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   2069篇
  免费   221篇
  国内免费   69篇
耳鼻咽喉   3篇
儿科学   87篇
妇产科学   21篇
基础医学   275篇
口腔科学   61篇
临床医学   260篇
内科学   471篇
皮肤病学   5篇
神经病学   130篇
特种医学   128篇
外科学   211篇
综合类   51篇
预防医学   352篇
眼科学   11篇
药学   194篇
中国医学   2篇
肿瘤学   97篇
  2021年   31篇
  2020年   19篇
  2019年   34篇
  2018年   32篇
  2017年   23篇
  2016年   27篇
  2015年   24篇
  2014年   44篇
  2013年   56篇
  2012年   86篇
  2011年   86篇
  2010年   47篇
  2009年   32篇
  2008年   61篇
  2007年   96篇
  2006年   64篇
  2005年   64篇
  2004年   65篇
  2003年   75篇
  2002年   60篇
  2001年   61篇
  2000年   56篇
  1999年   56篇
  1998年   45篇
  1997年   42篇
  1996年   41篇
  1995年   35篇
  1994年   35篇
  1993年   24篇
  1992年   54篇
  1991年   50篇
  1990年   61篇
  1989年   71篇
  1988年   64篇
  1987年   66篇
  1986年   59篇
  1985年   51篇
  1984年   53篇
  1983年   43篇
  1982年   24篇
  1981年   24篇
  1980年   19篇
  1979年   33篇
  1978年   26篇
  1977年   24篇
  1976年   26篇
  1975年   21篇
  1974年   23篇
  1973年   22篇
  1972年   16篇
排序方式: 共有2359条查询结果,搜索用时 10 毫秒
1.
To determine the potential effect of screening on referral patterns, an adult population sample (4,404 men, 5,164 women, 20-69 years of age) was systematically recruited and screened for hypercholesterolemia and then analyzed by different cholesterol referral recommendations. Using levels suggested by the Lipid Research Clinics Coronary Primary Prevention Trial (greater than or equal to 265 mg/dL), 7.3% of men and 5.8% of women would be referred for follow-up. With the suggested recommendations of the National Cholesterol Education Program (NCEP), (greater than or equal to 200 mg/dL), 49.2% of men and 40.2% of women would be referred. The use of age-related definitions of the NIH Consensus Conference on Lipid Lowering results in 28.0% referrals in men and 21.8% in women. From this population, hypercholesterolemia subjects (greater than or equal to 265 mg/dL at screening; n = 624) were invited for a second cholesterol determination (58% returned), which found 36% below the 265 mg/dL level. Population screening for cholesterol is likely to produce large numbers of patients for follow-up, with the actual numbers strongly dependent on cutoff levels and age-sex distributions. Referral and follow-up of these patients may place a significant load on an unprepared health care community.  相似文献   
2.
3.
Bilateral ulnar agenesis is a rare abnormality. A total of 36 cases are analyzed: 35 of these are documented in the literature and 1 stillborn male is presented in this study. Most patients had one of the three conditions: Al-Awadi/Raas-Rothschild syndrome, syndrome of ulnar aplasia with split hand/split foot deformity, or the Brachmann—de Lange syndrome. Fifty percent of all cases with bilateral ulnar agenesis were associated with lower limb defects and these cases, for the most part, also belonged to the aforementioned syndromes. Nonskeletal, internal organ malformations were identified in 34% of all patients. Nine patients presented with isolated bilateral ulnar agenesis. The Al-Awadi/Raas-Rothschild syndrome and the split hand/split foot deformity are heritable disorders. There was no evidence for genetic etiology in most of the other cases. Bilateral ulnar agenesis in our fetus was part of the Brachmann—de Lange syndrome with associated cardiac defect, diaphragmatic hernia, and umbilical artery agenesis.  相似文献   
4.
5.
6.
