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   12031篇
  免费   899篇
  国内免费   39篇
耳鼻咽喉   109篇
儿科学   527篇
妇产科学   343篇
基础医学   1463篇
口腔科学   165篇
临床医学   2316篇
内科学   1878篇
皮肤病学   119篇
神经病学   1092篇
特种医学   279篇
外科学   1163篇
综合类   155篇
一般理论   29篇
预防医学   1452篇
眼科学   224篇
药学   693篇
中国医学   48篇
肿瘤学   914篇
  2023年   65篇
  2022年   44篇
  2021年   244篇
  2020年   158篇
  2019年   220篇
  2018年   250篇
  2017年   246篇
  2016年   259篇
  2015年   270篇
  2014年   380篇
  2013年   537篇
  2012年   849篇
  2011年   904篇
  2010年   488篇
  2009年   447篇
  2008年   766篇
  2007年   835篇
  2006年   778篇
  2005年   776篇
  2004年   805篇
  2003年   719篇
  2002年   662篇
  2001年   236篇
  2000年   204篇
  1999年   188篇
  1998年   138篇
  1997年   92篇
  1996年   99篇
  1995年   87篇
  1994年   76篇
  1993年   65篇
  1992年   105篇
  1991年   95篇
  1990年   64篇
  1989年   81篇
  1988年   59篇
  1987年   83篇
  1986年   61篇
  1985年   60篇
  1984年   49篇
  1983年   55篇
  1982年   47篇
  1981年   38篇
  1980年   40篇
  1979年   31篇
  1978年   38篇
  1977年   25篇
  1976年   30篇
  1975年   24篇
  1974年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
We pooled multiethnic data from four population-based studies and examined associations of menstrual and reproductive characteristics with breast cancer (BC) risk by tumor hormone receptor (HR) status [defined by estrogen receptor (ER) and progesterone receptor (PR)]. We estimated odds ratios and 95% confidence intervals using multivariable logistic regression, stratified by age (<50, ≥50 years) and ethnicity, for 5,186 HR+ (ER+ or PR+) cases, 1,365 HR− (ER− and PR−) cases and 7,480 controls. For HR+ BC, later menarche and earlier menopause were associated with lower risk in non-Hispanic whites (NHWs) and Hispanics, and higher parity and longer breast-feeding were associated with lower risk in Hispanics and Asian Americans, and suggestively in NHWs. Positive associations with later first full-term pregnancy (FTP), longer interval between menarche and first FTP and shorter time since last FTP were limited to younger Hispanics and Asian Americans. Except for nulliparity, reproductive characteristics were not associated with risk in African Americans. For HR− BC, lower risk was associated with later menarche, except in African Americans and older Asian Americans and with longer breast-feeding in Hispanics and Asian Americans only. In younger African Americans, HR− BC risk associated with higher parity (≥3 vs. 1 FTP) was increased fourfold in women who never breast-fed, but not in those with a breast-feeding history, suggesting that breast-feeding may mitigate the adverse effect of higher parity in younger African American women. Further work needs to evaluate why menstrual and reproductive risk factors vary in importance according to age and ethnicity.  相似文献   
5.
6.
The long-held belief that degeneration of the cholinergic basal forebrain was central to Alzheimer's disease (AD) pathogenesis and occurred early in the disease process has been questioned recently. In this regard, changes in some cholinergic basal forebrain (CBF) markers (e.g. the high affinity trkA receptor) but not others (e.g., cortical choline acetyltransferase [ChAT] activity, the number of ChAT and vesicular acetylcholine transporter-immunoreactive neurons) suggest specific phenotypic changes, but not frank neuronal degeneration, early in the disease process. The present study examined the expression of the low affinity p75 neurotrophin receptor (p75(NTR)), an excellent marker of CBF neurons, in postmortem tissue derived from clinically well-characterized individuals who have been classified as having no cognitive impairment (NCI), mild cognitive impairment (MCI), and mild AD. Relative to NCI individuals, a significant and similar reduction in the number of nucleus basalis p75(NTR)-immunoreactive neurons was seen in individuals with MCI (38%) and mild AD (43%). The number of p75(NTR)-immunoreactive nucleus basalis neurons was significantly correlated with performance on the Mini-Mental State Exam, a Global Cognitive Test score, as well as some individual tests of working memory and attention. These data, together with previous reports, support the concept that phenotypic changes, but not frank neuronal degeneration, occur early in cognitive decline. Although there was no difference in p75(NTR) CBF cell reduction between MCI and AD, it remains to be determined whether these findings lend support to the hypothesis that MCI is a prodromal stage of AD.  相似文献   
7.
