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61.
Extensive experimental results are presented to reveal the relaxations of polystyrene surface deformed by rubbing with a velvet
cloth. We found that surface topographic features, such as ditches and ridges created by rubbing, relax at temperatures at
about 20°
C below the bulk glass transition temperature of the polystyrene for a molecular weight of 442 kg/mol, even though we estimate
the Laplace Pressure driving the relaxation to be 1/500 of the yield limit. The relaxation is independent of the thermal history
before the rubbing process, and post rubbing thermal history below 55°
C . In other words, physical-aging processes at 23°
C for up to 7 days and at 50°
C for 2 days, which would have drastic effects on the relaxations of bulk polymers, have little effects on the relaxations
of rubbed surfaces. This is consistent with the mobility enhancement in the surface layer previously reported in the literature. 相似文献
62.
Y. T. Angel Wong Vinicius Martins Dr. Bryan E. G. Lucier Prof. Dr. Yining Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(8):1848-1853
Metal–organic frameworks (MOFs) have shown great potential in gas separation and storage, and the design of MOFs for these purposes is an on-going field of research. Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a valuable technique for characterizing these functional materials. It can provide a wide range of structural and motional insights that are complementary to and/or difficult to access with alternative methods. In this Concept article, the recent advances made in SSNMR investigations of small gas molecules (i.e., carbon dioxide, carbon monoxide, hydrogen gas and light hydrocarbons) adsorbed in MOFs are discussed. These studies demonstrate the breadth of information that can be obtained by SSNMR spectroscopy, such as the number and location of guest adsorption sites, host–guest binding strengths and guest mobility. The knowledge acquired from these experiments yields a powerful tool for progress in MOF development. 相似文献
63.
In this paper, we present a new car-following model by taking into
account the effects of the traffic interruption probability on the
car-following behaviour of the following vehicle. The stability
condition of the model is obtained by using the linear stability
theory. The modified Korteweg--de Vries (KdV) equation is constructed
and solved, and three types of traffic flows in the
headway sensitivity space---stable, metastable, and unstable---are
classified. Both the analytical and simulation results show that the
traffic interruption probability indeed has an influence on driving
behaviour, and the consideration of traffic interruption probability
in the car-following model could stabilize traffic flow. 相似文献
64.
66.
The European Physical Journal A - Efficient neutron transport is a key ingredient to the performance of ultracold neutron (UCN) sources, important to meeting the challenges placed by high precision... 相似文献
67.
Analytic soliton solutions of cubic‐quintic Ginzburg‐Landau equation with variable nonlinearity and spectral filtering in fiber lasers 下载免费PDF全文
Long‐Gang Huang Li‐Hui Pang Pring Wong Yan‐Qing Li Shao‐Yi Bai Ming Lei Wen‐Jun Liu 《Annalen der Physik》2016,528(6):493-503
In fiber lasers, the study of the cubic‐quintic complex Ginzburg‐Landau equations (CGLE) has attracted much attention. In this paper, four families (kink solitons, gray solitons, Y‐type solitons and combined solitons) of exact soliton solutions for the variable‐coefficient cubic‐quintic CGLE are obtained via the modified Hirota method. Appropriate parameters are chosen to investigate the properties of solitons. The influences of nonlinearity and spectral filtering effect are discussed in these obtained exact soliton solutions, respectively. Methods to amplify the amplitude and compress the width of solitons are put forward. Numerical simulation with split‐step Fourier method and fourth‐order Runge‐Kutta algorithm are carried out to validate some of the analytic results. Transformation from the variable‐coefficient cubic‐quintic CGLE to the constant coefficients one is proposed. The results obtained may have certain applications in soliton control in fiber lasers, and may have guiding value in experiments in the future.
68.
Yingbang Yao Bernd Ploss C. L. Mak K. H. Wong 《Applied Physics A: Materials Science & Processing》2010,99(1):211-216
BiFeO3 (BFO) ceramics were prepared by a modified solid-state-reaction method which adopts a higher heating/cooling rate during
the sintering process than usually used. It was found that the calcination temperature T
cal (from 400 to 750°C) does not influence the BFO phase formation, while the sintering temperature T
sin (from 815 to 845°C) dominates the phase purity. The optimum sintering temperature was in the range from 825 to 835°C. The
optimized samples exhibit saturated ferroelectric hysteresis loops with a remnant polarization of 13.2 μC/cm2. The measured piezoelectric coefficient d
33 was 45 pC/N. No remnant magnetization was observed in all of the samples. The pyroelectric properties were studied as a function
of temperature and frequency. A pyroelectric coefficient as high as 90 μC/m2 K was obtained at room temperature in the optimized sample. An abrupt decrease of the pyroelectric coefficient was observed
at temperatures between 70 and 80°C. On the basis of our results, BFO may have the potential for pyroelectric applications. 相似文献
69.
Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical even today. Co-doping is a promising strategy that can be used for effectively tuning the dopant populations, electronic properties, and magnetic properties. It can enhance the solubility of dopants and improve the stability of desired defects. During the past 20 years, significant experimental and theoretical efforts have been devoted to studying the characteristics of co-doping. In this article, we first review the historical development of co-doping. Then, we review a variety of research performed on co-doping, based on the compensating nature of co-dopants. Finally, we review the effects of contamination and surfactants that can explain the general mechanisms of co-doping. 相似文献
70.
Guerrieri F Maccone L Wong FN Shapiro JH Tisa S Zappa F 《Physical review letters》2010,105(16):163602
The Rayleigh diffraction bound sets the minimum separation for two point objects to be distinguishable in a conventional imaging system. We demonstrate sub-Rayleigh resolution by scanning a focused beam--in an arbitrary, object-covering pattern that is unknown to the imager--and using N-photon photodetection implemented with a single-photon avalanche detector array. Experiments show resolution improvement by a factor ~(N-N(max))(?) beyond the Rayleigh bound, where N(max) is the maximum average detected photon number in the image, in good agreement with theory. 相似文献