全文获取类型
收费全文 | 1824篇 |
免费 | 29篇 |
国内免费 | 7篇 |
专业分类
化学 | 1124篇 |
晶体学 | 13篇 |
力学 | 38篇 |
数学 | 206篇 |
物理学 | 479篇 |
出版年
2020年 | 14篇 |
2019年 | 11篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 17篇 |
2014年 | 31篇 |
2013年 | 56篇 |
2012年 | 60篇 |
2011年 | 80篇 |
2010年 | 51篇 |
2009年 | 41篇 |
2008年 | 83篇 |
2007年 | 85篇 |
2006年 | 77篇 |
2005年 | 65篇 |
2004年 | 47篇 |
2003年 | 62篇 |
2002年 | 64篇 |
2001年 | 50篇 |
2000年 | 44篇 |
1999年 | 39篇 |
1998年 | 32篇 |
1997年 | 37篇 |
1996年 | 28篇 |
1995年 | 36篇 |
1994年 | 38篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 34篇 |
1989年 | 22篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 24篇 |
1980年 | 35篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 18篇 |
1974年 | 21篇 |
1973年 | 16篇 |
1970年 | 10篇 |
1969年 | 13篇 |
1967年 | 10篇 |
排序方式: 共有1860条查询结果,搜索用时 15 毫秒
991.
Break-up events in ice shelves have been studied extensively during the last years. One popular assumption links disintegration events to surface melting of the ice shelf in conjunction with growing melt-water ponds, leading to hydro-fracture. As this explanation only holds during warm seasons [1], the possibility of frost wedging as forcing mechanism for autumn and winter break-up events is considered. Frost wedging can only occur if a closed ice lid seals the water inside the crack. Hence, the present study of frost wedging in a single crack uses ice lid thicknesses to evaluate the additional pressure on the crack faces. The investigation of the resulting stress intensity factor as a measure of crack criticality follows consequently. The results show that freezing water inside a crack can result in unstable crack growth of an initially stable water filled crack. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
Gross Craig Iwen Mark A. Kämmerer Lutz Volkmer Toni 《Advances in Computational Mathematics》2021,47(6):1-38
Advances in Computational Mathematics - We present a novel family of C1 quadrilateral finite elements, which define global C1 spaces over a general quadrilateral mesh with vertices of arbitrary... 相似文献
993.
Ming Cheng Chunyang Guo Michael L. Gross 《Angewandte Chemie (International ed. in English)》2020,59(15):5880-5889
Structural proteomics refers to large‐scale mapping of protein structures in order to understand the relationship between protein sequence, structure, and function. Chemical labeling, in combination with mass‐spectrometry (MS) analysis, have emerged as powerful tools to enable a broad range of biological applications in structural proteomics. The key to success is a biocompatible reagent that modifies a protein without affecting its high‐order structure. Fluorine, well‐known to exert profound effects on the physical and chemical properties of reagents, should have an impact on structural proteomics. In this Minireview, we describe several fluorine‐containing reagents that can be applied in structural proteomics. We organize their applications around four MS‐based techniques: a) affinity labeling, b) activity‐based protein profiling (ABPP), c) protein footprinting, and d) protein cross‐linking. Our aim is to provide an overview of the research, development, and application of fluorine‐containing reagents in protein structural studies. 相似文献
994.
995.
M. Sc. Yangyang Yang M. Sc. Jasmin Schießl B. Sc. Sirine Zallouz M. Sc. Verena Göker Dr. Jürgen Gross Dr. Matthias Rudolph Dr. Frank Rominger Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(41):9624-9628
A gold(I)-catalyzed cascade cyclization–alkynylation of allenoates using alkynyl bromide to generate β-alkynyl-γ-butenolides was investigated. Whereas alkynyl iodides afforded significant amounts of the homo-coupling of two lactone units, alkynyl bromides led to a selective reaction, and a broad functional group tolerance was observed. Under the optimized reaction conditions, it was possible to directly synthesize a large range of β-alkynyl-γ-butenolides in moderate to good yields without the need for any external oxidant. 相似文献
996.
997.
Peter Gross Prof. Dr. Henning A. Höppe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14366-14376
The crystal structure of biuret was elucidated by means of XRD analysis of single crystals grown through slow evaporation from a solution in ethanol. It crystallises in its own structure type in space group C2/c (a=15.4135(8) Å, b=6.6042(3) Å, c=9.3055(4) Å, Z=8). Biuret decomposition was studied in situ by means of temperature-programmed powder XRD and FTIR spectroscopy, to identify a co-crystalline biuret–cyanuric acid phase as a previously unrecognised reaction intermediate. Extensive thermogravimetric studies of varying crucible geometry, heating rate and initial sample mass reveal that the concentration of reactive gases at the interface to the condensed sample residues is a crucial parameter for the prevailing decomposition pathway. Taking these findings into consideration, a study on the optimisation of carbon nitride synthesis from urea on the gram scale, with standard solid-state laboratory techniques, is presented. Finally, a serendipitously encountered self-coating of the crucible inner walls by graphite during repeated synthetic cycles, which prove to be highly beneficial for the obtained yields, is reported. 相似文献
998.
999.
1000.
Single crystals of the high pressure phase of the 'spin-chain-compound' (VO) 2 P 2 O 7 could be grown from the melt, but crystal size is limited so far. As an alternative to melt growth, we suggest to prepare single crystals of the high pressure phase by a phase transformation of previously grown single crystals of the ambient pressure phase. 相似文献