全文获取类型
收费全文 | 166篇 |
免费 | 18篇 |
国内免费 | 41篇 |
专业分类
化学 | 157篇 |
晶体学 | 5篇 |
力学 | 4篇 |
综合类 | 9篇 |
数学 | 19篇 |
物理学 | 31篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 5篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 13篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
101.
CO在某些过渡金属表面吸附活化的DFT研究 总被引:8,自引:0,他引:8
采用DFT方法对CO在M(100)(M= Cu、Ag、Au、Pd、Pt)表面上的吸附行为进行了系统的比较性研究.结果表明,CO分子在这些过渡金属单晶表面上发生的是非解离性吸附,吸附后C-O键长都变长了,均不同程度地削弱了C-O键,继而活化了CO分子;从表面结合能、重叠集居数、轨道电子数变化等方面分析了成键强弱顺序,发现CO的吸附强度随Pd(100)、Pt (100)、Cu (100)、Ag(100)、Au(100)顺序依次减弱,并且将CO与过渡金属间的结合能(BE)、过渡金属的d电子转移数分别与水煤气变换反应活性数据进行了关联,在定性上比较好地解释了金属铜的催化活性优于其它金属的原因. 相似文献
102.
A series of poly(propylene) silica‐grafted‐hyperbranched polyester nanocomposites by grafting the modified hyperbranched polyester (Boltorn? H20), possessing theoretically 50% end carboxylic groups and 50% end hydroxyl groups, which endcapped with octadecyl isocyanate (C19), onto the surface of SiO2 particles (30 nm) through 3‐glycidoxy‐propyltrimethoxysilane (GPTS) was prepared. The effect of silica‐grafted‐modified Boltorn? H20 on the mechanical properties of polypropylene (PP) was investigated by tensile and impact tests. The morphological structure of impact fracture surface and thermal behavior of the composites were determined by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The melt viscosity of composites was investigated by melt flow index (MFI). The obtained results showed that: (1) the modified Boltorn? H20 was successfully grafted onto the SiO2 surface confirmed by FT‐IR and X‐ray photoelectron spectroscopy (XPS) analysis; (2) the incorporation of silica‐grafted‐modified Boltorn? H20 (3–5 wt% SiO2) greatly enhanced the notched impact strength as well the tensile strength of the composites; (3) the incorporation of silica‐grafted‐modified Boltorn? H20 had no influence on the melting temperature and crystallinity of PP phase; (4) the MFI of PP composites increased when the silica‐grafted‐modified Boltorn? H20 particles were added compared with PP/SiO2 or PP/SiO2‐GPTS composites. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
103.
The demonized water was added to the alkali metal salts of 2-ethythexyl phosphonic acid mono 2-ethylhexyl ester (HA) to form microemulsion of W/O type. The maximum contents of H2O in these systems reached up to the mole ratio (H2O/MA+HA) of 6.5(Li), 12 (Na) and 66 (K), respectively. They are stable when the temperature is lower than 65℃ and no water separation was observed in the ultracentrifuge under 30000r?min-1. Their electrical conductance and infrared spectra in the range of 800-4000cm-1 were studied. The variation of stretching absorption peaks of P=O, P-O-C and P-O-H and their oscillator strengths with the amount of H2O added have been recorded. 相似文献
104.
Facile and Versatile Chemoenzymatic Synthesis of Enterobactin Analogues and Applications in Bacterial Detection 下载免费PDF全文
Albert A. Lee Yi‐Chen S. Chen Elisa Ekalestari Sheng‐Yang Ho Nai‐Shu Hsu Tang‐Feng Kuo Dr. Tsung‐Shing Andrew Wang 《Angewandte Chemie (International ed. in English)》2016,55(40):12338-12342
Siderophores, such as enterobactin (Ent), are small molecules that can be selectively imported into bacteria along with iron by cognate transporters. Siderophore conjugates are thus a promising strategy for delivering functional reagents into bacteria. In this work, we present an easy‐to‐perform, one‐pot chemoenzymatic synthesis of functionalized monoglucosylated enterobactin (MGE). When functionalized MGE is conjugated to a rhodamine fluorophore, which affords RhB‐Glc‐Ent, it can selectively label Gram‐negative bacteria that utilize Ent, including some E. coli strains and P. aeruginosa. V. cholerae, a bacterium that utilizes linearized Ent, can also be weakly targeted. Moreover, the targeting is effective under iron‐limiting but not iron‐rich conditions. Our results suggest that the RhB‐Glc‐Ent probe is sensitive not only to the bacterial strain but also to the iron condition in the environment. 相似文献
105.
