全文获取类型
收费全文 | 54996篇 |
免费 | 12303篇 |
国内免费 | 3723篇 |
专业分类
化学 | 54586篇 |
晶体学 | 574篇 |
力学 | 1595篇 |
综合类 | 190篇 |
数学 | 4916篇 |
物理学 | 9161篇 |
出版年
2024年 | 56篇 |
2023年 | 399篇 |
2022年 | 730篇 |
2021年 | 982篇 |
2020年 | 1993篇 |
2019年 | 3264篇 |
2018年 | 1675篇 |
2017年 | 1259篇 |
2016年 | 4298篇 |
2015年 | 4389篇 |
2014年 | 4476篇 |
2013年 | 5431篇 |
2012年 | 4743篇 |
2011年 | 3998篇 |
2010年 | 4196篇 |
2009年 | 3993篇 |
2008年 | 3697篇 |
2007年 | 2994篇 |
2006年 | 2643篇 |
2005年 | 2635篇 |
2004年 | 2217篇 |
2003年 | 1882篇 |
2002年 | 2562篇 |
2001年 | 1760篇 |
2000年 | 1587篇 |
1999年 | 692篇 |
1998年 | 307篇 |
1997年 | 305篇 |
1996年 | 270篇 |
1995年 | 223篇 |
1994年 | 190篇 |
1993年 | 146篇 |
1992年 | 141篇 |
1991年 | 118篇 |
1990年 | 127篇 |
1989年 | 99篇 |
1988年 | 76篇 |
1987年 | 58篇 |
1986年 | 65篇 |
1985年 | 68篇 |
1984年 | 39篇 |
1983年 | 30篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1975年 | 13篇 |
1974年 | 8篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
891.
892.
Xiong Wen Ye Yu Ping Zhang Ling Bo Qu Li Qun Fan Bo Li 《中国化学快报》2007,18(11):1399-1402
Microwave irradiation was firstly attempted for the preparation of organic-based monoliths of poly(styrene-divinylbenzene- methacrylic acid), which single step in situ polymerization was carried out during 15 min. The colunm permeability, electrophoretic and chromatographac behaviors were comparatively evaluated using pressure-assisted CEC, GEC and low pressure-driven separation modes. The largest theoretical plates for the preparing column could be close to 18,0000 plates/m for thiourea in the mode of p-CEC. It provided a viable alternative to traditional initiation means for the perparation of monolithic capillary columns. 相似文献
893.
Densities of boldine + alcohol binary mixtures were measured over the whole accessible range of boldine compositions at temperatures from 283.15 to 333.15 K using an Anton-Paar digital vibrating glass tube densimeter. The binary systems studied include, as a solvent, seven normal alcohols from n-C1 to n-C6, n-C8, and isopropanol. The density of these systems has been found an increasing function of the boldine composition. A new methodology based on density data of solutions of solid solutes with normal alcohols is described in order to determine solid molar volume of pure solutes. This methodology was validated with pure solid naphthalene molar volumes data at 298.15 K, with an average uncertainty of 6%. 相似文献
894.
The performance of 17 exchange-correlation functionals for molecules containing heavy elements are numerically examined through four-component relativistic density DFT calculations. The examined functionals show the similar accuracy as they do for the molecules containing light elements only except for bond lengths. LDA and OP86 produce good results for bond lengths and frequencies but bad bond energies. Different functionals do not show much different performance for bond energies except LDA. BP86 and GP86 produce results with average accuracy while LYP does not perform well. Although encouraging results are obtained with functional B97GGA-1, other heavily parameterized and meta-GGA functionals do not produce impressive results. 相似文献
895.
the interaction of hemin with chloroquine,quinine and quinidine was investigated in 50% water-propylene glycol mixture at pH=9,8.1,7.4 and 6.8using a spectrophotometric method.The data could be well fitted into a model consistent with the formation of a 1:1 complex between the reacting partners.In addition,the results indicated that hemin complexed more strongly with quinidine than with chloroquine and quinine,and the binding constants were pH-dependent.Moreover,it was proved that the water-propylene glycol mixture is well suitable to the study of the systems containing hemin and quinolinebased drugs. 相似文献
896.
897.
Ingo Hartenbach Falk Lissner Tanja Nikelski Steffen F. Meier Helge Müller‐Bunz Thomas Schleid 《无机化学与普通化学杂志》2005,631(12):2377-2382
About Lanthanide Oxotantalates with the Formula MTaO4 (M = La – Nd, Sm – Lu) Besides being a by‐product of solid state syntheses in tantalum ampoules the lanthanide(III) oxotantalates of the formula MTaO4 can be easily prepared by sintering lanthanide sesquioxide M2O3 and tantalum(V) oxide Ta2O5 with sodium chloride as flux. Under these conditions two structure types emerge depending upon the M3+ cationic radius. For M = La – Pr the MTaO4‐type tantalates crystallize in the space group P21/c with lattice constants of a = 762(±1), b = 553(±4), c = 777(±4) pm, β = 101(±1)° and four formula units per unit cell. With M = Nd, Sm – Lu, the monoclinic cell dimensions (space group P2/c) shrink to the lattice constants like a = 516(±9), b = 551(±9), c = 534(±9) pm, β = 96.5(±0.3)° and there are only two formula units present. Both structures show a coordination sphere of eight oxygen atoms for the lanthanide trications shaped as distorted square antiprism for the structure with the larger lanthanides (in the following referred to as A‐type) and as trigonal dodecahedron for the structure with the smaller ones (called as B‐type in the following). The coordination environment about the Ta5+ cations can be described as a slightly distorted octahedron (CN = 6) for the A‐type structure of MTaO4 and a heavily distorted one (CN = 6) for the B‐type. The difference between the two types results from the interconnection of these [TaO6]7? octahedra. Whereas they are connected via four vertices to form corrugated layers according to parallel the bc‐plane in the A‐type, the octahedra of the B‐type MTaO4 structure share edges to built up zig‐zag chains along the c axis. 相似文献
898.
辣根过氧化物酶对心肌线粒体过氧化损伤的保护作用 总被引:1,自引:0,他引:1
以黄嘌呤氧化酶/次黄嘌呤自由基诱生系统建立了稳定的离体心肌线粒体的损伤模型,并应用此模型研究辣根过氧化物酶对心肌线粒体自由基氧化损伤的保护作用,结果表明,辣根过氧化物酶能抑制心肌线粒体中氧自由基的形成,降低膜脂的过氧水平,保护了线粒体膜酶活性,有效地防止自由基对线粒体结构和功能的损伤。 相似文献
899.
900.
Ga3(HPO3)4F4(H3DETA) is a new open-framework fluorinated gallium phosphite obtained by mild hydrothermal synthesis using diethylenetriamine as templated agent and characterized by single crystal X-ray diffraction, the powder X-ray diffraction, IR spectroscopy, TGA, ICP and elemental analyses. It crystallizes in the monoclinic space group C2/c, a=12.741(6) Å, b=12.068(6) Å, c=11.988(5) Å, β=94.902(8)o, V=1836.6(15) Å3, Z=4. The construction of 3D open-framework structure in the title compound may be viewed as the assembly of pentameric building units and HPO3 groups. The pentameric building unit is the first to be found, which lead to form the three types of channels along a-, b- and c-axes, respectively, in gallium phosphite. The triprotonated DETA cations are inserted within the 10-membered ring channels and interact with anions of the framework via hydrogen bonds. 相似文献