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11.
12.
Biofilms are complex microbial communities that are resistant to attack by bacteriophages and to removal by drugs and chemicals. Here we use atomic force microscopy (AFM) to image the attack on Escherichia coli biofilms by Bdellovibrio bacteriovorus 109J. Bdellovibrio is a small, predatory bacterium that invades and devours other Gram-negative bacteria. We demonstrate that under dilute nutrient conditions, bdellovibrios can prevent the formation of simple bacterial biofilms and destroy established biofilms; under richer conditions the prey bacteria persist and are not eradicated, but may be shifted toward solution populations. Using AFM we explore these bacterial interactions with more detail and accuracy than available by more traditional staining assays or optical microscopy. AFM also allows us to investigate the nanoscale morphological changes of the predator, especially those related to motility. This demonstration of Bdellovibrio's successful predation in a biofilm inspires us to consider ways that it might be used productively for industrial, medical, agricultural, and biodefensive purposes. 相似文献
13.
Zdzisław Wawrzak Paweł Grochulski Zdzisław Gałdecki William L. Duax Phyllis D. Strong D. N. Kirk 《Journal of chemical crystallography》1991,21(5):649-652
The title compound crystallizes in space groupP212121 with lattice constantsa=16.253(3),b=17.107(3), andc=8.486(2) Å. The A ring has 1,2-half-chair conformation. The calculated steric energy of a 6-methyl-17-ester progesterone molecule is lower by about 4 kJ/mol for the normal A-ring conformation. The progesterone side chain has typical conformation for 17-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is –24.9(4)°. 相似文献
14.
Zdzisław Gałdecki Paweł Grochulski Zdzisław Wawrzak William L. Duax Phyllis D. Strong 《Journal of chemical crystallography》1989,19(3):561-568
The crystal and molecular structure of 3,12-dihydroxy-2-morpholino-5-pregnan-20-one, C25H41O4N, has been determined:M
r
=419.6,P21,a=13.5778(8),b=14.4340(8),c=5.8943(5) Å,=94.32(1)°,V
c
=1151.9(3) Å3,Z=2,D
x
=1.21 g cm–3,
(CuK) = 1.5418 Å, =5.6 cm–1,F(000)=460,R=0.039,R
w
=0.040 for 2421 unique observed reflections. All six-membered rings have chair conformations, and theD ring has a 13-envelope conformation. The progesterone side chain has an unusual conformation, and the C16-C17-C20-O20 torsion angle, which defines the conformation, is –152.6(3)°. The unusual conformation seems to be forced by the intramolecular hydrogen bond between the hydroxyl group at C12 and the O20 atom from the side-chain. 相似文献
15.
Noworolski SM Tien PC Merriman R Vigneron DB Qayyum A 《Magnetic resonance imaging》2009,27(4):570-576
Purpose
To develop a post-processing, respiratory-motion correction algorithm for magnetic resonance spectroscopy (MRS) of the liver and to determine the incidence and impact of respiratory motion in liver MRS.Materials and Methods
One hundred thirty-two subjects (27 healthy, 31 with nonalcoholic fatty liver disease and 74 HIV-infected with or without hepatitis C) were scanned with free breathing MRS at 1.5 T. Two spectral time series were acquired on an 8-ml single voxel using TR/TE=2500 ms/30 ms and (1) water suppression, 128 acquisitions, and (2) no water suppression, 8 acquisitions. Individual spectra were phased and frequency aligned to correct for intrahepatic motion. Next, water peaks more than 50% different from the median water peak area were identified and removed, and remaining spectra averaged to correct for presumed extrahepatic motion. Total CH2+CH3 lipids to unsuppressed water ratios were compared before and after corrections.Results
Intrahepatic-motion correction increased the signal to noise ratio (S/N) in all cases (median=11-fold). Presumed extrahepatic motion was present in 41% (54/132) of the subjects. Its correction altered the lipids/water magnitude (magnitude change: median=2.6%, maximum=290%, and was >5% in 25% of these subjects). The incidence and effect of respiratory motion on lipids/water magnitude were similar among the three groups.Conclusion
Respiratory-motion correction of free breathing liver MRS greatly increased the S/N and, in a significant number of subjects, changed the lipids/water ratios, relevant for monitoring subjects. 相似文献16.
Positively and negatively charged ionic modifications to cellulose assessed as cotton-based protease-lowering and hemostatic wound agents 总被引:1,自引:0,他引:1
J. V. Edwards Phyllis Howley Nicolette Prevost Brian Condon Judy Arnold Robert Diegelmann 《Cellulose (London, England)》2009,16(5):911-921
Recent developments in cellulose wound dressings targeted to different stages of wound healing have been based on structural
and charge modifications that function to modulate events in the complex inflammatory and hemostatic phases of wound healing.
Hemostasis and inflammation comprise two overlapping but distinct phases of wound healing wherein different dressing material
properties are required to bring pathological events under control when they present as a result of trauma or chronic wounds.
Thus, we have designed cellulose wound dressings with properties that function through modified fiber surface properties to
lower protease levels in the chronic wound and promote clotting in hemorrhaging wounds. With this in mind three finishing
chemistries utilizing traditional pad-dry-cure approaches were explored for their potential to confer charged properties to
cotton dressings. Cellulose dressings designed to remove cationic serine proteases from highly exudative chronic wounds were
created to present negatively charged fibers as an ion exchange mechanism of protease-lowering. Phosphorylated cotton and
polycarboxylic acid crosslinked cotton were prepared to examine their ability to remove human neutrophil elastase (HNE) from
surrogate wound fluid. A cellulose phosphorylation reaction utilizing sodium hexametaphosphate: urea was explored to optimize
cellulose phosphorylation as a function of HNE sequestration efficacy. Acid catalyzed cross linking of cellulose with butane-tetracarboxylic
acid also resulted in a negatively charged dressing that removed HNE from solution more effectively than phosphorylated cellulose.
