首页 | 本学科首页   官方微博 | 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   2380篇
  免费   199篇
  国内免费   62篇
耳鼻咽喉   9篇
儿科学   75篇
妇产科学   50篇
基础医学   353篇
口腔科学   124篇
临床医学   218篇
内科学   518篇
皮肤病学   20篇
神经病学   158篇
特种医学   138篇
外科学   250篇
综合类   34篇
一般理论   4篇
预防医学   253篇
眼科学   22篇
药学   185篇
中国医学   7篇
肿瘤学   223篇
  2022年   11篇
  2021年   21篇
  2020年   15篇
  2019年   34篇
  2018年   36篇
  2017年   40篇
  2016年   46篇
  2015年   38篇
  2014年   62篇
  2013年   77篇
  2012年   88篇
  2011年   83篇
  2010年   71篇
  2009年   63篇
  2008年   115篇
  2007年   132篇
  2006年   124篇
  2005年   110篇
  2004年   93篇
  2003年   87篇
  2002年   76篇
  2001年   61篇
  2000年   64篇
  1999年   79篇
  1998年   75篇
  1997年   60篇
  1996年   47篇
  1995年   51篇
  1994年   56篇
  1993年   38篇
  1992年   47篇
  1991年   40篇
  1990年   30篇
  1989年   56篇
  1988年   46篇
  1987年   42篇
  1986年   40篇
  1985年   39篇
  1984年   25篇
  1983年   22篇
  1982年   32篇
  1981年   27篇
  1980年   20篇
  1979年   14篇
  1978年   20篇
  1977年   22篇
  1976年   19篇
  1975年   15篇
  1972年   12篇
  1969年   11篇
排序方式: 共有2641条查询结果,搜索用时 218 毫秒
91.
Serum markers detect the presence of liver fibrosis: a cohort study   总被引:47,自引:0,他引:47  
BACKGROUND & AIMS: Histologic examination of a liver biopsy specimen is regarded as the reference standard for detecting liver fibrosis. Biopsy can be painful and hazardous, and assessment is subjective and prone to sampling error. We developed a panel of sensitive automated immunoassays to detect matrix constituents and mediators of matrix remodeling in serum to evaluate their performance in the detection of liver fibrosis. METHODS: In an international multicenter cohort study, serum levels of 9 surrogate markers of liver fibrosis were compared with fibrosis stage in liver biopsy specimens obtained from 1021 subjects with chronic liver disease. Discriminant analysis of a test set of samples was used to identify an algorithm combining age, hyaluronic acid, amino-terminal propeptide of type III collagen, and tissue inhibitor of matrix metalloproteinase 1 that was subsequently evaluated using a validation set of biopsy specimens and serum samples. RESULTS: The algorithm detected fibrosis (sensitivity, 90%) and accurately detected the absence of fibrosis (negative predictive value for significant fibrosis, 92%; area under the curve of a receiver operating characteristic plot, .804; standard error, .02; P < .0001; 95% confidence interval, .758-.851). Performance was excellent for alcoholic liver disease and nonalcoholic fatty liver disease. The algorithm performed equally well in comparison with each of the pathologists. In contrast, pathologists' agreement over histologic scores ranged from very good to moderate (kappa = .97-.46). CONCLUSIONS: Assessment of liver fibrosis with multiple serum markers used in combination is sensitive, specific, and reproducible, suggesting they may be used in conjunction with liver biopsy to assess a range of chronic liver diseases.  相似文献   
92.

Background

Adequate vitamin D concentrations during pregnancy are necessary to neonatal calcium homeostasis, bone maturation and mineralization. The aim of study is to evaluate serum vitamin D concentrations in mothers and their newborns and effect of vitamin D deficiency on pregnancy outcomes.

Methods

552 pregnant women were recruited from Tehran University educating hospitals in the winter of 2002. Maternal and cord blood samples were taken at delivery. The serum was assayed for 25-hydroxyvitamin D3, calcium, phosphorus and parathyroid hormone.

Results

The prevalence of vitamin D deficiency in maternal and cord blood samples were 66.8% and 93.3%, respectively (<35 nmol/l). There was significant correlation between maternal and cord blood serum concentrations of vitamin D. In mothers with vitamin D deficiency, cord blood vitamin D concentrations was lower than those from normal mothers (P = .001). Also, a significant direct correlation was seen between maternal vitamin D intake and weight gain during pregnancy.

