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991.
U. Köster P. Carbonez A. Dorsival J. Dvorak R. Eichler S. Fernandes H. Frånberg J. Neuhausen Z. Novackova R. Wilfinger A. Yakushev 《The European physical journal. Special topics》2007,150(1):285-291
Refractory elements, i.e. elements with very high melting point and
low vapor pressure, cannot be released in atomic form from an ISOL target.
Therefore most of these elements are presently not available as ISOL beams.
However, when reactive gases are introduced
into the target, they may form volatile compounds with the refractory elements,
allowing for an easier transport to the ion source. Particularly useful are
high-temperature stable fluorides and oxides.
By these chemical evaporation methods so far ISOL beams of the refractory elements
C, Zr, Hf and Ta have been produced. We discuss how ISOL beams of B, Ti, Nb, Mo, Tc,
Ru, W, Re, Os and Ir could be produced in a similar way. 相似文献
992.
Shaolin Liao Ronald J. Vernon 《International Journal of Infrared and Millimeter Waves》2007,28(6):479-490
The newly developed Taylor-Interpolation-FFT (TI-FFT) algorithm dramatically increases the computational speeds for millimeter
wave propagation from a planar (cylindrical) surface onto a “quasi-planar” (“quasi-cylindrical”) surface. Two different scenarios
are considered in this article: the planar TI-FFT is for the computation of the wave propagation from a plane onto a “quasi-planar” surface and the cylindrical TI-FFT is for the computation of wave propagation from a cylindrical surface onto a “quasi-cylindrical” surface. Due to the
use of the FFT, the TI-FFT algorithm has a computational complexity of O(N
2 log2
N
2) for an N × N computational grid, instead of N
4 for the direct integration method. The TI-FFT algorithm has a low sampling rate according to the Nyquist sampling theorem.
The algorithm has accuracy down to −80 dB and it works particularly well for narrow-band fields and “quasi-planar” (“quasi-cylindrical”)
surfaces. 相似文献
993.
Anjan Biswas Swapan Konar Essaid Zerrad 《International Journal of Theoretical Physics》2007,46(1):157-169
The intra-channel collision of optical solitons, with dual-power law nonlinearity, is studied in this paper by the aid of
quasi-particle theory. The perturbation terms that are considered in this paper are the nonlinear gain and saturable amplifiers
along with filters. The suppression of soliton-soliton interaction, in presence of these perturbation terms, is acheived.
The numerical simulations support the quasi-particle theory.
OCIS codes: 060.2310; 060.4510; 060.5530; 190.3270; 190.4370. 相似文献
994.
Measurement of D(d,p) T Reaction Cross Sections in Sm Metal in Low Energy Region (10≤Ed≤20keV) 下载免费PDF全文
WANG Tie-Shan YANG Zhen H. Yunemura A. Nakagawa LV Hui-Yi CHEN Jian-Yong LIU Sheng-Jin J. Kasagi 《中国物理快报》2007,24(11):3103-3106
To study the screening effect of nuclear reactions in metallic environments, the thick target yields, the cross sections and the experimental S(E) factors of the D(d,p)T reaction have been measured on deuterons implanted in Sm metal at 133.2K for beam energies ranging from 10 to 20keV. The thick target yields of protons emitted in the D(d,p) T reaction are measured and compared with those data extrapolated from cross sections and stopping power data at higher energies. The screening potential in Sm metal at 133.2K is deduced tobe 520±56eV. As compared with the value achieved in the gas target, thecalculated screening potential values are much larger. This screening potential cannot be simply interpreted only by the electron screening. Energy dependences of the cross section σ(E) and the experimental S(E) factor for D(d,p)T reaction in Sm metal at 133.2K are obtained, respectively. 相似文献
995.
996.
