全文获取类型
收费全文 | 14218篇 |
免费 | 1770篇 |
国内免费 | 1135篇 |
专业分类
化学 | 7863篇 |
晶体学 | 577篇 |
力学 | 1012篇 |
综合类 | 93篇 |
数学 | 414篇 |
物理学 | 7164篇 |
出版年
2024年 | 12篇 |
2023年 | 107篇 |
2022年 | 245篇 |
2021年 | 269篇 |
2020年 | 302篇 |
2019年 | 315篇 |
2018年 | 336篇 |
2017年 | 345篇 |
2016年 | 555篇 |
2015年 | 515篇 |
2014年 | 676篇 |
2013年 | 1206篇 |
2012年 | 739篇 |
2011年 | 988篇 |
2010年 | 839篇 |
2009年 | 953篇 |
2008年 | 928篇 |
2007年 | 1072篇 |
2006年 | 993篇 |
2005年 | 776篇 |
2004年 | 794篇 |
2003年 | 661篇 |
2002年 | 559篇 |
2001年 | 440篇 |
2000年 | 392篇 |
1999年 | 347篇 |
1998年 | 321篇 |
1997年 | 234篇 |
1996年 | 197篇 |
1995年 | 201篇 |
1994年 | 188篇 |
1993年 | 105篇 |
1992年 | 94篇 |
1991年 | 72篇 |
1990年 | 52篇 |
1989年 | 56篇 |
1988年 | 52篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 7篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 69 毫秒
1.
《Mendeleev Communications》2022,32(1):105-108
A mixed-metal 1D coordination polymer [CaCu(HBTC)2(H2O)8]n (where H3BTC – benzene-1,3,5-tric arboxylic acid) was obtained in a solvothermal synthesis of a well-known copper-containing metal–organic framework [Cu3(BTC)2(H2O)3]n (HKUST-1) in autoclaves 3D-printed from commercial polypropylene. This material was a source of calcium ions, apparently, leaking from a colorant (calcium carbonate) promoted by glacial acetic acid as a modulator used to produce large single crystals of HKUST-1. This finding was confirmed by elemental analysis and a model experiment that resulted in a new calcium-based 1D coordination polymer [Ca(H2BTC)2(H2O)5]n under the same solvothermal conditions with no copper or calcium salts put into a 3D-printed autoclave. 相似文献
2.
3.
4.
Based on the vectorial Rayleigh–Sommerfeld diffraction integrals, analytical expressions for the transversal and axial field distribution of plane waves propagating through a thin lens followed by a small circular aperture are derived and used to study the focusing and diffraction properties of plane waves. Some special cases of our general result are discussed, and illustrative numerical calculation results are given. It is found that the vectorial nonparaxial approach should be applied if the aperture dimension is comparable with the wavelength or the focusing is strong. 相似文献
5.
Shougo Higashi 《Surface science》2006,600(3):591-597
We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi4 clusters are arranged in the top Cu layer instead of MgBi4. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment. 相似文献
6.
7.
8.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(9):2399-2399
9.
Diffraction in electron stimulated desorption has revealed a propensity for Cl+ desorption from rest atom vs. adatom areas and unfaulted vs. faulted zones of Cl-terminated Si(1 1 1)-(7 × 7) surfaces. We associate the 15 eV ± 1 eV threshold with ionization of Si-Cl σ-bonding surface states and formation of screened two-hole states with Si 3s character. Similar specificity is observed from A and B reconstructions. This can be due to reduced screening in unfaulted regions and increased hole localization in Si back-bonds within faulted regions. 相似文献
10.
A new unified electroweak model is proposed in this paper. In this unified electroweak model, Higgsmechanism is not used, so no Higgs particle exists in the model. In order to keep the masses of intermediate gaugebosons non-zero, two sets of gauge fields will be introduced. In order to introduce symmetry breaking and to help tointroduce the masses of all fields, a vacuum potential is needed. Except for those terms concerning Higgs particle, thefundamental dynamical properties of this model are similar to those of the standard model. And in a proper limit, thismodel will approximately return to the standard model. The purpose of this paper is not to say that the Higgs particledoes not exist in Nature, it is only to prove that, without a Higgs particle, we can also set up a unified electroweak modelwhich is consistent with present experiments. 相似文献