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排序方式: 共有210条查询结果,搜索用时 11 毫秒
71.
Kamlakar Avasthi Lakshmi Shukla Ruchir Kant Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(6):555-561
The butylidene‐linker models 1‐[2‐(2,6‐dimethylsulfanyl‐9H‐purin‐9‐yl)‐2‐methylidenepropyl]‐4,6‐bis(methylsulfanyl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C18H20N8S4, (XI), 7,7′‐(2‐methylidenepropane‐1,3‐diyl)bis[3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one], C20H22N6O2S2, (XIV), and 7‐[2‐(4,6‐dimethylsulfanyl‐1H‐pyrazolo[3,4‐d]pyrimidin‐1‐yl)‐2‐methylidenepropyl]‐3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one, C19H21N7OS3, (XV), show folded conformations in solution, as shown by 1H NMR analysis. This folding carries over to the crystalline state. Intramolecular π–π interactions are observed in all three compounds, but only (XIV) shows additional intramolecular C—H...π interactions in the solid state. As far as can be established, this is the first report incorporating the pyrrolo[2,3‐d]pyrimidine nucleus for such a study. In addition to the π–π interactions, the crystal structures are also stabilized by other weak intermolecular C—H...S/N/O and/or S...N/S interactions. 相似文献
72.
Russian Journal of Organic Chemistry - A simple, green, and efficient protocol has been developed for the synthesis of biologically active 1,4dihydropyrano[2,3c]pyrazole derivatives via one-pot... 相似文献
73.
A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured
alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors
like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the
efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with
the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature
dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08,
0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related
to the process of stress relaxation in crystals. 相似文献
74.
K.N. Shrivastava 《Solid State Communications》1984,50(7):615-617
We propose the existence of phonon-induced virtual states in amorphous systems and calculate their width. The resonance occurs when the phonon frequency is equal to the electronic band gap. We predict the phenomenon of valencostriction, namely, the change in volume upon change in valence which provides observational evidence for the new wave functions. 相似文献
75.
Mechanoluminescence activity and charge produced during fracture are measured in many organic crystals of monoclinic system. The crystals belonging to sphenoidal and domatic classes which are piezoelectric, exhibit mechanoluminescence; however, the crystals belonging to prismatic class which are non-piezoelectric, do not exhibit mechanoluminescence. This fact suggests the piezoelectric origin of mechanoluminescence and shows that mechanoluminescence is a structure sensitive property of the crystals. 相似文献
76.
Nirogi RV Kandikere V Shrivastava W Mudigonda K Maurya S Ajjala D 《Biomedical chromatography : BMC》2007,21(11):1151-1158
A high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the quantification of pramipexole in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 212/152 for pramipexole and m/z 409/228 for the IS. The method exhibited a linear dynamic range of 200-8000 pg/mL for pramipexole in human plasma. The lower limit of quantification was 200 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 3.5 min for each sample made it possible to analyze more than 200 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies. 相似文献
77.
A. Lemasson A. Navin M. Rejmund N. Keeley V. Zelevinsky S. Bhattacharyya A. Shrivastava D. Bazin D. Beaumel Y. Blumenfeld A. Chatterjee D. Gupta G. de France B. Jacquot M. Labiche R. Lemmon V. Nanal J. Nyberg R.G. Pillay R. Raabe K. Ramachandran J.A. Scarpaci C. Schmitt C. Simenel I. Stefan C.N. Timis 《Physics letters. [Part B]》2011
78.
Ahmad Nazrul Rosli Noriza Ahmad Zabidi Hasan A. Kassim Keshav N. Shrivastava 《Journal of Cluster Science》2011,22(3):491-499
We have performed the calculation of the vibrational frequencies, Fermi energy and binding energy for several clusters of
Ni and vanadium atoms by using the first principles. The calculations are performed by using the density-functional theory
in the local-density approximation with spin polarized orbitals. The calculation of vibrational frequencies shows that some
of the clusters have positive vibrational frequencies which describe the oscillations of the stable clusters. The negative
vibrational frequencies indicate that these clusters are instable with respect to these vibrations when no energy of this
frequency is supplied. We find that for vanadium concentration less than 11.1% the clusters of Ni and V atoms are not stable.
Hence ferromagnetism in Ni is predicted below 11.1% vanadium. We find the vibrational frequencies of several clusters for
which the vanadium concentration is more than 11.1%. We are able to find a phase transition by use of quantum mechanics alone
without the use of classical mechanical variables or thermodynamic variables such as temperature. 相似文献
79.
Atul Shrivastava Upma Chaturvedi Ravi Sonkar Ashok Kumar Khanna J. K. Saxena Gitika Bhatia 《Applied biochemistry and biotechnology》2012,167(2):229-236
Oxidative stress plays a major role in the pathogenesis of both types of diabetes mellitus. Excessively high levels of free radicals cause damage to cellular proteins, membrane lipids and nucleic acids, and eventually cell death. The present study was designed to investigate the possible effect of Azadirachta indica leaf extract in high fat diet induced diabetic Charles Foster rats. The increased level of lipidperoxidation and altered levels of enzymatic (superoxide dismutase, glutathione peroxidase and catalase) and non-enzymatic (glutathione) antioxidants were seen in high fructose fed animals. The treatment with A. indica leaf extract significantly normalized the altered levels of lipid peroxidation and antioxidant status at 400?mg/kg b.w. dose. The A. indica leaf extract was also tested for in vitro inhibition of generation of superoxide anion and hydroxyl free radical in both enzymatic and non-enzymatic systems. The A. indica leaf extract was found to inhibit generation of superoxide anion and hydroxyl free radical significantly at 200???g/ml concentration. Data of present study demonstrated that the A. indica leaf extract has both antidiabetic and antioxidant properties. 相似文献
80.
Ramanand Prajapati Amrendra Kumar Rajendar Kandhikonda Ruchir Kant Narender Tadigoppula 《Tetrahedron》2019,75(3):374-380
Benzoxazine derivatives are useful building blocks and display various biological activities. We serendipitously discovered and subsequently developed a new one pot method for the synthesis of 2-(dimethyl amino)/2-morpholino/2- (piperidin-1-yl)-4H-benzo[e][1,3]oxazin-4-ones from corresponding substituted 2,2-diazidobenzofuran 3(2H) - ones and N-formyl dimethyl amine (DMF)/N-formylmorpholine/N-formylpiperidine using m-CPBA at 100?°C in moderate to good yields. We also demonstrated the utility of 4H-benzoxazines for the synthesis of other medicinally important compounds such as 2-hydroxyphenyl substituted 1,2,4-triazoles, unsymmetrical 1,3,5-triazines, and 1,2,4-oxadiazoles. 相似文献