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   3703篇
  免费   221篇
  国内免费   19篇
耳鼻咽喉   40篇
儿科学   172篇
妇产科学   79篇
基础医学   462篇
口腔科学   132篇
临床医学   278篇
内科学   809篇
皮肤病学   109篇
神经病学   377篇
特种医学   197篇
外科学   475篇
综合类   31篇
预防医学   215篇
眼科学   87篇
药学   235篇
  1篇
中国医学   6篇
肿瘤学   238篇
  2023年   16篇
  2022年   29篇
  2021年   80篇
  2020年   52篇
  2019年   72篇
  2018年   99篇
  2017年   84篇
  2016年   73篇
  2015年   76篇
  2014年   100篇
  2013年   138篇
  2012年   162篇
  2011年   195篇
  2010年   137篇
  2009年   128篇
  2008年   198篇
  2007年   186篇
  2006年   189篇
  2005年   173篇
  2004年   147篇
  2003年   150篇
  2002年   163篇
  2001年   113篇
  2000年   118篇
  1999年   95篇
  1998年   71篇
  1997年   65篇
  1996年   61篇
  1995年   34篇
  1994年   44篇
  1993年   39篇
  1992年   62篇
  1991年   66篇
  1990年   67篇
  1989年   58篇
  1988年   54篇
  1987年   43篇
  1986年   45篇
  1985年   20篇
  1984年   31篇
  1983年   35篇
  1982年   20篇
  1981年   22篇
  1980年   18篇
  1979年   17篇
  1976年   13篇
  1975年   9篇
  1970年   8篇
  1969年   11篇
  1966年   8篇
排序方式: 共有3943条查询结果,搜索用时 31 毫秒
1.
2.
BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a rare malignant tumour of the skin, with an estimated incidence of 0.8 to five cases per 1 million people per year. OBJECTIVE: To study epidemiological, immunohistochemical and clinical features, delay in diagnosis, type of treatment and outcome of DFSP from 1982 to 2002. METHODS: Using data from the population-based cancer registry, 66 patients with pathologically proved DFSP were included (fibrosarcomatous DFSP were excluded). Each patient lived in one of the four departments of Franche-Comté (overall population of 1 million people) at the time of diagnosis. The main data sources came from public and private pathology laboratories and medical records. The rules of the International Agency for Research on Cancer were applied. RESULTS: The estimated incidence of DFSP in Franche-Comté was about three new cases per 1 million people per year. Male patients were affected 1.2 times as often as female patients were. The trunk (45%) followed by the proximal extremities (38%) were the most frequent locations. DFSP occurred mainly in young adults between 20 and 39 years of age. Mean age at diagnosis was 43 years, and the mean delay in diagnosis was 10.08 years. Our 66 patients initially underwent a radical local excision. Among them, 27% experienced one or more local recurrences during 9.6 years of follow-up. There was one regional lymph node recurrence without visceral metastases. These recurrences were significantly related to the initial peripheral resection margins. We observed a local recurrence rate of 47% for margins less than 3 cm, vs. only 7% for margins ranging from 3 to 5 cm [P=0.004; OR=0.229 (95%, CI=0.103-0.510)]. The mean time to a first local recurrence was 2.65 years. Nevertheless, there was no death due to the DFSP course at the end of the follow-up, and the final outcome was favourable. CONCLUSION: Our study emphasizes the importance of wide local excision with margins of at least 3 cm in order to prevent local recurrence. However, the recent development of inhibitors of signal transduction by the PDGFB pathway should soon modify the surgical strategy, which is often too mutilating.  相似文献   
3.
4.
A Serra  G Polese  C Braggion    A Rossi 《Thorax》2002,57(1):50-54
BACKGROUND: Patients with advanced cystic fibrosis can benefit from non-invasive positive pressure ventilation (NPPV) for the treatment of acute decompensation as well as for the management of chronic respiratory failure. This study was undertaken to compare the physiological effects of non-invasive proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilatory pattern, transcutaneous blood gas tensions, and diaphragmatic effort in stable patients with cystic fibrosis and chronic CO2 retention. METHODS: In 12 patients two periods of spontaneous breathing were followed randomly by PSV (12 (3) cm H2O) and PAV (flow assist 4.9 (1.3) cm H2O/l.s, volume assist 18.9 (5.1) cm H2O/l) set for the patient's comfort and administered for 40 minutes with 2 cm H2O continuous positive airway pressure. Ventilatory pattern, transcutaneous blood gas tensions, and surface diaphragmatic electromyography were measured in the last 10 minutes of each application. RESULTS: On average, both PSV and PAV improved ventilation (+30%), tidal volume (+30%), and transcutaneous CO2 (-7%) while reducing diaphragmatic activity (-30% with PSV, -20% with PAV). Mean inspiratory airway pressure was lower during PAV than during PSV (9.7 (1.9) and 12.9 (2.7) cm H2O, respectively; p<0.05). The mean coefficient of variation of tidal volume was about 20% (range 11-39%) during spontaneous breathing and did not change with either PAV or PSV. CONCLUSIONS: These results show that short term administration of nasal PAV and PSV to patients with stable cystic fibrosis with chronic respiratory insufficiency is well tolerated, improves ventilation and blood gas tensions, and unloads the diaphragm.  相似文献   
5.
