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941.
Muhammad Saeed 《Tetrahedron letters》2005,46(26):4449-4451
The human carcinogen diethylstilbestrol (DES) is metabolized into 3′-hydroxydiethylstilbestrol (3′-OH-DES) (1). Chemical oxidation of the catechol metabolites with silver oxide in CH2Cl2 affords a novel spiro-quinone (3) in quantitative yield. Protection of the phenolic OH group followed by oxidation gives 4″-OCH3-DES-3′,4′-Q (5) in excellent yield. 相似文献
942.
On finite conductor domains 总被引:2,自引:0,他引:2
Muhammad Zafrullah 《manuscripta mathematica》1978,24(2):191-204
An integral domain D is a FC domain if for all a, b in D, aDbD is finitely generated. Using a set of very general and useful lemmas, we show that an integrally closed FC domain is a Prüfer v-multiplication domain (PVMD). We use this result to improve some results which were originally proved for integrally closed FC domains (or for coherent domains) to results on PVMD's. Finally we provide examples of integrally closed integral domains which are not FC domains. 相似文献
943.
Shazia Anjum Muhammad Asif Kashaf Zia Bakhat Jahan Muhammad Ashraf Shafqat Hussain 《Natural product research》2020,34(16):2315-2318
Abstract The present work deals with the biological and phytochemical studies on Capparis decidua (Forssk) Edgew from Cholistan desert of Pakistan. Aerial and floral parts of C. decidua were collected and dried under shade. Powdered materials of each part of C. decidua were extracted with methanol separately, followed by phytochemical studies. Hexane fraction of aerial parts of the C. decidua obtained after solvent-solvent extraction was purified through repeated column chromatography by increasing order of polarity. Four compounds were purified and identified as simiarenol (1), lupeol (2), taraxerol (3) and β-sitosterol (4). Simiarenol and lupeol were isolated for the first time from genus Capparis. The structures of these compounds were established by comparing the spectroscopic data (1H NMR, 13C NMR, IR, UV & Mass spectrometry) reported in literature. The structure of 1 was further confirmed by XRD analysis. Anti-bacterial activities of crude methanolic extracts were determined against 13 bacterial strains (MIC 250-1000?μg/mL). α-Glucosidase and urease inhibitory activities of pure compounds were also determined. Compounds 1, 2 and 4 showed α-glucosidase inhibition with IC50 at 96.12?±?0.12, 65.28?±?0.13 and 128.14?±?0.17?μM, respectively. 相似文献
944.
Jinhui Zhang Yang Yang Muhammad Ashraf Celia N. Cruz Sau Lee Patrick J. Faustino 《Rapid communications in mass spectrometry : RCM》2022,36(11):e9273
Rationale
Systemic absorption of UV-filtering chemicals following topical application of sunscreens may present a safety concern. The Food and Drug Administration (FDA) had recommended an in vitro skin permeation test (IVPT) to evaluate the potential of this safety risk for the evaluation of sunscreens prior to clinical studies. Therefore, a sensitive and robust bioanalytical method(s) were required for IVPT studies of different topical sunscreen products.Methods
An analytical procedure to quantitate sunscreen UV-filtering components and excipients in IVPT samples including avobenzone, octocrylene, oxybenzone, ecamsule, methylparaben and propylparaben was developed employing a RapidFire 360 robotic sample delivery system coupled with a triple quadrupole mass spectrometer. The analytical procedure was developed and validated according to the requirements of the FDA Bioanalytical Method Validation Guidance for Industry (2018).Results
The analytical method provided a turnaround time of 12 seconds per sample and was determined to be accurate, precise, specific, and linear over the corresponding analytical ranges. The validated method was successfully applied for two IVPT studies for evaluating the skin permeation potential of UV-filtering chemicals and assisting with the selection of the sunscreen products for the clinical study conducted by the FDA.Conclusions
This work highlights the first analytical procedure that has applied a non-chromatographic-MS/MS automation platform to an in vitro biopharmaceutics study. The analytical platform simultaneously quantitated four UV filters and two excipients in complex media to evaluate their permeation in IVPT studies. The sample throughput and analytical performance of advanced automation platforms indicate their analytical procedure has the potential to significantly advance the efficiency of IVPT studies to evaluate permeation of a wide variety of UV chemical filters and excipients for topical OTC sunscreen products.945.
Muhammad Abdul Hamid Ejaz Ur Rehman Muhammad Fuzail Riffat Naheed Amin-Uddin Ahmed 《Journal of Radioanalytical and Nuclear Chemistry》1995,190(1):37-50
The oxidation-reduction reaction between U(VI) and Ti(III) in HCl solution was studied spectrophotometrically. The reaction is second-order at all concentrations of reactants, HCl, ferrous chloride and mannitol used in this work. In 5M HCl the rate constantk increases with increasing Ti(III) concentration, whereas it decreases with increasing U(VI) concentration, with increasing HCl concentration from 1.00M to 7.17M and increases thereafter from 7.17M to 11.79M. The addition of mannitol causes a consistent decrease in the rate of reaction, whereas ferrous chloride has no effect. The activation energy for this oxidation-reduction reaction was 47.90±0.11 kJ·mol–1. The values of H
, G
and S
were 45.40±0.11 kJ·mol–1, 72.50±0.17 kJ·mol–1 and –91.10±0.22J·k–1·mol–1, respectively. The mode of reaction is discussed in the light of kinetic results. 相似文献
946.
