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   24513篇
  免费   1753篇
  国内免费   80篇
耳鼻咽喉   267篇
儿科学   562篇
妇产科学   496篇
基础医学   3385篇
口腔科学   743篇
临床医学   2825篇
内科学   4903篇
皮肤病学   208篇
神经病学   2641篇
特种医学   952篇
外国民族医学   2篇
外科学   2976篇
综合类   340篇
一般理论   24篇
预防医学   1951篇
眼科学   486篇
药学   2010篇
中国医学   20篇
肿瘤学   1555篇
  2023年   98篇
  2022年   148篇
  2021年   375篇
  2020年   242篇
  2019年   331篇
  2018年   376篇
  2017年   350篇
  2016年   403篇
  2015年   496篇
  2014年   693篇
  2013年   1045篇
  2012年   1594篇
  2011年   1727篇
  2010年   1012篇
  2009年   875篇
  2008年   1657篇
  2007年   1608篇
  2006年   1604篇
  2005年   1699篇
  2004年   1555篇
  2003年   1527篇
  2002年   1436篇
  2001年   294篇
  2000年   225篇
  1999年   309篇
  1998年   372篇
  1997年   280篇
  1996年   268篇
  1995年   254篇
  1994年   208篇
  1993年   182篇
  1992年   172篇
  1991年   155篇
  1990年   144篇
  1989年   144篇
  1988年   140篇
  1987年   133篇
  1986年   139篇
  1985年   146篇
  1984年   160篇
  1983年   157篇
  1982年   199篇
  1981年   164篇
  1980年   185篇
  1979年   99篇
  1978年   119篇
  1977年   110篇
  1976年   84篇
  1975年   89篇
  1974年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
BACKGROUND: Cutaneous cancers exhibit a much higher incidence in patients with chronic lymphocytic leukemia than in nonleukemic patients. Squamous and basal cell carcinomas also exhibit greater subclinical tumor extension in patients with chronic lymphocytic leukemia. OBJECTIVE: The purpose of this study was to estimate and compare the recurrence rates of squamous cell carcinoma after Mohs' surgery in patients with chronic lymphocytic leukemia compared with those in controls and to evaluate differences among squamous cell carcinoma size and histologic grade. METHODS: We retrospectively assessed the clinical histories, postoperative notes, and surgical photographs of patients with chronic lymphocytic leukemia and controls matched (2:1) for age, sex, and surgical year. Both patients and controls underwent Mohs' surgery for squamous cell carcinoma of the head and neck at the Mayo Clinic between March 1988 and April 1999. RESULTS: Twenty-eight patients who underwent Mohs' surgery for 57 squamous cell carcinomas had 7 recurrences. The cumulative incidence of recurrence on a per-tumor basis was 4.3% at 1 year, 14.8% at 3 years, and 19.0% at 5 years. Squamous cell carcinoma was seven times more likely to recur in patients with chronic lymphocytic leukemia than in controls (p = .003). The distribution of tumor histologic grade was not significantly different between patients and controls (p = .39). Maximum preoperative tumor diameters were clinically similar between patients and controls (median 15 mm vs 14 mm; p = .04). CONCLUSION: The recurrence rates of squamous cell carcinoma were significantly higher in patients with chronic lymphocytic leukemia. Squamous cell carcinomas in patients with chronic lymphocytic leukemia did not exhibit a significant difference in histologic grade or clinical difference in preoperative tumor size. Close surveillance for squamous cell carcinoma recurrence is warranted in patients with chronic lymphocytic leukemia.  相似文献   
84.
Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury. Tumor necrosis factor-alpha (TNFalpha) is protective in LPS-induced preconditioning yet exacerbates neuronal injury in ischemia. Here, we define dual roles of TNFalpha in LPS-induced ischemic tolerance in a murine model of stroke and in primary neuronal cultures in vitro, and show that the cytotoxic effects of TNFalpha are attenuated by LPS preconditioning. We show that LPS preconditioning significantly increases circulating levels of TNFalpha before middle cerebral artery occlusion in mice and show that TNFalpha is required to establish subsequent neuroprotection against ischemia, as mice lacking TNFalpha are not protected from ischemic injury by LPS preconditioning. After stroke, LPS preconditioned mice have a significant reduction in the levels of TNFalpha (approximately threefold) and the proximal TNFalpha signaling molecules, neuronal TNF-receptor 1 (TNFR1), and TNFR-associated death domain (TRADD). Soluble TNFR1 (s-TNFR1) levels were significantly increased after stroke in LPS-preconditioned mice (approximately 2.5-fold), which may neutralize the effect of TNFalpha and reduce TNFalpha-mediated injury in ischemia. Importantly, LPS-preconditioned mice show marked resistance to brain injury caused by intracerebral administration of exogenous TNFalpha after stroke. We establish an in vitro model of LPS preconditioning in primary cortical neuronal cultures and show that LPS preconditioning causes significant protection against injurious TNFalpha in the setting of ischemia. Our studies suggest that TNFalpha is a twin-edged sword in the setting of stroke: TNFalpha upregulation is needed to establish LPS-induced tolerance before ischemia, whereas suppression of TNFalpha signaling during ischemia confers neuroprotection after LPS preconditioning.  相似文献   
85.
Bronchiolitis obliterans syndrome (BOS) is a major cause of lung allograft dysfunction. Although previous studies have identified mild to severe rejection (grade>or=A2) as a risk factor for BOS, the role of minimal rejection (grade A1) remains unclear. To determine if A1 rejection by itself is a risk factor for BOS, we performed a retrospective cohort study on 228 adult lung transplant recipients over a 7-year period. Cohorts were defined by their most severe rejection episode (none, A1 only, and >or=A2) and analyzed for the subsequent development and progression of BOS using univariate and multivariate time-dependent Cox regression analysis. In the univariate model, the occurrence of isolated minimal rejection was a risk factor for all stages of BOS. Similarly, multivariate models that included HLA mismatch, cytomegalovirus pneumonitis, community acquired viral infection, underlying disease and type of transplant demonstrated that A1 rejection was a distinct risk factor for BOS. Furthermore, the associated risk with A1 rejection was slightly greater than the risk from >or=A2 and treatment of A1 rejection decreased the risk for subsequent BOS stage 1. We conclude that minimal rejection is associated with an increased risk for BOS development and progression that is comparable to A2 rejection.  相似文献   
86.
87.
88.
89.
90.
Infective endocarditis is an infrequent but serious complication in heart transplant recipients. We report successful treatment for this serious complication.  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