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451.
452.
A. M. El Atrash E. A. Saad M. S. A. Hamza 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(2):345-349
The extraction of radioactive152–154Eu by ethyl hydrogen benzyl phosphonate (HEBP) and ethyl hydrogen benzoyl phosphonate (HEBOP) in n-hexane from an aqueous solution of ionic strength 0.1M (Na+, HClO4) has been investigated at different temperatures and the thermodynamic functions evaluated. HEBOP was found to be more efficient than HEBP as extractant. In addition, the stability constant of the extracted complexes were determined. 相似文献
453.
Hamza A. S. Abujabal 《Results in Mathematics》1990,18(3-4):189-196
In the present paper we extend some commutativity theorems for rings as follows: Let m > 1, n and k be fixed non- negative integers, and let R be a left or right s- unital ring satisfying the polynomial identity [xn]y ? ymxk,x] = 0. Then R is commutative. Under appropriate conditions the commutativity of R has also been proved for the case m = 1. 相似文献
454.
Chemiluminescent evaluation of peroxide value in olive oil 总被引:1,自引:0,他引:1
A method is described for the evaluation of the peroxide value (PV, meq. O2 kg−1) in olive oil. The method is based on the chemiluminogenic energy-transfer reaction of bis(2,4,6-(trichlorophenyl)oxalate (TCPO) with hydrogen peroxide or total peroxides in the presence of Mn(II) as catalyst and 9,10-dimethylanthracene as fluorophore. The procedure developed allows the evaluation of PV within the range of 0.6-100 meq. O2 kg−1 (CL intensity = 1.76 × PV (meq. O2 kg−1) + 23.2, r2 = 0.994, n = 9) and relative standard deviation within the range 1-5% by using a simple manual measurement. 相似文献
455.
Shoukry MM Shehata MR Hamza MS van Eldik R 《Dalton transactions (Cambridge, England : 2003)》2005,(24):3921-3926
The interaction of [Ru(III)(edta)(H(2)O)](-) with a series of selected thiols having extra functional groups was investigated potentiometrically and kinetically. The pK(a) values of the uncoordinated carboxylic acid group and coordinated water molecule are 3.12 and 7.41, respectively, in aqueous solution at 25 degrees C and 0.1 M ionic strength. The formation constants of the complexes were determined in the pH range 3-9, and the concentration distribution of the various complex species was evaluated as a function of pH. The effect of dioxane on the pK(a) values of [Ru(III)(Hedta)(H(2)O)] and the formation constants of the corresponding thiol complexes is presented. The study also provides mechanistic information on the reaction of [Ru(III)(edta)(H(2)O)](-) with the thiols. The low values of DeltaH(not equal) and negative values of DeltaS(not equal) and DeltaV(not equal) for the substitution reactions of [Ru(III)(edta)(H(2)O)](-) clearly support the associative character of the substitution process. 相似文献
456.
Soad Abdel Meguid Osman Galal Eldin Hamza Elgemeie Galal Abdel Moein Nawar Mohamed Hilmy Elnagdi 《Monatshefte für Chemie / Chemical Monthly》1986,117(1):105-110
A variety of new 6-thiophen-2-yl and 6-furan-2-ylthiazolo[2,3—a]pyridine derivatives could be prepared via the reaction of 2-functionally substituted methyl-2-thiazolin-4-one with cyanomethylenethiophen-2-yl and cyanomethylenefuran-2-yl derivatives. The structure of the reaction products was established based on spectral data.
Aktivierte Nitrile in der Heterocyclen-Synthese: Die Synthese von 6-Thiophen-2-yl-und 6-Furan-2-yl-thiazolo[2,3—a]pyridin-Derivaten
Zusammenfassung Es konnte eine Reihe neuer 6-Thiophen-2-yl- und 6-Furan-2-yl-thiazolo-[2,3—a]pyridine über die Reaktion von 2-funktionell-substituierten Methyl-2-thiazolin-4-onen mit Cyanomethylenthiphen-2-yl bzw. Cyanomethylenfuran-2-yl-Derivaten hergestellt werden. Die Struktur der Reaktionsprodukte wurde mit spektroskopischen Methoden ermittelt.相似文献
457.
