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411.
This paper aims to study the general conditions under which omnidirectional band gaps (OBGs) are achieved by using heterostructure magnetic photonic crystals (HMPCs). These structures contain periodic layers with alternative dielectric permittivity and magnetic permeability. The proposed design offers the stacking of two magnetic photonic crystals (MPCs), where one MPC has Brewster’s angle at TE polarization and another has the angle at TM polarization. The propagation of electromagnetic waves is investigated by means of the transfer matrix method. Also, the total reflection frequency range for any incident angle and polarization is discussed in this paper. As a conclusion, although each MPC has no OBG individually, the proposed HMPC may contain an OBG. The main advantage of the proposed design is that the obtained OBG is independent of the ambient media refractive index. Therefore, it can be used in engineering omnireflectors in integrated photonics. 相似文献
412.
Sadia Ameen S.G. Ansari Minwu Song Young Soon Kim Hyung-Shik Shin 《Superlattices and Microstructures》2009,46(5):745-751
The work reports on the fabrication of a p–n heterojunction structure comprised of polyaniline (PANI) and TiO2 nanoparticles. PANI was deposited by plasma enhanced polymerization on TiO2 thin film substrates. The structural and the crystalline properties demonstrated the coherence and the substantive interaction of the plasma polymerized PANI molecules with the TiO2 nanoparticle thin film. The UV–Vis studies of PANI/TiO2 thin film supported the internalization of PANI with TiO2 nanoparticles due to π–π* transition of the phenyl rings with the lone pair electrons () of the nitrogen atom present in the PANI molecules. The I–V characteristics of the PANI/TiO2 heterojunction structure were obtained in the forward and the reverse biased at applied voltage ranging from −1 V to +1 V with a scan rate of 2 mV/s. The proficient current in the PANI/TiO2 heterojunction structure was attributed to the well penetration of PANI molecules into the pores of the TiO2 nanoparticle thin film. The I–V characteristics ensured an efficient charge movement at the junction of PANI/TiO2 interface and thus, behaved as a typical ohmic system. 相似文献
413.
Nasser A. M. Barakat Kee-Do Woo S. G. Ansari Jung-Ahn Ko Muzafar A. Kanjwal Hak Yong Kim 《Applied Physics A: Materials Science & Processing》2009,95(3):769-776
In the present study, nanofibers consisting of manganese monoxide (MnO), which is hard to prepare because of the chemical
activity of the manganese metal, and the popular Mn3O4 have been synthesized via the electrospinning technique. The nanofibers were obtained by electrospinning of an aqueous sol–gel
consisting of manganese acetate tetra-hydrate and poly(vinyl alcohol). The obtained nanofiber mats were dried in vacuum at
80°C for 24 h and then calcined in argon atmosphere at 900°C for 5 h. According to X-ray diffraction results, the obtained
nanofibers contain 65% MnO. Transmission electron microscope analysis reveals good crystallinity of the produced nanofibers.
UV–visible spectroscopic analysis has indicated that the produced nanofibers have two band-gap energies, 2 and 3.7 eV, which
enhances utilizing of the nanofibers in different applications. 相似文献
414.
The thermo-rheological characteristics of a fumed silica lubricating grease in linear and nonlinear oscillatory experiments have been investigated. The material rheological behavior represents a soft solid being thermo-rheologically complex. There is an abnormal temperature dependency in the range of ??10 to 10 °C which is related to the phase transition of the base oil. The dynamic moduli data in linear viscoelastic envelop (LVE) have been modeled using mode-coupling theory (MCT) in the whole temperature range. Two main relaxation mechanisms can be identified through linear and nonlinear viscoelastic properties related to interaction of the primary particle and its neighbor particles as well as a slow relaxation process which represents the escape of this particle from its “cage”. Finally, it is demonstrated that the dominant yielding process in large amplitude oscillatory experiments can be explained based on either particle cage rupture (consistent with MCT framework) or particle “hopping” out of its cage proposed in soft glassy rheology (SGR) model. It will be discussed that the governing mechanism depends on the applied frequency. 相似文献
415.
Maryam Salajegheh Maryam Kazemipour Mohammad Mehdi Foroghi Mehdi Ansari 《Electroanalysis》2019,31(3):468-476
A different molecularly imprinted composite film with the exploit of computational design is synthesized. The proposed composite is used for electrode modification to determine morphine. The ratio of monomer to template in optimum condition was obtained 4. The modification of the electrode was achieved by electropolymerizing L‐lysine in the presence of morphine on the surface of sodium alginate and activated carbon (SA‐AC) on glassy carbon electrode (GCE). The SA‐AC composite with special surface area suits for making sensitive sensors. Morphine showed an anodic peak in buffer solution of phosphate (pH=6.0) on MIP/SA‐AC/GCE. The optimization of the practical factors on the response and electrochemical behavior of template morphine on the modified electrode were precisely surveyed. The DPV outcomes exhibit high sensitivity for morphine detection within 0.1–1000.0 μM and limit of detection as 48 nM (S/N=3). The application of this disposable sensor in the case of urine samples was quite satisfactory. 相似文献
416.
