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   52827篇
  免费   5588篇
  国内免费   91篇
耳鼻咽喉   709篇
儿科学   1504篇
妇产科学   1328篇
基础医学   8041篇
口腔科学   1241篇
临床医学   6980篇
内科学   10223篇
皮肤病学   650篇
神经病学   4207篇
特种医学   1729篇
外国民族医学   1篇
外科学   7224篇
综合类   1007篇
一般理论   36篇
预防医学   5313篇
眼科学   834篇
药学   4257篇
中国医学   64篇
肿瘤学   3158篇
  2022年   375篇
  2021年   856篇
  2020年   520篇
  2019年   911篇
  2018年   1065篇
  2017年   746篇
  2016年   909篇
  2015年   936篇
  2014年   1352篇
  2013年   1971篇
  2012年   2701篇
  2011年   2822篇
  2010年   1569篇
  2009年   1418篇
  2008年   2428篇
  2007年   2473篇
  2006年   2418篇
  2005年   2415篇
  2004年   2270篇
  2003年   2191篇
  2002年   2166篇
  2001年   1625篇
  2000年   1639篇
  1999年   1432篇
  1998年   694篇
  1997年   572篇
  1996年   477篇
  1995年   508篇
  1994年   472篇
  1993年   435篇
  1992年   1149篇
  1991年   1076篇
  1990年   1060篇
  1989年   970篇
  1988年   886篇
  1987年   913篇
  1986年   883篇
  1985年   904篇
  1984年   733篇
  1983年   627篇
  1982年   449篇
  1981年   377篇
  1980年   378篇
  1979年   586篇
  1978年   453篇
  1977年   376篇
  1976年   383篇
  1974年   387篇
  1973年   337篇
  1972年   342篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To develop and validate a short form version of the Endometriosis Health Profile-30 questionnaire which consists of a 30-item core questionnaire and a 23 item modular questionnaire. METHODS: Three studies were carried out to develop the Endometriosis Health Profile-5. Study 1: a short form version of the Endometriosis Health Profile-30 core questionnaire was developed. Study 2: the results were verified in a new data set. Study 3: a short form version of the 23 item modular questionnaire was produced. The modular questionnaire contains six dimensions which may not be applicable to every woman with endometriosis and is used to supplement the five scales on the core questionnaire when required. RESULTS: The final instrument contained 11 items: five items from the core questionnaire and six items from the modular questionnaire. The 95% confidence intervals for Study 1 indicated that the scale scores overlapped with each item score and were confirmed in the second analysis (study 2). Each item was most highly correlated to its parent scale and less with the remaining four core questionnaire scales which was verified in study 2. In both studies all correlations were significant at the 0.01 level (two tailed test). CONCLUSION: The Endometriosis Health Profile-5 is a reliable and valid short form questionnaire which can also be supplemented with a short form version of the modular questionnaire when required. It will be especially useful in clinical settings where a short and economical endometriosis health status measure is required.  相似文献   
992.
OBJECTIVE: This study evaluated the influence of a multiple injury control intervention on injury and physical fitness outcomes among soldiers attending United States Army Ordnance School Advanced Individual Training. METHODS: The study design was quasiexperimental involving a historical control group (n = 2559) that was compared to a multiple intervention group (n = 1283). Interventions in the multiple intervention group included modified physical training, injury education, and a unit based injury surveillance system (UBISS). The management responsible for training independently formed an Injury Control Advisory Committee that examined surveillance reports from the UBISS and recommended changes to training. On arrival at school, individual soldiers completed a demographics and lifestyle questionnaire and took an army physical fitness test (APFT: push-ups, sit-ups, and two mile run). Injuries among soldiers were tracked by a clinic based injury surveillance system that was separate from the UBISS. Soldiers completed a final APFT eight weeks after arrival at school. RESULTS: Cox regression (survival analysis) was used to examine differences in time to the first injury while controlling for group differences in demographics, lifestyle characteristics, and physical fitness. The adjusted relative risk of a time loss injury was 1.5 (95% confidence interval 1.2 to 1.8) times higher in the historical control men and 1.8 (95% confidence interval 1.1 to 2.8) times higher in the historical control women compared with the multiple intervention men and women, respectively. After correcting for the lower initial fitness of the multiple intervention group, there were no significant differences between the multiple intervention and historical control groups in terms of improvements in push-ups, sit-ups, or two mile run performance. CONCLUSIONS: This multiple intervention program contributed to a reduction in injuries while improvements in physical fitness were similar to a traditional physical training program previously used at the school.  相似文献   
993.
