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921.
S. Songara M.K. Patra M. Manoth L. Saini V. Gupta G.S. Gowd S.R. Vadera N. Kumar 《Journal of photochemistry and photobiology. A, Chemistry》2010,209(1):68-73
Pure and (0.5–3 at%) vanadium doped TiO2 nanoparticles have been synthesized by wet chemical method. The as synthesized materials have been characterized by using XRD, atomic force microscope (AFM), Raman, EPR and UV–vis spectroscopy techniques. From XRD studies, both pure as well as vanadium doped TiO2 have been found to show pure anatase phase. The value of lattice constant c is smaller in doped TiO2 as compared to undoped and has been found to decrease with increase in vanadium concentration. AFM studies show formation of spherical particles with particle size ~23 nm in all the samples. Photochromic behavior of these materials has been studied by making their films in alkyd resin. Vanadium doped TiO2 films show reversible change in color from beige-yellow to brownish violet on exposure to UV light. The mechanism of coloration and bleaching process has been discussed. 相似文献
922.
Terbium ion doped MO–Al2O3 (M = Mg, Ca, Sr and Ba) series phosphors have been synthesized through combustion technique and their luminescence properties have been studied and compared. Terbium ion in different phosphors has shown different fluorescence properties due to the presence of different ratios of Tb3+ and Tb4+ states in different samples. The UV/Visible absorption and XPS techniques have been used to probe the existence of Tb3+ and Tb4+ states. The host sensitive 4f–5d and the charge transfer transitions enabled the use of terbium ion as an indicator of the structure. 相似文献
923.
B. Bhushan A. Basumallick N.Y. Vasanthacharya S. Kumar D. Das 《Solid State Sciences》2010,12(7):1063-1069
Multiferroic nanoparticles of Bi1?xSrxFeO3 (x = 0, 0.01, 0.03, 0.05 and 0.07) were prepared by a facile sol–gel route and the variation of their structural, optical, dielectric and magnetic properties on strontium concentration has been studied. XRD and TEM results confirm the phase purity of the samples having high degree of crystallinity and monodispersity. The average particle size shows an exponential decline with increase in Sr concentration. A shape transformation from a multifaceted polygon to a spherical one has been observed as Sr concentration in the sample increases to 5%. In the second derivative FTIR spectra, the intensity of vibration peak at ~593 cm?1 that is characteristic of rhombohedral BiFeO3 is seen to decrease after Sr doping. All the samples showed typical M–H behavior of a ferromagnet with saturation magnetization achieved within an applied magnetic field of 10 kOe. The sample with 3% Sr substitution displayed saturation and remanent magnetization values 1.37 emu/g and 0.32 emu/g respectively that are highest among all the samples studied. Presence of exchange coupling produced due to interaction between the antiferromagnetic core and ferromagnetic shell is also observed in all Bi1?xSrxFeO3 nanoparticles. 相似文献
924.
In the Ni(II)–S(IV)–O2 system in the region of pH > 8.4, both Ni(II) and S(IV) are simultaneously autoxidized, and when sulfur is consumed fully NiOOH precipitates. At pH > 8.4, ethanol has no effect on the rate, whereas ammonia strongly inhibits the reaction when pH > 7.0. The kinetics of the reaction, in both the presence and the absence of ethanol, is defined by the rate law where k is the rate constant, KO is the equilibrium constant for the adsorption of O2 on ? Ni(OH)2 particle surface. In ammonia buffer, the factor F is defined by where K, KOH, K1, K2, K3, and K4 are the stability constants of NiSO3, NiOH+, Ni(NH3)2+, Ni(NH3), Ni(NH3), and Ni(NH3), respectively. In unbuffered medium, the factor F reduces to The values of k and Ksp were found to be (1.3 ± 0.08) × 10?1 s?1 and (4.2 ± 3.5) × 10?16, respectively, at 30°C. A nonradical mechanism that assumes the adsorption of both SO32? and O2 on the ? Ni(OH)2 particle surface has been proposed. At pH ≤ 8.2, Ni(II) displays no catalytic activity for sulfur(IV)‐autoxidation and it is also not oxidized to NiOOH. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 464–478, 2010 相似文献
925.
