全文获取类型
收费全文 | 1427篇 |
免费 | 61篇 |
国内免费 | 20篇 |
专业分类
化学 | 1044篇 |
晶体学 | 8篇 |
力学 | 26篇 |
数学 | 146篇 |
物理学 | 182篇 |
综合类 | 102篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 28篇 |
2019年 | 38篇 |
2018年 | 18篇 |
2017年 | 27篇 |
2016年 | 54篇 |
2015年 | 49篇 |
2014年 | 39篇 |
2013年 | 75篇 |
2012年 | 120篇 |
2011年 | 126篇 |
2010年 | 53篇 |
2009年 | 52篇 |
2008年 | 113篇 |
2007年 | 101篇 |
2006年 | 137篇 |
2005年 | 98篇 |
2004年 | 81篇 |
2003年 | 68篇 |
2002年 | 80篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有1508条查询结果,搜索用时 93 毫秒
951.
Hitchcock I Chudek JA Holt EM Lowe JP Rigby SP 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18061-18070
The conversion of gas adsorption isotherms into pore size distributions generally relies upon the assumption of thermodynamically independent pores. Hence, pore-pore cooperative adsorption effects, which might result in a significantly skewed pore size distribution, are neglected. In this work, cooperative adsorption effects in water adsorption on a real, amorphous, mesoporous silica material have been studied using magnetic resonance imaging (MRI) and pulsed-gradient stimulated-echo (PGSE) NMR techniques. Evidence for advanced adsorption can be seen directly using relaxation time weighted MRI. The number and spatial distributions of pixels containing pores of different sizes filled with condensate have been analyzed. The spatial distribution of filled pores has been found to be highly nonrandom. Pixels containing the largest pores present in the material have been observed to fill in conjunction with pixels containing much smaller pores. PGSE NMR has confirmed the spatially extensive nature of the adsorbed ganglia. Thus, long-range (≥40 μm) cooperative adsorption effects, between larger pores associated with smaller pores, occur within mesoporous materials. The NMR findings have also suggested particular types of pore filling mechanisms occur within the porous solid studied. 相似文献
952.
Sun-Ae Jun Chuloo Moon Cheol-Hee Kang Sean W. Kong Byoung-In Sang Youngsoon Um 《Applied biochemistry and biotechnology》2010,161(1-8):491-501
The production of 1,3-propanediol (1,3-PD) was investigated with Klebsiella pneumoniae DSM 4799 using raw glycerol without purification obtained from a biodiesel production process. Fed-batch cultures with suspended cells revealed that 1,3-PD production was more effective when utilizing raw glycerol than pure glycerol (productivity after 47 h of fermentation, 0.84 g?L?1?h?1 versus 1.51 g?L?1?h?1 with pure and raw glycerol, respectively). In addition, more than 80 g/L of 1,3-PD was produced using raw glycerol; this is the highest 1,3-PD concentration reported thus far for K. pneumoniae using raw glycerol. Repeated fed-batch fermentation with cell immobilization in a fixed-bed reactor was performed to enhance 1,3-PD production. Production of 1,3-PD increased with the cycle number (1.06 g?L?1?h?1 versus 1.61 g?L?1?h?1 at the first and fourth cycle, respectively) due to successful cell immobilization. During 46 cycles of fed-batch fermentation taking place over 1,460 h, a stable and reproducible 1,3-PD production performance was observed with both pure and raw glycerol. Based on our results, repeated fed batch with immobilized cells is an efficient fermentor configuration, and raw glycerol can be utilized to produce 1,3-PD without inhibitory effects caused by accumulated impurities. 相似文献
953.
954.
955.
956.
957.
958.
959.
960.
Ruthenium Complex “Light Switches” that are Selective for Different G‐Quadruplex Structures 下载免费PDF全文
Erin Wachter Diego Moyá Dr. Sean Parkin Dr. Edith C. Glazer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):550-559
Recognition and regulation of G‐quadruplex nucleic acid structures is an important goal for the development of chemical tools and medicinal agents. The addition of a bromo‐substituent to the dipyridylphenazine (dppz) ligands in the photophysical “light switch”, [Ru(bpy)2dppz]2+, and the photochemical “light switch”, [Ru(bpy)2dmdppz]2+, creates compounds with increased selectivity for an intermolecular parallel G‐quadruplex and the mixed‐hybrid G‐quadruplex, respectively. When [Ru(bpy)2dppz‐Br]2+ and [Ru(bpy)2dmdppz‐Br]2+ are incubated with the G‐quadruplexes, they have a stabilizing effect on the DNA structures. Activation of [Ru(bpy)2dmdppz‐Br]2+ with light results in covalent adduct formation with the DNA. These complexes demonstrate that subtle chemical modifications of RuII complexes can alter G‐quadruplex selectivity, and could be useful for the rational design of in vivo G‐quadruplex probes. 相似文献