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991.
Impact of gas chromatography and mass spectrometry combined with gas chromatography and olfactometry for the sex differentiation of Baccharis articulata by the analysis of volatile compounds
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Manuel Minteguiaga Noelia Umpiérrez Laura Fariña Manuel A. Falcão Vanessa. B. Xavier Eduardo Cassel Eduardo Dellacassa 《Journal of separation science》2015,38(17):3038-3046
The Baccharis genus has more than 400 species of aromatic plants. However, only approximately 50 species have been studied in oil composition to date. From these studies, very few take into consideration differences between male and female plants, which is a significant and distinctive factor in Baccharis in the Asteraceae family. Baccharis articulata is a common shrub that grows wild in south Brazil, northern and central Argentina, Bolivia, Paraguay and Uruguay. It is considered to be a medicinal plant and is employed in traditional medicine. We report B. articulata male and female volatile composition obtained by simultaneous distillation–extraction technique and analyzed by gas chromatography with mass spectrometry. Also, an assessment of aromatic differences between volatile extracts was evaluated by gas chromatography with olfactometry. The results show a very similar chemical composition between male and female extracts, with a high proportion of terpene compounds of which β‐pinene, limonene and germacrene D are the main components. Despite the chemical similarity, great differences in aromatic profile were found: male plant samples exhibited the strongest odorants in number and intensity of aromatic attributes. These differences explain field observations which indicate differences between male and female flower aroma, and might be of ecological significance in the attraction of pollinating insects. 相似文献
992.
Elaine Cristina Azevedo Gilberto Orivaldo Chierice Salvador Claro Neto Daniel Scheidegger Soboll Eduardo Mauro Nascimento Carlos Mauricio Lepienski 《辐射效应与固体损伤》2013,168(3):208-214
In this study, an adhesive of a polyurethane derivate from castor oil was irradiated with gamma radiation from a 60Co source, at doses from 0.2 to 25 kGy. This adhesive polyurethane is considered for use in hospital furniture because it does not liberate dangerous solvents. Hardness and elastic modulus were measured by instrumented indentation with a pyramidal Berkovich indenter, using loads from 0.08–40 mN with a nanoindenter XP. The instrumented indentation hardness was 110 MPa for an untreated sample, increasing to 124 MPa after irradiation with 25 kGy, at penetration depths of about 5 μm. The increases in elastic modulus induced by radiation were less pronounced. This polyurethane is naturally cross-linked and the relative modifications in the hardness are attributed to an additional cross-linking process induced by radiation. X-ray diffraction indicates a slight increase in crystallinity. The roughness measured by atomic force microscopy increases after gamma irradiation. 相似文献
993.
994.
Silvina C. Carretero Cristina Dapeña Eduardo E. Kruse 《Isotopes in environmental and health studies》2013,49(3):399-419
This contribution presents the hydrochemical and isotopic characterisation of the phreatic aquifer located in the Partido de la Costa, province of Buenos Aires, Argentina. In the sand-dune barrier geomorphological environment, groundwater is mainly a low-salinity Ca-HCO3 and Na-HCO3-type, being in general suitable for drinking, whereas in the continental plain (silty clay sediments), groundwater is a Na-Cl type with high salinity and unsuitable for human consumption. The general isotopic composition of the area ranges from?6.8 to?4.3 ‰ for δ18O and from?39 to?21 ‰ for δ2H, showing that rainwater rapidly infiltrates into the sandy substrate and reaches the water table almost without significant modification in its isotopic composition. These analyses, combined with other chemical parameters, made it possible to corroborate that in the eastern area of the phreatic aquifer, there is no contamination from marine salt water. 相似文献
995.
Robinson I. Roacho Alejandro J. Metta‐Magaña Eduardo Peña‐Cabrera Keith H. Pannell 《Journal of Physical Organic Chemistry》2013,26(4):345-351
Fluorescent members of the 4, 4‐difluoro‐4‐bora‐3a, 4a‐diaza‐s‐indacene (BODIPY) family are widely used for a range of markers, dyes, and sensors. The capacity to substitute the basic framework is an attractive feature permitting a range of differently substituted materials to be formed. New isomeric BODIPYs, o‐, m‐, and p‐8‐[R‐C6H4]‐BODIPY (R = CH2OH, 2a (o), 2b (m), 2c (p); R = OMe, 3a (o), 3b (m), 3c (p)), have been synthesized and characterized by nuclear magnetic resonance, absorbance and emission spectroscopy, and single crystal X‐ray diffraction. The o‐isomers have a very high quantum yield emission in non‐polar solvents, while the m‐ and p‐ analogs showed weak fluorescence under the same conditions. Spectroscopic analysis, as well as X‐ray structural characterization, suggested that substitution in the ortho‐position of the phenyl ring is sufficient to increase the steric hindrance and hence impede the rotation of the phenyl moiety about the 8C‐C axis, thereby favoring radiative compared to non‐radiative relaxation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
996.
