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91.
Schuquel IT Pontes RM Freitas MP Rittner R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,81(1):135-139
The infrared spectra of 3-X-2-methylpropenes (X = Cl, Br, I, NMe(2), NEt(2), OH, OMe, OEt, SH, SMe and SEt) have been recorded at room temperature in CCl(4) solution. The C=C stretching mode was analyzed and compared to theoretically calculated data to give insight about the conformational isomerism of these compounds. A combination band systematically appears in all spectra (except for amines); the remaining ν(C=C) band and the corresponding intensities were used to obtain the conformer populations. For second-period atoms bonded to C-3, two or more conformers are observed in CCl(4) solution, but when substitution by heavier atoms takes place, only one conformer is observed under the tested conditions, i.e., the gauche form with respect to the C=C-C-X dihedral angle. Therefore, steric hindrance between X and =CH(2) in the s-cis form is strongly dependent on the heteroatom size, while the effect of the alkyl chain bonded to the heteroatom seems to be of secondary importance. 相似文献
92.
This work proposes two simple dynamic methods that provide an accurate method for measurement of diffusion coefficients in
building materials. Experimental measurements of moisture diffusion coefficients covered three commonly used building materials
and they were carried out for a range of the relevant parameters, as temperature and relative humidity. The diffusion coefficients
obtained by the two dynamic methods show a deviation comparatively to the steady-sate cup method; however, this variance is
in accordance with the results presented in literature. 相似文献
93.
Jamile Silva da Costa Jofre Jacob da Silva Freitas William N. Setzer Joyce Kelly R. da Silva Jos Guilherme S. Maia Pablo Luis B. Figueiredo 《Molecules (Basel, Switzerland)》2022,27(24)
Myrcia sylvatica (G. Mey) DC. is known as “insulin plant” because local communities use the infusions of various organs empirically to treat diabetes. The leaves of seven specimens of Myrcia sylvatica (Msy-01 to Msy-07) were collected in the Brazilian Amazon. Furthermore, the essential oils were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry, and their chemical compositions were submitted to multivariate analysis (Principal Component Analysis and Hierarchical Cluster Analysis). The multivariate analysis displayed the formation of four chemical profiles (chemotypes), described for the first time as follows: chemotype I (specimen Msy-01) was characterized by germacrene B (24.5%), γ-elemene (12.5%), and β-caryophyllene (10.0%); chemotype II (specimens Msy-03, -06 and -07) by spathulenol (11.1–16.0%), germacrene B (7.8–20.7%), and γ-elemene (2.9–7.6%); chemotype III (Msy-04 and -05) by spathulenol (9.8–10.1%), β-caryophyllene (2.5–10.1%), and δ-cadinene (4.8-5.6%); and chemotype IV, (Msy-02) by spathulenol (13.4%), caryophyllene oxide (15.0%), and α-cadinol (8.9%). There is a chemical variability in the essential oils of Myrcia sylvatica occurring in the Amazon region. 相似文献
94.
Ana Fernandes Sara Simes Isabel M. P. L. V. O. Ferreira Maria Joo Alegria Nuno Mateus Anabela Raymundo Victor de Freitas 《Molecules (Basel, Switzerland)》2023,28(1)
This work explores the potential of Rocha do Oeste pear pomace to be used as a sustainable and healthy food ingredient. Moreover, the enrichment with yeast protein extract (YPE) may be useful to design innovative food products. The main goals of this study were to assess pear pomace concerning: (i) chemical composition and antioxidant capacity; (ii) rheology, texture, and microstructure characterization (alone or enriched with YPE), before and after heating. The results showed that pear pomace was a rich source of dietary fibers (74.5% DW), with phenolic compounds (3.9 mg chlorogenic acid equivalents/g dry weight), also presenting antiradical activity (3.90 μmol Trolox equivalents/g DW). Pear pomace showed a shear thinning behavior and a typical soft-gel behavior, which was not affected by YPE enrichment, thus suggesting that YPE did not affect pear pomace technological properties. Thermal treatment also did not alter pear pomace rheological properties. YPE addition induced a decrease in the apparent viscosity and a destabilizing effect, compared to the samples that were subjected to thermal processing. These results highlight the importance of pear pomace and the use of YPE for protein enrichment, opening new opportunities for their exploitation. 相似文献
95.
