全文获取类型
收费全文 | 812篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 615篇 |
晶体学 | 4篇 |
力学 | 14篇 |
数学 | 109篇 |
物理学 | 84篇 |
出版年
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 32篇 |
2015年 | 26篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 45篇 |
2011年 | 57篇 |
2010年 | 37篇 |
2009年 | 27篇 |
2008年 | 48篇 |
2007年 | 37篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1992年 | 5篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1979年 | 10篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 13篇 |
1974年 | 24篇 |
1973年 | 17篇 |
1972年 | 6篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1956年 | 4篇 |
1902年 | 3篇 |
1901年 | 3篇 |
1888年 | 3篇 |
排序方式: 共有826条查询结果,搜索用时 15 毫秒
791.
Obermajer N Sattin S Colombo C Bruno M Svajger U Anderluh M Bernardi A 《Molecular diversity》2011,15(2):347-360
In this article, we describe the design, synthesis and activity evaluation of glycomimetic DC-SIGN antagonists, that use a
mannose residue to anchor to the protein carbohydrate recognition domain (CRD). The molecules were designed from the structure
of the known pseudo-mannobioside antagonist 1, by including additional hydrophobic groups, which were expected to engage lipophilic areas of DC-SIGN CRD. The results demonstrate
that the synthesized compounds potently inhibit DC-SIGN-mediated adhesion to mannan coated plates. Additionally, in silico
docking studies were performed to rationalize the results and to suggest further optimization. 相似文献
792.
Ferdinand Männle Terje Rosquist Tofteberg Morten Skaugen Huaitian Bu Thijs Peters Pascal D. C. Dietzel Monika Pilz 《Journal of nanoparticle research》2011,13(10):4691-4701
A route to a large variety of functionalized POSS compounds by a two-step procedure has been developed. Up-scaling to high
volume industrial applications is feasible. In the first step, an amino-functionalized silane such as 3-aminopropyltriethoxy
silane is converted to amino-functionalized POSS (amine-POSS) by a sol–gel process. In the second step, the amine groups of
amine-POSS are converted by state-of-the-art amine chemistry. A large number of reactants including carboxylic acids, esters,
anhydrides, isocyanates, carbonates, epoxides, and acrylates as well as reactants suitable for nucleophilic substitution can
be applied. Conversion of an amine-POSS with hexanoic acid leads to an amide-POSS. Amine chemistry can usually be performed
under mild conditions, which suppresses degradation and/or cross-linking reactions of the amine-POSS during the conversion.
MALDI-TOF mass spectroscopy and dynamic light scattering (particle size: 3–6 nm) have been applied to prove the conversion
of an amine-POSS to an amide-POSS. 1H-NMR and TGA-MS prove the presence of amide-POSS and its thermal stability. Gas barrier properties of nanocomposite coatings
based on functionalized POSS are characterized. 相似文献
793.
The paradox of destabilization of a conservative or non-conservative system by small dissipation,or Ziegler’s paradox(1952),has stimulated a growing interest in the sensitivity of reversible and Hamiltonian systems with respect to dissipative perturbations.Since the last decade it has been widely accepted that dissipation-induced instabilities are closely related to singularities arising on the stability boundary,associated with Whitney’s umbrella.The first explanation of Ziegler’s paradox was given(much earlier)by Oene Bottema in 1956.The aspects of the mechanics and geometry of dissipation-induced instabilities with an application to rotor dynamics are discussed. 相似文献
794.
Flow field through rotating porous disc was investigated with experimental fluid dynamics and compared with computational
fluid dynamics. Open cell aluminum metal foam with 88% porosity was used. On rotating porous disc, integral measurements of
static pressure difference in dependence of air volume flow rate were performed. Local measurements of velocity profiles close
to disc circumference were performed with hot-wire anemometry. The airflow visualization method using smoke generator and
digital camera was performed. Flow structures through porous disc were visualized at three different air volume flow rates.
Numerical simulation of homogenous rotating porous disc was performed. Experimental and numerical results were compared. The
results showed appropriate comparison of integral and local properties. The presented experimental approach can be used for
the investigation and understanding of flow field phenomena on rotating porous materials. The proposed conclusions can be
applied for variable applications on rotating porous materials. 相似文献
795.
Puterová Z Valentová J Bojková Z Kožíšek J Devínsky F 《Dalton transactions (Cambridge, England : 2003)》2011,40(7):1484-1490
The synthesis and solid-state structure of mononuclear copper(II) complexes [Cu(SAIB)(H(2)O)(2)] (1), [Cu(SBAIB)(H(2)O)(2)]·H(2)O (2) and [Cu(SGABA)(H(2)O)(2)] (3) are described. Schiff base ligands H(2)SAIB, H(2)SBAIB and H(2)SGABA chelate the copper(II) ion in an O,N,O tridentate fashion. The square-pyramidal geometry of the final complexes is completed by two water ligands. The formation of an unusual seven-membered ring in the set of copper(II) N-salicylidene-aminoacidates is reported. Compounds 1-3 were evaluated by the antiradical activity assay. 相似文献
796.
