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   7862篇
  免费   516篇
  国内免费   38篇
耳鼻咽喉   145篇
儿科学   351篇
妇产科学   485篇
基础医学   920篇
口腔科学   182篇
临床医学   676篇
内科学   1902篇
皮肤病学   244篇
神经病学   541篇
特种医学   482篇
外科学   976篇
综合类   46篇
一般理论   1篇
预防医学   530篇
眼科学   110篇
药学   438篇
  1篇
中国医学   23篇
肿瘤学   363篇
  2023年   30篇
  2022年   70篇
  2021年   188篇
  2020年   90篇
  2019年   209篇
  2018年   284篇
  2017年   152篇
  2016年   153篇
  2015年   175篇
  2014年   248篇
  2013年   311篇
  2012年   327篇
  2011年   403篇
  2010年   291篇
  2009年   318篇
  2008年   363篇
  2007年   444篇
  2006年   379篇
  2005年   365篇
  2004年   318篇
  2003年   277篇
  2002年   285篇
  2001年   231篇
  2000年   281篇
  1999年   216篇
  1998年   161篇
  1997年   149篇
  1996年   145篇
  1995年   104篇
  1994年   116篇
  1993年   125篇
  1992年   119篇
  1991年   99篇
  1990年   112篇
  1989年   115篇
  1988年   125篇
  1987年   82篇
  1986年   88篇
  1985年   62篇
  1984年   50篇
  1983年   32篇
  1982年   31篇
  1981年   40篇
  1980年   27篇
  1979年   22篇
  1977年   35篇
  1976年   29篇
  1975年   20篇
  1974年   22篇
  1973年   21篇
排序方式: 共有8416条查询结果,搜索用时 15 毫秒
1.

Background

Obesity is a risk factor for acetabular component malposition when total hip arthroplasty is performed with manual techniques. The utility of imageless navigation in obese patients remains unknown. This study compared the accuracy and precision of imageless navigation for component orientation between obese and nonobese patients.

Methods

A total of 459 total hip arthroplasties performed for osteoarthritis using imageless navigation were reviewed from a single surgeon’s institutional review board–approved database. Einzel-Bild-Roentgen Analyse determined component orientation on 6-week postoperative anteroposterior radiographs. Mean orientation error (accuracy) and precision were compared between obese (body mass index ≥ 30 kg/m2) and nonobese patients. Regression analysis evaluated the influence of obesity on component position.

Results

The difference in mean inclination and anteversion between obese and nonobese groups was 1.1° (43.0° ± 3.5°; range, 35.8°-57.8° vs 41.9° ± 4.4°; range, 33.0°-57.1° and 24.9° ± 6.3°; range, 14.2°-44.3° vs 23.8° ± 6.6°; range, 7.0°-38.6°, respectively). Inclination precision was better for nonobese patients. No difference in inclination accuracy or anteversion accuracy or precision was detected between groups. And 83% of components were placed within the target range. There was no relationship between obesity (dichotomized) and component placement outside the target ranges for inclination, anteversion, or both. As a continuous variable, increased body mass index correlated with higher odds of inclination outside the target zone (odds ratio, 1.06; P = .001).

Conclusion

Using imageless navigation, inclination orientation was less precise for obese patients, but the observed difference is likely not clinically relevant. Accurate superficial registration of landmarks in obese patients is achievable, and the use of imageless navigation similarly improves acetabular component positioning in obese and nonobese patients.

Level of Evidence

Therapeutic Level IV.  相似文献   
2.
3.
4.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.  相似文献   
5.
6.
We have identified the A3243G heteroplasmic point mutation in mitochondrial DNA from a female patient with headache as the main clinical feature. The mitochondrial origin of her disease was only suspected because of her brother with MELAS syndrome. Morphological and biochemical studies failed to reveal mitochondrial respiratory chain dysfunction in her muscle which contained 65% of mutated mitochondrial DNA molecules. Molecular studies performed among four generations (in the blood of seven subjects) showed the variable transmission of mutated molecules and pointed out the difficulty in giving genetic counsel.  相似文献   
7.
1. The present study aimed to determine the feasibility of conducting a 5 year cardiovascular outcome trial of the treatment of 6000 elderly hypertensive patients in Australian general practices. 2. General practitioners (GPs) were invited to participate by mail and personal follow-up. Patient records were reviewed to identify subjects for a blood pressure (BP) screening programme. Blood pressure was measured on three occasions and eligible subjects were included if the average BP was 160 mmHg systolic or 90 mmHg diastolic if systolic BP was 140 mmHg. 3. Seven hundred and forty-one GPs were approached and 89 were enrolled in the study (12% of mail invites and 75% of those receiving a personal contact). In 16 practices where screening was completed, 82 000 records were reviewed to identify 4% patients eligible for screening. Twenty-two per cent of eligible subjects attended screening. Of 1938 subjects screened, 180 (9%) had BP 5=160/90 mmHg. Forty-seven percent of subjects (n = 916) were receiving antihypertensive therapy and 184 (20%) were withdrawn from therapy. One hundred and sixteen (63%) of these subjects had BP return to study entry levels within 6 weeks. Fifty-seven newly diagnosed and 81 previously treated subjects were randomized (7% of the screened population). 4. Based on the high participation rate of GPs, the response rate of patients to attend a BP screening programme and the 7% randomization to screening ratio for entry into the study, the ANBP2 pilot study has demonstrated that it is feasible to recruit subjects from Australian general practices to a cardiovascular outcome trial.  相似文献   
8.
Computed tomography angiogram of the head and neck has lately become a pivotal imaging modality in the patient with acute stroke symptoms due to its high resolution, accuracy, speed, and sensitivity in the assessment of brain parenchyma and vascular patency.  相似文献   
9.
10.
AIMS: To show that a thrice daily meal-time biphasic insulin aspart (BIAsp) treatment regimen is as efficacious as a 4 times daily basal-bolus regimen with human isophane insulin (NPH) and insulin aspart (IAsp). METHODS: A multinational, randomised, open-label parallel-group trial in 394 patients with type 2 diabetes on a once or twice daily insulin regimen. Patients were randomised 1:1 to BIAsp or IAsp+NPH for 16 weeks. The BIAsp group was treated according to individual needs using BMI as a surrogate index of insulin resistance. Subjects administered BIAsp 70 (BMI< or =30 kg/m (2)) or BIAsp 50 (BMI>30 kg/m (2)) with breakfast and lunch and BIAsp 30 with dinner. The IAsp+NPH group injected IAsp at meals and NPH at bedtime as basal insulin. HbAlc levels after 16 weeks were compared between treatments using a predefined non-inferiority criterion of 0.4%. The incidence of hypoglycaemic episodes and adverse events was evaluated. RESULTS: Mean HbAlc (+/-SD) decreased from 9.1+/-0.7% to 7.8+/-1.0% with both treatments. Glycaemic control provided by BIAsp was non-inferior to that obtained by the IAsp+NPH (intention to treat ITT) population: diff, HbAlc -0.05%; 95% CI (-0.24; 0.14); per protocol (PP) population: diff, HbAlc -0.03%; 95% CI (-0.23; 0.16). Similar improvements in glycaemic control in both groups were confirmed by self-measured 8-point plasma glucose (PG) profiles, average and fasting PG concentrations, and average prandial PG increments. The incidence of adverse events and hypoglycaemic episodes was similar in the two treatment groups. CONCLUSIONS: A thrice daily meal-time BIAsp regimen is a suitable alternative to an intensified insulin regimen in people with inadequately controlled type 2 diabetes mellitus, and requires fewer daily injections than a basal-bolus therapy without compromising efficacy and safety.  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