Golnoush Mirzahosseini Azadeh Manayi Mahnaz Khanavi Maliheh Safavi Ali Salari Alireza Madjid Ansari 《Natural product research》2019,33(11):1687-1690
Centaurea bruguierana subsp. belangerana was extracted by 80% ethanol. The total extract was then partitioned into four fractions including chloroform, ethyl acetate and methanol. Cytotoxic effect of fractions was examined by MTT assay in K562 (chronic myelogenous leukemia), AGS (gastric adenocarcinoma), MCF-7 (breast adenocarcinoma) and SW742 (colon adenocarcinoma) cell lines. The Chloroform fraction, with the lowest LC50 against K-562 cell lines, was partitioned into 14 subfractions and subjected to further purification by reversed-phase (C18) silica gel and sephadex LH-20 column chromatography. Three flavonoids including cirsimaritin, cirsilinelol and eupatilin were isolated for the first time from the species and the structures were confirmed by spectroscopic data. The high selectivity index of the purified flavonoids indicates valuable components with potential few side effects for normal cell lines. However, solubility tests for isolated components indicates the need for novel pharmaceutical dosage forms, in the case for using natural flavonoids as chemotherapeutic agents. 相似文献
417.
In this paper, we consider the system of vector quasi-equilibrium problems with or without involving -condensing maps and prove the existence of its solution. Consequently, we get existence results for a solution to the system of vector quasi-variational-like inequalities. We also prove the equivalence between the system of vector quasi-variational-like inequalities and the Debreu type equilibrium problem for vector-valued functions. As an application, we derive some existence results for a solution to the Debreu type equilibrium problem for vector-valued functions. 相似文献
418.
Whole-field photorefractive holography can be combined with low-coherence interferometry for three-dimensional imaging and other applications, including imaging through turbid media, but the off-axis holographic recording geometry results in a limited field of view when light of low temporal coherence is used. We show that tilting the energy fronts with respect to the wave fronts by use of prisms can eliminate this problem and point out that this approach will be useful for many linear and nonlinear wave-mixing experiments. 相似文献
419.
Ansari MS Rama NH Hussain MT Raza AR 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,(7):1385-1389
Diastereotopy has been investigated in eight different derivatives of 3,4-dihydroisocoumarins by changing the substituent on the pyran ring chiral centre, C-3. A diastereotopic NMR effect is observed for the prochiral methylene protons on the benzopyran ring and the effect is greatly influenced by the pi-electron system of the substituent. The effect is also observed for the substituents, however, the extent of diastereotopy depends upon their nature and the separation of methylene groups from the chiral centre. 相似文献
420.
F. Sadeghi R. Ansari M. Darvizeh 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2016,67(4):80
The present work aims to investigate the mechanical oscillatory behavior of ions, and in particular \({{\rm Li}^{+}, {\rm Na}^{+}, {\rm Rb}^{+}}\) and \({{\rm Cl}^{-}}\) ions, inside a cyclo[(–d-Ala–l-Ala)4–] peptide nanotube using the continuum approximation along with the 6–12 Lennard–Jones (LJ) potential function. Assuming that each peptide unit is comprised of an inner and an outer tube, the van der Waals (vdW) potential energy and interaction force between an ion and a cyclic peptide nanotube (CPN) are determined analytically. With respect to the present formulations, a detailed parametric study is conducted on the vdW potential energy and interaction force distributions by varying the number of peptide units. Employing the conservation of mechanical energy principle, a novel expression for precise evaluation of oscillation frequency is introduced. To verify the accuracy of the proposed frequency expression, the results obtained from energy equation are compared with the ones predicted through solving the equation of motion numerically. The effects of number of peptide units and initial conditions including initial separation distance and velocity on the oscillatory behavior of various ions inside CPNs are explored. Among the considered ions, \({{\rm Cl}^{-}}\) ion is found to generate the highest frequency. According to the potential energy profile, one oscillatory zone for one peptide unit and different oscillatory zones for more than one peptide unit are observed. Numerical results indicate that optimal frequency decreases with increasing the number of peptide units and almost remains unchanged when the number of peptide units exceeds four. 相似文献