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   27521篇
  免费   2144篇
  国内免费   109篇
耳鼻咽喉   366篇
儿科学   696篇
妇产科学   525篇
基础医学   4036篇
口腔科学   489篇
临床医学   2753篇
内科学   6624篇
皮肤病学   326篇
神经病学   2559篇
特种医学   869篇
外科学   4201篇
综合类   322篇
一般理论   16篇
预防医学   2125篇
眼科学   627篇
药学   1514篇
中国医学   47篇
肿瘤学   1679篇
  2023年   212篇
  2022年   432篇
  2021年   945篇
  2020年   490篇
  2019年   766篇
  2018年   913篇
  2017年   581篇
  2016年   609篇
  2015年   778篇
  2014年   1031篇
  2013年   1325篇
  2012年   1981篇
  2011年   1989篇
  2010年   1102篇
  2009年   959篇
  2008年   1674篇
  2007年   1659篇
  2006年   1627篇
  2005年   1584篇
  2004年   1456篇
  2003年   1317篇
  2002年   1301篇
  2001年   206篇
  2000年   185篇
  1999年   247篇
  1998年   267篇
  1997年   223篇
  1996年   182篇
  1995年   175篇
  1994年   158篇
  1993年   131篇
  1992年   130篇
  1991年   124篇
  1990年   145篇
  1989年   115篇
  1988年   132篇
  1987年   132篇
  1986年   94篇
  1985年   115篇
  1984年   117篇
  1983年   109篇
  1982年   143篇
  1981年   129篇
  1980年   167篇
  1979年   81篇
  1978年   91篇
  1977年   82篇
  1976年   84篇
  1974年   73篇
  1973年   67篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Laparoscopic Cholecystectomy for Acute Cholecystitis: Prospective Trial   总被引:23,自引:0,他引:23  
p < 0.00001) and for hydrops (28.5%) and empyema of the gallbladder (28.5%) ( p = 0.004). The difference in conversion between the group with acute necrotizing (gangrenous) cholecystitis and the two groups with hydrops and empyema of the gallbladder was not statistically significant ( p = 0.07). The complication rates of acute cholecystitis, hydrops, empyema of the gallbladder, and gangrenous cholecystitis were 9.0%, 9.5%, 14.0%, and 20.0%, respectively ( p = NS). Patients with an operative delay of 96 hours or less from the onset of acute cholecystitis had a conversion rate of 23%, whereas a delay of more than 96 hours was associated with a conversion rate of 47% ( p = 0.022). The complication rate was 8.5% in the laparoscopic group and 27% in the converted group ( p = 0.013). Patients over 65 years of age, with a history of biliary disease, a nonpalpable gallbladder, WBC count over 13,000/cc, and acute gangrenous cholecystitis were independently associated with a high LC conversion rate; male patients, finding large bile stones, serum bilirubin over 0.8 mg/dl, and WBC count over 13,000/cc were independently associated with a high complication rate following laparoscopic surgery with or without conversion. Generally, LC can be performed safely for acute cholecystitis, with acceptably low conversion and complication rates. Different forms of cholecystitis carry various conversion and complication rates in selected cases. LC for acute cholecystitis should be performed within 96 hours of the onset of disease. Predictors of conversion and complications may be helpful when planning the laparoscopic approach to acute cholecystitis.   相似文献   
52.
This case report illustrates atypical magnetic resonance (MR) imaging findings in a liver hemangioma mimicking a malignant lesion—lower signal intensity than cerebrospinal fluid on T2-weighted spin-echo images and lack of early enhancement on dynamic contrast material—enhanced gradient-echo images. Pathologic analysis demonstrated nearly total replacement of the vascular cavities by dense fibrous tissue. In this rare, sclerosed form, this lesion could not be defined as a hemangioma with MR imaging.  相似文献   
53.
In this report, we give details of two families in which fixed subaortic stenosis was found in more than one member. It is rare for this entity to show familial incidence.  相似文献   
54.
