全文获取类型
收费全文 | 236篇 |
免费 | 10篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 2篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 6篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有246条查询结果,搜索用时 15 毫秒
51.
52.
Solway J.; Fredberg J. J.; Ingram R. H. Jr; Pedersen O. F.; Drazen J. M. 《Journal of applied physiology》1987,62(5):2013-2025
We recognized similarities between isovolume pressure-flow curves of the lung and emitter-collector voltage-current characteristics of bipolar transistors, and used this analogy to model expiratory flow limitation in a two-generation branching network with parallel nonhomogeneity. In this model, each of two bronchi empty parenchymal compliances through a common trachea, and each branch includes resistances upstream and downstream of a flow-limiting site. Properties of each airway are specified independently, allowing simulation of differences between the tracheal and bronchial generations and between the parallel bronchial paths. Simulations of four types of parallel asymmetry were performed: unilateral peripheral bronchoconstriction; unilateral central bronchoconstriction; asymmetric redistribution of parenchymal compliance; and unilateral alteration of the bronchial area-transmural pressure characteristic. Our results indicate that multiple axial choke points can exist simultaneously in a symmetric lung when large airway opening-pleural pressure gradients exist; despite severe nonhomogeneity of regional lung emptying, flow interdependence among parallel branches tends to maintain a near normal configuration of the overall maximal expiratory flow-volume (MEFV) curve throughout a large fraction of the vital capacity; and sudden changes of slope of the MEFV curve ("knees" or "bumps") may reflect choking in one branch in a nonuniform lung, but need not be obvious even when severe heterogeneity of lung emptying exists. 相似文献
53.
Molecular evolution of rodent insulins 总被引:1,自引:0,他引:1
Several trees of amino acid sequences of rodent insulins were derived with
the maximum-parsimony procedure. Possible orthologous and paralogous
relationships were investigated. Except for a recent gene duplication in
the ancestor of rat and mouse, there are no strong arguments for other
paralogous relationships. Therefore, a tree in agreement with other
biological data is the most reasonable one. According to this tree, the
capacity to form zinc-binding hexamers was lost once in the ancestor of the
hystricomorph rodents, followed by moderately increased evolutionary rates
in the lineages to African porcupine and chinchilla but highly increased
rates in at least three independent lines to other taxa of this suborder:
guinea pig, cuis, and Octodontoidea (coypu and casiragua).
相似文献
54.
In studies of large-amplitude periodic flows at an airway bifurcation, we found an appreciable steady-state pressure difference between the terminal units. To elucidate the fluid dynamic origins of such steady-state pressure differences, we studied single asymmetric bifurcation models with various area ratios and branching angles. The daughter ducts were identical in size and were terminated into identical elastic loads. Sinusoidal flow oscillations were applied at the parent duct so that the upstream Reynolds number ranged from 30 to 77,000 and the Womersley parameter from 2 to 30. The steady-state component (time averaged) of the pressure measured at the terminal with the smaller branching angle was found to be consistently higher than that at the other terminal. This steady-state pressure difference scaled approximately as a fixed fraction of the parent duct dynamic head. Guided by the results of flow-visualization studies, we modeled such behavior based on the temporal and spatial differences of head loss between the two branches of the bifurcation. Our results suggest that interlobar heterogeneity of mean alveolar-pressure observed in excised canine lungs during high frequency oscillation (Allen et al., J. Appl. Physiol. 62: 223-228, 1987) arises solely from fluid dynamic origins: differential head loss due to asymmetry of central airway branching structure. 相似文献
55.
Jeffrey J Fredberg 《Journal of applied physiology》2007,102(4):1709-10; discussion 1710-1
56.
Viscoplasticity of respiratory tissues 总被引:2,自引:0,他引:2
Low-frequency mechanical behavior of various respiratory tissues shows certain similarities. In this study we test the hypothesis that rate-independent plastic processes along with rate-dependent viscoelastic processes are responsible. We considered oscillatory responses of several respiratory tissues measured over prescribed ranges of frequency (up to 6 Hz) and amplitude of forcing. These included the excised cat lung, the human chest wall in vivo, and two components of the chest wall: the excised dog rib cage and the excised rabbit abdominal viscera; some data were previously reported and some are new. We analyzed these data using the viscoplastic model of Hildebrandt (J. Appl. Physiol. 28: 365-372, 1970). It consists of three compartments: a plastoelastic compartment mechanically in parallel with a viscoelastic compartment, both in series with a lumped inertia. We fitted oscillatory data of the above respiratory tissues to the model by a least-squares technique. The fit was qualitatively consistent with the observations and exhibited moderately good to very good quantitative correspondence. As an independent verification of this approach, we obtained the stress relaxation after a step-volume change. Based on the oscillatory response of cat lungs, the calculated stress relaxation function was found to be generally consistent with corresponding observations. This study indicates that both plasticity and viscoelasticity appear to be important determinants of mechanical behavior of respiratory tissues at low frequencies and that inertial effects are negligible. 相似文献
57.
