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21.
Three new linear compounds of the type Co(3)(dpa)(4)X(2), where dpa is the anion of di(2-pyridyl)amine and X is NCS(-) (5), CN(-) (6), and N(CN)(2)(-) (7), have been prepared, and their structures and magnetic behavior have been studied. In all of them, including three different solvates of 5, the Co(3) chains are symmetrical with Co-Co distances of ca. 2.31-2.32 A. The appearance of four lines in the (1)H NMR spectra of the three compounds is also consistent with a symmetrical structure in solution. For all compounds, the magnetic behavior is quite similar with mu(eff) of ca. 1.9-2.0 micro(B) at temperatures between 1.8 and 200 K. As the temperature increases, the effective moments increase gradually, but since saturation is not reached, even at 400 K, the high-spin state cannot be assigned. 相似文献
22.
Traces of nitrogen can be determined in uranium by reductive fusion in vacuum or in a current of helium. The two methods gave similar results, and these were confirmed by the Kjeldahl method. The excellent agreement between the values obtained made it possible to establish a reference standard. 相似文献
23.
The dissociation constants Kd of triethylammonium picrate have been determined from conductimetric measurements in nitrobenzene (NB) and in ortho-dichlorobenzene (ODCB) with and without pyridines being used as ligands. In the absence of any ligand, the enhancement of the dissociation in NB as compared with that in ODCB cannot be explained solely by the increase of the dielectric constant, but shows the existence of specific interactions of the former solvent with the ions. The results obtained in the presence of ligands are consistent with the formation of a 1:1 cation-pyridine hydrogen-bonded complex. The constantk 1 + for the formation of theis complex has been determined for six substituted pyridines in both solvents. Logk 1 + varies linearly with the Hammett parameter σH of the substituent. The slope ρ of the Hammett relation is ?1.86 in NB and ?2.90 in ODCB. The difference can be ascribed to specific interactions between NB and the pyridines which become stronger when the pyridine is more basic. 相似文献
24.
Miyasaka H Nezu T Iwahori F Furukawa S Sugimoto K Clérac R Sugiura K Yamashita M 《Inorganic chemistry》2003,42(15):4501-4503
The heterometallic Mn(II)(4)Ni(II)(2) title compound has been synthesized and characterized by X-ray crystallography. The compound consists of a Ni-Mn-Ni linear moiety, [[Ni-(mu-NO)(3)](2)-Mn], linked by oximate bridges and three Mn(II) hfac terminal units attached by oximate oxygens in a di-mu-oxo fashion, forming a novel heterometallic cluster: Mn[Mn(hfac)(2)](3)[Ni(pao)(3)](2) (1). Magnetic measurements reveal the antiferromagnetic nature of the oximate pathway between Mn(II) and Ni(II) metal ions, which imposes an unusual high-spin ground state (S = 8) for 1. 相似文献
25.
Clémence Guillaume Jacques Le Calvé Iliana Dimicoli Michel Mons 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,32(1):157-165
The intensity distribution of benzene+-Arn cluster ions formed by laser ionization of neutral clusters has been investigated: two main intensity anomalies (magic numbers atn=20 and 45) have been observed in the 15–60 size range. The evaporation dynamics of these species in the 2–50 microsecond time window following ionization has been studied using the electrostatic mirror of a reflectron time-of-flight mass spectrometer as a kinetic energy analyser capable to distinguish parent and daughter ions. The magic numbers are interpreted in terms of size dependent evaporation behaviors: beyondn=20, a sudden decrease of the evaporation energy is observed; in then=45–47 size range, the magic number is accounted for by the specific dynamics of then=46 and 47 clusters, in particular the possible loss of two argon atoms forn=47 within the experimental time window. These results and their implications on the cluster structure are discussed in the light of the evaporative ensemble model and compared to the evaporation characteristics of similar species, in particular the neat rare gas clusters. 相似文献
26.
Yamaki SB Andrade AA Mendonça CR Oliveira ON Atvars TD 《Journal of colloid and interface science》2005,283(2):464-471
A morphological analysis is presented for Langmuir films of the diazo dyes Sudan 4 (S4), Sudan 3 (S3), and Sudan red (SR), using Brewster angle microscopy. Stable nonmonomolecular structures are formed at the air-water interface denoted as a plateau in the pressure-area isotherms. Monolayer domains are evident by the contrastless image even before the pressure onset, which grow in size until it reached a condensed monolayer. This behavior resembles that of Langmuir films from simple aromatic fatty acids. Films from all the azo dyes display similar features, according to the surface potential isotherms and in situ polarized UV/vis spectroscopy except for the larger area per molecule occupied by S4 and SR. This is attributed to the presence of CH(3) groups that cause steric hindrance modifying the organization of diazo dye molecules at the air-water interface. UV/vis polarized absorption spectroscopy showed preferential orientation of S4 and S3 on the water surface, while SR molecules lie isotropically. For these three diazo dyes, film absorption was negligible at very large areas per molecule, becoming nonzero only at a critical area coinciding with the onset of surface potential. The critical area is ascribed to the formation of a H-bonded network between water molecules and diazo dye headgroups. 相似文献
27.
