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951.
952.
Du J Carl M Bydder M Takahashi A Chung CB Bydder GM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2010,207(2):304-311
We describe the use of two-dimensional ultrashort echo time (2D UTE) sequences with minimum TEs of 8 μs to image and quantify cortical bone on a clinical 3T scanner. An adiabatic inversion pulse was used for long T(2) water and fat signal suppression. Adiabatic inversion prepared UTE acquisitions with varying TEs were used for T(2) measurement. Saturation recovery UTE acquisitions were used for T(1) measurement. Bone water concentration was measured with the aid of an external reference phantom. UTE techniques were evaluated on cadaveric specimens and healthy volunteers. A signal-to-noise ratio of around 30, contrast-to-noise ratio of around 27/20 between bone and muscle/fat were achieved in tibia in vivo with a nominal voxel size of 0.23 × 0.23 × 6.0 mm(3) in a scan time of 5 min. A mean T(1) of 223 ± 11 ms and mean T(2) of 390 ± 19 μs were found. Mean bone water concentrations of 23.3 ± 1.6% with UTE and 21.7 ± 1.3% with adiabatic inversion prepared UTE sequences were found in tibia in five normal volunteers. The results show that in vivo qualitative and quantitative evaluation of cortical bone is feasible with 2D UTE sequences. 相似文献
953.
Sin KK Chan CP Pang TH Seydack M Renneberg R 《Analytical and bioanalytical chemistry》2006,384(3):638-644
Nanocrystals of the fluorogenic precursor fluorescein diacetate (FDA) were applied as labels in order to improve on the assay
sensitivity achieved in our previous studies. Each FDA nanocrystal can be converted into ∼2.6×106 fluorescein molecules, which is useful for improving immunoassay sensitivity and limits of detection. NeutrAvidin was simply
adsorbed onto the surface of the FDA nanocrystals, which were coated with distearoylglycerophosphoethanolamine (DSPE) modified
with amino(poly(ethylene glycol))(PEG(2000)-Amine) as an interface for coupling biomolecules. This can be applied to detect
different kinds of analytes that are captured by corresponding biotinylated biomolecules in different bioanalytical applications.
The applicability of the NeutrAvidin-labeled nanocrystals was demonstrated in an immunoassay using the labeled avidin–biotin
technique. Biotinylated antibody and FDA-labeled avidin were applied to the assay sequentially. The performance was compared
with the traditional sandwich-type assay for mouse immunoglobulin G detection. Following the immunoreaction, the nanocrystals
were released by hydrolysis and dissolution instigated by adding a large volume of organic solvent/sodium hydroxide mixture.
The limit of detection was lower (by a factor of 2.5–21) and the sensitivity was (3.5–30-fold) higher than immunoassays using
commercial labeling systems (FITC and peroxidase). This study shows that using fluorescent nanocrystals in combination with
the avidin–biotin technique can enhance assay sensitivity and provide a lower limit of detection without requiring long incubation
times as in enzyme-based labels. 相似文献
954.
In this paper, a digital photoelastic system was employed to observe the stress distribution generated by an ultrasonic wave
impinged at the edge of a strip. According to the classical photoelastic theory, gray level distribution of the photoelastic
fringe patterns was formulated and expressed in the form of
, where J0 is the zeroth-order Bessel function. This new technique is called the time-averaged photoelastic method. To verify the proposed
method, the distribution of
was superimposed onto the distribution of gray level of the experimentally obtained photoelastic fringe pattern caused by
standing wave only. Except regions near the center of fringes, well-matched results were found. 相似文献
955.
** Email: benzaouia{at}ucam.ac.ma A new methodology of the partial eigenstructure assignment bystate feedback via linear matrix inequality (LMI) is extendedto obtain a solution of the constrained regulator problem forlinear continuous-time and discrete-time systems by using theLMI formulation. 相似文献
956.