Lu W Singh AK Khan SA Senapati D Yu H Ray PC 《Journal of the American Chemical Society》2010,132(51):18103-18114
Prostate cancer is the second leading cause of cancer-related death among the American male population, and the cost of treating prostate cancer patients is about $10 billion/year in the United States. Current treatments are mostly ineffective against advanced-stage prostate cancer and are often associated with severe side effects. Driven by these factors, we report a multifunctional, nanotechnology-driven, gold nano-popcorn-based surface-enhanced Raman scattering (SERS) assay for targeted sensing, nanotherapy treatment, and in situ monitoring of photothermal nanotherapy response during the therapy process. Our experimental data show that, in the presence of LNCaP human prostate cancer cells, multifunctional popcorn-shaped gold nanoparticles form several hot spots and provide a significant enhancement of the Raman signal intensity by several orders of magnitude (2.5 × 10(9)). As a result, it can recognize human prostate cancer cells at the 50-cells level. Our results indicate that the localized heating that occurs during near-infrared irradiation can cause irreparable cellular damage to the prostate cancer cells. Our in situ time-dependent results demonstrate for the first time that, by monitoring SERS intensity changes, one can monitor photothermal nanotherapy response during the therapy process. Possible mechanisms and operating principles of our SERS assay are discussed. Ultimately, this nanotechnology-driven assay could have enormous potential applications in rapid, on-site targeted sensing, nanotherapy treatment, and monitoring of the nanotherapy process, which are critical to providing effective treatment of cancer. 相似文献
926.
Amareshwar Kumar Rai Ce Song Zijing Lin 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,73(5):865-870
An extensive exploration of the conformational space has been carried out to characterize all possible gas phase structures of leucine. A total of 324 unique trial structures for canonical leucine were generated by considering all possible combinations of single bond rotamers. All trial structures were optimized at the B3LYP/6-311G* level of the DFT method. A total of 77 unique and stationary canonical conformers were found. Further, 15 most stable conformers were reoptimized at B3LYP/6-311++G** level and their respective relative energies, vertical ionization energies, hydrogen bonding patterns, rotational constants and dipole moments were calculated. A single point energy calculations for leucine conformers have also been done at both B3LYP/6-311++G(2df, p) and MP2/6-311++G(2df, p) levels. The good agreement between our estimates of rotational constants for two most stable conformers and available experimental measurements supports the reliability of the B3LYP/6-311++G** level of theory for describing the conformational behavior of leucine molecule. The proton affinity and gas phase basicity were also determined. Using the statistical approach, conformational distributions at various temperatures have also been performed and analyzed. Vibrational spectra were also calculated. It is also observed that zwitterions of leucine are not stable in gas phase. 相似文献
927.
Three new ditopic receptors 3a-c based on thiacalix[4]arene of 1,3 alternate conformation possessing two different complexation sites have been designed and synthesized for both soft and hard metal ions. The imino nitrogens bind soft metal ion (Ag+/Pb2+/Cu2+) and the crown moiety binds K+ ion. The preliminary investigations show that 3a-c behave as ditopic receptors for Ag+/K+, Pb2+/K+, and Cu2+/K+ ions, respectively. In all the three receptors it was observed that the formation of 3a·Ag+/3b·Pb2+/3c·Cu2+ complex triggers the decomplexation of K+ ion from crown moiety and acts as a gateway, which regulates the binding of alkali metal to crown moiety. Thus, allosteric binding between metal ions ‘switch off’ the recognition ability of crown ether ring. 相似文献
928.
A wide variety of [1,2,3]triazolo[5,1-c][1,4]benzoxazines were synthesized through palladium-copper catalyzed reactions of 1-azido-2-(prop-2-ynyloxy)benzene with aryl/vinyl iodides. A plausible reaction mechanism has also been proposed. 相似文献
929.
Atul Kumar Nagaraj M. Gowda Sushma Gaikwad Archana Pundle 《Journal of photochemistry and photobiology. B, Biology》2009,97(2):65
Penicillin V acylase (PVA), a member of newly evolved Ntn-hydrolase superfamily, is a pharmaceutically important enzyme to produce 6-aminopenicillanic acid. Active site characterization of recently purified monomeric PVA from Rhodotorula aurantiaca (Ra-PVA), the yeast source, showed the involvement of serine and tryptophan in the enzyme activity. Modification of the protein with serine and tryptophan specific reagents such as PMSF and NBS showed partial loss of PVA activity and substrate protection. Ra-PVA was found to be a multi-tryptophan protein exhibiting one tryptophan, in native and, four in its denatured condition. Various solute quenchers and substrate were used to probe the microenvironment of the putative reactive tryptophan through fluorescence quenching. The results obtained indicate that the tryptophan residues of Ra-PVA were largely buried in hydrophobic core of the protein matrix. Quenching of the fluorescence by acrylamide was collisional. Acrylamide was the most effective quencher amongst all the used quenchers, which quenched 71.6% of the total intrinsic fluorescence of the protein, at a very less final concentration of 0.1 M. Surface tryptophan residues were found to have predominantly more electropositively charged amino acids around them, however differentially accessible for ionic quenchers. Denaturation led to shift in λmax from 336, in native state, to 357 nm and more exposed to the solvent, consequently increase in fluorescence quenching with all quenchers. This is an attempt towards the conformational studies of Ra-PVA. 相似文献
930.
A single-step synthesis for ring-fluorinated 4H-1,4-benzothiazines is reported by the condensation and oxidative cyclization of β-diketones with 2-amino-5-fluorobenzenethiol. The reaction is believed to proceed via an enaminoketone system. 相似文献