Comparison of the mutagenicity of nine isomeric benzo(a)pyrenyl [B(a)P] phenols conjugated with either sulfate or glucuronide was carried out using strain Salmonella typhimurium TA98. Of the nine conjugates tested, only B(a)P-1-sulfate was mutagenic. Accordingly, the mutagenicity of B(a)P-1-sulfate was compared with that of B(a)P and 1-hydroxybenzo(a)pyrene [B(a)P-1-OH] in the presence and absence of rat lung S9 and Aroclor-induced liver S9 with and without an NADPH-generating system. B(a)P-1-sulfate was slightly mutagenic, whereas B(a)P and the 1-hydroxy derivative were nonmutagenic when S9 fractions and NADPH were omitted. Addition of induced liver S9 with NADPH caused mutagenicity with B(a) -1-OH greater than B(a)P greater than B(a)P-1-sulfate. B(a)P-1-sulfate was the only mutagenic species when lung S9 was added. This mutagenicity did not require NADPH. Sodium sulfite, an inhibitor of arylsulfatase, decreased the mutagenicity of B(a)P-1-sulfate. These data suggest that a unique mutagenic species is generated from B(a)P-1-sulfate via arylsulfatase in rat lung.  相似文献   
7.
The adult stage of Nippostrongylus brasiliensis, a strongyloid parasite of the gastrointestinal tract of rats, released a product during in vitro culture which functionally inhibited platelet-activating factor (PAF), measured by its ability to mediate platelet aggregation. The extent of inhibition was proportional to the concentration of excretory/secretory (ES) products and the duration of preincubation with PAF prior to the assay of biological activity. The inhibitory activity was heat labile and was specific for PAF, as incubation of ES products with thrombin showed no diminution of platelet aggregation. Experiments using radiolabelled preparations of PAF demonstrated that the acetyl group esterified at the sn-2 position of the glycerol backbone was liberated on incubation with ES products, indicative of an acetylhydrolase activity. This activity was susceptible to inhibition by DFP, partial inhibition by eserine, but was resistant to PMSF and TPCK at concentrations which inhibit serine proteases.  相似文献   
8.
9.
Developmental data were abstracted from medical records on 50 trisomy 18 individuals ranging in age from 1 to 232 months and 12 trisomy 13 individuals ranging in age from 1 to 130 months. Data on the age when trisomy 18 and trisomy 13 children achieved developmental skills were collected from a larger group of 62 trisomy 18 individuals and 14 trisomy 13 individuals whose families filled out parent questionnaires. Developmental quotient (DQ), defined as developmental age divided by chronological age, averaged 0.18 for trisomy 18 and 0.25 for trisomy 13. There was a dramatic drop in DQ from infancy to later childhood. The highest DQs and the greatest variation in DQs were in the first 2–3 years of life. Developmental ages in 7 skill areas were significantly different, with daily living and receptive language having the highest values and motor and communication skills having the lowest. When chronological age was taken into account, there was no significant difference in DQs in the same 7 skill areas, although there was a trend that was similar to the pattern of differences with developmental age. Older children could use a walker, understand words and phrases, use a few words and/or signs, crawl, follow simple commands, recognize and interact with others, and play independently. Walking and some toileting skills were also reported for trisomy 13. Although individuals with trisomy 18 and trisomy 13 were clearly functioning in the severe to profound developmentally handicapped range, they did achieve some psychomotor maturation and always continued to learn. © 1994 Wiley-Liss, Inc.  相似文献   
10.
Trends in poverty and changes in service provision are combining to make the promotion of health in poverty a particular challenge to health and welfare practitioners. The evidence suggests that practitioner groups have failed to respond adequately to this challenge. Factors concerned with professional perceptions of poverty, the nature of qualifying and post-qualifying education and the difficulties associated with taking research into practice all appear, in some way, to contribute to practitioners’ failure to incorporate a poverty perspective in their work. A team training approach appears to offer one way forward in the practice-setting. Using a team training approach, the‘Health Promotion in Poverty Project’ has sought to enable the lessons learnt from the broad base of poverty theory and research to be used by practitioners to build responsive and integrated support strategies for low-income families with dependent children.  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