Reconstruction of dynamic contrast enhanced magnetic resonance imaging of the breast with temporal constraints 总被引:1,自引:0,他引:1
A number of methods using temporal and spatial constraints have been proposed for reconstruction of undersampled dynamic magnetic resonance imaging (MRI) data. The complex data can be constrained or regularized in a number of different ways, for example, the time derivative of the magnitude and phase image voxels can be constrained separately or jointly. Intuitively, the performance of different regularizations will depend on both the data and the chosen temporal constraints. Here, a complex temporal total variation (TV) constraint was compared to the use of separate real and imaginary constraints, and to a magnitude constraint alone. Projection onto Convex Sets (POCS) with a gradient descent method was used to implement the diverse temporal constraints in reconstructions of DCE MRI data. For breast DCE data, serial POCS with separate real and imaginary TV constraints was found to give relatively poor results while serial/parallel POCS with a complex temporal TV constraint and serial POCS with a magnitude-only temporal TV constraint performed well with an acceleration factor as large as R=6. In the tumor area, the best method was found to be parallel POCS with complex temporal TV constraint. This method resulted in estimates for the pharmacokinetic parameters that were linearly correlated to those estimated from the fully-sampled data, with Ktrans,R=6=0.97 Ktrans,R=1+0.00 with correlation coefficient r=0.98, kep,R=6=0.95 kep,R=1+0.00 (r=0.85). These results suggest that it is possible to acquire highly undersampled breast DCE-MRI data with improved spatial and/or temporal resolution with minimal loss of image quality. 相似文献
957.
Kevin M. Wright Joshua Warner Luca Venturi Robert B. Piggott Simon Donell Brian P. Hills 《Magnetic resonance imaging》2010
Image contrast is calculated by inputting experimental 2D T1–T2 relaxation spectra into the ODIN software interface. The method involves characterising a magnetic resonance imaging pulse sequence with a “relaxation signature” which describes the sensitivity of the sequence to relaxation and is independent of sample parameters. Maximising (or minimising) the overlap between the experimental 2D T1–T2 relaxation spectra and the relaxation signature can then be used to maximise image contrast. The concept is illustrated using relaxation signatures for the echo planar imaging and Turbo spin-echo imaging sequences, together with in-vitro 2D T1–T2 spectra for liver and cartilage. 相似文献
958.
在样品池条件下,应用脉冲激光的泵浦-检测技术,研究了Rb(6~2D)激发态原子与H_2反应碰撞生成的RbH分子的振转能级的布居数密度分布及平均转动能、振动能、平动能的相对比值.发现RbH(X~1∑~+)只有v=0,1上有布居.转动带分布轮廓与池温下的统计分布接近,得到RbH的Boltzmann转动温度稍低于池温,而振动温度高.v=1和v=0上的布居数之比约为0.69,从而得到RbH(X~1∑~+)上平均转动能和平均振动能,由反应的有效能得到平均平动能,这三种能量的相对比值f_R:f_V: 相似文献
959.
In this paper we demonstrate the presence of CdBr2 and cadmium aggregates in KBr matrix during Czochralski growth of KBr crystals. The chemical decomposition of CdBr2 due to high temperature of crystallisation and reformation of cadmium bromide seems to be responsible for this effect. 相似文献
960.
H.M. Ali M.M. Abou-Mesalam M.M. El-Shorbagy 《Journal of Physics and Chemistry of Solids》2010,71(1):51-55
Titanium oxide inorganic ion exchange material was synthesized by hydrolysis with water and ammonia solution. Structural feature of the synthesized titanium oxide was analyzed using X-ray diffraction, X-ray fluorescence and infrared spectrometer technique. Tentative formula of titanium oxide was determined and written as TiO2·0.58H2O. Titanium oxide films were deposited on glass substrates by means of an electron beam evaporation technique at room temperature from bulk sample. The films were annealed at 250, 350, 450, and 550 °C temperatures. Transmittance, reflectance, optical energy gap, refractive index and extinction coefficient were investigated. The transmittance values of 85% in the visible region and 88% in the near infrared region have been obtained for titanium oxide film annealed at 550 °C. Kubelka-Munk function was used to evaluate the absorption coefficient which was used to determine the optical band gap. It was found that the optical band gap increases with increasing annealing temperature whereas the refractive index and extinction coefficient decreases. 相似文献