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71.
The CARI (clinical amplitude/velocity reconstruction imaging) technique is a new ultrasonography for better detection of the breast cancer. The method uses the mammography-like positioning of the breast and a reference structure to assess the changes of sound velocity in the screened region. In this work, we present a first attempt to simulate the CARI technique using finite element time-domain (FETD) wave propagation. The CARI sensitivity to the size, shape and location of the tumors is investigated via the simulations on 2D and 3D breast models. Small lesions can be detectable under a suitable spatial resolution. 3D simulations agree with the quantitative results of the 2D case. Moreover, the FETD approximation is proving to be a simple, but robust tool in the CARI simulation. 相似文献
72.
Aaron Dodd Allan McKinley Martin Saunders 《Journal of Physics and Chemistry of Solids》2007,68(12):2341-2348
Nanoparticulate TiO2 is of interest for a variety of technological applications, including optically transparent UV-filters and photocatalysts for the destruction of chemical waste. The successful use of nanoparticulate TiO2 in such applications requires an understanding of how the synthesis conditions effect the optical and photocatalytic properties. In this study, we have investigated the effect of heat treatment temperature on the properties of nanoparticulate TiO2 powders that were synthesised by solid-state chemical reaction of anhydrous TiOSO4 with Na2CO3. It was found that the photocatalytic activity increased with the heat treatment temperature up to a maximum at 600 °C and thereafter declined. In contrast, the optical transparency decreased monotonically with the heat treatment temperature. These results indicate that solid-state chemical reaction can be used to prepare powders of nanoparticulate TiO2 with properties that are optimised for use as either optically transparent UV-filters or photocatalysts. 相似文献
73.
Reactivities of mixed organozinc and mixed organocopper reagents. Part 13 Kinetic study for phosphine‐catalyzed acylation of alkylarylzincs and effect of residual group on the transfer rate of alkyl group 下载免费PDF全文
Özgen Ömür Pekel 《Journal of Physical Organic Chemistry》2016,29(4):190-195
Kinetics of reactions of di‐n‐butylzinc, n‐Bu2Zn, and mixed n‐butyl(substituted phenyl)zinc reagents and n‐Bu(functional group (FG)?C6H4)Zn with benzoyl chloride in the presence of tri‐n‐butylphosphine have been investigated. Reaction rates of transferable n‐butyl group have been determined in tetrahydrofuran at 0 °C to compare the transfer rate of n‐butyl group in homo and mixed diorganozincs. Rate law is consistent with a third‐order reaction, which is first order in diorganozinc, benzoyl chloride, and n‐Bu3P, and a mechanism was proposed. The lower reaction rate of n‐BuPhZn than that of n‐Bu2Zn and negative reaction constant in Hammett plot are in accordance with the carbanionic charge of transferable n‐butyl group in the acylation reaction. These findings support the hypothesis that the reaction rate of transferable group, RT, changes depending upon the residual group, RR, in RRRTZn reagents. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
74.
Weis J Ahlström H Hlavcak P Häggman M Ortiz-Nieto F Bergman A 《Magnetic resonance imaging》2009,27(1):87-93
Purpose
To minimize user and vendor dependence of the spectrum processing of prostate spectra, to measure the ratio of choline (Cho) plus creatine (Cr) to citrate (Cit) in the prostate tissue of normal volunteers and cancer patients, and to compare the results with pathologic findings after radical prostatectomy.Materials and methods
Four healthy volunteers and 13 patients with prostate cancer were measured. Measurements were performed using two-dimensional magnetic resonance spectroscopic imaging (MRSI) and endorectal coil. A standard vendor's spectrum processing approach has been modified. An original feature of this methodology was the combination of vendor-optimized and user-independent spectrum preprocessing in the scanner and user-independent quantitation in the environment of an MRUI software package. (Cho+Cr)/Cit ratio was used for the classification of prostate tissue. Results were compared with histopathology after radical prostatectomy.Results
Eight of 13 cancer patients were classified as suspicious or very suspicious for cancer at spectroscopy, three were ambiguous for cancer and two patients were evaluated as false negative. A considerable overlap of metabolite ratios at various Gleason score was found.Conclusion
The proposed spectrum processing has the potential to improve the accuracy and user independency of the (Cho+Cr)/Cit quantitation. This study confirmed the previous results that a considerable overlap of (Cho+Cr)/Cit ratios exists at various Gleason score levels. 相似文献75.