LUO En & LI WeiHua Department of Applied Mechanics Engineering Sun Yat-sen University Guangzhou China 《中国科学G辑(英文版)》2007,50(3):370-378
According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified way proposed by Luo, some basic principles in the dynamic theory of viscoelastic materials with voids can be estab- lished systematically. In this paper, an important integral relation in terms of con- volutions is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem, but also to derive systemati- cally the complementary functionals for the eight-field, six-field, four-field simpli- fied Gurtin-type variational principles and the potential energy-functional for the two-field one in the dynamic theory of viscoelastic materials with voids by the generalized Legendre transformations given in this paper. Furthermore, with this approach, the intrinsic relationship among various principles can be explained clearly. 相似文献
997.
一维光子晶体缺陷模偏振特性的研究 总被引:3,自引:6,他引:3
利用一维光子晶体的透射率公式,计算出一维光子晶体掺杂后TE波和TM波缺陷模的波长随入射角的响应曲线、缺陷模透射峰随入射角的响应曲线、缺陷模透射峰随入射波长的响应曲线.研究发现,TE波和TM波的缺陷模透射峰均随入射角的增加而向短波方向移动;TE波缺陷模透射峰的半高宽度(FWHM)和峰值随入射角的增加而减小,而TM波缺陷模透射峰的半高宽度(FWHM)和峰值确随入射角的增加而增加;对TM波其波长为λ0的缺陷模也存在明显的“广义布儒斯特角”现象, TE波的缺陷模不存在“广义布儒斯特角”现象. 相似文献
998.
Beniamino Cappelletti Montano Antonio De Nicola 《Journal of Geometry and Physics》2007,57(12):2509-2520
We present a compared analysis of some properties of 3-Sasakian and 3-cosymplectic manifolds. We construct a canonical connection on an almost 3-contact metric manifold which generalises the Tanaka–Webster connection of a contact metric manifold and we use this connection to show that a 3-Sasakian manifold does not admit any Darboux-like coordinate system. Moreover, we prove that any 3-cosymplectic manifold is Ricci-flat and admits a Darboux coordinate system if and only if it is flat. 相似文献
999.
Data assimilation-based parameter estimation can be used to deterministically tune forecast models. This work demonstrates that it can also be used to provide parameter distributions for use by stochastic parameterization schemes. While parameter estimation is (theoretically) straightforward to perform, it is not clear how one should physically interpret the parameter values obtained. Structural model inadequacy implies that one should not search for a deterministic “best” set of parameter values, but rather allow the parameter values to change as a function of state; different parameter values will be needed to compensate for the state-dependent variations of realistic model inadequacy. Over time, a distribution of parameter values will be generated and this distribution can be sampled during forecasts. The current work addresses the ability of ensemble-based parameter estimation techniques utilizing a deterministic model to estimate the moments of stochastic parameters. It is shown that when the system of interest is stochastic the expected variability of a stochastic parameter is biased when a deterministic model is employed for parameter estimation. However, this bias is ameliorated through application of the Central Limit Theorem, and good estimates of both the first and second moments of the stochastic parameter can be obtained. It is also shown that the biased variability information can be utilized to construct a hybrid stochastic/deterministic integration scheme that is able to accurately approximate the evolution of the true stochastic system. 相似文献
1000.
Jean E. Burns 《Foundations of Physics》2007,37(12):1727-1737
Vacuum radiation causes a particle to make a random walk about its dynamical trajectory. In this random walk the root mean
square change in spatial coordinate is proportional to t
1/2, and the fractional changes in momentum and energy are proportional to t
−1/2, where t is time. Thus the exchange of energy and momentum between a particle and the vacuum tends to zero over time. At the end of
a mean free path the fractional change in momentum of a particle in a gas is very small. However, at the end of the mean free
path each particle undergoes an interaction that magnifies the preceding change, and the net result is that the momentum distribution
of the particles in a gas is randomized in a few collision times. In this way the random action of vacuum radiation and its
subsequent magnification by molecular interaction produces entropy increase. This process justifies the assumption of molecular
chaos used in the Boltzmann transport equation. 相似文献