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   1146篇
  免费   81篇
  国内免费   3篇
耳鼻咽喉   13篇
儿科学   20篇
妇产科学   22篇
基础医学   133篇
口腔科学   12篇
临床医学   128篇
内科学   171篇
皮肤病学   24篇
神经病学   52篇
特种医学   65篇
外科学   225篇
综合类   29篇
一般理论   2篇
预防医学   122篇
眼科学   4篇
药学   81篇
中国医学   3篇
肿瘤学   124篇
  2023年   12篇
  2021年   22篇
  2020年   15篇
  2019年   22篇
  2018年   20篇
  2017年   11篇
  2016年   12篇
  2015年   9篇
  2014年   29篇
  2013年   40篇
  2012年   42篇
  2011年   44篇
  2010年   21篇
  2009年   19篇
  2008年   46篇
  2007年   46篇
  2006年   50篇
  2005年   44篇
  2004年   52篇
  2003年   42篇
  2002年   47篇
  2001年   41篇
  2000年   44篇
  1999年   31篇
  1998年   27篇
  1997年   16篇
  1996年   21篇
  1995年   12篇
  1994年   15篇
  1992年   21篇
  1991年   17篇
  1990年   14篇
  1989年   25篇
  1988年   20篇
  1987年   22篇
  1986年   17篇
  1985年   27篇
  1984年   17篇
  1983年   12篇
  1981年   10篇
  1980年   10篇
  1979年   18篇
  1977年   14篇
  1975年   12篇
  1972年   9篇
  1971年   17篇
  1970年   11篇
  1969年   13篇
  1968年   7篇
  1967年   8篇
排序方式: 共有1230条查询结果,搜索用时 15 毫秒
1.
2.
ABSTRACT

Adolescents and young adults smoke waterpipe tobacco (WT) and cigarillos, at least in part, based on erroneous beliefs that these products are safer than cigarettes. To address this challenge, we used a systematic, three-phase process to develop a health communication campaign to discourage WT and cigarillo smoking among at-risk (tobacco users and susceptible non-users) 16- to 25-year-olds. In Phase 1, we used a national phone survey (N = 896) to determine salient message beliefs. Participants reported constituents (i.e., harmful chemicals) emitted by the products were worrisome. In Phase 2, we developed and evaluated four message executions, with varying imagery, tone, and unappealing products with the same constituents, using focus groups (N = 38). Participants rated one execution highly, resulting in our development of a campaign where each message: (1) identified a tobacco product and constituent in the smoke; (2) included an image of an unappealing product containing the constituent (e.g., pesticides, gasoline) to grab attention; and (3) used a humorous sarcastic tone. In Phase 3, we tested the campaign messages (17 intervention and six control) with a nationally representative online survey (N = 1,636). Participants rated intervention and control messages highly with few differences between them. Exposure to messages resulted in significant increases in all risk beliefs from pre to post (< 0.05). For WT, intervention messages increased beliefs about addiction more than control messages (p < 0.05). This systematic, iterative approach resulted in messages that show promise for discouraging WT and cigarillo use.  相似文献   
3.
4.
BACKGROUND: We have seen several patients with itchy lichenified plaques located bilaterally on the elbows and/or knees and have named this condition 'psoriatic neurodermatitis' (PN). OBJECTIVE: The purpose of this study was to compare clinical and histopathological characteristics of these patients to those of patients with typical lichen simplex chronicus (LSC). METHODS: Nineteen patients with PN and 34 patients with typical LSC were included. Besides clinical dermatological evaluation, the prick test was carried out on 49 patients; the Phadiatop test on 40 patients; the patch test with European standard series on 47 patients; histopathological evaluation on 39 patients; and clinical psychiatric examination on 38 patients. RESULTS: Almost exclusively, PN was seen in females and was located on the extremities. It caused more plaques than typical LSC did. In PN, the plaques were smaller, sharper, more keratotic and less excoriated, and had fewer lichenoid papules around them. Itching was usually more severe in the evening, while resting and in a hot environment in typical LSC, but not in PN. In plaques of PN, microabscesses in the horny layer, hypogranulosis, regular acanthosis and thinning of the suprapapillary plates were more frequent, and hyperpigmentation in the basal layer was less. In patients with PN, depressive disorder was found more frequently; and generalized anxiety disorder or psychosomatic characteristics, less. There were no significant differences in the results of prick, Phadiatop and patch tests between patients with PN and those with typical LSC. CONCLUSION: In our opinion, it is most likely that the so-called PN is itchy psoriasis superimposed by LSC.  相似文献   
5.
Analyses of losses of heterozygosity and linkage studies have implicated a gene(s) on chromosome 17q in the genesis of sporadic and early-onset familial breast carcinomas, respectively. To define the critical region of 17q, we examined DNAs from a series of 20 sporadic breast carcinomas and corresponding blood samples for allelic losses of chromosome 17q using microsatellite length polymorphisms. With these highly informative markers (average heterozygosity, 0.73), we observed frequent deletions of 17q at several loci. We found that D17S250 was deleted in 50% (7 of 14), THRA1 in 79% (11 of 14), D17S579 in 59% (11 of 19), NME1 in 29% (5 of 17), MPO in 36% (4 of 11), and GH in 25% (4 of 16) in the tumor set examined. A common region of deletion was found that was flanked by D17S250 to D15S579. These markers have recently been localized to a 6-cM interval of proximal chromosome 17q in bands 17q11.2-q21 and map within the region of the early-onset familial breast cancer locus, implying that the same gene or genes may be involved in both sporadic and familial breast tumors. Thyroid hormone receptor alpha and retinoic acid receptor alpha are two potential candidate genes in this region.  相似文献   
6.
