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   426516篇
  免费   19804篇
  国内免费   1136篇
耳鼻咽喉   3917篇
儿科学   13342篇
妇产科学   7604篇
基础医学   49498篇
口腔科学   6687篇
临床医学   37670篇
内科学   83969篇
皮肤病学   4123篇
神经病学   40587篇
特种医学   17282篇
外国民族医学   13篇
外科学   67363篇
综合类   5836篇
一般理论   324篇
预防医学   39128篇
眼科学   9428篇
药学   26524篇
  5篇
中国医学   986篇
肿瘤学   33170篇
  2023年   1239篇
  2022年   2048篇
  2021年   5542篇
  2020年   3321篇
  2019年   5402篇
  2018年   27127篇
  2017年   21255篇
  2016年   23706篇
  2015年   6768篇
  2014年   9453篇
  2013年   12698篇
  2012年   24874篇
  2011年   39345篇
  2010年   28635篇
  2009年   20664篇
  2008年   35522篇
  2007年   38534篇
  2006年   18073篇
  2005年   19583篇
  2004年   19693篇
  2003年   19440篇
  2002年   16675篇
  2001年   2609篇
  2000年   2236篇
  1999年   2681篇
  1998年   3331篇
  1997年   2822篇
  1996年   2341篇
  1995年   2260篇
  1994年   1896篇
  1993年   1678篇
  1992年   1495篇
  1991年   1432篇
  1990年   1317篇
  1989年   1274篇
  1988年   1213篇
  1987年   1195篇
  1986年   1157篇
  1985年   1159篇
  1984年   1398篇
  1983年   1246篇
  1982年   1455篇
  1981年   1377篇
  1980年   1253篇
  1979年   840篇
  1978年   864篇
  1977年   727篇
  1976年   700篇
  1975年   572篇
  1974年   600篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
981.
In some patients with mental retardation, a Q-tip pap smear obtained blindly from the upper vagina may be the only cytologic smear obtainable without subjecting the patient to heavy sedation or to examination under anesthesia. The efficacy of blind Q-tip smears has not been previously determined. Of 31 Q-tip smears obtained from patients with CIN, the Q-tip smear identified the abnormality in 10 (32%) patients. For those patients who will not submit to examination without anesthesia or sedation, routine screening with multiple smears, obtained on an annual basis has the potential to identify many cases of CIN which otherwise would not be identified at all, and in certain patients, this method outweighs the risks of heavy sedation or general anesthesia. Because of the greatly reduced sensitivity of the Q-tip pap, every effort should be made to help the patient and/or her family or guardian to understand the implications and risks of this method. However, if an examination under anesthesia is performed for other indications, a complete gynecologic examination and a direct smear should be obtained at that time.  相似文献   
982.
In 1998, the New York City Department of Health and the Mayor’s Office of Emergency Management began monitoring the volume of ambulance dispatch calls as a surveillance tool for biologic terrorism. We adapted statistical techniques designed to measure excess influenza mortality and applied them to outbreak detection using ambulance dispatch data. Since 1999, we have been performing serial daily regressions to determine the alarm threshold for the current day. In this article, we evaluate this approach by simulating a series of 2,200 daily regressions. In the influenza detection implementation of this model, there were 71 (3.2%) alarms at the 99% level. Of these alarms, 64 (90%) occurred shortly before or during a period of peak influenza in each of six influenza seasons. In the bioterrorism detection implementation of this methodology, after accounting for current influenza activity, there were 24 (1.1%) alarms at the 99% level. Two occurred during a large snowstorm, 1 is unexplained, and 21 occurred shortly before or during a period of peak influenza activity in each of six influenza seasons. Our findings suggest that this surveillance system is sensitive to communitywide respiratory outbreaks with relatively few false alarms. More work needs to be done to evaluate the sensitivity of this approach for detecting nonrespiratory illness and more localized outbreaks.  相似文献   
983.
