全文获取类型
收费全文 | 4161篇 |
免费 | 92篇 |
国内免费 | 7篇 |
专业分类
化学 | 2823篇 |
晶体学 | 17篇 |
力学 | 104篇 |
数学 | 287篇 |
物理学 | 1029篇 |
出版年
2021年 | 28篇 |
2020年 | 27篇 |
2019年 | 48篇 |
2016年 | 68篇 |
2015年 | 55篇 |
2014年 | 85篇 |
2013年 | 161篇 |
2012年 | 107篇 |
2011年 | 162篇 |
2010年 | 109篇 |
2009年 | 91篇 |
2008年 | 149篇 |
2007年 | 131篇 |
2006年 | 138篇 |
2005年 | 132篇 |
2004年 | 118篇 |
2003年 | 96篇 |
2002年 | 70篇 |
2001年 | 63篇 |
2000年 | 58篇 |
1999年 | 45篇 |
1998年 | 40篇 |
1997年 | 63篇 |
1996年 | 72篇 |
1995年 | 76篇 |
1994年 | 65篇 |
1993年 | 94篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 50篇 |
1989年 | 56篇 |
1988年 | 35篇 |
1987年 | 54篇 |
1986年 | 53篇 |
1985年 | 55篇 |
1984年 | 56篇 |
1983年 | 43篇 |
1982年 | 46篇 |
1981年 | 56篇 |
1980年 | 62篇 |
1979年 | 44篇 |
1978年 | 60篇 |
1977年 | 37篇 |
1976年 | 68篇 |
1975年 | 62篇 |
1974年 | 51篇 |
1973年 | 61篇 |
1972年 | 34篇 |
1969年 | 28篇 |
1967年 | 44篇 |
排序方式: 共有4260条查询结果,搜索用时 296 毫秒
51.
Johanna Flock Dr. Amra Suljanovic Dr. Ana Torvisco Dr. Wolfgang Schoefberger Birgit Gerke Prof. Dr. Rainer Pöttgen Prof. Dr. Roland C. Fischer Prof. Dr. Michaela Flock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15504-15517
Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition‐metal chemistry. However, the stabilization of main‐group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6‐[ArNH‐CH2]2(NC5H3) (Ar=C6H3‐2,6‐iPr2)) with Sn[N(SiMe3)2]2 produces the DIMPYSn complex (DIMPY=(2,6‐[ArN?CH]2(NC5H3)) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low‐valent SnII complexes, including a [DIMPYSnIICl]+[SnCl3]? ion pair, a bisstannylene DAMPY{SnII[N(SiMe3)2]2}2, and the enamine complex MeDIMPYSnII, were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and 119Sn Mössbauer spectroscopy. 相似文献
52.
Kai Zhang Steffen Fischer Andreas Geissler Erica Brendler Kathrin Gebauer 《Cellulose (London, England)》2013,20(4):2069-2080
Synthesis of cellulose sulfates (CSs) and carboxyl cellulose sulfates (COCSs) with regioselectively or regiospecifically distributed functional groups within anhydroglucose units was reported. CS with regioselectively distributed sulfate groups at 2,3-O- or 2,6-O-position were homogeneously synthesized and cellulose trifluoroacetate (CTFA) was used as intermediates. The trifluoroacetyl groups were detected primarily at 6-O-position and their distributions could be altered by changing the amount of trifluoroacetyl anhydride (TFAA). Various sulfating agents were used for further homogeneous sulfation of CTFA. The total degree of sulfation (DSS) and the distribution of sulfate groups within the repeating units were affected by the amount of TFAA, the type and amount of sulfating agents. Subsequent homogenous 4-acetamide-TEMPO or TEMPO-mediated oxidation of CS led to COCS with carboxyl groups regiospecifically distributed at C6 position, which may be interesting structural mimics for natural occurring heparin. 相似文献
53.
54.
55.
56.
57.
58.
Bei Zhou Yousef Heider Andreas Blaeser Stefan Raith Horst Fischer Bernd Markert 《PAMM》2016,16(1):117-118
The aim of this work is to numerically simulate the gelation of a crosslinking polymer, which is a very complex process involving chemical reactions and phase transitions from a viscous fluid to a viscoelastic solid. A phenomenological model is proposed to simulate the gelation process of agarose droplets, considering the thermal boundary conditions. The numerical model is implemented using the finite element package FlexPDE. The temperature- and time-dependent degree of gelation and the deformation of the droplets during the gelation process are investigated. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
59.
Weijin Li Song Xue Sebastian Watzele Shujin Hou Johannes Fichtner A. Lisa Semrau Liujiang Zhou Alexander Welle Aliaksandr S. Bandarenka Roland A. Fischer 《Angewandte Chemie (International ed. in English)》2020,59(14):5837-5843
Metal–organic frameworks (MOFs) and their derivatives are considered as promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are important for many energy provision technologies, such as electrolyzers, fuel cells and some types of advanced batteries. In this work, a “strain modulation” approach has been applied through the use of surface‐mounted NiFe‐MOFs in order to design an advanced bifunctional ORR/OER electrocatalyst. The material exhibits an excellent OER activity in alkaline media, reaching an industrially relevant current density of 200 mA cm?2 at an overpotential of only ≈210 mV. It demonstrates operational long‐term stability even at a high current density of 500 mA cm?2 and exhibits the so far narrowest “overpotential window” ΔEORR‐OER of 0.69 V in 0.1 m KOH with a mass loading being two orders of magnitude lower than that of benchmark electrocatalysts. 相似文献
60.
Márton Zwillinger Dr. Post Sai Reddy Dr. Barbara Wicher Dr. Pradeep K. Mandal Dr. Márton Csékei Dr. Lucile Fischer Dr. András Kotschy Prof. Dr. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17366-17370
Helically folded aromatic oligoamide foldamers have a size and geometrical parameters very distinct from those of α-helices and are not obvious candidates for α-helix mimicry. Nevertheless, they offer multiple sites for attaching side chains. It was found that some arrays of side chains at the surface of an aromatic helix make it possible to mimic extended α-helical surfaces. Synthetic methods were developed to produce quinoline monomers suitably functionalized for solid phase synthesis. A dodecamer was prepared. Its crystal structure validated the initial design and showed helix bundling involving the α-helix-like interface. These results open up new uses of aromatic helices to recognize protein surfaces and to program helix bundling in water. 相似文献