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461.
Double Deposition and Stripping Steps for Trace Determination of Au(III) Using Anodic Stripping Voltammetry 下载免费PDF全文
A new way of decreasing the detection limit ‐ double deposition and stripping steps was proposed to determine trace amounts of gold(III) by anodic stripping voltammetry. Two carbon composite electrodes that differed drastically in their surface areas were used for the measurements. The calibration graph was linear from 1×10?9 to 1×10?8 mol L?1 following deposition time of 300 s at the first and the second electrode. The detection limit was found to be 2.3×10?10 and 1.4×10?11 mol L?1 for deposition time 600 and 2400 s, respectively. It is the lowest detection limit obtained so far for gold(III) determination in stripping voltammetry. 相似文献
462.
Richard S. Herrick Christopher J. Ziegler Tang Ding Janet Shaw Iwona Wrona Matthew Beaver 《Journal of Coordination Chemistry》2017,70(20):3488-3500
Eight new compounds, M(pyca(CH2)xCOOR)Cl2, M = Pd, Pt; R = Me, Et; x = 2, 3, 5, 11, were prepared. The resulting new complexes were characterized by 1H and 13C NMR spectroscopy and each was also structurally elucidated by X-ray crystallography. The compounds share general structural features, but there are differences in the alignment of the alkyl chain; as the chain lengthens, the chain straightens relative to the plane of the metal complex. For the dodecanoic ester derivatives, a nearly linear alkyl chain was observed. These longer alkyl derivatives show mesogenic behavior. 相似文献
463.
Jacek yczko Jacek Piotr Twardowski Bartomiej Skalny Renata Galek Antoni Szumny Iwona Gruss Dariusz Piesik Sebastian Sendel 《Molecules (Basel, Switzerland)》2021,26(9)
Rare carnivorous plants representing the genus Sarracenia are perceived as very interesting to scientists involved in various fields of botany, ethnobotany, entomology, phytochemistry and others. Such high interest is caused mainly by the unique capacity of Sarracenia spp. to attract insects. Therefore, an attempt to develop a protocol for micropropagation of the Sarracenia alata (Alph.Wood) Alph.Wood, commonly named yellow trumpets, and to identify the specific chemical composition of volatile compounds of this plant in vitro and ex vivo was undertaken. Thus, the chemical volatile compounds excreted by the studied plant to attract insects were recognized with the application of the headspace solid-phase microextraction (HS-SPME) coupled with the GC-MS technique. As the major volatile compounds (Z)-3-hexen-1-ol (16.48% ± 0.31), (E)-3-hexen-1-ol acetate (19.99% ± 0.01) and β-caryophyllene (11.30% ± 0.27) were identified. Further, both the chemical assumed to be responsible for attracting insects, i.e., pyridine (3.10% ± 0.07), and whole plants were used in in vivo bioassays with two insect species, namely Drosophila hydei and Acyrthosiphon pisum. The obtained results bring a new perspective on the possibilities of cultivating rare carnivorous plants in vitro since they are regarded as a valuable source of bioactive volatile compounds, as including ones with repellent or attractant activity. 相似文献
464.
Modern databases of small organic molecules contain tens of millions of structures. The size of theoretically available chemistry is even larger. However, despite the large amount of chemical information, the “big data” moment for chemistry has not yet provided the corresponding payoff of cheaper computer‐predicted medicine or robust machine‐learning models for the determination of efficacy and toxicity. Here, we present a study of the diversity of chemical datasets using a measure that is commonly used in socioeconomic studies. We demonstrate the use of this diversity measure on several datasets that were constructed to contain various congeneric subsets of molecules as well as randomly selected molecules. We also apply our method to a number of well‐known databases that are frequently used for structure‐activity relationship modeling. Our results show the poor diversity of the common sources of potential lead compounds compared to actual known drugs. © 2016 Wiley Periodicals, Inc. 相似文献
465.
466.
Andrzej Wawer Iwona Wawer Boguslawa Piekarska-Bartoszewicz Andrzej Temeriusz 《光谱学快报》2013,46(6):1079-1090
Abstract The acidic properties of ureido NH protons in two new derivatives of methyl 3,4,6-triacetyl-2-deoxy-β-D-glucopyranoside and i-butylamine (1) and L-leucine (2) were studied by 1H NMR. Stronger influence of polar aprotic solvents, more effective interaction with nitroxyl radical and faster H/D exchange indicate that N1'-H proton which is proximate to the glucopyranose ring is more acidic than N3'-H one in both ureido sugars, this conclusion was supported by semi-empirical AM1 calculation. Hydrogen to deuterium exchange rates are 1.2 x 10?2 to 5.5x 10?3 M?1 min?l. Significantly slower exchange of N3'-H proton standing by Leu residue in 2 can be explained by the existence of internal H-bonds. 相似文献
467.
Grażyna Janowska Agnieszka Kucharska-Jastrząbek Przemysław Rybiński Dorota Wesołek Iwona Wójcik 《Journal of Thermal Analysis and Calorimetry》2010,102(3):1043-1049
This paper presents the results of testing the flammability and fire hazard of butadiene (BR), butadiene-acrylonitrile (NBR)
and butadiene- styrene (SBR) rubbers with the use of oxygen index test, ignition temperature measurement, cone calorimetry
and inverse liquid chromatography. Toxicometric indices, RTFH CO/CO2, WLC50SM and the concentration of polycyclic aromatic hydrocarbons (PAH) have been determined. The results obtained have been interpreted
from the point of view of the chemical constitution of the polymers tested. 相似文献
468.
Tin(II/IV) phosphate was prepared by various synthetic methods. The different methods resulted in tin phosphate with different
properties, i.e., different crystalline form and behaviour during thermal treatment. The prepared materials have 3 mol water
of crystallisation, which they lose in different ways. Total mass loss was between 20 and 30%. This could be connected with
water loss, going generally in two steps in parallel with endothermic processes. At the end of thermal treatment, tin pyrophosphate
is obtained, irrespective of the method of preparation used. 相似文献
469.
Iwona E. Gowacka Anna Hartwich Iwona Rozpara Dorota G. Piotrowska 《Molecules (Basel, Switzerland)》2021,26(11)
Short and efficient syntheses of functionalized (pyrrolidin-2-yl)phosphonate and (5-oxopyrrolidin-2-yl)phosphonate have been developed. The synthetic strategy involved the diastereospecific 1,3-dipolar cycloaddition of N-benzyl-C-(diethoxyphosphoryl)nitrone to cis-1,4-dihydroxybut-2-ene and dimethyl maleate, respectively. O,O-Diethyl 3-carbamoyl-4-hydroxy(5-oxopyrrolidin-2-yl)phosphonate was obtained from O,O-diethyl 2-benzyl-4,5-dimethoxycarbonyl(isoxazolidin-3-yl)phosphonate by hydrogenation and subsequent treatment with ammonia, whereas transformation of O,O-diethyl 2-benzyl-4,5-dihydroxymethyl(isoxazolidin-3-yl)phosphonate into O,O-diethyl 3-aminomethyl-4-hydroxy(pyrrolidin-2-yl)phosphonate was accomplished by mesylation followed by hydrogenolysis to undergo intramolecular cyclization and the introduction of amino group via ammonolysis. Stereochemistry of the isoxazolidine cycloadducts, as well as the final functionalized (pyrrolidin-2-yl)- and (5-oxopyrrolidin-2-yl)phosphonates were established based on conformational analyses using vicinal H–H, H–P, and C–P couplings and supported by the observed diagnostic NOESY correlation signals. 相似文献
470.