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181.
Bayard S. Holmes Joo B. Dias Belgacem A. Jaroux Takamitsu Sassa Yasuhiro Ban 《国际流体数值方法杂志》1997,24(12):1307-1319
Finite element and boundary element calculations are combined to predict the flow noise radiated from a 1/10th-scale model of an aerodynamic cover used around the pantograph on a train at 250 km h−1. The solutions of the unsteady air flow over the cover and the resulting sound propagation are divided into two parts in order to keep the problem tractable. First the unsteady fluid flow is solved using large-eddy simulation (LES). The pressure histories on the cover are then used to predict the radiated sound, using a boundary element method to solve the Helmholtz equation. The result thus leans heavily on assumptions about the coupling of the two solutions, the propagation of sound in a disturbed medium and the efficacy of LES. The predicted sound pressure levels are compared with experimental measurements made in an anechoic wind tunnel. © 1997 John Wiley & Sons, Ltd. 相似文献
182.
Nurul Aida Ngah George J. Dias Darryl C. Tong Siti Noor Fazliah Mohd Noor Jithendra Ratnayake Paul R. Cooper Haizal Mohd Hussaini 《Molecules (Basel, Switzerland)》2021,26(23)
Background: Platelet-rich fibrin (PRF) has gained popularity in craniofacial surgery, as it provides an excellent reservoir of autologous growth factors (GFs) that are essential for bone regeneration. However, the low elastic modulus, short-term clinical application, poor storage potential and limitations in emergency therapy use restrict its more widespread clinical application. This study fabricates lyophilised PRF (Ly-PRF), evaluates its physical and biological properties, and explores its application for craniofacial tissue engineering purposes. Material and methods: A lyophilisation method was applied, and the outcome was evaluated and compared with traditionally prepared PRF. We investigated how lyophilisation affected PRF’s physical characteristics and biological properties by determining: (1) the physical and morphological architecture of Ly-PRF using SEM, and (2) the kinetic release of PDGF-AB using ELISA. Results: Ly-PRF exhibited a dense and homogeneous interconnected 3D fibrin network. Moreover, clusters of morphologically consistent cells of platelets and leukocytes were apparent within Ly-PRF, along with evidence of PDGF-AB release in accordance with previously reports. Conclusions: The protocol established in this study for Ly-PRF preparation demonstrated versatility, and provides a biomaterial with growth factor release for potential use as a craniofacial bioscaffold. 相似文献
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184.
Lúcia Brandão Dias Hildeberto E. Cabral 《Journal of Dynamics and Differential Equations》2018,30(1):81-92
We consider the dynamics of an infinitesimal particle under the gravitational action of P primaries of equal masses. These move in an elliptic homographic solution of the P-body problem and the infinitesimal particle moves along the straight line perpendicular to their plane of motion and passing through the common focus of the ellipses. In this work we consider the parametric stability of the infinitesimal mass located at the focus of the ellipses. We construct the boundary curves of the stability/instability regions in the plane of the parameters \(\mu \) and \(\epsilon \), which are the mass of each primary and the eccentricity of the elliptic orbit, respectively. 相似文献
185.
Stability analysis of internally damped rotating composite shafts using a finite element formulation
Safa Ben Arab José Dias Rodrigues Slim Bouaziz Mohamed Haddar 《Comptes Rendus Mecanique》2018,346(4):291-307
This paper deals with the stability analysis of internally damped rotating composite shafts. An Euler–Bernoulli shaft finite element formulation based on Equivalent Single Layer Theory (ESLT), including the hysteretic internal damping of composite material and transverse shear effects, is introduced and then used to evaluate the influence of various parameters: stacking sequences, fiber orientations and bearing properties on natural frequencies, critical speeds, and instability thresholds. The obtained results are compared with those available in the literature using different theories. The agreement in the obtained results show that the developed Euler–Bernoulli finite element based on ESLT including hysteretic internal damping and shear transverse effects can be effectively used for the stability analysis of internally damped rotating composite shafts. Furthermore, the results revealed that rotor stability is sensitive to the laminate parameters and to the properties of the bearings. 相似文献
186.
K. Bescherer J. A. Barnes S. Dias G. Gagliardi H.-P. Loock N. R. Trefiak H. Waechter S. Yam 《Applied physics. B, Lasers and optics》2009,96(1):193-200
Multi-exponential decay waveforms are common occurrences in cavity ring-down spectroscopy and the respective ring-down times
are typically obtained by fitting the ring-down waveform to the sum of exponential decay functions. In phase-shift cavity
ring-down (CRD) spectroscopy the measurement of a single phase angle will not provide sufficient information and needs to
be complemented by either intensity measurements or phase angle measurements at different modulation frequencies. Here, a
formalism analogous to that developed for fluorescence lifetime spectroscopy is adapted to the phase-shift CRD technique and
is tested for two types of waveguide CRD systems: (1) a single-mode fiber cavity in which light is confined by two identical
Fiber Bragg Gratings and (2) a multimode fiber loop. By measuring the phase angle at different modulation frequencies, lifetimes
for up to three different decay processes were obtained. 相似文献
187.
188.
3α-Hydroxyl-7α-(4-pentenoyloxy)-5β-cholanoic acid (5) has been synthesized in four step reactions starting from CDCA. The serendipitous synthesis of methyl 3α-(ethoxycarbonyloxy)-7α-(allyloxycarbonyloxy)-5β-cholanoate (7) has led us to compare the spectroscopic difference of the 7α-(allyloxycarbonyloxy) group versus the 7α-(4-pentenoyloxy) group. The molecular structures of these compounds were confirmed by X-ray crystallography. Methyl 3α-(ethoxycarbonyloxy)-7α-(allyloxycarbonyloxy)-5β-cholanoate was obtained by a method, which may prove useful in the synthesis of 14C-labeled derivatives for metabolic studies. 相似文献
189.
190.
Matilte Halma Kelly Aparecida Dias de Freitas Castro Vanessa Prvot Claude Forano Fernando Wypych Shirley Nakagaki 《Journal of molecular catalysis. A, Chemical》2009,310(1-2):42-50
The first generation anionic iron(III) porphyrin [Fe(TSPP)] and the second generation anionic complexes [Fe(TDFSPP)], [Fe(TCFSPP)], and [Fe(TDCSPP)] were immobilized into three-dimensionally macroporous layered double hydroxide (3DM-LDH), using the direct reconstruction of 3DM-LDH from macroporous mixed oxides MOX or the anionic exchange on DDS intercalated 3DM-LDH. The macroporous layered double hydroxides were obtained at the surface of nanometric polystyrene spheres, which were synthesized by an inverse opal method. Polystyrene was removed after calcination in oxidizing atmosphere, nanostructured mixed oxides (3DM-MOX) were obtained, which after reconstruction give origin to macroporous layered double hydroxide (3DM-LDH). Following metalloporphyrin immobilization, the resulting materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), UV–vis (glycerin mull) spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR), and electron paramagnetic resonance (EPR). Results revealed that the complexes are either immobilized at the surface of the macroporous layered double hydroxide or intercalated between the layers, displacing some dodecylsufate anions. The obtained materials were investigated as catalysts for oxidation reactions, to find out whether they function as cytochrome P-450 models. 相似文献