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991.
Waldemar Adam Hector Rebollo Heinz Dürr Karl-Heinz Pauly Karl Peters Eva-Maria Peters Hans-Georg von Schnering 《Tetrahedron letters》1982,23(9):923-926
4-Methyl-1,2,4-triazoline-3,5-dione (MTAD) gives with 7-spiro-fluorenyl-1,3,5-cycloheptatriene () initially he norcaradine-type urazole () which at ambient temperatures rearranges into (), while 102 gives the tropilidene-type endoperoxide (). 相似文献
992.
Binuclear redox sites consisting of a Zr oxo-bridged to a Cu(I) center have been obtained on the pore surface of MCM-41 silicate sieve by a stepwise grafting procedure, along with isolated metal centers. The bimetallic site features a Zr(IV)-O-Cu(I) to Zr(III)-O-Cu(II) metal-to-metal charge-transfer (MMCT) absorption extending from the UV region to about 500 nm. The Zr-O-Cu linkage is revealed by a Cu(I)-O infrared stretch mode at 643 cm-1. Irradiation of the MMCT chromophore of ZrCu(I)-MCM-41 loaded with 1 atm of CO2 gas at room temperature resulted in growth of CO (2150 cm-1) and H2O (1600 cm-1). Photolysis experiments using 13CO2 and C18O2 demonstrate that carbon monoxide and the oxygen atom of the water product originate from CO2. This indicates splitting of the CO2 by the excited MMCT moiety to CO and a surface OH radical, followed by trapping of the products at Cu(I) centers (OH is reduced to H2O). This is the first observation of CO2 photoreduction at a binuclear MMCT site at the gas-solid interface. 相似文献
993.
Anthony Linden Enas M. Awad Nehal M. Elwan Hamdi M. Hassaneen Heinz Heimgartner 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o122-o124
Crystals of the title compound, C23H17ClN4O2·2.5H2O, contain channels filled with highly disordered water molecules. The best structure refinement was obtained by removing the solvent contribution from the intensity data and refining against a solvent‐free model. The central six‐membered ring of the quinolizine molecule has a slightly distorted screw‐boat conformation. 相似文献
994.
Heinz Löster 《Monatshefte für Chemie / Chemical Monthly》2005,136(8):1443-1466
Summary. The metabolism in the heart prefers long-chain fatty acids to other substrates. L-Carnitine, a co-factor of coenzyme A, plays an essential role in the transport of long-chain fatty acids through the inner mitochondrial membrane. Without carnitine, metabolisation of long-chain fatty acids in the mitochondria is not possible. In addition, acyl groups from acyl-CoA compounds can be transferred to L-carnitine, thus influencing the enzymatic activities of important mitochondrial enzymes.The isolated heart model developed by Langendorff was used to investigate the effects of L-carnitine on the heart. During aerobic perfusion, the hemodynamic parameters of isolated hearts reacted in a very sensitive way to alterations in the external conditions (temperature, preload, composition of the perfusion solution). During postischemic perfusion, recovery of the hearts was also influenced by the composition of the perfusion. The hemodynamic parameters of the reperfused hearts increased markedly if there was a sufficiently high supply of long-chain fatty acids and/or glucose. The insufficient recovery of hearts perfused without glucose and at low fatty acid concentrations could be improved by adding L-carnitine. Determination of carnitine levels in heart tissue found that the heart loses about 30% of its carnitine content during ischemia, and that exogenous carnitine is taken up by the heart during reperfusion. There it effects the restoration of sufficient concentrations of creatine phosphate and ATP, a fact that was confirmed by 31P NMR spectroscopy. NMR spectroscopy also established that L-carnitine lessens the harmful effects of ischemia-induced metabolic acidosis.The favourable influence of L-carnitine on the heart in the reperfusion period could be due to a reduction in oxygen radicals (lowering of MDA concentrations during reperfusion, raising of GPx and SOD activities).The findings of these experiments on isolated hearts as well as the favourable results of two placebo-controlled and double-blind clinical studies (investigating the effects of carnitine in cardiomyopathy patients and the effects of L-carnitine in hemodialysis patients) demonstrate that L-carnitine produces positive therapeutic effects, particularly in heart and circulatory diseases. 相似文献
995.
