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101.
The interaction of ethidium bromide (2,7-diamino-10-ethyl-9-phenylphenanthridinium bromide; EB) with double stranded (ds) calf thymus DNA and thermally denatured single stranded (ss) DNA was studied in solution and at the electrode surface by means of transfer voltammetry using a carbon paste electrode (CPE) as working electrode in 0.2 M acetate buffer, pH 5.0. As a result of intercalation of this dye between the base pairs of dsDNA, the characteristic peak of dsDNA, due to the oxidation of guanine residues, decreased and after a particular concentration of EB a new peak at +0.81 V appeared, probably due to the formation of a complex between dsDNA and EB. The non-intercalated EB gives another peak, but at an increased concentration of the dye. A similar behaviour was observed during the interaction of the dye with ssDNA.Furthermore, the interaction of EB with ds, ss and supercoiled (sc) DNA was studied at the hanging mercury drop electrode (HMDE) surface by means of alternating current voltammetry in 0.3 M NaCl and 50 mM sodium phosphate buffer (pH 8.5) as supporting electrolyte. dsDNA yields a smaller peak at −1.42 V (peak III) compared to the one yielded by ssDNA, since the latter is a relaxed and more accessible form. By addition of EB into the buffer solution an increase of peak III was observed in the dsDNA form as well as in ssDNA resulting from their interaction with EB. Furthermore, the appearance of peak III in covalently closed circular scDNA after exposure to increasing concentrations of EB is a result of the introduction of ‘free ends’ in DNA affecting its structural integrity. 相似文献
102.
M. M. Abd-Elmeguid Ch. Sauer U. Köbler W. Zinn 《Zeitschrift für Physik B Condensed Matter》1985,60(2-4):239-248
X-ray diffraction,151Eu Mössbauer effect (ME) and magnetic susceptibility measurements have been performed to investigate the valence behavior and the magnetic interactions of the Eu ions in the intermetallic series Eu(Pd1–x
Au
x
)2Si2 (0x1) as a Forx>0.4 all experimental techniques are in agreement with each other and suggest a divalent 4f
7 ground state of the Eu ion. Belowx=0.4 the different methods lead to different results: while the lattice parameters and the ME isomer shift suggest an instable behavior of the valence the magnetic susceptibility proves a pure divalent 4f
7 ground state. These differences can be explained by assuming a partial extension of the 4f-shell radius such that the localized character of the 4f-electrons is preserved.Dedicated to B. Mühlschlegel on the occasion of his 60th birthday 相似文献
103.
J.A. Bajgrowicz A. El Hallaoui R. Jacquier Ch. Pigière Ph. Viallefont 《Tetrahedron letters》1984,25(26):2759-2762
The lithium diorganocuprate reactions with L-serine derivatives are studied. Retention of configuration, or at least a high enantiomeric excess (>80%) of the formed α-amino esters is observed in all cases. Attempts are made to restrict side-reactions. 相似文献
104.
Zusammenfassung Der zeitliche Verlauf der Farbstoffaufnahme an den beiden aufeinanderliegenden Al2O3-Schichten bei anodisch oxydiertem Aluminium wird in beiden F?llen durch die „Anlaufparabel“ dargestellt.
Die Gültigkeit dieser Gleichung best?tigt die Bildung eines Lackes zwischen dem benutzten Farbstoff und dem Aluminiumoxyd
bei beiden Schichten.
Die Geschwindigkeitskonstante für die erste Schicht desx
1-Al2O3 ist der Stromdichte proportional, mit welcher die Oxydation vorgenommen wurde; für die zweite Schicht desx
2-Al2O3 ist dasK″ unabh?ngig von der Stromdichte.
In dem Diagramm desK″ gegen die Stromdichte zeigt sich ein Sprung in den Eigenschaften der beiden Schichten bei 8600 Coul/dm2 (9,55 A/dm2 · 15 · 60), d.h. an demselben Punkt, an dem er sich auch in der Arbeit (1) gezeigt hatte. Diese Lage des Sprunges best?tigt
die Messungen und die Ergebnisse der beiden Arbeiten.
Au?erdem wurde so von neuem bewiesen, da? an der Grundschicht anliegendesx
1-Al2O3 por?s ist und infolgedessen die Geschwindigkeit der Farbstoffaufnahme von seiner Gesamtoberfl?che abh?ngt, d. h. von seiner
Dicke (1) und deshalb von der Stromdichte.
Im Gegensatz dazu ist die daraufliegende Schicht vonx
2-Al2O3 weniger por?s; infolgedessen ist die Geschwindigkeit der Farbstoffaufnahme unabh?ngig von seiner Dicke (1) und von der Stromdichte,
mit der die Oxydation durchgeführt worden ist (1).
Die Gültigkeit der Arrheniusschen Gleichung für beide Schichten erlaubt auch die Bestimmung der Aktivierungsenergie, deren
Wert (identisch für beide Schichten), auf Grund der Theorie der Fehlordnung und der Gültigkeit der Anlaufparabel, den Ablauf
einer Platzwechselreaktion beweist.
