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991.
Lenka Nezbedov Konstantin Drandarov Christa Werner Manfred Hesse 《Helvetica chimica acta》2000,83(11):2953-2960
The asymmetric synthesis of the unlabeled and [D8]‐labeled terminal precursors, 4 ((−)‐(S)‐dihydroxyverbacine) and 19 , respectively, in the biogenesis of the spermine alkaloids aphelandrine ( 5 ) and orantine ( 6 ), respectively, is described. A partial synthesis of the alkaloid (−)‐(S)‐[(E)‐4‐methoxycinnamoyl]buchnerine ( 10 ) is also presented. 相似文献
992.
The lyophilized venom of the spider Paracoelotes birulai (Araneidae: Amaurobiidae) has been analyzed. A number of acylpolyamines were found and separated. By on‐line coupled high‐performance liquid chromatography and atmospheric‐pressure chemical‐ionization mass spectrometry, the structures of the three most abundant compounds PB 490 (N‐(16‐guanidino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxyindol‐3‐yl)acetamide; Fig. 3, b), PB 421 (N‐(16‐guanidino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxybenzamide; Fig. 4, a), and PB 448 (N‐(16‐amino‐4‐hydroxy‐4,8,12‐triazahexadecyl)‐2‐(4‐hydroxyindol‐3‐yl)acetamide; Fig. 5,b) were elucidated. Two different types of polyamines were found in the α‐palutoxins and compared with acylpolyamines from the Agelenidae spider family. The results of this investigation will initiate further chemotaxonomical studies on spiders. 相似文献
993.
Peter Müller‐Buschbaum Jochen S. Gutmann Manfred Stamm Robert Cubitt 《Macromolecular Symposia》2000,149(1):283-288
The surface structure of thin polymer blend films of deuterated polystyrene (dPS) and polyparamethylstyrene (PpMS) after annealing above the glass transition temperature was investigated. With scanning force microscopy (SFM) the surface topography originated by a dewetting process is detected. The sample surface is covered with small droplets consisting of several polymer molecules. Utilizing grazing incidence small angle neutron scattering (GISANS) the topographical information as well as the in‐plane composition is probed. For thin confined blend films a substructure of the droplets resulting from an additional phase separation process at different length scales is detected. 相似文献
994.
As shown in the Scheme, 3-(1-nitro-2-oxocyclooctyl)propanal ( 1 ) prepared earlier from cyclooctanone was converted into the 14-membered lactones 6 and 7 . The aldehyde 1 was submitted to allylation to give 2 using allyltitnium or allylsilicon reagents. After lactonizatrion and transformation of the C,C-double bond to an alcohol, 4 was translactonized under acidic conditions to form 5 , from which 6 and 7 were prepared. 相似文献
995.
Demetrio De la Calle García Manfred Reichenbcher Klaus Danzer Christian Hurlbeck Christine Bartzsch Karl-Heinz Feller 《Journal of separation science》1998,21(7):373-377
Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds. 相似文献
996.
Nikolay Youhnovski Laurent Bigler Christa Werner Manfred Hesse 《Helvetica chimica acta》1998,81(9):1654-1671
A H2O/MeOH extract of the pollen of Hippeastrum x hortorum (Amaryllidaceae) was analyzed. A mixture of different compounds (at the most 84) was found, namely the geometrically ((E,E), (E,Z), (Z,E), and (Z,Z) and structurally isomeric N,N′-dicoumaroyl (=N,N′-bis[3-(4-hydroxyphenyl)prop-2-enoyl]), N,N′-diferuloyl (=N,N′-bis[3-(4-hydroxy-3-methoxyphenyl)prop-2-enoyl]), N,N′-disinapoyl (=N,N′-bis[3-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-enoyl]), N-coumaroyl-N′-feruloyl, and N-feruloyl-N′-sinapoyl derivatives of spermidine (=4-azaoctane-1,8-diamine=N-(3-aminopropyl)butane-1,4-diamine). Their structures were proven by using on-line-coupled high-performance liquid chromatography and atmospheric-pressure chemical-ionization mass spectrometry (HPLC-UV(DAD)/APCI-MS and MS/MS), UV-induced (E)⇌(Z) photoisomerization, and catalytic hydrogenation, as well by comparing their spectra and chromatographic behavior with those of synthetic standards. According to the physicochemical properties of these natural compounds, a proposed biological function is discussed. 相似文献
997.
998.
999.
Manfred Rätzsch Hartmut Bucka Achim Hesse Norbert Reichelt E. Borsig 《Macromolecular Symposia》1998,129(1):53-77
Radical reactions of i-PP are a well known technical process for the chemical degradation to increase the flowability of the i-PP melt. By decreasing the temperature and increasing the life time of the PP-radicals, a process to synthesize long chain branched i-PP, was developed. The long chain branched-i-PP allows to introduce the i-PP in processing technologies as blow moulding film technology or foaming technology. The mechanism will be discussed. The radical grafting of Polypropylene (PP) becomes more important for the developing of PP-alloys with extended properties. Methylmethacrylate and styrene were polymerized and grafted in PP at low temperatures in solid state. Grafting and polymerizing in solid state means solving the monomers in the PP-powder directly from the reactor without contacting with oxygen (air). The reaction is started by the thermal decomposition of a peroxide. The reactivity of the primary radicals from the peroxide and the transfer reactions of the polymer radical of the PMMA or PS influences the amount of the grafted polymer. The solubility of the monomers and the peroxide in the amorphous i-PP-phase was measured. The grafting yield and the dispersity of the second polymer depends on the solubility and dispersity of peroxide and monomers in the PP-powder particles. 相似文献