全文获取类型
收费全文 | 8719篇 |
免费 | 1343篇 |
国内免费 | 1261篇 |
专业分类
化学 | 6672篇 |
晶体学 | 144篇 |
力学 | 468篇 |
综合类 | 77篇 |
数学 | 867篇 |
物理学 | 3095篇 |
出版年
2024年 | 50篇 |
2023年 | 195篇 |
2022年 | 365篇 |
2021年 | 385篇 |
2020年 | 446篇 |
2019年 | 448篇 |
2018年 | 324篇 |
2017年 | 363篇 |
2016年 | 422篇 |
2015年 | 458篇 |
2014年 | 518篇 |
2013年 | 688篇 |
2012年 | 742篇 |
2011年 | 804篇 |
2010年 | 567篇 |
2009年 | 493篇 |
2008年 | 583篇 |
2007年 | 463篇 |
2006年 | 417篇 |
2005年 | 350篇 |
2004年 | 267篇 |
2003年 | 233篇 |
2002年 | 270篇 |
2001年 | 191篇 |
2000年 | 172篇 |
1999年 | 134篇 |
1998年 | 103篇 |
1997年 | 103篇 |
1996年 | 103篇 |
1995年 | 105篇 |
1994年 | 97篇 |
1993年 | 81篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 44篇 |
1989年 | 50篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 27篇 |
1985年 | 37篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1959年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
A very sensitive electroanalytical method was employed to determine bergenin in phosphate buffer with a pH of 6.0, bergenin was accumulated at a 4-(2-pyridylazo)-resorcinol (PAR) polymer film modified glassy carbon electrode (GCE) surface under the condition of open-circuit. In the following anodic sweep from −0.4 to 0.8 V, bergenin adsorbed at the PAR polymer film modified electrode surface, was oxidized and yielded a sensitive oxidation peak at 0.595 V. Due to its unique structure and extraordinary properties, the PAR polymer film shows higher accumulation efficiency toward bergenin compared with a bare GCE. Hence, the amount of bergenin at the PAR polymer film modified GCE surface increases significantly, and finally the oxidation peak current improves greatly. The experimental conditions, such as supporting electrolyte, pH value, accumulation time and scan rate, were optimized for the measurement of bergenin, and a sensitive electroanalytical method was proposed for bergenin determination. The oxidation peak current varies linearly with the concentration of bergenin over the range of 2.0 × 10−7 to 1.2 × 10−5 mol/L, and the detection limit is 2.0 × 10−8 mol/L after 3 min open-circuit accumulation. The relative standard deviation of the same electrode in 10 successive scans is 1.8% for 1.0 × 10−6 mol/L bergenin and 2.1% for interelectrodes, indicating excellent reproducibility. This new method was successfully demonstrated with bergenin tablets and diluted urine. 相似文献
122.
123.
A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition.A closely packed electroless copper film with strong adhesion is successfully formed by AFM observation.XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs. 相似文献
124.
125.
历史文物建筑修复与保护的首要步骤是对建材构件进行成分解析。但成型的混凝土构件成分复杂,传统技术难以直接分析。微区X射线荧光光谱具有速度快、无需前处理、可获得大面积高分辨的元素成像等优势,可用于此类混合物的原位分析。本文采用束斑为20μm的微区X射线荧光光谱仪,扫描成型混凝土构件以获得混合成分的元素分布图,结合基本参数定量法,对上海地区典型历史建筑混泥土构件进行元素定量。分析结果有效地解析了混凝土构建中骨料和凝胶材料的成分和含量,鉴别了涂层成分,解析了拌混工艺,鉴别了局部污染元素和致劣元素并分析致劣原因,为历史建筑修复材料选配、拌混工艺选择、除污及保护性预防劣化提供了科学的数据支撑。 相似文献
126.
A novel thermo-responsive 2,9(10),16(17),23(24)-tetrakis[(3-carboxyacrylamide) phthalocyaninato] zinc (ZnPc)-g-TiO2-g-poly(N-isopropylacrylamide) (PNIPAM) photocatalyst modified with phthalocyanines was prepared. The photocatalyst exhibited thermo-responsive properties due to the introduction of PNIPAM, which performed recovery for reuse above the lower critical solution temperature (LCST, about 26 °C). ZnPc-g-TiO2-g-PNIPAM effectively expanded the light response range to the visible light region and inhibited the recombination of electron–hole pairs, which enhanced the performance of the photocatalyst. As expected, ZnPc-g-TiO2-g-PNIPAM (0.3 g/L) exhibited excellent photocatalytic performance for the removal of Rhodamine B (RhB, 1.0 × 10−5 mol/L) and methylene blue (MB, 1.0 × 10−5 mol/L) under visible light, which reached 97.2% and 88.6% at 20 °C within 40 min, respectively. Furthermore, the influence of temperature upon photocatalytic performance was also investigated. When the temperature increased from 20 °C to 45 °C, the removal of RhB decreased by approximately 53.8%. The stability of the photocatalyst demonstrated that the photocatalytic activity was still above 80% for the removal of RhB after 3 cycles. Above all, this work provided an intelligent thermally responsive photocatalyst based on phthalocyanine for water purification under visible light. 相似文献
127.
模糊有限自动机两个算子的若干性质 总被引:1,自引:1,他引:0
在文[1]定义了模糊有限自动机的bifuzzy seccessor算子和bifuzzy source算子的基础上,着重研究它们之间的基本性质及关系,并得到几个重要的性质定理。 相似文献
128.
129.
Leqing Lin Yu Zhong Haoyang Lin Chenglong Wang Zhifei Yang Qian Wu Di Zhang Wenguo Zhu Yongchun Zhong Yuwei Pan Jianhui Yu Huadan Zheng 《Molecules (Basel, Switzerland)》2022,27(13)
Spider silk is one of the hottest biomaterials researched currently, due to its excellent mechanical properties. This work reports a novel humidity sensing platform based on a spider silk-modified quartz tuning fork (SSM-QTF). Since spider silk is a kind of natural moisture-sensitive material, it does not demand additional sensitization. Quartz-enhanced conductance spectroscopy (QECS) was combined with the SSM-QTF to access humidity sensing sensitively. The results indicate that the resonance frequency of the SSM-QTF decreased monotonously with the ambient humidity. The detection sensitivity of the proposed SSM-QTF sensor was 12.7 ppm at 1 min. The SSM-QTF sensor showed good linearity of ~0.99. Using this sensor, we successfully measured the humidity of disposable medical masks for different periods of wearing time. The results showed that even a 20 min wearing time can lead to a >70% humidity in the mask enclosed space. It is suggested that a disposable medical mask should be changed <2 h. 相似文献
130.