Discrimination of well-differentiated pulmonary adenocarcinoma from reactive bronchioloalveolar epithelium can be difficult on routine histology, especially with small biopsies. Ancillary studies to help in this distinction are desirable. p63, a p53-homologous nuclear protein, is a marker of reserve cells of the bronchus and terminal lobular unit. In this study, 33 cases of adenocarcinoma (20 open lung and 13 transbronchial/percutaneous biopsies) and 43 cases of benign lungs with fibrosis and metaplasia (22 open lung and 21 transbronchial/percutaneous biopsies) were studied for nuclear p63 expression by immunohistochemistry (Dako, Carpinteria, CA, USA). Five additional cases each of atypical adenomatous hyperplasia and adenosquamous carcinoma and three cases of squamous carcinoma (all open lung biopsies) were also stained. The diagnostic categories of benign lung conditions were usual interstitial pneumonia, parenchymal scar, cryptogenic organizing pneumonia and diffuse alveolar damage. In neoplastic cases, p63 positivity was calculated as percentage of all tumor cells examined. In areas of normal lung, p63 decorated the reserve cells of large and small airways and occasional cells of the distal lobular unit. In fibrotic reactive processes, an interrupted but distinct pattern of nuclear staining was present in all cases, with staining of basal cells of the airways as well as bronchiolar- and squamous-metaplastic epithelium (43/43, 100%). p63 immunoreactivity was less uniform in areas of acute lung injury within these cases. One adenocarcinoma and two cases of atypical adenomatous hyperplasia showed strong immunoreactivity (>80%), while three adenocarcinomas highlighted only rare tumor nuclei (<5% of tumor cells). Morphologic areas where p63 immunostaining was not helpful included the junction of normal lung and lepidic growth of adenocarcinoma, and retrograde spread of adenocarcinoma into small airways. Our results highlight the differential expression of p63 across various bronchioloalveolar lesions. Moreover, p63 may be helpful in distinguishing reactive from neoplastic glandular proliferations in the lung.  相似文献   
55.
The combination of insulin-like growth factor-I and platelet-derived growth factor-BB has previously been shown to stimulate healing of soft tissue wounds and the formation of bone and ligament around teeth. The purpose of the present study was to evaluate the effects of platelet-derived growth factor-BB and insulin-like growth factor-I individually and in combination on the healing of osseous wounds. Four standardized cortical wounds were created in each tibia of 11 adult Yucatan miniature pigs. The wounds in one tibia per animal were treated with either purified recombinant human insulin-like growth factor-I, platelet-derived growth factor-BB, or both in a methylcellulose gel. The wounds in each contralateral tibia received placebo gel alone. Coded serial sections of each wound were evaluated by computer-aided histomorphometry 21 days after surgery. The area and perimeter of the newly formed mineralized callus, the thickness of the total callus, and the percentage of mineralized tissue within the callus were significantly increased compared with the values of matched controls only in wounds treated with a combination of insulin-like growth factor-I and platelet-derived growth factor-BB. No significant differences in the measured parameters of callus formation were found in wounds treated with either insulin-like growth factor-I or platelet-derived growth factor-BB alone. Cartilage was present only in sites treated with insulin-like growth factor-I alone. These results suggest that the combination of platelet-derived growth factor-BB and insulin-like growth factor-I stimulates bone formation in wounds in long bones of adult animals and that these growth factors act via different pathways during the repair process.  相似文献   
56.
57.
In a patient with clinical manifestations suggestive of brain malformation, CT showed lissencephaly with absent opercularization. The child had seizures but not a typical EEG of hypsarhythmia. MRI confirmed the diagnosis and showed heterotopic grey matter and abnormal basal ganglia. High grey-white matter contrast and the possibility of imaging the brain in sagittal, coronal and transverse planes make MRI the methode of choice for the evaluation of lissencephaly and other brain malformations.  相似文献   
58.
59.
We report a case of massive cerebrospinal fluid (CSF) leakage where the tracer injected intra-thecally for radionuclide cisternography was later visualized in the bowel as well as the nasopharynx. We discuss the potential implications of this finding in patients with CSF leaks. A brief review of the diagnosis of CSF leaks is included.  相似文献   
60.
It is well established that visual display unit (VDU) operators complain of visual fatigue and visual stress during after-work hours. The present study was divided into two parts. In the first part, standard eye examinations were performed on a group of VDU workers (n = 32) and a control group (n = 15); those subjects who were found to have correct vision (n = 16 and 13, respectively) participated in the second part. The eye examinations revealed that on the average, the VDU workers suffered more than twice as many visual impairments as the controls. In those with correct vision, the near point of accommodation was measured at the beginning of the workday at the start of the week, and at the end of the workday, four days later. In the VDU group, the decrease in accommodation was uniformally distributed between zero and 1.0 diopter, whereas among the non-VDU workers, 77% of the decrease was between zero and 0.25 diopter. The dynamic range of accommodation in the VDU workers on the second examination was smaller than on the first. We conclude that some of the visual stress and visual fatigue that developed at work hindered visual activities after work.  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