全文获取类型
收费全文 | 888篇 |
免费 | 45篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 23篇 |
妇产科学 | 6篇 |
基础医学 | 81篇 |
口腔科学 | 6篇 |
临床医学 | 84篇 |
内科学 | 102篇 |
皮肤病学 | 9篇 |
神经病学 | 124篇 |
特种医学 | 248篇 |
外科学 | 65篇 |
综合类 | 33篇 |
预防医学 | 40篇 |
眼科学 | 12篇 |
药学 | 49篇 |
中国医学 | 1篇 |
肿瘤学 | 51篇 |
出版年
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 20篇 |
2012年 | 23篇 |
2011年 | 26篇 |
2010年 | 30篇 |
2009年 | 33篇 |
2008年 | 38篇 |
2007年 | 26篇 |
2006年 | 30篇 |
2005年 | 36篇 |
2004年 | 25篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 32篇 |
1997年 | 43篇 |
1996年 | 32篇 |
1995年 | 26篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 18篇 |
1991年 | 27篇 |
1990年 | 17篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1969年 | 6篇 |
1967年 | 2篇 |
排序方式: 共有949条查询结果,搜索用时 15 毫秒
1.
2.
Possible relevance of pigeons as an indicator species for monitoring air pollution. 总被引:4,自引:1,他引:3
下载免费PDF全文
![点击此处可从《Environmental health perspectives》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P A Schilderman J A Hoogewerff F J van Schooten L M Maas E J Moonen B J van Os J H van Wijnen J C Kleinjans 《Environmental health perspectives》1997,105(3):322-330
Wild city pigeons were caught at four different locations in the Netherlands to represent areas of high (Amsterdam-high), moderate (Amsterdam-medium), and low (Maastricht and Assen) traffic density. It is assumed that local ambient air pollution decreases as a function of traffic density. In these pigeons levels of polycyclic aromatic hydrocarbon (PAH)-DNA adducts, oxidative DNA damage, and heavy metal residues were determined in kidney, lung, liver, and blood (no adduct analysis in blood). The contribution of leaded gasoline to total body lead content was estimated by measuring concentrations of Pb and its isotopes in blood. We also analyzed samples of ambient air particulate matter for PAH and heavy metal concentrations at the four different locations. Interregional differences in heavy metals in ambient air particulate matter were reflected relatively well by pigeon body loads. The higher lead and cadmium concentrations in blood, kidney, liver, and lung were found in the Amsterdam high traffic density area, followed by Amsterdam medium, Assen, and Maastricht. A high Pb concentration in blood coincided with relatively low 206Pb/207Pb values, indicating a high contribution of leaded gasoline to total blood Pb concentrations in pigeons from the Amsterdam high traffic density area. Significantly enhanced blood zinc values were found in pigeons from both locations in Amsterdam compared to pigeons from the other two areas. However, no differences in Zn tissue levels between the four different groups were found. Oxidative DNA damage, determined as the ratio of 7-Hydro-8-oxo-2'-deoxyguanosine/ deoxyguanosine, in pigeon liver was highest in Amsterdam-high, followed by Assen (low traffic density). Pb content, but not the Cd content, was positively associated with oxidative DNA damage in liver tissue. In lung tissue, a negative correlation was found between oxidative DNA damage and Zn content. These results indicate that the carcinogenic potential of Pb might be ascribed to oxygen radical formation, whereas Zn plays a protective role against oxidative DNA damage. Places with high and medium traffic density could be clearly discriminated on the basis of PAH levels in the ambient air. The PAH content in particulate air samples was not, however, reflected in total PAH-related DNA adduct levels because no differences could be observed in tissue adduct levels in pigeons from the four different locations. Our results indicate that wild city pigeons can be used as biological indicators of exposure to heavy metal pollution in outdoor air. 相似文献
3.
