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111.
Influence of low and high frequency inputs on spike timing in visual cortical neurons 总被引:6,自引:2,他引:4
Cortical neurons in vivo respond to sensory stimuli with the generation of
action potentials that can show a high degree of variability in both their
number and timing with repeated presentations as wells as, on occasion, a
high degree of synchronization with other cortical neurons, including in
the gamma frequency range of 30-70 Hz. Here we examined whether or not this
variability may arise from the intrinsic mechanisms of action potential
generation in cortical regular spiking, fast spiking and intrinsic
burst-generating neurons maintained in vitro. For this purpose, we
performed intracellular recordings in slices of ferret visual cortex and
activated these cells with the intracellular injection of various current
waveforms. Some of these waveforms were derived from barrages of
postsynaptic potentials evoked by visual stimulation recorded in vivo;
others were artificially created and contained various amounts of gamma
range fluctuations; finally, others consisted of swept-sinewave current
(ZAP current) functions. Using such stimuli, we found that, as expected
given the resistive and capacitive properties of cortical neurons, low
frequencies have a larger effect on the membrane potential of cortical
neurons than do higher frequencies. However, increasing the amount of gamma
range fluctuations in a stimulus leads to more precise timing of action
potentials. This suggests that different frequencies play different roles,
low frequencies being efficient for depolarizing cells with high
frequencies increasing the precision of action potential timing. In
parallel to increases in temporal precision, the addition of higher
frequency components increases the range of interspike intervals present in
the action potential discharge. These results suggest that higher frequency
components such as gamma range fluctuations may facilitate the generation
of action potentials with a high temporal precision while at the same time
exhibiting a high degree of variability in interspike intervals on single
trials. This temporal precision may facilitate the use of temporal codes or
the generation of precise synchronization for the transmission and analysis
of information within cortical networks.
相似文献
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113.
Arunava Kali MV Pravin Charles Mariya Joseph Noyal Umadevi Sivaraman Shailesh Kumar Joshy M Easow 《The Australasian medical journal》2013,6(8):387-391
Background
Candida species are emerging as a potentially pathogenic fungus in patients with broncho-pulmonary diseases. The synergistic growth promoting association of Candida and Mycobacterium tuberculosis has raised increased concern for studying the various Candida spp . and its significance in pulmonary tuberculosis patients during current years.Aims
This study was undertaken with the objective of discovering the prevalence of co-infection caused by different Candida species in patients with pulmonary tuberculosis.Method
A total of 75 patients with pulmonary tuberculosis diagnosed by sputum Ziehl-Neelsen staining were included in the study. Candida co-infection was confirmed using the Kahanpaa et al. criteria. Candida species were identified using gram stain morphology, germ tube formation, morphology on cornmeal agar with Tween-80, sugar fermentation tests and HiCrome Candida Agar.Results
Candida co-infection was observed in 30 (40%) of patients with pulmonary tuberculosis. Candida albicans was the most common isolate observed in 50% of the patients with co-infection, followed by C. tropicalis (20%) and C. glabrata (20%). Candida co-infection was found in 62.5% of female patients, while it was observed in only 29.4% of the male patients (P value 0.0133). Mean ± SD age of the patients with C. glabrata infection was 65.83 ± 3.19, while the mean ± SD age of the patients with other Candida infections was 43.25 ± 20.44 (P value 0.0138).Conclusion
Many patients with pulmonary tuberculosis have co-infection with Candida spp. The prevalence of non-albicans Candida species is increasing and may be associated with inadequate response to anti-tubercular drugs. C. glabrata infection has a strong association with old age. 相似文献114.
F?de la?PortillaEmail author ML?Reyes-Díaz MV?Maestre RM?Jiménez-Rodríguez AM?García-Cabrera JM?Vázquez-Monchul JM?Díaz-Pavón FC?Padillo-Ruiz 《International journal of colorectal disease》2017,32(3):437-440
Background
Faecal incontinence (FI) is both a medical and social problem, with an underestimated incidence. For patients with internal anal sphincter damage, implantation of biomaterial in the anal canal is a recognised treatment option. One such material, Gatekeeper?, has previously shown promising short- and medium-term results without any major complications, including displacement. The main aim of the present study is to assess the degree to which displacement of Gatekeeper prostheses may occur and to determine whether this is associated with patient outcomes.Methods
Seven patients (six females) with a mean age of 55.6 years [50.5–57.2] and a mean FI duration of 6 ± 2 years were prospectively enrolled in the study. Each subject was anaesthetised and underwent implantation of six prostheses in the intersphincteric region, guided by endoanal 3D ultrasound (3D-EAU). Follow-up was performed at post-interventional months 1, 3, and 12 (median 12 ± 4 months), during which data were obtained from a defaecation diary, Wexner scale assessment, anorectal manometry (ARM), 3D-EAU, and a health status and quality of life questionnaire (FIQL).Results
At 3-month follow-up, 3D-EAU revealed displacement of 24/42 prostheses in 5/7 patients. Of these, 15 had migrated to the lower portion and 9 to the upper portion of the anal canal and rectum. Despite this migration, treatment was considered successful in 3/7 patients. In one patient, it was necessary to remove a prosthesis due to spontaneous extrusion.Conclusions
We have shown that displacement of the Gatekeeper? prosthesis occurs, but is not associated with poorer clinical outcomes.115.
116.
117.
Digital and conventional chest imaging: a modified ROC study of observer performance using simulated nodules 总被引:5,自引:0,他引:5
A modified receiver operating characteristic (ROC) study was performed in which five readers were asked to locate multiple nodules on images of an anthropomorphic phantom obtained with a prototype digital radiographic chest unit and with a conventional chest unit. Results indicate that when nodules were projected over the lungs, a significantly greater number (significant at the 5% level) were identified on conventional radiographs, whereas for nodules projected over the mediastinum, the digital images were notably superior (difference significant at the 2% level). An error analysis of the multiple nodule problem and pseudo-ROC curves are presented. The modified ROC study does not suffer from the positional ambiguity inherent in most ROC studies and is efficient in acquiring data. 相似文献
118.
119.
Seventy-five patients (75 eyes) with central involution chorioretinal dystrophy (non-exudative type at the progression stage) were followed up. All of them received low-intensity laser therapy. Irradiation of 890 nm, 644 nm and 500 nm was used in groups 1, 2 and 3, respectively. The study purpose was to compare the efficiency of wavelengths. Visual acuity and retinal sensitivity were determined. The results were evaluated immediately after treatment and in 3 months. The maximal improvement in visual acuity and retinal sensitivity was in those who received 890 nm laser therapy; 500 nm irradiation--a less pronounced effect and 640 nm--the lowest one. We attribute such distribution of efficiency to a proliferation type of each irradiation range in the macular zone. 相似文献
120.