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   9963篇
  免费   567篇
  国内免费   84篇
耳鼻咽喉   78篇
儿科学   308篇
妇产科学   117篇
基础医学   1150篇
口腔科学   444篇
临床医学   887篇
内科学   2393篇
皮肤病学   230篇
神经病学   797篇
特种医学   470篇
外科学   1635篇
综合类   18篇
一般理论   1篇
预防医学   540篇
眼科学   93篇
药学   459篇
中国医学   11篇
肿瘤学   983篇
  2024年   17篇
  2023年   128篇
  2022年   222篇
  2021年   438篇
  2020年   207篇
  2019年   329篇
  2018年   402篇
  2017年   266篇
  2016年   268篇
  2015年   300篇
  2014年   391篇
  2013年   463篇
  2012年   665篇
  2011年   732篇
  2010年   424篇
  2009年   393篇
  2008年   616篇
  2007年   600篇
  2006年   571篇
  2005年   560篇
  2004年   505篇
  2003年   453篇
  2002年   370篇
  2001年   165篇
  2000年   138篇
  1999年   122篇
  1998年   73篇
  1997年   68篇
  1996年   55篇
  1995年   45篇
  1994年   39篇
  1993年   38篇
  1992年   59篇
  1991年   47篇
  1990年   44篇
  1989年   41篇
  1988年   38篇
  1987年   34篇
  1986年   35篇
  1985年   26篇
  1984年   21篇
  1983年   24篇
  1982年   18篇
  1980年   11篇
  1979年   15篇
  1977年   16篇
  1975年   14篇
  1974年   12篇
  1973年   13篇
  1968年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Clinical significance of the assessment of endothelial function]   总被引:1,自引:0,他引:1  
Endothelium-derived nitric oxide is not only a potent vasodilator but also inhibits platelet aggregation, vascular smooth muscle cell migration and proliferation, monocyte adhesion and adhesion molecule expression, thus protecting the vessel wall from the development of atherosclerosis and thrombosis. Major cardiovascular risk factors are associated with endothelial dysfunction, which involves enhanced production of oxygen free radicals, that can destroy nitric oxide and reduce its availability, and release of endothelium-derived contracting factors including prostanoids and endothelin-1. Endothelial dysfunction is a promoter of atherosclerotic and thrombotic damage and in prospective studies on patients with high cardiovascular risk impaired endothelium-dependent vasodilation is associated with an increased incidence of cardiovascular events. However, endothelial function cannot yet be included among the surrogate endpoints which need to be measured for cardiovascular risk stratification. This limitation springs from the fact that available tests to assess endothelium-dependent vasodilation are invasive or, if noninvasive, they have no sufficient sensitivity and specificity to be proposed for clinical practice. Moreover, no study is available demonstrating that reversal of endothelial dysfunction, which can be obtained by appropriate treatment, is independently associated with a better clinical outcome. However it is conceivable that in the future, by the utilization of a non-invasive method such as the determination of brachial artery flow-mediated dilation, large-scale multicenter trials might provide a definitive answer to the real prognostic value of endothelial dysfunction, in terms of cardiovascular risk and therapeutic approach.  相似文献   
992.
Purpose: To report a case of CRB1-associated retinal dystrophy characterized by vitritis, retinal capillaritis, and cystoid macular edema (CME).

Methods: A case report.

Results: An 8-year-old boy was diagnosed with intermediate uveitis and treated with corticosteroids. He was subsequently diagnosed with retinal dystrophy and found to have two CRB1 mutations.

Conclusions: Retinal capillaritis, vitritis, and CME could be inflammatory features of CRB1 retinal dystrophy in our young patient.  相似文献   

