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51.
Summary First and second order resistance coefficients between membrane matrix and permeant for the permeation of methanol, acetone and methyl ethyl ketone through pyrex and quartz membranes have been evaluated from the experimental data on electroosmotic effects. Analysis of the data shows that-the following non-linear relationP =R
11
J
v
+R
12
I +R
122
I
2[1] exists between pressure difference,P, and the fluxes and a linear relation =R
21
J
v
+R
22
I [2] expresses the dependence of potential difference,, on the fluxes. The first order cross resistance coefficients have been found to obey theOnsager's reciprocity relation. An attempt has been made to explain the occurrence of higher order resistance coefficients in terms of electrokinetic character of the membrane, permeant interface.
With 2 figures and 2 tables 相似文献
Zusammenfassung Die Widerstandskoeffizienten 1. und 2. Ordnung zwischen einer Membranmatrix und dem permeierenden Stoff wurden für die Permeation von Methanol, Aceton und Methyläthylketon durch Pyrex- und Quarz-Membranen auf Grund elektroosmotischer Effekte bestimmt. Die Auswertung gibt die nichtlineare BeziehungP =R 11 J v +R 12 I +R 122 I 2 [1] zwischen der Druckdifferenz und dem Fließen; die lineare Beziehung =R 21 J v +R 22 I [2] beschreibt die Abhängigkeit der Potentialdifferenz vom Fließen. Die gekreuzten Widerstandskoeffizienten 1. Ordnung gehorchen dem ReziprozitätsgesetzOnsager. Das Vorkommen von Widerstandskoeffizienten höherer Ordnung wird versuchsweise auf den elektrokinetischen Charakter der Membran-Grenzfläche zurückgeführt.
With 2 figures and 2 tables 相似文献
52.
K. C. Srivastava 《中国化学会会志》1974,21(3):163-166
A new, sensitive spectrophotometric method for the determination of palladium(II) with methylthymol blue has been developed. The palladium methylthymol blue complex has an absorption maximum at 530 nm. The colour reaction has a sensitivity of 0.005 µg of palladium/cm2 and obeys Beer's Law over the range 0.4 to 3.24 ppm of palladium. The effects of concentration of perchloric acid, reagent, heating, stability of colour and diverse ions have been investigated. The ratio of metal: ligand in the complex is 1:1 and the formation constant was calculated to be 1.18×104. 相似文献
53.
54.
Summary The coagulation concentration for silver iodide sol, both in presence of pyridine and dioxane, increases for mono- and bivalent
coagulating electrolyte. In presence of a mixture of pyridine and dioxane in equal volume, the coagulation concentration assumes
an intermediate value, which is nearer to dioxane. However, in presence of dioxane more bivalent electrolyte is needed than
in presence of pyridine. If a bivalent coagulating electrolyte is added to a sol containing a mixture of pyridine and dioxane,
the amount of electrolyte required to coagulate is less than pyridine and greater than dioxane. Thus silver iodide sol is
more stable toward mono- and bivalent coagulating electrolytes. The degree of stabilization increases with the decrease of
the dielectric constant of the dispersing medium. The intermediate values for dioxane pyridine mixture is accountable by the
fact that dioxane acts as a solvent for pyridine. The PH value of the sol increases up to the coagulation point. Beyond this,
there is an abrupt decrease. When the particles settle down completely a rise in PH is again noted on the further addition
of electrolytes. The increase in the electrical conductance is more significant after coagulation. These changes have been
explained by adsorption of the ions and due to the release of ions from the electrical double layer.