Dr. Hui Zhao Dr. Qi‐Song Liu Dr. Hao Geng Dr. Yuan Tian Dr. Min Cheng Dr. Yan‐Hong Jiang Dr. Ming‐Sheng Xie Dr. Xiao‐Gang Niu Dr. Fan Jiang Prof. Dr. Ya‐Ou Zhang Dr. Yuan‐Zhi Lao Prof. Dr. Yun‐Dong Wu Prof. Dr. Nai‐Han Xu Prof. Dr. Zi‐Gang Li 《Angewandte Chemie (International ed. in English)》2016,55(39):12088-12093
Described is a facile helix‐nucleating template based on a tethered aspartic acid at the N‐terminus [terminal aspartic acid (TD)]. The nucleating effect of the template is subtly influenced by the substituent at the end of the side‐chain‐end tether as indicated by circular dichroism, nuclear magnetic resonance, and molecular dynamics simulations. Unlike most nucleating strategies, the N‐terminal amine is preserved, thus enabling further modification. Peptidomimetic estrogen receptor modulators (PERMs) constructed using this strategy show improved therapeutic properties. The current strategy can be regarded as a good complement to existing helix‐stabilizing methods. 相似文献
106.
首先给出了Heisenberg型群上一类仿积算子的定义,研究了该算子的L~2→L~2有界性.其次探讨了Heisenberg型群上的Calderon-Zygmund算子,包括该算子的L~p→L~p有界性,L~1→L~(1,∞)有界性以及H~1→L~1有界性.最后证明了仿积算子也是Calderon-Zygmund算子,同时还证明了仿积算子的一些其它重要性质. 相似文献
107.
Miao Miao Jiang Xue Zhang Yi Dai Hao Gao Hong Wei Liu Nai Li Wang Wen Cai Ye Xin Sheng Yao 《中国化学快报》2008,19(3):302-304
(3S)-2-Oxo-5,12-dimethoxy-3-hydroxy-3-methylbenz[f]indoline (1), a new benzoxindole alkaloid, along with two known alkaloids, was isolated from the root barks of Goniothalamus cheliensis Hu. The structure was elucidated by spectroscopic evidences, and the absolute configuration was determined by CD spectrum. 相似文献
108.
Four new halogenated sesquiterpenes, 10‐bromo‐3‐chloro‐2,7‐epoxychamigr‐9‐en‐8α‐ol ( 1 ), 2,10β‐dibromochamigra‐2,7‐dien‐9α‐ol ( 2 ), (9S)‐2‐bromo‐3‐chloro‐6,9‐epoxybisabola‐7(14),10‐diene ( 3 ), and (9R)‐2‐bromo‐3‐chloro‐6,9‐epoxybisabola‐7(14),10‐diene ( 4 ), were characterized from the marine red alga Laurencia saitoi. In addition, two known halosesquiterpenes, 2,10‐dibromo‐3‐chlorochamigr‐7‐en‐9α‐ol ( 5 ) and isolaurenisol ( 6 ), were also isolated and identified. Their structures were established on the basis of extensive analysis of spectroscopic data. 相似文献
109.
Koc-Kan Ho Nai Fang Wang Christine Lercara Doris C. O'Toole Douglas M. Achan Edmund A. Vuocolo 《合成通讯》2013,43(5):883-895
Coupling of 4-(4-aminophenyl)butyric acid 1 with acyl halides in both organic and aqueous media were found to produce large amount of oligomeric materials. By using an in situ chlorotrimethylsilane protection/activation procedure, these oligomers were suppressed completely and the desired 4-(4-acylaminophenyl)butyric acids 3 were obtained in good yield and high purity. The method was also extended to a parallel synthesis of a three component mixture. 1H-NMR of the mixture indicated that each component was formed in a nearly stoichiometric quantity. 相似文献
110.