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141.
Rubinsztein DC DiFiglia M Heintz N Nixon RA Qin ZH Ravikumar B Stefanis L Tolkovsky A 《Autophagy》2005,1(1):11-22
Increased numbers of autophagosomes/autophagic vacuoles are seen in a variety of physiological and pathological states in the nervous system. In many cases, it is unclear if this phenomenon is the result of increased autophagic activity or decreased autophagosome-lysosome fusion. The functional significance of autophagy and its relationship to cell death in the nervous system is also poorly understood. In this review, we have considered these issues in the context of acute neuronal injury and a range of chronic neurodegenerative conditions, including the Lurcher mouse, Alzheimer's, Parkinson's, Huntington's and prion diseases. While many issues remain unresolved, these conditions raise the possibility that autophagy can have either deleterious or protective effects depending on the specific situation and stage in the pathological process. 相似文献
142.
Ambient temperature perception in plants 总被引:3,自引:0,他引:3
Since plants are sessile they must be able to sense and rapidly respond to changes in ambient temperature. Key aspects of plant development, including the transition to flowering and the circadian clock, have important inputs from ambient temperature. In the model system Arabidopsis thaliana, molecular candidates for mediating these roles have recently been uncovered, which will be critical for obtaining an understanding of the mechanisms involved. 相似文献
143.
The hydrogen bonding interactions between the Klenow fragment of Escherichia coli DNA polymerase I with the proofreading exonuclease inactivated (KF(-)) and the minor groove of DNA were examined with modified oligodeoxynucleotides in which 3-deazaguanine (3DG) replaced guanine. This substitution would prevent a hydrogen bond from forming between the polymerase and that one site on the DNA. If the hydrogen bonding interaction were important, then we should observe a decrease in the rate of reaction. The steady-state and pre-steady-state kinetics of DNA replication were measured with 10 different oligodeoxynucleotide duplexes in which 3DG was placed at different positions. The largest decrease in the rate of replication was observed when 3DG replaced guanine at the 3'-terminus of the primer. The effect of this substitution on mispair extension and formation was then probed. The G to 3DG substitution at the primer terminus decreased the k(pol) for the extension past G/C, G/A, and G/G base pairs but not the G/T base pair. The G to 3DG substitution at the primer terminus also decreased the formation of correct base pairs as well as incorrect base pairs. However, in all but two mispairs, the effect on correct base pairs was much greater than that of mispairs. These results indicate that the hydrogen bond between Arg668 and the minor groove of the primer terminus is important in the fidelity of both formation and extension of mispairs. These experiments support a mechanism in which Arg668 forms a hydrogen bonding fork between the minor groove of the primer terminus and the ring oxygen of the deoxyribose moiety of the incoming dNTP to align the 3'-hydroxyl group with the alpha-phosphate of the dNTP. This is one mechanism by which the polymerase can use the geometry of the base pairs to modulate the rate of formation and extension of mispairs. 相似文献
144.
Tiran J Ben-Oved N Elan E Slovik Y Leiberman A Weisel-Eichler A Kaplan DM 《Journal of biomechanical engineering》2005,127(6):994-997
Rhinomanometry is a method for measuring nasal resistance for the purpose of providing an objective evaluation of nasal patency. Posterior rhinomanometry is accomplished without the use of a mask, thus allowing the patient to breathe naturally. Here, we report on the improvements we have made to the existing posterior rhinomanometry system. In this system, nasal airflow is measured indirectly by measuring the pressure differential across a small mesh window in the body plethysmograph. We have calibrated this measurement and developed software that automatically provides the correct values for all airflow rates. Also, we have developed software that automatically corrects for the phase shift caused by the plethysmograph structure. These refinements should provide more accurate values for nasal resistance. 相似文献
145.
146.
Transient States of Adenylate Cyclase in Brain Membranes 总被引:3,自引:1,他引:2
Basal activity of adenylate cyclase from the amygdala of sheep brain and the neostriatum of turkey brain decays in two phases at 37 degrees C. The first phase is rapid (t1/2 = 2.3 +/- 0.3 min) and results in the loss of 60-70% of basal activity. The second phase is slow (t1/2 approximately 100 min) during which time the catalytic units denature irreversibly. The GTP analogue guanosine-5' (beta-gamma imino) triphosphate (p[NH]ppG) prevents the rapid decay by stabilizing the enzyme at its initial level of activity and also reactivates the enzyme to initial levels during or immediately following the early phase, indicating that denaturation of neither the guanylnucleotide units nor the catalytic units causes the rapid decline in basal activity. Activation by p[NH]ppG is rapid at 37 degrees C, but the binding of p[NH]ppG to the guanylnucleotide subunit also occurs at nonactivatory temperatures. This is determined by the protection of catalytic units from thermal or N-ethylmaleimide inactivation after extensive washing. Thus, at 25 degrees C all of the catalytic units can be stabilized by saturating p[NH]ppG concentrations. At 0 degree C, 35% of the catalytic units can be stabilized by saturating p[NH]ppG concentrations within 30 s. The half-saturation constant for the binding of p[NH]ppG at 0 degree C is identical to that derived in an assay at 37 degrees C, or after an incubation of the membranes for 10 min at 45 degrees C, when the process of thermal denaturation is 80% complete (K1/2 approximately 3 +/- 2 microM).(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
147.
Primary conidia of the entomopathogens Erynia (subgenus Neopandora) delphacis (1 isolate) and Erynia ( Neopandora) neoaphidis
(3 isolates) were stimulated to form germ-tubes with Tween 20 and with free, long-chain fatty acids, each incorporated into
Entomophthora complete medium (ECM). When combined with other basal media (three tested), these compounds did not stimulate
germ-tube formation. Triacylglycerols and vegetable oils, added to the same media, allowed almost complete resporulation in
the fungi. In both species, Tween 20 (0.1%) encouraged greater germ-tube production (41–69%) than the fatty acids (0.1%) (≤36%).
For E. delphacis, Tween 20 and the fatty acids differed significantly, but for E. neoaphidis the differences were almost always
insignificant. Myristic and oleic acids stimulated germ-tube formation in both species. Palmitic acid allowed almost complete
resporulation of the fungi, except for one isolate of E. neoaphidis that formed germ-tubes. Linoleic acid, tested only for
E. delphacis, was fungistatic to most conidia. Higher concentrations of the fatty acids (≤1%) did not increase germ-tube formation,
except 1% oleic acid which affected E. delphacis alone (>80% germination and germ-tubes). Linoleic acid, and sometimes also
myristic and oleic, were fungistatic and/or toxic, depending on their concentration and on medium composition. Addition of
fatty acids to ECM usually extended the lag period, and altered the morphology of the conidia and germ-tubes. These phenomena
were not observed with Tween 20. Colonies were formed by E. delphacis alone, stimulated by ECM supplemented with Tween 20
or fatty acids. The results are discussed with respect to biological and physiological aspects of germination, and with respect
to the mode of action of the fatty acids and the surfactant.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
148.
Mechanisms by which a Very-Low-Calorie Diet Reverses Hyperglycemia in a Rat Model of Type 2 Diabetes
149.
150.