全文获取类型
收费全文 | 3912篇 |
免费 | 440篇 |
国内免费 | 275篇 |
专业分类
化学 | 2788篇 |
晶体学 | 36篇 |
力学 | 208篇 |
综合类 | 23篇 |
数学 | 395篇 |
物理学 | 1177篇 |
出版年
2024年 | 12篇 |
2023年 | 119篇 |
2022年 | 214篇 |
2021年 | 194篇 |
2020年 | 216篇 |
2019年 | 209篇 |
2018年 | 200篇 |
2017年 | 159篇 |
2016年 | 246篇 |
2015年 | 219篇 |
2014年 | 275篇 |
2013年 | 320篇 |
2012年 | 405篇 |
2011年 | 416篇 |
2010年 | 238篇 |
2009年 | 235篇 |
2008年 | 207篇 |
2007年 | 179篇 |
2006年 | 140篇 |
2005年 | 76篇 |
2004年 | 56篇 |
2003年 | 33篇 |
2002年 | 41篇 |
2001年 | 22篇 |
2000年 | 35篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 23篇 |
1995年 | 8篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4627条查询结果,搜索用时 31 毫秒
41.
Mathematical Notes - The Boros–Moll polynomials $$P_m(a)$$ arise in the evaluation of a quartic integral. In the past few years, there has been some remarkable research on the properties of... 相似文献
42.
酞菁氧钛的合成及晶型转化 总被引:4,自引:0,他引:4
酞菁氧钛以联环己烷为溶剂,以邻苯二脂及四氯化钛直接反应生成。其优点是便于分离及纯化。同时对各晶型的获得及晶型间的相互转化进行了研究,并以X-射线粉末衍射及FT-IR进行了表征,并记录了不同晶型的酞菁氧钛在室温硫化硅橡胶中的吸收光谱。 相似文献
43.
批量离子交换层析和凝胶过滤层析在类人胶原蛋白I纯化中的应用 总被引:3,自引:0,他引:3
研究了利用批量离子交换层析与凝胶过滤层析相结合的方法纯化类人胶原蛋白I的最佳条件。分别考察了不同离子交换树脂、缓冲溶液pH、离子强度、进料蛋白浓度对批量离子交换的影响,以及不同凝胶过滤介质对凝胶过滤层析的影响。结果表明,采用阴离子交换树脂DEAE52吸附杂蛋白,缓冲液pH为7.0,NaCl浓度为0.2mol/L,进料蛋白浓度为40mg/mL,并采用凝胶过滤介质SephadexG-100进一步纯化后,类人胶原蛋白I的纯度可达到98.2%,总纯化倍数为3.1,总回收率为80.6%。SDS-PAGE分子量分析和N末端氨基酸序列分析均表明纯化后的类人胶原蛋白I与基因设计一致。 相似文献
44.
45.
46.
47.
Bixing Fang Lina Dong Xingwei Ding YingZi Ren Zhongsheng Lv Kuan Liu Feng Zhang Wei Zhang Jianjian Deng Hongbo Xin Xiaolei Wang 《中国化学快报》2019,30(6):1178-1181
Black fungus aerogel (BFA) exhibited interesting double-faced properties. Weexplored the diverse properties of each side of the black fungus in three aspects:water contact angle measurements, liquid selective absorption capacity and air pollutant adsorption abilities. 相似文献
48.
Renqing Lü 《天然气化学杂志》2005,14(2):119-124
The density functional theory and the cluster model methods have been employed to investigate the interactions between ethanethiol and HZSM-5 zeolites. Molecular complexes formed by the adsorption of ethanethiol on silanol H3SiOH with two coordination forms, model Bronsted acid sites of zeolite cluster H3Si(OH)Al(OH)2SiH3 interaction with ethanethiol, aluminum species adsorbed ethanethiol have been comparatively studied. Full optimization and frequency analysis of all cluster models have been carried out using B3LYP hybrid method at 3-21G basis level for hydrogen atoms and 6-31G(d) basis set level for silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms of H3Si(OH)Al(OH)2SiH3-ethanethiol, silanol-ethanethiol and Al(OH)3-ethanethiol have been studied. The calculated results showed the nature of interactions was van der Waals force as exhibited by not much change in geometric structures and properties. The preference order of ethanethiol adsorbed on HZSM-5 zeolite may be residual aluminum species, bridging hydroxyl groups and silanol OH groups from the adsorption heat. The adsorbed models of protonized ethanethiol on bridging hydroxyl OH groups and linear hydrogen bonded ethanethiol on bridging OH groups suggested in literature might not exist as revealed by this theoretical calculation. Possible adsorption models were obtained for the first time. 相似文献
49.
A room-temperature ionic liquid (IL), 1-ethyl-3-methyl-imidazolium tetrafluoroborate (1E-3MI-TFB), used for the coating of
a silica capillary enables one to reduce or invert the electroosmotic flow (EOF) in capillary zone electrophoresis. Excellent
separations of amino acids and ary lalkanoic acids were obtained. Such separations could not be obtained in a naked capillary
in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) or polycationic polymer hexadimethrine bromide
(HDB). The results indicate that 1E-3MI-TFB not only modulates the EOF but also acts as a discriminator. Further experiments
indicate that the interaction between hydrogen at C-2 carbon of IL and acid drugs plays an important role in the separation.
The text was submitted by the authors in English. 相似文献
50.
A novel polyimide (PI) based on 2,6-bis(p-aminophenyl)-benzo[1,2-d;5,4-d′]bisoxazole has been synthesized via a conventional two-stage procedure with bis(ether anhydrides) (HQDPA). The intermediate poly(amic acid) had inherent viscosities of 1.70 dl/g and could be thermally converted into light yellow polyimide film. The resulted polyimide showed excellent thermal stability, and the glass transition temperatures (Tg) were above 283 °C, the 5% weight loss temperature of the polymer was at 572 °C in N2. The thermal degradation of the polyimide was studied by thermogravimetric analysis (TGA) in order to determine the actual reaction mechanisms of the decomposition process. The activation energy of the solid-state process was determined using Flynn-Wall-Ozawa method, which does not require knowledge of the reaction mechanism, which resulted to be 361.36 kJ/mol. The activation energy of different mechanism models and pre-exponential factor (A) were determined by Coats-Redfern method. Compared with the value obtained from the Ozawa method, the actual reaction mechanism obeyed nucleation and growth model, Avrami-Erofeev function (A3) with integral form g(X) = [−ln(1−X)]3. 相似文献