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151.
Kofi P. Adragni Elias Al-Najjar Sean Martin Sai K. Popuri Andrew M. Raim 《Computational Statistics》2016,31(3):923-941
Sufficient dimension reduction methodologies in regressions of Y on a p-variate X aim at obtaining a reduction \(R(X) \in {\mathbb R}^{d}, d \le p\), that retains all the regression information of Y in X. When the predictors fall naturally into a number of known groups or domains, it has been established that exploiting the grouping information often leads to more effective sufficient dimension reduction of the predictors. In this article, we consider group-wise sufficient dimension reduction based on principal fitted components, when the grouping information is unknown. Principal fitted components methodology is coupled with an agglomerative clustering procedure to identify a suitable grouping structure. Simulations and real data analysis demonstrate that the group-wise principal fitted components sufficient dimension reduction is superior to the standard principal fitted components and to general sufficient dimension reduction methods. 相似文献
152.
Innovation-driven competitiveness is critical for a country’s long run economic performance in today’s knowledge-based global economy. Although several alternative measures of innovation, productivity, and competitiveness have been proposed, these concepts are inherently linked and this justifies the necessity of studying them in an integrated way, giving emphasis on their potential interrelations. This paper proposes a methodological measurement framework based on multiobjective mathematical programming in order to study the linkage among national innovation, productivity, and competitiveness and discover potential performance patterns. The model is applied in a set of European countries for the period 1998–2008. The empirical results reveal important gaps and show that innovativeness, income, and geographic area significantly affect national performances. 相似文献
153.
Electrochemical Detection Using an Engraved Microchip – Capillary Electrophoresis Platform
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The present study describes a simple strategy to integrate electrochemical detection with an assembled microchip‐capillary electrophoresis platform. The electrochemical cell was integrated with a microfluidic device consisting of five plastic squares interconnected with fused silica capillaries, forming a four‐way injection cross between the separation channel and three side‐arms (each of 15 mm in length) acting as buffer/sample reservoirs. The performance of the system was evaluated using electrodes made with either carbon ink, carbon nanotubes, or gold and under different experimental conditions of pH, capillary length, and injection time. Using this system it was possible to separate the neurotransmitters dopamine and cathecol and to quantify phenol from a real sample using a linear calibration curve with a calculated LOD of 0.7 µM. A similar concept was applied to determine glucose, by including a pre‐reactor filled with beads modified with glucose oxidase (GOx). The latter system was used to determine glucose in a commercial sample, with a recovery of 95.2 %. Overall, the presented approach represents a simple, inexpensive, and versatile approach to integrate electrochemical detection with CE separations without requiring access to microfabrication facilities. 相似文献
154.
Epoxy terpenes cyclize readily, by confinement within zeolite NaY, to form exomethylenic cyclohexanols as the major products. The selective monocyclization of 10,11-epoxyfarnesyl acetate within NaY provides a short and efficient biomimetic route to (+/-)-elengasidiol and (+/-)-farnesiferols B-D. [reaction: see text]. 相似文献
155.
Litos IK Emmanouilidou E Glynou KM Laios E Ioannou PC Christopoulos TK Kampa M Castanas E Gravanis A 《Analytical and bioanalytical chemistry》2007,389(6):1849-1857
In recent years an increasing amount of interest has been directed at the study and routine testing of polymorphisms responsible
for variations in drug metabolism. Most of the current methods involve either time-consuming electrophoresis steps or specialized
and expensive equipment. In this context, we have developed a rapid, simple and robust method for genotyping of CYP2D6*3,
CYP2D6*4, CYP2C19*2, CYP2C19*3 and TPMT*2 single nucleotide polymorphisms (SNP). Genomic DNA is isolated from whole blood
and the segments that span the SNP of interest are amplified by PCR. The products are subjected directly (without purification)
to two primer extension (PEXT) reactions (three cycles each) using normal and mutant primers in the presence of biotin-dUTP.
The PEXT primers contain a (dA)30 segment at the 5′ end. The PEXT products are detected visually by a dry-reagent dipstick-type assay in which the biotinylated
extension products are captured from immobilized streptavidin on the test zone of the strip and detected by hybridization
with oligo(dT)-functionalized gold nanoparticles. Patient samples (76 variants in total) were genotyped and the results were
fully concordant with those obtained by direct DNA sequencing. 相似文献
156.
