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991.
D. Sen J. S. Melo J. Bahadur S. Mazumder S. Bhattacharya G. Ghosh D. Dutta S. F. D’Souza 《The European physical journal. E, Soft matter》2010,31(4):393-402
Morphological transformation during evaporation-induced self-assembly of a mixed colloidal suspension in micrometric droplets
has been investigated. It has been demonstrated that a buckling-driven shape transition of drying droplets of mixed colloidal
suspension takes place during evaporation-induced self-assembly. Further, it is also shown that the distortion modulations
get significantly amplified with enhancement in volume fraction of anisotropic soft colloidal component of the mixed colloids.
It has been argued that the reduction in elastic modulus of formed shell, at the boundary of a drying droplet, and the anisotropic
nature of one of the colloidal components facilitate the deformation process. Hierarchical structures of these assembled colloidal
grains have been probed using electron microscopy and scattering techniques. 相似文献
992.
Swapankumar Ghosh Damodaran Divya Kottayilpadi C. Remani Thadathil S. Sreeremya 《Journal of nanoparticle research》2010,12(5):1905-1911
Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from
cerium(III) nitrate solution at different temperatures in the range 35–80 °C. The activation energy for growth of CeO2 nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained
from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated
the formation of highly crystalline CeO2 particles in narrow size range. CeO2 nanocrystals precipitated at 35 °C were further annealed at temperatures in the range 300–700 °C. The activation energy for
crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism
of crystal growth during the precipitation and annealing. 相似文献
993.
994.
N. Nimje S. Dubey S. K. Ghosh 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(2):223-231
The present paper is aimed to the exploration of modulational amplification in transversely magnetised diffusive semiconductors.
By considering that the origin of modulational interaction lies in the third-order optical susceptibility c(3)\chi^{(3)} arising from the nonlinear diffusion current density and using coupled mode theory, an analytical investigation of frequency
modulational interaction between co-propagating laser beams and internally generated acoustic mode is presented. We have studied
the steady state and transient amplification characteristics of modulated waves arising in the transversely magnetised semiconductor
plasmas. The effect of carrier heating adds new dimensions to the present study. The heating effect reduces the required threshold
amplitude of wave and enhances steady-state as well as transient gain of the generated acoustic mode. 相似文献
995.
We report the formation of H3+ by proton coagulation in methanol under the impact of low energy Ar(8+) projectiles. Our time-of-flight coincidence measurements with CH3OD establish that the H3+ formation arises from intramolecular bond rearrangement of the methyl group. We have performed ab initio quantum chemical calculations that show the preferred pathway for C-H3 bond cleavage. Fragmentation of organic molecules like methanol under impact of highly charged ions is suggested as an alternative mechanism of H3+ formation in outer space. 相似文献
996.
Ghosh AK Ghoshal D Zangrando E Ribas J Chaudhuri NR 《Dalton transactions (Cambridge, England : 2003)》2006,(12):1554-1563
Three new polymeric squarato-bridged manganese complexes {[Mn(H(2)O)(2)(bpe)(sq)].bpe.H(2)O}(n) (1), [Mn(2)(H(2)O)(4)(phen)(2)(sq)(2)](n) (2) and [Mn(2)(H(2)O)(2)(phen)(4)(sq)].(sq).8(H(2)O) (3) [bpe, 1,2-bis(4-pyridyl)ethane; phen, 1,10-phenanthroline; sq, squarate dianion] have been synthesized and characterized by single crystal X-ray diffraction analysis and variable temperature magnetic studies. Complex 1 is a 2D rectangular grid-like structure, achieved through flexible bpe bridging ligands and squarate dianions. On the other hand the use of chelating phen instead of bpe gives rise to a 1D polymeric chain in complex 2 and to a dinuclear entity in 3. In all the three complexes weak interactions play a vital role in stabilizing the solid-state structure. Variable temperature (2-300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in all the complexes. 相似文献
997.
Ramakrishna G Jose DA Kumar DK Das A Palit DK Ghosh HN 《The journal of physical chemistry. B》2006,110(20):10197-10203
Femtosecond transient absorption spectroscopy has been employed to understand the excited state dynamics of [Ru(bpy)(2)Sq](+) (I; bpy is 2,2'-bipyridyl, and Sq is the deprotonated species of the semiquinone form of 1,2-dihydroxy benzene) and its derivatives, a widely studied near-infrared (NIR) active electrochromic dye. Apart from the well-defined dpi(Ru) --> pi(bpy)-based metal-to-ligand charge transfer (MLCT) transition bands at approximately 480 nm, this class of molecules generally shows another dpi(Ru) --> pi(Sq)(SOMO)-based intense MLCT band at around 900 nm, which is known to be redox active and bleaches reversibly upon a change in the oxidation state of the coordinated dioxolene moiety. To have better insight into the photoinduced electron transfer dynamics associated with this MLCT transition, detailed investigations have been carried out on exciting this MLCT band at 800 nm. Immediately after photoexcitation, bleach at 900 nm has been observed, whose recovery is found to follow a triexponential function with major contribution from the ultrafast component. This ultrafast component of approximately 220 fs has been ascribed to the S(1) to S(0) internal conversion process. In addition to the bleach, we have detected two transient species absorbing at 730 and 1000 nm with a formation time approximately 220 fs for both species. The excited state lifetimes for these two transient species have been measured to be 1.5 and 11 ps and have been attributed to excited singlet ((1)MLCT) and triplet ((3)MLCT) states, respectively. Transient measurements carried out on the different but analogous derivatives (II and III) have also shown similar recovery dynamics except that the rate for the internal conversion process has increased with the decrease in the S(1) to S(0) energy gap. The observed results are consistent with the energy gap law for nonradiative decay from S(1) to S(0). 相似文献
998.
