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131.
A modified two-aperture speckle shear interferometer that eliminates the contribution of the in-plane component and its derivative to the phase change, and yields a fringe pattern corresponding to the first-order partial derivatives of the out-of-plane displacement component, is reported in this note. In this method, two laterally sheared object points are viewed axially. The wave fields from these points are independently combined at the image plane of the imaging system. 相似文献
132.
B. Gopala Krishna G. Ravi Chandra S. V. Suryanarayana 《Crystal Research and Technology》1992,27(4):569-581
Samples with the nominal composition Bi2Sr2CaCu2Oy with na doped at the Ca site and K doped at the Sr site are prepared by solid state reaction method. From the X-ray diffraction data it is found that all the the samples have exhibited a single phase 2212. The D.C. electrical resistivity data show that for Na-doped samples the Tc (zero) varies from 80 K to 85 K and for K-doped samples it is from 79 K to 82 K. The loss of oxygen from these samples around 400°C was confirmed by high temperature dilatometry. The variation of the thermal expansion coefficient (“α”) with temperature for different alkali dopings are discussed. Also the samples with the nominal composition Bi4Sr3Ca3Cu4−xAgxOy (with x = 0, 0.1, 0.2, 0.3) were studied. 相似文献
133.
Weerasekara A Rinzan M Matsik S Perera AG Buchanan M Liu HC von Winckel G Stintz A Krishna S 《Optics letters》2007,32(10):1335-1337
Terahertz detection using the free-carrier absorption requires a small internal work function of the order of a few millielectron volts. A threshold frequency of 3.2 THz (93 microm or approximately 13 meV work function) is demonstrated by using a 1 x 10(18) cm(-3) Si-doped GaAs emitter and an undoped Al(0.04)Ga(0.96)As barrier structure. The peak responsivity of 6.5 A/W, detectivity of 5.5 x 10(8) Jones, and quantum efficiency of 19% were obtained at 7.1 THz under a bias field of 0.7 kV/cm at 6 K, while the detector spectral response range spans from 3.2 to 30 THz. 相似文献
134.
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
135.
Niko Prasetyo Alberto Krishna Ksatria Winning Kusuma La Ode Muhammad Iqbal 《International journal of quantum chemistry》2024,124(1):e27236
The spin component scale MP2/molecular mechanics molecular dynamics simulation investigated the hydration shell formation and hydrated Cd2+ dynamics in the water environment. At the first hydration shell, six water molecules with 2.27 Å for the average distance between water and Cd2+. Dynamical properties were analyzed by computing the water molecule's mean residence time (MRT) in its first and second hydration shells. The MRT of each shell was determined to be 31.8 and 1.92 ps, suggesting the strong influence of Cd2+ in the first hydration shell. The second shell was labile, with an average number of water molecules being 18. Despite the strong interaction between Cd2+ and water molecules in the first shell, the influence of ions in the second hydration shell remained weak. 相似文献
136.
Light‐Directing Omnidirectional Circularly Polarized Reflection from Liquid‐Crystal Droplets 下载免费PDF全文
Dr. Jing Fan Dr. Yannian Li Dr. Hari Krishna Bisoyi Prof. Rafael S. Zola Prof. Deng‐ke Yang Dr. Timothy J. Bunning Prof. David A. Weitz Prof. Quan Li 《Angewandte Chemie (International ed. in English)》2015,54(7):2160-2164
Constructing and tuning self‐organized three‐dimensional (3D) superstructures with tailored functionality is crucial in the nanofabrication of smart molecular devices. Herein we fabricate a self‐organized, phototunable 3D photonic superstructure from monodisperse droplets of one‐dimensional cholesteric liquid crystal (CLC) containing a photosensitive chiral molecular switch with high helical twisting power. The droplets are obtained by a glass capillary microfluidic technique by dispersing into PVA solution that facilitates planar anchoring of the liquid‐crystal molecules at the droplet surface, as confirmed by the observation of normal incidence selective circular polarized reflection in all directions from the core of individual droplet. Photoirradiation of the droplets furnishes dynamic reflection colors without thermal relaxation, whose wavelength can be tuned reversibly by variation of the irradiation time. The results provided clear evidence on the phototunable reflection in all directions. 相似文献
137.
Light‐Driven Reversible Alignment Switching of Liquid Crystals Enabled by Azo Thiol Grafted Gold Nanoparticles 下载免费PDF全文
Dr. Chenming Xue Jie Xiang Hossein Nemati Dr. Hari Krishna Bisoyi Karla Gutierrez‐Cuevas Dr. Ling Wang Dr. Min Gao Shuang Zhou Prof. Deng‐ke Yang Prof. Oleg D. Lavrentovich Dr. Augustine Urbas Prof. Quan Li 《Chemphyschem》2015,16(9):1852-1856
Stimuli‐directed alignment control of liquid crystals (LCs) with desired molecular orientation is currently in the limelight for the development of smart functional materials and devices. Here, photoresponsive azo thiol (AzoSH) was grafted onto gold nanoparticles (GNPs). The resulting hybrid GNPs were able to homogeneously mix with a commercially available nematic LC host, as evidenced by Cryo‐TEM. Interestingly, the LC nanocomposites were found to undergo reversible alignment transition upon light irradiation as a consequence of the trans–cis photoisomerization of the azo groups on the GNP surface. LC molecules in either planar or bare glass cells were able to change their alignment to vertical upon UV irradiation, while the vertically aligned LC molecules returned to the planar or random orientation under visible irradiation. Neither the azo thiol molecules nor the unfunctionalized GNPs alone promoted the alignment of the LC molecules in the system upon light irradiation. The photoinduced vertical alignment without applied electric or magnetic field was very stable over time and with respect to temperature. Furthermore, an optically switchable device based on the photostimulated reversible alignment control of LCs was demonstrated. 相似文献
138.
