全文获取类型
收费全文 | 1538篇 |
免费 | 41篇 |
国内免费 | 2篇 |
专业分类
化学 | 970篇 |
晶体学 | 13篇 |
力学 | 48篇 |
数学 | 229篇 |
物理学 | 321篇 |
出版年
2021年 | 14篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2016年 | 31篇 |
2015年 | 19篇 |
2014年 | 26篇 |
2013年 | 66篇 |
2012年 | 73篇 |
2011年 | 85篇 |
2010年 | 43篇 |
2009年 | 46篇 |
2008年 | 68篇 |
2007年 | 79篇 |
2006年 | 76篇 |
2005年 | 70篇 |
2004年 | 54篇 |
2003年 | 48篇 |
2002年 | 51篇 |
2001年 | 43篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 24篇 |
1997年 | 13篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 39篇 |
1993年 | 19篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 20篇 |
1985年 | 21篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 20篇 |
1974年 | 12篇 |
1973年 | 18篇 |
1972年 | 14篇 |
1971年 | 10篇 |
排序方式: 共有1581条查询结果,搜索用时 312 毫秒
171.
Shestopalov AA Morris CJ Vogen BN Hoertz A Clark RL Toone EJ 《Langmuir : the ACS journal of surfaces and colloids》2011,27(10):6478-6485
We report a simple, reliable high-throughput method for patterning passivated silicon with reactive organic monolayers and demonstrate selective functionalization of the patterned substrates with both small molecules and proteins. The approach completely protects silicon from chemical oxidation, provides precise control over the shape and size of the patterned features in the 100 nm domain, and gives rapid, ready access to chemically discriminated patterns that can be further functionalized with both organic and biological molecules. 相似文献
172.
P.G. Fleming J.D. Holmes D.J. Otway M.A. Morris 《Journal of solid state chemistry》2011,184(9):2595-2600
Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La2O3 phase. 相似文献
173.
174.
While an unequal population of rapidly interconverting left- and right-handed conformers of a helical oligomer can be detected by circular dichroism, precise quantification of a conformer ratio has not previously been achieved. We demonstrate, using a set of labeled peptide analogues, that simple analysis of peak separation in their (13)C NMR spectra at slow and fast exchange allows an accurate value for the ratio of helical conformers to be obtained. The method reports the ratio of conformers at the site of the label and can therefore be used to investigate local variations in helical conformational control. 相似文献
175.
Cheng G Slawin AM Vautravers NR André P Morris RE Samuel ID Cole-Hamilton D 《Organic & biomolecular chemistry》2011,9(4):1189-1200
A range of dendritic molecules was made using the monodentate SEMI-ESPHOS phosphine oxide ligand, which was derivatised with a series of functional groups including bromide, vinyl, allyl and terminal alkyne. Several methods to attach the resulting precursors onto octavinylsilsesquioxane (OVS), ranging from hydrosilylation, Suzuki, Heck, Grubbs or Sonogashira coupling reactions, have been investigated. Cross-metathesis of SEMI-ESPHOS oxide dendrons containing vinyl end groups with OVS catalyzed by Grubbs' catalyst was proven to be effective in the formation of precursors for dendritic molecules based on OVS. 相似文献
176.
The effects of shape and contact angle on the behaviour of orthorhombic particles at an interface and in thin films were investigated using Surface Evolver. It is shown that the energetically stable orientations of the particle change with its aspect ratio. Long, wide, flat particles with low contact angles are more stable in flat orientations, i.e. with two faces parallel to the flat film surface. More cubic particles with higher contact angles are more stable in twisted orientations, where the opposite sides of the film can be drawn together at the sharp edges of the particle. The combination of contact angle and orientation has been found to have a large effect on the capillary pressure required to rupture the film. A film containing a particle in a flat orientation will rupture at a capillary pressure up to three times greater than one containing an identical particle in a twisted orientation. Wider, flatter particles with low contact angles stabilise thin liquid films to a greater extent than cubic particles with high contact angles. 相似文献
177.