Anthony Linden A. S. Muhammad Sofian C. Kuan Lee 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o711-o714
At 160 K, the glucopyranosyl ring in 1,6‐dichloro‐1,6‐dideoxy‐β‐d ‐fructofuranosyl 4‐chloro‐4‐deoxy‐α‐d ‐glucopyranoside monohydrate, C12H19Cl3O8·H2O, has a near ideal 4C1 chair conformation, while the fructofuranosyl ring has a 4T3 conformation. The conformation of the sugar molecule is quite different to that of sucralose, particularly in the conformation about the glycosidic linkage, which affects the observed pattern of intramolecular hydrogen bonds. A complex series of intermolecular hydrogen bonds links the sugar and water molecules into an infinite three‐dimensional framework. 相似文献
947.
New steroidal alkaloids from Fritillaria imperialis and their cholinesterase inhibiting activities 总被引:3,自引:0,他引:3
Atta-Ur-Rahman Akhtar MN Choudhary MI Tsuda Y Sener B Khalid A Parvez M 《Chemical & pharmaceutical bulletin》2002,50(8):1013-1016
Two new cevanine steroidal alkaloids, impericine (1) and forticine (2) along with known bases delavine (3), persicanidine A (4), and imperialine (5) were isolated from the bulbs of Fritillaria imperialis. The structures of impericine (1) [(20R,22S,25S)-5alpha-cevanin-23-ene-3beta,6beta,16beta-triol] and forticine (2) [(20S,22S,25S)-5alpha-cevanine-3beta,6beta-diol] were determined with the help of spectroscopic studies. These steroidal bases showed anti-acetylcholinesterase and anti-butyrylcholinesterase inhibitory activity. 相似文献
948.
W. David Cotterill Muhammad Iqbal Robert Livingstone Maurice V. Walshaw 《Journal of heterocyclic chemistry》1974,11(3):283-286
The reaction between 3,3-bis(methoxyphenyl)-3H-naphtho[2,1-b]pyran and 1,3-bis(methoxyphenyl)-1H-naphtho[2,1-b]pyran under acid conditions gives a 7a,15a-dihydro-7a,15-bis(methoxyphenyl)-16-[2,2-bis(methoxyphenyl)-l-vinyl]dinaphtho-[2,1-b:2,1-g]-4H,5H-pyrano[2,3-b]-pyran. 相似文献
949.
Evaporation from water-ethylene glycol liquid mixture 总被引:1,自引:0,他引:1
Rusdi M Moroi Y Nakahara H Shibata O 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7308-7310
Evaporation rates were determined for water-ethylene glycol liquid mixtures with different mole fractions, where the evaporation rate expressed as mg min(-1)/area was used because of the presence of two kinds of molecular species. The rate increased with increasing temperature and decreased with increasing mole fraction of ethylene glycol, almost obeying ideal mixing of the two components, although a small positive deviation was observed over the mole fraction from 0 to 0.5 of ethylene glycol at higher temperatures. The activation energy of evaporation was determined from the temperature dependence of the evaporation rate, where the energy was an apparent one because the composition of evaporated species was not determined. The activation energy increased with decreasing temperature and with increasing mole fraction of ethylene glycol, where the energy obeyed the ideal mixing at lower temperatures while it positively deviated at higher temperatures. The evaporation rates were examined by surface tension of the liquid mixture, but any definite relation between them was not found. Both the evaporation rate and the activation energy were found to be determined mainly by the mole fraction in the surface layer from which the evaporation takes place. Finally, the new concept of surface excess was presented, where the surfactant molecules were concentrated and formed a bimolecular layer at a certain distance beneath the air/solution interface. 相似文献
950.
Noor Shahina Begum D. E. Vasundhara C. R. Girija G. D. Kolavi V. S. Hegde I. M. Khazi 《Journal of chemical crystallography》2007,37(3):193-198
Imidazo[2,1-b][1,3,4] thiadiazole derivatives are significant for their various pharmacological properties. This paper reports
the synthesis and structure of one of them, 2-cyclohexyl-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde.
The compound crystallizes in the monoclinic space group P21/c with a=17.316(3)?, b=6.5420(9)?, c =17.056(3)?, β=112.909(2)°, V=1779.7(4)?3, z=4. The, Imidazo[2,1-b][1,3,4] thiadiazole and the coumarin ring systems are each planar but inclined at an angle of 48.14(2)°
towards each other. The crystal structure is stabilized by C–H … O interactions. 相似文献