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21.
Vaishali Tiwari 《Thermochimica Acta》2006,443(2):206-211
Densities ρ and viscosities η of two hydroxamic acids, N-phenyl-2-chlorobenzo- and N-o-tolyl-4-chlorobenzo-, have been determined as a function of their concentration in aqueous acetone solution at temperatures 303.15 and 313.15 K. Apparent molar volumes, standard-state partial molar volumes and relative viscosities have been calculated. The viscosity data have been analyzed using Jones-Dole equation. The activation thermodynamic parameters of viscous flow have been evaluated using Feakins equation. These were obtained to throw light on the mechanism of viscous flow. Thermodynamic interactions in solutions have been studied in terms of a number of excess functions calculated from the experimental data. The effect of hydroxamic acid concentration and temperature on these parameters has been discussed. The results were interpreted in the light of solute-solvent interactions in aquo-organic media. 相似文献
22.
Summary 3,4-Dicyano-5-aminopyrazole, H3,4(CN)25NH2pz (L) reacts either with anhydrous MCl2 or with [M(PPh3)2Cl2] to yield ML4Cl2 complexes (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd or Hg), whose monomeric and covalent natures have been confirmed by their solubility in most non-polar solvents and their low electrical conductivities. The bonding mode of substituted pyrazole is inferred from the position of the (C-N) band in the i.r. spectra. The electronic spectra and the magnetic moments of these compounds were recorded. 相似文献
23.
S. P. Mushran A. K. Bose J. N. Tiwari 《Monatshefte für Chemie / Chemical Monthly》1976,107(4):1021-1027
N-bromosuccinimide oxidation of cyclopentanone in acidic media in presence of mercuric acetate has been made. A zero order dependance to N-bromosuccinimide and a first order dependence to cyclopentanone and hydrogen ion concentration has been observed. Ionic strength, mercuric acetate and succinimide has negligible effect while methanol addition has a positive effect. Various rate parameters have been computed and 1,2-cyclopentanedione identified as the end product. A suitable mechanism in confirmity with the above observations has been proposed.With 2 Figures 相似文献
24.
Devendra K. Rastogi Suresh K. Sahni Vidya B. Rana Satendra K. Dua 《Transition Metal Chemistry》1978,3(1):56-60
Summary Dimeric manganese(II)and iron(II)complexes, (ML)2, derived from benzoyl hydrazones ofo-hydroxyaryl aldehydes and ketones arc described and characterised by elemental analyses and by conductance, molecular weight, magnetic, electronic and i.r. spectral measurements. The dimeric nature of the complexes is revealed by i.r. spectra which show bands atca. 885 Mn2+ and 820 cm–1 Fe2+, characteristic of ring vibrations. The i.r. spectra reveal the terdentate nature of the ligands. The electronic spectra in dimethylformamide are consistent with the tetrahedral nature of the complexes. The appreciable lowering in
eff is attributed to the presence of exchange interactions between two paramagnetic atomsvia oxygen bridges.Reprints of this article are not available. 相似文献
25.
Summary The halogen oxidation and nitrosylation of cis-[(SB)M-(CO)4] [M = Cr or Mo, SB = N,N-ethylenebis(p-tolualideneimine), N,N-ethylenebis(p-N,N-dimethylaminobenzalideneimine) or N,N-ethylenebis(methyl-p-methoxyphenylketimine); M = Mo, SB = N,N-ethylenebis-(cinnamylideneimine) or N,N-ethylenebis(methyl-p-methylphenylketimine)] have been studied. Halogenation of [(SB)Cr(CO)4] yielded [(SB)CrX2] (X = Cl, Br or I) where-as [(SB)Mo(CO)4] gave [(SB)Mo(CO)3X2] (X = Br or I) and [(SB)MoX
x
] (X = I, n = 2; X = Cl or Br, n = 4). NOCl produced [(SB)Cr(NO)2Cl2] and [(SB)Mo(CO)2(NO)Cl] when reacted with the corresponding [(SB)M(CO)4]. The complexes were characterized by physico-chemical and spectroscopic measurements. 相似文献
26.
