全文获取类型
收费全文 | 2460篇 |
免费 | 54篇 |
国内免费 | 11篇 |
专业分类
化学 | 1442篇 |
晶体学 | 10篇 |
力学 | 84篇 |
数学 | 579篇 |
物理学 | 410篇 |
出版年
2021年 | 30篇 |
2020年 | 23篇 |
2019年 | 30篇 |
2016年 | 43篇 |
2015年 | 56篇 |
2014年 | 42篇 |
2013年 | 111篇 |
2012年 | 85篇 |
2011年 | 108篇 |
2010年 | 60篇 |
2009年 | 56篇 |
2008年 | 96篇 |
2007年 | 67篇 |
2006年 | 58篇 |
2005年 | 52篇 |
2004年 | 46篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 19篇 |
2000年 | 28篇 |
1999年 | 30篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 29篇 |
1994年 | 24篇 |
1993年 | 26篇 |
1992年 | 31篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1988年 | 25篇 |
1987年 | 30篇 |
1986年 | 27篇 |
1985年 | 46篇 |
1984年 | 33篇 |
1983年 | 22篇 |
1982年 | 24篇 |
1981年 | 34篇 |
1980年 | 38篇 |
1979年 | 35篇 |
1978年 | 24篇 |
1977年 | 40篇 |
1976年 | 32篇 |
1975年 | 23篇 |
1974年 | 21篇 |
1971年 | 20篇 |
1970年 | 16篇 |
1967年 | 17篇 |
1933年 | 20篇 |
1932年 | 16篇 |
1930年 | 21篇 |
排序方式: 共有2525条查询结果,搜索用时 133 毫秒
1.
Aysun apc Mlanie M. Lorion Hui Wang Nina Simon Maria Leidenberger Mariana C. BorgesSilva Diogo R. M. Moreira Yongping Zhu Yuqing Meng Jia Yun Chen Yew Mun Lee Oliver Friedrich Barbara Kappes Jigang Wang Lutz Ackermann Svetlana B. Tsogoeva 《Angewandte Chemie (International ed. in English)》2019,58(37):13161-13161
2.
3.
4.
Oxidative dehydrogenation (ODH) of n-octane was carried out over a vanadium–magnesium oxide catalyst in a continuous flow fixed bed reactor. The catalyst was characterized by ICP–OES, powder XRD and SEM. The catalytic tests were carried out at different gas hourly space velocities (GHSVs), viz. 4000, 6000, 8000, and 10,000 h?1. The best selectivity for octenes was obtained at the GHSV of 8000 h?1, while that for C8 aromatics was attained at the GHSV of 6000 h?1 at high temperatures (500 and 550 °C). The catalytic testing at the GHSV of 10,000 h?1 showed the lowest activity, while that at the GHSV of 4000 h?1 consistently showed the lowest ODH selectivity. Generally, the best ODH performance was obtained by the catalytic testing at the GHSVs of 6000 and 8000 h?1. No phasic changes were observed after the catalytic testing. 相似文献
5.
Back Cover: Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes (Chem. Eur. J. 33/2015) 下载免费PDF全文
6.
Partial Oxidation as a Rational Approach to Kinetic Control in Bioinspired Magnetite Synthesis 下载免费PDF全文
Dr. Cem L. Altan Jos J. M. Lenders Paul H. H. Bomans Prof. Gijsbertus de With Dr. Heiner Friedrich Dr. Seyda Bucak Prof. Nico A. J. M. Sommerdijk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6150-6156
Biological systems show impressive control over the shape, size and organization of mineral structures, which often leads to advanced physical properties that are tuned to the function of these materials. Such control is also found in magnetotactic bacteria, which produce—in aqueous medium and at room temperature—magnetite nanoparticles with precisely controlled morphologies and sizes that are generally only accessible in synthetic systems with the use of organic solvents and/or the use of high‐temperature methods. The synthesis of magnetite under biomimetic conditions, that is, in water and at room temperature and using polymeric additives as control agents, is of interest as a green production method for magnetic nanoparticles. Inspired by the process of magnetite biomineralization, a rational approach is taken by the use of a solid precursor for the synthesis of magnetite nanoparticles. The conversion of a ferrous hydroxide precursor, which we demonstrate with cryo‐TEM and low‐dose electron diffraction, is used to achieve control over the solution supersaturation such that crystal growth can be regulated through the interaction with poly‐(α,β)‐dl ‐aspartic acid, a soluble, negatively charged polymer. In this way, stable suspensions of nanocrystals are achieved that show remanence and coercivity at the size limit of superparamagnetism, and which are able to align their magnetic moments forming strings in solution as is demonstrated by cryo‐electron tomography. 相似文献
7.
Kinetics and Catalysis - Boron and barium were employed as dopants for the VMgO system. The catalysts were characterized by ICP-OES, BET, IR, powder XRD, EDX, TPR-H2, TPD-NH3, XPS, and 51V MAS NMR.... 相似文献
8.
9.
Jan Maier Marian Deutsch Dr. Julia Merz Prof. Dr. Qing Ye Oliver Diamond Maja-Tessa Schilling Dr. Alexandra Friedrich Prof. Dr. Bernd Engels Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15989-16000
We have investigated the cannibalistic self-trapping reaction of an ortho-benzyne derivative generated from 1,11-bis(p-tolyl)undeca-1,3,8,10-tetrayne in an HDDA reaction. Without adding any specific trapping agent, the highly reactive benzyne is trapped by another bisdiyne molecule in at least three different modes. We have isolated and characterized the resulting products and performed high-level calculations concerning the reaction mechanism. During the cannibalistic self-trapping process, either a C≡C triple bond or an sp–sp3 C−C single bond is cleaved. Up to seven rings and nine C−C bonds are formed starting from two 1,11-bis(p-tolyl)undeca-1,3,8,10-tetrayne molecules. Our experiments and calculations provide considerable insight into the variety of reaction pathways which the ortho-benzyne derivative, generated from a bisdiyne, can take when reacting with another bisdiyne molecule. 相似文献
10.