全文获取类型
收费全文 | 1549篇 |
免费 | 31篇 |
国内免费 | 6篇 |
专业分类
化学 | 967篇 |
晶体学 | 16篇 |
力学 | 24篇 |
数学 | 289篇 |
物理学 | 290篇 |
出版年
2020年 | 16篇 |
2019年 | 21篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 40篇 |
2012年 | 55篇 |
2011年 | 42篇 |
2010年 | 43篇 |
2009年 | 47篇 |
2008年 | 56篇 |
2007年 | 53篇 |
2006年 | 40篇 |
2005年 | 50篇 |
2004年 | 42篇 |
2003年 | 35篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1988年 | 13篇 |
1987年 | 17篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1978年 | 13篇 |
1960年 | 12篇 |
1958年 | 11篇 |
1956年 | 16篇 |
1934年 | 26篇 |
1933年 | 15篇 |
1932年 | 29篇 |
1931年 | 24篇 |
1930年 | 21篇 |
1929年 | 13篇 |
1928年 | 16篇 |
1926年 | 23篇 |
1925年 | 11篇 |
1923年 | 19篇 |
1922年 | 16篇 |
1910年 | 11篇 |
排序方式: 共有1586条查询结果,搜索用时 15 毫秒
51.
We report the direct observation of 1D and 2D nanostructures of cobalt dipyrromethene trimer complexes adsorbed on a highly oriented pyrolytic graphite surface using scanning tunneling microscopy (STM). STM images showed two types of ordered structures coexisting on the surface: long 1D molecular chains isolated on the terraces, and 2D hexagonal patterns confined by a 1D chain and/or a graphite step edge. These 1D and 2D structures are attributed to ‘edge-on’ and ‘face-on’ complex alignments on the surface, respectively. In both configurations, substrate-mediated molecule-molecule interactions may play a significant role in stabilizing the nanostructures. 相似文献
52.
Summary This paper establishes the Lévy-Hinčin representation for all random compact convex subsets of ℝ which are infinitely divisible
for Minkowski addition.
Research partially supported by NSF grants No. MCS 8100728 and DMS-8318610
Research partially supported by NSF grant No. MCS 8301326 相似文献
53.
Generating Metallic Amorphous Core–Shell Nanoparticles by a Solid‐State Amorphization Process 下载免费PDF全文
Tao Feng Di Wang Chaomin Wang Na Chen Horst Hahn Herbert Gleiter 《Particle & Particle Systems Characterization》2016,33(2):82-88
Metallic crystalline/amorphous core–shell nanoparticles consisting of a crystalline Pd core (c‐Pd) surrounded by an amorphous Fe25Sc75 shell (a‐FeSc) are prepared by inert‐gas condensation. A phase transformation of the c‐Pd by a solid‐state diffusion process resulting in an amorphous core (a‐PdSc) surrounded by an amorphous FeSc shell is observed if the core–shell structure is irradiated at ambient temperature with 300 keV electrons. The amorphization process seems to involve the diffusion of irradiation‐induced defects and is presumably driven by the large negative heat of mixing of Pd and Sc, as well as by the excess enthalpy of the interfaces between the c‐Pd regions and the surrounding a‐FeSc. The structural transformation reported here opens a new way to producing metallic amorphous core–shell nanoparticles of different chemical compositions and probably novel properties. 相似文献
54.
Schmidt WG Hahn PH Bechstedt F Esser N Vogt P Wange A Richter W 《Physical review letters》2003,90(12):126101
The InP(001)(2 x 1) surface has been reported to consist of a semiconducting monolayer of buckled phosphorus dimers. This apparent violation of the electron counting principle was explained by effects of strong electron correlation. Combining first-principles calculations with reflectance anisotropy spectroscopy and LEED experiments, we find that the (2 x 1) reconstruction is not at all a clean surface: it is induced by hydrogen adsorbed in an alternating sequence on the buckled P dimers. Thus, the microscopic structure of the InP growth plane relevant to standard gas phase epitaxy conditions is resolved and shown to obey the electron counting rule. 相似文献
55.
56.
Polydentate ligands with benzene-o-dithiolato donor groups are useful building blocks in supramolecular coordination chemistry. The coordination chemistry of bis- and tris(benzene-o-dithiolato) ligands and mixed benzene-o-dithiolato/catecholato ligands is reviewed. These ligands exhibit a versatile coordination chemistry both in solution and in the solid state. 相似文献
57.
A variable-low-temperature scanning tunneling microscope (STM) was used to observe oxygen (O2), ethylene (C2H4), and acetylene (C2H2) molecules on a Ag(110) surface and the various complexes that were formed between these two hydrocarbons and oxygen at 13 K. Ethylene molecule(s) were moved to the vicinity of O2 either by STM tunneling electrons at 13 K or thermally at 45 K to form (C2H4)x-O2 (x = 1-4) complexes stabilized by C-H...O hydrogen bonding. Acetylene-oxygen complexes involving one or two acetylene molecules were observed. 相似文献
58.
59.
Samuel K. Kutty Joshua A. Lutz Simon Felder Philip Hahn Carol M. Taylor 《Tetrahedron》2018,74(31):4247-4258
The microbisporicins are the most potent lantibiotics isolated to-date. Cyclic tetra-, hexa- and octapeptides, inspired by this family of antimicrobial agents, have been synthesized from linear peptides. Generalized reaction conditions are reported for the two-step conversion of linear peptides to thioether macrocycles: formation of a disulfide followed by reductive desulfurization. 1H NMR analysis of the reduction reaction mixture indicated the intermediacy of a dehydroalanine when excess hexamethylphosphorus triamide (HMPT) was employed for the reduction. Maintaining a stoichiometric amount of HMPT, in dilute methanolic solution, gave the corresponding thioethers, retaining stereochemical integrity. 相似文献
60.
Klaus Grasshoff und Harry Hahn 《Fresenius' Journal of Analytical Chemistry》1962,186(1):147-153
Zusammenfassung Es wird eine polarographische Methode zur Bestimmung von Molybdän in Stahl beschrieben. Als Trägerelektrolyt wird 0,1 m Citronensäure verwendet. Bei pH 2 treten zwei Stufen mit einem Halbstufenpotential von –0,27 und –0,65 V auf. Der Diffusionsstrom bzw. Spitzenstrom beider Stufen ist gut ausgebildet und gut reproduzierbar. Eisen sowie die üblichen in Stählen vorkommenden Elemente stören die Bestimmung nicht. Die Brauchbarkeit und die Genauigkeit der Methode wird an vier verschiedenen Legierungen mit Gehalten von 0,3–1,3% Molybdän demonstriert.V. Mitteilung: Grasshoff, K., u. H. Hahn: diese Z. 186, 132 (1962).Wir danken der Deutschen Forschungsgemeinschaft sowie dem Fonds der Chemischen Industrie für die Unterstützung dieser Arbeit. 相似文献