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   10198篇
  免费   545篇
  国内免费   78篇
耳鼻咽喉   116篇
儿科学   226篇
妇产科学   184篇
基础医学   1312篇
口腔科学   242篇
临床医学   1040篇
内科学   2435篇
皮肤病学   112篇
神经病学   1166篇
特种医学   352篇
外科学   1683篇
综合类   14篇
预防医学   297篇
眼科学   105篇
药学   640篇
中国医学   12篇
肿瘤学   885篇
  2024年   10篇
  2023年   55篇
  2022年   152篇
  2021年   219篇
  2020年   134篇
  2019年   185篇
  2018年   255篇
  2017年   212篇
  2016年   255篇
  2015年   237篇
  2014年   361篇
  2013年   499篇
  2012年   784篇
  2011年   717篇
  2010年   401篇
  2009年   391篇
  2008年   676篇
  2007年   644篇
  2006年   686篇
  2005年   662篇
  2004年   689篇
  2003年   599篇
  2002年   511篇
  2001年   104篇
  2000年   80篇
  1999年   90篇
  1998年   116篇
  1997年   86篇
  1996年   93篇
  1995年   81篇
  1994年   69篇
  1993年   73篇
  1992年   66篇
  1991年   66篇
  1990年   48篇
  1989年   60篇
  1988年   43篇
  1987年   39篇
  1986年   42篇
  1985年   34篇
  1984年   39篇
  1983年   29篇
  1982年   37篇
  1981年   33篇
  1980年   28篇
  1979年   17篇
  1978年   16篇
  1977年   12篇
  1975年   10篇
  1972年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Summary We investigated the role of urinary testosterone levels as a marker of risk of recurrent disease in 113 operable breast cancer patients (70 premenopausal, 43 postmenopausal). Twenty-four-hour urine collections for testosterone measurement were obtained before surgical treatment, between 20–40 days thereafter, and then every 6 months for 5 years. The cutoff values to separate high testosterone (A+) from normal testosterone (A–) were 8.0µg/24h in premenopause and 4.9µg/24h in postmenopause. Urinary testosterone levels were considered high when they exceeded the cutoff value in at least 2 of the first 3 measurements (pretreatment, post-treatment, 6 months) of each patient. According to the aforementioned criterion, 33 patients (29.2%) had high testosterone levels, which were associated to axillary node involvement in 16 patients. Thirteen of the latter relapsed during the 5-year follow-up period (5/7 in premenopause, 8/9 in postmenopause). Relapse-free survival (RFS) curves were drawn only for node-positive patients owning to the small number of recurrences observed in the node-negative group. In premenopausal node-positive patients, RFS was significantly different for patients presenting high and normal urinary testosterone levels (77% vs 28%, respectively; logrank test, p< 0.006). In postmenopausal node-positive patients, RFS was also different between the two groups (54% vs 11% in high and normal excretors, respectively) but the difference was not statistically significant. The present findings suggest that urinary testosterone is a prognostic indicator of early breast cancer recurrence in node-positive patients.  相似文献   
993.
Sensory disturbances such as anesthesia, hypoesthesia, hyperesthesia, and paresthesia may be present in the oral cavity, stemming from many local and systemic factors. Paresthesia of the inferior alveolar nerve is quite rare because of the unique anatomy of this nerve. Among other effects, periapical lesions can damage the nerve, resulting in paresthesia of its innervated area. Only a few cases of paresthesia caused by these lesions are reported in the literature. In this report we present a case of paresthesia of the right inferior alveolar nerve; discuss the anatomy, pathobiology, and etiology; and suggest that a periapical lesion affecting the lower right second molar (No. 31) may have been the cause. The routine x-rays (intraoral and panorex) and the axial and cross-sectional tomographs of the mandible by means of computed tomography contribute to making this case a good example of nerve injury.  相似文献   
994.
995.
Vitamin D status is currently considered among the relevant determinants of skeletal integrity. Since vitamin D levels present seasonal variations, we longitudinally studied young healthy men and women in order to investigate the related physiologic modifications of both calcium homeostasis and bone remodeling. Thirty-two men (mean age 39.4 ± 7.8 years) and 58 premenopausal women (aged 36.9 ± 6.4 years) from southern Italy were studied. In all subjects the following parameters were measured both in winter and in summer: serum calcium, phosphorus, creatinine, total alkaline phosphatase activity, 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), osteocalcin (BGP), together with urinary calcium (Ca/Cr), total pyridinoline (Pyr/Cr) and deoxypyridinoline (d-Pyr/Cr), corrected for creatinine excretion. In both sexes 25OHD levels were significantly higher in summer, while PTH values were lower, than in winter. The prevalence of hypovitaminosis D, defined by concentrations of 25OHD lower than 30 nmol/l, was 17.8% in winter and 2.2% in summer in the whole sample, while it was 27.8% and 3.4%, respectively, among female subjects. Indeed male subjects did not display hypovitaminosis D, having throughout the year significantly higher calcium and 25OHD levels together with lower PTH values, than the women. Moreover, alkaline phosphatase total activity was more elevated in men both in winter and in summer. In women, during winter, bone remodeling markers levels were higher while urinary calcium levels were lower than in summer. In the whole sample serum 25OHD correlated positively with serum calcium and inversely with PTH. The seasonal percentage variations in PTH were inversely correlated with those of Ca/Cr. Our results show a relatively high prevalence of subclinical vitamin D deficiency among young healthy women from southern Italy. Significant gender-specific differences have been demonstrated in both calcium homeostasis and skeletal remodeling indexes; the seasonal fluctuations in the vitamin D–PTH axis are accompanied by cyclical variations of bone turnover rate, which were more pronounced in women. Received: 11 January 2001 / Accepted: 6 July 2001  相似文献   
996.
