全文获取类型
收费全文 | 277篇 |
免费 | 14篇 |
专业分类
化学 | 213篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 38篇 |
物理学 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 16篇 |
2012年 | 38篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 13篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 1篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2000年 | 4篇 |
1996年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有291条查询结果,搜索用时 15 毫秒
101.
Silva S Pereira PM Silva P Paz FA Faustino MA Cavaleiro JA Tomé JP 《Chemical communications (Cambridge, England)》2012,48(30):3608-3610
Synthesis of water soluble porphyrin and phthalocyanine derivatives with, respectively, eight and sixteen galactose units has been carried out. The combined preliminary photophysical and photochemical features of the new products suggest that they might be promising photodynamic therapeutic agents. 相似文献
102.
103.
Maria Inês Sucupira Maciel Maria do Socorro de Mendon?a Cavalcanti Thiago Henrique Napole?o Patrícia Maria Guedes Paiva Maria Teresa Jansem de Almeida Catanho Luana Cassandra Breitenbach Barroso Coelho 《Applied biochemistry and biotechnology》2012,168(3):580-591
Lectins, proteins that recognize carbohydrates, have been immobilized on inert supports and used in the screening or purification of glycoproteins. Anacardium occidentale bark infusion has been used as a hypoglycemic agent in Brazil. The toxicity of natural products may be evaluated determining their capability to alter the biodistribution of technetium-99M (99mTc). This work reports the isolation and characterization of a lectin from A. occidentale bark (AnocBL), its evaluation as an affinity support for glycoprotein isolation and lectin effect on the uptake of 99mTc by rat adipocytes. AnocBL was isolated from 80?% ammonium sulphate supernatant by affinity chromatography on fetuin?Cagarose. SDS?CPAGE showed a single protein band of 47?kDa. The monossacharide l-arabinose and the glycoproteins fetuin, asialofetuin, ovomucoid, casein, thyroglobulin, peroxidase, fetal bovine serum and IgG inhibited the activity. The lectin activity was stable until 70?°C and at a pH range of 3.0?C7.5. AnocBL?CSepharose column bound fetuin indicating that the lectin matrix may be used to obtain glycoconjugates of biotechnological interest. In vitro assay revealed that glucose and insulin increase 99mTc uptake by rat adipocytes. AnocBL decreases 99mTc uptake, and this effect was not detected in the presence of glucose. Fetuin inhibited AnocBL effect in all insulin concentrations. 相似文献
104.
S Figueiredo AC Gomes P Neves TR Amarante FA Almeida Paz R Soares AD Lopes AA Valente M Pillinger IS Gonçalves 《Inorganic chemistry》2012,51(15):8629-8635
The reaction of [MoO(2)Cl(2)(pypzEA)] (1) (pypzEA = ethyl[3-(pyridin-2-yl)-1H-pyrazol-1-yl]acetate) with water in a Teflon-lined stainless steel autoclave (100 °C) or in an open reflux system leads to the isolation of the molybdenum oxide/pyrazolylpyridine composite material [Mo(2)O(6)(HpypzA)] (2; HpypzA = [3-(pyridinium-2-yl)-1H-pyrazol-1-yl]acetate). The solid state structure of 2 was solved through single crystal and powder X-ray diffraction analyses in conjunction with information derived from FT-IR and (13)C CP MAS NMR spectroscopies and elemental analyses. In the asymmetric unit of 2, two crystallographically distinct Mo(6+) centers are bridged by a syn,syn-carboxylate group of HpypzA. The periodic repetition of these units along the a axis of the unit cell leads to the formation of a one-dimensional composite polymer, (∞)(1)[Mo(2)O(6)(HpypzA)]. The outstretched pyrazolylpyridine groups of adjacent polymers interdigitate to form a zipper-like motif, generating strong onset π-π contacts between adjacent rings of coordinated HpypzA molecules. The composite oxide 2 is a stable heterogeneous catalyst for liquid-phase olefin epoxidation. 相似文献
105.
Let C be a projective Gorenstein curve over an algebraically closed field of characteristic 0. A generalized linear system on C is a pair (?, ε) consisting of a torsion-free, rank-1 sheaf ? on C, and a map of vector spaces ε: V → Γ(C, ?). If the system is nondegenerate on every irreducible component of C, we associate to it a 0-cycle W, its Weierstrass cycle. Then we show that for each one-parameter family of curves C t degenerating to C, and each family of linear systems (? t , ε t ) along C t , with ? t invertible, degenerating to (?, ε), the corresponding Weierstrass divisors degenerate to a subscheme whose associated 0-cycle is W. We show that the limit subscheme contains always an “intrinsic” subscheme, canonically associated to (?, ε), but the limit itself depends on the family ? t . 相似文献
106.
The definition of the inverse along an element was very recently introduced, and it contains known generalized inverses such as the group, Drazin and Moore–Penrose inverses. In this article, we first prove a simple existence criterion for this inverse in a semigroup, and then relate the existence of such an inverse in a ring to the ring units. 相似文献
107.
Sérgio A. Saraiva Patrícia V. Abdelnur Rodrigo R. Catharino George Nunes Marcos N. Eberlin 《Rapid communications in mass spectrometry : RCM》2009,23(3):357-362
A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS). With no need for sample‐preparation or pre‐separation procedures, EASI‐MS and EASI‐MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
Patricio P Pham CT Romero-Enrique JM 《The European physical journal. E, Soft matter》2008,26(1-2):97-101
It is known that the wetting behaviour of a fluid is deeply altered by the presence of rough or structured substrates. We first review some simple considerations about isotropic fluids and rough substrates, and then we generalize Wenzel's law, which assigns an effective contact angle to a droplet on a rough substrate, when the wetting layer has an ordered phase, like a nematic. We estimate the conditions for which the wetting behavior of an ordered fluid can be qualitatively different from that usually found in a simple fluid. To support our general considerations, we use the Landau-de Gennes mean field approach to investigate theoretically and numerically the wetting transition of a nematic phase on a periodic triangular structured substrate. 相似文献
109.
In this work,we give a complete classification of spherical dihedral f-tilings when the prototiles are two noncongruent isosceles triangles with certain adjacency pattern.As it will be shown,this class is composed by two discrete families denoted by Em,m ≥ 2,m ∈ N,Fk,k ≥ 4,k ∈ N and two sporadic tilings denoted by G and H. 相似文献
110.
Patrícia R. Pinto Luis C. Mendes Marcos L. Dias C. Azuma 《Colloid and polymer science》2006,284(5):529-535
Silica was obtained by sol–gel process through hydrolysis and condensation of tetraethyl orthosilicate (TEOS) using molar
fraction of H2O/TEOS=9 under alkaline catalysis, at different reaction times (5 min to 24 h). At the end of each time, the reaction medium
appeared as a suspended microparticle system. After solvent evaporation, the yield was calculated to be around 100% and practically
independent of the time of reaction. The silica had its surface modified through the condensation reaction with acryloyl chloride
forming organically modified silica. The unmodified and modified silica were characterized by thermogravimetry and derivative
thermogravimetry (TG/DTG), infrared spectrometry (FT-IR), size particle and optical microscopy (OM). The acrylic content was
independent of the reaction time. The methodology represents an alternative route to obtain silica with an unsaturated organic
group, able to polymerize and stabilize up to 300–400°C. The modified material has a potential application as compatibilizing
filler in dental composite. 相似文献