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91.
In this paper, we discuss the electronic structure of alkali dimer molecules in 3Pig states on the surface of a helium droplet. The perturbation due to the droplet will in general not satisfy rotational symmetry around the internuclear axis of the diatom and thus, in addition to a broadening and blue shift, will cause a splitting of electronic levels that are degenerate in the free molecules. We propose a model based on general symmetry arguments and on a small number of physically reasonable parameters. We demonstrate that such a model accounts for the essential features of laser-induced fluorescence (LIF) and magnetic circular dichroism (MCD) spectra of the (1)3Pig-a3Sigma+ transition of Rb2 and K2. Furthermore the MCD spectra, analyzed according to the approach of Langford and Williamson [J. Phys. Chem. A 1998, 102, 2415], allow a determination of the populations of Zeeman sublevels in the ground state and thus a measurement of the surface temperature of the droplet. The latter agrees with the accepted temperature, 0.37 K, measured in the interior of a droplet. 相似文献
92.
Ernst Pittenauer Günter Allmaier 《Journal of the American Society for Mass Spectrometry》2009,20(6):1037-1047
Triacylglycerols were analyzed as cationized species (Li+, Na+, K+) by high-energy CID at 20 keV collisions utilizing MALDI-TOF/RTOF mass spectrometry. Precursor ions, based on [M+Li]+-adduct ions exhibited incomplete fragmentation in the high and low m/z region whereas [M+K]+-adducts did not show useful fragmentation. Only sodiated precursor ions yielded product ion spectra with structurally diagnostic
product ions across the whole m/z range. The high m/z region of the CID spectra is dominated by abundant charge-remote fragmentation of the fatty acid substituents. In favorable
cases also positions of double bonds or of hydroxy groups of the fatty acid alkyl chains could be determined. A-type product
ions represent the end products of these charge-remote fragmentations. B- and C-type product ions yield the fatty acid composition
of individual triacylglycerol species based on loss of either one neutral fatty acid or one sodium carboxylate residue, respectively.
Product ions allowing fatty acid substituent positional determination were present in the low m/z range enabling identification of either the sn-1/sn-3 substituents (E-, F-, and G-type ions) or the sn-2 substituent (J-type ion). These findings were demonstrated with synthetic triacylglycerols and plant oils such as cocoa
butter, olive oil, and castor bean oil. Typical features of 20 keV CID spectra of sodiated triacylglycerols obtained by MALDI-TOF/RTOF
MS were an even distribution of product ions over the entire m/z range and a mass accuracy of ±0.1 to 0.2 u. One limitation of the application of this technique is mainly the insufficient
precursor ion gating after MS1 (gating window at 4 u) of species separated by 2 u. 相似文献
93.
Schwizer D Patton JT Cutting B Smieško M Wagner B Kato A Weckerle C Binder FP Rabbani S Schwardt O Magnani JL Ernst B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(5):1342-1351
A new class of N-acetyl-D-glucosamine (GlcNAc) mimics for E-selectin antagonists was designed and synthesized. The mimic consists of a cyclohexane ring substituted with alkyl substituents adjacent to the linking position of the fucose moiety. Incorporation into E-selectin antagonists led to the test compounds 8 and the 2'-benzoylated analogues 21, which exhibit affinities in the low micromolar range. By using saturation transfer difference (STD)-NMR it could be shown that the increase in affinity does not result from an additional hydrophobic contact of the alkyl substituent with the target protein E-selectin, but rather from a steric effect stabilizing the antagonist in its bioactive conformation. The loss of affinity found for antagonists 10 and 35 containing a methyl substituent in a remote position (and therefore unable to support to the stabilization of the core) further supports this hypothesis. Finally, when a GlcNAc mimetic containing two methyl substituents (52 and 53) was used, in which one methyl was positioned adjacent to the fucose linking position and the other was in a remote position, the affinity was regained. 相似文献
94.
Albert A. Smith Matthias Ernst Sereina Riniker Beat H. Meier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(28):9483-9488
Nuclear magnetic resonance (NMR) relaxation data and molecular dynamics (MD) simulations are combined to characterize the dynamics of the fungal prion HET‐s(218‐289) in its amyloid form. NMR data is analyzed with the dynamics detector method, which yields timescale‐specific information. An analogous analysis is performed on MD trajectories. Because specific MD predictions can be verified as agreeing with the NMR data, MD was used for further interpretation of NMR results: for the different timescales, cross‐correlation coefficients were derived to quantify the correlation of the motion between different residues. Short timescales are the result of very local motions, while longer timescales are found for longer‐range correlated motion. Similar trends on ns‐ and μs‐timescales suggest that μs motion in fibrils is the result of motion correlated over many fibril layers. 相似文献
95.
