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   27571篇
  免费   1335篇
  国内免费   52篇
耳鼻咽喉   385篇
儿科学   1122篇
妇产科学   511篇
基础医学   3239篇
口腔科学   536篇
临床医学   1752篇
内科学   7403篇
皮肤病学   883篇
神经病学   2378篇
特种医学   812篇
外科学   4102篇
综合类   113篇
一般理论   4篇
预防医学   2396篇
眼科学   490篇
药学   1403篇
中国医学   101篇
肿瘤学   1328篇
  2023年   156篇
  2022年   98篇
  2021年   591篇
  2020年   244篇
  2019年   645篇
  2018年   1082篇
  2017年   594篇
  2016年   533篇
  2015年   564篇
  2014年   647篇
  2013年   1049篇
  2012年   1843篇
  2011年   2018篇
  2010年   1066篇
  2009年   804篇
  2008年   1671篇
  2007年   1754篇
  2006年   1702篇
  2005年   1676篇
  2004年   1605篇
  2003年   1437篇
  2002年   1422篇
  2001年   1026篇
  2000年   1257篇
  1999年   895篇
  1998年   155篇
  1997年   77篇
  1996年   97篇
  1995年   56篇
  1994年   51篇
  1993年   48篇
  1992年   319篇
  1991年   241篇
  1990年   248篇
  1989年   173篇
  1988年   127篇
  1987年   123篇
  1986年   125篇
  1985年   97篇
  1984年   70篇
  1983年   50篇
  1979年   32篇
  1976年   27篇
  1975年   27篇
  1974年   50篇
  1973年   52篇
  1972年   41篇
  1971年   38篇
  1970年   39篇
  1969年   38篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
91.
The model of biliary tract infection induced in rats given suspension of E. coli into the bile duct is described. To prevent leakage of microorganisms after the administration, a temporary ligation of the bile duct followed. Contemporary groups of sham-operated and control rats (given saline by intrabiliary injection) were compared to assess the significance of the changes. The effect of biliary infection was concentration dependent. If 0.1 ml of the concentration containing 10(2), 10(3) and 10(6) colony-forming units/ml was injected, the mortality of rats reached 8%, 57% and 65%, respectively within 24 h. Blood and bile cultures from all dead animals grew E. coli. To evaluate the effect of chronic biliary infection, the concentration of 10(2) colony-forming units/ml was used. Serum concentrations of total and conjugated bilirubin, cholesterol and creatinine, activities of S-alanine-aminotransferase, S-aspartate-aminotransferase, alkaline phosphatase, the count of leucocytes in blood, total body weight with weight of the liver were investigated on days 1, 4 and 12 after the treatment. The results showed: an increase in leucocytes (21 +/- 4.2 10(9)/l, p less than 0.02 vs control animals) on day 4, an augmentation of serum cholesterol on day 1, (2.1 +/- 0.9 mmol/l, p less than 0.02 vs control animals), the presence of E. coli in blood on day 1 and its persistence in the bile on days 1, 4 and 12. Except the bile, all of the other symptoms were reversible by day 12.  相似文献   
92.
Maternal group B streptococcal infection is an uncommon entity. Herein we describe a case of a 27-year-old-woman who presented life-threateniing group B streptococcus meningitis with an ectopic cervical pregnancy. No other infectious focus have been found. To our knowledge this is the first time that this association has been reported.  相似文献   
93.
BACKGROUND. Detection and treatment for rejection after transplantation are based on the identification of myocyte damage upon endomyocardial biopsy. Noninvasive detection of such damage is possible with 111In-labeled monoclonal antimyosin antibodies (MAA). Although the presence and degree of MAA uptake parallels the rejection activity detected by biopsy, the relation between the degree of uptake and the occurrence of severe rejection-related complications has not been previously assessed. METHODS AND RESULTS. Two hundred forty-seven MAA studies were performed coinciding with biopsies in 52 patients 1-71 months after transplantation. A heart-to-lung ratio (HLR) was used as a measure of relative MAA uptake, with an HLR of 1.55 discriminating normal from abnormal studies. Of the 247 antimyosin studies, 149 coincided with absent, 38 with mild, and 60 with moderate rejection at biopsy. HLR was 1.68 +/- 0.27, 1.79 +/- 0.22, and 1.91 +/- 0.33 in the three biopsy groups, respectively (p less than 0.0001). Two hundred thirty-eight of 247 antimyosin studies coexisted with absent rejection-related complications; in nine of 247 patients, such complications were detected (five congestive heart failure episodes due to rejection and four episodes of vascular occlusion, which resulted in five deaths), and mean HLR was 1.74 +/- 0.3 and 2.1 +/- 0.16 in the two groups, respectively (p less than 0.0001). No complications were noted in 193 studies of patients with HLR of less than 2.00, whereas in nine of 45 with HRL of 2.00 or greater, complications occurred (p less than 0.0001). None of the 23 patients prospectively followed since surgery who had a gradual decrease in MAA uptake during the first 3 months showed rejection-related complications, whereas persistent uptake was associated with complications in five of nine patients (p less than 0.001). CONCLUSIONS. No rejection-related complications are seen coinciding with HLR of less than 2.00, whereas patients who have complications have an HLR of more than 2.00. The early 3-month pattern of decreasing MAA uptake is associated with a clinical course free of rejection-related complications, whereas a persistent pattern is a signal of the possibility of such complications.  相似文献   
94.
We reviewed 488 twin pregnancies that resulted in the birth of neonates weighing 1000 g or more. Complications were present in 56.7% of all pregnancies; most common were threat of premature labor (17.4%) and preeclampsia (14.5%). Perinatal mortality was 31.8 per thousand. Eighty percent of neonatal deaths in twin pregnancies involved newborns weighing less than 2000 g. Twin pregnancies are high risk pregnancies and benefit from early diagnosis, prevention and treatment of the threat of premature birth.  相似文献   
95.
