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   862篇
  免费   67篇
  国内免费   1篇
耳鼻咽喉   2篇
儿科学   32篇
妇产科学   16篇
基础医学   115篇
口腔科学   19篇
临床医学   105篇
内科学   230篇
皮肤病学   14篇
神经病学   74篇
特种医学   26篇
外科学   124篇
综合类   1篇
预防医学   91篇
眼科学   8篇
药学   39篇
肿瘤学   34篇
  2023年   4篇
  2022年   13篇
  2021年   16篇
  2020年   17篇
  2019年   20篇
  2018年   33篇
  2017年   12篇
  2016年   21篇
  2015年   20篇
  2014年   23篇
  2013年   37篇
  2012年   50篇
  2011年   67篇
  2010年   34篇
  2009年   24篇
  2008年   62篇
  2007年   45篇
  2006年   51篇
  2005年   40篇
  2004年   40篇
  2003年   30篇
  2002年   35篇
  2001年   16篇
  2000年   32篇
  1999年   19篇
  1997年   5篇
  1992年   5篇
  1991年   13篇
  1990年   10篇
  1989年   11篇
  1988年   6篇
  1987年   12篇
  1986年   6篇
  1985年   6篇
  1984年   4篇
  1983年   8篇
  1978年   6篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1974年   3篇
  1972年   3篇
  1971年   3篇
  1970年   3篇
  1969年   5篇
  1968年   6篇
  1967年   4篇
  1966年   5篇
  1934年   4篇
  1933年   4篇
排序方式: 共有930条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Incidence of cervical cancer is high among Bolivian Andean women. Human papillomavirus (HPV) infection is known as the major risk factor of cervical cancer. The host immune system plays an important role in the outcome of HPV infection and associated malignancies. In order to study the immunogenetic background of Bolivian Andean women with regard to HPV infection status, we compared HLA class I and class II allele frequencies between 37 HPV positive and 68 HPV negative Bolivian women. Demographic variables, including distribution of Andean ethnicities, were similar in both groups. Comparison of HLA class I allele frequencies between both groups indicated no significant difference. In contrast, HLA class II DRB1*1602 allele, an Amerindian allele, was significantly higher in the HPV positive women compared with HPV negative controls (chi(2) = 5.2, p < 0.05, odds ratio = 3.17; 95% confidence interval = 1.4-8.8). HPV types present in the HPV positive group were HPV-18, -16, -31, -33, and -58. These results suggest that HLA class II DRB1*1602 may confer susceptibility to infection with genetically related HPV types. This is the first report of an HLA class II association with HPV infection in an Andean population.  相似文献   
5.
In the present report we describe the preparation of LC-6.2HCl, a soluble derivative of the synthetic bispyrazole LC-6. Because the latter was practically insoluble in aqueous and organic media, experiments which indicated that it had antiallergic activity were confined to in vivo studies following its oral administration. The availability of soluble LC-6.2HCl made it possible to administer the drug i.v. or i.p. Through these routes it exhibited greater antiallergic activity than by the oral route, as judged by lower ID50's and by the achievement of 100% PCA inhibition. The latter result had not previously been attained orally with the base. Furthermore, when injected i.v. or i.p. LC-6.2HCl showed prolonged inhibitory activity, a valuable attribute of the parent compound. The in vivo activity of the soluble salt, which we describe, further establishes the potential therapeutic value of the drug.  相似文献   
6.
A representative sample of 406 U.S. Navy commands, including all medical treatment facilities, was surveyed in 1990 about their activities and programs to prevent the use of tobacco and promote smoking cessation during the preceding year. The vast majority of Navy commands (86 percent) provided some type of tobacco cessation educational materials or programs. However, the most common activities typically were rated as only "somewhat useful" in helping to curb tobacco use. Almost one-half of all commands offered psychological or behavioral cessation programs. Survey respondents estimated that approximately one-third of those persons who attended such a program stopped their tobacco use and nearly one-half reduced their tobacco use as a result of the program. Over-the-counter smoking cessation aids were not widely available at Navy exchange stores, individual commands, or medical treatment facilities. Furthermore, only 61 percent of all commands reported that they had a written policy or instruction regarding tobacco use. Only about one-third of medical treatment facilities had a routine system for identifying tobacco users by glancing at their medical records. However, it was estimated that 80 percent of medical treatment facility physicians routinely asked their patients about their tobacco use. The authors discuss the need for a more active Navy approach in prevention and cessation efforts and a routine system for identifying tobacco users from their medical records. In addition, inequities in cessation efforts were found among command subgroups.  相似文献   
7.
