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991.
Two dimensional particle-in-cell simulations show that laser channeling in millimeter-scale underdense plasmas is a highly nonlinear and dynamic process involving longitudinal plasma buildup, laser hosing, channel bifurcation and self-correction, and electron heating to relativistic temperatures. The channeling speed is much less than the linear group velocity of the laser. The simulations find that low-intensity channeling pulses are preferred to minimize the required laser energy but with an estimated lower bound on the intensity of I approximately 5x10(18) W/cm(2) if the channel is to be established within 100 ps. The channel is also shown to significantly increase the transmission of an ignition pulse. 相似文献
992.
Tzoufras M Lu W Tsung FS Huang C Mori WB Katsouleas T Vieira J Fonseca RA Silva LO 《Physical review letters》2008,101(14):145002
A theory that describes how to load negative charge into a nonlinear, three-dimensional plasma wakefield is presented. In this regime, a laser or an electron beam blows out the plasma electrons and creates a nearly spherical ion channel, which is modified by the presence of the beam load. Analytical solutions for the fields and the shape of the ion channel are derived. It is shown that very high beam-loading efficiency can be achieved, while the energy spread of the bunch is conserved. The theoretical results are verified with the particle-in-cell code OSIRIS. 相似文献
993.
994.
Hideki Katayanagi Bhim P. Kafle Takanori Mori Yasuhiro Takabayashi Yoshihiro Kubozono 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(9):1590-1598
The photoion yield spectra of an endohedral metallofullerene Pr@C82 were measured in the photon energy range of 100-150 eV by using time-of-flight mass spectrometry. Parent ions Pr@C82+, Pr@C822+ and Pr@C823+ were observed in the mass spectra. The photoion yield spectra of Pr@C822+ showed a broad peak at 120-140 eV that was assigned to the 4d-4f giant dipole resonance of the encapsulated Pr atoms. Absolute photoabsorption cross sections of Pr@C82 were evaluated from the photoion yield spectra to be 37±12 Mb at 110 eV (off-resonance) and 52±13 Mb at 130 eV (on-resonance). These cross sections of Pr@C82 were compared with the results of Ce@C82, the only metallofullerene whose photoionization properties have ever been studied near the 4d edge of the encapsulated metal atom. The enhancement of photoabsorption due to the giant resonance was found to be similar in Pr@C82 and Ce@C82, but there are marked differences in the peak shapes, which can be explained as due to interference effects between the fullerene cage and the encapsulated metal atoms. 相似文献
995.
A. Sagisaka H. Daido S. Nashima S. Orimo K. Ogura M. Mori A. Yogo J. Ma I. Daito A.S. Pirozhkov S.V. Bulanov T.Zh. Esirkepov K. Shimizu M. Hosoda 《Applied physics. B, Lasers and optics》2008,90(3-4):373-377
We have observed simultaneously both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction
with a 5-μm thick titanium target. In order to control the proton acceleration and THz radiation, we have changed the duration
of the amplified spontaneous emission (ASE) preceding the main pulse generated by the high-intensity Ti:sapphire laser. A
fast proton beam with the maximal energy of ∼ 490 keV has been realized by reducing the duration of the ASE. Simultaneously,
an intense emission of THz radiation is observed for various ASE durations. We propose the antenna mechanism for the THz radiation,
according to which the fast electrons moving along the target surface emit the low-frequency electromagnetic wave.
PACS 52.25.Os; 52.38.Kd; 52.50.Jm 相似文献
996.
Koichi Terashima Akihito Tanabe Kaoru Mori Junko Nakatsuru Manabu Ikemoto 《Applied Surface Science》2008,254(19):6165-6167
We fabricated Ge-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) by using replacement gate process and selective epitaxial growth. In our method, thin Ge layers were selectively grown on the channel region of MOSFETs after the removal of a sacrificial gate stack structure and the etching of the channel region. Ge layers with a smooth surface and a good morphology could be obtained by using the thin Si0.5Ge0.5 buffer layer. Dislocations were observed in the epitaxial layers and near the interface between the epitaxial layer and the substrates. We consider that these dislocations degrade the device performance. Although the electrical characteristics of the obtained MOSFETs need further improvement, our method is one of the promising candidates for the practical fabrication process of Ge-channel MOSFETs. 相似文献
997.
