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31.
János Osán Szabina Török Bálint Alföldy Anita Alsecz Gerald Falkenberg Soo Yeun Baik René Van Grieken 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
The rivers in the Hungarian Upper Tisza Region are frequently polluted mainly due to mining activities in the catchment area. At the beginning of 2000, two major mining accidents occurred in the Romanian part of the catchment area due to the failure of a tailings dam releasing huge amounts of cyanide and heavy metals to the rivers. Surface sediment as well as water samples were collected at six sites in the years 2000–2003, from the northeast-Hungarian section of the Tisza, Szamos and Túr rivers. The sediment pollution of the rivers was compared based on measurements of bulk material and selected single particles, in order to relate the observed compositions and chemical states of metals to the possible sources and weathering of pollution. Non-destructive X-ray analytical methods were applied in order to obtain different kinds of information from the same samples or particles. In order to identify the pollution sources, their magnitude and fate, complementary analyses were carried out. Heterogeneous particulate samples were analyzed from a large geographical territory and a 4-year time period. Individual particles were analyzed only from the “hot” samples that showed elevated concentrations of heavy metals. Particles that were classified as anthropogenic were finally analyzed to identify trace concentrations and chemical states of heavy metals. 相似文献
32.
The total syntheses of the epoxy cyclic hemiacetal structures 8 and 9, which are isomeric with the structure 6 proposed for the phomactin known as Sch 49028 isolated from the marine fungus Phoma sp. are described. Neither of these structures showed spectroscopic data consistent with those reported for the purported natural product, adding credibility to the proposal that the structure Sch 49028 does not exist in nature and that its NMR spectroscopic data should have been assigned as phomactin A (1). 相似文献
33.
Gerald A. Miller Ned D. Heindel John A. Minatelli 《Journal of heterocyclic chemistry》1981,18(6):1253-1254
3-Aralkylidene-5-arylthiophen-2-(3H)ones can be prepared in two steps from 4-aryl-4-oxobutanoic acids through the intermediacy of butenolides and thiophenones generated by the sequential action of acetic anhydride, sodium hydrosulfide and aromatic aldehydes. 相似文献
34.
Gerald Rosen 《International Journal of Theoretical Physics》1985,24(12):1191-1195
Duality invariance of the Dirac-Schwinger charge-symmetric theory for electromagnetism leads one to consider the complex-valued amplitudes
1 and
2 for the separation between the magnetic monopole and quarks in the logarithmic charge plane. It is observed that the orthogonality relation on the latter amplitudes, Re(
1
*
2)=0, is equivalent to the equation (ln 9
–1)(ln 2)=(1/2)
2, which is indeed satisfied by the experimental value fora to within 0.027%. In addition to fixing the unit of electric charge at a primary physical value, the orientation of
1,
2 may also prescribe the Cabibbo angle to have the theoretical value 12.4438. 相似文献
35.
Zusammenfassung Die früher beschriebene Apparatur zur Bestimmung der primären Aminogruppe wurde verbessert. Auch die Handhabung wurde vereinfacht. Die einzelnen Teile der Apparatur (Desaminierungsteil, Absorber) können nun unabhängig voneinander ausgewaschen und luftfrei gemacht werden. Die Absorber sind für etwa 30 bis 50 Analysen benützbar, bevor sie erneuert werden müssen.
Der Firma P. Haack, Wien danken wir für das besondere Entgegen-Kommen bei der Entwicklung der Apparatur. 相似文献
Summary The apparatus previously described for the determination of primary amino groups has been improved. Also the manipulation is simplified. The individual segments of the apparatus (deamination part, absorber) can now be washed out independently of each other, and rendered free of air. The absorbers may be used for around 30 to 50 analyses before they must be renewed.
Der Firma P. Haack, Wien danken wir für das besondere Entgegen-Kommen bei der Entwicklung der Apparatur. 相似文献
36.
Giovanna Marini-Bettòlo Soumya P. Sahoo Gerald A. Poulton Thomas Y.R. Tsai Karel Wiesner 《Tetrahedron》1980,36(6):719-721
Some years ago an empirical rule, which allows the prediction of product stereochemistry in cis-photocycloaddition reactions of α,β-unsaturated ketones and olefins was tentatively proposed. Several additional examples, both selected from the literature and synthesized in our laboratory, seem to strengthen the validity of the rule. 相似文献
37.
