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排序方式: 共有124条查询结果,搜索用时 218 毫秒
31.
Trávníček Zdeněk Maloň Michal Biler Martin Hajdúch Marián Brož Pavel Doležal Karel Holub Jan Kryštof Vladimír Strnad Miroslav 《Transition Metal Chemistry》2000,25(3):265-269
Compounds of composition [Ni(L)(H2O)2Cl] and [Ni(L)(H2O)(NO3)] · EtOH [HL = 6-(2-chlorobenzylamino)purine] have been synthesized and characterized by elemental analyses, i.r. and electronic spectra, magnetic measurements and mass spectroscopy as tetrahedral nickel(II) complexes. The geometry of both complexes has been optimized using molecular mechanics modelling. Although the monoanionic ligand L is potentially bidentate, we assume that the coordination to nickel is via the N9 atom only. Cytokinin and anti-cancer activities of the complexes were also tested in an Amaranthus cytokinin bioassay and in an in vitro MTT-based cytotoxicity assay, respectively. In human T-lymphoblastic leukemia cell line CCRF-CEM both complexes showed potent cytotoxic activity. 相似文献
32.
Direct and indirect potentiometric, bipotentiometric and biamperometric titrations with a standard iron(II) solution are described for some inorganic compounds in alkaline media containing hexitols (mannitol, dulcitol and sorbitol). The optimal conditions for titrations based on the Cr(VI) → Cr(III), Mn(IV) → Mn(III) → Mn(II), V(V) → V(IV), Co(III) → Co(II) and U(VI) → U(IV) systems are discussed. Of the hexitols studied, sorbitol has the greatest effect on the value of the redox potential of the Fe(III)/Fe(II) system; the Ef° value is about —1.10 V vs. SCE. 相似文献
33.
A method for the gravimetric determination of cerium as Ce3(PO4)4 is described. Cerium can be separated from many metals in this form, as well as from permanganate and dichromate; the cerium separated can then be titrated with iron(II) solution. The method was verified for the determination of cerium in a rare earth concentrate. 相似文献
34.
Optimal reaction conditions for the direct spectrophotometric determination of niobium in steels are described. Conditions for the formation of the niobium—sulphochlorophenol S complex are defined, and the effects of many alloying elements are discussed. Niobium can thus be determined in all types of steels in the range of 0.002–3%Nb. 相似文献
35.
Fouzia Jbilou Catherine Joly Sophie Galland Laurent Belard Valérie Desjardin Rémy Bayard Patrice Dole Pascal Degraeve 《Polymer Testing》2013,32(8):1565-1575
Plasticised corn flour/poly(butylene succinate-co-butylene adipate) (PBSA) materials were prepared by extrusion and injection in order to study the impact of PBSA ratio on their physicochemical properties and biodegradability. Scanning electron microscopy observations showed that corn flour and PBSA are incompatible. Three types of morphology have been observed: (i) starch dispersed in a PBSA matrix, (ii) a “co-continuous-like” morphology of starch and PBSA, and (iii) PBSA dispersed in a starch matrix. As expected, the extent of plasticised corn flour starch hydrolysis by amylolytic enzymes decreased when the amount of PBSA increased. Addition of a lipase to hydrolyse PBSA ester bonds enhanced enzymatic hydrolysis of starch by amylolytic enzymes in materials where PBSA formed a continuous phase. This suggests that PBSA formed a barrier restricting the access of amylolytic enzymes to starch. This was consistent with aerobic and anaerobic biodegradation assays, which also showed lower biodegradability of materials containing a majority of PBSA. 相似文献
36.
S. P. Gomes J. Doležalová A. N. Araújo C. M. C. M. Couto M. C. B. S. M. Montenegro 《Journal of Analytical Chemistry》2013,68(9):794-800
In this work the preparation and electrochemical characterisation of a new glutamate amperometric sol-gel biosensor is described. A carbon paste electrode was electrochemically modified with the phenothiazine dye methylene green (MG). The NADP+ and glutamate dehydrogenase were co-immobilised in a sol-gel matrix. When coupled to a flow injection system (FIA) the biosensor showed good electrocatalytic activity towards NADPH oxidation at the potential of + 0.3 V vs. Ag/AgCl; KCl sat., which represents a strong overpotential reduction. The biosensor yielded a linear response from 5.0 × 10?5 to 1.0 × 10?2 M glutamate concentration, with a detection limit of 5 × 10?6 M and reproducibility of results better than 2.3% (RSD). Moreover, the implemented biosensor showed to be still useful after 7 months, 500 determinations. 相似文献
37.
