全文获取类型
收费全文 | 1227篇 |
免费 | 147篇 |
国内免费 | 219篇 |
专业分类
化学 | 1471篇 |
晶体学 | 4篇 |
力学 | 3篇 |
综合类 | 4篇 |
数学 | 2篇 |
物理学 | 109篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 38篇 |
2021年 | 57篇 |
2020年 | 70篇 |
2019年 | 49篇 |
2018年 | 49篇 |
2017年 | 39篇 |
2016年 | 78篇 |
2015年 | 61篇 |
2014年 | 59篇 |
2013年 | 72篇 |
2012年 | 81篇 |
2011年 | 69篇 |
2010年 | 62篇 |
2009年 | 71篇 |
2008年 | 62篇 |
2007年 | 74篇 |
2006年 | 51篇 |
2005年 | 60篇 |
2004年 | 45篇 |
2003年 | 45篇 |
2002年 | 89篇 |
2001年 | 40篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 32篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1977年 | 1篇 |
排序方式: 共有1593条查询结果,搜索用时 15 毫秒
111.
在缺氧的肿瘤细胞内, 硝基还原酶(NTR)通常过表达且其含量高低与缺氧程度呈正相关, 因此开发高选择性检测NTR的方法对早期肿瘤诊断至关重要. 本文通过修饰对硝基苯硫酚(p?NTP)到金纳米粒子(Au NPs)表面构建了一种表面增强拉曼散射(SERS)探针. 在缺氧条件下, 以还原型烟酰胺腺嘌呤二核苷酸(NADH)作为电子供体, NTR可催化还原芳香硝基为芳香胺, 导致纳米探针的SERS光谱发生变化, 从而实现NTR的高选择性检测, 检出限低至18 ng/mL. 该探针毒性低、 生物兼容性好, 可用于缺氧条件下A549细胞内的NTR分析, 为肿瘤细胞的缺氧现象评估提供了一种有效的策略. 相似文献
112.
近年来,随着材料科学、微纳加工技术和微纳尺度物质传输理论的发展,纳通道技术得到了越来越多的研究和关注。纳通道包括生物纳通道和人工纳通道,其孔径通常为1~100 nm。在这一尺度下,通道表面与通道内物质之间的作用概率大大增强,使得纳通道表现出许多与宏观体系不同的物质传输特性,例如通道表面电荷与通道内离子之间的静电作用产生了离子选择性,通道内电化学势的不对称分布产生了离子整流特性,物质传输过程中占据通道产生了阻塞脉冲特性等。纳通道中的这些物质传输特性在传感、分离、能源等领域具有广泛应用,例如通过对纳通道进行功能化修饰可以实现门控离子传输;利用亚纳米尺度的通道可以实现单分子传感;利用通道与传输物质之间的相互作用可以实现离子、分子、纳米粒子的分离;利用纳通道的离子选择性可以在通道内实现电荷分离,将不同形式的能量(如光、热、压力、盐差等)高效转化为电能。纳通道技术是化学、材料科学、纳米技术等多学科的交叉集合,在解决生物、环境、能源等基本问题方面具有良好的前景。该文综述了近10年来与纳通道物质传输理论以及纳通道技术应用相关的前沿研究,梳理了纳通道技术的发展过程,并对其在各个领域的应用进行了总结与展望。 相似文献
113.
炼厂干气中回收乙烯是扩宽C2H4来源的有效途径,但C2H4和C2H6物理性质和分子尺寸非常接近,分离困难.金属有机骨架材料(MOFs)近年来在低碳烃分离领域展现出广阔的前景.本工作采用氨吸附改性调节UTSA-280的结构,通过一维直孔道大小的调节实现C2H4/C2H6的高效分离.改性后的UTSA-280具有独特的超微孔结构能提升C2H4的吸附,而完全不吸附稍大的C2H6,实现理想的C2H4/C2H6吸附选择性(>1000).结果表明,改性后的UTSA-280的C2H4吸附量可提高至2.83 mmol/g,与未改性的材料相比增加29%,并且能阻挡C2H6的吸附,最终达到>1200的C2H4/C2H6选择性.蒙特卡罗分子模拟(GCMC)计算C2H4/C2H6混合气体(1:1)的吸附得出,改性后UTSA-280孔内的C2H4吸附相比于C2H6具有更多的吸附分布.通过C2H4/C2H6混合气体穿透实验测试,改性后的UTSA-280材料能展现出48 min以上的分离时间,相比于未改性的材料,分离性能提升近1倍. 相似文献
114.
