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   1601篇
  免费   171篇
耳鼻咽喉   6篇
儿科学   57篇
妇产科学   34篇
基础医学   164篇
口腔科学   19篇
临床医学   187篇
内科学   300篇
皮肤病学   11篇
神经病学   223篇
特种医学   57篇
外科学   251篇
综合类   56篇
预防医学   204篇
眼科学   7篇
药学   79篇
中国医学   3篇
肿瘤学   114篇
  2022年   11篇
  2021年   29篇
  2020年   20篇
  2019年   22篇
  2018年   25篇
  2017年   24篇
  2016年   26篇
  2015年   23篇
  2014年   36篇
  2013年   47篇
  2012年   64篇
  2011年   74篇
  2010年   33篇
  2009年   31篇
  2008年   73篇
  2007年   91篇
  2006年   70篇
  2005年   89篇
  2004年   66篇
  2003年   81篇
  2002年   74篇
  2001年   46篇
  2000年   42篇
  1999年   32篇
  1998年   20篇
  1997年   16篇
  1996年   14篇
  1995年   15篇
  1993年   19篇
  1992年   37篇
  1991年   49篇
  1990年   34篇
  1989年   34篇
  1988年   46篇
  1987年   43篇
  1986年   38篇
  1985年   42篇
  1984年   23篇
  1983年   23篇
  1982年   17篇
  1981年   16篇
  1979年   33篇
  1978年   13篇
  1977年   11篇
  1976年   8篇
  1975年   12篇
  1974年   7篇
  1973年   9篇
  1971年   11篇
  1968年   7篇
排序方式: 共有1772条查询结果,搜索用时 0 毫秒
1.
Twenty four volunteers who had been allergic to laboratory animals for some years were examined by means of a questionnaire paying particular attention to symptoms associated with rats and by serological and skin tests with extracts of rat urine (retrospective study). Nasal and eye symptoms were reported by 21 and 16 individuals respectively: 13 had asthma. Positive skin tests and high levels of specific IgE antibody to rat urine extract were found in 17 of the more severely affected individuals and this group included 12 of those with asthma. Latent periods of work with animals before symptoms appeared varied from 0.5 to 12 years. Also 148 individuals were studied during their first year of work with animals (prospective study). Symptoms developing during the year were reported by 15%, asthma by 2%. IgE antibody levels to rat urine were raised in 40% of affected and 6% of the unaffected individuals but there was no significant correlation between symptoms and either antibody levels or positive skin tests. Allergic symptoms developing during the first year of postemployment were, on the whole, much milder than those seen in the retrospective study. A tentative conclusion is that most individuals who become allergic to laboratory animals develop the condition in a mild form during their first year of employment but it appears probable that atopic individuals, although having an equal chance of developing allergy as compared with non-atopic individuals, may eventually progress to a more severe form of the disease.  相似文献   
2.
Determination of plasma delta-aminolaevulinic acid levels is of interest for the diagnosis of disorders of heme biosynthesis. We describe a reliable method for the determination of this parameter, based on a modification of the original method of Mauzerall and Granick. Analytical criteria are defined and the reference range used, established using data from 40 subjects, was 0.30 to 1.20 mumol/l. Results in patients with porphyria or lead poisoning and in those treated with haemodialysis or anticonvulsants indicate that this determination could be used principally in the diagnosis and management of acute porphyrias and in the early laboratory diagnosis of lead poisoning.  相似文献   
3.
4.
The outcome at three months after aneurysmal SAH in a group of older patients and a group of younger patients is compared. The patients were admitted within 72 hours of their SAH. Of 61 patients 66 years of age and older, comprising 13% of the whole patient group, 52% died, 12% remained dependent and 36% became independent. In the younger group, 55% had an independent outcome (p less than 0.01). In contrast to what we expected in the older patient group, not extracranial, but intracranial events (re-bleeds, infarcts, hydrocephalus) were by far the most frequent cause of deterioration.  相似文献   
5.