Devendra Kumar 《Journal of polymer science. Part A, Polymer chemistry》1980,18(4):1375-1385
With a view to understanding the structure of aromatic polyimide backbone, model compound N,N-bis(4-phenoxyphenyl)-1,2:4,5-benzenetetracarboxdiimide was synthesized by the condensation of pyromellitic dianhydride and 4-aminodiphenyl ether in solvent N,N-dimethylacetamide or N,N-dimethylformamide. Various side products formed during the reaction were isolated and identified by spectroscopical methods. This study reveals that the polymer backbone contains nearly 85% imide rings. The uncyclizable residues in the backbone are those derived by the chemical interaction of polymerization solvent or by the modification of intermediate orthoamido acid. The uncyclizable nature of the latter was explained in mass and infrared (IR) spectral studies. The role of the dipolar solvent appears to be vital to imidization. 相似文献
27.
4,4-bismaleimidophenyl methane (BM) and 3,3-bismaleimidophenyl sulfone (BS) were blended in solution using weight ratios 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) and 13 (MS13). Chain extended bismaleimide resins were also prepared by treating BS/BM with 4,4-diaminodiphenyl ether in molar ratios of 10.3 (BM-E and BS-E resins). These resins were also blended with bismaleimides and the curing characteristics were evaluated by differential scanning calorimetry. Increase in BM content in BMBS blends or increase in chain extended bismaleimide content in BM-EBS or BS-E BM blends resulted in a reduction of melting and curing temperatures. Indication about the extent of cross-linking was obtained from solubility measurements (in DMF) of isothermally cured resins (180 °C, lh and 220 °C, lh in an air oven). Thermogravimetric analysis of samples isothermally cured at 180 °C and 220 °C (lh each) was carried out in nitrogen atmosphere. Improvement in thermal stability of chain extended bismaleimides was observed on blending.
The financial assistance provided by Department of Science and Technology is gratefully acknowledged. 相似文献
Zusammenfassung 4,4-Bismalimidophenyl-methan (BM) und 3,3-Bismalimidophenyl-sulfon (BS) wurden in Lösung in den Gewichtsverhältnissen 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) und 13 (MS13) gemischt. Auch kettenpolymerisierten Bismalimid-Harze wurden durch Behandlung von BS/BM mit Diaminodiphenylether im Molverhältnis 10,3 dargestellt (BM-E- und BS-E-Harze). Die Kennwerte der Aushärtung von Mischungen dieser Harze mit den Bismalimiden wurden mittels DSC ermittelt. Eine Erhöhung des BM-Gehaltes in den BM BS-Mischungen oder des Gehaltes der BM-E BS oder BS-E-Mischungen an kettenpolymerisierten Bismalimiden führt zu einer Erniedrigung der Schmelz- und Aushärtetemperaturen. Hinweise über den Vernetzungsgrad wurden aus Löslichkeitsmessungen (in DMF) von Isotherm (je 1 Stunde bei 180 und 220 °C in Luft) gehärteten Harzen erhalten. Die thermogravimetrische Analyse der Isotherm bei 180 bzw. 220 °C 1 Stunde ausgehärteten Proben wurde in Stickstoffatmosphäre ausgeführt. Die thermische Stabilität der Bismalimide wird durch Verschneiden verbessert.
4,4-- () 3,3-- () 31 (MC 31), 21 (MC 21), 11 (MC 11), 12 (MC 12) 13 (MC13). - / 4,4- 10,3 ( - C-). - . - - - - , . ( 1 180 220°) . . - .
The financial assistance provided by Department of Science and Technology is gratefully acknowledged. 相似文献
28.
Summary Alkaline sodium borohydride has been employed as a reducing reagent for the titrimetric determination of compounds containing the carbonyl function. The sample is dissolved in methanol and is then reduced with alkaline sodium borohydride. After completion of the reaction, the excess sodium borohydride is back titrated against standardized hydrochloric acid solution using methyl red as indicator. The stoichiometry between the carbonyl function and sodium borohydride is 41.
Zusammenfassung Natriumborhydrid dient als Reduktionsmittel zur Titration von Carbonylverbindungen. Die Probe wird in Methanol gelöst und dann mit alkalischem Natriumborhydrid reduziert. Nach Ablauf der Reaktion wird der Überschuß mit Salzsäure gegen Methylrot zurücktitriert. Carbonylverbindung und Natriumborhydrid reagieren im Verhältnis 41.相似文献
29.
