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   3098篇
  免费   129篇
  国内免费   89篇
耳鼻咽喉   6篇
儿科学   74篇
妇产科学   40篇
基础医学   304篇
口腔科学   47篇
临床医学   289篇
内科学   735篇
皮肤病学   44篇
神经病学   116篇
特种医学   350篇
外国民族医学   1篇
外科学   217篇
综合类   30篇
预防医学   184篇
眼科学   8篇
药学   143篇
肿瘤学   728篇
  2023年   7篇
  2022年   18篇
  2021年   30篇
  2020年   12篇
  2019年   24篇
  2018年   30篇
  2017年   20篇
  2016年   33篇
  2015年   50篇
  2014年   39篇
  2013年   90篇
  2012年   79篇
  2011年   82篇
  2010年   100篇
  2009年   111篇
  2008年   123篇
  2007年   175篇
  2006年   130篇
  2005年   124篇
  2004年   91篇
  2003年   123篇
  2002年   101篇
  2001年   102篇
  2000年   119篇
  1999年   104篇
  1998年   129篇
  1997年   120篇
  1996年   134篇
  1995年   104篇
  1994年   103篇
  1993年   99篇
  1992年   76篇
  1991年   85篇
  1990年   70篇
  1989年   57篇
  1988年   55篇
  1987年   47篇
  1986年   54篇
  1985年   47篇
  1984年   32篇
  1983年   30篇
  1982年   26篇
  1981年   23篇
  1980年   18篇
  1979年   7篇
  1978年   16篇
  1977年   16篇
  1976年   17篇
  1975年   8篇
  1971年   5篇
排序方式: 共有3316条查询结果,搜索用时 15 毫秒
11.
Shared care: a review of the literature   总被引:7,自引:1,他引:6  
This review examines broad issues of concern regarding the primary/secondarycare interface. The main purpose was to identify areas of goodpractice which could be adapted for more general use. One ofthe most fundamental aspects identified was communication, whichis discussed in some detail. Also covered are shared prescribingand disease management. The data suggest that the most effectivesystem(s) of shared care has yet to be established. Furtherqualitative and economic evaluations are required, taking intoaccount patient preferences. Although the literature does describecertain practice exemplars, it is clear that inter- and intra-professionalcommunication continues to be a problem. Whilst informationtechnology may provide some of the solutions, it is concludedthat a culture change, which compels health professionals tomake sharing of patient information a much higher priority,is reauired. Keywords. Shared care, seamless care, hospital, general practice, family practice.  相似文献   
12.
Ageing is associated with complex remodelling in the phenotypic and functional profiles of T lymphocytes. We investigated whether expression of CD28 antigen on T cells is conserved throughout adulthood and ageing in humans. For this purpose we analysed T cells obtained from peripheral blood of 102 healthy people of ages ranging from 20 to 105 years. We found an age-related increase of CD28- T cells in percentage and absolute number, predominantly among CD8+ T cells. CD28- T cells from aged donors analysed by flow cytometry appeared as resting cells (not expressing CD25, CD38, CD69, CD71, DR), bearing markers of cytotoxic activity (CD 11b and CD 57) and with a phenotype compatible with 'memory' cells (up-regulated CD2 and CD11a; CD62L absent). At the functional level, freshly isolated purified CD28- CD8+ T cells showed high anti-CD3 redirected cytotoxic activity against Fc-bearing P815 cells. The same activity tested on freshly isolated bulk T lymphocytes was significantly augmented with age. We found a positive correlation between age, number of CD8+ CD28- T cells and anti-CD3 redirected cytotoxicity by freshly isolated T cells. These data suggest that an activation of unknown nature within the cytotoxic arm of the immune system occurs with age. We speculate that these cytotoxic T lymphocytes (CTL) in vivo may constitute armed effector cells for immediate killing of targets bearing peptides from pathogens of intracellular origin.  相似文献   
13.