Patients with clinical signs of alpha 1-antitrypsin deficiency in the neonatal period usually present with prolonged obstructive jaundice. We report a patient with alpha 1-antitrypsin deficiency who presented with gallbladder enlargement in the neonatal period. This gallbladder enlargement may be due to cystic duct hypoplasia or atresia, which has been reported in association with alpha 1-antitrypsin deficiency. The diagnosis of alpha 1-antitrypsin deficiency should be considered in neonates with gallbladder enlargement and prolonged obstructive jaundice.  相似文献   
7.
This study is part of a programme to elicit and examine community preferences for health care in different contexts. Data were obtained from a group of predominantly Australian health care decision-makers. A short questionnaire contained six valuation questions and four demographic questions. The six valuation questions posed choices where equal health gains were to be allocated to different population groups based upon: age; sex; current health; socio-economic status; across time; and across different numbers of individuals. The results provide some evidence that respondents were prepared to discriminate between health gains derived in different contexts especially where health gains were to be allocated between groups of different health status and over time. Further research is planned and the possible implications for health policy, and in particular for resource allocation in health care, are briefly discussed.  相似文献   
8.
The clinical signs and pathological lesions which developed in various ages of cattle experimentally infected intranasally with the "Strichen" strain of IBR virus were similar to, but generally milder than, those of the field disease. The clinical signs were most severe 4 days after infection and had almost wholly regressed after 12 days. Serum neutralizing antibodies were detected in every animal. Virus was isolated from nasal and ocular swabs for up to 13 days and 10 days, respectively, after infection. The clinical signs and the pathological lesions were more severe in the younger animals.  相似文献   
9.
Hepatitis E virus (HEV) is endemic in many developing and some industrialized countries. It has been hypothesized that animals may be the source of infection. The recent identification of swine HEV in U.S. pigs and the demonstration of its ability to infect across species have lent credence to this hypothesis. To assess the potential risk of zoonotic HEV infection, we tested a total of 468 veterinarians working with swine (including 389 U.S. swine veterinarians) and 400 normal U.S. blood donors for immunoglobulin G anti-HEV. Recombinant capsid antigens from a U.S. strain of swine HEV and from a human HEV strain (Sar-55) were each used in an enzyme-linked immunosorbent assay. The anti-HEV prevalence assayed with the swine HEV antigen showed 97% concordance with that obtained with the human HEV antigen (kappa = 92%). Among the 295 swine veterinarians tested from the eight U.S. states (Minnesota, Indiana, Nebraska, Iowa, Illinois, Missouri, North Carolina, and Alabama) from which normal blood donor samples were available, 26% were positive with Sar-55 antigen and 23% were positive with swine HEV antigen. In contrast, 18% of the blood donors from the same eight U.S. states were positive with Sar-55 antigen and 17% were positive with swine HEV antigen. Swine veterinarians in the eight states were 1.51 times more likely when tested with swine HEV antigen (95% confidence interval, 1.03 to 2.20) and 1.46 times more likely when tested with Sar-55 antigen (95% confidence interval, 0.99 to 2.17) to be anti-HEV positive than normal blood donors. We did not find a difference in anti-HEV prevalence between veterinarians who reported having had a needle stick or cut and those who had not or between those who spent more time (> or = 80% of the time) and those who spent less time (< or = 20% of the time) working with pigs. Similarly, we did not find a difference in anti-HEV prevalence according to four job categories (academic, practicing, student, and industry veterinarians). There was a difference in anti-HEV prevalence in both swine veterinarians and blood donors among the eight selected states, with subjects from Minnesota six times more likely to be anti-HEV positive than those from Alabama. Age was not a factor in the observed differences from state to state. Anti-HEV prevalence in swine veterinarians and normal blood donors was age specific and paralleled increasing age. The results suggest that swine veterinarians may be at somewhat higher risk of HEV infection than are normal blood donors.  相似文献   
10.
1. The effect of semistarvation (sufficient to produce a loss of 18-28% of initial body weight) on the active transport of D-glucose and L-histidine by the rat, the guinea-pig and the golden hamster has been investigated by the use of sacs of everted small intestine (from upper jejunum to lower ileum).2. In the rat and the guinea-pig the dietary restriction resulted in increased active transport in all regions of the small intestine. In contrast, it caused no alteration in active transport in the hamster.3. The response in the rat was most impressive in the middle-to-lower ileum during D-glucose uptake. Whereas normal sacs from this area appeared unable to move the sugar against its concentration gradient, sacs from semistarved rats did so quite well.4. Although there was a considerable loss (24-29%) of intestinal dry weight in all three species when the food intake was reduced, shortening of the small intestine was not detectable in the guinea-pig or the hamster and was present to only a minor extent in the rat.5. Evidence is presented indicating that the enhanced active transport is not merely a reflexion of the thinning of the intestinal wall and that it occurs during complete as well as in partial starvation.  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