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981.
Resveratrol is a polyphenol isolated from many natural sources including grapes, mulberries, eucalyptus, spruce, lilies, and peanuts. The hydroxyl groups in polyphenols can be substituted with various functional groups, allowing production of multiple derivatives. NMR spectroscopy is used to identify new derivatives. Since the complete NMR data of the known derivatives can be useful for identification of the newly isolated derivatives, here, we report the synthesis of 14 methoxylated stilbenes and four 1,2-diphenylethanes and their NMR data. 相似文献
982.
J Eyssautier D Frot L Barré 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):11997-12004
The abundant literature involving asphaltene often contrasts dynamic measurements of asphaltene solutions, highlighting the presence of small particle sizes between 1 and 3 nm, with static scattering measurements, revealing larger aggregates with a radius of gyration around 7 nm. This work demonstrates the complementary use of the two techniques: a homemade dynamic light scattering setup adapted to dark and fluorescent solutions, and small-angle X-ray and neutron scattering. Asphaltene solutions in toluene are prepared by a centrifugation separation to investigate asphaltene polydispersity. These experiments demonstrate that asphaltene solutions are made of Brownian colloidal aggregates. The hydrodynamic radii of asphaltene aggregates are between 5 and 10 nm, while their radii of gyration are roughly comparable, between 3.7 and 7.7 nm. A small fraction of asphaltenes with hydrodynamic and gyration radii around 40 nm is found in the pellet of the centrifugation tube. The fractal character of the largest clusters is observed from small angle scattering nearly on a decade length scale. Previous results on aggregation mechanisms are confirmed ( Eyssautier, J., et al. J. Phys. Chem. B 2011 , 115 , 6827 ): nanoaggregates of 3 nm radius, and with hydrodynamic properties also frequently illustrated in the literature, aggregate to form fractal clusters with a dispersity of aggregation number. 相似文献
983.
Freire MG Pereira JF Francisco M Rodríguez H Rebelo LP Rogers RD Coutinho JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(6):1831-1839
New polyethylene glycol (PEG)/ionic liquid aqueous biphasic systems (ABS) are presented. Distinct pairs of PEG polymers and ionic liquids can induce phase separation in aqueous media when dissolved at appropriate concentrations. Phase diagrams have been determined for a large array of systems at 298, 308 and 323 K. A comparison of the binodal curves allowed the analysis of the tunable structural features of the ionic liquid (i.e., anionic nature, cationic core, cationic alkyl side chain length and functionalisation, and number of alkyl substituents in the cation) and the influence of the molecular weight of the PEG polymer on the ability of these solutes to induce an ABS. It was observed that contrary to typical ABS based on ionic liquids and inorganic salts, in which the phase behaviour is dominated by the formation of the hydration complexes of the ions, the interactions between the PEG polymers and ionic liquids control the phase demixing in the polymer-type ABS studied herein. It is shown that both the ionic liquids and PEG polymers can act as the salting-out species; that is, it is an occurrence that is dependent on the structural features of the ionic liquid. For the first time, PEG/ionic liquid ABS are reported and insight into the major interactions that govern the polymer/ionic liquid phase behaviour in aqueous media are provided. The use of two different nonvolatile and tunable species (i.e., ionic liquids and PEG polymers) to form ABS allows the polarities of the phases to be tailored. Hence, the development of environmentally friendly separation processes that make use of these novel systems is envisaged. 相似文献
984.
Jo?o A. Sousa Alexandra M. Reynolds álvaro S. Ribeiro 《Accreditation and quality assurance》2012,17(2):207-214
The evaluation of measurement uncertainties has been widely applied to the calibration of measurement instruments, whereas
its application to tests, despite increasing requirements, is a more recent phenomenon. The generalization of the evaluation
of measurement uncertainties to tests has been a gradual process, in line with changes in the requirements of the normative
framework that regulates the accreditation of tests laboratories and also as the perceived good practices have evolved. The
sole identification of the relevant sources of uncertainty was followed by the requirement to provide a simplified estimate
of the measurement uncertainty, and it is now an accepted requirement to properly evaluate the expanded measurement uncertainty
associated with any tests. In this study, the evaluation of measurement uncertainty associated with the determination of sulfate
in water will be attempted using a procedure that includes linear regression, with the regression parameters provided with
associated uncertainties, and a Monte Carlo method applied as a validation tool of the conventional mainstream evaluation
method, concerning the approximations in terms of linearization of the model and the assumed shape of the output distribution
introduced by this approach. 相似文献
985.
Sang-Keun JinChul-Wook Kim Ki-Hwa ChungKwang-Keun Jo Jin-Yeon JeongIn-Chul Hur Eun-Young JungSeon-Tea Joo Han-Sul Yang 《Radiation Physics and Chemistry》2012,81(2):208-215
To determine the effect of different irradiation doses on ready-to-eat (RTE) dry-cured shoulder hams, physicochemical and sensory attributes were analyzed during 8 weeks of refrigerated storage. The results show that irradiation reduced the redness value and increased the 2-thiobarbituric acid-reactive substance (TBARS) value as well as the irradiation aroma during storage. However, ham samples irradiated with 2.5 and 5.0 kGy did not show significant changes in lightness values compared to the control sample during 8 weeks of storage. TBARS values were lower in the sample irradiated with 2.5 kGy than in the other irradiated samples. The total plate counts of the 5.0 kGy-irradiated samples were not measured after 0 weeks. Sensory panels found that the 2.5- and 5.0 kGy-irradiated samples had better overall acceptability scores than the other irradiated samples. It was concluded that treatments with lower levels of irradiation (≤5.0 kGy) can enhance the microbial safety and sensory acceptance of dry-cured shoulder hams. 相似文献
986.
