全文获取类型
收费全文 | 25861篇 |
免费 | 4566篇 |
国内免费 | 4173篇 |
专业分类
化学 | 19961篇 |
晶体学 | 403篇 |
力学 | 1385篇 |
综合类 | 359篇 |
数学 | 3005篇 |
物理学 | 9487篇 |
出版年
2024年 | 45篇 |
2023年 | 454篇 |
2022年 | 639篇 |
2021年 | 878篇 |
2020年 | 1058篇 |
2019年 | 1080篇 |
2018年 | 893篇 |
2017年 | 941篇 |
2016年 | 1296篇 |
2015年 | 1338篇 |
2014年 | 1580篇 |
2013年 | 2024篇 |
2012年 | 2383篇 |
2011年 | 2332篇 |
2010年 | 1888篇 |
2009年 | 1733篇 |
2008年 | 1965篇 |
2007年 | 1647篇 |
2006年 | 1609篇 |
2005年 | 1304篇 |
2004年 | 1057篇 |
2003年 | 930篇 |
2002年 | 1004篇 |
2001年 | 881篇 |
2000年 | 638篇 |
1999年 | 537篇 |
1998年 | 420篇 |
1997年 | 301篇 |
1996年 | 279篇 |
1995年 | 231篇 |
1994年 | 192篇 |
1993年 | 150篇 |
1992年 | 146篇 |
1991年 | 150篇 |
1990年 | 103篇 |
1989年 | 80篇 |
1988年 | 70篇 |
1987年 | 50篇 |
1986年 | 51篇 |
1985年 | 39篇 |
1984年 | 30篇 |
1983年 | 30篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1973年 | 8篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
71.
文章简要地叙述了法国著名物理学家路易·奈尔的成长历程与生平业绩,其中包括他在磁学领域的诸多重大贡献、成功地创立和领导了一个富有成就的科学研究团体以及他堪称为一位出色的科技开发企业家的风范. 相似文献
72.
73.
Nickel complexes 1–4 ligated with 2,9-disubstituted-1,10-phenanthroline were synthesized and characterized by FT-IR spectra and elemental analysis.
The molecular structure of complex 2 was confirmed by X-ray crystal diffraction analysis. Activated with methylaluminoxane (MAO), those complexes showed moderate
activities for ethylene oligomerization.
Published in Kinetika i Kataliz, 2007, Vol. 48, No. 5, pp. 710–714.
This article was submitted by the authors in English. 相似文献
74.
75.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
76.
77.
采用高温热解法,以乙二胺为前驱液,在沉积有铁催化剂的p型硅(111)基底上制备出了定向生长的CNx纳米管.利用扫描电子显微镜、高分辨率透射电子显微镜和拉曼光谱对CNx纳米管进行了形貌观察和表征.CNx纳米管的高度在20?μm左右,直径在50—100nm之间,具有明显的“竹节状”结构,结晶有序度较差.对CNx纳米管薄膜进行低场致发射性能测试:外加电场为1.4V/μm,观察到20?μA /cm2发射电流,外电场升至2.54V/μm时发射电流达到1.280mA/cm2,在较高外电场下,没有发现电流“饱和”.这比
关键词:
CNx纳米管
高温热解
“竹节状”结构
场致发射 相似文献
78.
We investigate some topological properties of a normal functorH introduced earlier by Radul which is some functorial compactification of the Hartman-Mycielski construction HM. We prove
that the pair (H X, HMY) is homeomorphic to the pair (Q, σ) for each nondegenerated metrizable compactumX and each denseσ-compact subsetY. 相似文献
79.
Jie Da Thieo E. Hogen‐Esch 《Journal of polymer science. Part A, Polymer chemistry》2004,42(2):360-373
The synthesis is reported of copolymers of N,N‐dimethylacrylamide (DMA) and methacrylates containing 2,2′‐dihydroperfluorodecanoyl (RF) groups separated from the methacrylate by long polyethylene glycol (PEG) tether groups (between 1000 and 14,000 Da). At concentrations of between 1 and 8 wt % the copolymers with macromonomer contents of 1 mol % or less give gels in organic solvents such as dioxane, THF, or methanol, as well as in water. Given the low molecular weights, this indicates very efficient association of very low numbers of RF groups. Association and gel formation is enormously enhanced in the presence of longer PEG tethers. This is consistent with smaller poly(N,N,‐dimethylacrylamide) (PDMA) intermolecular excluded volume effects that are mediated by the longer PEG tethers and possibly by the incompatibility of PEG and PDMA that may lead to the formation of PEG microdomains. This increases the local concentrations of the RF groups in the PEO domains that are not diluted by the PDMA chains, as would be the case in the absence of PEG tethers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 360–373, 2004 相似文献
80.
Veličković Jelena Đ. Andrić Deana Roglić Goran Tešic Živoslav Lj. Milojković-Opsenica Dušanka M. 《平面色谱法杂志一现代薄层色谱法》2004,17(4):255-260
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of fourteen 1-arylpiperazine derivatives has been studied by thin-layer chromatography on both silica... 相似文献