This study examined whether response to behavior modification with and without methylphenidate differed for children with attention-deficit/hyperactivity disorder (ADHD) and conduct problems (CP) depending on the presence of callous/unemotional (CU) traits. Participants were 37 children ages 7 to 12, including 19 with ADHD/CP-only and 18 with ADHD/CP-CU, referred to a university-based summer treatment program. Results showed that ADHD/CP-CU children had worse behavior in the behavior-therapy-only (BT-only) condition, especially on measures of CP, noncompliance, and rule violations, but these differences largely disappeared when medication was added to BT. Children with ADHD/CP-CU were also less likely to be normalized by treatment than were children with ADHD/CP-only. These findings, though tentative, suggest that children with ADHD/CP-CU may not show a sufficient positive response to BT alone and that the combination of medication and BT may be especially important for them.  相似文献   
6.
7.
8.
Familial lipoprotein lipase deficiency (FLD) is of particular interest to the French Canadian population of Québec since the largest concentration of homozygotes and carriers of this genetic disease in the world resides in this area. We have previously described a missense mutation (M-188) in the lipoprotein lipase (LPL) gene which was present in FLD patients belonging to different ancestries, including a number of French Canadians (Monsalve MV et al. J Clin Invest 1990: 86: 728-734). In the present report, we show that this mutation, although found in largest absolute numbers among French Canadians as compared to other groups in the world, accounts for only a small proportion (24%) of all the LPL mutant alleles in this population. The M-188 occurs either in the homozygote state or as a compound heterozygote with another LPL mutation. Analysis of geographic distribution indicates that the M-188 is more prevalent in western Québec, with the highest carrier rate in the Mauricie region. Genealogical reconstruction leads to the recognition of four founders for M-188, all emigrants from France to Québec in the 17th century.  相似文献   
9.
Summary A plasmid-like molecule was detected in a strain of the ascomycete Ceratocystis fimbriata Ell. & Halst., a pathogenic fungus of Populus spp. The DNA replicon, designated pFQ501, was found to have a linear structure with a length of 6.0 kb (3.9 × 106 daltons) and a density of 1.685 g/cc. This molecule was found to be associated with the mitochondria and was isolated from the gel; its restriction map was deduced from single and double digestions.  相似文献   
10.
Because body composition is altered during head-down bed rest (HDBR), body mass can not be used as an index of energy balance. Consequently diet allowances should not be based on body mass evolution but on fat mass changes. Though criticized, skinfold thickness (ST) is the costless, easiest and fastest method to use for such an objective. The aim of this study was to compare the percentage of body fat (%BF) estimated by ST with the isotope dilution of H218O. We compiled data from three HDBR campaigns, one on women (n=8) in November 1998 and two on the same men (n=8) in December 1997 (without countermeasure) and January 1998 (with thigh-cuffs countermeasure), according to a crossover design. Body composition was assessed before and after 6 days of HDBR. %BF was derived from the biceps, triceps, sub-scapular and sup-iliac ST according to Durnin and Wormersly (1974). Fat-free mass was measured on the same day by H218O dilution and fat mass was calculated by the difference with body mass and expressed as a percentage. Based on precision tests, the minimum measurable change by ST was 1.1%BF for single measurement point. Both intercepts (F 4,30=0.89, P=0.45) and slopes (F 4,30=0.74; P=0.57) of the ST versus dilution relationships were not affected by the periods (December vs January), experimental conditions (control vs HDBR vs HDBR + thigh cuffs) or sex allowing the derivation of a common relationship %BFst=0.94 × %BFdil (F 1,47=97.9, P<0.0001; non-significant intercept excluded) with a bias between methods of −1.7±2.0 %BF (95% CI: −5.8, 2.4 %BF). ST can be used to measure %BF during HDBR provided great care is placed on training and changes are higher than 1.1 %BF. If the method can be applied for in-flight energy balance monitoring given the high observed energy deficit, a tight monitoring of the individual nutritional status as needed during simulation appears, however, dubious based on this solely method.  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