全文获取类型
收费全文 | 3574篇 |
免费 | 834篇 |
国内免费 | 276篇 |
专业分类
化学 | 1606篇 |
晶体学 | 33篇 |
力学 | 30篇 |
综合类 | 16篇 |
数学 | 122篇 |
物理学 | 2877篇 |
出版年
2024年 | 11篇 |
2023年 | 43篇 |
2022年 | 81篇 |
2021年 | 110篇 |
2020年 | 141篇 |
2019年 | 120篇 |
2018年 | 111篇 |
2017年 | 99篇 |
2016年 | 132篇 |
2015年 | 139篇 |
2014年 | 183篇 |
2013年 | 267篇 |
2012年 | 225篇 |
2011年 | 257篇 |
2010年 | 206篇 |
2009年 | 259篇 |
2008年 | 202篇 |
2007年 | 230篇 |
2006年 | 217篇 |
2005年 | 173篇 |
2004年 | 157篇 |
2003年 | 163篇 |
2002年 | 183篇 |
2001年 | 147篇 |
2000年 | 158篇 |
1999年 | 111篇 |
1998年 | 122篇 |
1997年 | 44篇 |
1996年 | 39篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 34篇 |
1992年 | 32篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有4684条查询结果,搜索用时 46 毫秒
101.
State Miao Ming-Ming Liao Dai-Zheng Jiang Zong-Hui Cheng Peng Wang Geng-Lin 《中国化学》1996,14(4):326-330
Four new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)2]2[Cu(opba)]}(ClO4)2, where opba denotes o-phenylenebis(oxamato) and L stands for 1,10-phenanthroline(phen) (1), 5-nitro-l,10-phenanthroline(NO2-phen) (2), 2,2′-bipyridyl(bpy) (S) and 4,4′-dimethyl-2,2′-bipyridyl(Me2bpy) (4). The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(opba)]}(ClO4)23H2O has been studied in the 4–300 K range, giving the exchange integral J—109 cm?1. The HMT vs. T plot exhibits a minimum at about 100 K, characteristic of this kind of coupled polymetallic complex with an irregular spin-state structure. 相似文献
102.
In this paper, we obtain considerable spin-orbit (SO) parameters in AlxGa1-xN/GaN quantum wells (QWs) with sheet carrier concentration Ns=120×1011/cm2 . With increasing Al content (x) of the barrier, the SO parameters increase as a whole, and the two major contributions are found to be the decrease of the expansion region of the envelope functions and the increase of the polarized electric field in the well. Compared with the Rashba parameters for the first two subbands, the intersubband SO parameter is a bit smaller and varies more slowly with x. The results indicate the SO parameters, especially the Rashba parameters can be engineered by the Al composition of the barrier, which may be helpful to the spin manipulation of III-nitride low-dimensional heterostructures. 相似文献
103.
Dr. Athanassios K. Boudalis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(24):7022-7042
Spin triangles, that is, triangular complexes of half-integer spins, are the oldest molecular nanomagnets (MNMs). Their magnetic properties have been studied long before molecular magnetism was delineated as a research field. This Review presents the history of their study, with references to the parallel development of new experimental investigations and new theoretical ideas used for their interpretation. It then presents an indicative list of spin-triangle families to illustrate their chemical diversity. Finally, it makes reference to recent developments in terms of theoretical ideas and new phenomena, as well as to the relevance of spin triangles to spintronic devices and new physics. 相似文献
104.
Daniel T. W. Toolan Richard Hodgkinson Jonathan R. Howse 《Journal of Polymer Science.Polymer Physics》2014,52(1):17-25
Spin‐coated polymer blends possess a rich variety of accessible non‐equilibrium morphologies, formed through a process of phase separation and self‐assembly, the complexities of which remain incompletely understood. The technique of stroboscopic microscopy has now been developed to allow direct observations of microscopic and mesoscopic morphological development during spin‐coating and has afforded unequivocal information regarding morphological development. The technique so far has three modes of operation providing information on topographical, compositional, and crystal development. In this review, we look at the technique's development, its applications and comment on the future potential for this technique. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 17–25 相似文献
105.
106.
107.
《应用有机金属化学》2017,31(7)
The reaction of bromazepam (7‐bromo‐1,3‐dihydro‐5‐(2‐pyridyl)‐2H ‐1,4‐benzodiazepin‐2‐one, BZM) with Cr(III) ( 1 ), Fe(III) ( 2 ) and Ru(III) ( 3 ) salts gives complexes of the type [M(BZM)3]⋅3X (X = Cl or NO3). Structural characterization was extensively carried out using various analytical and spectral tools such as infrared, 1H NMR and UV–visible spectroscopies and magnetic, conductance, elemental and thermal analyses. BZM is a bidentate ligand and interacts with the metal ions via the pyridine and benzodiazepin‐2‐one nitrogen atoms. The magnetic and electronic properties of 2 and 3 are consistent with low‐spin octahedral complexes. The three BZM molecules are non‐isoenergetically coordinated to the metal ions and this is reflected in the values of the second‐order interaction energy. The antibacterial activity was studied using Staphylococcus aureus and Escherichia coli . Coordination of BZM to Cr(III) or Ru(III) ions leads to a marked increase in toxicity with respect to the inactive Fe(III) complex 2 . 相似文献
108.
109.
HUANG HouBing MA XingQiao YUE Tao XIAO ZhiHua SHI SanQiang & CHEN LongQing 《中国科学:物理学 力学 天文学(英文版)》2011,(7)
The current-induced magnetic switching is studied in Co/Cu/Co nanopillar with an in-plane magnetization traversed under the perpendicular-to-plane external field.Magnetization switching is found to take place when the current density exceeds a threshold.By analyzing precessional trajectories,evolutions of domain walls and magnetization switching times under the perpendicular magnetic field,there are two different magnetization switching modes:nucleation and domain wall motion reversal;uniform magnetization ... 相似文献
110.
Yury Yu. Rusakov Irina L. Rusakova Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2014,52(5):214-221
Four‐component relativistic calculations of 77Se–13C spin–spin coupling constants have been performed in the series of selenium heterocycles and their parent open‐chain selenides. It has been found that relativistic effects play an essential role in the selenium–carbon coupling mechanism and could result in a contribution of as much as 15–25% of the total values of the one‐bond selenium–carbon spin‐spin coupling constants. In the overall contribution of the relativistic effects to the total values of 1J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin‐orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second‐order polarization propagator approach (CC2) with the four‐component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of 1J(Se,C). Solvent effects in the values of 1J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2–78.4) are next to negligible decreasing negative 1J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of 77Se–13C spin‐spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1–0.2‐Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献