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971.
Malitesta C Mazzotta E Picca RA Poma A Chianella I Piletsky SA 《Analytical and bioanalytical chemistry》2012,402(5):1827-1846
This review highlights the importance of coupling molecular imprinting technology with methodology based on electrochemical
techniques for the development of advanced sensing devices. In recent years, growing interest in molecularly imprinted polymers
(MIPs) in the preparation of recognition elements has led researchers to design novel formats for improvement of MIP sensors.
Among possible approaches proposed in the literature on this topic, we will focus on the electrosynthesis of MIPs and on less
common hybrid technology (e.g. based on electrochemistry and classical MIPs, or nanotechnology). Starting from the early work
reported in this field, an overview of the most innovative and successful examples will be reviewed. 相似文献
972.
Sousa J Alves G Abrantes J Fortuna A Falcão A 《Analytical and bioanalytical chemistry》2012,403(1):93-129
Fluoroquinolones are one of the most promising and intensively studied drugs of contemporary anti-infective chemotherapy.
New fluoroquinolone antibacterials with improved pharmacokinetic properties and a broad spectrum of activity have been developed,
opening new windows of opportunity for clinical use. To our knowledge, no comprehensive and critical review of the analytical
methods for the determination of these agents, which correspond to the third- and fourth-generation quinolones, has yet been
published. This work summarizes for the first time most of the liquid chromatographic methods reported in the literature for
the separation and quantification of the new fluoroquinolones in biological matrices and pharmaceutical formulations. A systematic
and detailed survey of physicochemical properties, sample preparation procedures, and chromatographic and detection conditions
is presented herein. In the course of this review several liquid chromatographic methods are discussed: reversed-phase high-performance
liquid chromatography (RP-HPLC), ion-exchange high-performance liquid chromatography (IEX-HPLC), hydrophilic interaction liquid
chromatography (HILIC), high-performance thin-layer chromatography (HPTLC) and other chiral chromatographic methods. Their
advantages, applicability and limitations are also examined. 相似文献
973.
M. Gra?a Dias M. Filomena Cam?es Luísa Oliveira 《Accreditation and quality assurance》2012,17(2):183-189
For consistent interpretation of an analytical method result it is necessary to evaluate the confidence that can be placed
in it, in the form of a measurement uncertainty estimate. The Guide to the expression of Uncertainty in Measurement issued
by ISO establishes rules for evaluating and expressing uncertainty. Carotenoid determination in food is a complex analytical
process involving several mass transfer steps (extraction, evaporation, saponification, etc.), making difficult the application
of these guidelines. The ISO guide was interpreted for analytical chemistry by EURACHEM, which includes the possibility of
using intra- and interlaboratory information. Measurement uncertainty was estimated based on laboratory validation data, including
precision and method performance studies, and also, based on laboratory participation in proficiency tests. These methods
of uncertainty estimation were applied to analytical results of different food matrices of fruits and vegetables. Measurement
uncertainty of food carotenoid determination was 10–30% of the composition value in the great majority of cases. Higher values
were found for measurements near instrumental quantification limits (e.g. 75% for β-cryptoxanthin, and 99% for lutein, in
pear) or when sample chromatograms presented interferences with the analyte peak (e.g. 44% for α-carotene in orange). Lower
relative expanded measurement uncertainty values (3–13%) were obtained for food matrices/analytes not requiring the saponification
step. Based on these results, the saponification step should be avoided if food carotenoids are not present in the ester form.
Food carotenoid content should be expressed taking into account the measurement uncertainty; therefore the maximum number
of significant figures of a result should be 2. 相似文献
974.
Daniel M. Silveira Pedro A. S. Salgueiro M. Filomena G. F. C. Cam?es Ricardo J. N. Bettencourt da Silva 《Accreditation and quality assurance》2012,17(2):115-127
Tear gases are the most widely used non-lethal weapons, both by security forces and by the general public. The pepper spray,
whose active agent is capsaicin, is the only self-defence aerosol allowed in Portugal, where capsaicin concentration must
be below 5 g/100 mL. The cost-effective evaluation of the compliance of self-defence weapons with legislation involves the
use of two measurement procedures with increasing quantitative capability. Samples are first assessed by preliminary measurement
procedure based on single-point GC–MS calibration. Whenever the measurement uncertainty from this assessment makes evaluation
inconclusive, the evaluation of sample compliance using multi-point GC–MS calibration is performed. Metrological models including
sound criteria for the evaluation of sample compliance with legislation were developed for both measurement procedures. Such
models include the evaluation of the impact of instrumental performance, calibration model, sample dilution and standards
preparation on measurement uncertainty. The relative expanded uncertainty, in the studied range (capsaicin 3–7 g/100 mL),
of measurements supported in single-point calibrations ranged from 10 to 22% and the ones supported on multi-point calibrations
from 8 to 12% depending on capsaicin concentration and daily GC–MS repeatability. Measurements are fit for the intended use
since they present a relative expanded uncertainty smaller than a target value of 30, or 15%, for measurements supported in
single- or multi-point calibrations, respectively. 相似文献
975.
Jessie Casimiro Bénédicte Lepoittevin Caroline Boisse-Laporte Marie-Geneviève Barthés-Labrousse Pascale Jegou Fran?ois Brisset Philippe Roger 《Plasma Chemistry and Plasma Processing》2012,32(2):305-323
With the aim of introducing primary amino groups on the surface of poly(ethylene terephthalate) (PET), two methods were compared—the
use of ammonia or a combination of nitrogen and hydrogen low-pressure microwave plasma. Several plasma parameters were optimized
on the reactor to increase the –NH2 surface density, which was estimated by colorimetric titration and X-ray photoelectron spectroscopy (XPS). These techniques
show that whatever the plasma treatment, almost 2 –NH2/nm2 are incorporated on PET films. Emission spectroscopy highlighted a correlation between the density of primary amino groups
and the ratio between an NH peak intensity and an Ar peak intensity (INH/IAr). Variation in surface hydrophilicity with aging in air after plasma treatment was monitored with contact angle measurements
and showed a hydrophobic recovery. This was confirmed by XPS, which suggests also that surfaces treated by NH3 plasma are more stable than surfaces treated by N2/H2. 相似文献
976.
