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161.
John Blackwell Robin A. Chivers Genaro A. Gutierrez Amit Biswas 《Journal of Macromolecular Science: Physics》2013,52(1-4):39-59
This paper describes x-ray analysis of the structure of a group of wholly aromatic thermotropic liquid crystalline copolyesters, focusing on two systems: condensation copolymers of 4-hydroxy-benzoic acid (HBA) and 2-hydroxy–6-naphthoic acid; and of HBA, 2,6-dihydroxy-naphthalene, and terephthalic acid. The fiber diagrams of these copolymers contain a series of aperiodic meridional maxima that shift in position with the monomer ratio. We have shown that these characteristics are predicted by a structure consisting of an array of chains of completely random monomer sequence. The positions of the maxima are predicted by a simple model in which the monomers are represented by points, separated from their neighbors by the appropriate monomer lengths. Use of atomic models for the monomers leads to prediction of both the positions and the intensities of the maxima. Calculations for nonrandom sequence distribution show that all but minimal blockiness can be ruled out. From the breath of the meridional maximum at d = 2.1 Å it is possible to estimate the correlation or persistence length for the stiff chain conformation in the solid state. 相似文献
162.
Amit Pratap Singh 《辐射效应与固体损伤》2013,168(1):44-49
In this work, the thermal conductivity variation due to pit formation and surface roughness in nanometer-thick semiconducting films has been studied. It is shown that the thermal conductivity of thin films is reduced due to the presence of these effects in the films. This reduction in thermal conductivity is dependent on film thickness. The present analysis has been done on GaAs nanometer-thick films using the available experimental data. 相似文献
163.
In this article we consider the following class of three point boundary value problem and use monotone iterative technique to derive some sufficient conditions of existence. Examples are included to illustrate the effectiveness of the proposed results. We consider both well ordered and reverse ordered upper and lower solutions. 相似文献
164.
AbstractThe effect of initial orientation on twinning micro-mechanisms during tensile deformation of commercially pure titanium has been studied using micro focus X-ray diffraction and electron back scatter diffraction (EBSD) in a scanning electron microscope. Three orientations A, B and C obtained from a rolled and annealed block of commercially pure titanium were deformed in uniaxial tension till failure and the tested specimens were characterised with regard to bulk texture, microstructure and crystal orientation mapping using EBSD. Orientation B along the transverse direction in ND-TD plane exhibits higher strength and lower strain hardening compared to orientations A and C along the rolling direction in TD-RD and ND-RD plane, respectively. This is attributed to different texture of sample B compared to samples A and C leading to dissimilar twinning micro-mechanisms and characteristic variation in nature of twinning. It is observed that limited twin nucleation and prominent lateral growth plays a dominant role in orientation B while multiple twin nucleation with significant non-Schmid behaviour is dominant for the other two orientations. It is proposed from this study that conventional factors associated with twin formation like Schmid factor play a main role in twin nucleation and propagation, however, growth or lateral thickening of the twins is explained by elastic stiffness variation across twins and their parent grains. 相似文献
165.
In this work a numerical investigation has been carried out to study the effect of g-jitter on zero-gravity (0ge) opposed flow spreading flame over thin solid fuels. For comparison simulations have also been carried out for normal gravity (1ge) downward spreading flames. G-jitter is emulated by gravity modulation of sinusoidal (Age sin(2πt/Tge)) gravity perturbation (g-perturbation) of a particular time-period (Tge) and amplitude (Age) over a selected base gravity level (0ge or 1ge). The response of flames at 0ge base gravity and at 1ge base gravity was different to the imposed g-perturbation. While at 0ge the mean and the amplitude of the oscillatory flame spread rate (FSR) magnified with increase in the time period of g-perturbation, interestingly for the 1ge flame a maximum mean FSR and oscillation amplitude occurs at certain perturbation time period. Further, at very small perturbation time-periods (Tge) the FSR at 1ge was lower than the steady state FSR. The amplitude of oscillatory FSR increased with increase in perturbation amplitude (Age). However, the 0ge flame which is little affected (compared to 1ge flame) at small perturbation amplitude (Age) is affected severely at large perturbation amplitude (Age). Both the gas phase and fuel pyrolysis (or fuel response) follow perturbation signal with a lag but fuel pyrolysis is more sluggish and lags behind gas phase. The phase lag between fuel pyrolysis and gas increases at smaller time-periods (Tge) and tends to enhance the effect of external perturbation whereas at larger time-periods (Tge) this lag inhibits the effect of external perturbation. 相似文献
166.