Our thanks are due to Prof. R. C. Mehrotra for providing all the facilities for this work and to Prof. S. Ghosh of Allahabad University for helpful discussions. Thanks are also due to the University Grants Commission, Government of India, for the award of a research scholarship to one of us (V. K. S.). 相似文献
Zusammenfassung Die Koagulationskonzentration für Silberjodidsol in Gegenwart von Pyridin und Dioxan steigt für ein- und zweiwertige Elektrolyte an. In Gegenwart einer Mischung zu gleichen Volumen erh?lt man mittlere Werte, n?her denen zu Dioxan. Für Koagulation in Gegenwart von Dioxan ist jedoch mehr zweiwertiger Elektrolyt notwendig als in Gegenwart von Pyridin. Bei Koagulation mit zweiwertigem Elektrolyt verbraucht ein Sol mit der Mischung von Pyridin und Dioxan weniger als für Pyridin und mehr als für Dioxan. Daher ist das Silbersol gegenüber ein- und zweiwertigen Elektrolyten stabiler. Der Grad der Stabilisierung w?chst mit abnehmender Dielektrizit?tskonstante des Dispersionsmediums. Die Zwischenwerte der Dioxan-Pyridin-Mischungen lassen sich verstehen durch die Tatsache, da? Dioxan als L?sungsmittel für Pyridin wirkt. Der PH-Wert des Sols w?chst bis zum Koagulationspunkt, darüberhinaus erfolgt ein steiler Abfall. Wenn die Teilchen vollst?ndig absetzen, ist bei weiterer Zugabe von Elektrolyt ein erneuter Anstieg im PH feststellbar. Der Anstieg der elektrolytischen Leitf?higkeit wird nach der Koagulation ausgepr?gter. Diese ?nderungen lassen sich durch Ionenadsorption und Freiwerden von Ionen aus der elektrischen Doppelschicht erkl?ren.
Our thanks are due to Prof. R. C. Mehrotra for providing all the facilities for this work and to Prof. S. Ghosh of Allahabad University for helpful discussions. Thanks are also due to the University Grants Commission, Government of India, for the award of a research scholarship to one of us (V. K. S.). 相似文献
55.
Kundu B Rastogi SK Ahmad R Srivastava AK 《Combinatorial chemistry & high throughput screening》2002,5(7):545-550
A library of 72 compounds related to N- [4-(benzyloxy) benzoyl]alanine (I) was synthesized, prepared and screened for alpha-glucosidase inhibitory activity. Four compounds showed potent inhibition, six compounds moderate inhibition, and 16 were weak inhibitors. One compound, N- [4-(benzyloxy) benzoyl] serine, was found to be a potent inhibitor of alpha-glucosidase with 100% inhibition at 1 micro M. This inhibitor was at least five times more potent than the lead compound I. 相似文献
56.
Observations of the activity of two hydrolyzing enzymes—protease and α-amylase—entrapped inside the reversed micelles formed
by surfactants in hexane, benzene, and cyclohexane are reported. The surfactants chosen for this study are: Tween 80, a nonionic
surfactant, Cetyl pyridinium chloride, a cationic surfactant, and two anionic surfactants, sodium lauryl sulfate and Aerosol
OT.
Tween 80 enhances the activity of both protease and α-amylase. Sodium lauryl sulfate and Aerosol OT, which are ionic surfactants,
enhance the activity of protease, but inhibit the activity of α-amylase. Cetyl pyridinium chloride, however, enhances the
activity of α-amylase, but inhibits the activity of protease. Enhanced activity is generally severalfold greater in comparison
to the activity observed in the usual aqueous system in the absence of reversed micelles. It has also been observed that the
enhanced activity of the enzymes entrapped inside the reversed micelles remains preserved for a much longer period of time
in comparison to the activity in the usual aqueous systems. These observations, which support the view that with proper choice
of surfactant and the organic solvent, reversed micelles act like a microreactor that provides a favorable aqueous microenvironment
for enzyme activity, have biotechnological overtones. 相似文献
57.
58.
59.
Summary Triisopropoxy bis(O,O-dialkyl dithiophosphates), (i-PrO)3M[S2P(OR)2]2 (M = Nbv, Tav; R = n-Pr, i-Pr, i-Bu and Ph) have been prepared by reacting the appropriate triisopropoxymetal(V)dichloride, (i-PrO)3MCl2 (1 mol) with sodium/ammonium dialkyl dithiophosphates (2 mols)in THF. The monomeric products which are viscous liquids, soluble in common organic solvents and highly susceptible to hydrolysis, were characterized by i.r. and n.m.r. spectra which indicate a bidentate mode of attachment of dithiophosphato groups to the metal. 相似文献
60.
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