全文获取类型
收费全文 | 4025篇 |
免费 | 141篇 |
国内免费 | 12篇 |
专业分类
化学 | 2682篇 |
晶体学 | 17篇 |
力学 | 53篇 |
数学 | 624篇 |
物理学 | 802篇 |
出版年
2022年 | 30篇 |
2021年 | 47篇 |
2020年 | 78篇 |
2019年 | 63篇 |
2018年 | 31篇 |
2017年 | 29篇 |
2016年 | 96篇 |
2015年 | 80篇 |
2014年 | 68篇 |
2013年 | 107篇 |
2012年 | 183篇 |
2011年 | 188篇 |
2010年 | 94篇 |
2009年 | 119篇 |
2008年 | 193篇 |
2007年 | 174篇 |
2006年 | 161篇 |
2005年 | 133篇 |
2004年 | 130篇 |
2003年 | 127篇 |
2002年 | 125篇 |
2001年 | 89篇 |
2000年 | 97篇 |
1999年 | 78篇 |
1998年 | 70篇 |
1997年 | 82篇 |
1996年 | 63篇 |
1995年 | 56篇 |
1994年 | 83篇 |
1993年 | 67篇 |
1992年 | 59篇 |
1991年 | 59篇 |
1990年 | 51篇 |
1989年 | 42篇 |
1988年 | 59篇 |
1987年 | 60篇 |
1986年 | 46篇 |
1985年 | 60篇 |
1984年 | 73篇 |
1983年 | 47篇 |
1982年 | 61篇 |
1981年 | 60篇 |
1980年 | 52篇 |
1979年 | 44篇 |
1978年 | 40篇 |
1977年 | 37篇 |
1976年 | 54篇 |
1975年 | 31篇 |
1974年 | 25篇 |
1973年 | 30篇 |
排序方式: 共有4178条查询结果,搜索用时 31 毫秒
11.
Peter Karduck Norbert Ammann Hans Günter Esser Jörg Winter 《Fresenius' Journal of Analytical Chemistry》1991,341(5-6):315-319
Summary The first wall of the fusion device TEXTOR at the Forschungszentrum Jülich has been coated in situ with an amorphous hydrogen rich carbon/boron film (a-C/B:H) which reduces plasma impurities caused by the plasma surface interaction. The results of the coating process of the 35 m2 large inner wall surface have been controlled by a recently developed modification of the quantitative electron probe microanalysis, which has been applied to 12 samples from specified positions inside the tokamak. The quantification itself is based on a Monte Carlo simulation of electron trajectories providing very accurate results for X-ray intensities emitted by elements present in the electron bombarded sample. The Monte Carlo results are used in the present work to calibrate the measured X-ray intensities emitted by boron and carbon from the a-C/B:H layers deposited on pure silicon substrates. As a result the total deposited mass of the layer per area unit as well as the composition of the layers (except hydrogen) could be determined very accurately. The relative errors were less than 7%. The limit of detectability were found to be in the range of one monolayer for boron as well as for carbon. 相似文献
12.
13.
Norbert Poschadel 《Mathematische Semesterberichte》2002,49(1):45-54
Zusammenfassung. Eine Abbildung zwischen metrischen R?umen hei?t abstandsvertr?glich, wenn der Abstand der Bilder zweier Punkte nur vom Abstand der Punkte selbst abh?ngt. Wir zeigen, dass eine Abbildung genau dann abstandsvertr?glich ist, wenn der Cauchyschen Funktionalgleichung genügt, also ein Endomorphismus der Gruppe ist. Ein entsprechendes Resultat gilt auch für die abstandsvertr?glichen Abbildungen des Kreises (mit der Multiplikation komplexer Zahlen als Gruppenverknüpfung). Damit kann man sowohl alle messbaren abstandsvertr?glichen Abbildungen von bzw. in sich angeben, als auch einen Nachweis für die Existenz nichtmessbarer abstandsvertr?glicher Abbildungen auf und erbringen.
Eingegangen am 20. Juni 2001 / Angenommen am 13. September 2001 相似文献
14.
15.
Stefan Pitsch Sebastian Wendeborn Ramanarayanan Krishnamurthy Armin Holzner Mark Minton Martin Bolli Christian Miculca Norbert Windhab Ronald Micura Michael Stanek Bernhard Jaun Albert Eschenmoser 《Helvetica chimica acta》2003,86(12):4270-4363
Pyranosyl‐RNA (‘p‐RNA’ ) is an oligonucleotide system isomeric to natural RNA and composed of the very same building blocks as RNA. Its generational, chemical, and informational properties are deemed to be those of an alternative nucleic acid system that could have been a candidate in Nature's evolutionary choice of the molecular basis of genetic function. We consider the study of the chemistry of p‐RNA as etiologically relevant in the sense that knowledge of its structural, chemical, and informational properties on the chemical level offers both a perspective and reference points for the recognition of specific structural assets of the RNA structure that made it the (supposedly) superior system among possible alternatives and, therefore, the system that became part of biology as we know it today. The paper describes the chemical synthesis of β‐d‐ (and L )‐ribopyranosyl‐(4′→2′)‐oligonucleotide sequences, presents a resume of their structural and chemical properties, and cautiously discusses what we may and may not have learned from the pyranosyl isomer of RNA with respect to the conundrum of RNA's origin. 相似文献
16.
17.
18.
The three-loop form factors in massless QCD can be expressed as a linear combination of master integrals. Besides a number of master integrals which factorise into products of one-loop and two-loop integrals, one finds 16 genuine three-loop integrals. Of these, six have the form of a bubble insertion inside a one-loop or two-loop vertex integral. We compute all master integrals with these insertion topologies. 相似文献
19.
20.
A simple and fast HPLC method for the determination of glycols is described. It is characterized by a reversed-phase separation using water as eluent and a refractive index detection. The method was applied to investigate the biodegradation of glycols in a laboratory activated sludge plant and to determine the content of glycols or alcohols in detergents. The detection limit is 4 mg/l ethylene glycol or propylene glycol in an aqueous sample. 相似文献