Aavishkar A. Patel Shraddha Sharma Amit Dutta 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(9):1-6
We study the dynamics of edge states of the two dimensional BHZ Hamiltonian in a ribbon geometry following a sudden quench to the quantum critical point separating the topological insulator phase from the trivial insulator phase. The effective edge state Hamiltonian is a collection of decoupled qubit-like two-level systems which get coupled to bulk states following the quench. We notice a pronounced collapse and revival of the Lochschmidt echo for low-energy edge states illustrating the oscillation of the state between the two edges. We also observe a similar collapse and revival in the spin Hall current carried by these edge states, leading to a persistence of its time-averaged value. 相似文献
167.
Yogesh Patil Ramesh Shingare Amit Choudhari Dhiman Sarkar Balaji Madje 《Journal of heterocyclic chemistry》2019,56(2):434-442
In the present investigation, a series of 4‐((3‐(trifluoromethyl)‐5,6‐dihydro‐[1,2,4]triazolo[4,3‐a]pyrazin‐7(8H)‐yl)methyl)benzenamine analogs 6a–o were synthesized and characterized by IR, NMR (1H and 13C), and mass spectra. All newly synthesized compounds 6a–o were prepared under conventional and microwave irradiation methods. These compounds obtained in higher yields and in shorter reaction times in the microwave irradiation method when compared with the conventional method. Synthesized compounds 6a–o were inspected for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Ra using an established XTT reduction menadione assay. Among the screened compounds, 6i (IC50: 1.82 μg/mL), 6j (IC50: 1.02 μg/mL), and 6k (IC50: 1.59 μg/mL) showed excellent activity. Furthermore, compound 6i showed MIC90 value of 16.02 μg/mL. In summary, the results indicate the identification of some novel, selective, and specific inhibitors against M. tuberculosis that can be explored further for the potential antitubercular drug. 相似文献
168.
Garratt-Braverman cyclization has been employed to synthesize a series of dihydroisofuran fused phenanthridine derivatives. The established protocol proposes a simpler synthetic alternative to have access to these therapeutically relevant cytotoxic scaffolds. Single crystal X-ray data unambiguously confirmed the structures of the synthesized phenanthridine derivatives. UV–Vis absorption titration with calf-thymus DNA followed by fluorescence-based competitive ethidium bromide displacement assay established the synthesized target compounds as potent DNA-intercalating agents with intrinsic binding constant of the range 103-105. Results obtained from the molecular docking further justified the spectroscopically obtained results. 相似文献
169.
Mohammad Bodiuzzaman Atanu Ghosh Korath Shivan Sugi Abhijit Nag Esma Khatun Babu Varghese Ganesan Paramasivam Sudhadevi Antharjanam Ganapati Natarajan Thalappil Pradeep 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):195-200
Two ligand‐protected nanoscale silver moieties, [Ag46(SPhMe2)24(PPh3)8](NO3)2 and [Ag40(SPhMe2)24(PPh3)8](NO3)2 (abbreviated as Ag46 and Ag40, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag32S24P8, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag14 and a completely new core, Ag8, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT). 相似文献
170.
Debasish Manna Basudeb Maji Soumyashree A. Gangopadhyay Kurt J. Cox Qingxuan Zhou Benjamin K. Law Ralph Mazitschek Amit Choudhary 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(19):6351-6355
Several genome engineering applications of CRISPR‐Cas9, an RNA‐guided DNA endonuclease, require precision control of Cas9 activity over dosage, timing, and targeted site in an organism. While some control of Cas9 activity over dose and time have been achieved using small molecules, and spatial control using light, no singular system with control over all the three attributes exists. Furthermore, the reported small‐molecule systems lack wide dynamic range, have background activity in the absence of the small‐molecule controller, and are not biologically inert, while the optogenetic systems require prolonged exposure to high‐intensity light. We previously reported a small‐molecule‐controlled Cas9 system with some dosage and temporal control. By photocaging this Cas9 activator to render it biologically inert and photoactivatable, and employing next‐generation protein engineering approaches, we have built a system with a wide dynamic range, low background, and fast photoactivation using a low‐intensity light while rendering the small‐molecule activator biologically inert. We anticipate these precision controls will propel the development of practical applications of Cas9. 相似文献