全文获取类型
收费全文 | 10043篇 |
免费 | 1192篇 |
国内免费 | 383篇 |
专业分类
化学 | 5878篇 |
晶体学 | 504篇 |
力学 | 136篇 |
综合类 | 42篇 |
数学 | 90篇 |
物理学 | 4968篇 |
出版年
2023年 | 56篇 |
2022年 | 104篇 |
2021年 | 135篇 |
2020年 | 196篇 |
2019年 | 192篇 |
2018年 | 194篇 |
2017年 | 191篇 |
2016年 | 369篇 |
2015年 | 343篇 |
2014年 | 441篇 |
2013年 | 827篇 |
2012年 | 525篇 |
2011年 | 706篇 |
2010年 | 615篇 |
2009年 | 713篇 |
2008年 | 693篇 |
2007年 | 824篇 |
2006年 | 741篇 |
2005年 | 557篇 |
2004年 | 576篇 |
2003年 | 480篇 |
2002年 | 374篇 |
2001年 | 277篇 |
2000年 | 240篇 |
1999年 | 187篇 |
1998年 | 186篇 |
1997年 | 134篇 |
1996年 | 121篇 |
1995年 | 130篇 |
1994年 | 115篇 |
1993年 | 68篇 |
1992年 | 64篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Iain D. H. Oswald 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(8):1021-1022
A new crystalline form of αβ‐d ‐lactose prepared by oven drying a concentrated aqueous solution of d ‐lactose is a lesson in the power of observation and the rigorous analysis of powder samples. 相似文献
2.
Andrey V. Lunchev Dr. Samuel A. Morris Dr. Rakesh Ganguly Prof. Andrew C. Grimsdale 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1819-1823
A route to the synthesis of novel 5,7-diazapentacenes and some preliminary studies on their properties is reported. A single crystal X-ray diffraction study of the dihexyl derivative showed it had formed a dimer during the analysis. The materials possess lower lying frontier orbitals than pentacene and may have potential applications in organic electronic devices. This synthetic method may be applicable to the synthesis of other azaacenes. 相似文献
3.
《Mendeleev Communications》2022,32(2):180-182
New amino phospha betaines were obtained by quaternization of potassium salt of amino phosphonate and higher alkyl bromides. The structure of isopropyl (N-dodecyl-N,N- dimethylammoniomethyl)phosphonate was confirmed by single crystal X-ray diffraction. All synthesized compounds demonstrate high antibacterial and antifungal activities. 相似文献
4.
《Mendeleev Communications》2022,32(6):742-744
A solution of a histone-like protein from Spiroplasma melliferum (HUSpm) was examined by small-angle X-ray scattering (SAXS). The experimental SAXS curve was compared with those calculated for the HUSpm structures from the PDB databank obtained by both X-ray diffraction analysis and nuclear magnetic resonance spectroscopy. The model of the HUSpm structure in solution, which best agrees with the experimental SAXS data, has a shorter distance between the centers of mass of the HUSpm monomers compared to the crystal structure, indicating that the HUSpm monomers can be located closer to each other in solution than in the crystalline state. 相似文献
5.
Dr. Christoph Ludwig Teske Dr. Anna-Lena Hansen Prof. Dr. Richard Weihrich Prof. Dr. Lorenz Kienle Marius Kamp Kasper Pieter van der Zwan Prof. Dr. Jürgen Senker Dr. Carsten Dosche Prof. Dr. Gunther Wittstock Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6763-6772
A new preparation route is developed for the synthesis of needle-like crystals of [Au(S2CNH2)2]SCN, which avoids disproportionation of the AuI salt used as a starting material. In the crystal structure, the two crystallographically independent AuIII centers are in a square-planar environment of two S2CNH2 ligands. The Hirshfeld surface analysis reveals the presence of noncovalent intermolecular S⋅⋅⋅S interactions, which are essential for the spatial arrangement of the molecules. Density functional theory (DFT) calculations including dispersion and damping corrections result in a unit cell volume very close to the value determined experimentally. Thermal decomposition in an inert atmosphere generates black needles with lengths of up to 500 μm. X-ray powder diffraction and pair distribution function analyses demonstrate that the needles are composed of nanosized crystals with a volume-weighted average domain size of 20(1) nm. According to results of X-ray photoemission experiments, the black needles are covered by a nitrogen-rich carbon nitride with composition near (CN)2N. 13C solid-state NMR investigations indicate that two different carbon species are present, with signals corresponding well to heptazine units as in melon and triazine units as in poly(triazin imide) type compounds. Scanning transmission electron microscopy tomography evidences that the needles are composed of slightly elongated nanoparticles. 相似文献
6.