Simo Huotari Tuomas Pylkkänen J. Aleksi Soininen Joshua J. Kas Keijo Hämäläinen Giulio Monaco 《Journal of synchrotron radiation》2012,19(1):106-113
X‐ray Raman scattering (XRS) provides a bulk‐sensitive method of measuring the extended X‐ray absorption fine structure (EXAFS) of soft X‐ray absorption edges. Accurate measurements and data analysis procedures for the determination of XRS‐EXAFS of polycrystalline diamond are described. The contributions of various angular‐momentum components beyond the dipole limit to the atomic background and the EXAFS oscillations are incorporated using self‐consistent real‐space multiple‐scattering calculations. The properly extracted XRS‐EXAFS oscillations are in good agreement with calculations and earlier soft X‐ray EXAFS results. It is shown, however, that under certain conditions multiple‐scattering contributions to XRS‐EXAFS deviate from those in standard EXAFS, leading to noticeable changes in the real‐space signal at higher momentum transfers owing to non‐dipole contributions. These results pave the way for the accurate application of XRS‐EXAFS to previously inaccessible light‐element systems. 相似文献
76.
Yusuf Öztürk Asım Egemen Yılmaz Evrim Çolak Ekmel Özbay 《Photonics and Nanostructures》2012,10(4):624-631
Planar metamaterials, which have incident to normal plane excitation unlike SRR-type structures and that are easily fabricated in multilayer form, have received great interest in recent years. In this paper, one-dimensional and polarization independent circular fishnet metamaterials and their equivalent discontinuous slab-pair modeling for tuning resonance frequencies are introduced. After the numerical and experimental demonstration of the inclusions, the standard retrieval characterization methods and the correspondent/related backward-wave propagation observation are realized in order to check the physical explanation mentioned in the paper. In addition, a detailed phase analysis is performed in order to demonstrate the application of the suggested structure as a phase compensator. 相似文献
77.
J. Kurpeta G. Lhersonneau A. Płochocki J.C. Wang P. Dendooven A. Honkanen M. Huhta M. Oinonen H. Penttilä K. Peräjärvi J.R. Persson J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):449-460
The decay of neutron-rich isotope 113Ru obtained as on-line mass separated product of proton-induced fission has been investigated by γγ coincidence and spectrum
multiscaling measurements. Decay schemes for both low- and high-spin isomers of 113Ru have been constructed. The level scheme of 113Rh is considerably extended. Systematics of the lowest-lying rhodium levels is smooth. The picture of shape coexistence established
for neutron-rich Rh isotopes near-neutron midshell is confirmed with the observation of a K = 1/2 deformed band, with its 3/2+ state at 600 keV being the lowest-lying level and of probable 7/2+
and 5/2+
band members. A large fraction of β feeding is found to populate high-lying levels in 113Rh. The GT strength in 113Rum decay is significantly larger than for the decay of 113Rug and of lighter rhodium isotopes.
Received: 18 January 2001 / Accepted: 14 January 2002 相似文献
78.
Per JensenSteven S. Wesolowski Nicole R. BrinkmannNancy A. Richardson Yukio YamaguchiHenry F. Schaefer III P.R. Bunker 《Journal of Molecular Spectroscopy》2002,211(2):254-261
The potential energy surface and dipole moment surfaces of the ã4A2 electronic state of CH2+ are calculated ab initio using an augmented correlation-consistent polarized valence quadruple-ζ (aug-cc-pVQZ) basis set, with the incorporation of dynamical correlation using the coupled cluster method with single and double excitations and perturbatively connected triple excitations [CCSD(T)]. We use these surfaces in the MORBID program system to calculate rotation and rotation-vibration term values for ã-state CH2+, CD+2, and CHD+ and to simulate the rotation and rotation-vibration absorption spectrum of CH2+ in the ã4A2 electronic state. Our work is motivated by studies of CH2+ that use the Coulomb explosion imaging technique and by the goal of predicting spectra that may be obtained from discharge sources. Although the ã state is the lowest-lying excited state above the X?/Ã ground state pair, it turns out to be relatively high-lying, and we determine that Te(ã)=30447.5 cm−1. The equilibrium bond angle for ã-state CH2+ is only 77.1°; as a result the asymmetric top κ value is close to 0, and the molecule is equally far from the oblate and prolate symmetric top limits in this electronic state. 相似文献
79.
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