Jarmila Müllerová Marinus Fischer Marie Netrvalová Miro Zeman Pavel Šutta 《Central European Journal of Physics》2011,9(5):1301-1308
The effect of deposition temperature on the structural and optical properties of amorphous hydrogenated silicon (a-Si:H) thin
films deposited by plasma-enhanced chemical vapour deposition (PECVD) from silane diluted with hydrogen was under study. The
series of thin films deposited at the deposition temperatures of 50–200°C were inspected by XRD, Raman spectroscopy and UV
Vis spectrophotometry. All samples were found to be amorphous with no presence of the crystalline phase. Ordered silicon hydride
regions were proved by XRD. Raman measurement analysis substantiated the results received from XRD showing that with increasing
deposition temperature silicon-silicon bond-angle fluctuation decreases. The optical characterization based on transmittance
spectra in the visible region presented that the refractive index exhibits upward trend with increasing deposition temperature,
which can be caused by the densification of the amorphous network. We found out that the scale factor of the Tauc plot increases
with the deposition temperature. This behaviour can be attributed to the increasing ordering of silicon hydride regions. The
Tauc band gap energy, the iso-absorption value their difference were not particularly influenced by the deposition temperature.
Improvements of the microstructure of the Si amorphous network have been deduced from the analysis. 相似文献
797.
Yaqin Xu Lizanne Pharand Quan Wen Ferdinand Gonzaga Yingfu Li M. Monsur Ali Carlos D. M. Filipe Robert Pelton 《Colloid and polymer science》2011,289(5-6):659-666
Compared are two approaches for the biotinylation of poly(N-isopropylacrylamide-co-vinylacetic acid) microgels, 300-nm diameter, water swollen particles with a corona of carboxyl groups. The biotinylated microgels are a platform for bioactive water-based ink. Streptavidin binding was measured as a function of biotin density, and the results were interpreted with a new model that predicts the minimum local density of biotins required to capture a streptavidin. An amino-polyethylene glycol derivative of biotin gave higher biotin contents than a biotin hydrazide. However, the streptavidin content versus biotin content results for both biotin derivatives fell on the same master curve with maximum biotin coverage of 0.11?mg of bound streptavidin per milligram of biotinylated microgel. Exclusion experiments showed that streptavidin was too big to penetrate the cross-linked microgel structure; thus, the conjugated streptavidin was restricted to the microgel surface. The colloidal stability of the microgels was preserved, and the biotinylated products showed good hydrolytic stability. 相似文献
798.
Brook MA Whinton M Gonzaga F Li N 《Chemical communications (Cambridge, England)》2011,47(31):8874-8876
Robust, transparent elastomeric hydrogels encoded with a bicontinuous structure result from the sequential photopolymerization of the aqueous hydroxyethyl methacrylate phase and crosslinking of the silicone phase of a silicone microemulsion stabilized with an acrylate-functional silicone-poly(ethylene glycol) surfactant. 相似文献
799.
Emília Illeková Jana Harnúšková Roman Florek František Simančík Igor Maťko Peter ŠvecSr. 《Journal of Thermal Analysis and Calorimetry》2011,105(2):583-590
The eventual competition between the dehydrogenation and oxidation of TiH2 powder in the argon, oxygen, and static air atmospheres has been examined in the regime of linear heating using differential thermal analysis (DTA), X-ray diffraction, transmission and scanning electron microscopy coupled to energy dispersive spectroscopy techniques. Three stages of dehydrogenation, R1, R2, and R3, and two different oxidation reactions, O1 and O2, have been identified. The kinetics of individual reactions has been investigated by the Kissinger and Suriñach curve fitting procedures. While the kinetics of O1, O2, and R1 reactions depends on the diffusivities of the external reagent gas, being oxygen, and internal product gas, being hydrogen, the main dehydrogenation stage R2 is controlled by the combined nucleation-and-growth and coalescence kinetics. The effect of pre-annealing of TiH2 on its subsequent degradation has also been studied. Due to the huge overheating accompanying both oxidation reactions in the DTA set-up, substantial thermal losses have been demonstrated and the method to obtain the true heat of oxidation reactions in metals has been described. 相似文献
800.
Josef Šlapal 《Applied Categorical Structures》2011,19(2):523-537
We introduce and deal with a convergence on (objects of) constructs which is expressed in terms of generalized nets. The generalized
nets used are obtained from the usual nets by replacing the construct of directed sets and cofinal maps by an arbitrary construct.
Convergence separation and convergence compactness are then introduced in a natural way. We study the convergence compactness
and compactification and show that they behave in much the same way as the compactness and compactification of topological
spaces. 相似文献