8.
梁素娥 《现代医院》2007,7(Z2):83-84
目的 保持皮肤清洁,使病人身心舒适;维持病人皮肤完整性,治疗或预防皮肤并发症.方法 ①大小便失禁病人皮肤完整的床上擦浴,bid,排便后及时清洗,用电吹风或红外线照射,保持会阴部、尾骶部皮肤干燥;应用一次性尿垫、阴茎套、留置导尿管等辅助工具接尿;②褥疮护理使用气垫床,翻身防褥疮护理,q2h,对褥疮创面给予换药、湿润烧伤膏外敷,qd;③外阴炎给予达克宁霜或康纳乐霜外涂,tid.结果 入院时皮肤完好的320例病人褥疮发生率为0.5%,皮肤炎发生率为0.85%,尿路感染发生率为1.5%;50例皮肤炎病人全部治愈,86例带入院褥疮治愈率为93%.结论 对大小便失禁的病人实施良好的皮肤护理,可促进病人舒适,维持病人皮肤完整性,治疗和预防皮肤并发症的发生.  相似文献   
9.
Aims: Studies conducted in first‐episode psychosis (FEP) samples avoid many biases. However, very few studies are based on epidemiological cohorts treated in specialized FEP services. The aim of this file audit study was to examine premorbid and baseline characteristics of a large epidemiological sample of FEP. Methods: File audit study of all patients admitted to the Early Psychosis Prevention and Intervention Centre between 1998 and 2000 using a specialized questionnaire. Results: There were 661 patient files included in the study. Premorbid evaluation revealed high rates of substance use disorder (74.1%), history of psychiatric disorder (47.5%), past traumatic events (82.7%) suicide attempts (14.3%) and family history of psychiatric illness (55.6%). Baseline characteristics revealed high intensity of illness (mean CGI 5.5), high prevalence of lack of insight (62%) and high rate of comorbidity (70%). Conclusion: High rates of traumatic events or episodes of mental illness before treatment for FEP must be considered when designing treatment approaches because a too narrow focus on positive psychotic symptoms will inevitably lead to incomplete treatment. Additionally, early intervention programmes need sufficient range of resources to address the multiple challenges presented by FEP patients such as high severity of illness, comorbidities and functional impairment. Finally, observation of an important degree of functional impairment despite short duration of untreated psychosis suggests that while early detection of FEP is a necessary step in early intervention, it may not be sufficient to improve functional recovery in psychosis and that efforts aimed at identifying people during the prodromal phase of psychotic disorders should be pursued.  相似文献   
10.
Tumor metastasis to the pancreas is a rare but recognized cause of acute pancreatitis. Autopsy series have reported a 24-40% of pancreatic involvement in small cell lung cancer. However, only a very few cases of tumor-induced acute pancreatitis have been described. Budd-Chiari syndrome complicating lung cancer is a rarely reported condition. We report a 68-year-old woman with extensive small cell lung cancer with the unusual initial presentation of both acute pancreatitis and acute Budd-Chiari syndrome. This patient suffered from progressive epigastralgia for 3 weeks. Severe epigastralgia with radiation to back and progressive jaundice developed 2 days prior to admission. After admission, the liver enlarged rapidly and the ascites increased markedly. Chest roentgenogram showed a mass lesion over the left lower lung field. Poorly differentiated carcinoma cells were found in ascites and bone marrow. The patient died on the ninth day of hospitalization before chemotherapy was initiated. Prompt diagnosis of extensive-stage small cell lung cancer may allow early chemotherapy treatment which favorably influences recovery when the pancreatitis is mild. Although prolonged survival might have been expected had this patient recovered from pancreatitis and received chemotherapy, diagnosis was delayed due to difficulty in immunohistochemical diagnosis of the tumor and the unusual clinical presentation. The use of stains employing antibodies against neurofilament and neuron-specific enolase cell antigens is important for early diagnosis of poorly differentiated metastatic tumor cells.  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