Nir Sukenik Francesco Tassinari Shira Yochelis Oded Millo Lech Tomasz Baczewski Yossi Paltiel 《Molecules (Basel, Switzerland)》2020,25(24)
The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates. 相似文献
115.
Qun He Daobin Liu Ji Hoon Lee Yumeng Liu Zhenhua Xie Sooyeon Hwang Shyam Kattel Li Song Jingguang G. Chen 《Angewandte Chemie (International ed. in English)》2020,59(8):3033-3037
The electrochemical CO2 reduction reaction (CO2RR) to yield synthesis gas (syngas, CO and H2) has been considered as a promising method to realize the net reduction in CO2 emission. However, it is challenging to balance the CO2RR activity and the CO/H2 ratio. To address this issue, nitrogen‐doped carbon supported single‐atom catalysts are designed as electrocatalysts to produce syngas from CO2RR. While Co and Ni single‐atom catalysts are selective in producing H2 and CO, respectively, electrocatalysts containing both Co and Ni show a high syngas evolution (total current >74 mA cm?2) with CO/H2 ratios (0.23–2.26) that are suitable for typical downstream thermochemical reactions. Density functional theory calculations provide insights into the key intermediates on Co and Ni single‐atom configurations for the H2 and CO evolution. The results present a useful case on how non‐precious transition metal species can maintain high CO2RR activity with tunable CO/H2 ratios. 相似文献
116.
The design of molecularly selective interfaces can lead to efficient electrochemically-mediated separation processes. The fast growing development of electroactive materials has resulted in new electroresponsive adsorbents and membranes, with enhanced selectivity, higher uptake capacities, and improved energy performance. Here, we review progress on the interfacial design for electrochemical separations, with a focus on chemical and biological applications. We discuss the development of new electrode materials and the underlying mechanisms for selective molecular binding, highlighting areas of growing interest such as metal recovery, waste recycling, gas purification, and protein separations. Finally, we emphasize the need for integration between molecular level interface design and electrochemical engineering for the development of more efficient separation processes. We envision that electrochemical separations can play a key role towards the electrification of the chemical industry and contribute towards new approaches for process intensification. 相似文献
117.
Benjamin D. Egleston Konstantin V. Luzyanin Michael C. Brand Rob Clowes Michael E. Briggs Rebecca L. Greenaway Andrew I. Cooper 《Angewandte Chemie (International ed. in English)》2020,59(19):7362-7366
Control of pore window size is the standard approach for tuning gas selectivity in porous solids. Here, we present the first example where this is translated into a molecular porous liquid formed from organic cage molecules. Reduction of the cage window size by chemical synthesis switches the selectivity from Xe‐selective to CH4‐selective, which is understood using 129Xe, 1H, and pulsed‐field gradient NMR spectroscopy. 相似文献
118.
Jiawang Liu Ji Yang Carolin Schneider Robert Franke Ralf Jackstell Matthias Beller 《Angewandte Chemie (International ed. in English)》2020,59(23):9032-9040
For the first time, the monoalkoxycarbonylation of easily available 1,3‐diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2′‐bis(tert‐butyl(pyridin‐2‐yl)phosphanyl)‐1,1′‐binaphthalene (Neolephos), which permits the palladium‐catalyzed selective carbonylation under mild conditions, providing a general preparation of functionalized 1,3‐enynes in good‐to‐high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology include an efficient one‐pot synthesis of 4‐aryl‐4H‐pyrans as well as the rapid construction of various heterocyclic, bicyclic, and polycyclic compounds. 相似文献
119.
Jie Wang Yuqi Tang Huiyuan Chu Jiwei Shen Chaozhan Wang Yinmao Wei 《Journal of separation science》2020,43(14):2766-2772
Poly(ionic liquid)‐modified stationary phases can have multiple interactions with solutes. However, in most stationary phases, separation selectivity is adjusted by changing the poly(ionic liquid) anions. In this work, two poly(ionic liquid)‐modified silica stationary phases were prepared by introducing the cyano or tetrazolyl group on the pendant imidazolium cation on the polymer chains. Various analytes were selected to investigate their mechanism of retention in the stationary phases using different mobile phases. Two poly(ionic liquid)‐modified stationary phases can provide various interactions toward solutes. Compared to the cyano‐functionalized poly(ionic liquid) stationary phase, the tetrazolyl‐functionalized poly(ionic liquid) stationary phase provides additional cation‐exchange and π‐π interactions, resulting in different separation selectivity toward analytes. Finally, applicability of the developed stationary phases was demonstrated by the efficient separation of nonsteroidal anti‐inflammatory drugs. 相似文献
120.