Eliane Przytyk Jung Beatriz Pereira de Freitas Claudete Norie Kunigami Davyson de Lima Moreira Natlia Guimares de Figueiredo Leilson de Oliveira Ribeiro Ricardo Felipe Alves Moreira 《Molecules (Basel, Switzerland)》2022,27(17)
This study aimed to evaluate Bauhinia forficata infusions prepared using samples available in Rio de Janeiro, Brazil. As such, infusions at 5% (w/v) of different brands and batches commercialized in the city (CS1, CS2, CS3, and CS4) and samples of plant material botanically identified (BS) were evaluated to determine their total phenolic and flavonoid contents (TPC and TFC), antioxidant capacity (ABTS•+, DPPH•, and FRAP assays), phytochemical profile, volatile compounds, and inhibitory effects against the α-amylase enzyme. The results showed that infusions prepared using BS samples had lower TPC, TFC and antioxidant potential than the commercial samples (p < 0.05). The batch averages presented high standard deviations mainly for the commercial samples, corroborating sample heterogeneity. Sample volatile fractions were mainly composed of terpenes (40 compounds identified). In the non-volatile fraction, 20 compounds were identified, with emphasis on the CS3 sample, which comprised most of the compounds, mainly flavonoid derivatives. PCA analysis demonstrated more chemical diversity in non-volatile than volatile compounds. The samples also inhibited the α-amylase enzyme (IC50 value: 0.235–0.801 mg RE/mL). Despite the differences observed in this work, B. forficata is recognized as a source of bioactive compounds that can increase the intake of antioxidant compounds by the population. 相似文献
96.
97.
S. M. Almeida M. C. Freitas C. A. Pio 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):161-165
A Gent stacked filter unit sampler was used to collect air particulate matter (APM) in separate coarse (PM2.5–10) and fine (PM2.5) size fractions, at a sub-urban site in Lisbon, Portugal. The sampling was done during the year 2001 and two daily samples
were taken per week. The filters were analyzed for particulate mass by instrumental neutron activation analysis (INAA). The
chemical analysis of APM levels and the study of the atmospheric dynamics by back-trajectories showed that most of the PM2.5 and PM2.5–10 peaks events were associated with air masses transport from the Saharan desert. High mineral load in ambient particulate
matter levels were registered during the Saharan dust outbreaks. The accuracy of INAA to measure Fe, Sc and Sm was evaluated
by NIST filter standards, revealing results with an agreement of ± 10%. This method constituted an important tool to identify
these events. 相似文献
98.
A. M. G. Pacheco M. C. Freitas M. S. Baptista M. T. S. D. Vasconcelos J. P. Cabral 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):135-141
This study deals with the influence of the exposure conditions on biological uptake, by looking into concentrations of Ni
and V in lichen thalli and tree bark after continuous and discontinuous field trials at littoral sites impacted by anthropogenic
emissions. Biomonitors were assessed by k
0-INAA and AAS. Correlations at Sines are more apparent than at Viana or Lisboa. When data from all sites are pooled, V shows
correlations for practically every situation while Ni shows none, which may indicate a dissimilar uptake mechanism for each
element. At Sines, V/Ni ratios reach values that comply with emissions from oil-related industries. 相似文献
99.
M. Corti V. DeGiorgio C. E. Swenberg S. L. Shapiro F. Wang H. Pant B. R. Jennings P. J. Ridler M. D. Duncan J. Reintjes T. J. Manuccia V. S. Letokhov A. Andreoni R. Cubeddu S. De Silvestri P. Laborta F. Docchio R. Ramponi C. A. Sacchi G. Bottiroli I. Freitas V. S. Antonov A. N. Shibanov 《Applied physics. B, Lasers and optics》1982,28(2-3):240-245
100.
We have measured the Raman scattering intensities of the E1 (TO) polariton mode in ZnO, a wurtzite type crystal, at room and liquid nitrogen temperatures. These results reveal a novel behavior in contrast to that observed for ZnSe. These results confirm earlier theoretical considerations. 相似文献