全文获取类型
收费全文 | 2372篇 |
免费 | 77篇 |
国内免费 | 19篇 |
专业分类
化学 | 1746篇 |
晶体学 | 19篇 |
力学 | 44篇 |
数学 | 295篇 |
物理学 | 364篇 |
出版年
2022年 | 8篇 |
2021年 | 20篇 |
2020年 | 45篇 |
2019年 | 26篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 44篇 |
2015年 | 31篇 |
2014年 | 37篇 |
2013年 | 104篇 |
2012年 | 132篇 |
2011年 | 154篇 |
2010年 | 64篇 |
2009年 | 43篇 |
2008年 | 111篇 |
2007年 | 130篇 |
2006年 | 124篇 |
2005年 | 164篇 |
2004年 | 127篇 |
2003年 | 138篇 |
2002年 | 139篇 |
2001年 | 38篇 |
2000年 | 30篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 34篇 |
1996年 | 44篇 |
1995年 | 32篇 |
1994年 | 19篇 |
1993年 | 31篇 |
1992年 | 8篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 29篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 29篇 |
1981年 | 34篇 |
1980年 | 36篇 |
1979年 | 22篇 |
1978年 | 41篇 |
1977年 | 36篇 |
1976年 | 18篇 |
1975年 | 23篇 |
1974年 | 9篇 |
1973年 | 24篇 |
排序方式: 共有2468条查询结果,搜索用时 46 毫秒
111.
X-ray Photoelectron Spectroscopy was used to study a ferroan platinum crystal from the Kondyor Massif, Russian Far East. Prior to the X-ray Photoelectron Spectroscopic analyses, the nature of the crystal was confirmed by X-ray diffraction. The survey scan showed mainly the presence of Pt and Fe, with smaller amounts of O and Si. The high resolutions spectra of the Pt 4f and Fe 2p showed 18.3 atom% Fe in the crystal, which puts the composition on the lower boundary for ferroan platinum and confirms earlier analyses using other methods such as Scanning Electron Microscopy-Energy Dispersive X-ray analysis/microprobe. The binding energy of the Pt 4f5/2 was 74.0?eV and Pt 4f7/2 70.5?eV, while the Fe 2p3/2 for metallic Fe was observed at 707.2?eV. The Fe 2p3/2 for metallic Fe was significantly sharper than that of Fe 2p3/2 at 710.7?eV associated with surface material. The Raman spectrum was dominated by the Pt–Pt stretching mode at 253?cm?1. Changed orientation resulted in the observation of two bands at 127 and 139?cm?1, interpreted as being due to stretching modes of two Pt–Pt bonds with the third bond to Fe and Pt fixed. The presence of Ca-Fe-Al-Mg-Si-O on the surface was probably associated with the presence of a clinopyroxene. These minerals can be expected since the crystal came originally from a clinopyroxenite-dunite matrix. The spectra showed a variety of interferences, e.g. Al 2p with Pt 4f, Mg 2p with Fe 3p, and Ca 2p1/2 with Mg Auger, making exact determinations of the ratios of these elements difficult. 相似文献
112.
113.
114.
115.
Back Cover: Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity (Chem. Eur. J. 10/2016) 下载免费PDF全文
116.
Enantiopure Ferrocene‐Based Planar‐Chiral Iridacycles: Stereospecific Control of Iridium‐Centred Chirality 下载免费PDF全文
Ross A. Arthurs Dr. Muhammad Ismail Christopher C. Prior Dr. Vasily S. Oganesyan Dr. Peter N. Horton Dr. Simon J. Coles Dr. Christopher J. Richards 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3065-3072
Reaction of [IrCp*Cl2]2 with ferrocenylimines (Fc=NAr, Ar=Ph, p‐MeOC6H4) results in ferrocene C?H activation and the diastereoselective synthesis of half‐sandwich iridacycles of relative configuration Sp*,RIr*. Extension to (S)‐2‐ferrocenyl‐4‐(1‐methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal‐based pseudo‐tetrahedral chirality, to give both neutral and cationic half‐sandwich iridacycles of absolute configuration Sc,Sp,RIr. Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal‐centred chirality through an iron–iridium interaction in the coordinatively unsaturated cationic intermediate. 相似文献
117.
Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity 下载免费PDF全文
Dr. Amina Bensalah‐Ledoux Delphine Pitrat Thibault Reynaldo Dr. Monika Srebro‐Hooper Barry Moore II Prof. Jochen Autschbach Dr. Jeanne Crassous Prof. Stéphan Guy Dr. Laure Guy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3333-3346
Helicenes are fascinating molecules owing to their unusual properties and applications in many fields from catalysis to organic electronics. Herein, we report a straightforward pathway for the synthesis of helicene‐like molecules on a gram scale in an enantiopure form. Thin‐film materials with good propagating optical properties and very high chiroptical responses have been grown by using pulsed laser ablation without altering the structure or the enantiopurity of the molecules. Moreover, electronic and vibrational circular dichroism spectroscopies coupled with theoretical calculations enabled some dependences of the chiroptical properties with the structure to be highlighted, for example, effects of rigidification, aromatization, or the state of matter (liquid versus solid). 相似文献
118.
Andrew M. Riley Stephen J. Mills Barry V. L. Potter 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Data are presented on the magnitudes of 5 J pp and 6 J PP spin-spin coupling constants in the 31P NMR spectra of a variety of novel polyphosphite triesters. 相似文献
119.
120.
Hakim Al Garalleh Ngamta Thamwattana Barry J. Cox James M. Hill 《Journal of mathematical chemistry》2013,51(8):2020-2032
Aquaporin is a family of small membrane-proteins that are capable of transporting nano-sized materials. In the present paper, we investigate the structure of these channels and provide information about the mechanism of individual molecules being encapsulated into aquaglyceroporin (GlpF) and aquaporin-1 (AQP1) channels by calculating the potential energy. In particular, we presents a mathematical model to determine the total potential energy for the interaction of the ammonia and nitric oxide molecules and different aquaporin channels which we assume to have a symmetrical cylindrical structure. We propose to describe these interactions in two steps. Firstly, we model the nitrogen atom as a discrete point and secondly, we model the three hydrogen atoms on the surface of a sphere of a certain radius. Then, we find the total potential energy by summing these interactions. Next, by considering the nitric oxide molecule as two discrete atoms uniformly distributed interacting with GlpF and AQP1 channels then gathering all pairs of interaction to determine the potential energy. Our results show that the ammonia and nitric oxide molecules can be encapsulated into both GlpF and AQP1 channels. 相似文献