Qin C Wang XL Li YG Wang EB Su ZM Xu L Clérac R 《Dalton transactions (Cambridge, England : 2003)》2005,(15):2609-2614
Two new three-dimensional nickel coordination polymers, [Ni3(BTC)2(4,4'-bpy)2(H2O)5].1.5H2O (1) and [Ni(PDB)(4,4'-bpy)].0.5H2O (2)(4,4'-bpy = bipyridine, BTC = 1,2,4-benzenetricarboxylate, PDB = pyridine-3,4-dicarboxylate), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, TGA, and single crystal X-ray diffraction. Both compounds contain 2D scaffolding motifs, and most interestingly adjacent scaffolds are connected by infinite helical chains into unique three-dimensional mesomeric networks. Moreover, temperature-dependent magnetic susceptibilities for the two compounds were studied, and ferromagnetic interactions through syn-anti carboxylate bridges between Ni sites have been observed. 相似文献
28.
Geciane Toniazzo Débora de Oliveira Cláudio Dariva Enrique Guillermo Oestreicher Octávio A. C. Antunes 《Applied biochemistry and biotechnology》2005,123(1-3):837-844
The main objective of this work was to investigate the biotransformations of (−)α-pinene, (−)β-pinene, and (+) limonene by
Aspergillus niger ATCC 9642. The culture conditions involved—concentration of cosolvent (EtOH), substrate applied, and sequential addition
of substrates—were investigated. Adaptation of the precultures with small amounts of substrate was also studied. The experiments
were performed in conical flasks with liquid cultures. This strain of A. niger was able to convert only (−)β-pinene into α-terpineol. An optimum conversion of (−)β-pinene into α-terpineol of about 4%
was obtained when the substrate was applied as a diluted solution in EtOH and sequential addition of substrate was used. 相似文献
29.
A new method is presented for spectrophotometric micro-determinations of cadmium by means of a triazine dye, called “Cadion”The method is a highly sensitive one, permitting the determination of 0.05 p.p.m. cadmium in the final solution, with satisfactory accuracy and reproducibility.The interference of the main foreign anions and cations is studied, and a way of eliminating the interfering ions is suggestedSome examples are given for the application of the proposed method 相似文献
30.
Zusammenfassung Nach den an Hand der Warburg-Technik durchgeführten Autoxydationsversuchen erweisen sich im Einklang mit früheren eigenen Untersuchungen p-Benzochinon, p-Benzohydrochinon sowie p-Benzochinhydron als Antioxydantien unterschiedlicher Wirkungsstärke und verschiedenartiger Wirkart.Chinon, das schwächste Antioxydans, betätigt sich als Retarder, Hydrochinon mit seiner markanten Verlängerung der Induktionsperiode stellt einen echten Inhibitor dar. Chinhydron sind beide Wirkungen als Retarder und Inhibitor zuzuordnen.Durch eingehende systematische Untersuchungen wird gezeigt, daß die Veränderungen von Chinon, Chinhydron und Hydrochinon während der Autoxydation von Äthyllinolat ohne Störung durch gebildete Hydro peroxyde im lipiden System als reduzierbarer bzw. oxydierbarer Anteil auf polarographischem Wege mit gut reproduzierbaren Ergebnissen und sehr befriedigender Empfindlichkeit bestimmbar sind.
Herrn Prof. Dr.-Ing.G. Gorbach zum 60. Geburtstag in glückwünschender Verbundenheit gewidmet. 相似文献
Summary According to the autoxidation experiments carried out by means of the Warburg technique,p-benzoquinone,p-benzohydroquinone, and alsop-benzoquinhydrone, in agreement with previous trials by the present writers, exhibit antioxidant actions of different degrees and kinds of action.Quinone, the weakest antioxidant, acts as retarder. Hydroquinone, with its distinct lengthening of the induction period is a real inhibitor. Quinhydrone can function either as retarder or inhibitor.Extensive systematic trials showed that the changes in quinone, quinhydrone and hydroquinone during the autoxidation of ethyl linolate can be determined polarographically in excellent reproducible fashion and with good sensitivity with no interference from the resulting hydroperoxides in the lipid system as reducible or oxidizable portion.
Résumé Les essais d'auto-oxydation effectués d'après la technique de Warburg se montrent en accord avec certaines expériences antérieures réalisées avec lap-benzoquinone, lap-benzohydroquinone ainsi qu'avec lap-benzoquinhydrone comme anti-oxydants agissant avec des actions plus ou moins fortes et suivant des processus différents.La quinone, l'anti-oxydant le plus faible, se comporte comme »retardateur«, l'hydroquinone, qui prolonge de manière très accentuée la période d'induction, se présente comme un véritable »inhibiteur«. La quinhydrone se comporte à la fois comme »retardateur« et comme »inhibiteur«.On montre par des recherches systématiques et approfondies que l'on peut doser les variétés de quinone, de quinhydrone et d'hydroquinone pendant l'auto-oxydation du linoléate d'éthyle, comme éléments »réducteurs« ou »oxydants«, par polarographie, avec de bons résultats reproductibles et une bonne sensibilité, sans interférence avec les hydroperoxydes formés dans le système lipide.
Herrn Prof. Dr.-Ing.G. Gorbach zum 60. Geburtstag in glückwünschender Verbundenheit gewidmet. 相似文献