Conclusion

Consideration to adequate calcium and vitamin D intake during pregnancy is essential. Furthermore, we think it is necessary to reconsider the recommendation for vitamin D supplementation for women during pregnancy.  相似文献   
93.
目的:了解中国不同地区间中老年人群膝关节骨性关节炎患病危险因素。方法:调查时间为2005—07/08。①从中国六大行政区(西北,华北,华东。中南,东北,西南)选出六城市(西安,石家庄,上海。广州,哈尔滨市,成都),用分层多阶段整群抽样方法,抽取6218名40岁及以上具有正式户口常住男女人群进行膝关节骨性关节炎的流行病学问卷调查(包括一般情况、现病史、既往史、体格检查、X射线片检查情况和疾病诊断6个方面,共计94个问题141个变量指标),并对其中4808名有症状者进行X射线平片膝正侧位投照。②膝关节骨性关节炎诊断标准为临床症状阳性加X射线Kellgren & Lawrence分级二级及以上者。③计算患病率,并采用Epilnf06.0和SPSS 10.0软件对其中83个变量进行多因素非条件Logistfc回归分析,表示疾病与暴露因素之间联系强度的指标用比值比(OR),若OR〉1,说明疾病发生危险性增加,与暴露因素呈正关联;若OR〈1,说明疾病发生危险性减少,与暴露因素呈负关联。 结果:①六城市膝关节骨性关节炎总患病率为15.6%,其中西安7.7%,石家庄11.2%,上海9.8%。广州30.5%,哈尔滨16.9%,成都17.5%,各城市患病率比较差异显著(P〈0.01)。②Logistic回归分析膝关节骨性关节炎在大部分城市有共同的危险因素如年龄大(OR=1.032—1.181),使用蹲坑排便年限长(OR=1.021-1.077),体质量高(OR=1.048—1.073),和开始饮酒年龄大(OR=1.008~1.028);而从事专职体育运动(OR=1.651,西安),骨质疏松病史(OR=3.311,石家庄),吸烟(OR=2.654,石家庄),类风湿关节炎病史(OR=4.964,上海),文化程度高(OR=2.593,上海),女性(OR=2.510,广州),姐妹骨关节炎史(OR=13.251,哈尔滨),母亲骨关节炎史(OR=5.683,成都)等危险因素分别在不同地区出现. 结论:年龄大、使用蹲坑排便年限长、体质量高和开始饮酒年龄大是中国六地区膝关节骨性关节炎患病的共同危险因素,同时,不同地区主要危险因素又有一定差异。  相似文献   
94.
目的:观察经介入途径移植自体骨髓单个核细胞在股骨头坏死治疗中的应用,并评价其疗效。方法:选择2004-07/2005-11在解放军四六三院细胞治疗中心住院的,具有完整随访资料的股骨头坏死确诊患者共54例91髋。纳入确诊股骨头坏死,有关节疼痛、功能障碍等症状患者,性别、年龄不限;排除有严重心力衰竭、严重肾功能异常等不能耐受手术者。符合纳入标准54例,男45例,女9例,12~68岁。按ARCO分期Ⅱ期42髋,Ⅲ期47髋,Ⅳ期2髋。实验对象对治疗的相关内容知情同意并签知情同意。干预措施:抽取患者髂后上嵴骨髓进行单个核细胞悬液的制备。在DSA监视下将采集的单个核细胞混悬液经股动脉行Seldinger法穿刺,穿刺成功后,置入4F动脉鞘,经动脉鞘置入Cobra导管,将导管超选择至闭孔动脉及旋股内外侧动脉,平均注入单个核细胞悬液。术后定期随访症状变化情况,1年后复查X射线或CT,随访疼痛、关节活动度等情况。实验评估:①疼痛指数:无疼痛症状为3分,Harris髋关节评分疼痛分级A级;时有隐痛2分,Harris髋关节评分疼痛B级;轻度疼痛为1分,Harris髋关节评分疼痛C级;中度疼痛为0分,Harris髋关节评分疼痛D级。②功能指数:髋关节屈、伸、展、收、旋转度评分达Harris髋关节活动范围评分4~5分为3分;3~4分为2分;2~3分为1分;小于2分为0分。③X射线平片指数:股骨头形态无变化,应力骨小梁清晰,坏死区明显缩小为3分;坏死区略缩小为2分;治疗前后无明显变化为1分;坏死区扩大为0分。④血管指数:治疗后旋股内、外侧动脉及其分支增粗、增多,延长1cm以上者3分;1~0.5cm者2分;小于0.5cm者1分,无变化者0分。结果:54例患者均完成疼痛症状、关节功能及影像学随访1年。①术后12个月复查疼痛消失9髋,缓解61髋,无缓解21髋,缓解率为76.9%。②关节功能缓解33髋,无缓解58髋,缓解率为36.3%。③1年后X射线平片或CT、MRI示股骨头区可见不同程度的股骨头坏死区骨质密度改变,坏死区有吸收、缩小,股骨头形态变圆滑规整,改善28髋,无缓解或加重63髋,缓解率为30.1%。④12例24髋完成术后12个月复查股骨头供血动脉数字减影血管造影,好转18髋,好转率为72.2%。结论:经介入途径移植自体骨髓单个核细胞治疗股骨头坏死损伤小,可缓解临床相关症状。  相似文献   
95.
Hyperbaric oxygen and cerebral infarction in the gerbil   总被引:6,自引:0,他引:6  
The effectiveness of hyperbaric oxygen in reducing the incidence of cerebral infarction during the first 36 hours after occlusion of the right common carotid artery was investigated in gerbils. After carotid ligation, the gerbils were divided into four groups: controls, which breathed air at ambient pressure; group 1, which received hyperbaric oxygen at 1.5 atmospheres absolute pressure (ATA) for 36 hours, with a 5-minute, 1.5-ATA air break each hour; group 2, which received hyperbaric oxygen at 1.5 ATA for 1 hour alternating with 1 hour air at 1 ATA, for 36 hours; and group 3, which received hyperbaric oxygen at 1.5 ATA with hourly 5-minute air breaks for 18 hours, and ambient air for the second 18 hours. Neurological evaluations and staining of the brain with tetrazolium revealed