Gerald Kainz und Franz Scheidl 《Fresenius' Journal of Analytical Chemistry》1964,202(4):251-258
Zusammenfassung In der vorliegenden Arbeit wurde untersucht, wie man die vergaste Probe am besten durch die Verbrennungszone führt, damit man eine vollständige Vermischung mit Sauerstoff erhält; denn bei hohen Temperaturen ist nicht so sehr die Umsatzgeschwindigkeit der Probe mit Sauerstoff bestimmend, sondern die Mischungsgeschwindigkeit mit Sauerstoff. Es wurden zwei Möglichkeiten untersucht. Bei der schnellen Vergasung im geraden Rohr ergab sich, daß sich dabei ein Substanzpfropf bildet, der durch Sauerstoff (im Wege der Diffusion) durchdrungen werden muß. Eine quantitative Oxydation ist nur dann möglich, wenn die Einwaage auf den Durchmesser des Verbrennungsrohres abgestimmt ist. Bei Mikroeinwaagen (3 mg) muß der Durchmesser des Verbrennungsrohres mindestens 20 mm betragen.Eine wesentlich intensivere Vermischung der Substanzdämpfe mit Sauerstoff wird bei der Verbrennung in der Flamme erreicht, die auf Wickbold bzw. Radmacher zurückgeht. Hierbei wird die Probe in einem engen Rohr unter Durchleiten von Sauerstoff oder Stickstoff vergast und durch eine enge Düse in die heiße Verbrennungszone eingeblasen. An der Düse bildet sich eine Flamme, in die Sauerstoff intensiv eindiffundiert. Eine einfache Apparatur, die eine schnelle, bei Mikroeinwaagen von der Geschicklichkeit des Analytikers unabhängige Vergasung und Verbrennung zuläßt, wird beschrieben.
Summary In this paper the problem is investigated how to pass the vaporised sample through the combustion zone in order to attain a complete mixture with oxygen; at high temperatures the completeness of combustion depends not so much on the rate of reaction with oxygen than on the rate of mixing with oxygen. Two experimental procedures have been investigated. High speed vaporisation in straight tubes leads to a plugshaped concentration of the sample, which must be penetrated by oxygen (diffusion). Using this procedure, a quantitative oxidation is only possible, if the sample weight is in a proper relation to the diameter of the tube. In microanalysis (3 mg of sample) the diameter of the combustion tube must be 20 mm or more.A much more intensive mixing of the vaporised sample with oxygen is attained by the combustion in the flame proposed by Wickbold and Radmacher. The vaporised sample is blown out of a small tube through a narrow nozzle into the heated combustion zone. On the nozzle a flame is formed, in which oxygen is diffusing intensively. A simple apparatus is described, which permits a rapid vaporisation and quantitative oxidation. Analysing micro samples the vaporisation was found to be independent of the skill of the analyst.相似文献
38.
Prof. Gerald B. Porter 《Theoretical chemistry accounts》1972,24(2-3):265-270
Analysis of the transient and steady-state kinetics of reversible energy transfer shows that while the interpretation of lifetime measurements is difficult unless the donor and acceptor lifetimes are appreciably different, quantum yield measurements are relatively easy to interpret.
Dedicated to the memory of Professor K. H. Hansen. 相似文献
Zusammenfassung Die Analyse der Kinetik der Übergangszustände und der stationären Zustände der reversiblen Energieübertragung zeigt, daß im Gegensatz zu einer schwierigen Interpretation der Messungen der Lebensdauer — es sei denn die Lebensdauer von Donor und Acceptor sind wesentlich voneinander verschieden — die Messungen der Quantumausbeute verhältnismäßig einfach zu interpretieren sind.
Résumé L'analyse de la cinétique de l'état transitoire et de l'état stationnaire du transfert réversible d'énergie montre que, si l'interprétation des mesures de durée de vie est difficile, à moins queles durées de vie du donneur et de l'accepteur soient très différentes, il est par contre relativement facile d'interpréter les mesures de rendement quantique.
Dedicated to the memory of Professor K. H. Hansen. 相似文献
39.
Fifteen of twenty-four silver(I) carboxylates examined give useful electron impact mass spectra. The compounds vaporize at moderate temperatures, apparently mainly as dimer with traces of higher oligomer in only a few cases. The molecular ion for the dimer is generally weak or absent, with the most abundant silver containing ion being [Ag2(O2CR)]+ in most cases. Metastable defocusing and deuterium labeling experiments on silver acetate have established some of the fragmentation pathways. The reported loss of carbon dioxide from perfluorocarboxylates to give intense peaks for organosilver ions was not observed in this study. Attempts to obtain spectra on the silver salts of organic materials other than carboxylic acids were successful in several cases. Silver trifluoromethanesulfonate, although much less volatile, gives a spectrum and fragmentation very much like the carboxylates, whereas silver trifluoromethanethiolate gives a complex spectrum which suggests tetramer as a major gas phase species. Of three compounds examined which have silver to nitrogen bonding only silver(II) phthalocyanine is sufficiently volatile to give a spectrum without decomposition. The field desorption spectra of the four compounds examined all show the ions AgnXn ? 1 for X=acetate (n=1 ? 6), X=p-chlorobenzoate (n=1 ? 4), X=methanesulfonate (n=1 ? 7) and X=p-toluenesulfonate (n=1 ? 5). 相似文献
40.
-A spectrophotometric method has been developed which is applicable to the determination of extremely small quantities of osmium. Osmium is oxidised to the octovalent state, then added to an acidic aqueous solution containing 1:5-diphenylcarbohydrazide (DPC). After heating the aqueous solution to 65°, the osmium-DPC complex is extracted with chloroform. A molar absorbancy index of about 150,000 is obtained. From 7 to 25 μg of osmium can be determined with a coefficient of variation of 6%. It was established that FeIII, CuII, RuIII and AuIII seriously interfere in the determination of osmium by this method, while CrVI, NiII, MoVI, IrIII and chloride interfere only when present in relatively high concentrations. 相似文献