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   2534篇
  免费   188篇
  国内免费   8篇
耳鼻咽喉   16篇
儿科学   154篇
妇产科学   87篇
基础医学   335篇
口腔科学   36篇
临床医学   228篇
内科学   686篇
皮肤病学   39篇
神经病学   131篇
特种医学   71篇
外科学   213篇
综合类   40篇
预防医学   215篇
眼科学   185篇
药学   136篇
中国医学   10篇
肿瘤学   148篇
  2023年   6篇
  2022年   35篇
  2021年   61篇
  2020年   34篇
  2019年   49篇
  2018年   60篇
  2017年   42篇
  2016年   60篇
  2015年   62篇
  2014年   98篇
  2013年   108篇
  2012年   189篇
  2011年   210篇
  2010年   123篇
  2009年   104篇
  2008年   165篇
  2007年   159篇
  2006年   133篇
  2005年   135篇
  2004年   139篇
  2003年   111篇
  2002年   124篇
  2001年   26篇
  2000年   30篇
  1999年   29篇
  1998年   25篇
  1997年   20篇
  1996年   17篇
  1995年   12篇
  1994年   12篇
  1993年   16篇
  1992年   42篇
  1991年   34篇
  1990年   24篇
  1989年   16篇
  1988年   17篇
  1987年   19篇
  1986年   25篇
  1985年   18篇
  1984年   22篇
  1983年   12篇
  1982年   11篇
  1981年   12篇
  1980年   19篇
  1979年   11篇
  1978年   11篇
  1977年   7篇
  1976年   6篇
  1974年   7篇
  1971年   5篇
排序方式: 共有2730条查询结果,搜索用时 15 毫秒
1.
Background Anti-EGFR-based therapies have limited success in HNSCC patients. Predictive biomarkers are greatly needed to identify the patients likely to be benefited from these targeted therapies. Here, we present the prognostic and predictive association of biomarkers in HPV-negative locally advanced (LA) HNSCC patients.Methods Treatment-naive tumour tissue samples of 404 patients, a subset of randomised Phase 3 trial comparing cisplatin radiation (CRT) versus nimotuzumab plus cisplatin radiation (NCRT) were analysed to evaluate the expression of HIF1α, EGFR and pEGFR by immunohistochemistry and EGFR gene copy change by FISH. Progression-free survival (PFS), locoregional control (LRC) and overall survival (OS) were estimated by Kaplan–Meier method. Hazard ratios were estimated by Cox proportional hazard models.Results Baseline characteristics of the patients were balanced between two treatment groups (CRT vs NCRT) and were representative of the trial cohort. The median follow-up was of 39.13 months. Low HIF1α was associated with better PFS [HR (95% CI) = 0.62 (0.42–0.93)], LRC [HR (95% CI) = 0.56 (0.37–0.86)] and OS [HR (95% CI) = 0.63 (0.43–0.93)] in the CRT group. Multivariable analysis revealed HIF1α as an independent negative prognostic biomarker. For patients with high HIF1α, NCRT significantly improved the outcomes [PFS:HR (95% CI) = 0.55 (0.37–0.82), LRC:HR (95% CI) = 0.55 (0.36–0.85) and OS:HR (95% CI) = 0.54 (0.36–0.81)] compared to CRT. While in patients with low HIF1α, no difference in the clinical outcomes was observed between treatments. Interaction test suggested a predictive value of HIF1α for OS (P = 0.008).Conclusions High HIF1α expression is a predictor of poor clinical response to CRT in HPV-negative LA-HNSCC patients. These patients with high HIF1α significantly benefited with the addition of nimotuzumab to CRT.Clinical trial registration Registered with the Clinical Trial Registry of India (Trial registration identifier—CTRI/2014/09/004980).Subject terms: Tumour biomarkers, Head and neck cancer, Tumour biomarkers, Head and neck cancer, Predictive markers  相似文献   
2.
3.
4.

Background  

Skeletal ratios and bone lengths are widely used in anthropology and forensic pathology and hip axis length is a useful predictor of fracture. The aim of this study was to show that skeletal ratios, such as length of femur to height, could be accurately measured from a DXA (dual energy X-ray absorptiometry) image.  相似文献   
5.
BACKGROUND: Electron beam tomography coronary calcium imaging is an evolving technique for the early detection of coronary atherosclerosis, and recent studies have established its prognostic value in asymptomatic individuals. The relationship of coronary artery calcium scores (CAC) to obstructive coronary artery disease (CAD) has been poorly studied but is clinically relevant because it determines which individuals are likely to benefit from revascularization procedures. Hence, we prospectively evaluated the prevalence of myocardial ischemia in asymptomatic patients with cardiovascular risk factors and subclinical atherosclerosis. METHODS AND RESULTS: We studied 864 asymptomatic patients with no previous CAD but with cardiovascular risk factors, referred for electron beam tomography coronary calcium imaging to our institution over an 18-month period. From this group, 220 consecutive patients (85% men; mean age, 61 +/- 9 years; age range, 31-84 years) with moderate to severe atherosclerotic disease (coronary calcium score > or =100 Agatston units) were prospectively evaluated by technetium 99m sestamibi single photon emission computed tomography (SPECT). Patients were followed up (mean follow-up, 14 months) and data regarding their subsequent clinical management recorded. Of the 220 patients, 119 had moderate atherosclerosis (CAC score of 100-400 Agatston units) and 101 had severe atherosclerosis (CAC score > or =400 Agatston units). Abnormal SPECT findings were seen in 18% of patients with moderate atherosclerosis (n = 21) and 45% of patients with severe atherosclerosis (n = 45). Increasing severity of atherosclerosis was related to increasing ischemic burden (summed difference score = 1 +/- 0.2 for CAC score of 100-400 Agatston units and 3.2 +/- 0.5 for CAC score > or =400 Agatston units). In a multivariate linear regression model incorporating risk factors, CAC was the only predictor of silent ischemia. CONCLUSION: In comparison to previously published data, we detected a higher prevalence of silent ischemia even in patients with moderate coronary atherosclerosis (18%). This may reflect the differing risk factor profile of our patient population. When coronary calcium screening is used to preselect asymptomatic patients with cardiovascular risk factors for myocardial perfusion imaging, the optimum coronary calcium score threshold will depend on the population prevalence of risk factors and asymptomatic obstructive CAD.  相似文献   
6.