the following results at 36 hours after carotid ligation: 72% of the controls had cerebral infarcts; 26% of the gerbils in group 1 had infarcts, but all animals died at 24-36 hours after beginning hyperbaric oxygen exposure from oxygen toxicity; 44% of the gerbils in group 2 had infarcts; 11% of the gerbils in group 3 had infarcts during the first 18 hours after carotid ligation, and no infarcts developed in the 18 hours that followed. Hyperbaric oxygen reduces the incidence of cerebral infarction after carotid artery ligation, presumably by allowing time for collateral circulation to develop.  相似文献   
96.
A model of reversible obstructive jaundice in the rat   总被引:5,自引:0,他引:5  
A model of reversible, extrahepatic biliary obstruction is described. Vessel loop blockade of the biliary tree results in obstructive jaundice while removal of the exteriorized vessel loop provides internal biliary drainage without subsequent laparotomy. This technique combined with a system for chronic venous infusion and arterial blood sampling in the unrestrained rat is ideal for long-term metabolic studies of obstructive jaundice. Male Fisher 344 rats (275-350 g) underwent either the combined procedure of total biliary tract blockade and vascular access or sham operation. Mean serum bilirubin was significantly elevated (12.7 +/- 8.9 mg/dl) in the experimental group and following relief of biliary obstruction significantly dropped below 1 mg/dl in all animals except one. Concomitant changes in alkaline phosphatase, glutamate oxaloacetate transaminase, and glutamate pyruvate transaminase were seen. Experimental and control rats initially lost weight following laparotomy; however, mean body weight stabilized by the 5th postoperative day and was similar in both groups on the 10th postoperative day. This combined procedure is a simple, effective and reproducible method of obstructive jaundice.  相似文献   
97.

Introduction  

The effect of age and gender on time to perforation in acute appendicitis has not been well characterized. This study examined the relationship between duration of disease and appendiceal perforation in different subgroups of age and gender.  相似文献   
98.
99.
100.
The authors report 2 patients who experienced medial wall blowout fractures. Both patients presented with significant restriction of upgaze, mild proptosis, and crepitus of the upper lid. Computed tomography revealed significant pneumo-orbita filling the superior orbit with inferior displacement of the muscle cone and subcutaneous emphysema. No floor fractures were seen in either patient, but in both cases, the medial wall was breached and was almost certainly the source of the intraorbital air. Patients were managed conservatively, and the vertical gaze deficiencies resolved after 3 to 5 days. Large amounts of intraorbital and extraorbital air in the absence of a floor fracture can imitate inferior rectus entrapment and could potentially lead to unnecessary surgical intervention.  相似文献   
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