Won E Ko BR Adachi I Aihara H Arinstein K Asner DM Aushev T Bakich AM Barberio E Bay A Bhardwaj V Bhuyan B Bischofberger M Bondar A Bozek A Bračko M Brodzicka J Browder TE Chang P Chen A Chen P Cheon BG Chilikin K Cho IS Cho K Choi SK Choi Y Dalseno J Danilov M Doležal Z Drásal Z Drutskoy A Eidelman S Fast JE Gaur V Gabyshev N Garmash A Goh YM Golob B Haba J Hara T Hayasaka K Hayashii H Horii Y Hoshi Y Hou WS Hsiung YB Hyun HJ Iijima T Inami K Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T 《Physical review letters》2011,107(22):221801
We report the first observation of the doubly Cabibbo-suppressed decays D(+)→K(+)η((')) using a 791 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbo-suppressed D(+)→π(+)η((')) decays are B(D(+)→K(+)η)/B(D(+)→π(+)η)=(3.06±0.43±0.14)% and B(D(+)→K(+)η')/B(D(+)→π(+)η')=(3.77±0.39±0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D(+) decays, δ(TA), is (72±9)° or (288±9)°. We also report the most precise measurements of CP asymmetries to date: A(CP)(D(+)→π(+)η)=(+1.74±1.13±0.19)% and A(CP)(D(+)→π(+)η')=(-0.12±1.12±0.17)%. 相似文献
38.
Josef Jampílek Eliška Brojerová Martin Doležal Jiří Kuneš Daniel Jun 《Chemical Papers》2008,62(3):281-287
Arylalkanoic acid derivatives exhibit a variety of biological effects. In the current publication some of new glycidic acid
derivatives were prepared via the Darzens condensation. The synthetic approach, analytical and spectroscopic data of all newly
synthesized compounds are presented. The prepared compounds were evaluated as potential inhibitors of arachidonic acid-induced
platelet aggregation and their activity was compared with that of acetylsalicylic acid as the standard. (±)-Ethyl 3-{4-[(4-methoxyphenyl)sulfanyl]phenyl}-3-methyl-cis-oxirane-2-carboxylate (IC50 = 0.07 mmol L−1) and (±)-3-{4-[(4-methoxyphenyl)sulfanyl]phenyl}-3-methyl-cis-oxirane-2-carboxylic acid (IC50 = 0.06 mmol L−1) showed the highest antiplatelet activity against arachidonic acid-induced platelet aggregation comparable with the standard.
Structure-activity relationships between the chemical structure, lipophilicity, and the antiplatelet activity of the evaluated
compounds are discussed. 相似文献
39.
40.
Maša Islamčević Razboršek Darinka Brodnjak Vončina Valter Doleček Ernest Vončina 《Chromatographia》2008,67(5-6):433-440
Phytochemical investigations of different species of Lamiaceae family (rosemary-Rosmarinus officinalis L., sage-Salvia officinalis L., winter savory-Satureja montana L., clary sage-Salvia sclarea L. and sticky sage-Salvia glutinosa L.), using gas chromatography and mass spectrometry (GC-MS) were performed. The studies were focused on oleanolic, betulinic
and ursolic acid. Since oleanolic and ursolic acid are position isomers with very similar structures, the difficulties in
their separation and identification have been reported by several authors. However, both compounds can be well distinguished
by order of elution during gas chromatography and by intensities of the fragment ion signals in their mass spectra, where
the retro-Diels-Alder reaction was primarily observed. A combination of ultrasonic extraction, solid phase extraction, size
exclusion chromatography, trimethylsilylation, and GC-MS resulted in simultaneous separation, identification and quantification
of the mentioned compounds. The compounds have been identified by retention time and comparison of mass spectra with those
of pure standards. The mass spectral fragmentation behavior of all three derivatised acids was investigated. The obtained
characteristic fragment patterns are discussed in the presented work. Good linearity over the concentration range 1–50 mg
L−1 for all three compounds was confirmed. The correlation coefficients (r
2
) were in the range of 0.9980–0.9983. Quantitative analyses of different Lamiaceae extracts showed that the oleanolic acid content ranged from 0.09 to 0.9% dry weight, content of betulinic acid ranged from
traces to 0.6%, and that of ursolic acid varied from 0.09 to 1.6% dry weight. 相似文献