Jubilut GN Cilli EM Crusca E Silva EH Okada Y Nakaie CR 《Chemical & pharmaceutical bulletin》2007,55(3):468-470
Based on our studies of the stability of model peptide-resin linkage in acid media, we previously proposed a rule for resin selection and a final cleavage protocol applicable to the Nalpha-tert-butyloxycarbonyl (Boc)-peptide synthesis strategy. We found that incorrect choices resulted in decreases in the final synthesis yield, which is highly dependent on the peptide sequence, of as high as 30%. The present paper continues along this line of research but examines the Nalpha-9-fluorenylmethyloxycarbonyl (Fmoc)-synthesis strategy. The vasoactive peptide angiotensin II (AII, DRVYIHPF) and its [Gly8]-AII analogue were selected as model peptide resins. Variations in parameters such as the type of spacer group (linker) between the peptide backbone and the resin, as well as in the final acid cleavage protocol, were evaluated. The same methodology employed for the Boc strategy was used in order to establish rules for selection of the most appropriate linker-resin conjugate or of the peptide cleavage method, depending on the sequence to be assembled. The results obtained after treatment with four cleavage solutions and with four types of linker groups indicate that, irrespective of the circumstance, it is not possible to achieve complete removal of the peptide chains from the resin. Moreover, the Phe-attaching peptide at the C-terminal yielded far less cleavage (50-60%) than that observed with the Gly-bearing sequences at the same position (70-90%). Lastly, the fastest cleavage occurred with reagent K acid treatment and when the peptide was attached to the Wang resin. 相似文献
157.
Kim SH Haimovich-Caspi L Omer L Yu CM Talmon Y Wang NH Franses EI 《Langmuir : the ACS journal of surfaces and colloids》2007,23(10):5657-5664
The stability and state of aggregation of aqueous fibrinogen (FB) and dipalmitoylphosphatidylcholine (DPPC) vesicles in water or buffer at 25 degrees C were studied with dynamic light scattering (DLS), UV-vis spectroturbidimetry (ST), and cryo-transmission electron microscopy (cryo-TEM). In water, when 1000 ppm (0.10 wt %) DPPC dispersions were prepared with a protocol including extensive sonication, they contained mostly vesicles and were quite clear, transparent, and stable for at least 30 days. FB mixtures with water (0.075 wt %) were quite unstable and biphasic. They formed large aggregates which eventually precipitated. The addition of DPPC vesicles into these unstable FB dispersions reversed FB aggregation and precipitation and produced stable translucent microdispersions. The inferred lipid/protein aggregates were limited in size, with average diameters ranging from 200 to 300 nm. In buffer, DPPC dispersions were also clear and quite stable, with average dispersed particles diameter of ca. 90 nm. FB dissolved in aqueous buffer and formed transparent and stable solutions. Adding salt to an aggregated FB dispersion in water reversed the aggregation. FB aggregated and redissolved in the presence of the citrate and after the citrate was removed. There was no effect of citrate (present in FB initially) in the FB aggregation or redissolution. FB molecules in buffer form dimers or higher aggregates. Their average aggregation number is 2, determined with Rayleigh scattering analysis of turbidity data. The average hydrodynamic diameter of FB solutions from DLS was 30 nm. Mixing a stable FB solution in buffer and a stable DPPC dispersion in buffer produced highly unstable mixtures, in which large aggregates precipitated. These results have implications in understanding the interactions of lipids and proteins in many biological applications and food processing applications. 相似文献
158.
159.
Maria Bidikoudi Carmen Simal Vasillios Dracopoulos Elias Stathatos 《Molecules (Basel, Switzerland)》2021,26(19)
Perovskite solar cells that use carbon (C) as a replacement of the typical metal electrodes, which are most commonly employed, have received growing interest over the past years, owing to their low cost, ease of fabrication and high stability under ambient conditions. Even though Power Conversion Efficiencies (PCEs) have increased over the years, there is still room for improvement, in order to compete with metal-based devices, which exceed 25% efficiency. With the scope of increasing the PCE of Carbon based Perovskite Solar Cells (C-PSCs), in this work we have employed a series of ammonium iodides (ammonium iodide, ethylammonium iodide, tetrabutyl ammonium iodide, phenethylammonium iodide and 5-ammonium valeric acid iodide) as additives in the multiple cation-mixed halide perovskite precursor solution. This has led to a significant increase in the PCE of the corresponding devices, by having a positive impact on the photocurrent values obtained, which exhibited an increase exceeding 20%, from 19.8 mA/cm2, for the reference perovskite, to 24 mA/cm2, for the additive-based perovskite. At the same time, the ammonium iodide salts were used in a post-treatment method. By passivating the defects, which provide charge recombination centers, an improved performance of the C-PSCs has been achieved, with enhanced FF values reaching 59%, which is a promising result for C-PSCs, and Voc values up to 850 mV. By combining the results of these parallel investigations, C-PSCs of the triple mesoscopic structure with a PCE exceeding 10% have been achieved, while the in-depth investigation of the effects of ammonium iodides in this PSC structure provide a fruitful insight towards the optimum exploitation of interface and bulk engineering, for high efficiency and stable C-PSCs, with a structure that is favorable for large area applications. 相似文献
160.