Reddy BM Lakshmanan P Loridant S Yamada Y Kobayashi T López-Cartes C Rojas TC Fernandez A 《The journal of physical chemistry. B》2006,110(18):9140-9147
The thermal stability of a nanosized Ce(x)Zr(1-x)O2 solid solution on a silica surface and the dispersion behavior of V2O5 over Ce(x)Zr(1-x)O2/SiO2 have been investigated using XRD, Raman spectroscopy, XPS, HREM, and BET surface area techniques. Oxidative dehydrogenation of ethylbenzene to styrene was performed as a test reaction to assess the usefulness of the VOx/Ce(x)Zr(1-x)O2/SiO2 catalyst. Ce(x)Zr(1-x)O2/SiO2 (1:1:2 mol ratio based on oxides) was synthesized through a soft-chemical route from ultrahigh dilute solutions by adopting a deposition coprecipitation technique. A theoretical monolayer equivalent to 10 wt % V2O5 was impregnated over the calcined Ce(x)Zr(1-x)O2/SiO2 sample (773 K) by an aqueous wet impregnation technique. The prepared V2O5/Ce(x)Zr(1-x)O2/SiO2 sample was subjected to thermal treatments from 773 to 1073 K. The XRD measurements indicate the presence of cubic Ce0.75Zr0.25O2 in the case of Ce(x)Zr(1-x)O2/SiO2, while cubic Ce0.5Zr0.5O2 and tetragonal Ce0.16Zr0.84O2 in the case of V2O5/Ce(x)Zr(1-x)O2/SiO2 when calcined at various temperatures. Dispersed vanadium oxide induces more incorporation of zirconium into the ceria lattice, thereby decreasing its lattice size and also accelerating the crystallization of Ce-Zr-O solid solutions at higher calcination temperatures. Further, it interacts selectively with the ceria portion of the composite oxide to form CeVO4. The RS measurements provide good evidence about the dispersed form of vanadium oxide and the CeVO4 compound. The HREM studies show the presence of small Ce-Zr-oxide particles of approximately 5 nm size over the surface of amorphous silica and corroborate with the results obtained from other techniques. The catalytic activity studies reveal the ability of vanadium oxide supported on Ce(x)Zr(1-x)O2/SiO2 to efficiently catalyze the ODH of ethylbenzene at normal atmospheric pressure. The remarkable ability of Ce(x)Zr(1-x)O2 to prevent the deactivation of supported vanadium oxide leading to stable activity in the time-on-stream experiments and high selectivity to styrene are other important observations. 相似文献
999.
The temporally overlapping, ultrafast electronic and vibrational dynamics of a model five-coordinate, high-spin heme in a nominally isotropic solvent environment has been studied for the first time with three complementary ultrafast techniques: transient absorption, time-resolved resonance Raman Stokes, and time-resolved resonance Raman anti-Stokes spectroscopies. Vibrational dynamics associated with an evolving ground-state species dominate the observations. Excitation into the blue side of the Soret band led to very rapid S2 --> S1 decay (sub-100 fs), followed by somewhat slower (800 fs) S1 --> S0 nonradiative decay. The initial vibrationally excited, non-Boltzmann S0 state was modeled as shifted to lower energy by 300 cm(-1) and broadened by 20%. On a approximately 10 ps time scale, the S0 state evolved into its room-temperature, thermal distribution S0 profile largely through VER. Anti-Stokes signals disappear very rapidly, indicating that the vibrational energy redistributes internally in about 1-3 ps from the initial accepting modes associated with S1 --> S0 internal conversion to the rest of the macrocycle. Comparisons of anti-Stokes mode intensities and lifetimes from TRARRS studies in which the initial excited state was prepared by ligand photolysis [Mizutani, T.; Kitagawa, T. Science 1997, 278, 443, and Chem. Rec. 2001, 1, 258] suggest that, while transient absorption studies appear to be relatively insensitive to initial preparation of the electronic excited state, the subsequent vibrational dynamics are not. Direct, time-resolved evaluation of vibrational lifetimes provides insight into fast internal conversion in hemes and the pathways of subsequent vibrational energy flow in the ground state. The overall similarity of the model heme electronic dynamics to those of biological systems may be a sign that the protein's influence upon the dynamics of the heme active site is rather subtle. 相似文献
1000.
The secant map of an immersion sends a pair of points to the direction of the line joining the images of the points under the immersion. The germ of the secant map of a generic codimension-c immersion $X\!\!:{\mathbb R}^n \to {\mathbb R}^{n+c}The secant map of an immersion sends a pair of points to the direction of the line joining the images of the points under
the immersion. The germ of the secant map of a generic codimension-c immersion
X:\mathbb Rn ? \mathbb Rn+cX\!\!:{\mathbb R}^n \to {\mathbb R}^{n+c} at the diagonal in the source is a
\mathbb Z2{\mathbb Z}_2 stable map-germ
\mathbb R2n ? \mathbb Rn+c-1{\mathbb R}^{2n} \to {\mathbb R}^{n+c-1} in the following cases: (i) c≥ 2 and (2n,n + c − 1) is a pair of dimensions for which the
\mathbb Z2{\mathbb Z}_2 stable germs of rank at least n are dense, and (ii) for generically immersed surfaces (i.e., n = 2 and any c≥ 1). In the latter surface case the
A\mathbb Z2{\mathcal A}^{{\mathbb Z}_2}-classification of germs of secant maps at the diagonal is described and it is related to the
A{\mathcal A}-classification of certain singular projections of the surfaces. 相似文献