Durch die vorliegende Arbeit im Zusammenhang mit der Arbeit (1) wurde das Bild von der anodischen Oxydation des Aluminiums
und von der Farbstoffaufnahme vervollst?ndigt, sowohl vom Standpunkt der Sekund?rstruktur des Oxyds (hier wurde zum erstenmal
die Anwesenheit von zwei übereinanderliegenden Oxydschichten in der Zone der Hauptschicht mit deutlich verschiedenen Eigenschaften
bewiesen), als auch vom Standpunkt der Reaktionskinetik aus (hier wurde der Reaktionsmechanismus aufgedeckt). 相似文献
105.
Raschig rings used as a safety mechanism, to avoid critical reactions in solutions containing radioactive materials, are usually made of borosilicate glass. Since boron is the active neutron absorbing ingredient, it is important to determine the boron content in the Raschig rings at any given time. A method has been developed to determine rapidly the boron content of borosilicate glasses. Ion exchange and potentiometric measurement are used to determine boron as the tetrafluoroborate ion. The precision of the method is ±2.0 mV. The average difference between values of a wet chemical analysis and those of the potentiometric method is 7.7%. 相似文献
106.
107.
Zh. Bo J. H. Yan X. D. Li Y. Chi K. F. Cen B. G. Chéron 《Plasma Chemistry and Plasma Processing》2007,27(5):546-558
The combined effects of oxygen and water vapor on three typical volatile organic compounds, i.e. tetrachloromethane, n-butane and toluene, decomposition efficiency under gliding arc gas discharge conditions are studied. The electron density
and the density of the reactive radicals such as O and OH are modified by addition of oxygen and water vapor. Consequently,
the decomposition process can be enhanced or suppressed, depending on the involved chemical structures and reaction channels.
The addition of oxygen and water vapor suppresses the tetrachloromethane decomposition which indicates that this process is
mainly controlled by the electron dissociation reactions. By contrast, the n-butane and toluene decompositions are enhanced, which shows that they can be mainly ascribed to the radical induced reactions.
Especially, in a moist atmosphere the OH radicals are supposed to play the most important role in the n-butane decomposition process. 相似文献
108.
W. Koenig F. -W. Richter J. Ch. Bode B. Meinel 《Journal of Radioanalytical and Nuclear Chemistry》1980,58(1-2):327-339
Multi-element-analysis by PIXE in respect to medical applications is discussed. Examples of trace-element determinations in
liver tissues are given, demonstrating the applicability and usefulness of this rather new analytical technique.
相似文献
109.
Thermal Properties of Hot-Stage Extrudates of Itraconazole and Eudragit E100. Phase separation and polymorphism 总被引:1,自引:0,他引:1
Six K. Leuner Ch. Dressman J. Verreck G. Peeters J. Blaton N. Augustijns P. Kinget R. Van den Mooter G. 《Journal of Thermal Analysis and Calorimetry》2002,68(2):591-601
Solid dispersions of itraconazole and eudragit E100 were prepared by hot-stage extrusion. Analysis of the physical structure
revealed the existence of different phases, depending on the manufacturing condition. Extrudates prepared at 453 K existed
as a molecular dispersion of itraconazole in eudragit E100 when the drug concentration did not exceed ca. 13% mass/mass. At
higher concentrations, a second phase consisting of pure glassy itraconazole emerged. In other dispersions prepared at 413
K, the second phase consisted of pure crystalline itraconazole. The difference can be attributed to the relation of the process-temperature
to the melting point. Heating of both dispersions induced cold crystallization. Extrudates prepared at 453 K showed comparable
behavior before and after milling, with the exception that unmilled dispersions with a drug load of ≥60% mass/mass recrystallized
upon heating into a polymorphic modification of itraconazole (T
m=431 K). Upon further heating the polymorph recrystallized to the stable crystalline form (T
m=441 K).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
110.
J. Voll T. Kerscher D. Geppert R. de Vivie-Riedle 《Journal of photochemistry and photobiology. A, Chemistry》2007,190(2-3):352-358
The technological needs imposed by the exponential miniaturization trend of conventional electronic devices has drawn attention towards the development of smaller and faster devices like ultrafast molecular switches. In recent years molecular switches emerge again in the focus of active and innovative research with state-of-the-art optical tools recording their dynamics in real time. Still many questions about the underlying microscopic mechanism are left open, including potential factors that effect the switching process in either way, improve or worsen it. Due to the complexity of such molecules it is difficult to obtain a global answer from experiment alone. On the other side molecular switches are generally too large for a complete quantum chemical and quantum dynamical calculation. In our group we therefore developed an ab initio based modular model to handle the laser induced quantum dynamics in molecular switches like fulgides. It enables us to study the effect of internal molecular coupling and of the molecular response to external fields. We can investigate the related wave packet dynamics, the switching efficiency and the controllability. Our results focus on the laser induced ring opening in fulgides, which equals one direction of the switching process. Presented are the influence of a conical intersection seam and of time-dependent potentials, mimicking the mean interaction with the environment. Furthermore the relation of controllability and the wave packet's momentum is studied and the influence of potential barriers on the switching dynamics is shown. 相似文献