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61.
Kalpana Tomar Gagandeep Kaur Sandeep Verma Gurunath Ramanathan 《Tetrahedron letters》2018,59(41):3653-3656
The tetrapeptide (Bz-Phe(p-NPh2)-l-DOPA(protected)-l-Phe-l-Phe-OMe was designed to incorporate seven phenyl rings so that it’s conformation, self-assembly and application in Hg2+ ions sensing could be studied. Peptide molecules adopted an overlapping β-turn of type III/III conformation in crystals. The peptide showed a highly selective turn-on response towards mercuric ion over other metal ions with a 10-fold enhancement in fluorescence intensity. This intensity change coupled with the selectivity of the peptide towards mercury allowed us to demonstrate simple colorimetric dip sensing of Hg2+ ions. The technique provides a highly selective and effective way to detect Hg2+ ions. The peptide also self-assembled into nanospheres with diameter ranges from 100 to 500?nm. Mercuric ion coordination enabled these peptide nanospheres to aggregate into well-defined nanoparticles. The enhanced fluorescence upon Hg2+ addition demonstrates that peptide scaffolds can be exploited in the development of different selective sensors. 相似文献
62.
We prove that there exists a finite universal Korovkin set with respect to positive spectral contraction operators for a Segal
algebra on a locally compact abelian groupG if and only ifĜ is finite dimensional separable metrizable space. 相似文献
63.
JPC – Journal of Planar Chromatography – Modern TLC - A sensitive, specific, and accurate stability-indicating high-performance thin-layer chromatographic method for the analysis of... 相似文献
64.
Intermolecular stacking in pyrazolo[3,4‐d]pyrimidine‐based pentamethylene‐linked flexible molecules
Kamlakar Avasthi Sheikh M. Farooq Ashish K. Tewari Ashoke Sharon Prakas R. Maulik 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(1):o42-o45
The crystal structures of 1‐{5‐[4,6‐bis(methylsulfanyl)‐2H‐pyrazolo[3,4‐d]pyrimidin‐2‐yl]pentyl}‐6‐methylsulfanyl‐4‐(pyrrolidin‐1‐yl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C22H29N9S3, and 6‐methylsulfanyl‐1‐{5‐[6‐methylsulfanyl‐4‐(pyrrolidin‐1‐yl)‐2H‐pyrazolo[3,4‐d]pyrimidin‐2‐yl]pentyl}‐4‐(pyrrolidin‐1‐yl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C25H34N10S2, which differ in having either a pyrrolidine substituent or a methylsulfanyl group, show intermolecular stacking due to aromatic π–π interactions between the pyrazolo[3,4‐d]pyrimidine rings. 相似文献
65.
Recently measured inelastic X-ray spectra (IXS) of detailed coherent dynamical structure factor S(κ, ω) and hence the equilibrium collective dynamics, of the lightest liquid alkali metal, lithium at 475 K, have been successfully explained using the modified microscopic theory of the collective dynamics of a simple liquid, in a huge wave-vector, κ, range: 1.4 nm?1 ≤ κ ≤ 110.0 nm?1, ?κ is the linear momentum transfer. The role of single particle motion in the collective dynamics of the liquid changes from diffusive for smaller values of wave-vector, κ < 21 nm?1 to that of a free particle for higher κ-values, 21 nm?1 ≤ κ ≤ 110 nm?1. The quantum correction due to detailed balance condition in S(κ, ω) for liquid Li, whose dynamics, unlike that of quantum liquid 4He, is essentially classical, yields results in better agreement with the corresponding experimental S(κ, ω) and the quantum correction becomes significant for higher values of κ and ω. The wave-vector dependent variation of longitudinal viscosity, ηl, is in good agreement with the corresponding results obtained from memory function approach. The wave-vector dependent variation of single characteristic relaxation time lies in between the variation of two relaxation times of memory function approach. 相似文献
66.
Self-assembled nanocages for hydrophilic guest molecules 总被引:1,自引:0,他引:1
Jones MC Tewari P Blei C Hales K Pochan DJ Leroux JC 《Journal of the American Chemical Society》2006,128(45):14599-14605
Reverse polymeric micelles are obtained following the association of polymeric amphiphiles in apolar media. To this date, reports of pharmaceutical applications for such micelles have been scarce, mainly because these systems have been studied in solvents that are not suitable for medical use. Here, alkylated star-shaped poly(glycerol methacrylate) polymers have been proposed in the design of oil-soluble reverse polymeric micelles. Micellar behavior was studied in various apolar solvents, including ethyl oleate, a pharmaceutically acceptable vehicle. The polymers were shown to assemble into spherical nanostructures (<40 nm) as determined by cryogenic transmission electron microscopy and atomic force microscopy studies. Interestingly, the reverse micelles were able to encapsulate various peptides/proteins (vasopressin, myoglobin, and albumin) in substantial amounts and facilitate their solubilization in oil. The nature of both the polymer used in micelle formation and the guest molecules was found to influence the ability of the micelle to interact with hydrophilic compounds. 相似文献
67.