OBJECTIVE: The purpose of this study was to describe the sociodemographic and serologic profiles in a first time consultant population at the Information and AIDS Prevention Center of Valencia (Spain). In addition, the HIV infection risk factors were analyzed. METHOD: A cross-sectional study was performed on 1,573 persons who consulted during the year 1995. Sociodemographic and infection risk practices data were recorded and serologic information about HIV, HBV and HCV infection were obtained. Exact binomial method with a 95% interval confidence was used to calculate infection prevalence and the chi square test to make comparisons between qualitative variables. RESULTS: Sex distribution was 66,1% males and 31,9% females; mean age was 29,01 (SD: 9.2) years. Sexual intercourse without condom (25.2%) and parenteral drug abusers (22.6%) were the more frequent risk groups seeking consultation about HIV infection. Global HIV infection prevalence was 12.7% (95% CI= 11,2-14,5%). Among HIV seropositive patients, sexual transmission accounted for 30.8% of cases, of which 69.4% were heterosexual relations. The HIV infection prevalence for different risk groups were the following: parenteral drug abusers 36.8% (95% CI= 31,7-42%), heterosexual intercourse with an HIV-infected partner 24.1% (95% CI= 17,1-32,2%) and homosexual intercourse between men 9,5% (95% CI= 5,8-14,5%). HCV antibody prevalence for parenteral drug abusers was 81.2% (95% CI= 76,7-85,1%). Risk practices with a statistically significant association with HIV infection were: being an injecting drug abuser, as well as having an HIV infected and/or a injecting drug abuser partner. CONCLUSIONS: Drug parenteral abusers are still the target population for prevention programs. Data suggest that prevention and sexual education programs must continue. The main effort should be focused on the young population and on sexual partners of injecting drug abusers and/or HIV seropositive partners.  相似文献   
8.
Summary The influence of respiratory and metabolic acid-base alterations on the myocardial sensitivity to catecholamines was studied in the isolated rat atria. The ability of noradrenaline for increasing the atrial rate was enhanced during alkalosis and conversely, it was decreased by acidosis. These changes in sensitivity shifted the concentration-effect curve for noradrenaline to the right by about 0.5 log unit when the pH was lowered from 7.60 to 7.00. No changes in the maximum attainable response were detected. Essentially the same shifts of the concentration-effect curves were obtained with changes in pH brought about by altering the pCO2 or at constant pCO2. The decrease in the pH produced a similar shift to the right of the concentration-effect curve for isoprenaline, after the extraneuronal uptake inhibition by hydrocortisone and also in atria tissue with low content of endogenous noradrenaline (reserpine-pretreated and newborn rats). The ability of isoprenaline for increasing cyclic AMP levels in atrial tissue was also enhanced by alkalosis and decreased by acidosis. However, the shift to the right of the concentration-effect curve for cyclic AMP induced by the decrease in the pH was greater than the shift detected in the chronotropic-effect curve. In addition a decrease in the maximum increment of cyclic AMP was detected under acidosis, in spite of equal maximal chronotropic response.Our results support the hypothesis that the alterations in the sensitivity to catecholamines induced by the changes in pH are not due to a release of endogenous noradrenaline nor to alterations of the mechanisms which remove catecholamines from the biophase. The fact that cyclic AMP response to catecholamines was also reduced by acidosis strongly suggests that the mechanism(s) involved is located in the earlier steps of the events leading to the chronotropic effect of the -agonists.  相似文献   
9.
Distinct patterns of glomerular disease in Lima, Peru   总被引:2,自引:0,他引:2  
AIM: We performed both a retrospective and prospective study to elucidate the types of glomerular diseases present in adults in Lima, Peru. MATERIAL AND METHODS: In the retrospective study, we analyzed 1,263 renal biopsies over a 10-year period (1985 -1995) that were processed at a central reference renal pathology laboratory in Lima. 101 cases were examined in the prospective study. RESULTS: The most common glomerular diseases observed were those due to systemic lupus erythematosus (30.2%), membranoproliferative glomerulonephritis (MPGN, 14.8%), and focal and segmental glomerulosclerosis (FSGS, 13.9%). Although mesangial-proliferative nephritis was observed in 9.5% of cases, IgA nephropathy was rare (0.9%). Examination of the year to year frequency showed that MPGN has tended to decrease in frequency with time whereas FSGS has been increasing. Although there is known to be a high frequency of infections in Peru, only 4.2% of the cases in the retrospective study were associated with infection. Furthermore, in the prospective study, only one case of hepatitis C and no cases of hepatitis B viral infection were detected, including in the 11 cases of MPGN observed. CONCLUSION: We conclude that the epidemiology of glomerular disease in Lima, Peru, is distinct from most areas of the world, but has similarities to certain regions in Africa, in that MPGN is common whereas IgA nephropathy appears to be rare. Further studies are necessary to elucidate the reasons why the patterns of glomerular disease are different from that observed in other parts of the world.  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