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   305567篇
  免费   21079篇
  国内免费   10728篇
耳鼻咽喉   4841篇
儿科学   8546篇
妇产科学   4646篇
基础医学   26507篇
口腔科学   7468篇
临床医学   32552篇
内科学   50120篇
皮肤病学   4956篇
神经病学   11019篇
特种医学   16000篇
外国民族医学   137篇
外科学   46127篇
综合类   34990篇
现状与发展   47篇
预防医学   16326篇
眼科学   4809篇
药学   27949篇
  93篇
中国医学   5550篇
肿瘤学   34691篇
  2023年   3099篇
  2022年   5500篇
  2021年   12159篇
  2020年   8158篇
  2019年   13840篇
  2018年   8405篇
  2017年   8022篇
  2016年   10367篇
  2015年   13701篇
  2014年   23484篇
  2013年   20504篇
  2012年   24068篇
  2011年   21334篇
  2010年   19016篇
  2009年   18527篇
  2008年   17348篇
  2007年   17598篇
  2006年   15320篇
  2005年   11113篇
  2004年   6767篇
  2003年   5950篇
  2002年   4893篇
  2001年   4301篇
  2000年   3741篇
  1999年   2654篇
  1998年   2816篇
  1997年   2535篇
  1996年   2217篇
  1995年   2222篇
  1994年   2099篇
  1993年   1542篇
  1992年   1690篇
  1991年   1494篇
  1990年   1458篇
  1989年   1370篇
  1988年   1290篇
  1987年   1099篇
  1986年   906篇
  1985年   1832篇
  1984年   1938篇
  1983年   1401篇
  1982年   1505篇
  1981年   1469篇
  1980年   1278篇
  1979年   1085篇
  1978年   829篇
  1977年   811篇
  1976年   713篇
  1975年   440篇
  1974年   456篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
BackgroundRepairing crowns with defective margins is minimally invasive and cost-effective compared with replacement. The authors’ objectives were to examine the survival trajectory of crown margin repairs and to determine the factors associated with survival.MethodsRecords of adult patients from January 2008 through August 2019 were reviewed for crown margin repairs completed at University of Iowa College of Dentistry. A total of 1,002 crown margin repairs were found. Each repair was followed through the end of study in 2019 or until an event (for example, additional repair, endodontic treatment, crown replacement, or extraction). A Cox proportional hazards model was used to study the relationship between selected covariates and time to event.ResultsDuring the follow-up period, 32.8% of the repairs needed reintervention. In the final model, repair material was the only significant covariate. No difference was found between the survival of repairs done with resin-modified glass ionomer and amalgam. However, the repairs done with resin-based composite and conventional glass ionomer were more likely (1.5 times: 95% CI, 1.02 to 2.10 times; and 2 times: 95% CI, 1.40 to 2.73 times, respectively) to need reintervention than were those done with amalgam.ConclusionsMedian survival time of crown margin repairs was 5.1 years (95% CI, 4.48 to 5.72 years). Median survival times for amalgam, resin-modified glass ionomer, resin-based composite, and glass ionomer repair materials were 5.7 years (95% CI, 4.80 to 6.25 years), 5.3 years (95% CI, 4.73 to 6.34 years), 3.2 years (95% CI, 2.51 to 6.19 years), and 3.0 years (95% CI, 2.53 to 3.62 years), respectively.Practical ImplicationsWhen considering crown margin repairs, resin-modified glass ionomer or amalgam is preferable to resin-based composite or glass ionomer.  相似文献   
72.
Adenoid cystic carcinoma (AdCC) is a salivary gland-type of cancer that may also occur in the breast. Breast AdCC shows the same morphological spectrum as is observed in salivary glands, with recognition of individual subtypes that may differ in their clinical behaviour. AdCC classic variant (C-AdCC) is a slowly growing tumour, with a low rate of axillary node and distant metastases. Local recurrences may develop as a consequence of incomplete surgical excision. C-AdCC should be differentiated from the solid-basaloid variant of AdCC (SB-AdCC) that is characterized by nuclear atypia, frequent mitotic figures and necrosis, in addition to the solid architecture. SB-AdCC is a more aggressive tumour, with higher rates of axillary node and distant metastases. AdCC may also co-exist with more aggressive types of carcinoma including metaplastic and neuroendocrine carcinoma, referred to as AdCC with high grade transformation (HG-AdCC). This paper reviews the key diagnostic criteria of the different subtypes of breast AdCC with emphasis on differential diagnosis and prognostic parameters.  相似文献   
73.
Patients undergoing sentinel node biopsy (SLNB) for early oral squamous cell carcinoma (OSCC) who harbour occult metastases (pN+ve) may be at greater risk of mortality due to prolonged overall treatment times than those identified as pN+ve on elective neck dissection (ELND). A retrospective comparative survival analysis was therefore undertaken to test this hypothesis. Patients were identified from the South Glasgow multidisciplinary team (MDT) database. Group 1 comprised 38 patients identified as pN+ve, or who were false negative, on sentinel lymph node biopsy (SLNB). Group 2 comprised 146 patients staged pN+ve on ELND. The groups were compared with the Kaplan Meier method and Cox proportional hazards model. In addition, a matched-pair analysis was performed. A unique and specifically designed algorithm was deployed to optimise the pairings. No difference in disease-specific or overall survival was found between the groups. Patients undergoing SLNB as the initial neck staging modality in early OSCC and are identified as pN+ve do not appear to be at a survival disadvantage compared with those staged with ELND.  相似文献   
74.
