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981.
In this work we consider the state estimation problem in nonlinear/non-Gaussian systems. We introduce a framework, called the scaled unscented transform Gaussian sum filter (SUT-GSF), which combines two ideas: the scaled unscented Kalman filter (SUKF) based on the concept of scaled unscented transform (SUT) (Julier and Uhlmann (2004) [16]), and the Gaussian mixture model (GMM). The SUT is used to approximate the mean and covariance of a Gaussian random variable which is transformed by a nonlinear function, while the GMM is adopted to approximate the probability density function (pdf) of a random variable through a set of Gaussian distributions. With these two tools, a framework can be set up to assimilate nonlinear systems in a recursive way. Within this framework, one can treat a nonlinear stochastic system as a mixture model of a set of sub-systems, each of which takes the form of a nonlinear system driven by a known Gaussian random process. Then, for each sub-system, one applies the SUKF to estimate the mean and covariance of the underlying Gaussian random variable transformed by the nonlinear governing equations of the sub-system. Incorporating the estimations of the sub-systems into the GMM gives an explicit (approximate) form of the pdf, which can be regarded as a “complete” solution to the state estimation problem, as all of the statistical information of interest can be obtained from the explicit form of the pdf (Arulampalam et al. (2002) [7]).In applications, a potential problem of a Gaussian sum filter is that the number of Gaussian distributions may increase very rapidly. To this end, we also propose an auxiliary algorithm to conduct pdf re-approximation so that the number of Gaussian distributions can be reduced. With the auxiliary algorithm, in principle the SUT-GSF can achieve almost the same computational speed as the SUKF if the SUT-GSF is implemented in parallel.As an example, we will use the SUT-GSF to assimilate a 40-dimensional system due to Lorenz and Emanuel (1998) [27]. We will present the details of implementing the SUT-GSF and examine the effects of filter parameters on the performance of the SUT-GSF. 相似文献
982.
A new tunable cascaded infinite impulse response (IIR) microwave photonic filter is presented, based on a novel configuration in which a semiconductor optical amplifier (SOA) is inserted between two active recirculating delay line (RDL) loops. Due to wavelength conversion with cross-gain modulation (XGM) in SOA, interferences between light beams traveling different paths are canceled, ensuring a stable transmission. By employing this configuration, a cascaded IIR microwave photonic filter is firstly achieved. The free spectral range (FSR) and the Q factor are both increased significantly by adopting “vernier effect” technique in the IIR filter. The structure is also tunable by adjusting the length of one RDL loop. 相似文献
983.
Meredith Tromble 《Foundations of Chemistry》2009,11(1):51-60
This paper explores the use of chemical symbolism in works by the new media artist Sonya Rapoport, with a focus on the pivotal
Cobalt series from the late 1970s. These works, drawings on computer printouts generated by research at the Lawrence Berkeley Laboratory,
respond to experiments in nuclear chemistry. They mark the beginning of three productive decades in which Rapoport produced
a variety of images related to chemistry in her work. She states, “I looked for authentic research projects that were interesting
to me, preferably with captivating pictorial subject matter. Then came the creative chaotic process of resolving a cohesive
product that combined scientific research with art concept.” Rapoport had an unusual degree of access to scientific materials
through her husband, organic chemist Henry Rapoport, a faculty member at the University of California, Berkeley. At the time
of production, these works were outside mainstream art world interests and they have received little critical attention. This
paper examines the development of Rapoport’s images and places her use of chemical references in context in her lifetime of
work.
相似文献
Meredith TrombleEmail: |
984.
Syms RR 《Analytical and bioanalytical chemistry》2009,393(2):427-429
Mass filters for miniature mass spectrometers are now being constructed using three-dimensional microfabrication techniques.
Crossed-field, travelling-wave, time-of-flight, quadrupole and cylindrical ion-trap filters have all been demonstrated, with
steadily increasing mass range and mass resolution. This paper reviews the range of available devices and the state of the
art. 相似文献
985.
Digital bioanalysis 总被引:3,自引:1,他引:2
Digital microfluidics has recently emerged as a new paradigm in the world of lab-on-a-chip technology. A wide variety of bioanalyses
have been successfully implemented in this format. This paper reviews the various techniques that have been adapted to digital
microfluidic systems, and the current state of the field.
Figure A multiplexed digital microfluidic device. Six analytical platforms are wired in series, allowing multiple independent analyses
to be performed simultaneously from a single set of controls. 相似文献
986.
This paper is devoted to the discussion of filters in residuated lattices. The lattice structure of filters in residuated lattice was established. It is proved that the set of all filters forms a distributive lattice. Also, the concept of prime filter in residuated lattice was proposed and some equivalent conditions about prime filter were given. 相似文献
987.
Gaiao Eda N Martins VL Lyra Wda S de Almeida LF da Silva EC Araújo MC 《Analytica chimica acta》2006,570(2):283-290
The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H3PO4 in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H3PO4, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection. 相似文献
988.
The digitisation
of a real disc
having radius
and centre
consists of all integer points inside
, i.e.,
In this paper we show that there are
different (up to translations) digitisations of discs having radius
. More formally,
The result is of interest in the area of digital image processing because it describes how large the impact of the object
position can be on its digitisation. 相似文献
989.
An analytical method for the determination of UV filter substances in fish tissue has been developed and validated using benzophenone-3,
3-(4-methylbenzylidene)-camphor, 2-ethylhexyl-2-cyano-3,3-diphenyl-2-propenoate and 2-ethylhexyl 3-(methoxyphenyl)-2-propenoate
as target analytes. The fish fillets were homogenised and extracted by Soxhlet extraction. The extracts were run through a
clean-up process including gel permeation chromatography followed by solid-phase extraction. Quantification of the compounds
was performed using liquid chromatography with tandem mass spectrometric detection. Blank fish as well as spiked blank fish
were analysed to validate the analytical method. The analytical method developed has the multiple advantages of enabling separation,
simultaneous identification and quantification of each of the four selected compounds in a single run. Contamination of blank
samples and abnormally high concentrations in spiked samples were avoided by taking extensive precautions during the fish
preparation procedure. The method was validated in accordance with internationally accepted criteria, such as specificity,
accuracy and repeatability. The combination of LC with tandem mass spectrometry ensures a high level of specificity. The accuracy
of the method was reported as the mean recovery rate for the analytes in the sample matrix. Mean recoveries were in the range
86–108%. The precision is expressed as the relative standard deviation, and in all but one of the cases was 20% or below.
The accuracy of the method allows residue analyses to be performed on biological matrices at ng/g levels. The determined limit
of quantification for each analyte was 8 ng/g fish. For all spiking levels ≥8 ng/g, relative standard deviations were ≤ 20%. 相似文献
990.
Christian E. Willert 《Experiments in fluids》2006,41(1):135-143
The performance of three implementations of pinhole-based camera models for use in common light-sheet imaging arrangements is investigated on the background of application to particle image velocimetry (PIV) and Doppler global velocimetry (DGV). Calibration data obtained from translated planar calibration targets was found to yield camera attitude within 0.1° on four different test cases with object distance varying as little as 2% depending on the choice of camera model. Camera calibration using data from a single image of coplanar points is considered a viable alternative to manual triangulation of camera positions but is restricted to off-normal viewing directions.
相似文献
Christian E. WillertEmail: |