Molecular dynamics simulation of cocaine binding with human butyrylcholinesterase and its mutants 总被引:1,自引:0,他引:1
Molecular dynamics (MD) simulations were carried out to study cocaine binding with wild-type human butyrylcholinesterase (BChE) and its mutants based on a recently reported X-ray crystal structure of human BChE. For each BChE-cocaine system, we simulated both the nonprereactive and prereactive complexes in water. Despite the significant difference found at the acyl binding pocket, the simulated structures confirm the fundamental structural and mechanistic insights obtained from earlier computational studies of wild-type BChE with cocaine based on a homology model, e.g. the rate-determining step for BChE-catalyzed hydrolysis of biologically active (-)-cocaine is the (-)-cocaine rotation in the active site from the nonprereactive BChE-(-)-cocaine complex to the prereactive complex. It has been demonstrated that the MD simulations on both the nonprereactive and prereactive BChE-cocaine complexes can clearly reveal whether specific mutations produce the desired BChE-(-)-cocaine binding structures in which the (-)-cocaine rotation is less hindered while the required prereactive BChE-(-)-cocaine binding is maintained. Based on the MD simulations, both A328W/Y332A and A328W/Y332G BChE's are expected to have catalytic activity for (-)-cocaine hydrolysis higher than that of wild-type BChE and the activity of A328W/Y332G BChE should be slightly higher than that of A328W/Y332A BChE due to the less-hindered (-)-cocaine rotation in the mutant BChE's. However, the less-hindered (-)-cocaine rotation is only a necessary condition for a higher activity mutant BChE. The (-)-cocaine rotation is also less hindered in A328W/Y332A/Y419S BChE, but (-)-cocaine binds with A328W/Y332A/Y419S BChE in a way that is not suitable for the catalysis. Thus, A328W/Y332A/Y419S BChE is expected to lose the catalytic activity. The computational predictions were confirmed by our experimental kinetic data, demonstrating that the MD simulation-based computational protocol used in this study is reliable in prediction of the catalytic activity of BChE mutants for (-)-cocaine hydrolysis. 相似文献
458.
S. M. Hamza M. M. M. Ramiz I. M. Aly 《Journal of Thermal Analysis and Calorimetry》1994,42(6):1231-1239
The solid-state thermal reactions of 2,6-diamino-4-chloropyrimidine, 3,3-dimethoxybenzidine and of thiosemicarbazide with each of 2-hydroxy-1-naphthaldehyde and 2,4-dihydroxybenzaldehyde in a mole ratio of 1∶1 produced (1+1) condensation products (‘half units’). These solid state reactions have been studied by means of differential thermal analysis (DTA). The products of the reactions were identified using elemental analysis and IR spectroscopy. Some kinetic parameters such as orders and activation energies of the reactions were evaluated form the DTA curves. 相似文献
459.
Yusuf
zcan Semra de Mehmet Karakus Hamza Ylmaz 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):m388-m389
In the the title compound, [Ni(C21H28O2PS2)2], the Ni atom resides on an inversion centre and is coordinated in a square‐planar array by four S atoms, with Ni—S and P—S bond lengths of 2.2336 (12)/2.2351 (13) and 1.9910 (16)/2.0010 (17) Å, respectively. The two O‐2,4‐di‐tert‐butylphenyl and two 4‐methoxyphenyl moieties adopt trans configurations about the central Ni atom. 相似文献
460.
Jahan N Malik A Mustafa G Ahmad Z Ahmad S Anis E Malik S Shujaat S Afza N Atta-Ur-Rahman 《Natural product letters》2001,15(3):177-185
Pentacyclic triterpenes (1) and (2) have been isolated from Mimusops elengi and assigned structures 3beta,6beta,19alpha,23-tetrahydroxy-urs-12-ene and 1beta-hydroxy-3beta-hexanoyllup-20 (29)-ene-23, 28-dioic acid, respectively, on the basis of spectroscopic studies including 2D-NMR. The compound 1 showed moderate inhibiting activity against beta-glucuronidase enzyme 相似文献