Collagenase sequestration was also assessed with phosphorylated cellulose and polycarboxylic acid cross linked cellulose derivatives.
Butanetetracarboxylic acid and phosphorylated cellulose functioned to remove collagenase from solution most effectively. Cellulose
dressings designed to accelerate thrombosis and aggregation of blood platelets were prepared with a view to examining derivatized
cotton fibers bearing a net positive charge to promote hemostasis. Cellulose and chitosan dressings bearing an aminoglucan
functionality were created by grafting chitosan on cotton and preparing aminized cotton. The preparation of chitosan-grafted
cotton dressings was completed with a citric acid grafting onto cellulose. Aminized cotton was functionalized as an ethylamino-ether
cellulose derivative. The chitosan-grafted and aminized cotton demonstrated a dose response gelling of citrated sheep blood. 相似文献
17.
Varughese T Riosa N Higginbotham S Arnold AE Coley PD Kursar TA Gerwick WH Cubilla Rios L 《Tetrahedron letters》2012,53(13):1624-1626
Among thirty four endophytic fungal strains screened for in vitro antagonism, the endophytic fungus Cordyceps dipterigena was found to strongly inhibit mycelial growth of the plant pathogenic fungus Gibberella fujikuroi. Two new depsidone metabolites, cordycepsidone A (1) and cordycepsidone B (2), were isolated from the PDA culture extract of C. dipterigena and identified as being responsible for the antifungal activity. Elucidation of their chemical structures was carried out using 1D and 2D NMR spectroscopy in combination with IR and MS spectroscopic data. Cordycepsidone A displayed strong and dose-dependent antifungal activity against the plant pathogenic fungus Gibberella fujikuroi. The isolates were inactive in bioassays for malaria (Plasmodium falciparum), leishmaniasis (Leishmania donovani), Chagas's disease (Trypanosoma cruzi), and cytotoxicity at 10 μg/mL. The compounds were also found to be inactive against several bacterial strains at 50 μg/mL. 相似文献
18.
W. E. Garner C. A. Waters H. Lüers C. W. G. Hetterschy Aristides Kanitz F. Liebert A. Uhl W. Kestranek J. M. Kolthoff B. D. Hartong J. Pinkhof E. Biilmann A. Klit F. Haber Z. Klemensiewicz W. S. Hughes A. L. v. Steiger W. E. L. Brown Phyllis M. T. Kerridge Th. Arnd W. Siemers K. H. Goode W. D. Treadwell J. W. Williams Th. A. Whitenack U. Ehrhardt und E. Linde 《Fresenius' Journal of Analytical Chemistry》1930,80(5-6):203-213
Ohne Zusammenfassung 相似文献
19.
Katherine Verdolini David G. Druker Phyllis M. Palmer Hani Samawi 《Journal of voice》1998,12(3):315-327
The primary question in this study was whether subjects with nodules and subjects with healthy larynges would produce “resonant voice” with a similar laryngeal configuration. A second question regarded whether the electroglottographic closed quotient (EGG CQ) could be used to noninvasively distinguish resonant from other voice types. Twelve adult singers and actors served as subjects, including 6 persons with healthy larynges and 6 persons with nodules. Performers were used as an attempt to maximize token validity and stability. Subjects produced repeated tokens of resonant, pressed, normal, and breathy voice during sustained vowels. Laryngeal adduction was directly estimated using blinded, ordinal, visual-perceptual ratings based on videoscopic views of the larynx. EGG CQs were further calculated based on separate trials. The perceptual ratings indicated that subjects in both groups produced resonant voice with a barely adducted or barely abducted laryngeal configuration that was distinct from configurations for pressed and breathy (but not normal) voice. Previous literature suggests that this configuration may be relevant in many cases of voice therapy (I). Average CQs distinguished resonant from pressed voice, but inconsistently distinguished resonant from breathy voice. Further CQs were reliably different across healthy subjects and subjects with nodules. Thus, the utility of this measure to noninvasively estimate resonant voice may be limited, particularly without ongoing subject-specific calibration procedures. 相似文献
20.
The gas-phase thermal isomerizations at 315 °C of cis,anti,cis-tricyclo[6.4.0.02,7]dodec-3-ene to trans-tricyclo[6.2.2.02,7]dodec-9-ene and to cis,endo-tricyclo[6.2.2.02,7]dodec-9-ene favor the former, the more geometrically strained product, by a ratio of 2.4:1. These products correspond to suprafacial inversion (si) and suprafacial retention (sr) stereochemical outcomes. The reaction stereochemistry shown by the 11-carbon homolog, cis,anti,cis-tricyclo[6.3.0.02,7]undec-3-ene, is strikingly different: the [1,3] carbon shift takes place to give only the ‘forbidden’ sr product. Two related bicyclic vinylcyclobutanes, 8-deuterio- and 8-exo-methylbicyclo[4.2.0]oct-2-enes, evidence contrasting reaction stereochemical predilections in [1,3] shifts, but the 12-carbon tricyclic system and the 8-exo-methyl bicyclic analog isomerize with the same si:sr ratio! These observations prompt fresh considerations of structural influences on conformational preferences available to the alkyl, allyl diradical reactive intermediates involved. 相似文献