The aim of this study was to compare the efficacy of pure follicle stimulating hormone (FSH) with that of FSH/human menopausal gonadotrophin (HMG) combination in downregulated cycles. A total of 357 patients was evaluated retrospectively. Sixty percent of patients in the FSH group and 55% in the FSH/HMG group were new; the others were repeat patients. Ovulation was suppressed with leuprolide acetate in all patients, followed by either FSH (n = 218) or FSH/HMG (n = 119). There was no difference in patients' age, infertility factors, number of ampoules used, length of stimulation, oestradiol levels on day of human chorionic gonadotrophin (HCG) administration, number of oocytes recovered or the number of embryos transferred. Also, nuclear maturity at aspiration and fertilization rates were not different between the two groups. FSH stimulation resulted in a significantly higher percentage of mature oocytes that showed the typical 'mature' morphological characteristics (P < 0.0001). The clinical pregnancy rates per transfer were 40 and 28% in patients stimulated with pure FSH and FSH/HMG respectively (P < 0.05). The significantly higher number of immature oocytes matured in vitro in the FSH/HMG group (P = 0.001) suggests a possible effect on in-vitro maturation, due to luteinizing hormone present in HMG. The difference in mature oocyte quality may be an important determinant in the higher pregnancy rates for the FSH- stimulated patients.   相似文献   
14.
Phenotypic features and proliferative ability of thymocytes, splenocytes and peripheral blood lymphocytes of 20-22 weeks human fetuses affected by Down's syndrome (DS) were studied and compared to those of fetuses of the same gestational age with a normal karyotype. In the thymus of both DS and normal fetuses, the great majority of cells was CD1+, CD2+, CD5+, CD4+, CD8+; using double fluorescence analysis, these markers could be detected on the same cell. About 50-60% showed CD3 antigen and about 40-50% presented the alpha beta T cell receptor. Thymocytes with NK markers (CD16, CD57, CD56) were not found. After stimulation with phytohemagglutinin, thymocytes showed a low but detectable proliferative capability, while splenocytes and peripheral blood lymphocytes showed a high responsiveness to the mitogen. These data show that the impaired immune system in DS is not associated with gross abnormalities of phenotypic T cell development in the fetal thymus or with an inability of such fetal cells to proliferate after a mitogenic stimulus.  相似文献   
15.
Autoantibodies that react exclusively with the gastrin-secreting cell of human antrum have been detected by immunofluorescence in eight of 106 patients with histologic evidence of chronic atrophic gastritis, Type B, involving mainly the antrum. These antibodies were of the IgG class and of low titer. However, follow-up studies one to two years later showed persistently positive reactions, despite symptomatic treatment. These data support the concept of an autoimmune variant of chronic "antral" gastritis, Type B.  相似文献   
16.
A hospital-based case-control study of renal cell cancer was conducted in northern Italy betwen 1986 and 1989, with 240 cases of renal cell cancer (150 males and 90 females), and 665 controls (445 males and 220 females) chosen on the basis of age, sex, and area of residence. No associations were found between renal cell cancer and: body mass index (BMI); number of cigarettes smoked; age at starting to smoke; years of smoking; consumption of wine, beer, spirits, coffee, decaffeinated coffee; tea; intake of animal protein, fruits, and vegetables; various resproductive factors; hormonal use; sexual habits; sexually transmitted diseases; or selected occupational exposures. The odds ratio (OR) was above unity in smokers (OR=1.34 for 15 cigarettes/day), but the trends in risk with dose or duration were not statistically significant. Significant positive associations were found between renal cell cancer and sources of fat intake, especially margarine (OR for highest vs lowest intake = 1.71), and oils (OR=1.89) whereas carrot intake showed a negative association (OR=0.62). Also, a history of nephrolithiasis and multiple episodes of cystitis showed weak positive associations (OR=2.00, 95 percent confidence interval (CI) 1.07–3.73; and OR=1.60, 95 percent CI 0.95–2.70, respectively).Address reprint requests to Dr Talamini. The work was conducted with the contribution of the Italian Association for Cancer Research, Milan, Italy and the CNR (Italian National Research Council) Applied Projects Oncology (Contract n. 85.02209.44).Drs Talamini, Barón, Barra, Bidoli, Serraino, and Franceschi are in the Epidemiology Unit, Aviano Cancer Center, Via Pedemontana Occ. 33081 Aviano (PN) Italy. At the time of this work, Dr Barón was a visiting biostatistician from the Department of Preventive Medicine and Biometrics, University of Colorado, Health Science Center, CO, funded by the National Cancer Institute (US) and the Italian National Research Council. Dr Franceschi is also chief of the Hormones and Sexual Factors and Cancer Working Group of the European Organization for Cooperation in Cancer Prevention Studies, Bruxelles, Belgium. Drs La Vecchia and Negri are in the Mario Negri Institute for Pharmacological Research, Milan, Italy. Dr La Vecchia is also in the Institute of Social and preventive Medicine, University of Lausanne, Switzerland.  相似文献   
17.