Zusammenfassung Nach Einspritzung einer einzigen Dose von Vitamin B1, B2 und C wurden folgende Ergebnisse erzielt: 1. Nach Verabreichung von Vitamin B1 eine beständige Vermehrung der Perspiratio insensibilis und eine geringe Verminderung der Quaddelzeit; 2. nach Verabreichung von Vitamin B2 in den meisten Fällen Vermehrung der Perspiratio insensibilis und Veränderungen in positivem und negativem Sinne der Quaddelzeit; 3. nach Verabreichung von Vitamin C in den meisten Fällen Vermehrung der Perspiratio insensibilis und in allen Fällen Verlängerung der Quaddelzeit.  相似文献   
6.
Hirschsprung disease (HSCR) is considered a model for a complex inheritance disorder. Several genes, including the major HSCR-susceptibility RET proto-oncogene, play an aetiological role in the development of HSCR. Genetic linkage analysis in familial HSCR with both long- and short-segment phenotypes has demonstrated a tight linkage to the RET locus, while the phenotype within a HSCR family is characterised by an incomplete penetrance or a variable extension of the aganglionosis. Therefore, additional genetic alterations of RET are postulated in the aetiology or modification of the HSCR phenotype. In this study, the coding region of all 21 exons of the RET proto-oncogene, including the flanking intronic sequences, were investigated by direct DNA sequencing in a HSCR population. We genotyped the c.135 G/A polymorphism and resolved haplotypes comprising the mutation locus and the c.135 G/A polymorphism. Twenty different mutations were detected in 18 of 76 HSCR patients. In ten families the mutations were inherited from the parents, while only four patients had a positive family history for the disease. Moreover, in all ten families an incomplete penetrance of the HSCR phenotype was observed. We have investigated the effect of the non-mutated wild-type allele as well as the c.135 G/A polymorphism on the phenotype within the HSCR families. Our findings support the notion that both RET alleles are involved in the pathogenesis of a subgroup of HSCR patients in a dose-dependent fashion. Additionally, we have shown a modifying effect of the c.135 G/A polymorphism on the HSCR phenotype within HSCR families.  相似文献   
7.
γδ T lymphocytes respond to different bacterial antigens and transformed cells. The antigenic molecules responsible for this activity have been studied extensively in antigenic preparations from Mycobacterium . We describe here the in vitro effect of Pseudomonas aeruginosa on γδ T lymphocytes and the properties of the implicated compounds. We found a preferential γδ T-cell expansion when we used heat-treated P. aeruginosa preparations and a dose-dependent inhibition of proliferation of peripheral blood mononuclear cells (PBMC) when non-heat-treated antigens were studied. This expansion corresponded to a Vγ9-positive subpopulation. In contrast to αβ T lymphocytes, the highest stimulatory activity was restricted to very small cytosolic compounds. This activity was protease resistant and phosphatase sensitive and always dependent on interleukin (IL)-2 or αβ T-cell activation. We concluded that the antigenic molecules from P. aeruginosa that activated γδ T lymphocytes were small, non-peptidic, phosphorylated compounds, similar to those previously described from Mycobacterium .  相似文献   
8.
Over the past decade, the unfortunate reality is that the income gap has widened between Canadian families. Educational outcomes are one of the key areas influenced by family incomes. Children from low-income families often start school already behind their peers who come from more affluent families, as shown in measures of school readiness. The incidence, depth, duration and timing of poverty all influence a child’s educational attainment, along with community characteristics and social networks. However, both Canadian and international interventions have shown that the effects of poverty can be reduced using sustainable interventions. Paediatricians and family doctors have many opportunities to influence readiness for school and educational success in primary care settings.  相似文献   
9.
Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.  相似文献   
10.
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