全文获取类型
收费全文 | 348105篇 |
免费 | 12666篇 |
国内免费 | 703篇 |
专业分类
耳鼻咽喉 | 3571篇 |
儿科学 | 11368篇 |
妇产科学 | 6385篇 |
基础医学 | 39118篇 |
口腔科学 | 5058篇 |
临床医学 | 29376篇 |
内科学 | 67785篇 |
皮肤病学 | 3433篇 |
神经病学 | 33795篇 |
特种医学 | 14862篇 |
外国民族医学 | 13篇 |
外科学 | 54406篇 |
综合类 | 4593篇 |
现状与发展 | 3篇 |
一般理论 | 201篇 |
预防医学 | 30816篇 |
眼科学 | 7448篇 |
药学 | 20673篇 |
中国医学 | 826篇 |
肿瘤学 | 27744篇 |
出版年
2023年 | 638篇 |
2022年 | 1028篇 |
2021年 | 2862篇 |
2020年 | 1763篇 |
2019年 | 2894篇 |
2018年 | 24893篇 |
2017年 | 19430篇 |
2016年 | 21915篇 |
2015年 | 4309篇 |
2014年 | 5855篇 |
2013年 | 8572篇 |
2012年 | 18073篇 |
2011年 | 32620篇 |
2010年 | 25054篇 |
2009年 | 17488篇 |
2008年 | 30431篇 |
2007年 | 33336篇 |
2006年 | 12235篇 |
2005年 | 14164篇 |
2004年 | 14751篇 |
2003年 | 15171篇 |
2002年 | 12987篇 |
2001年 | 1727篇 |
2000年 | 1505篇 |
1999年 | 1733篇 |
1998年 | 2514篇 |
1997年 | 2211篇 |
1996年 | 1780篇 |
1995年 | 1675篇 |
1994年 | 1507篇 |
1993年 | 1405篇 |
1992年 | 1073篇 |
1991年 | 1030篇 |
1990年 | 945篇 |
1989年 | 887篇 |
1988年 | 882篇 |
1987年 | 754篇 |
1986年 | 856篇 |
1985年 | 943篇 |
1984年 | 1239篇 |
1983年 | 1192篇 |
1982年 | 1660篇 |
1981年 | 1512篇 |
1980年 | 1455篇 |
1979年 | 787篇 |
1978年 | 914篇 |
1977年 | 803篇 |
1976年 | 715篇 |
1975年 | 571篇 |
1974年 | 612篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Louis S. Pilotto Robert M. Douglas 《Australian and New Zealand journal of public health》1992,16(3):245-250
Abstract: Nitrogen dioxide is produced from the combustion of fossil fuels and as an emission from gas-fired appliances, and is also a component of tobacco smoke. Nitrogen dioxide has been shown in experimental animals to be toxic to the respiratory tract. A number of recent studies have suggested that children exposed to significant levels of nitrogen dioxide in the home may be more susceptible to respiratory illness than children exposed to normal ambient levels. Respiratory illness is a major cause of morbidity in children everywhere. Here, we review the available evidence of this association and explore methodological issues in measurement of nitrogen dioxide exposure— misclassification of subjects, symptom bias and confounding. It has recently been shown that some New South Wales school rooms, where unflued gas heaters are often used as a source of warmth, have nitrogen dioxide levels which are above recommended ambient levels for outside air. This has underlined the need for setting standards for indoor levels of various pollutants, and cohort studies are suggested, to include personal monitoring and prospective data collection techniques. 相似文献
972.
Michelle McKerral Pierre Lachapelle François Tremblay Robert C. Polomeno Marie-Sylvie Roy Raquel Beneish Franco Leporé 《Documenta ophthalmologica. Advances in ophthalmology》1995,91(2):181-193
The contribution of each monocular pathway to the timing of the binocular pattern visual evoked potential was assessed in situations where a significant interocular timing discrepancy was observed. Monocular and binocular pattern visual evoked potentials to 0.5° checks were recorded from normal subjects, normal subjects in whom one eye was blurred, patients with monocular amblyopia, and patients with resolved unilateral optic neuritis. Normal subjects showed facilitation, while suppression was evidenced in subjects with monocular blurring. In patients with amblyopia, the affected pathway had no effect on binocular pattern visual evoked potential latency, suggesting that the amblyopic eye was suppressed. In contrast, all patients with optic neuritis showed binocular averaging. Our results show that different forms of binocular interaction are evidenced in normal subjects, in amblyopia and in optic neuritis, and suggest that a comparative analysis of monocular and binocular pattern visual evoked potential peak times brings valuable information to the clinical evaluation that could be used to distinguish disease processes further.Abbreviation BPVEP
binocular pattern visual evoked potential 相似文献
973.