杨兴旺 《眼外伤职业眼病杂志》1994,16(3):202-204
采用综合治疗,抗炎,散瞳,局部治疗与全身应用免疫抑制疗法,治疗319例352眼外伤获得了满意的疗效,眼球挫伤104例,眼球穿孔伤93例,化学烧伤71例,眼炸伤46例。眼热烧伤5例,治疗包括及时清创胶粘或缝合,清除前房出血合理用皮质类固醇和免疫抑制剂等。眼球挫伤治愈率97.12%,穿透伤93.18%,热烧伤66.67%。319例眼外伤治愈率94.67%好转5.33%,并对各种治疗方法进行了讨论。 相似文献
4.
Computer simulation is used to assess the precision and accuracy of diffusion and perfusion parameters derived from a set of gradient-sensitized images. Under ideal experimental conditions, a moderate signal-to-noise level (ca. 40) suffices to estimate diffusion coefficients to within 20% relative precision. However, estimation of a typical cerebral perfusion fraction of 5% to within 20% relative precision requires signal-to-noise levels of ca. 400. Simulations also show that systematic errors in perfusion fraction estimation, as well as underestimation of the uncertainties in perfusion parameters (by chi-squared analysis), will be found at moderate signal-to-noise levels. 相似文献
5.
6.
Retrorenal colon: implications for percutaneous diskectomy 总被引:1,自引:0,他引:1
It has been recommended that computed tomography (CT) with the patient prone be performed in every patient undergoing percutaneous diskectomy; this would enable detection of a retrorenal location of the colon, which could interfere with the percutaneous procedure. In this evaluation of 346 prone CT studies, only one patient (0.29%) was found to have retrorenal or retropsoas bowel that would have been perforated at diskectomy. Because of this extremely low prevalence, the performance of prone CT in every patient undergoing percutaneous lumbar diskectomy is not believed to be necessary. 相似文献
7.
8.
PL Macken FRACO FRACS CJ Pavlin FRCS R Tuli MD GE Trope PhD FRCS 《Clinical & experimental ophthalmology》1995,23(3):217-220
Background: Spherophakia is an uncommon diagnosis. This is the first case report of spherophakia evaluated by ultrasound biomicroscopy.
Methods: Ultrasound biomicroscopy is a new diagnostic technique developed by one of the authors and provides images with microscopic resolution of the anterior segment. A patient with spherophakia was evaluated by ultrasound biomicroscopy (Zeiss-Humphrey, 50MHz) before and after YAG laser iridotomy.
Results: Ultrasound biomicroscopic assessment revealed a shallow anterior chamber, a very steep anterior lens curvature, iridolenticular contact, elongated zonules, and an increased distance between the lens equator and the ciliary processes. Angle closure glaucoma was due to a pupil block mechanism. The pupil block was relieved by YAG laser iridotomy.
Conclusions: Ultrasound biomicroscopy is a useful technique to confirm the diagnosis of spherophakia. The pupil block in spherophakia is relieved by YAG laser iridotomy. 相似文献
Methods: Ultrasound biomicroscopy is a new diagnostic technique developed by one of the authors and provides images with microscopic resolution of the anterior segment. A patient with spherophakia was evaluated by ultrasound biomicroscopy (Zeiss-Humphrey, 50MHz) before and after YAG laser iridotomy.
Results: Ultrasound biomicroscopic assessment revealed a shallow anterior chamber, a very steep anterior lens curvature, iridolenticular contact, elongated zonules, and an increased distance between the lens equator and the ciliary processes. Angle closure glaucoma was due to a pupil block mechanism. The pupil block was relieved by YAG laser iridotomy.
Conclusions: Ultrasound biomicroscopy is a useful technique to confirm the diagnosis of spherophakia. The pupil block in spherophakia is relieved by YAG laser iridotomy. 相似文献
9.
10.
1,6—二磷酸果糖对手术后应激病人应用全肠外营养支持效果的影响 总被引:3,自引:1,他引:2
本文在胃癌行全胃或胃大部切除术引起的中等程度应激病人,随机分组对比观察了全肠外营养或TPN加用1,6-二磷酸果糖的效果。结果显示,与单纯TPN相比,TPN加用FDP后血清皮质醇和胰高血糖素等应激激素水平有所下降,尿中3-甲基组氨酸排出减少,累积氮平衡增加。 相似文献