993.
Unresectable neuroendocrine neoplasms (NENs) often poorly respond to standard therapeutic approaches. Alkylating agents, in particular temozolomide, commonly used to treat high-grade brain tumors including glioblastomas, have recently been tested in advanced or metastatic NENs, where they showed promising response rates. In glioblastomas, prediction of response to temozolomide is based on the assessment of the methylation status of the MGMT gene, as its product, O6 -methylguanine-DNA methyltransferase, may counteract the damaging effects of the alkylating agent. However, in NENs, such a biomarker has not been validated yet. Thus, we have investigated MGMT methylation in 42 NENs of different grades and from various sites of origin by two different approaches: in contrast to methylation-specific PCR (MSP), which is commonly used in glioblastoma management, amplicon bisulfite sequencing (ABS) is based on high-resolution, next-generation sequencing and interrogates several additional CpG sites compared to those covered by MSP. Overall, we found MGMT methylation in 74% (31/42) of the NENs investigated. A higher methylation degree was observed in welldifferentiated tumors and in tumors originating in the gastrointestinal tract. Comparing MSP and ABS results, we demonstrate that the region analyzed by the MSP test is sufficiently informative of the MGMT methylation status in NENs, suggesting that this predictive parameter could routinely be interrogated also in NENs.  相似文献   
994.
Malignant thymoma in children: a 20-year review   总被引:1,自引:0,他引:1  
Malignant thymomas are extremely rare in children, with only 27 cases reported thus far in the pediatric surgical literature. We report four additional cases diagnosed at this institution over the past 20 years (ages 3 to 14 years). Clinical presentations included superior vena cava syndrome, cough, dyspnea, cyanosis, enlarging mediastinal mass, spontaneous pneumothorax, and pleuropericardial effusion. Three patients underwent incomplete resection of the mass or biopsy because of "unresectability" and were treated with radiotherapy and adjunctive chemotherapy. One patient underwent near complete macroscopic resection as well as radiotherapy and chemotherapy. All patients died at intervals ranging from 6 months to 2 1/2 years after diagnosis. Three patients were found to have metastatic disease prior to death or at autopsy. In one case, the initial pathological diagnosis was lymphocytic thymoma. After ultrastructural studies were performed, the diagnosis was changed to thymic T-cell lymphoma. This patient subsequently developed acute lymphoblastic leukemia 3 months after surgical resection followed by radiotherapy. Malignant thymomas are highly aggressive tumors in children. A radical surgical approach with complete excision of the tumor and contiguous structures in continuity, with adjunctive radiotherapy and chemotherapy remains the only hope for survival in children with these rare lesions.  相似文献   
995.
A noninvasive means to predict the onset and recurrence of lupus nephritis (LN) before overt renal injury is needed to optimize and individualize treatment. Colony-stimulating factor-1 (CSF-1) is expressed by kidney tubules at the onset of LN, increases with disease progression, and spills into the circulation in lupus-prone mice. We tested the hypothesis that amplified expression of CSF-1 detected in the serum or urine correlates with intrarenal CSF-1 expression and histopathology (increased macrophage accumulation, activity indices) and clinical kidney disease activity and predicts the onset and recurrence of nephritis in patients with systemic lupus erythematosus (SLE). We found increased serum or urine CSF-1 levels in patients with cutaneous, serositis, and musculoskeletal disease; however, the increase in CSF-1 levels was far greater in LN. Moreover, an elevation in serum or urine CSF-1 levels correlated with increasing intrarenal CSF-1 expression and histopathology. By longitudinally tracking patients, we found that elevated serum CSF-1 heralded the initial onset of disease, and a rise in serum or urine CSF-1 predicted recurrences of LN before clinical evidence of glomerular dysfunction and conventional serologic measures, even in patients with other manifestations of SLE. These findings indicate that serial monitoring for a rise in serum or urine CSF-1 levels in patients with SLE reflects kidney histopathology and may predict renal disease activity and the onset and recurrence of LN more accurately than conventional laboratory measures.  相似文献   
996.
Background The prognosis of unresectable metastatic colorectal cancer might be improved if a radical surgical resection of metastases could be performed after a response to chemotherapy. Methods We treated 74 patients with unresectable metastatic colorectal cancer (not selected for a neoadjuvant approach) with irinotecan, oxaliplatin, and 5-fluorouracil/leucovorin (FOLFOXIRI and simplified FOLFOXIRI). Because of the high activity of these regimens (response rate, 72%), a secondary curative operation could be performed in 19 patients (26%). Results Four patients underwent an extended hepatectomy, nine patients underwent a right hepatectomy, three patients underwent a left hepatectomy, and three patients had a segmental resection. In five patients, surgical removal of extrahepatic disease was also performed. In seven patients, surgical resection was combined with intraoperative radiofrequency ablation. The median overall survival of the 19 patients who underwent operation is 36.8 months, and the 4-year survival rate is 37%. The median overall survival of the 34 patients who were responsive to chemotherapy, but who did not undergo operation, is 22.2 months (P = .0114). Conclusions The FOLFOXIRI regimens we studied have significant antitumor activity and allow a radical surgical resection of metastases in patients with initially unresectable metastatic colorectal cancer not selected for a neoadjuvant approach and also those with extrahepatic disease. The median survival of patients with resected disease is promising.  相似文献   
997.
998.
OBJECTIVE: A higher mortality has been reported after pneumonectomy over the age of 70. The aim of the study was to quantify the additional risk due to age after standard pneumonectomy for lung cancer by a case-control study. METHODS: Our clinical database was reviewed to search for patients aged 70 years or more who underwent standard pneumonectomy for lung cancer between 1998 and 2005. A control group of patients younger than 70 (one case/two controls) was matched for sex, cardiovascular disease, American Association of Anaesthetists score, respiratory function, side of pneumonectomy, induction chemotherapy and stage. Overall mortality and morbidity were compared. Long-term survival data were also analysed. RESULTS: During the considered period, 35 patients aged 70 years or more underwent pneumonectomy (30 males, median age 73 years, 15 right-sided procedures). The control group was composed of 70 patients. The two groups were homogeneous in the variables used for matching. Overall mortality and morbidity were 11.4 and 54.2% in the elderly group as compared to 4.3 and 41.6% in controls (p-value not significant). Elderly patients experienced a higher rate of respiratory complications (25.7%) as compared to controls (8.3%, p=0.01). At univariate analysis, the only risk factor for death was the occurrence of respiratory complications (OR 6.5, CI 1.8-18.2). At multivariate analysis, age >or=70 years (OR 5.36, CI 1.48-19.3) and preoperative chemotherapy (OR 7.65, CI 2.04-28.6) were confirmed as predictors of respiratory complications. Five-year survival was 17.5% in the elderly group and 53.6% in the control group (p=0.003). Elderly patients with a better respiratory function (FEV1>70%) had a 5-year survival of 45.4%. CONCLUSIONS: In the elderly patients, the risk of respiratory complications after pneumonectomy is increased as compared to younger patients with equivalent respiratory function. Age and preoperative chemotherapy are independent risk factors for respiratory complications. A lower mortality and a better long-term survival are obtained in elderly patients with a better respiratory function (FEV1>or=70%).  相似文献   
999.
Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1 M KF solution treatments, 0.1 M FST and 1 M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F? treatments. The corrosion inhibitory action of 0.1 M FST and 1 M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1 M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1 M FST showed the presence of KMgF3 crystals on the surface while a MgF2 film was detected for 1 M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F?-containing film which ensures the gradual degradation process.  相似文献   
1000.