58.
Victor van der Meer Henk F van Stel Moira J Bakker Albert C Roldaan Willem JJ Assendelft Peter J Sterk Klaus F Rabe Jacob K Sont 《Respiratory research》2010,11(1):74
Background
Internet-based self-management has shown to improve asthma control and asthma related quality of life, but the improvements were only marginally clinically relevant for the group as a whole. We hypothesized that self-management guided by weekly monitoring of asthma control tailors pharmacological therapy to individual needs and improves asthma control for patients with partly controlled or uncontrolled asthma.Methods
In a 1-year randomised controlled trial involving 200 adults (18-50 years) with mild to moderate persistent asthma we evaluated the adherence with weekly monitoring and effect on asthma control and pharmacological treatment of a self-management algorithm based on the Asthma Control Questionnaire (ACQ). Participants were assigned either to the Internet group (n = 101) that monitored asthma control weekly with the ACQ on the Internet and adjusted treatment using a self-management algorithm supervised by an asthma nurse specialist or to the usual care group (UC) (n = 99). We analysed 3 subgroups: patients with well controlled (ACQ ≤ 0.75), partly controlled (0.75>ACQ ≤ 1.5) or uncontrolled (ACQ>1.5) asthma at baseline.Results
Overall monitoring adherence was 67% (95% CI, 60% to 74%). Improvements in ACQ score after 12 months were -0.14 (p = 0.23), -0.52 (p < 0.001) and -0.82 (p < 0.001) in the Internet group compared to usual care for patients with well, partly and uncontrolled asthma at baseline, respectively. Daily inhaled corticosteroid dose significantly increased in the Internet group compared to usual care in the first 3 months in patients with uncontrolled asthma (+278 μg, p = 0.001), but not in patients with well or partly controlled asthma. After one year there were no differences in daily inhaled corticosteroid use or long-acting β2-agonists between the Internet group and usual care.Conclusions
Weekly self-monitoring and subsequent treatment adjustment leads to improved asthma control in patients with partly and uncontrolled asthma at baseline and tailors asthma medication to individual patients'' needs.Trial registration
Current Controlled Trials ISRCTN79864465 相似文献59.
Background
The assembly and spatial organization of enzymes in naturally occurring multi-protein complexes is of paramount importance for the efficient degradation of complex polymers and biosynthesis of valuable products. The degradation of cellulose into fermentable sugars by Clostridium thermocellum is achieved by means of a multi-protein "cellulosome" complex. Assembled via dockerin-cohesin interactions, the cellulosome is associated with the cell surface during cellulose hydrolysis, forming ternary cellulose-enzyme-microbe complexes for enhanced activity and synergy. The assembly of recombinant cell surface displayed cellulosome-inspired complexes in surrogate microbes is highly desirable. The model organism Lactococcus lactis is of particular interest as it has been metabolically engineered to produce a variety of commodity chemicals including lactic acid and bioactive compounds, and can efficiently secrete an array of recombinant proteins and enzymes of varying sizes. 相似文献60.
Stiffness changes in cultured airway smooth muscle cells 总被引:7,自引:0,他引:7
An SS Laudadio RE Lai J Rogers RA Fredberg JJ 《American journal of physiology. Cell physiology》2002,283(3):C792-C801
Airwaysmooth muscle (ASM) cells in culture stiffen when exposed tocontractile agonists. Such cell stiffening may reflect activation ofthe contractile apparatus as well as polymerization of cytoskeletalbiopolymers. Here we have assessed the relative contribution of thesemechanisms in cultured ASM cells stimulated with serotonin(5-hydroxytryptamine; 5-HT) in the presence or absence of drugs thatinhibit either myosin-based contraction or polymerization offilamentous (F) actin. Magnetic twisting cytometry was used to measurecell stiffness, and associated changes in structural organization ofactin cytoskeleton were evaluated by confocal microscopy. We found that5-HT increased cell stiffness in a dose-dependent fashion and alsoelicited rapid formation of F-actin as marked by increased intensity ofFITC-phalloidin staining in these cells. A calmodulin antagonist (W-7),a myosin light chain kinase inhibitor (ML-7) and a myosin ATPaseinhibitor (BDM) each ablated the stiffening response but not theF-actin polymerization induced by 5-HT. Agents that inhibited theformation of F-actin (cytochalasin D, latrunculin A, C3 exoenzyme, andY-27632) attenuated both baseline stiffness and the extent of cellstiffening in response to 5-HT. Together, these data suggest thatagonist-evoked stiffening of cultured ASM cells requires actinpolymerization as well as myosin activation and that neitheractin polymerization nor myosin activation by itself is sufficient toaccount for the cell stiffening response. 相似文献