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991.
Pałasz A 《Organic & biomolecular chemistry》2005,3(17):3207-3212
Cycloadditions of 3-aryl-2-benzoyl-2-propenenitriles and 3-phenylsulfonyl-3-buten-2-one to N-vinyl-2-oxazolidinone proceed regio- and diastereoselectively yielding cis and trans diastereoisomers of 4-aryl-3,4-dihydro-2-(2-oxo-3-oxazolidinyl)-2H-pyrans in 37-65% yield. Cycloadducts cis- were the major products. Reaction of 5-arylidene-1,3-dimethylbarbituric acids with dienophile afforded mixtures of 2H-pyrano[2,3-d]pyrimidine-2,4(3H)-diones trans and products resulted from an elimination of 2-oxazolidinone, in 50-52% yield. To confirm the experimental results, semiempirical AM1 and PM3 calculations of frontier orbital energies have been performed. 相似文献
992.
Stanislaw Zieliński Lechosław Łomozik Anna Wojciechowska 《Monatshefte für Chemie / Chemical Monthly》1982,113(3):323-330
The formation and the mode of coordination of rare earth (Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) complexes with proline and hydroxyproline have been investigated by1H and13C NMR spectral techniques. It has been established that the nitrogen and the carboxyl group of the ligands are involved in complexation, and that the OH– group of hydroxyproline does not participate in coordination.
1H und13C NMR Untersuchungen an Lanthanid-Komplexen mit Prolin und Hydroxyprolin
Zusammenfassung Die Bildung und die Koordination von seltenen Erden (Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu) in Komplexen mit Prolin und Hydroxyprolin wurden mit Hilfe von1H- und13C-NMR-Spektroskopie untersucht. Es wurde festgestellt, daß in den Komplexen der Stickstoff und der Carboxylsauerstoff der Liganden koordinieren. Die OH–-Gruppe von Hydroxyprolin nimmt keinen Anteil an der Koordinierung.相似文献
993.
A concise and efficient synthesis of the C13 tricyclic core of the dihydro-β-agarofuran skeleton common to the natural Celastraceae sesquiterpenoids is described. The strategy entails a Mukaiyama aldol reaction of a tetrahydronaphthalene enol silane with acetone, epoxidation, ketone reduction, and acid-catalyzed cyclization. This key scaffold was converted into diverse polyhydroxylated derivatives, which were tested for insecticidal activity. 相似文献
994.
Agnieszka Majchrzak Aleksandra Janczak Grzegorz Mlosto Anthony Linden Heinz Heimgartner 《Helvetica chimica acta》2003,86(6):2272-2283
The smooth reaction of 3‐chloro‐3‐(chlorosulfanyl)‐2,2,4,4‐tetramethylcyclobutanone ( 3 ) with 3,4,5‐trisubstituted 2,3‐dihydro‐1H‐imidazole‐2‐thiones 8 and 2‐thiouracil ( 10 ) in CH2Cl2/Et3N at room temperature yielded the corresponding disulfanes 9 and 11 (Scheme 2), respectively, via a nucleophilic substitution of Cl? of the sulfanyl chloride by the S‐atom of the heterocyclic thione. The analogous reaction of 3‐cyclohexyl‐2,3‐dihydro‐4,5‐diphenyl‐1H‐imidazole‐2‐thione ( 8b ) and 10 with the chlorodisulfanyl derivative 16 led to the corresponding trisulfanes 17 and 18 (Scheme 4), respectively. On the other hand, the reaction of 3 and 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5(4H)‐thione ( 12 ) in CH2Cl2 gave only 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazol‐5(4H)‐one ( 13 ) and the trithioorthoester derivative 14 , a bis‐disulfane, in low yield (Scheme 3). At ?78°, only bis(1‐chloro‐2,2,4,4‐tetramethyl‐3‐oxocyclobutyl)polysulfanes 15 were formed. Even at ?78°, a 1 : 2 mixture of 12 and 16 in CH2Cl2 reacted to give 13 and the symmetrical pentasulfane 19 in good yield (Scheme 5). The structures of 11, 14, 17 , and 18 have been established by X‐ray crystallography. 相似文献
995.