Ernst Vidic 《Fresenius' Journal of Analytical Chemistry》1952,135(1):81-98
Zusammenfassung Der nephelometrische Nachweis des Morphins und Dilaudids nach Deckert ist für die Anzeige von Eukodal, Dicodid, Codein, Acedicon, Narcotin, Papaverin und Cocain nicht anwendbar, wenn diese Alkaloide, wie dies in der Praxis der Urinkontrolle suchtverdächtiger Personen fast ausschließlich der Fall ist, nur in geringeren Konzentrationen (unter 75g je 10 ml oder 7,5 mg je Liter) im Harn enthalten sind.Um möglichst alle Opiate und deren Derivate durch eine kurze Voruntersuchung auch in geringsten Mengen nachweisbar zu machen und dadurch eine rasche Entscheidung über die weitere Untersuchung möglich zu machen bzw. einwandfrei negativ reagierende Urine ausscheiden zu können, wurde eine neue Schnellmethode entwickelt. Diese Methode kann in einfacher, zeitsparender Weise mit der Prüfung nach Deckert verbunden werden und beruht auf charakteristischen Trübungsreaktionen mit den Halogenen Brom und Jod. Bei der Durchführung der Reaktionen in essigsaurem Medium wird durch Anwendung von Brom- und Jodlösungen bestimmter Zusammensetzung, je nachdem, ob dieselben einzeln oder zugleich den nach Deckert hergestellten Extraktlösungen hinzugefügt werden, nicht nur eine zuverlässige Anzeige, sondern auch eine gewisse Differenzierung der einzelnen Alkaloide ermöglicht. Die Empfindlichkeit der Reaktionen ist ausreichend groß, so daß mit einer Urinmenge von 20 ml — bzw. 10 ml bei allgemeiner Opiatanzeige mit beiden Halogenen zugleich — das Auslangen gefunden wird.Mit normalen, opiatfreien Urinen werden einwandfreie Blindproben erhalten, welche sich auch von den schwach positiven Befunden deutlich unterscheiden und dadurch eine große Sicherheit in der Anzeige geringster Opiatgehalte bedingen.Bei der Überprüfung des Verhaltens einer größeren Zahl von Arzneistoffen konnte festgestellt werden, daß eine Vortäuschung von Opiaten durch diese Stoffe nicht zu befürchten ist. Die als Störsubstanzen in Betracht kommenden Analgetica Polamidon, Dolantin und mit Einschränkung auch Cliradon sind ebenso wie Chinin leicht und rasch durch die Reaktion mit Bromkresolgrün zu erkennen. Die Halogenmethode besitzt demnach einen bedeutenden Grad von Spezifität. 相似文献
96.
Treatment of transition-metal—ammonia complexes with ketones yields complexes with RR′CNH ligands. Of particular interest is the stabilization of dialkylketimines such as e.g. (CH3)2CNH and C6H10NH in [M(CO)5{NHC(CH3)2}] or [M(CO)5 {NHC6H10}] (M = Cr, Mo, W). The principle of synthesis may be applied to a wide range of different metals and types of complexes, as can be shown by the synthesis of [C5H5Mn(CO)2 {NHC(CH3)2}], [C5H5Fe(CO)2{NHC(CH3)2}]PF6, [M(CO)4L2] (M = Cr, Mo, W; L = (CH3)2CNH, C6H10NH) and [W(CO)3(diphos){NHC(CH3)}2]. Treatment of [Cr(CO)5NH3] with urotropine gives [Cr(CO)5 {N4(CH2)6}] which is also obtained from [Cr(CO)5THF] and urotropine. The methods of preparation, reactions and spectroscopic properties of the complexes are reported. 相似文献
97.
98.
Wolfgang Scherer Prof. Dr. Christoph Hauf Dipl.‐Phys. Manuel Presnitz Dipl.‐Phys. Ernst‐Wilhelm Scheidt Dr. Georg Eickerling Dr. Volker Eyert Dr. Rolf‐Dieter Hoffmann Dr. Ute C. Rodewald Dipl.‐Ing. Adrienne Hammerschmidt Dr. Christian Vogt Dr. Rainer Pöttgen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(9):1578-1582
99.
100.
Johannes Tauer Heinrich Kofler Elisabeth Schwarz Ernst Wintner 《Central European Journal of Physics》2010,8(2):242-248
Laser ignition is considered to be one of the most promising future concepts for internal combustion engines. It combines the legally required reduction of pollutant emissions and higher engine efficiencies. The igniting plasma is generated by a focused pulsed laser beam. Having pulse durations of a few nanoseconds, the pulse energy E p for reliable ignition amounts to the order of 10 mJ. Different methods of laser ignition with an emphasis on fiber-based systems will be discussed and evaluated. 相似文献