The finite element based approximation of a quasilinear elliptic equation of non monotone type with Neumann boundary conditions
is studied. Minimal regularity assumptions on the data are imposed. The consideration is restricted to polygonal domains of
dimension two and polyhedral domains of dimension three. Finite elements of degree k ≥ 1 are used to approximate the equation. Error estimates are established in the L
2(Ω) and H
1(Ω) norms for convex and non-convex domains. The issue of uniqueness of a solution to the approximate discrete equation is
also addressed. 相似文献
997.
González Álvarez J Blanco Gomis D Arias Abrodo P Díaz Llorente D Busto E Ríos Lombardía N Gotor Fernández V Gutiérrez Álvarez MD 《Analytical and bioanalytical chemistry》2011,400(5):1209-1216
Two ionic liquids (ILs), namely (S,S)-1-butyl-3-(2'-hydroxy-cyclohexyl)-3H-imidazol-1-ium tetrafluoroborate and (S,S)-1-butyl-3-(2'-acetyl-cyclohexyl)-3H-imidazol-1-ium tetrafluoroborate have been employed as stationary phases in capillary gas chromatography. These new phases exhibit a column efficiency of 1,600 and 2,100 plates m(-1) for IL 1 and IL 2, respectively, a wide operating temperature range and good thermal stability (bleeding temperature of 250 °C for IL 1 and 160 °C for IL 2). Inverse gas chromatography (GC) analyses were used to study the solvation properties of these ILs through a linear solvation energy model. The application of these ILs as new GC stationary phases was studied. These stationary phases exhibited unique selectivity for many organic substances, such as alkanes, ketones, esters, and aromatic compounds. The efficient separation of several mixtures containing compounds of different polarities and the good separation of fatty acid methyl esters (FAMEs) and cis/trans isomers indicate that these ILs may be applicable as a new type of GC stationary phases. 相似文献
998.
Vera L Aceña L Guasch J Boqué R Mestres M Busto O 《Analytical and bioanalytical chemistry》2011,399(6):2073-2081
An electronic nose based on coupling of headspace (HS) with a mass spectrometer (MS) has been used in this study to classify
and characterize a series of beers according to their production site and chemical composition. With this objective, we analyzed
67 beers of the same brand and preparation process but produced in different factories. The samples were also subjected to
sensory evaluation by a panel of experts. Linear discriminant analysis (LDA) was used as the classification technique and
stepwise LDA based on Wilk’s lambda criterion was used to select the most discriminating variables. To interpret the aroma
characteristics of the beers from the m/z ions obtained, score and loading bi-plots were obtained by applying canonical variables. Because the beers analyzed were
marketed with the same name and brand, we expected to be working with the same product irrespective of its origin. However,
results from both sensory evaluation and use of the e-nose revealed differences between factories. With the e-nose it was
possible to relate these differences to the presence (and abundance) of characteristic ions of different compounds typically
found in beer. These results demonstrate that the HS–MS e-nose is not only an aroma sensor capable to classify and/or differentiate
samples but it can also provide information about the compounds responsible for this differentiation. 相似文献
999.
Eduardo Hernández Michelle Pierri Maria Aparecida Bená 《Applied mathematics and computation》2011,217(22):8963-8972
We study the existence of asymptotically almost periodic classical solutions for a class of abstract neutral integro-differential equation with unbounded delay. A concrete application to partial neutral integro-differential equations which arise in the study of heat conduction in fading memory material is considered. 相似文献
1000.
We derive a satisfying rate of convergence of the Marcus-Lushnikov process towards the solution to Smoluchowski’s coagulation equation. Our result applies to a class of homogeneous-like coagulation kernels with homogeneity degree ranging in (−∞,1]. It relies on the use of a Wasserstein-type distance, which has shown to be particularly well-adapted to coalescence phenomena. It was introduced and used in preceding works (Fournier and Laurençot (2006) [7]) and (Fournier and Löcherbach (2009) [8]). 相似文献