Study objective

We investigated seasonal prevalence of hyponatremia in the emergency department (ED).

Design

A cross-sectional study using clinical chart review.

Setting

University Hospital ED, with approximately 28 000 patient visits a year.

Type of participants

We reviewed 15 049 patients, subdivided in 2 groups: the adult group consisting of 9822 patients aged between 18 and 64 years old and the elderly group consisting of 5227 patients aged over 65 years presenting to the ED between January 1st, 2014 and December 31st, 2015.

Intervention

Emergency patients were evaluated for the presence of hyponatremia by clinical chart review.

Measurements and main results

Hyponatremia was defined as a serum sodium level < 135 mmol/l. Mean monthly prevalence of hyponatremia was of 3.74 ± 0.5% in the adult group and it was significantly increased to 10.3 ± 0.7% in the elderly group (p < 0.05 vs adults). During the summer, hyponatremia prevalence was of 4.14 ± 0.2% in adult and markedly increased to 12.52 ± 0.7% (zenith) in elderly patients (p < 0.01 vs adult group; p < 0.05 vs other seasons in elderly group). In the elderly group, we reported a significant correlation between weather temperature and hyponatremia prevalence (r: 0.491; p < 0.05).

Conclusion

We observed a major influence of climate on the prevalence of hyponatremia in the elderly in the ED. Decline in renal function, salt loss, reduced salt intake and increased water ingestion could all contribute to developing hyponatremia in elderly patients during the summer. These data could be useful for emergency physicians to prevent hot weather-induced hyponatremia in the elderly.  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