全文获取类型
收费全文 | 2835篇 |
免费 | 122篇 |
国内免费 | 7篇 |
专业分类
化学 | 2233篇 |
晶体学 | 7篇 |
力学 | 42篇 |
数学 | 397篇 |
物理学 | 285篇 |
出版年
2023年 | 22篇 |
2022年 | 59篇 |
2021年 | 112篇 |
2020年 | 79篇 |
2019年 | 81篇 |
2018年 | 38篇 |
2017年 | 47篇 |
2016年 | 114篇 |
2015年 | 107篇 |
2014年 | 111篇 |
2013年 | 175篇 |
2012年 | 210篇 |
2011年 | 214篇 |
2010年 | 161篇 |
2009年 | 120篇 |
2008年 | 177篇 |
2007年 | 161篇 |
2006年 | 143篇 |
2005年 | 143篇 |
2004年 | 132篇 |
2003年 | 107篇 |
2002年 | 100篇 |
2001年 | 34篇 |
2000年 | 42篇 |
1999年 | 31篇 |
1998年 | 25篇 |
1997年 | 25篇 |
1996年 | 32篇 |
1995年 | 21篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 21篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有2964条查询结果,搜索用时 15 毫秒
181.
Monika Schuster Claudia Turecek Helga Lichtenegger Robert Liska 《Applied Surface Science》2007,254(4):1131-1134
Continuously increasing life expectancy results in a rising number of bone diseases and fractures. Replacements from natural sources are not only limited in their availability, they also have some serious disadvantages such as possible immunological reactions or transmission of diseases. New synthetic biodegradable materials based on photopolymers could be an alternative solution. In these investigations an acrylate-based monomer formulation has been developed, consisting of a biodegradable basis monomer which is derived from gelatin, different reactive diluents, an appropriate photoinitiator and filler materials. For the three-dimensional shaping process stereolithography is the method of choice because of its capability to produce cellular structures with high resolutions. 相似文献
182.
183.
184.
185.
186.
Noe Oña Antonio Romero Carmen Assiego Claudia Bello Pierre Vogel M. Soledad Pino-González 《Tetrahedron: Asymmetry》2010,21(17):2092-2099
An approach to the synthesis of polyhydroxyazepane derivatives from sugar-based epoxyamides or epoxyalcohols, in which the total regioselective epoxide opening by nitrogen nucleophiles is the key step, is described. Thus, novel polyhydroxyazepane carboxamides and aminomethyl polyhydroxyazepanes, with potential pharmacological interest, are synthesized from diacetone d-mannose. Configurational assignments of the obtained products were determined. 相似文献
187.
Elisabeth Eidenberger Erich Stergar Harald Leitner Peter Staron Jürgen Spitaler Claudia Ambrosch-Draxl Helmut Clemens 《Applied Physics A: Materials Science & Processing》2009,97(2):331-340
Atom probe tomography (APT) measurements were conducted to analyze nm-sized precipitates in a Fe-25 m% Co-15 m% Mo model alloy.
Calculation of isoconcentration surfaces and application of cluster-search algorithms yielded the chemical compositions of
matrix and precipitates. Small-angle neutron scattering (SANS) was performed in order to calculate the ratio of magnetic to
nuclear scattering. This so-called A-ratio was compared with values calculated from the chemical information derived from the atom probe data. For this, the magnetism
of the precipitates has to be taken into account. Ab-initio studies have been carried out to determine the magnetic moment
of the precipitate phase. The results show that the extremely fine precipitates are ferromagnetic and exhibit near-equilibrium
composition. In the very early stage of decomposition, however, the composition is different from near-equilibrium. The influences
of the magnetism of the precipitates as well as of artifacts from atom probe measurements on the obtained results are discussed. 相似文献
188.
Claudia Strobel Adriano A. Torrano Rudolf Herrmann Marcelina Malissek Christoph Bräuchle Armin Reller Lennart Treuel Ingrid Hilger 《Journal of nanoparticle research》2014,16(1):1-16
Until now, the potential effects of titanium dioxide (TiO2) nanoparticles on endothelial cells are not well understood, despite their already wide usage. Therefore, the present work characterizes six TiO2 nanoparticle samples in the size range of 19 × 17 to 87 × 13 nm, which are commonly present in sun protection agents with respect to their physicochemical properties (size, shape, ζ-potential, agglomeration, sedimentation, surface coating, and surface area), their interactions with serum proteins and biological impact on human microvascular endothelial cells (relative cellular dehydrogenase activity, adenosine triphosphate content, and monocyte chemoattractant protein-1 release). We observed no association of nanoparticle morphology with the agglomeration and sedimentation behavior and no variations of the ζ-potential (?14 to ?19 mV) in dependence on the surface coating. In general, the impact on endothelial cells was low and only detectable at concentrations of 100 μg/ml. Particles containing a rutile core and having rod-like shape had a stronger effect on cell metabolism than those with anatase core and elliptical shape (relative cellular dehydrogenase activity after 72 h: 60 vs. 90 %). Besides the morphology, the nanoparticle shell constitution was found to influence the metabolic activity of the cells. Upon cellular uptake, the nanoparticles were localized perinuclearly. Considering that in the in vivo situation endothelial cells would come in contact with considerably lower nanoparticle amounts than the lowest-observable adverse effects level (100 μg/ml), TiO2 nanoparticles can be considered as rather harmless to humans under the investigated conditions. 相似文献
189.
190.
Claudia Unger Martin Gruene Lothar Koch Juergen Koch Boris N. Chichkov 《Applied Physics A: Materials Science & Processing》2011,103(2):271-277
In this work, the printing mechanism of an alginate-based hydrogel via laser-induced forward transfer (LIFT) is investigated
by spatial and temporal high-resolved stroboscopic imaging. First, the generation of the liquid jet is studied at two different
laser fluences in a process without collector slide. Furthermore, the impingement process onto the collector slide at the
same fluence levels is observed. With the help of these images the development of the jet is explained. Besides the influences
of the collector slide as well as the applied laser fluence on the transfer are demonstrated. 相似文献