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In-vitro-grown cells of Mucuna pruriens, immobilized in calcium-alginate gels, were able to transform the precursor L-tyrosine into L-dihydroxyphenylalanine (L-DOPA). After the immobilization in alginate the plant cells released 90% of the produced L-DOPA into the medium; supplementation of the medium with calcium inhibited both the transformation of L-tyrosine into L-DOPA and the release of L-DOPA into the medium. Continuous illumination of the beads had a slight beneficial effect on the synthesis of L-DOPA. A simple production medium for the transformation of L-tyrosine into L-DOPA was designed. This medium contained only sucrose and sodium chloride as osmotic stabilizers, a low concentration of calcium chloride for stabilization of the alginate beads, and L-tyrosine as the precursor. 相似文献
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Tjitske A. Oenema Harm Maarsingh Marieke Smit Geny M. M. Groothuis Herman Meurs Reinoud Gosens 《PloS one》2013,8(6)
Airway remodelling, including smooth muscle remodelling, is a primary cause of airflow limitation in asthma. Recent evidence links bronchoconstriction to airway remodelling in asthma. The mechanisms involved are poorly understood. A possible player is the multifunctional cytokine TGF-β, which plays an important role in airway remodelling. Guinea pig lung slices were used as an in vitro model to investigate mechanisms involved in bronchoconstriction-induced airway remodelling. To address this aim, mechanical effects of bronchoconstricting stimuli on contractile protein expression and TGF-β release were investigated. Lung slices were viable for at least 48 h. Both methacholine and TGF-β1 augmented the expression of contractile proteins (sm-α-actin, sm-myosin, calponin) after 48 h. Confocal fluorescence microscopy showed that increased sm-myosin expression was enhanced in the peripheral airways and the central airways. Mechanistic studies demonstrated that methacholine-induced bronchoconstriction mediated the release of biologically active TGF-β, which caused the increased contractile protein expression, as inhibition of actin polymerization (latrunculin A) or TGF-β receptor kinase (SB431542) prevented the methacholine effects, whereas other bronchoconstricting agents (histamine and KCl) mimicked the effects of methacholine. Collectively, bronchoconstriction promotes the release of TGF-β, which induces airway smooth muscle remodelling. This study shows that lung slices are a useful in vitro model to study mechanisms involved in airway remodelling. 相似文献
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Walter Harm 《Molecular & general genetics : MGG》1960,91(1):52-62
Summary The inactivation of phage T4 by nitrous acid (HNO2) is essentially an exponential function of time of treatment. HNO2-inactivated T4 is able to undergo multiplicity reactivation, and genetic markers may be rescued by live phage, however, the extent of both effects is appreciably less than after UV-inactivation. Also, the survival of phenotypic function of the cistronsr II-A andr II-B is lower with HNO2-treatment than with a UV-irradiation of a corresponding number of hits.The reduced effects are quantitatively accounted for by the assumption of lethal hits blocking early steps of infection. These early-step damages amount to approximately 1/6 of the total hit number; it is still unknown whether they occur in DNA or in protein. Some indication for the occurrence in protein comes from the result that the host-killing efficiency of HNO2-inactivated phage is reduced at a similar rate as these early-step damages occur. However, at least 5/6 of the lethal hits are due to chemical changes within the DNA, as can be calculated from the results of multiplicity reactivation, marker rescue, and phenotypic survival of therII-cistrons.
Mit 6 Textabbildungen 相似文献
Mit 6 Textabbildungen 相似文献
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Hageman J van Waarde MA Zylicz A Walerych D Kampinga HH 《The Biochemical journal》2011,435(1):127-142
Humans contain many HSP (heat-shock protein) 70/HSPA- and HSP40/DNAJ-encoding genes and most of the corresponding proteins are localized in the cytosol. To test for possible functional differences and/or substrate specificity, we assessed the effect of overexpression of each of these HSPs on refolding of heat-denatured luciferase and on the suppression of aggregation of a non-foldable polyQ (polyglutamine)-expanded Huntingtin fragment. Overexpressed chaperones that suppressed polyQ aggregation were found not to be able to stimulate luciferase refolding. Inversely, chaperones that supported luciferase refolding were poor suppressors of polyQ aggregation. This was not related to client specificity itself, as the polyQ aggregation inhibitors often also suppressed heat-induced aggregation of luciferase. Surprisingly, the exclusively heat-inducible HSPA6 lacks both luciferase refolding and polyQ aggregation-suppressing activities. Furthermore, whereas overexpression of HSPA1A protected cells from heat-induced cell death, overexpression of HSPA6 did not. Inversely, siRNA (small interfering RNA)-mediated blocking of HSPA6 did not impair the development of heat-induced thermotolerance. Yet, HSPA6 has a functional substrate-binding domain and possesses intrinsic ATPase activity that is as high as that of the canonical HSPA1A when stimulated by J-proteins. In vitro data suggest that this may be relevant to substrate specificity, as purified HSPA6 could not chaperone heat-unfolded luciferase but was able to assist in reactivation of heat-unfolded p53. So, even within the highly sequence-conserved HSPA family, functional differentiation is larger than expected, with HSPA6 being an extreme example that may have evolved to maintain specific critical functions under conditions of severe stress. 相似文献
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Jean Yves Le Reste Patrice Nabbe Charles Rivet Charilaos Lygidakis Christa Doerr Slawomir Czachowski Heidrun Lingner Stella Argyriadou Djurdjica Lazic Radost Assenova Melida Hasaganic Miquel Angel Munoz Hans Thulesius Bernard Le Floch Jeremy Derriennic Agnieska Sowinska Harm Van Marwijk Claire Lietard Paul Van Royen 《PloS one》2015,10(1)