OBJECTIVES: Within a clinic serving disadvantaged children, 1) to evaluate a multifaceted quality improvement (QI) project to improve immunization (IZ) up-to-date (UTD) rates and 2) to assess the efficacy of IZ reminder/recall performed following QI. METHODS: A year-long QI project followed by a trial of reminder/recall. QI interventions were targeted at previously identified barriers to IZ and were designed specifically to improve the efficacy of reminder/recall. QI interventions were designed to 1) increase the use of medical record releases to document IZs received elsewhere; 2) improve the accuracy of parental contact information; and 3) reduce missed opportunities by utilizing chart prompts, provider education, and provider reminders. Following QI, we conducted a randomized trial of reminder/recall. RESULTS: UTD rates for 7-11 month olds increased from 21% before the QI project to 52% after (P <.0001); rates for 12-18 month olds increased from 16% before QI to 44% after (P <.0001); 19-25 month olds 18% before to 33% after (P <.001). After QI, an average of 61 records per month were updated with IZs received elsewhere. However, the accuracy of parental contact information worsened (29% unreachable before QI vs 44% after, P <.001) and missed opportunities did not improve (8% before vs 6% after, P = not significant [NS]). A subsequent trial of reminder/recall did not increase UTD rates, with 17% of recalled children brought UTD vs 16% of controls (P = NS). CONCLUSIONS: Clinic-based QI increased documented UTD rates in a disadvantaged patient population. However, IZ reminder/recall did not further increase UTD rates above the rates achieved by the QI process.  相似文献   
994.
Endometrial carcinomas are classified by their morphology into two major subtypes. Endometrioid carcinomas (type I) are generally estrogen dependent, well-differentiated, superficially invasive, and have a good outcome. Serous carcinomas (type II) are hormone independent, frequently deeply invasive and widely metastatic, and have a poor prognosis. Microarray technology and analysis allows us to determine if the global gene expression profiles of these two subtypes correlate with their morphologic phenotype. Fresh tissue from 18 endometrial carcinomas was studied: 7 well-, 2 moderately, and one poorly differentiated endometrioid, 4 serous carcinomas, and 4 high-grade mixed endometrioid-serous carcinomas. Labeled cDNA probes were synthesized (Cy5 for tumor, Cy3 for reference) and applied to microarrays containing 18,098 cDNA clones or ESTs. A pool of equal amounts of total RNA from each tumor served as the reference RNA. By unsupervised cluster analysis, the endometrioid carcinomas clustered together and were separate from the serous carcinomas. The high-grade mixed carcinomas clustered with the serous carcinomas. Using a statistical algorithm based on gene expression pattern and conducting a supervised analysis of the two defined groups, we have identified 315 genes that statistically differentiate type I from type II endometrial carcinomas. In addition to corroborating the predicted overexpression of known markers (e.g., ras and catenin in endometrioid carcinomas), the cDNA microarray technique has revealed novel alterations in gene expression relevant to cell cycle, cell adhesion, signal transduction, apoptosis, and tumor progression not previously implicated in endometrial carcinomas. For serous carcinomas, these include aldolase, desmoplakin, integrin-linked kinase, PKC, and metallopeptidase. In conclusion, the gene expression profiles of type I and type II endometrial carcinomas are different. Refinement of these profiles will permit more accurate diagnostic tumor classification and the development of prognosis assays.  相似文献   
995.
996.