Hiroshi Nakano Masahiro Mori Yorihiko Tsunoda Susumu Matsuo 《Journal of magnetism and magnetic materials》2008
A kink was observed near 20 kOe in the field dependence of the magnetization in a single-grained α-Mn without a magnetic hysteresis below the Neel temperature in an accurate magnetization measurement below 80 kOe. It was observed along [1 0 0], [1 1 0] and [1 1 1] crystallographic directions. The field dependence of the magnetization above 40 kOe extrapolates to positive finite magnetization at null field. The kink suggests a weak metamagnetism induced by the external magnetic field. A small but clear anisotropy was observed between the weak-field susceptibilities along [1 0 0] and [1 1 0]/[1 1 1] directions. A previously reported large susceptibility anomaly was not affirmed between 90 and 270 kOe. 相似文献
998.
Shuichi Iwata Yusuke Yamada Toru Takashima Hideki Mori 《ournal of non Newtonian Fluid Mechanics》2008,151(1-3):30
The enhancement of bubble rising velocity was experimentally investigated by mechanically applying an oscillating pressure to a single small air bubble (e.g., 1 mm3) in a viscoelastic fluid. For shear-thinning fluids, the cyclic change in bubble diameter induced by the oscillating pressure generates a continuous strong local flow near the bubble surface. Consequently, the apparent liquid viscosity is reduced and the bubble rising velocity increases by 400 times or more compared to the case without oscillating pressure. However, for a Newtonian fluid, almost no effect was observed with oscillating pressure. Time-series data of the longitudinal and horizontal bubble diameters were obtained experimentally using a stroboscope and a video system, and these data were used to estimate the local shear rate and the local shear viscosity. The increase in bubble rising velocity estimated from the shear viscosity behavior agreed well with the experimental data. Additionally, a periodic change in the bubble shape from a sphere at the maximum bubble size to a cusped shape at the minimum bubble size was observed under strong oscillatory pressure. 相似文献
999.
Hideharu Mori Masato Sawada Tomohiro Higuchi Koichi Hasebe Nobuo Otsuka Minoru Terano 《Macromolecular rapid communications》1999,20(5):245-250
The surface atomic structure of MgCl2 crystalline particles and MgCl2‐supported Ziegler catalysts was observed by means of high resolution transmission electron microscopy. Step‐terrace surface structures, characteristic of the structure of the MgCl2 crystal, are found in the observed images of MgCl2 particles. The observation of the structure of MgCl2‐supported Ziegler catalysts shows that the MgCl2 crystals are severely deformed by the processes of catalyst preparation. Due to the preparation procedure used the structure of the catalyst changes from crystalline to amorphous. 相似文献
1000.
Kazukiyo Nagai Miyuki Mori Tetsuya Watanabe Tsutomu Nakagawa 《Journal of Polymer Science.Polymer Physics》1997,35(1):119-131
The poly(1-trimethylsilyl-1-propyne) (PMSP) has the potential to be an important membrane gas separation material due to the fact that it has the highest gas permeability of all polymeric membranes. One problem with PMSP is a decrease in the gas permeability with age. In order to understand the aging processes, we studied the change in free volume and the molecular motions of the PMSP and its membranes modified with 1-phenyl-1-propyne (PP) structures; that is, a copolymer and a blend of PMSP and PPP. During aging, the unrelaxed volume of the PMSP membrane was relaxed, and the molecular motion of carbons dropped, suggesting that the decrease in the microvoids caused a tighter chain packing. The copolymer and blend membrane had stable permeability compared to the PMSP. In particular, the addition of a small amount of the PP structure provided excellent stability with high gas permeability. A decrease in the unrelaxed volume of modified membranes was hardly observed with age; however, the molecular motion of some carbons slightly changed. This change did not affect the gas permeability. In this case, a larger unrelaxed volume was probably a dominant factor in the gas permeation of the PMSP rich membranes relative to the molecular motion in the T1 measurement. © 1997 John Wiley & Sons, Inc. 相似文献