We reviewed our experience with 11 consecutive combined latissimus dorsi and serratus anterior free-muscle transplantations from 1980 to 1990. All 11 flaps were successful and there was minimal morbidity. This combined muscle flap is ideal for soft-tissue coverage in extensive lower extremity wounds, in mutilating hand injuries with dorsal and palmar defects, and in situations when a long vascular pedicle is needed to get out of the "zone of injury."  相似文献   
18.
In two headache questionnaire surveys we inquired about the occurrence of headache in the mothers, fathers, siblings and children of the respondents. In total, 633 people completed valid questionnaires, 260 in the first survey and 373 in the second. The hypothesis was that familial headache occurrence would be positively associated with headache frequency. In each survey, the regression of headache frequency on the number of parents having headache was highly significant. Neither sex nor the sibling and children variables were significant predictors. In the cross-tabulations of the parental occurrence of headache with headache frequency we saw a clear "break-point" between the "no headache" and the headache frequency categories studied. For the final analyses the dichotomy "headache/no headache" was related in fourfold tables to headache occurrence in the father and the mother separately, and to the number of headache parents. The positive associations were not simply due to the large number of migraine cases since they remained after removing the migraineurs.  相似文献   
19.
BACKGROUND: Tobacco smoking is one of the main risk factors for oral, pharyngeal and oesophageal cancers in developed countries. Information on the role of the tar yield of cigarettes in upper digestive tract carcinogenesis is sparse and needs to be updated because the tar yield of cigarettes has steadily decreased over the last few decades. PATIENTS AND METHODS: We analysed two case-control studies, from Italy and Switzerland, conducted between 1992 and 1999, involving 749 cases of oral and pharyngeal cancer and 1770 controls, and 395 cases of squamous-cell oesophageal carcinoma and 1066 matched controls. Odds ratios (ORs) were estimated by unconditional multiple logistic regression models, including terms for age, sex, study centre, education and alcohol consumption. RESULTS: Based on the brand of cigarettes smoked for the longest time, the multivariate ORs for current smokers compared with never smokers were 6.1 for <20 mg and 9.8 for >or=20 mg tar for oral and pharyngeal neoplasms, and 4.8 and 5.4 for oesophageal cancer, respectively. For the cigarette brand smoked in the previous six months, the ORs for >or=10 mg compared with <10 mg were 1.9 for cancer of the oral cavity and pharynx and 1.8 for oesophageal cancer, after allowance for number of cigarettes and duration of smoking. CONCLUSIONS: The present study confirms the direct relationship between the tar yield of cigarettes and upper digestive tract neoplasms, and provides innovative information on lower tar cigarettes, which imply reduced risks compared with higher tar ones. However, significant excess risks were observed even in the lower tar category, thus giving unequivocal indications for stopping smoking as a priority for prevention of upper digestive tract neoplasms.  相似文献   
20.
OBJECTIVE: To analyse the prevalence of neural tube defects in small geographical areas and seek to explain any spatial variations with reference to environmental lead and deprivation. SETTING: The Fylde of Lancashire in the north west of England. DESIGN: Cases were ascertained as part of a prospective survey of major congenital malformations in babies born in the Fylde to residents there between 1957 and 1981. A matched case-control analysis used infants with cardiovascular system, alimentary tract, and urinary system malformations as controls. Conditional logistic regression was used to assess the effects of more than 10 micrograms/l lead in drinking water and the Townsend deprivation score. RESULTS: The prevalence of neural tube defects in 1957-73 was higher in Blackpool, Fleetwood, and North Fylde, whereas the three control groups showed no significant spatial variation. In 1957-81 mothers living in electoral wards with either a higher proportion of houses with more than 10 micrograms/l lead in the water or a higher deprivation score had a greater risk of having a baby with a neural tube defect. For spina bifida and cranium bifidum alone, this was also true. For anencephaly, deprivation was less important although the effect of lead was still seen. In some neural tube defects, lead may act independently of other possible factors associated with deprivation. It seemed unlikely that lead levels changed significantly during the survey. The percentage of houses with 10 micrograms/l or more of lead in the water in 1984-5 was similar to that found in Great Britain 10 years previously. CONCLUSION: There is evidence to suggest that lead is one cause of neural tube defects, especially anencephaly. This could link the known preventive actions of hard water and folic acid. Calcium is a toxicological antagonist of lead. One cause of a deficiency of folic acid is impaired absorption secondary to zinc deficiency, which may be produced or exacerbated by lead.  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