Driven by research findings regarding the positive relationship between training and enhancement of services, as well as literature on adult learning, the New England Head Start Teaching Center (NEHSTC) was created in 1992 to test the efficacy of participatory, hands-on training. The purpose of this paper is to examine the outcome evaluation results from 4 years of training at the NEHSTC, 1 of 14 federally funded sites, as well as to discuss the implications for delivering this type of participatory training throughout Head Start. Findings suggest that the NEHSTC was successful in implementing high quality, participatory training within the context of an ongoing Head Start program. Head Start staff who participated in the NEHSTC trainings demonstrated gains in knowledge, skills, and expertise compared to similar Head Start employees who did not receive training. Results also reveal a sustained effect of training over time, with NEHSTC participants continuing to demonstrate enhanced knowledge and skills 6 months after training. Similar positive outcomes of training were found for staff with varying levels of experience and holding different Head Start positions. Thus the participatory, hands-on training implemented by the NEHSTC was found to produce positive and lasting outcomes for diverse Head Start staff. An effective and cost efficient model of training Head Start personnel is particularly relevant and timely as Head Start strives to establish universal quality and expansion of services in the 21st Century. The findings are also relevant for improving the quality of all early care and education programs.  相似文献   
984.
A 438 basepair intron 1 sequence adjacent to exon 2 in the human major histocompatibility complex DQA1 gene defined 16 allelic variants in 69 individuals from wide ethnic backgrounds. In contrast, the most variable coding region spanned by the 247 basepair exon 2 defined 11 allelic variants. Our phylogenetic human intron 1 tree derived by the Bootstrap algorithm reflects the same relative allelic relationships as the reported DQA1 exon 2 tree [Gyllensten and Erlich, Hum Immunol 36:1–10, 1989]. Thus 3′ DQA1 intron 1 and exon 2 have cosegregated since divergence of the human races. Comparison of human alleles to a Rhesus monkey DQA1 first intron sequence found only 10 nucleotide substitutions unique to Rhesus, with the other 428 positions (98%) found in at least one human allele. This high degree of homology reflects the evolutionary stability of intron sequences since these two species diverged over 20 million years ago. Because more intron 1 alleles exist than exon 2 alleles, these polymorphic introns can be used to improve tissue typing for transplantation, paternity testing, and forensics and to derive more complete phylogenetic trees. These results suggest that introns represent a previously underutilized polymorphic resource. © 1994 Wiley-Liss, Inc.  相似文献   
985.
An important methodological issue in depressionanalog research is whether individuals who scoreextremely low on self-report measures like the BeckDepression Inventory (BDI) should be included innondepressed control groups. Joiner, Schmidt, and Metalsky(1994) found that college students with BDI scores of 0or 1 evidenced a fake-good test taking style as measuredby the MMPI validity scales. The present study investigated whether very low BDI scores (BDI= 0 or 1; n = 21) might be associated with an elevatedpositive mood state, extreme optimism, positiveattributional style or social desirability. Resultsindicated that the very low scoring BDI subjects scoredhigher on social desirability than the low scoring group(BDI = 2 9, n = 63). Significant differences on mood,symptom and cognitive measures disappeared when social desirability was entered as a covariate.Findings support Kendall, Hollon, Beck, Hammen, andIngram's (1987) recommendation that subjects who score0 or 1 on the BDI should be excluded from a nondepressed control group.  相似文献   
986.
987.
Neuropsychologists often diagnose cerebral dysfunction based, in part, on marked variation in an individual's cognitive test performance. However, little is known about what constitutes the normal range of intraindividual variation. In this study, after excluding 54 individuals with significant health problems, we derived 32 z-transformed scores from 15 tests administered to 197 adult participants in a study of normal aging. The difference between each person's highest and lowest scores was computed to assess his or her maximum discrepancy (MD). The resulting MD values ranged from 1.6 to 6.1 meaning that the smallest MD shown by any person was 1.6 standard deviations (SDs) and the largest MD shown by any person was 6.1 SDs. Sixty-six percent of participants produced MD values that exceeded 3 SDs. Eliminating each person's highest and lowest test scores decreased their MDs, but 27% of the participants still produced MD values exceeding 3. Although MD values appeared to increase with age, adjusting test scores for age, which is standard in clinical practice, did not correct for this. These data reveal that marked intraindividual variability is very common in normal adults, and underscore the need to base diagnostic inferences on clinically recognizable patterns rather than psychometric variability alone.  相似文献   
988.
The present study evaluated curiosity and anger as motives among childhood firesetters. Parents of 133 firesetters (ages 6-13) completed the Fire Incident Analysis (FIA) to permit classification of the children as high and low on each of these two primary motives and to document details of the child's most serious incident within the past 12 months. The children were compared on measures of child dysfunction and firesetting history. An effect of Curiosity was found on measures of psychopathology, firesetting risk, and fire involvement, whereas an effect of Anger was found on measures of firesetting risk and the behavioral correlates of individual incidents. The results clarify the role of child motive in understanding firesetting involvement.  相似文献   
989.
990.
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