997.
OBJECTIVE: To establish a correlation between the retinal nerve fiber layer (RNFL) thickness measured by a scanning laser polarimeter (GDx) and the pattern electroretinogram (p-ERG) amplitudes in a heterogeneous population sample composed of normal subjects, ocular hypertensive and glaucomatous patients. METHODS: 112 subjects were considered: 40 glaucomatous patients, 39 ocular hypertensive and 33 normal subjects. All were examined with the GDx, and the RNFL thickness was measured. A transient p-ERG was then recorded. RESULTS: A statistically significant correlation was observed between the RNFL thickness and the p-ERG amplitudes (p < 0.001) by means of linear regression analysis. CONCLUSION: We observed a strict correlation between the measurements of the RNFL thickness obtained with the GDx and the amplitude of the p-ERG signal. These techniques represent additional objective tools to detect an early glaucomatous damage.  相似文献   
998.
999.
The aim of this report was to evaluate the effectiveness of the endoscopic treatment of colonic polyps to allow secondary prophylaxis in order to prevent the onset of cancer arising from adenomas. From October 2002 to January 2004 we performed 487 colonoscopies on a patient group with the following indications: screening prior to kidney transplant; screening for colorectal cancer (patients positive at faecal occult blood testing); follow-up of patients who had undergone colonic resections for colorectal cancer; patients with other diseases. Colorectal polyps were diagnosed in 15 males and 15 females, with a mean age of 63 years. All the neoplasms were resected during colonoscopy and specimens sent for histological study. The histological examinations yielded the following results: 4 hyperplastic polyps; 9 tubular adenomas (6 with mild, 2 with mild-to-moderate, and 1 with severe dysplasia); 8 tubulo-villous adenomas (3 with mild, 1 with mild-to-moderate, and 4 with moderate dysplasia); 4 villous adenomas (3 with mild and 1 with severe dysplasia); 1 adenocarcinoma; 1 inflammatory polyp; in 3 cases we were unable to retrieve the polyps after polypectomy. Colonoscopic detection of a neoplasm allows us to remove it and send to the pathology laboratory for definitive histological diagnosis. Moreover, snare polypectomy can be a radical treatment for dysplastic polyps without stromal axis and basal membrane infiltration. We therefore conclude that colonoscopy allows not only early diagnosis of colonic neoplasms, but also radical curative treatment in the early stages.  相似文献   
1000.
OBJECTIVE: To investigate the efficacy of imipenem, piperacillin combined with cecropin B in the prevention of lethality in 2 rat models of septic shock. Main outcome measures were bacterial growth in blood and intra-abdominal fluid, endotoxin and TNF-alpha concentrations in plasma, and lethality. BACKGROUND: Sepsis remains a serious clinical problem despite intense efforts to improve survival. It is a major cause of morbidity and mortality in hospitalized patients. The primary cause of Gram-negative shock results from activation of host effector cells by endotoxin, the lipopolysaccharide (LPS) associated with cell membranes of Gram-negative bacteria. METHODS: Adult male Wistar rats were given (1). an intraperitoneal injection of 1 mg of Escherichia coli 0111:B4 LPS or (2). 2 x 1010 CFU of E. coli ATCC 25922. All animals were randomized to receive intraperitoneally isotonic sodium chloride solution, 1 mg/kg cecropin B, 20 mg/kg imipenem, and 120 mg/kg piperacillin alone and combined with 1 mg/kg cecropin B. Each group included 20 animals.RESULTS All compounds reduced the lethality when compared with controls. Piperacillin and imipenem significantly reduced the lethality and the number of E. coli in abdominal fluid compared with saline treatment. On the other hand, each betalactam determined an increase of plasma endotoxin and TNF-alpha concentration. Combination between cecropin B and betalactams showed to be the most effective treatment in reducing all variables measured. CONCLUSION: Cecropin B enhances betalactams activities in Gram-negative sepic shock rat models.  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