全文获取类型
收费全文 | 2888篇 |
免费 | 42篇 |
国内免费 | 7篇 |
专业分类
化学 | 1897篇 |
晶体学 | 9篇 |
力学 | 34篇 |
数学 | 504篇 |
物理学 | 493篇 |
出版年
2016年 | 48篇 |
2015年 | 40篇 |
2014年 | 41篇 |
2013年 | 62篇 |
2012年 | 73篇 |
2011年 | 108篇 |
2010年 | 56篇 |
2009年 | 70篇 |
2008年 | 92篇 |
2007年 | 96篇 |
2006年 | 96篇 |
2005年 | 83篇 |
2004年 | 76篇 |
2003年 | 80篇 |
2002年 | 72篇 |
2001年 | 48篇 |
2000年 | 45篇 |
1999年 | 27篇 |
1998年 | 33篇 |
1997年 | 22篇 |
1996年 | 35篇 |
1995年 | 41篇 |
1994年 | 37篇 |
1993年 | 37篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 34篇 |
1989年 | 38篇 |
1988年 | 52篇 |
1987年 | 40篇 |
1986年 | 37篇 |
1985年 | 49篇 |
1984年 | 31篇 |
1983年 | 22篇 |
1982年 | 24篇 |
1981年 | 40篇 |
1980年 | 38篇 |
1979年 | 47篇 |
1978年 | 46篇 |
1977年 | 28篇 |
1976年 | 26篇 |
1975年 | 36篇 |
1974年 | 24篇 |
1973年 | 36篇 |
1972年 | 24篇 |
1971年 | 36篇 |
1934年 | 27篇 |
1933年 | 23篇 |
1931年 | 17篇 |
1912年 | 18篇 |
排序方式: 共有2937条查询结果,搜索用时 15 毫秒
91.
92.
Kayla M. Diemoz Sean O. Wilson Prof. Dr. Annaliese K. Franz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(51):18349-18353
A series of new 1,3‐disiloxanediols has been synthesized, including naphthyl‐substituted and unsymmetrical siloxanes, and demonstrated as a new class of anion‐binding catalysts. In the absence of anions, diffusion‐ordered spectroscopy (DOSY) displays self‐association of 1,3‐disiloxanediols through hydrogen‐bonding interactions. Binding constants determined for 1,3‐disiloxanediol catalysts indicate strong hydrogen‐bonding and anion‐binding abilities with unsymmetrical siloxanes displaying different hydrogen‐bonding abilities for each silanol group. 相似文献
93.
94.
95.
By a comparison of the mass spectra of mono-, bis- and tris(trimethylsilyl)pyrazole isomers, characteristic influences of the different TMS-groups are revealed. An N-TMS-group forms an ion of mass 72 in the spectrum of N-TMS-pyrazole and with more than one TMS-group present, leads to the expulsion of a neutral fragment C3H8Si. Decomposition of the 4-TMS-group is more facile than the others, giving rise to a small molecular ion of intensity (approx.) 5%Σ40. In N-silylated pyrazoles without a 4-TMS-group, intensive elimination of HCN from the [M ? CH3˙]+ ion can be assigned to an unsubstituted C-3 position. In the case of unsymmetrically substituted pyrazoles without and N-TMS-group, silylation by an N-TMS acetamide may help to identify the predominating tautomer. 相似文献
96.
Cavalieri F Ashokkumar M Grieser F Caruso F 《Langmuir : the ACS journal of surfaces and colloids》2008,24(18):10078-10083
High-intensity ultrasound induces emulsification and cross-linking of protein molecules in aqueous medium. The stability and the functionality of the resultant protein-coated microbubbles are crucial in many of their applications. For example, the stability of drug-loaded microbubbles should be sufficiently long enough, in vivo, so that they can be ruptured only at specific sites for release of the drugs. In this study, we report the synthesis of stable and functional microbubbles, coated with chemically reduced lysozyme, using high-intensity ultrasound in aqueous solution. In the absence of chemical reduction, stable microbubbles were not produced with native lysozyme, indicating the importance of free -SH functional groups for protein cross-linking. The degree of cross-linking between lysozyme molecules was controlled by manipulating both the extent of chemical reduction of the intramolecular disulfide bonds and sonication time. The lysozyme-coated microbubbles are stable for several months and retain the enzymatic (antimicrobial) activity of lysozyme. The layer-by-layer (LbL) deposition of polyelectrolytes onto the protein-shell air-core template has been used as a versatile procedure to modify the surface properties of the microbubbles, indicating the possibility of adsorbing potential drugs and/or biolabels on the surface of these microbubbles for therapeutic and diagnostic applications. 相似文献
97.
Grazia Cafeo Dr. Franz H. Kohnke Prof. Luca Valenti Andrew J. P. White Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(36):11593-11600
10α,20α‐Bis(4‐nitrophenyl)calix[4]pyrrole ( 1 ) forms 1:1 complexes with anions of selected aromatic hydroxy acids in which the host orientation within the guest is controlled by a change in the pH value. Some bis‐anionic guests, including those obtained from 4‐hydroxybenzoic acid, 1,4‐ and 1,3‐benzenedicarboxylic acids, induce the self‐assembly of molecular capsules involving two molecules of the receptor. 1H NMR data and solid‐state structures of the 1:1 complex of 1 with p‐C6H4(COOH)(COO?)+NMe4 and the 2:1 capsule [( 1 )2m‐C6H4(COO?)2(+NMe4)2] provide structural details in solution and in the solid state. 相似文献
98.
99.
Stone MM Franz AH Lebrilla CB 《Journal of the American Society for Mass Spectrometry》2002,13(8):964-974
Non-covalent inclusion complexes formed between amino acids and derivatized calix[6]arenes are observed in MALDI mass spectrometry. The methyl, ethyl, and propyl ester derivatives of calix[6]arene yielded amino acid complexes, while the smaller calix[4]arene analogs did not. Similarly the underivatized calix[6]arene and calix[4]arene did not produce complexes. Amino acid complexes were observed for nearly all 20 amino acids in time-of-flight (TOF) analysis. In Fourier transform mass spectrometry (FTMS) analysis, however, only the most basic amino acids arginine, histidine, and lysine formed stable adducts. The complexes were abundant under matrix-assisted laser desorption ionization (MALDI) conditions, which suggested favorable interactions between host and guest. 相似文献
100.