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131.
Ablikim M Bai JZ Ban Y Bian JG Cai X Chen HF Chen HS Chen HX Chen JC Chen J Chen YB Chi SP Chu YP Cui XZ Dai YS Diao LY Deng ZY Dong QF Du SX Fang J Fang SS Fu CD Gao CS Gao YN Gu SD Gu YT Guo YN Guo YQ Guo ZJ Harris FA He KL He M Heng YK Hu HM Hu T Huang GS Huang XT Ji XB Jiang XS Jiang XY Jiao JB Jin DP Jin S Jin Y Lai YF Li G Li HB Li HH Li J Li RY Li SM Li WD Li WG Li XL Li XN Li XQ Li YL Liang YF Liao HB Liu BJ Liu CX Liu F Liu F Liu HH Liu HM Liu J Liu JB Liu JP Liu Q Liu RG Liu ZA Lou YC 《Physical review letters》2006,97(20):202002
Using a data sample of 58 x 10(6) J/psi decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of eta and eta' in J/psi to phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag the eta and eta' decays. No signals are found for the invisible decays of either eta or eta', and upper limits at the 90% confidence level are determined to be 1.65 x 10(-3) for the ratio B(eta-->invisible)/B(eta --> gamma gamma) and 6.69 x 10(-2) for B(eta' --> invisible)/B(eta' --> gammagamma). These are the first searches for eta and eta' decays into invisible final states. 相似文献
132.
Zhongyan Li Xingde Dai Yuanan Diao Jianguo Xin 《Journal of Fourier Analysis and Applications》2010,16(2):155-176
Let A be any 2×2 real expansive matrix. For any A-dilation wavelet ψ, let
[^(y)]\widehat{\psi}
be its Fourier transform. A measurable function f is called an A-dilation wavelet multiplier if the inverse Fourier transform of
(f[^(y)])(f\widehat{\psi})
is an A-dilation wavelet for any A-dilation wavelet ψ. In this paper, we give a complete characterization of all A-dilation wavelet multipliers under the condition that A is a 2×2 matrix with integer entries and |{det }(A)|=2. Using this result, we are able to characterize the phases of A-dilation wavelets and prove that the set of all A-dilation MRA wavelets is path-connected under the L
2(ℝ2) norm topology for any such matrix A. 相似文献
133.
Diao J Young L Kim S Fogarty EA Heilman SM Zhou P Shuler ML Wu M DeLisa MP 《Lab on a chip》2006,6(3):381-388
We have developed a prototype three-channel microfluidic chip that is capable of generating a linear concentration gradient within a microfluidic channel and is useful in the study of bacterial chemotaxis. The linear chemical gradient is established by diffusing a chemical through a porous membrane located in the side wall of the channel and can be established without through-flow in the channel where cells reside. As a result, movement of the cells in the center channel is caused solely by the cells chemotactic response and not by variations in fluid flow. The advantages of this microfluidic chemical linear gradient generator are (i) its ability to produce a static chemical gradient, (ii) its rapid implementation, and (iii) its potential for highly parallel sample processing. Using this device, wildtype Escherichia coli strain RP437 was observed to move towards an attractant (e.g., l-asparate) and away from a repellent (e.g., glycerol) while derivatives of RP437 that were incapable of motility or chemotaxis showed no bias of the bacteria's distribution. Additionally, the degree of chemotaxis could be easily quantified using this assay in conjunction with fluorescence imaging techniques, allowing for estimation of the chemotactic partition coefficient (CPC) and the chemotactic migration coefficient (CMC). Finally, using this approach we demonstrate that E. coli deficient in autoinducer-2-mediated quorum sensing respond to the chemoattractant l-aspartate in a manner that is indistinguishable from wildtype cells suggesting that chemotaxis is insulated from this mode of cell-cell communication. 相似文献
134.
In this paper, we consider a weak viscoelastic equation with internal time-varying delay in a bounded domain. By introducing suitable energy and Lyapunov functionals, under suitable assumptions, we establish a general decay result for the energy. This work generalizes and improves earlier results in the literature.
相似文献
$$\begin{aligned} u_{tt}(x, t)-\triangle u(x, t)+\alpha(t) \int_{0}^{t}g(t-s)\triangle u(x, s)ds+\mu u_{t}\bigl(x, t-\tau(t)\bigr)=0 \end{aligned}$$
135.
