全文获取类型
收费全文 | 1543篇 |
免费 | 46篇 |
国内免费 | 2篇 |
专业分类
化学 | 1136篇 |
晶体学 | 19篇 |
力学 | 31篇 |
数学 | 149篇 |
物理学 | 256篇 |
出版年
2023年 | 8篇 |
2022年 | 27篇 |
2021年 | 50篇 |
2020年 | 42篇 |
2019年 | 37篇 |
2018年 | 21篇 |
2017年 | 18篇 |
2016年 | 37篇 |
2015年 | 56篇 |
2014年 | 46篇 |
2013年 | 102篇 |
2012年 | 113篇 |
2011年 | 108篇 |
2010年 | 58篇 |
2009年 | 76篇 |
2008年 | 111篇 |
2007年 | 85篇 |
2006年 | 70篇 |
2005年 | 50篇 |
2004年 | 68篇 |
2003年 | 53篇 |
2002年 | 43篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 28篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1991年 | 5篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1985年 | 8篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 6篇 |
1924年 | 2篇 |
1918年 | 2篇 |
排序方式: 共有1591条查询结果,搜索用时 218 毫秒
81.
A self-supporting ZSM-5 monolith with a hierarchical porosity was prepared using polyurethane foam (PUF) as a structural template and a hydrothermal synthesis procedure. The synthesized monolith was characterized and investigated towards the adsorption and catalytic oxidation of trichloroethylene (TCE). Adsorption of TCE was studied gravimetrically and oxidation of TCE was studied using a vapor-phase down-flow reactor. Monolithic ZSM-5 displayed good sorption properties and completely oxidized TCE. Conversion levels of 50% and 90% were achieved at reduced temperatures (by ~50 ℃) when compared with the conversion temperatures obtained from the powder counterparts. Besides the activity of the monolith towards TCE adsorption and oxidation, it was stable and enhanced diffusion, thereby reducing pressure drops to a great extent owing to its hierarchical porous nature. 相似文献
82.
Dr. Jonathan A. Robson Dr. Markéta Kubánková Tamzin Bond Rian A. Hendley Dr. Andrew J. P. White Prof. Dr. Marina K. Kuimova Prof. Dr. James D. E. T. Wilton-Ely 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21615-21619
A new family of robust, non-toxic, water-compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity-sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells. 相似文献
83.
ngela Liberal ngela Fernandes Nikolaos Polyzos Spyridon A. Petropoulos Maria Inês Dias Jos Pinela Jovana Petrovi Marina Sokovi Isabel C.F.R. Ferreira Lillian Barros 《Molecules (Basel, Switzerland)》2020,25(23)
Petroselinum crispum Mill., Fuss., is a culinary vegetable used as an aromatic herb that garnishes and flavours a great variety of dishes. In the present study, the chemical profiles and bioactivities of leaf samples from 25 cultivars (three types: plain- and curly-leafed and turnip-rooted) from this species were assessed. Seven phenolic compounds were identified in all the varieties, including apigenin and kaempherol derivates. Apigenin-O-pentoside-O-hexoside was the major compound in all the tested parsley types (20, 22 and 13 mg/g of extract, respectively) and responsible for its excellent antioxidant activity, also investigated in this study. Antimicrobial activities were also explored, and the results revealed a good bioactivity against specific tested pathogens, such as bacteria and fungi. In conclusion, the leaves of all the types of P. crispum are a good source of natural bioactive compounds that confer health benefits, and thus, they should be part of a balanced and diversified diet. 相似文献
84.
Optimized HR-AR-DFB laser structures are proposed foreseeing their use in directly modulated optical communication systems. They present, simultaneously, high single-longitudinal-mode yield, stable single-longitudinal-mode operation, high power efficiency and stable emitted wavelength. Lasers harder to manufacture were previously proposed elsewhere and did not succeed in achieving such high performances. A detailed assessment of the proposed lasers is presented and discussed. 相似文献
85.
86.
87.
Cobalt compounds supported on 2-, 3-, and 4-aminopyridine-modified silica surfaces, named Sil2Co, Sil3Co, and Sil4Co, respectively, were used to catalyze the decomposition of hydrogen peroxide on ethanolic solutions at 293, 298, and 303 K. The calculated k values (x10(-4) s(-1)) for Sil2Co, Sil3Co, and Sil4Co are 0.65, 1.24, and 4.78 (293 K); 1.23, 1.87, and 6.33 (298 K); and 1.80, 2.80, and 10.30 (303 K), respectively. All obtained results evidence that such decomposition is a first-order reaction. Zinc-, nickel-, and copper-supported compounds were also tested, but exhibited a very low catalytic activity. By using the k values at 298 and 303 K, and employing the equation ln (k1/k2) = E(a)/R(1/T2-1/T1), the activation energy values for the considered reaction were Sil2Co = 57.20, Sil3Co = 60.60, and Sil4Co = 73.10 kJ mol(-1), respectively. The low values calculated for E(a) are in agreement with a free-radical mechanism. 相似文献
88.
89.
90.
J.M. Robson 《Physics letters. [Part B]》1976,65(3):225-226
A simple focussing device in the form of a cone has been used to produce a localised flux increase of ultra-cold neutrons. 相似文献