974.
975.
Marwan H. Saab Douglas C. Smith Paul K. Aka Robert W. Brownlee J. David Killeen 《Cardiovascular and interventional radiology》1992,15(4):211-216
Percutaneous transluminal balloon angioplasty (PTA) was performed in 17 tibial arteries with an average cross-sectional area
stenosis of 92% (range 75–99%) in 13 patients (14 limbs) for limb salvage. In 4 of 14 lower extremities, PTA of femoropopliteal
arteries was also performed. Technical success with 50% or less residual stenosis was achieved in all 17 tibial vessels. At
approximately 2 months after PTA, clinical improvement had occurred in 10 of 14 limbs; no patient was made worse. Most recent
follow-up (mean 19 months, range 8–34 months) revealed continued satisfactory clinical success with no further vascular intervention
in 9 of these 10 limbs (one patient died). Short segmental stenoses, residual stenoses less than 40% following PTA, and absence
of diabetes or gangrene appear to be predictors of favorable clinical outcomes. Our results suggest that PTA of focal tibial
stenosis is an effective and safe treatment modality in properly selected patients and that wider use of PTA may be justified. 相似文献
976.
Purpose. This paper compares unsteady-state and steady-state methods for estimating dermal absorption or analyzing dermal absorption data. The unsteady-state method accounts for the larger absorption rates during short exposure times as well as the hydrophilic barrier which the viable epidermis presents to lipophilic chemicals.
Methods. Example calculations for dermal absorption from aqueous solutions are presented for five environmentally relevant chemicals with molecular weights between 50 and 410 and log10Kow between 0.91 and 6.8: chloromethane, chloroform, chlordane, 2,3,7,8-TCDD, and dibenz(a,h)anthracene. Also, the new method is used to evaluate experimental procedures and data analyses of in vivo and in vitro permeation measurements.
Results. In the five example cases, we show that the steady-state approach significantly underestimated the dermal absorption. Also, calculating permeability values from cumulative absorption data measured for exposure periods less than 18 times the stratum corneum lag time will overestimate the actual permeability.
Conclusions. In general, steady-state predictions of dermal absorption will underestimate dermal absorption predictions which consider unsteady-state conditions. Permeability values calculated from data sets which include unsteady-state data will be incorrect. Strategies for analyzing in vitro diffusion cell experiments and confirming steady state are described. 相似文献
977.
978.
979.
Inhibitory motor control in children with attention-deficit/hyperactivity disorder: event-related potentials in the stop-signal paradigm. 总被引:4,自引:0,他引:4
Aneta Dimoska Stuart J Johnstone Robert J Barry Adam R Clarke 《Neuropsychopharmacology》2003,54(12):1345-1354
BACKGROUND: The aim of the study was to investigate the inhibitory control of an ongoing motor response and to identify underlying neural deficiencies, manifested in event-related potentials, that cause poorer inhibitory performance in children with attention-deficit/hyperactivity disorder. METHODS: A stop-signal paradigm with a primary visual task and auditory stop signal was used to compare performance in 13 children with attention-deficit/hyperactivity disorder and 13 control children, while event-related potentials were recorded simultaneously. RESULTS: Children with attention-deficit/hyperactivity disorder showed poorer inhibitory performance through a slower inhibitory process. Inhibitory processing of auditory stop signals was marked by a frontal N2 component that was reduced in the attention-deficit/hyperactivity disorder group relative to controls. A central positive component (P3) was associated with the success of inhibiting a response, but there were no group differences in its amplitude or latency. CONCLUSIONS: Findings support the hypothesis of deficient inhibitory control in children with attention-deficit/hyperactivity disorder. Slower inhibitory processing appears to be due to a specific neural deficiency that manifests in the processing of the stop signal as attenuated negativity in the N2 latency range. 相似文献
980.