Measurement of Large Dipolar Couplings of a Liquid Crystal with Terminal Phenyl Rings and Estimation of the Order Parameters 下载免费PDF全文
NMR spectroscopy is a powerful means of studying liquid‐crystalline systems at atomic resolutions. Of the many parameters that can provide information on the dynamics and order of the systems, 1H–13C dipolar couplings are an important means of obtaining such information. Depending on the details of the molecular structure and the magnitude of the order parameters, the dipolar couplings can vary over a wide range of values. Thus the method employed to estimate the dipolar couplings should be capable of estimating both large and small dipolar couplings at the same time. For this purpose, we consider here a two‐dimensional NMR experiment that works similar to the insensitive nuclei enhanced by polarization transfer (INEPT) experiment in solution. With the incorporation of a modification proposed earlier for experiments with low radio frequency power, the scheme is observed to enable a wide range of dipolar couplings to be estimated at the same time. We utilized this approach to obtain dipolar couplings in a liquid crystal with phenyl rings attached to either end of the molecule, and estimated its local order parameters. 相似文献
139.
Theoretical insights into the relative bonding of normal and abnormal N‐heterocyclic carbenes in [PdCl2(NHCR)2] and [PdCl2(NHCR)(aNHCR)] (R = H,Ph, Mes) 下载免费PDF全文
Krishna K. Pandey 《International journal of quantum chemistry》2016,116(7):537-546
Quantum chemical insights into normal Pd‐C2(NHCR) and abnormal Pd‐C5(aNHCR) bonding, dominated by dispersion interactions in N‐hetereocyclic carbene complexes [PdCl2(NHCR)2] ( I , R = H; II , R = Ph; III , R = Mes (2,4,6‐trimethyl)phenyl)) and [PdCl2(NHCR)(aNHCR] ( IV , R = H; V , R = Ph; VI , R = Mes) have been investigated at DFT and DFT‐D3(BJ) level of theory with particular emphasis on the effects of the noncovalent interactions on the structures and the nature of Pd‐C2(NHCR) and Pd‐C5(aNHCR) bonds. The optimized geometries are good agreement with the experimental values. The Pd‐C bonds are essentially single bond. Hirshfeld charge distributions indicate that the abnormal aNHCR carbene ligand is relatively better electron donor than the normal NHCR carbene ligand. The C2 atom has larger %s contribution along Pd‐C2 bond than the C5 atom along Pd‐C5 bond. As a consequence the Pd‐C2(NHCR) bonds are relative stronger than the Pd‐C5(aNHCR) bonds. Thus, the results of natural hybrid orbital analysis support the key point of the present study. Calculations predict that for bulky substituent (R = Ph, Mes) at carbene, the Pd‐C2(NHCR) bond is stronger than Pd‐C5(aNHCR) bond due to large dispersion energy in [PdCl2(NHCR)2] than in [PdCl2(NHCR)(aNHCR)]. However, in case of non‐bulky substituent with small and almost equal contribution of dispersion energy, the Pd‐C2(NHCR) bond is relative weaker than Pd‐C5(aNHCR) bond. The bond dissociation energies are dependent on the R substituent, the DFT functional and the inclusion of dispersion interactions. Major point of this study is that the abnormal aNHCs are not always strongly bonded with metal center than the normal NHCs. Effects of dispersion interaction of substituent at nitrogen atoms of carbene ligand are found to play a crucial role on estimation of relative bonding strengths of the normal and abnormal aNHCs with metal center. © 2016 Wiley Periodicals, Inc. 相似文献
140.
Gollapalli Venkateswara Rao Santhosh R. Pindi Bollikolla Hari Babu Bala Murali Krishna Khandapu 《Journal of heterocyclic chemistry》2024,61(2):341-346
The present work describes the synthesis and characterization of six related compounds of cloxacillin sodium ( 1 ) viz penicilloic acid of cloxacillin (2) , (3-(2-chlorophenyl)-5-methylisoxazole-4-carbonyl) glycine (Glycine analogue of cloxacillin) (3), CMICAA adduct of cloxacillin (4) , (4S)-2-(carboxy(3-(2-chlorophenyl)-5-methylisoxazole-4-carboxamido) methyl)-3-(2-ethylhexanoyl)-5,5-dimethylthiazolidine-4-carboxylic acid (N-2-ethylhexanoyl penicilloic acid of cloxacillin) ( 5 ), N-Acetylated penicilloic acid of cloxacillin ( 6 ), and Cloxacillin Penicillamide (7) . These related compounds are very essential in the process development of cloxacillin sodium and are used as reference standards to determine the quality of the drug substance. 相似文献