Either the natural biodegradation process or the industrial hydrolytic process requires synergistic interactions between various
cellulases. However, it is sometimes impeded by low hydrolytic rate of existing cellulases and the lack of accessory enzymes.
Herein, the ability of a commercial cellulase (Spezyme CP, from Genencor) to degrade steam explosion-pretreated corn stover
was significantly improved. Firstly, a fungal cellulase producer, Aspergillus fumigatus ECU0811, was isolated from hundreds of soil samples. A 96-deep-well microscale-based platform was developed here to reduce
the labor-intensive screening work and proved to be consistent with macroscale screening work. After optimization of fermentation,
3% corn cob could induce A. fumigatus ECU0811 to yield the highest cellulase production. Based on the high activities of β-glucosidase and xylanase by A. fumigatus ECU0811, 0.91 and 125 U/mg protein, respectively, an enzyme cocktail was composed with a fixed dosage of Spezyme CP (CPCel)
at 14.2 filter paper units (FPU)/g glucan and varied dosages of A. fumigatus cellulase (AFCel). Consequently, the glucan-to-glucose conversion of corn stover was increased from 25.6% in the presence
of CPCel at a dosage of 14.2 FPU/g glucan to 99.5% in the presence of the enzyme cocktail (14.2 FPU CPCel plus 1.21 FPU AFCel
per gram of glucan). On the other side, it reduced the total protein amount of CPCel by as much as tenfold, which extremely
improved the hydrolytic rate of Spezyme CP and reduced its dosage. 相似文献
977.
Two types of sewage sludge anaerobic digestion were carried out: mesophilic and thermophilic. Metal speciation analysis was
performed revealing some changes in the chemical form of the metals during the stabilization process of sludge. After both
methane fermentation processes, a comparable level of organic matter distribution was obtained (≈ 40 %). The amount of produced
methane during thermophilic and mesophilic digestion was 560 mL of CH4 and 580 mL of CH4 from 1 g of removed organic matter, respectively. Low concentration of heavy metal ions in the liquid phase of sludge was
observed. Metal ions precipitated and remained bound throughout the stabilization process. No accumulation of heavy metals
in the mobile fractions of sludge (exchangeable and carbonate) was observed for either digestion process. The highest increase
of zinc, copper, nickel, cadmium, and chromium concentration was observed in the organic-sulfide fraction, whereas the highest
increase of lead was found in the residual fraction. 相似文献
978.
ABSTRACT Copolymers of 1,5-dioxepan-2-one (DXO) and e-caprolactone (?-CL), δ-valerolactone (δ-VL) or L-lactide (LLA) have been synthesized and characterized. High molecular weight copolymers were obtained using stannous-2-ethyl hexanoate as catalyst in bulk. Reactivity ratios for the copolymerization of DXO and δ-VL were determined at 110°C as rVL=0.5 and rDXO=2.3. At high conversion, depolymerization of δ-VL occurred, resulting in lower molecular weight and variations in the copolymer composition. Physical properties, such as crystallinity and melting temperature of the DXO-copolymers proved to be strongly dependent on the choice of comonomer and on the molar composition of the copolymers. DXO appears to be incorporated into the poly-?-caprolactone (PCL) crystals and to some extent into the poly-δ-valerolactone (PVL) crystals, resulting in a more gradual decrease in crystallinity with increasing amount of DXO. 相似文献
979.
Riaño S Alcudia-León MC Lucena R Cárdenas S Valcárcel M 《Analytical and bioanalytical chemistry》2012,403(9):2583-2589
A stir membrane liquid phase microextraction procedure working under the three-phase mode is proposed for the first time for the determination of six anti-inflammatory drugs in human urine. The target compounds are isolated and preconcentrated using a special device that integrates the extractant and the stirring element. An alkaline aqueous solution is used as extractant phase while 1-octanol is selected as supported liquid membrane solvent. After the extraction, all the analytes are determined by liquid chromatography (LC) with ultraviolet detection (UV). The analytical method is optimized considering the main involved variables (e.g., pH of donor and acceptor phases, extraction time, stirring rate) and the results indicate that the determination of anti-inflammatory drugs at therapeutic and toxic levels is completely feasible. The limits of detection are in the range from 12.6 (indomethacin) to 30.7 μg/L (naproxen). The repeatability of the method, expressed as relative standard deviation (RSD, n = 5) varies between 3.4% (flurbiprofen) and 5.7% (ketoprofen), while the enrichment factors are in the range from 35.0 (naproxen) to 72.5 (indomethacin). 相似文献
980.
Stemme F Geßwein H Drahus MD Holländer B Azucena C Binder JR Eichel RA Haußelt J Bruns M 《Analytical and bioanalytical chemistry》2012,403(3):643-650
The fabrication of novel iron-doped barium strontium titanate thin films by means of radio frequency (RF) magnetron co-sputtering is shown. Investigations of the elemental composition and the dopant distribution in the thin films obtained by X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and time-of-flight secondary ion mass spectroscopy reveal a homogeneous dopant concentration throughout the thin film. The incorporation of the iron dopant and the temperature-dependent evolution of the crystal structure and morphology are analyzed by electron paramagnetic resonance spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, and scanning electron microscopy. In summary, these results emphasize the RF magnetron co-sputter process as a versatile way to fabricate doped thin films. 相似文献