采用液相共沉淀法成功合成Y2(WO4)3,利用高、低温X射线衍射方法研究Y2(WO4)3的结构及其负热膨胀性能,发现液相共沉淀法制得的Y2(WO4)3与固相反应法制得的Y2(WO4)3具有一致的Pnca空间群正交结构和相差不大的晶胞参数和体积(经TOPAS软件计算),二者的本征体热膨胀系数分别为-18.8×10-6℃-1(液相法)和-19.5×10-6℃-1(固相法)。液相共沉淀法相对传统固相化学反应法,具有减少合成循环次数和降低反应温度的优点。这证明该法制备稀土钨酸盐类负膨胀材料是可行的。 相似文献
136.
Single-wall carbon nanotubes (SWNTs) chemically assembled on gold substrates were employed as electrodes to investigate the charge transfer process between SWNTs and the underlying substrates. Cyclic voltammetry (CV) indicates that the assembled SWNTs allow electron communication between a gold electrode and the redox couple in solution, though the SWNTs are linked directly onto the insulating monolayer of 11-amino-n-undecanethiol (AUT) on the Au substrate. An electron transfer (ET) mechanism, which contains an electron tunneling process across the AUT monolayer, is proposed to explain the CV behavior of Au/AUT/SWNT electrodes. Electrochemical measurements show that the apparent electron tunneling resistance, which depends on the surface density of assembled SWNTs, has apparent effects similar to those of solution resistance on CV behavior . The theory of solution resistance is used to describe the apparent tunneling resistance. The experimental results of the dependence of ET parameter psi on the potential scan rate upsilon are in good agreement with the theoretical predictions. Kinetic studies of the chemical assembly of SWNTs by atomic force microscopic (AFM), electrochemical, and Raman spectroscopic methods reveal that two distinct assembly kinetics exist: a relatively fast step that is dominated by the surface reaction, and a successive slow step that is governed by bundle formation. 相似文献
137.
Adsorption, vibration, and diffusion of O atoms on Rh low-index and (711) stepped defective surfaces
Diao ZY Hao C Wang ZX Dong CC Pang XH 《The journal of physical chemistry. B》2005,109(25):12467-12473
The adsorption, vibration, and diffusion of O atoms on Rh(100), Rh(111), Rh(110), and Rh(711) surfaces were studied using the 5-parameter Morse potential (5-MP) of interaction between an adatom and a metal surface cluster. Our theoretical calculations provide information about adsorption sites, adsorption geometry, binding energy, and eigenvibration. Our results agreed very well with experimental results. Four major results follow. First, the theoretical calculation showed that on the Rh(100) surface the 4-fold hollow site is the only adsorption site. Second, on the O-Rh(111) system, the 3-fold hollow site is the stable adsorption site. Third, on the Rh(110) surface at low coverage, the O atom is adsorbed preferably on the pseudo-3-fold site, while with increasing coverage, the O atom is adsorbed not only on the pseudo-3-fold site but also on the long bridge site. Last, as for the Rh(711) stepped surface, the 3-fold site on the (111) step is metastable, whereas the 4-fold sites on the (100) terrace are stable, which enables the O atoms to diffuse easily from the 3-fold to the 4-fold site at low coverage. Therefore, the O atoms are adsorbed preferrably on the stable 4-fold sites of the (100) terrace and then later as coverage increases on the metastable 3-fold site of the (110) step. 相似文献
138.
139.
140.
ZHANG Duan-Ming ZHONG Zhi-Cheng HAN Xiang-Yun YAN Wen-Sheng SUN Hong-Zhang YANG Feng-Xia ZHENG Ke-Yu WEI Nian LI Zhi-Hua 《理论物理通讯》2005,43(5):855-857
In this paper, the relation between the dielectric properties and the
lattice distortion in the phase coexistence region is discussed using a phase statistical distribution model, and in the rhombohedral phase region the two connection equations on the dielectric properties and the lattice distortion are established. Particularly, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics, and the fitting value of the volume fraction of the tetragonal phase
VT to composition x in the equation is determined. Further, the fitting results are well consistent with the related experimental data. It involves more profound physical process than relation between the dielectric properties and composition x. 相似文献