全文获取类型
收费全文 | 898篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
化学 | 723篇 |
晶体学 | 7篇 |
力学 | 20篇 |
数学 | 44篇 |
物理学 | 140篇 |
出版年
2023年 | 12篇 |
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 14篇 |
2013年 | 43篇 |
2012年 | 57篇 |
2011年 | 54篇 |
2010年 | 44篇 |
2009年 | 31篇 |
2008年 | 52篇 |
2007年 | 76篇 |
2006年 | 65篇 |
2005年 | 40篇 |
2004年 | 61篇 |
2003年 | 43篇 |
2002年 | 35篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有934条查询结果,搜索用时 0 毫秒
211.
Chemoenzymatic synthesis of sacranosides a and B 总被引:1,自引:0,他引:1
Direct beta-glucosidation between (-)-myrtenol and nerol and D-glucose (3) using the immobilized beta-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave myrtenyl O-beta-D-glucoside (4) and neryl O-beta-D-glucoside (10), respectively. The coupling of the myrtenyl or neryl O-beta-D-glucopyranoside congeners (7 or 13) and 2,3,4-tri-O-benzoyl-beta-L-arabinopyranosyl bromide (8) afforded the coupled products (9 or 14), respectively. Deprotection of the coupled products (9 or 14) afforded the synthetic myrtenyl 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (Sacranoside A, 1) or neryl 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (Sacranoside B, 2), respectively. 相似文献
212.
Nishibori E Terauchi I Sakata M Takata M Ito Y Sugai T Shinohara H 《The journal of physical chemistry. B》2006,110(39):19215-19219
The X-ray structure of Sc(3)C(82) is redetermined by the MEM/Rietveld method by using synchrotron radiation powder data at SPring-8, where the C(2) encapsulated structure available to discuss the Sc-Sc interatomic distances has been determined. The encapsulated three scandium atoms form a triangle shape. A spherical charge distribution originating from the C(2) molecule is located at the center of the triangle. Interatomic distances between Sc and Sc are 3.61(3) A in the triangle. The distance between Sc and the center of the C(2) molecule is 2.07(1) A. 相似文献
213.
Remote Control of the Planar Chirality in Peptide‐Bound Metallomacrocycles and Dynamic‐to‐Static Planar Chirality Control Triggered by Solvent‐Induced 310‐to‐α‐Helix Transitions 下载免费PDF全文
Fumihiko Mamiya Dr. Naoki Ousaka Prof. Dr. Eiji Yashima 《Angewandte Chemie (International ed. in English)》2015,54(48):14442-14446
The dynamic planar chirality in a peptide‐bound NiII‐salphen‐based macrocycle can be remotely controlled. First, a right‐handed (P)‐310‐helix is induced in the dynamic helical oligopeptides by a chiral amino acid residue far from the macrocyclic framework. The induced planar chirality remains dynamic in chloroform and acetonitrile, but is almost completely locked in fluoroalcohols as a result of the solvent‐induced transition of the peptide chains from a 310‐helix to a wider α‐helix, which freezes the rotation of the pendant peptide units around the macrocycle. 相似文献
214.
Hydrothermal routes to prepare nanocrystalline mesoporous SnO2 having high thermal stability 总被引:13,自引:0,他引:13
Fujihara S Maeda T Ohgi H Hosono E Imai H Kim SH 《Langmuir : the ACS journal of surfaces and colloids》2004,20(15):6476-6481
We report simple hydrothermal routes to prepare thermally stable SnO2 particles having high specific surface areas and mesoporosity. The preparation method includes a new combination of synthetic processes: hydrolysis of tin(IV) chloride at 95 degrees C in the absence of alkaline solutions (aqueous NH3 or NaOH), formation of nanocrystalline SnO2, and subsequent hydrothermal treatments at temperatures between 100 and 200 degrees C. After annealing treatments of the hydrothermally treated SnO2 particles at 400 or 500 degrees C, their crystallite sizes remained smaller than 7.7 nm and their specific surface areas were still higher than 110 m2/g, indicative of the high thermal stability against particle growth and sintering. Furthermore, mesoporosity evolved with a relatively narrow pore size distribution typically in the range of 3.0-4.3 nm. The effects of the hydrothermal treatment were explained by uniformization of the particle size that was beneficial to the suppression of particle growth. 相似文献
215.