A comparison was performed between technetium-99m tetrofosmin myocardial perfusion tomography at baseline and after nitrate administration, using a 2-day protocol, and rest-reinjection thallium-201 single-photon emission tomography (SPET) studies in order to assess whether nitrates enhance the detection of viable myocardium with99mTc-tetrofosmin. Fifteen patients with coronary artery disease, previous myocardial infarction and a left ventricular ejection fraction <40% underwent201T1 rest-injection and99mTc-tetrofosmin. baseline-postnitroglycerin (0.4 mg sublingually) SPET studies, within 48 h. Tomograms based on the three spatial planes were divided into 15 segments and regional tracer uptake was quantitatively analysed. Viability was defined as presence of tracer uptake >50% of peak activity on baseline studies or after reversibility. The percentage of peak activity of99mTc-tetrofosmin at baseline correlated with that of 201T1 (r=0.82,P <0.001). On baseline99mTc-tetrofosmin studies, 73 of the 225 segments that were analysed had <50% of peal. activity. Fifteen percent of these segments showed reversibility after nitrate administration, with an increase in99mTc-tetrofosmin uptake from 40%±9% to 57%±9% of peak activity (P=0.003). All reversible segments after nitrate administration had viability criteria on201Tl studies, but 20 segments that were non-viable on99mTc-tetrofosmin. studies were viable on201Tl studies. Using a threshold value of >40% of peak activity, only seven segments remained non-viable on99mTc-tetrofosmin studies. Overall agreement between99mTc-tetrofosmin with nitrates and201Tl-reinjection regarding the presence of myocardial viability was 90%. Detection of myocardial viability with99mTc-tetrofosmin. was enhanced after nitrate administration, correlating with viability criteria observed on thallium studies.  相似文献   
96.
INTRODUCTION: Colon cancer is one of the main causes of cancer death. Diagnosis requires the examination of the entire large bowel by means of radiological or endoscopic techniques. Many patients suspect of colon cancer are referred for colonoscopy but nevertheless this suspicion is not confirmed after endoscopic examination. The objective of this study is the evaluation of the reliability of abdominal ultrasound in the diagnosis of these tumors. MATERIAL AND METHOD: We selected patients suspect of colon cancer referred to the endoscopy unit for a colonoscopy. An abdominal ultrasound was carried out on all patients prior to the endoscopy. Considering the endoscopic examination as a gold standard, the sensibility, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the ultrasonography were evaluated. Likewise, a series of analytical and clinical parameters were evaluated, in an attempt to establish associated factors of a colon cancer. The statistical analysis was carried out by means of the statistical package SPSS 12.0 for Windows. RESULTS: 145 patients were included in the study (56.6% males) with an average 66.72 years of age (22-89). A cancer was diagnosed in 42 cases (28.9%). In the diagnosis of colon cancer, abdominal ultrasound presents a sensitivity of 79.06%, a specificity of 92.15%, a PPV and a NPV of 80.9% and of 91.2%, respectively. Excluding from the analysis lesions of the rectal ampulla, which cannot be adequately evaluated by means of ultrasound, the figures for sensitivity, specificity, PPV and NPV increase to 91.8, 92.1, 80.9 and 96.9% respectively. The univariate analysis showed that an age over 65 years and the presence of microcytosis are associated to a greater risk of colon cancer while after multivariate analysis only the presence of microcytosis resulted to be an independent predictive factor of cancer. CONCLUSIONS: Abdominal ultrasound presents high sensitivity, specificity, PPV and NPV in the diagnosis of colon cancer. The combination of an ultrasonography and a rectoscopy permits us to rule out the presence of a colorectal carcinoma. In patients with microcytosis of 65 years and over, if there is strong clinical suspicion, a negative ultrasound may not be sufficient to rule out a colorectal neoplasia.  相似文献   
97.
98.
OBJECTIVE: Respiratory scleroma (RS) is a progressive, chronic, granulomatous disease caused by Klebsiella rhinoscleromatis. There is only one report of RS association with HLA-DQ3. In this study, molecular association of HLA class II and RS was determined. STUDY DESIGN AND SETTING: Nine RS patients and 163 healthy controls were compared. DQA1, DQB1, and DRB1 loci were typed. RESULTS: Statistical analysis demonstrated association between DQB1*0301 and susceptibility to RS (P(c) = 0.004). Haplotype analysis showed an association of DQA1*03011-DQB1*0301 (P = 1.21E-19) and DRB1*0407-DQA1*03011-DQB1*0301 (P = 0.0002). CONCLUSIONS: Results established that DQA1*03011-DQB1*0301 haplotype is a strong risk factor for development of RS.  相似文献   
99.
100.
Recent experimental studies and one clinical case have suggested that grafting tissue from the adrenal medulla into the brain may ameliorate the signs of Parkinson's disease. We describe the treatment of two young patients (35 and 39 years old) with intractable and incapacitating Parkinson's disease, in whom fragments of the adrenal medulla were autotransplanted to the right caudate nucleus. Clinical improvement was noted in both patients at 15 and 6 days (respectively) after implantation and has continued in both. Rigidity and akinesia had virtually disappeared in the first patient at 10 months after surgery, and his tremor was greatly reduced. A similar degree of improvement was present in the second patient at three months. We conclude that autografting of the adrenal medulla to the right caudate nucleus was associated with a marked improvement in the signs of Parkinson's disease in two patients, but our results are preliminary and further work is necessary to see whether this procedure will be applicable over the long term in other types of patients with Parkinson's disease.  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