V.K. Chandra B.P. Chandra M. Tiwari R.N. Baghel M. Ramrakhiani 《Journal of luminescence》2012,132(6):1532-1539
When a voltage pulse is applied under forward biased condition to a spin-coated bilayer organic light-emitting diode (OLED), then initially the electroluminescence (EL) intensity appearing after a delay time, increases with time and later on it attains a saturation value. At the end of the voltage pulse, the EL intensity decreases with time, attains a minimum intensity and then it again increases with time, attains a peak value and later on it decreases with time. For the OLEDs, in which the lifetime of trapped carriers is less than the decay time of the EL occurring prior to the onset of overshoot, the EL overshoot begins just after the end of voltage pulse. The overshoot in spin-coated bilayer OLEDs is caused by the presence of an interfacial layer of finite thickness between hole and electron transporting layers in which both transport molecules coexist, whereby the interfacial energy barrier impedes both hole and electron passage. When a voltage pulse is applied to a bilayer OLED, positive and negative space charges are established at the opposite faces of the interfacial layer. Subsequently, the charge recombination occurs with the incoming flux of injected carriers of opposite polarity. When the voltage is turned off, the interfacial charges recombine under the action of their mutual electric field. Thus, after switching off the external voltage the electrons stored in the interface next to the anode cell compartment experience an electric field directed from cathode to anode, and therefore, the electrons move towards the cathode, that is, towards the positive space charge, whereby electron–hole recombination gives rise to luminescence. The EL prior to onset of overshoot is caused by the movement of electrons in the electron transporting states, however, the EL in the overshoot region is caused by the movement of detrapped electrons. On the basis of the rate equations for the detrapping and recombination of charge carriers accumulated at the interface expressions are derived for the transient EL intensity I, time tm and intensity Im corresponding to the peak of EL overshoot, total EL intensity It and decay of the intensity of EL overshoot. In fact, the decay prior to the onset of EL overshoot is the decay of number of electrons moving in the electron transporting states. The ratio Im/Is decreases with increasing value of the applied pulse voltage because Im increases linearly with the amplitude of applied voltage pulse and Is increases nonlinearly and rapidly with the increasing amplitude of applied voltage pulse. The lifetime τt of electrons at the interface decreases with increasing temperature whereby the dependence of τt on temperature follows Arrhenius plot. This fact indicates that the detrapping involves thermally-assisted tunneling of electrons. Using the EL overshoot in bilayer OLEDs, the lifetime of the charge carriers at the interface, recombination time of charge carriers, decay time of the EL prior to onset of overshoot, and the time delay between the voltage pulse and onset time of the EL overshoot can be determined. The intense EL overshoot of nanosecond or shorter time duration may be useful in digital communication, and moreover, the EL overshoot gives important information about the processes involving injection, transport and recombination of charge carriers. The criteria for appearance of EL overshoot in bilayer OLEDs are explored. A good agreement is found between the theoretical and experimental results. 相似文献
30.
Komuraiah Buduma Niranjana Kumar A Satya Srinivas KVN Kotesh Kumar J Srinivas Chinde Anand Kumar Domatti Yogesh Kumar Paramjit Grover Ashok Tiwari Feroz Khan 《Journal of heterocyclic chemistry》2021,58(11):2078-2089
Design, synthesis, and bioactivity evaluation of novel mannich bases ( 2a-2j ) and triazole-chalcone derivatives ( 7a-7k ) of Eugenol 1 were reported. Among all the derivatives tested for antiproliferative activity, di-amine manich derivative 2b (32.92 μM), and 4-methoxy chalcone triazole derivative 7d (33.05 μM) significantly inhibited HepG2 cell lines when compared to the standard doxorubicin (37.29 μM). Whereas most of the compounds such as diethylamine 2a (17.75 μM), (aminomethyl) methane diamine 2b (17.02 μM), and bis (chloromethyl) amine 2c (20.12 μM) showed moderate to better inhibition towards MCF-7 cell lines. The synthesized analogues were also tested for antidiabetic and antiobesity potentials. Compounds 2f (55.50%), 2c (54.34%), 7g (55.5%), and 2a (55.5%) have shown moderate inhibitory potentials toward intestinal α-glucosidase enzyme when compared to the standard Acarbose (72.86%). Likewise, compounds 7d (82.95%), 7f (76.19%), 7g (74.81%), 7e (74.81%), and 2g (72.50%) have shown significant to moderate inhibitory potentials toward Pancreatic lipase enzyme when compared to the standard orlistat (91.10%). ROS induces life-threatening diseases like diabetes, cancer, etc., and antioxidants play a major role in controlling their production. Compounds 2c (99.81%), 2i (99.80%), 2d (99.26%), 2g (98.79%), and 2f (98.42%) have shown significant antioxidant profiles in ABTS assay when compared to the standard Trolox (99.07%). Further, In silico Molecular docking and pharmacokinetic screening of the eugenol derivatives complemented the in vitro results indicating the drug likeness of the obtained active compounds. 相似文献