衍射光栅可以将不同波长的光在空间上分离开,在光谱分析领域中有广泛应用.利用光栅的衍射来测量光栅常数是大学物理实验中的一个典型实验,而本文介绍的正是光栅衍射实验中的两个有趣现象:一是旋转光栅时,谱线的偏转角存在一个最小值;二是光栅旋转到一定角度时,衍射光斑会逐渐消失在视野中.论文从理论上分析解释这两种现象,并设计出两种测量光栅常数的方法,在实验上进行验证.与传统的用最小偏转角测光栅常数的方法相比,本文重点分析了由判定最小偏转角位置偏差所带来的影响,并提出了对称旋转测量的方法来进一步减小误差. 相似文献
7.
New Perspectives for Old Clusters: Anderson–Evans Anions as Building Blocks of Large Polyoxometalate Frameworks in a Series of Heterometallic 3 d–4 f Species 下载免费PDF全文
Dr. Beñat Artetxe Dr. Santiago Reinoso Dr. Leire San Felices Prof. Luis Lezama Prof. Juan M. Gutiérrez‐Zorrilla Dr. Cristian Vicent Fadi Haso Prof. Tianbo Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4616-4625
A series of nine [Sb7W36O133Ln3M2(OAc)(H2O)8]17? heterometallic anions ( Ln3M2 ; Ln=La–Gd, M=Co; Ln=Ce, M=Ni and Zn) have been obtained by reacting 3 d metal disubstituted Krebs‐type tungstoantimonates(III) with early lanthanides. Their unique tetrameric structure contains a novel {MW9O33} capping unit formed by a planar {MW6O24} fragment to which three {WO2} groups are condensed to form a tungstate skeleton identical to that of a hypothetical trilacunary derivative of the ?‐Keggin cluster. It is shown, for the first time, that classical Anderson–Evans {MW6O24} anions can act as building blocks to construct purely inorganic large frameworks. Unprecedented reactivity in the outer ring of these disk‐shaped species is also revealed. The Ln3M2 anions possess chirality owing to a {Sb4O4} cluster being encapsulated in left‐ or right‐handed orientations. Their ability to self‐associate in blackberry‐type vesicles in solution has been assessed for the Ce3Co2 derivative. 相似文献
8.
A neutron powder diffraction study on lithium titanate Li2TiO3 was performed at low temperatures. The monoclinic β-phase has been found to be stable over the whole investigated range of temperatures (4 K–300 K). A smooth and nonlinear increase of the lattice parameters has been observed upon heating and correlated to the behavior of interatomic distances. Lithium diffusion pathways in Li2TiO3 were estimated theoretically on the basis of the obtained structural data using bond-valence modeling. Experimentally diffusion pathways were evaluated by analysis of the negative nuclear scattering densities at 1073 K, which were reconstructed using a maximum entropy method. Although the bond-valence mismatch map indicated a possible Li diffusion either in ab plane or along c direction, analysis of the experimental data revealed that Li migration is thermodynamically less feasible in latter case. 相似文献
9.
Back Cover: Understanding the Origins of Nucleophilic Hydride Reactivity of a Sodium Hydride–Iodide Composite (Chem. Eur. J. 21/2016) 下载免费PDF全文
10.