首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6578篇
  免费   312篇
  国内免费   33篇
医药卫生   6923篇
  2023年   74篇
  2022年   51篇
  2021年   231篇
  2020年   131篇
  2019年   152篇
  2018年   219篇
  2017年   141篇
  2016年   179篇
  2015年   189篇
  2014年   287篇
  2013年   344篇
  2012年   528篇
  2011年   486篇
  2010年   254篇
  2009年   288篇
  2008年   399篇
  2007年   394篇
  2006年   395篇
  2005年   385篇
  2004年   323篇
  2003年   302篇
  2002年   245篇
  2001年   92篇
  2000年   89篇
  1999年   77篇
  1998年   50篇
  1997年   40篇
  1996年   38篇
  1995年   32篇
  1994年   20篇
  1993年   20篇
  1992年   38篇
  1991年   43篇
  1990年   42篇
  1989年   29篇
  1988年   31篇
  1987年   23篇
  1986年   20篇
  1985年   30篇
  1984年   28篇
  1983年   19篇
  1979年   13篇
  1978年   14篇
  1977年   13篇
  1974年   12篇
  1973年   13篇
  1972年   9篇
  1971年   9篇
  1970年   11篇
  1969年   8篇
排序方式: 共有6923条查询结果,搜索用时 31 毫秒
71.
72.
Ocular toxicity of intravitreal clarithromycin.   总被引:5,自引:0,他引:5  
OBJECTIVE: To investigate the ocular toxicity and clearance of intravitreal clarithromycin lactobionate (Klaricid) and to determine the highest nontoxic dose. MATERIALS AND METHODS: To evaluate toxicity, 24 New Zealand white rabbits were divided into six groups (four rabbits each). Rabbits were examined preoperatively and electroretinography (ERG) was performed. The left eyes of the animals served as controls and received intravitreal injection of 0.1 mL sterile water. Klaricid (0.1 mL) was injected into the midvitreous cavity of the right eyes at concentrations of 25 microg, 250 microg, 500 microg, 1.0 mg, 2.0 mg, and 4.0 mg/0.1 mL. The animals were followed up to 15 days postinjection by clinical examination and ERG. The animals were killed and the eyes were enucleated and processed for light microscopy. Ten New Zealand rabbits were used for the vitreous clearance study as drug test rabbits and two additional rabbits were used to generate control retina and vitreous. The highest nontoxic dose (1 mg) was injected into the vitreous and the concentration of clarithromycin in the vitreous was determined using high-performance liquid chromatography at various time intervals after injection. RESULTS: Cataract occurred after intravitreal doses of 2.0 and 4.0 mg. Electroretinography showed decreasing b-wave amplitude with both dark- and light-adapted stimulus in the 4.0-mg group; it was normal in other groups. Histopathologic sections showed localized retinal necrosis and disorganization with the 2.0 and 4.0 mg dosage. No histologic changes were found in the other groups. The half-life of intravitreal clarithromycin was found to be 2 hours. No metabolites of clarithromycin were observed in the vitreous samples. CONCLUSION: Intravitreal clarithromycin lactobionate is nontoxic to rabbit eyes up to a dose of 1.0 mg. Because of its broad-spectrum antibiotic effect and appropriate half-life in the vitreous, it may be a good choice for intravitreal treatment of susceptible organisms.  相似文献   
73.
We used in vitro autoradiography to identify the endothelin-1 receptor subtype(s) in the nucleus raphe obscurus of rats. These studies showed dense binding of [125I]PD151242 (for endothelin ETA receptors), while tissues incubated with [125I]BQ3020 (for endothelin ETB receptors) had low binding. In addition, we examined the effects of the endothelin receptor antagonists FR 139317 (endothelin ETA receptor-selective antagonist), SB 209670 (endothelin ETA/ETB receptor-non-selective antagonist) and BQ-788 (endothelin ETB receptor-selective antagonist) on the blood pressure responses following administration of endothelin-1 into the nucleus raphe obscurus. The basal mean arterial blood pressure (MABP) of the rats was 110 ± 7 mmHg (n = 5). This was decreased in a dose-dependent manner by endothelin-1 (0.1, 1 and 10 pmol) microinjected into the nucleus raphe obscurus. This effect occurred within 1–6 s and recovered within 4 ± 1.2 min at a dose of 10 pmol. The doses of 0.1 pmol and 1 pmol ET-1 had responses which lasted 1 ± 0.4 min and 2 ± 0.2 min, respectively. Small decreases in heart rate accompanied the MAP responses to endothelin-1. For instance, the heart rate decreased by 16 ± 4 beats min–1 after 10 pmol endothelin-1 (control, 366 ± 6 beats min–1, n = 5). Decreases in blood pressure induced by endothelin-1 were greatly reduced by pre-administration to the nucleus raphe obscurus of FR139317 (5 nmol/rat) or SB209670 (3 nmol/rat; 97 ± 7% and 95 ± 6%, P < 0.01, n = 5, respectively), but were not affected by BQ-788 (50 nmol/rat; 8 ± 3%, P > 0.05, n = 5). The antagonists did not influence heart rate when injected to the nucleus raphe obscurus prior to endothelin-1. FR139317 (0.5 nmol) and SB209670 (0.3 nmol) had no effects on endothelin-induced changes in arterial blood pressure. Therefore, the autoradiographic study showed that there are binding sites for ET-1 within the nucleus raphe obscurus of rats, which are predominantly of ETA type. The in vivo study showed that ETA receptors are the predominant mediators of depressor responses induced by endothelin-1 injected into this nucleus. Received: 6 August 1998 / Accepted: 16 February 1999  相似文献   
74.
