全文获取类型
收费全文 | 6679篇 |
免费 | 639篇 |
国内免费 | 347篇 |
专业分类
化学 | 3838篇 |
晶体学 | 501篇 |
力学 | 174篇 |
综合类 | 10篇 |
数学 | 319篇 |
物理学 | 2823篇 |
出版年
2024年 | 10篇 |
2023年 | 115篇 |
2022年 | 85篇 |
2021年 | 102篇 |
2020年 | 198篇 |
2019年 | 178篇 |
2018年 | 184篇 |
2017年 | 200篇 |
2016年 | 361篇 |
2015年 | 222篇 |
2014年 | 298篇 |
2013年 | 860篇 |
2012年 | 287篇 |
2011年 | 367篇 |
2010年 | 333篇 |
2009年 | 412篇 |
2008年 | 366篇 |
2007年 | 489篇 |
2006年 | 384篇 |
2005年 | 336篇 |
2004年 | 270篇 |
2003年 | 240篇 |
2002年 | 179篇 |
2001年 | 157篇 |
2000年 | 134篇 |
1999年 | 150篇 |
1998年 | 121篇 |
1997年 | 79篇 |
1996年 | 90篇 |
1995年 | 60篇 |
1994年 | 53篇 |
1993年 | 43篇 |
1992年 | 39篇 |
1991年 | 25篇 |
1990年 | 37篇 |
1989年 | 24篇 |
1988年 | 33篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 21篇 |
1983年 | 7篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 7篇 |
排序方式: 共有7665条查询结果,搜索用时 31 毫秒
81.
A. I. Barabash 《Journal of Molecular Structure》1998,450(1-3):23-28
The influence of geometric isotopic effects on the Curie temperature of hydrogen-containing crystals was considered. The experimental pressure and concentration dependencies of the Curie temperature have been explained in a framework of the pseudo-spin Ising model, by taking into account the changes in geometry of hydrogen bonds under pressure and due to isotopic exchange. 相似文献
82.
K. Babu V. Ganesh Shridhar R. Gadre Nour E. Ghermani 《Theoretical chemistry accounts》2004,111(2-6):255-263
Experimental and theoretical studies of electron densities and the corresponding derived entities such as electrostatic potentials have been the primary means of understanding the chemical nature and electronic properties of crystalline substances. Conventional crystal calculation methods such as the embedded cluster models are capable of performing calculations on small and medium-sized molecules, while periodic ab initio methods can treat crystals with up to 200 atoms per unit cell. A linear scaling method, viz. the molecular tailoring approach, has recently been developed for obtaining ab initio quality one-electron properties. In the present study, the molecular tailoring approach is employed to generate electron density, electrostatic potential and interaction density maps with the ibuprofen crystal as a test case. The interaction density and electrostatic potential maps produced in the present work succinctly bring out the actual crystalline environment around a given reference molecule by including the interactions with atoms in its neighborhood. The results obtained from the molecular tailoring approach may thus be expected to enhance our understanding of the environment in the crystalline material with reasonably small computational effort.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
83.
Koichi Tanaka Hideyuki Takano Zofia Urbanczyk-lipkowska 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(3-4):281-285
The host compounds 1,1’-binaphthyl-2,2′-dihydroxy-5,5′-dicarboxylic acid (1) and 1,1′-binaphthyl-2,2′-dihydroxy-6,6′-dicarboxylic acid (2) have been synthesized, and their inclusion properties have been studied. Inclusion complexes formed by 1 and 2 with volatile guests such as acetone and methanol release the guests only at much higher temperatures than their boiling
points. The crystal structures of the inclusion complexes have been determined from single crystal X-ray diffraction data
and show different host lattices. 相似文献
84.
The geometrical and energetical parameters of hydrogen fluoride and hydrogen chloride crystals are calculated using the periodic Hartree–Fock method with 6-31G and 6-31G(d,p) basis sets. The comparison of the stabilisation energies reveals that HCl crystals are about 75% less stable than HF crystals. The activation energy for collective proton movements are computed and discussed in view of data of isolated infinite chains. The barriers of 13.1 and 40.0 kcal mol−1 at 6-31G(d,p) level are found for HF and HCl crystals. 相似文献
85.
R. Parthasarathy Ravi V. Prasad P. R. Sarode K. J. Rao 《Journal of Chemical Sciences》1982,91(3):201-205
The exafs of Co2+ has been studied in rare earth cobaltites and in sulphate and borate glasses. It has been found that the environment of Co2+ ions is very similar in these cases. It appears feasible to study local structures in glasses using probe ion exafs.
Communication No. 151 from the Solid State and Structural Chemistry Unit. 相似文献
86.
This article examines the current status of Markov processes in single molecule fluorescence. For molecular dynamics to be described by a Markov process, the Markov process must include all states involved in the dynamics and the first-passage time (FPT) distributions out of those states must be describable by a simple exponential law. The observation of non-exponential FPT distributions or other evidence of non-Markovian dynamics is common in single molecule studies and offers an opportunity to expand the Markov model to include new dynamics or states that improve understanding of the system. 相似文献
87.
By using a chiral molecular motor as a dopant in a cholesteric liquid‐crystalline film, fully reversible control of the reflection color of this film across the entire visible spectrum is possible. The large difference in helical twisting power between the two isomeric forms of the motor allows efficient light‐ and heat‐induced switching of the helicity of the cholesteric liquid‐crystal superstructure. 相似文献
88.
Ben-zhong Tang Xiang-xing Kong Xin-de Feng Department of Chemistry Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong China Department of Polymer Science & Engineering College of Chemistry Peking University Beijing China 《高分子科学》1999,(3):289-294
A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily "tunab1e" by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments. 相似文献
89.
Alexander Kane Ren-Fan Shao Joseph E Maclennan Lixing Wang David M Walba Noel A Clark 《Chemphyschem》2007,8(1):170-174
We demonstrate, both theoretically and experimentally, that it is possible to use an electric field to drive the formation of macroscopic chiral (conglomerate) domains from an initially homogeneous fluid racemate. Field-induced segregation is exhibited in a fluid smectic liquid-crystal phase of a racemic mesogen, wherein enantiomerically-enriched domains are readily identifiable by their chiral electro-optical response. The sharp field-generated boundaries that form between opposite-handed domains broaden by diffusion in the absence of field, but reform rapidly if the field is switched on again, providing unambiguous evidence for the field-driven physical separation of enantiomers. A mean-field model successfully describes the steady-state and the dynamic evolution of conglomerate formation. 相似文献
90.
报道了一种单颗粒微电极制备新方法, 并研究了LaNi4.7Al0.3球形单颗粒微电极的电化学行为. 相似文献