storage temperature, normal room lighting and laser radiation (photostability) on samples stability. The effects of irradiation on BG1189 and BG1190 molecules were also assessed through Fourier-transform infrared (FTIR) spectroscopy. FTIR spectra showed that laser radiation breaks some chemical bonds affecting the substituents and the quinazoline radical of the compounds. 相似文献
3.
4.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献
5.
6.
7.
András Gy. Németh Renáta Szabó Dr. Attila Domján Prof. György M. Keserű Dr. Péter Ábrányi-Balogh 《ChemistryOpen》2021,10(1):16-27
The development of a new three-component chromatography-free reaction of isocyanides, amines and elemental sulfur allowed us the straightforward synthesis of thioureas in water. Considering a large pool of organic and inorganic bases, we first optimized the preparation of aqueous polysulfide solution from elemental sulfur. Using polysulfide solution, we were able to omit the otherwise mandatory chromatography, and to isolate the crystalline products directly from the reaction mixture by a simple filtration, retaining the sulfur in the solution phase. A wide range of thioureas synthesized in this way confirmed the reasonable substrate and functional group tolerance of our protocol. 相似文献
8.
Mejía Hugo Fernando Giraldo Jiménez-Piqué Emilio Valdés Matías Procaccini Raúl Pellice Sergio 《Journal of Solid State Electrochemistry》2020,24(10):2451-2460
Journal of Solid State Electrochemistry - A novel material was developed using sol-gel chemistry and an environmental-friendly grafting process of clay nanoparticles. In a previous work of our... 相似文献
9.
Ortiz Adolfo Yang Jianhua Coccolo Mattia Seoane Jesús M. Sanjuán Miguel A. F. 《Nonlinear dynamics》2020,102(4):2323-2337
Nonlinear Dynamics - The main purpose of this paper is to study both the underdamped and the overdamped dynamics of the nonlinear Helmholtz oscillator with a fractional-order damping. For that... 相似文献
10.