Effects of low-level gamma irradiation on the characteristics of fermented pork sausage during storage 总被引:1,自引:0,他引:1
I.S. KimC. Jo K.H. LeeE.J. Lee D.U. AhnS.N. Kang 《Radiation Physics and Chemistry》2012,81(4):466-472
The effect of gamma irradiation (0.5, 1, 2, and 4 kGy) on the quality of vacuum-packaged dry fermented sausages during refrigerated storage was evaluated. At Day 0 of irradiation, the pH, redness (CIE a?), yellowness (CIE b?), 2-thiobarbituric acid-reactive substances (TBARS) and volatile basic nitrogen (VBN) values of samples irradiated at 2 and 4 kGy were higher (p<0.05), but the CIE L? values (lightness) were lower than those of the non-irradiated control (p<0.05). At<1 kGy irradiation, however, the pH, CIE L?, CIE a? and CIE b?-value of samples were not significantly influenced by irradiation. The CIE a?, and CIE b?-values of samples irradiated at 2 and 4 kGy decreased with the increase of storage time. The VBN, TBARS, and CIE L?-values of samples irradiated at 4 kGy were not changed significantly during refrigerated storage for 90 days (p>0.05). The total plate counts (TPC) and lactic acid bacteria (LAB) in the samples irradiated at 4 kGy were significantly lower (p<0.01) than those with lower irradiation doses. At the end of storage, the TPC, coliform, and LAB in the samples were not increased after irradiation at 1, 0.5 and 1 kGy, respectively. TPC and LAB were not detected in samples irradiated at 4 kGy at Day 90. In addition, no coliform bacteria were found in samples irradiated at 1 kGy during refrigerated storage. Sensory evaluation indicated that the rancid flavor of samples irradiated at 4 kGy was significantly higher, but aroma and taste scores were lower than those of the control at Day 3 of storage. Irradiation of dry fermented sausages at 2 kGy was the best conditions to prolong the shelf-life and decrease the rancid flavor without significant quality deterioration. 相似文献
987.
The monitoring of non-structural viral protein 3 (NS3) has been of considerable interest in developing simple and reliable methods for detection of hepatitis C virus (HCV) for applications in diagnostic medicine. Although enzyme-linked immunosorbent assay (ELISA) is the most general method in HCV detection, using antibody brings problems. This method is temperature-sensitive and requires specific reactions condition. In addition, secondary antibody conjugated with enzyme and fluorescent dye is required. To overcome these bottlenecks, we designed a streptavidin-biotin conjugation method, namely, the RNA oligonucleotide sensor system that could monitor viral protein with detection limit of 500 pg/mL by using biotin-tagged RNA oligonucleotide in forteBio??s Octet optical biosensor system. In this study, we proposed an efficient method for simple and convenient detection of HCV viral protein, with the advantage of target specific monitoring. 相似文献
988.
Leite JF Assreuy AM Mota MR Bringel PH Lacerda RR Gomes Vde M Cajazeiras JB Nascimento KS Pessôa Hde L Gadelha CA Delatorre P Cavada BS Santi-Gadelha T 《Molecules (Basel, Switzerland)》2012,17(3):3277-3290
Lectins are proteins that have the ability to bind specifically and reversibly to carbohydrates and glycoconjugates, without altering the structure of the glycosyl ligand. They are found in organisms such as viruses, plants and humans, and they have been shown to possess important biological activities. The objective of this study was to purify and characterize lectins in the seeds of Clitoria fairchildiana, as well as to verify their biological activities. The results indicated the presence of a lectin (CFAL) in the glutelin acid protein fraction, which agglutinated native rabbit erythrocytes. CFAL was purified by column chromatography ion-exchange, DEAE-Sephacel, which was obtained from a peak of protein retained in the matrix by applying 0.5 M NaCl using the step-wise method. Electrophoretic analysis of this lectin in SDS-PAGE indicated a two band pattern protein molecular mass of approximately 100 and 116 kDa. CFAL proved to be unspecific to all carbohydrates/glycoconjugates in common use for the sugar inhibition test. This lectin showed no significant cytotoxicity to human red blood cells. It was observed that CFAL has anti-inflammatory activity in the paw edema induced by carrageenan model, in which a 64% diminution in edema was observed. Antinociceptive effects were observed for CFAL in the abdominal writhing test (induced by acetic acid), in which increasing doses of the lectin caused reduction in the number of contortions by up to 72%. It was concluded that the purified and characterized lectin from the seeds of Clitoria fairchildiana has anti-inflammatory and antinociceptive activity, and is not cytotoxic to human erythrocytes. 相似文献
989.
Inorganic salts in purely ionic liquid media: the development of High Ionicity Ionic Liquids (HIILs)
Pereiro AB Araújo JM Oliveira FS Bernardes CE Esperança JM Lopes JN Marrucho IM Rebelo LP 《Chemical communications (Cambridge, England)》2012,48(30):3656-3658
This work explores the possibility of increasing the ionicity of ionic liquids via the solubilization of inorganic salts in their midst. The resulting purely ionic media-distinct ionic liquid plus inorganic salt mixtures-are liquid in an extensive concentration range and can be aptly denominated High Ionicity Ionic Liquids (HIILs). 相似文献
990.