Ren Traber Max Kuhn Artur Rüegger Heinz Lichti Hans-Rudolf Loosli Albert von Wartburg 《Helvetica chimica acta》1977,60(4):1247-1255
The Structure of Cyclosporin C The structure of cyclosporin C ( 2 ), a minor antifungal metabolite from Trichoderma polysporum (Link ex Pers.) RIFAI has been elucidated. Hydrolytic cleavage and spectroscopic evidence show that cyclosporin C is a neutral oligopeptide of 11 amino acids linked together in a 33-membered ring. Cyclosporin C ( 2 ) differs from the main metabolite cyclosporin A ( 1 ) [2] [4] only by containing L-threonine in the place of L-α-aminobutyric acid as has been shown by the conversion of 2 into 1 . 13C-NMR. spectra and study of molecular models suggest that cyclosporin C ( 2 ) has the same molecular conformation as 1 , which is best described as a twisted β-pleated sheet held together in a conformationally stable form by intramolecular hydrogen bonding. 相似文献
996.
Dieter Fenske Heinz Teichert Heinz Prokscha Werner Renz Hermann J. Becher 《Monatshefte für Chemie / Chemical Monthly》1980,111(1):177-191
The unusual properties of bis(diphenylphosphino)maleic anhydride and similar ditertiary phosphines has prompted the synthesis of analogous arsines and stibines. Bis(diphenylarsino)maleic anhydride,-maleic thioanhydride and-N-methyl maleic imide, bis(diphenylstibino)maleic anhydride (5) and-maleic thioanhydride are obtained as crystalline yellow or red compounds by the reaction of the corresponding 2,3-dichloromaleic acid derivatives with diphenyl(trimethylsilyl)arsine and-stibine resp. The uv/vis spectra and characteristic i.r. bands of selected compounds are given and compared with those of the corresponding phosphines. The strong shift of C=C to lower wavenumbers observed in all compounds has caused the determination of crystal and molecular structure of5 by x-ray diffraction. Bond distances and angles are given. The complex formation of the new diarsine ligands has been examined by the preparation of Ni-, Cr- and Mo-carbonyl derivatives. As the first organylsulfane substituted maleic acid derivatives bis(phenylthio)maleic thioanhydride,-N-methyl-maleic imide and-maleic acid dimethylester are synthesized and described. 相似文献
997.
As the first set of stereomeric donor-acceptor cyclophanes with TCNQ as an acceptor, and were synthesized; their charge-transfer absorptions differ strongly as a consequence of the different donor-acceptor orientation. 相似文献
998.
Heinz Lster Rainer Herzschuh Eberhard Lippmann 《Journal of mass spectrometry : JMS》1980,15(4):167-171
The mass spectra of S-(1-aryltetrazol-5-yl)-monothiocarbonic acid esters have been studied. The stability of the ester molecular ions is lower than the stability of the corresponding 1-aryl-5-mercaptotetrazoles. Substituents at the phenyl group increase the stability, whereas the influence of the ester alkyl groups is very small. The esters undergo fragmentation via four different fragmentation pathways. The elimination of carbon dioxide is influenced by an ‘ortho effect’ of the substituents. 相似文献
999.
Heinz Balli Thomas Eichenberger Bruno Hellrung Peter Scheibli 《Helvetica chimica acta》1985,68(5):1394-1400
Photoisomerization and Relaxation of Symmetrical Triazacarbocyanine Dyes in an Alcoholic Mixture at Low Temperature The partial photobleaching of a series of symmetrical triazacarbocyanine dyes with different heterocycles in EtOH/MeOH/i-PrOH at low temperature (110 to 250 K) was investigated by UV/VIS spectra. Kinetic data of the dark reaction of photobleached compounds are given. The effect of electron-donating or -accepting substituents, respectively, and of protonation of the photobleached compound on kinetic data and on UV/VIS spectra was studied. Products of photobleaching and mechanisms of the dark reaction are discussed. 相似文献
1000.
The Cope Rearrangement, a Reaction for Repeatable Ring Expansions Starting with the unsaturated β-ketoesters of type I, a vinyl group is introduced into the β-position by 1,4-addition of vinyl magnesium chloride to give II (Scheme 3). Treatment of the β-ketoester II with phenyl vinyl sulfoxide in the presence of sodium hydride yields the sulfoxides III, which on thermolysis lead to the α, β-divinyl ketoesters of type IV via elimination of sulfinic acid (Scheme 3). The Cope-System IV undergoes rearrangement to V, which is again an unsaturated β-ketoester. The latter is suitable for a further ring expansion sequence. These reaction steps were carried out with the nine-, twelve- and fifteen-membered ketoesters 32, 33 and 34 , as well as with the open-chain compound 35 (Table 1). With the cyclohexane derivative 31 , ring expansion could not be achieved with the described sequence. 相似文献