全文获取类型
收费全文 | 108362篇 |
免费 | 5094篇 |
国内免费 | 4887篇 |
专业分类
化学 | 46850篇 |
晶体学 | 1240篇 |
力学 | 8429篇 |
综合类 | 416篇 |
数学 | 35306篇 |
物理学 | 26102篇 |
出版年
2024年 | 66篇 |
2023年 | 435篇 |
2022年 | 873篇 |
2021年 | 997篇 |
2020年 | 1035篇 |
2019年 | 1115篇 |
2018年 | 11177篇 |
2017年 | 11010篇 |
2016年 | 7375篇 |
2015年 | 2307篇 |
2014年 | 2121篇 |
2013年 | 2669篇 |
2012年 | 6415篇 |
2011年 | 13161篇 |
2010年 | 7670篇 |
2009年 | 7986篇 |
2008年 | 8768篇 |
2007年 | 10646篇 |
2006年 | 2154篇 |
2005年 | 3043篇 |
2004年 | 2918篇 |
2003年 | 3133篇 |
2002年 | 2387篇 |
2001年 | 1208篇 |
2000年 | 1124篇 |
1999年 | 818篇 |
1998年 | 667篇 |
1997年 | 542篇 |
1996年 | 576篇 |
1995年 | 436篇 |
1994年 | 338篇 |
1993年 | 323篇 |
1992年 | 269篇 |
1991年 | 245篇 |
1990年 | 207篇 |
1989年 | 197篇 |
1988年 | 180篇 |
1987年 | 132篇 |
1986年 | 133篇 |
1985年 | 127篇 |
1984年 | 82篇 |
1983年 | 72篇 |
1982年 | 66篇 |
1981年 | 60篇 |
1980年 | 63篇 |
1979年 | 56篇 |
1978年 | 49篇 |
1914年 | 45篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
The first α‐diimine nickel(I) complex having a chloro bridge is reported. The centrosymmetric dinuclear structure of {[ArN?C(Me)C(Me)?NAr]NiCl}2[Ar?2,6?C6H3(i‐Pr)2] features two chelating α‐diimine ligands and two bridged chlorine atoms, so that a distorted tetrahedral N2Cl2 coordination geometry for nickel results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
4.
使用Monte Carlo模拟的方法得出了随机粗糙表面,在Kirchhoff近似的基础上,利用数值分析的方法分析了一维随机粗糙表面的散射特征,得出了一维随机粗糙表面散射分布曲线,我们还考虑了遮蔽效应的影响,并且讨论了Kirchhoff近似的有效性。 相似文献
5.
6.
Christiane Albrecht 《Analytical and bioanalytical chemistry》2008,390(5):1223-1224
7.
8.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
9.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献
10.
Dong‐Cheol Shin Yun‐Hi Kim Hong You Jae Gyu Jin Soon‐Ki Kwon 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5636-5646
A poly(p‐phenylenevinylene) (PPV) derivative containing a bulky (2,2‐diphenylvinyl)phenyl group in the side chain, EHDVP‐PPV, was synthesized by Gilch route. The reduced tolane‐bisbenzyl (TBB) defects, as well as the structure of the polymer, was confirmed by various spectroscopic methods. The intramolecular energy transfer from the (2,2‐diphenylvinyl)phenyl side group to the PPV backbone was studied by UV‐vis and photoluminescence (PL) of the obtained polymer and model compound. The polymer film showed maximum absorption and emission peaks at 454 and 546 nm, respectively, and high PL efficiency of 57%. A yellow electroluminescence (λmax = 548 nm) was obtained with intensities of 6479 cd/m2 when the light‐emitting diodes of ITO/PEDOT/EHDVP‐PPV/LiF/Al were fabricated. The maximum power efficiency of the devices was 0.729 lm/W with a turn‐on voltage of 3.6 V. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5636–5646, 2004 相似文献