A chiral regioregular polythiophene (PT), poly[3-[4-((R)-4-ethyl-2-oxazolin-2-yl)phenyl]thiophene] (poly-1), forms chiral aggregates which exhibit a unique induced circular dichroism (ICD) in the pi-pi transition region derived from the supramolecular chirality in the presence of various poor solvents or metal salts in chloroform. We report here that the chirality of such supramolecular aggregates can be switched ("on" and "off") through electron transfer. We have found that upon the addition of copper(II) trifluoromethanesulfonate [Cu(OTf)(2)] to the chiral aggregates of poly-1 in a chloroform-acetonitrile mixture, the ICD disappears because of the oxidative doping of the poly-1 main chain, while a further addition of amines such as triethylenetetramine (TETA) induces undoping of the poly-1 which results in the reappearance of the ICDs. Therefore, the supramolecular chirality of the poly-1 assemblies was reversibly controlled by the addition or removal of an electron from the poly-1 main chain. This may be the first example of a reversible supramolecular chirality switch on chiral PT aggregates. We investigated the mechanism of the chirality switch through the doping and undoping process on the polymer main chain by means of absorption and CD spectroscopies, ESR, cyclic voltammetry, X-ray diffraction, and AFM measurements. 相似文献
216.
An iridoid glucoside dimer and a non-glycosidic iridoid from the leaves of Lasianthus wallichii 总被引:1,自引:0,他引:1
Takeda Y Shimidzu H Mizuno K Inouchi S Masuda T Hirata E Shinzato T Aramoto M Otsuka H 《Chemical & pharmaceutical bulletin》2002,50(10):1395-1397
A new iridoid glucoside dimer (1) and a non-glycosidic iridoid (2) was isolated together with the known compounds, asperuloside (3), paederoside (4), daphylloside (5), citroside A (6) and benzyl 6-O-alpha-L-rhamnopyranosyl-beta-D-glucopyranoside (7), from the leaves of Lasianthus wallichii. The structures of the new compounds were elucidated by spectroscopic and chemical evidence. 相似文献
217.
Furusho Y Goto H Itomi K Katagiri H Miyagawa T Yashima E 《Chemical communications (Cambridge, England)》2011,47(35):9795-9797
A tetranuclear Cu(I) double-stranded helicate was synthesized from ketimine-bridged tris(bipyridine) ligands and Cu(I) ions, and the racemate was successfully resolved by diastereomeric salt formation using an optically pure phosphate anion followed by anion exchange with NaPF(6) without racemization. 相似文献
218.
Kamio E Yonemura S Ono T Yoshizawa H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(23):13287-13298
We demonstrate a simple, unique method for preparing microcapsules with holes in their shells. Cross-linked polymelamine microcapsules are prepared by the phase-separation method. The holey shell of each microcapsule is synthesized on the surface of an oil-in-water (O/W) emulsion droplet where a water-soluble polymeric surfactant and an oil-soluble surfactant are competitively adsorbed. The water-soluble polymeric surfactant provides a reaction site for shell formation. The oil-soluble surfactant molecules seem to self-assemble while the shells are being formed, so holes appear where they assemble. The critical degree of surface coverage of an emulsion droplet by the water-soluble polymeric surfactant needed to form the holey shells is determined to be 0.90 from theoretical calculations in which competitive adsorption is considered. Theoretical consideration suggests that the size and quantity of the holes in the microcapsule shells are controlled by the composition of the surfactants adsorbed on the surface of an emulsion droplet. This theoretical consideration is confirmed by experiments. The prepared microcapsule with controllable macroholes in its shell has the potential to be used for controlled release applications and can be used to fabricate a microcapsule that encapsulates hydrophilic compounds. 相似文献
219.
Yoshiyuki Manabe Roberta Marchetti Yohei Takakura Masahiro Nagasaki Wataru Nihei Tomoyuki Takebe Katsunori Tanaka Kazuya Kabayama Fabrizio Chiodo Shinya Hanashima Yoshihiro Kamada Eiji Miyoshi Hari Prasad Dulal Yoshiki Yamaguchi Yoshiyuki Adachi Naohito Ohno Hiroshi Tanaka Alba Silipo Koichi Fukase Antonio Molinaro 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(51):18870-18875
The core fucose, a major modification of N‐glycans, is implicated in immune regulation, such as the attenuation of the antibody‐dependent cell‐mediated cytotoxicity of antibody drugs and the inhibition of anti‐tumor responses via the promotion of PD‐1 expression on T cells. Although the core fucose regulates many biological processes, no core fucose recognition molecule has been identified in mammals. Herein, we report that Dectin‐1, a known anti‐β‐glucan lectin, recognizes the core fucose on IgG antibodies. A combination of biophysical experiments further suggested that Dectin‐1 recognizes aromatic amino acids adjacent to the N‐terminal asparagine at the glycosylation site as well as the core fucose. Thus, Dectin‐1 appears to be the first lectin‐like molecule involved in the heterovalent and specific recognition of characteristic N‐glycans on antibodies. 相似文献
220.
Dr. Feng Dang Dr. Yuya Oaki Takao Kokubu Dr. Eiji Hosono Dr. Haoshen Zhou Prof. Dr. Hiroaki Imai 《化学:亚洲杂志》2013,8(4):760-764
Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO3 precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol % Co exhibited excellent cycle performance as an anode material for Li‐ion batteries. The solid–electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li2O, during the conversion reaction in the charge–discharge cycle. The Co nanoparticles and SEI provide the electron and Li‐ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li‐ion batteries. 相似文献