M. Zieliński A. Zielińska H. Papiernik-Zielińska G. Czarnota G. Kasprzyk J. A. McKenzie H. Paul S. Bernasconi 《Journal of Radioanalytical and Nuclear Chemistry》1997,223(1-2):41-45
The13C fractionation has been studied in the reaction of phenylacetylene with the excess of liquid Merck formic acid at 30 and 40 °C to see the contribution of the13C fractionation in the formolysis of transient -formoxystyrene to the experimentally observed global13C fractionation. The13C fractionation has been investigated also in the hydration of 1 ml of PhCCH with 1 ml of formic acid in the temperature interval of 80–100°C. The13C KIE equal to 1.0168 at 91.75 °C and 1.0167 at 100°C indicate that the self-decomposition of formic acid in such experimental conditions is already largely suppressed. The isotope effect is discussed within the framework of the sequence of reaction steps leading to acetophenone and carbon monoxide production listed in part I. 相似文献
996.
Viktor Krchňák Aleksandra S. Weichsel Dasha Cabel Zuzka Flegelova Michal Lebl 《Molecular diversity》1996,1(3):149-164
Summary We have designed and synthesized structurally homogeneous and heterogeneous nonpeptide libraries. Structurally homogeneous libraries are characterized by the presence of one common structural unit, a scaffold, in all library compounds (e.g. cyclopentane, cyclohexane, diketopiperazine, thiazolidine). In structurally heterogeneous libraries different organic reactions (acylation, etherification, reductive amination, nucleophilic displacement) were applied to connect bifunctional building blocks unrelated in structure (aromatic hydroxy acids, aromatic hydroxy aldehydes, amino alcohols, diamines, and amino acids). The focus of this communication is to document the use of bifunctional building blocks for the design and synthesis of structurally heterogeneous libraries ofN-(alkoxy acyl)amino acids, N,N-bis-(alkoxy acyl)diamino acids,N-acylamino ethers,N-(alkoxy acyl)amino alcohols,N-alkylamino ethers, andN-(alkoxy aryl)diamines.Abbreviations AcOH
acetic acid
- DCE
dichloroethane
- DCM
dichloromethane
- DEAD
diethyl azodicarboxylate
- DIAD
diisopropyl azodicarboxylate
- DIC
diisopropyl carbodiimide
- DIEA
diisopropylethylamine
- DMAP
dimethylaminopyridine
- DMF
dimethylformamide
- Fmoc
fluorenylmethyloxycarbonyl
- HOBt
N-hydroxybenzotriazole
- MeCN
acetonitrile
- MeOH
methanol
- NaOH
sodium hydroxide
- PEG/PS
polyethylene-grafted copolystyrene
- PPh3
triphenylphosphine
-
t-Bu
tert- butyl
- TFA
trifluoroacetic acid
- TG
TentaGel
- THE
tetrahydrofuran 相似文献
997.
998.
999.
A simple and sensitive method for simultaneous analysis of 43 pharmaceutical compounds in sewage sludge and sediment samples was developed and validated. The target compounds were extracted using pressurized liquid extraction (PLE) and then purified and pre-concentrated by solid phase extraction (SPE) using a hydrophilic-lipophilic balanced polymer. PLE extraction was performed on temperature of 100 °C, with methanol/water mixture (1/2, v/v) as extraction solvent. The quantitative analysis was performed by liquid chromatography tandem mass spectrometry using a hybrid triple quadrupole-linear ion trap mass spectrometer (LC-QqLIT-MS). Data acquisition was carried out in selected reaction monitoring (SRM) mode, monitoring two SRM transitions to ensure an accurate identification of target compounds in the samples. Additional identification and confirmation of target compounds were performed using the Information Dependent Acquisition (IDA) function. The method was validated through the estimation of the linearity, sensitivity, repeatability, reproducibility and matrix effects. The internal standard approach was used for quantification because it efficiently corrected matrix effects. Despite the strong matrix interferences, the recoveries were generally higher of 50% in both matrixes and the detection and quantification limits were very low. Beside the very good sensitivity provided by LC-QqLIT-MS, an important characteristic of the method is that all the target compounds can be simultaneously extracted, treated and analysed. Hence, it can be used for routine analysis of pharmaceuticals providing large amount of data. The method was applied for the analysis of pharmaceuticals in river sediment and wastewater sludge from three treatment plants with different treatment properties (i.e. capacity, secondary treatment, quality of influent waters). The analysis showed a widespread occurrence of pharmaceuticals in the sludge matrices. 相似文献