Vikas?D.?GhuleEmail author Dharavath?Srinivas S.?Radhakrishnan Pandurang?M.?Jadhav Surya?P.?Tewari 《Structural chemistry》2012,23(3):749-754
Density functional theory has been used to investigate geometries, heats of formation (HOFs), C-NO2 bond dissociation energies (BDEs), and relative energetic properties of nitro derivatives of azole substituted furan. HOFs for a series of molecules were calculated by using density functional theory (DFT) and Møller–Plesset (MP2) methods. The density is predicted using crystal packing calculations; all the designed compounds show density above 1.71 g/cm3. The calculated detonation velocities and detonation pressures indicate that the nitro group is very helpful for enhancing the detonation performance for the designed compounds. Thermal stabilities have been evaluated from the bond dissociation energies. Charge on the nitro group was used to assess the impact sensitivity in this study. According to the results of the calculations, tri- and tetra-nitro substituted derivatives reveal high performance with better thermal stability. 相似文献
68.
The cushioning material in a tractor seat plays a dominant role in supporting operator posture, isolating vibration and improving ride quality. Vibration attenuation in a tractor seat is achieved by selecting proper suspension and damping mechanism. This paper describes damping characterisation of tractor seat cushion materials to improve operator’s comfort. Nine commercially available seat cushion materials of different densities, thickness and compositions were selected for the study. A sinusoidal displacement exciter was designed to measure damping characteristics of the seat cushion materials in the frequency range of 1–8 Hz with displacement amplitudes of 10, 15 and 20 mm peak-to-peak. It was observed that the equivalent viscous damping coefficient (Ceq) of cushion materials decreased with the increase in frequency and peak-to-peak amplitude of vibration and decrease was very sharp in the lower frequency range up to 3 Hz. The average percentage reduction in Ceq increased with increase in peak-to-peak amplitude of vibration from 10 to 20 mm for the selected seat cushion materials. The average percentage reduction in Ceq was the highest for thinner high density polyurethane (PU) foam (thickness of 44 mm, density of 19.09 kg/m3) at different frequencies of vibration. It may be concluded that the high density PU based cushion material is good for dampening vibrations transmitted in tractor under dynamic condition. 相似文献
69.
A. P. Singh W. R. Kalsi A. K. Tewari S. K. Puri B. Basu A. S. Sarpal 《Chromatographia》2001,54(7-8):537-540
Summary A procedure has been standarized for the determination of p-dioxan (1,4-dioxan) in benzene feedstock in the range of 1 to
100 ppm by capillary GC. The GC conditions such as oven temperature, length of the column etc were optimized to achieve better
resolution of p-dioxan from hydrocarbons. The standard addition method of quantitation, was used to determine the amount of
p-dioxan and was found to give better results than those obtained by external standardization. Prior to analysis the identity
of the p-dioxan peak was established by GC-MS. The proposed method has been applied for the monitoring of p-dioxan in high
purity benzene feedstock produced by the Udex extraction process in the refinery. The data were used for optimization of plant
conditions for the production of high purity benzene feedstock. By using this method, the p-dioxan content down to 0.5 ppm
can be determined in the benzene feedstock. 相似文献
70.
ZnO thin films were prepared by spray pyrolytic decomposition of zinc acetate onto a glass substrate. These films were analyzed for the optical and electrical properties. Optical studies show that in these films the electronic transition is of the direct transition type. The optical energy gap for the films of different thicknesses is estimated to be in the range 2.98 – 3.09 eV. Electrical studies indicate that the films exhibit thermally activated electronic conduction and the activation energies are found to be dependent on the film thickness. The complex impedance measurements were carried out over a wide range of frequencies at room temperature (300 K). All the impedance spectra contain only a single arc, but the arc has a non‐zero intersection with the real axis in the high frequency region. Also, the arc has its centre lying below with the real axis which indicates the multirelaxation behavior of the films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献