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   6073篇
  免费   348篇
  国内免费   24篇
耳鼻咽喉   38篇
儿科学   218篇
妇产科学   159篇
基础医学   995篇
口腔科学   77篇
临床医学   409篇
内科学   1085篇
皮肤病学   188篇
神经病学   634篇
特种医学   186篇
外国民族医学   5篇
外科学   846篇
综合类   38篇
预防医学   276篇
眼科学   179篇
药学   438篇
中国医学   2篇
肿瘤学   672篇
  2023年   36篇
  2022年   73篇
  2021年   86篇
  2020年   65篇
  2019年   78篇
  2018年   100篇
  2017年   77篇
  2016年   111篇
  2015年   127篇
  2014年   165篇
  2013年   204篇
  2012年   286篇
  2011年   313篇
  2010年   158篇
  2009年   172篇
  2008年   320篇
  2007年   261篇
  2006年   287篇
  2005年   300篇
  2004年   256篇
  2003年   258篇
  2002年   220篇
  2001年   228篇
  2000年   209篇
  1999年   182篇
  1998年   79篇
  1997年   68篇
  1996年   57篇
  1995年   34篇
  1994年   50篇
  1993年   36篇
  1992年   103篇
  1991年   89篇
  1990年   84篇
  1989年   77篇
  1988年   90篇
  1987年   82篇
  1986年   71篇
  1985年   56篇
  1984年   45篇
  1983年   39篇
  1982年   32篇
  1979年   52篇
  1978年   31篇
  1975年   31篇
  1974年   41篇
  1973年   36篇
  1972年   33篇
  1971年   32篇
  1966年   46篇
排序方式: 共有6445条查询结果,搜索用时 15 毫秒
31.
The correlation between the noradrenalin (NA), dopamine (DA) and serotonin (5-HT) contents of cerebrospinal fluid (CSF) samples obtained from the cerebro-ventricular space and the systolic and diastolic blood pressure (BP) of two patients with cerebral haemorrhage were investigated. Significant correlation was found between CSF NA, CSF DA level and systolic BP in case I. There was no correlation between CSF catecholamine levels and diastolic BP and between serotonin level and BP. Significant correlation was observed in case II between CSF DA level and diastolic BP. There was no correlation between CSF serotonin level and BP. These results suggest that CSF catecholamines might play some role in the regulation of BP.  相似文献   
32.
33.
Cardiac myxomas are the most frequent cardiac tumors and cause for significant morbidity and mortality. Recent evidence indicates that cardiac myxomas are, in fact, neoplasms rather than organized thrombi. Cardiac myxomas may present as solitary lesions or in association with the Carney complex. Carney complex has been linked to chromosome 2p16 and the PRKAR1A gene at 17q22-24. In this study, we analyzed sporadic cardiac myxomas to evaluate whether the genetic alterations seen in Carney complex are present in non Carney complex associated cardiac myxomas as well. We analyzed microdissected material from 13 patients with cardiac myxomas for the markers PRKAR1 9CA, D2S2153, D2S2251 and D2S123. None of the cases demonstrated loss of heterozygosity or definite band changes suggestive of microsatellite instability for any of the markers used. We conclude that sporadic cardiac myxomas are genetically not related to Carney complex and most likely do not represent an incomplete form of Carney complex.  相似文献   
34.
Forty-one patients with adrenal cortical tumors were evaluated retrospectively for the presence of histologic and non-histologic features associated with malignant behavior. The patients who survived operation were followed at least five years. The association of these features with subsequent metastasis was examined by both parametric and nonparametric statistical methods. Twelve criteria were statistically significant in predicting subsequent metastasis. The most significant of these were: clinical evidence of weight loss, broad fibrous bands traversing the tumor, a diffuse growth pattern, vascular invasion, tumor cell necrosis, and tumor mass. The tendency toward metastasis for each tumor was expressed in indices that correlated well with diagnoses made by conventional histologic means, but were more accurate in predicting subsequent clinical behavior than nonquantitative methods of evaluation.  相似文献   
35.
36.
Urothelial carcinoma of the renal pelvis and ureter may develop as a manifestation of hereditary nonpolyposis colorectal cancer syndrome (HNPCC), a disorder characterized by mutation or inactivation of a number of DNA mismatch repair genes and detectable as microsatellite instability (MSI). Some urothelial carcinomas display areas of endophytic, or inverted, growth. In this study, urothelial cancers of the upper urinary tract (n = 132) from patients treated at 2 tertiary care centers were studied to identify an association between growth pattern and MSI. Thirty-five neoplasms were microsatellite unstable (26.5%), and MSI was more frequent in papillary lesions than in sessile urothelial cancers (P = .033). The amount of inverted growth was estimated as a percentage of the total tumor. The interobserver and intraobserver concordance in recognizing inverted growth was good, and 65.7% of microsatellite-unstable tumors exhibited at least 20% of an inverted growth component, compared with only 17.5% of microsatellite-stable tumors (P < .0001). In this series, inverted growth predicted MSI with a sensitivity and specificity of .82. Inverted growth in urothelial carcinomas of the upper urinary tract may serve as a marker lesion for MSI and may help identify patients who should be offered testing for HNPCC.  相似文献   
37.
38.
The Epstein-Barr virus (EBV) is consistently associated with undifferentiated nasopharyngeal carcinoma (NPC). There is, however, conflicting evidence as to whether squamous cell NPCs are also EBV-associated. Moreover, it has been proposed that other epithelial tumours, particularly thymomas and thymic carcinomas, should be included in the group of EBV-associated neoplasias. However, since the viral DNA in these studies was demonstrated only in extracted DNA, the cellular origin of the viral DNA is uncertain. We have therefore investigated 152 epithelial tumours from various sites for the presence of EBV-DNA by in situ hybridization with 35S-labelled probes. Sixty-eight of 77 undifferentiated NPCs showed an EBV-specific autoradiographic signal, thus confirming the strong association of this tumour type with EBV even in geographical areas where undifferentiated NPC is not endemic. None of eight squamous cell NPCs showed an EBV-specific signal. All of 15 carcinomas with a similar morphology to undifferentiated NPC but from different anatomic sites (thymus, tonsil, breast) were EBV-negative as were 9 thymomas, 26 squamous cell carcinomas of the palatine tonsil, and 14 cervical carcinomas. Our results therefore suggest a unique association of EBV with undifferentiated NPC and support concepts assigning different biological properties to undifferentiated NPC as compared with squamous cell NPC.  相似文献   
39.
Staphylococcus aureus isolates (n = 70) from 65 patients (36 canine, 18 equine, 7 bovine, 2 avian, and 2 feline) at seven veterinary teaching hospitals in the United States were studied. The majority of patients (83%) with an S. aureus infection were canine and equine, but this may have reflected a sample bias based on clinic case loads and diagnostic lab submissions at the participating institutions. Fourteen percent of patients with an S. aureus infection were infected with a methicillin-resistant S. aureus (MRSA) isolate. Six of seven institutions had at least one MRSA infection during the study. Pulsed-field gel electrophoresis on 63 of the 70 isolates yielded 58 unique strains of S. aureus. None of the strain types of the MRSA isolates matched each other or the type of any other S. aureus isolate. The proportions of patients infected with an MRSA isolate were not significantly different between institutions or animal species (P > or = 0.222). Methicillin-resistant S. aureus isolates in this study seemed to be community acquired rather than hospital acquired.  相似文献   
40.
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