Shojaei-Zadeh S Morris JF Couzis A Maldarelli C 《Journal of colloid and interface science》2011,363(1):25-33
This study demonstrates how luminescent semiconductor nanocrystals (quantum dots or QDs) can be dispersed uniformly in a poly(dimethylsiloxane) (PDMS) matrix by polymerizing a mixture of the prepolymer oligomers and the nanocrystals with a relatively large concentration of crosslinking molecules. A microfluidic device is used to fabricate PDMS microbeads embedded with the QDs by using flow focusing to first form monodisperse droplets of the prepolymer/crosslinker/nanocrystal mixture in a continuous aqueous phase. The droplets are subsequently collected, and heated to polymerize them into solid microbead composites. The degree of aggregation of the nanocrystals in the matrix is studied by measuring the nonradiative resonance energy transfer (RET) between the nanocrystals. For this purpose, two quantum dots are used with maxima in their luminescence emission spectrum at 560 nm and 620 nm. When the nanocrystals are within the F?rster radius (approximately 10 nm) of each other, exciton energy cascades from the QDs which emit at the shorter wavelength to the QDs which emit at the longer wavelength. This energy transfer is quantified, for two concentration ratios of the prepolmer to the crosslinker, by measuring the deviation of the microbead luminescence spectrum from a reference spectrum obtained by dispersing the QD mixture in a solvent (toluene) in which the nanocrystals do not aggregate. For a low concentration of crosslinking molecules relative to the prepolymer (5:1 by weight prepolymer to crosslinker), strong RET is observed as the emission of the 620 nm QDs is increased and the 560 nm QDs is decreased relative to the reference. In the emission spectrum for a higher concentration of crosslinkers (2:1 by weight prepolymer to crosslinker), the resonance energy transfer is less relative to the case of the low concentration of crosslinkers, and the spectrum more closely resembles the reference. This result indicates that the increase in the crosslinker concentration has reduced the nanocrystal aggregation in the cured polymer. The use of crosslinking can serve as a general paradigm for forming, from a prepolymer/nanoparticle mixture, a composite in which the particles are not aggregated. Under the usual conditions the entropic cost to a linearly growing polymer chain of surrounding nanoparticles forces them to aggregate; crosslinking kinetically entraps the particles and circumvents this aggregation driving force. The QD/polymer composite microbeads fabricated in this study find applications in bead-based platforms for high-throughput, multiplexed screening, where the emission spectrum of the QD luminescence can be used as a spectral barcode to label the beads. For microbeads in which the nanocrystals are uniformly dispersed, this barcode is undistorted by energy transfer, and is easily read. 相似文献
178.
This paper studies the compressional dispersive Alfvén (CDA) waves where Noether symmetries will be calculated from which the corresponding conservation laws will be obtained via Noether's theorem. Furthermore, one case of double reduction is performed via the association of a conserved vector with a Noether symmetry (with zero gauge). The conserved quantities of optical solitons in the presence of intermodal dispersion that is governed by the perturbed nonlinear Schrödinger's equation with Kerr law nonlinearity. The invariance-multiplier method is adopted to carry out the analysis, from which the conserved densities are then retrieved. Finally, the conserved quantities are obtained using the 1-soliton solution of the governing equation. 相似文献
179.
Indrek S. Wichman Scott C. Morris Andrew W. McIntosh 《Experimental Thermal and Fluid Science》2002,25(8):595-603
A fire testing facility named the “MSU Fire Tunnel” has been developed. The intent was to devise a testing apparatus that controlled the flow of oxidizing gas in the tunnel to an extent not heretofore accomplished. A novel approach was developed for mounting the flame-spread samples flush with the surface of an “airfoil”. This method avoids previous complications of determining the exact position of the leading edge of the velocity boundary layer. Data were gathered for the flow field using hot-wire anemometry. These data indicated that a zero-pressure gradient Blasius boundary layer flow was established along the airfoil and fuel sample surfaces. Opposed-flow flame-spread tests were conducted and correlations were produced that support the predictive capacity of this apparatus. It was shown that the opposed flow flame-spread data allowed distinctions to be made between correlations of previous researchers. No such comparisons were formerly possible. A finite-chemistry correlation was shown to be consistent with, and similar to, correlations derived in the previous work. 相似文献
180.
The processes of electron transfer and dissociative scattering are explored for collisions of hyperthermal NO+ on GaAs(110). The experiments reveal a marked angular dependence to O− emergence. A strong correlation between the O− scattering angle and the final atom-surface interaction site provides a map of the lateral dependence to reactivity. The results are modeled by sequential neutralization, dissociation, and electron attachment steps. Classical trajectory calculations, in conjunction with an empirical opacity function, accurately reproduce the experimental results. The opacity function is interpreted as the probability that an electron will attach to a departing O fragment as a function of the last surface site the atom impacts. The experiments indicate that O− emergence occurs predominantly for oxygen atoms which come in close contact with the localized dangling bond states of GaAs(110). 相似文献