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161.
162.
Preparation of 1,2-Diarylethylenediamines by Aminative Reductive Coupling of Aromatic Aldehydes with Low-Valent Titanium Reagents In a novel McMurry- Type one-pot reaction, aromatic aldehydes and secondary amines are poupled of give the N, N, N′, N′-tetraalkyl-1,2-diarylethylendiamines 1–22 (Table 3). To this end, a lithium dialkylamide is added to an aromatic aldehyde to give the adduct B which is then treated with 1 equiv. of TiC14 to yield a coloured suspension of a reagent synthetically equivalent to a iminium salt ( C/D in Scheme 4). After treatment with a low-valent Ti reagent which is prepared by reduction of TiC14 with either K or, preferably, Mg, the coupling products are isolated in 23 to 81% yield as a 1:1 mixture of the diastereoisomers (meso- and rac-form). These are separated either by chromatography or by crystallization and characterized. 相似文献
163.
Investigations carried out in order to determine traces of 25 elements in tungsten in the lower g/g range are reported on. Atomic absorption spectrometry and plasma atomic emission spectrometry as well as solution photometry and activation analysis were the main techniques used. 相似文献
164.
165.
Laser-induced breakdown spectroscopy has been used for quantitative measurement of trace elements, e.g. sulfur and chlorine,
in concrete. Chloride and sulfate ions have a large effect on the durability of concrete structures, and quantitative measurement
is important for condition assessment and quality assurance. Concrete is a highly heterogeneous material in composition and
grain-size distribution, i.e. the spatial distribution of elements. Calibration plots were determined by use of laboratory-made
reference samples consisting of pressings of cement powder, hydrated cement, cement mortar, and concrete, in which the heterogeneity
of the material is increasing because of the aggregates. Coarse aggregate and cement paste are distinguishable by the intensity
of the Ca spectral lines. More advanced evaluation is necessary to account for the effect of the fine aggregate. The three
series of reference samples enable systematic study of the effects of heterogeneity on spectral intensity, signal fluctuation,
uncertainty, and limits of detection. Spatially resolved measurements and many spectra enable statistical evaluation of the
data. The heterogeneity has an effect on measurement of the sulfur and chlorine content, because both occur mainly in the
cement matrix. Critical chloride concentrations are approximately 0.04% (m/m). The chlorine spectral line at 837.6 nm is evaluated. The natural sulfur content of concrete is approximately 0.1% (m/m). The spectral line at 921.3 nm is evaluated. One future application may be simultaneous determination of the amount of damaging
trace elements and the cement content of the concrete. 相似文献
166.
167.
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
168.
Reaction of 1,1-difluoroallene and tetrafluoroallene with a series of transition metal complex fragments yields the mononuclear allene complexes [CpMn(CO)(2)(allene)] (1), [(CO)(4)Fe(allene)] (2), [(Ph(3)P)(2)Pt(C(3)H(2)F(2))] (4), [Ir(PPh(3))(2)(C(3)H(2)F(2))(2)Cl] (5), and the dinuclear complexes [mu-eta(1)-eta(3)-C(3)H(2)F(2))Fe(2)(CO)(7)] (3), [Ir(PPh(3))(C(3)H(2)F(2))(2)Cl](2) (6), and [mu-eta(2)-eta(2)-C(3)H(2)F(2))(CpMo(CO)(2))(2)] (9), respectively. In attempts to synthesize cationic complexes of fluorinated allenes [CpFe(CO)(2)(C(CF(3))=CH(2))] (7a), [CpFe(CO)(2)(C(CF(3))=CF(2))] (7b) and [mu-I-(CpFe(CO)(2))(2)][B(C(6)H(3)-3,5-(CF(3))(2))(4)] were isolated. The spectroscopic and structural data of these complexes revealed that the 1,1-difluoroallene ligand is coordinated exclusively with the double bond containing the hydrogen-substituted carbon atom. 1,1-Difluoroallene and tetrafluoroallene proved to be powerful pi acceptor ligands. 相似文献
169.
170.
G. Matuschek J. Cyrys D. Lenoir A. Kettrup 《Journal of Thermal Analysis and Calorimetry》1993,40(2):533-535
The effect of oxydation of particulate carbon as a part of fly ash has been studied by mean of differential scanning calorimetry
(DSC) and simultaneous thermal analysis/mass spectrometry (TA/MS). The results from different carbon modifications added to
fly ash were discussed and compared to those of the pure samples.
Zusammenfassung Mittels DSC und Thermoanalyse/Massenspektrometrie wurde der Effekt der Oxidation von Kohlenstoff als Teil von Flugasche untersucht. Die durch Zusatz verschiedener Kohlenstoffarten zu Flugasche erhaltenen Ergebnisse wurden diskutiert und mit denen von reinen Proben verglichen.相似文献