Anaplastic thyroid carcinoma (ATC) is an aggressive thyroid malignancy with high mortality rate. This malignancy arises in thyroid follicular cells either denovo or with an associated differentiated thyroid carcinoma component. Clinically, it usually presents as a rapidly enlarging mass, pain and locally compressive symptoms. Histopathologic variability and heterogeneity often pose diagnostic challenges, especially in scant and paucicellular specimens. This article describes the clinical, histopathologic and molecular features of ATC and also addresses the associated diagnostic limitations and challenges.  相似文献   
75.
76.
The adrenal cortex gives rise to a biologically heterogenous group of neoplasms, each with a distinct morphology, antigen expression and molecular profile. Adrenal cortical adenomas have excellent prognosis and are usually cured by surgical resection alone, while adrenal cortical carcinomas are very aggressive tumors with a poor prognosis regardless of therapy. These tumors are rare and often challenging for a pathologist to diagnose, as significant overlap exists between benign and malignant lesions in some cases. In this review, we attempt to summarize most important histologic and clinical features of adrenal cortical adenomas and carcinomas, clarify the use of different grading systems, the use of special stains and the differential diagnosis for practicing pathologists. Most relevant hereditary syndromes associated with adrenal cortical tumors are listed. Updates in molecular alterations in adrenal cortical neoplasms and hyperplastic diseases as well as their clinical significance and potential therapeutic implications are also discussed.  相似文献   
77.
ObjectiveTo study the clinical features and identify unique renal neoplasia subtypes and their prognostic implications in individuals with tuberous sclerosis complex (TSC).Patients and MethodsThe Mayo Clinic nephrectomy registry included 37 patients with TSC diagnosed between 1970 and 2018. Four additional patients were identified from the pathology consultation and autopsy files. All available renal tumors were further characterized using immunohistochemistry and fluorescence in situ hybridization. Clinicopathologic features and follow-up were obtained from the medical record. The American Association for Cancer Research Project GENIE registry was accessed using cBioPortal for molecular profiling of angiomyolipoma (AML).ResultsA total of 276 renal tumors from 41 patients were analyzed. Renal tumors were classified into 9 distinct morphological subtypes, with AML predominating (238 [86%]). Interestingly, all these tumors acted in a benign fashion except one renal cell carcinoma with clear cells and fibromyomatous stroma and one epithelioid AML that metastasized. Molecular profiling studies revealed that epithelioid AMLs were enriched for alterations of TP53, RB1, and ATRX. Eight patients died of direct complications of TSC, including 3 of end-stage renal disease. To date, none have died of a renal epithelial neoplasm.ConclusionThe identification of unique renal neoplasia subtypes may provide important clues to establish a diagnosis of TSC, and in the somatic setting, this finding has important implications for accurate prognostication. These tumors tend to be indolent, and only 2 of 276 tumors in our study exhibited metastatic behavior. Our results support multidisciplinary management with a focus on preservation of renal function.  相似文献   
78.
The coronavirus disease 2019 (COVID-19) pandemic has rapidly created widespread impacts on global health and the economy. Data suggest that women are less susceptible to severe illness. However, sex-disaggregated data are incomplete, leaving room for misinterpretation, and focusing only on biologic sex underestimates the gendered impact of the pandemic on women. This narrative review summarizes what is known about gender disparities during the COVID-19 pandemic and the economic, domestic, and health burdens along with overlapping vulnerabilities related to the pandemic. In addition, this review outlines recommended strategies that advocacy groups, community leaders, and policymakers should implement to mitigate the widening gender disparities related to COVID-19.  相似文献   
79.
To investigate factors that affect and also decrease the duration for recurrences and secondary tumors in cSCC.A retrospective study was conducted for all patients who were treated for a cSCC of the head and neck between 2009 and 2016. Anamnestic as well as epidemiological and histological data were noted and correlated with the occurrence of recurrences and secondary cancers. The duration between surgery and these events was used to determine if histological factors accelerate their occurrence.The highest risk for recurrences was seen in patients with previous skin cancers (RR 3.23). Histological ulceration (p = 0.003) and grading (p = 0.031) of the tumor were found as significant factors accelerating the time to relapse. Surrounding chronic precancerotic lesions (p < 0.001) and poor tumor grading (p = 0.035) were found as significant factors accelerating the time until a secondary cSCC was observed.Known risk factors increase not only the risk for a cSCC but also for recurrences. Specific histologic findings can help to adjust follow-up intervals to identify recurrences and secondary tumors at an early stage as these were shown to decrease the duration for a further event.  相似文献   
80.
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