Summary Three families are described which include members with typical Friedreich's disease (FD) and others who are ataxic but do not satisfy all the diagnostic criteria for that disease. In family A two patients have an early-onset, rapidly progressive FD, while two others have a late-onset, more benign form. In families B and C one member has typical FD, and another has a similar ataxic syndrome, except for preservation of knee jerks. Laboratory evaluation is consistent with the diagnosis of FD in all cases. FD diagnosis appears justified in secondary cases with late onset or preserved tendon reflexes, provided that the index case fulfils all diagnostic criteria. Whether the diagnosis of FD is tenable in sporadic atypical cases remains to be seen. Echocardiographic and neurophysiological examination may be valuable in classifying such cases.  相似文献   
75.
A longitudinal growth study with monthly measurements during the 1st year of life was conducted by nine paediatricians working in private practice in Zurich. Of 92 children, none was lost to the study and only 32 of 1104 planned visits were missed; the quality of the measurements was comparable to that of a specialised university clinic. Compared to the Zurich Longitudinal Growth Studies, children of this study were considerably heavier and taller. In 92% of the subjects, growth velocity was at least once outside the reference range (3rd–97th percentile). For weight increments, the corresponding proportion was 87%. Conclusions The data indicate that current standards for the 1st year of life for the Zurich area might no longer be appropriate and need to be updated. The currently used velocity percentiles based on 3-monthly measurements are not suitable to assess individual height and weight increments calculated from monthly measurements. Received: 9 June 1997 / Accepted in revised form: 21 November 1997  相似文献   
76.
77.
To evaluate left ventricular myocardial mass and function as well as ostial coronary artery cross-sectional area in endurance athletes, an athlete group of 12 highly trained rowers and a control group of 12 sedentary healthy subjects underwent MR examination. An ECG-gated breath-hold cine gradient-echo sequence was used to calculate myocardial mass, end-diastolic and end-systolic volumes, stroke volume, and cardiac output, all related to body surface area, as well as ejection fraction. A 3D fat-saturated ECG- and respiratory-triggered navigator echo sequence was used to evaluate coronary arteries: left main (LM), left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA). Cross-sectional area was calculated and divided for body surface area. Myocardial mass was found significantly larger in athlete group than in control group (p = 0.0078), the same being for end-diastolic volume (p = 0.0078), stroke volume (p = 0.0055), LM (p = 0.0066) and LAD (p = 0.0129). No significant difference was found for all the remaining parameters. Significant correlation with myocardial mass was found for LM (p < 0.001) and LAD (p = 0.0340), not for LCx and RCA. Magnetic resonance imaging is a useful tool in evaluating the myocardial hypertrophy and function of athlete's heart. Magnetic resonance angiography is a valuable noninvasive method to visualize the correlated cross-sectional area increase of the left coronary artery system. Received: 25 March 1999; Revised: 31 August 1999; Accepted: 1 September 1999  相似文献   
78.
Free-radical formation may play a role in postoperative complications of phacoemulsification (e.g., corneal endothelium damage from mechanical injury). The present experiments were aimed at investigating whether different molecular weight ranges (2000-2600, 2600-3200, or 3200-3800 kDa) of hyaluronan may influence free radical formation, corneal endothelium damage, and inflammation parameters after phacoemulsification in the rabbit eye. The viscoelastic substance was injected in the anterior chamber of rabbits' eyes before phacoemulsification, at a 2.5% concentration. The formation of free radicals was determined by adding luminol to the irrigation media and measuring the chemoluminescence in eyes. The corneal endothelial damage was evaluated by measuring the corneal central thickness by pachimetry. The inflammation parameters were measured by calculation in aqueous humor of peak levels of leukocytes and prostaglandin E(2) (PGE(2)) and evaluation in uveal tissue of myeloperoxidase activity. Hyaluronan decreased by about 58-60% free-radical formation during phacoemulsification, reduced by about 76-80% modifications in mean corneal thickness and by about 54-61% the corneal endothelial cell loss in all molecular weight ranges used. No difference was found among various molecular weight ranges. The highest molecular weight range showed to be more potent than the lowest range for reduced number of inflammation cells and level of PGE(2) in aqueous humor. Thus, hyaluronan reduces free-radical formation, exerts protection on the corneal endothelium and exerts anti-inflammation properties after phacoemulsification in rabbits. The latter effect seems to depend on the molecular weight of the substance.  相似文献   
79.
We report the case of a 30-year-old woman with cystic fibrosis (CF) chronically infected with Pseudomonas aeruginosa who delivered and breast-fed a healthy boy. While breast-feeding the woman had to undergo an i.v. antibiotic course with tobramycin, due to pulmonary exacerbation. Tobramycin was not detected in her milk and lactation could be continued. This is the first time that the presence of tobramycin in the milk of a CF woman during i.v. administration has been investigated.  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号