Paget's disease is a focal condition of bone. To study changes in cells within pagetic lesions, we cultured osteoblasts and stromal cells from 22 patients and compared gene expression in these cells to cells from healthy bone. We identified several differentially regulated genes, and we suggest that these changes could lead to the formation of the lesions. INTRODUCTION: Paget's disease is a focal condition of bone of unknown cause. Although it is regarded as primarily an osteoclast disorder, the tight coupling of the activity of osteoclasts and osteoblasts suggests that the osteoblast could play a key role in its pathogenesis. The aim of the study was to identify possible changes in pagetic osteoblasts and stromal cells that might contribute to the development of pagetic lesions. MATERIALS AND METHODS: Candidate genes were identified based on known bone cell regulators, supplemented with microarray analysis. Gene expression was determined by real-time PCR in primary cultures of osteoblasts and bone marrow stromal cells from pagetic patients and control subjects. Concentrations of secreted proteins were determined by ELISA. RESULTS: Dickkopf1 mRNA and protein levels were increased in both pagetic osteoblast and stromal cell cultures, and interleukin (IL)-1 and IL-6 were overexpressed in pagetic osteoblasts. These changes parallel recent findings in myeloma bone disease, which shares some clinical similarities with Paget's disease. Alkaline phosphatase was overexpressed, and bone sialoprotein and osteocalcin were underexpressed in pagetic osteoblasts, consistent with their circulating levels in pagetic patients. It is hypothesized that overexpression of Dickkopf1, IL-1, and IL-6 would result in stimulation of osteoclast proliferation and inhibition of osteoblast growth, leading to the development of the characteristic lytic bone lesions. By stimulating osteoblast differentiation, Dickkopf1 and IL-6 may also promote mineralization, leading to the conversion of lytic lesions to sclerotic. CONCLUSIONS: These findings suggest that dysregulated gene expression in pagetic osteoblasts could cause the changes in bone cell number and function characteristic of Paget's disease.  相似文献   
7.
8.
9.
We have studied the effect of clonidine pretreatment on cardiovascular responses to various stimuli during craniotomy. Fifty-eight patients (ASA Class I-II), scheduled for supratentorial surgery, were randomly given either oral clonidine, mean dose 3.6 micrograms/kg (n = 28), or oral diazepam, 0.2 mg/kg (n = 30), ninety to one hundred minutes before surgery. Anaesthesia was induced with thiopentone and maintained with nitrous oxide:oxygen, pentazocine and halothane. Pancuronium was used as a neuromuscular blocker. Mean arterial pressure and heart rate were recorded before and after several stimuli. In the clonidine group hypertensive response was significantly less on laryngoscopy (6.5% increases versus 11.2% in the diazepam group), intubation (9.2% versus 16.5%), Mayfield clamp application (14.5% versus 29.91%) and after skin infiltration with lignocaine-adrenaline solution (2.95% versus 5.42%). Heart rate response to laryngoscopy, intubation and skin infiltration was also significantly attenuated in the clonidine group. The sleep dose of thiopentone was smaller in patients pretreated with clonidine. Patients in the diazepam group required more medical intervention. No adverse effect occurred in any patient.  相似文献   
10.
We studied two families with an inherited deletion of the short arm of an X chromosome (Xp) in which affected male offspring have epiphyseal stippling in infancy (chondrodysplasia punctata), nasal hypoplasia, ichthyosis, and mental retardation. The presence of ichthyosis and the apparent pattern of X-linked recessive inheritance prompted investigation of the short arm of the X chromosome through studies of genetic markers and focused cytogenetic analysis. Biochemical studies suggested that there was a deletion of three genes previously mapped to the X-chromosome short arm, including the steroid sulfatase locus, the Xg locus, and the M1C2X locus. Prometaphase chromosomes demonstrated a deletion of Xp at p22.32 in the affected boys, in their obligate-carrier mothers, and in 11 of 25 women at risk as potential carriers. The women carrying the Xp deletion had normal gonadal function and fertility but were shorter than the noncarriers in their families (P less than 0.00001). These findings have implications for the genetic organization of this portion of the human X chromosome and demonstrate that small cytogenetic abnormalities may account for disorders with apparent mendelian patterns of inheritance.  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