BACKGROUND: The relationship between asthma severity and atopy is complex. Many studies have failed to show significant relationships between clinical severity or lung function and markers of atopic sensitisation. AIM: To determine whether increasing asthma severity is related to atopic sensitisation in a population of children with asthma. METHODS: A total of 400 children (7-18 years) with asthma were recruited as part of a multicentre study of the genetics of asthma. Detailed phenotypic data were collected on all participants. Associations between measures of asthma severity and atopic sensitisation were sought using multilevel models allowing variation at the individual and family level. RESULTS: Children recruited to the study had a range of asthma severities, with just over a third having mild persistent asthma. The logarithm of total serum IgE was associated with increased asthma severity score, decreased FEV1, increased airways obstruction, risk of hospital admission, and inhaled steroid use. Increasing skin prick test reactivity to a panel of seven aeroallergens was associated with increased risk of hospital admission, use of an inhaled steroid, and airways obstruction. The results remained highly significant after corrections for age, gender, and birth order. CONCLUSIONS: In children with asthma, increasing atopy is associated with increasing asthma severity. However, the relationships between asthma severity and skin prick tests, and asthma severity and total serum IgE values, appear subtly different.  相似文献   
997.
Objectives: To explore whether severity and/or consistency of dysphonia are linked to voice‐related quality of life. Design: Cross‐sectional study. Setting: Specialist voice clinics, University Teaching Hospital. Participants: Sixty adult patients attending with a primary complaint of dysphonia. Exclusion criteria were those below 16 years of age, transexual patients and those with a persistent dysphonia of >2 years. Main outcome measures: Voice‐related quality of life as assessed by VoiSS. Explanatory factors: Severity of dysphonia as judged by perceptual ratings of voice (GRBAS); a visual analogue scale to judge best, worst and today's voice. Results: There was a highly significant correlation between perceptual dysphonia severity as assessed by GRBAS and the total, impairment and emotional subsets of the VoiSS questionnaire (r from 0.48 to 0.64). There was a similar and highly significant correlation between best, worst and today's self‐rated voice and the total, impairment and emotional subsets of the VoiSS questionnaire (r from ?0.40 to ?0.60). However, none of the self‐rated parameters was demonstrably better at explaining the effect on quality of life. Conclusions: An increasingly negative effect on quality of life appears to be associated with an increase in the severity of dysphonia. Further research on the role of quality of life measures in the assessment and treatment of dysphonia would be of value.  相似文献   
998.
Objectives: To investigate the acoustic similarity between natural and sedation‐induced snores. Design: Prospective observational study. Setting: University Hospital Aintree, Liverpool, UK. Participants: Twenty‐one patients, who had already had overnight snore recordings, completed a pre‐operative sleep nasendoscopic examination. Endoscopic examination of the upper aero‐digestive tract was performed at sequentially increasing, steady‐state sedation levels, using intravenous propofol administered according to a weight/time‐based algorithm to predict blood and effect site (tissue) concentrations. At each sedation level at which snoring occurred, snoring sound was recorded. From these samples, snore files, comprising the inspiratory sound of each snore were created. Similarly, from natural snores recorded pre‐operatively, snore files, comprising the inspiratory sounds of the first 100 snores with the patient sleeping in a supine position, were also created. Main outcome measures: Snore duration (s), loudness (dBA), periodicity (%) and energy ratios for the frequency sub‐bands 0–200, 0–250 and 0–400 Hz. Results: Snore loudness increased significantly (P < 0.0001), whilst energy ratios for frequency bands 0–200, 0–250 and 0–400 Hz all decreased significantly as sedation level increased (P < 0.001). A significant difference between natural snoring and snoring induced at the lowest sedation level was shown (P < 0.0001). Endoscopic examination was not tolerated at this sedation level. Conclusions: The acoustic characteristics of sedation‐induced and natural snores are sufficiently different to recommend the need for further research to determine whether the technique of sleep nasendoscopy is, in fact, a valid predictor of outcome of snoring surgery.  相似文献   
999.
The intrauterine contraceptive device is used extensively in the female population. Serious complications are rare, but they do occur. We discuss three cases of bowel perforation caused by these devices following their perforation through the uterine wall. It is important that cases of perforation be recognised swiftly and the possibility of involvement of other organs considered.  相似文献   
1000.
Medical intractability is one of the absolute indications for considering temporal lobe epilepsy surgery. This is a relative concept that has to be highly individualized. It is quite easy to determine when a patient's seizures are fully controlled. On the other hand, "continuing seizures are not necessarily a measure of intractability or disability". A positive decision to operate would be based on some of the following factors: assurance of a firm diagnosis, seizures that are frequent and disabling, and seizures occurring in patients who are drug refractory to optimal anti-epileptic medications and dosages.  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