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   7989篇
  免费   574篇
  国内免费   22篇
耳鼻咽喉   63篇
儿科学   309篇
妇产科学   214篇
基础医学   1303篇
口腔科学   117篇
临床医学   940篇
内科学   1590篇
皮肤病学   142篇
神经病学   1080篇
特种医学   91篇
外科学   616篇
综合类   62篇
一般理论   14篇
预防医学   1030篇
眼科学   56篇
药学   432篇
中国医学   15篇
肿瘤学   511篇
  2023年   49篇
  2022年   89篇
  2021年   227篇
  2020年   129篇
  2019年   228篇
  2018年   221篇
  2017年   158篇
  2016年   190篇
  2015年   204篇
  2014年   276篇
  2013年   427篇
  2012年   624篇
  2011年   608篇
  2010年   325篇
  2009年   270篇
  2008年   465篇
  2007年   557篇
  2006年   507篇
  2005年   494篇
  2004年   459篇
  2003年   442篇
  2002年   390篇
  2001年   78篇
  2000年   36篇
  1999年   50篇
  1998年   101篇
  1997年   81篇
  1996年   89篇
  1995年   58篇
  1994年   54篇
  1993年   67篇
  1992年   40篇
  1991年   31篇
  1990年   36篇
  1989年   32篇
  1988年   31篇
  1987年   27篇
  1986年   22篇
  1985年   23篇
  1984年   36篇
  1983年   20篇
  1982年   43篇
  1981年   47篇
  1980年   24篇
  1979年   16篇
  1978年   23篇
  1977年   18篇
  1976年   16篇
  1971年   12篇
  1970年   11篇
排序方式: 共有8585条查询结果,搜索用时 15 毫秒
31.
In fetal testes of non-inbred guinea pigs, virus-like particles were seen in the primordial germ cells, but not in the somatic cells. Using the particles as a marker for the gonocytes it was possible to trace the phagocytosis of degenerating gonocytes by the Sertoli cells in the fetal testis.  相似文献   
32.
33.
Scleroderma renal crisis (SRC) is a rare but life-threatening complication of systemic sclerosis (SSc) characterized by malignant hypertension and acute kidney injury. Historically, SRC was the leading cause of death in SSc. However, with the advent of angiotensin converting enzyme (ACE) inhibitors, mortality rates have decreased significantly. Nevertheless, one-year outcomes remain poor, with over 30% mortality and 25% of patients remaining dialysis-dependent. There is an urgent need to improve early recognition and treatment, and to identify novel treatments to improve outcomes of SRC. In this chapter, the clinical features, classification, pathophysiology, differential diagnosis, management and outcomes of SRC are presented. Specific issues relating to pregnancy, prophylactic ACE inhibition and management of essential hypertension are also discussed.  相似文献   
34.
35.
BackgroudCurrent evidence supports the use of cemented hemiarthroplasty for treatment of intracapsular femoral neck fractures since it is associated with a lower risk of implant-related complications. However, many medical centers employ the cementless technique for the frail elderly population because it is faster and has lower cardiovascular risks and perioperative mortality. This observational study reports the outcomes of cementless bipolar hemiarthroplasty for intracapsular femoral neck fractures in patients aged 80 years and older.MethodsA total of 424 patients (female, 77.1%) with a mean age of 86.9 years were operated for intracapsular femoral neck fractures between January 2009 and December 2017. Of those, 66.7% had an American Society of Anaesthesiologists (ASA) score of 3 or more. All operations were performed with the posterolateral surgical approach and all patients received a cementless stem. Intraoperative and perioperative values and in-hospital outcomes were evaluated, and clinical and radiographical follow-up was done at 40 days, 90 days, and when possible between 5 months and 12 months postoperatively. Multivariate analysis was performed to evaluate if there were factors affecting mortality.ResultsThe mean operative time was 50 minutes. There were no deaths intraoperatively. Intraoperative periprosthetic fractures occurred in 2.1% of the cases with 66.7% of them fixed through cerclage wires intraoperatively. The median length of hospitalization was 11 days (interquartile range, 8.75–15) and 2.4% of patients died while in hospital after surgery. Approximately 91.5% of patients presented with perioperative anemia. Only 1.9% of the complications were related to the implant, 62.5% of which were dislocations. More than 90% of patients were ambulatory either autonomously or with support at each follow-up assessment. Age, male sex, and higher ASA score were related to increased mortality.ConclusionsDespite some limitations, this observational study underlines that a cementless femoral stem of modern design can give good clinical outcomes, thus being an appropriate solution especially for the frail elderly.  相似文献   
36.
37.
This study compared parent-reported competencies and behavioral/emotional problems in demographically-matched samples of Greek and American children, ages 6–11. Parents of 356 children of each nationality completed the Child Behavior Checklist (CBCL). Competence scores were higher for American children, except on Academic Competence, where scores were higher for Greek children. Greek scores were significantly higher than American scores on the Withdrawn, Anxious/Depressed, Attention Problems, Delinquent Behavior, Aggressive Behavior, Internalizing, Externalizing, and Total Problem scales. On the Anxious/Depressed syndrome, nationality accounted for 14% of the variance. There were few main effects for sex and age and fewer interactions. The higher problem scores in the Greek sample were partly due to the tendency of Greek parents to use extreme item scores. When items were scored present v. absent, Greek scores were higher only on Withdrawn, Anxious/Depressed, Internalizing, and Total Problems, while American scores were higher on Somatic Complaints and Thought Problems. Nationality differences in rates of referral for mental health services and sample differences in exclusion criteria for prior mental health services may have contributed to differences in problem scores. Results are compared to findings from other cross-cultural studies.
Zusammenfassung Diese Studie vergleicht die Fähigkeiten und Verhaltens- bzw. emotionalen Auffälligkeiten in demographisch parallelisierten Stichproben von griechischen und amerikanischen Kindern im Alter von 6-11 Jahren. Die Eltern von 356 Kindern der beiden Nationalitäten füllten die Child Behavior Checklist (CBCL) aus. Die Kompetenzwerte waren bei den amerikanischen Kindern mit Ausnahme der akademischen Fähigkeiten höher. Die griechischen Werte waren signifikant höher als die amerikanischen im Hinblick auf die Skalen Zurückhaltung, ängstlich/depressiv, Aufmerksamkeitsstörungen, delinquentes Verhalten, aggressives Verhalten, Internalisation, Externalisation und Gesamtauffälligkeiten. Im Hinblick auf das ängstlich/depressive Syndrom war die Nationalität für 14% der Varianz verantwortlich. Nur vereinzelt wurden Haupteffekte im Hinblick auf Geschlecht und Alter und eine geringere Anzahl Interaktionen festgestellt. Die höheren Problemwerte in der griechischen Stichprobe waren teilweise durch die Tendenz der griechischen Eltern bedingt, extreme Werte anzukreuzen. Bei den Items, die als vorhanden bzw. nicht vorhanden gewertet werden mußten, waren die griechischen Werte nur bei den Skalen Zurückhaltung, ängstlich/depressiv, Internalisation und Gesamtprobleme höher, während amerikanische Werte für die Skalen körperliche Beschwerden und Denkstörungen höher lagen. Nationalitätsunterschiede der Zuweisungsraten zu psychosozialen Diensten und Stichprobenunterschieden im Hinblick auf die Ausschlußkriterien für vorangegangene Inanspruchnahme psychosozialer Dienste könnten zu den unterschiedlichen Problemwerten beigetragen haben. Die Ergebnisse werden verglichen mit anderen transkulturellen Studien.

Résumé Cette étude a comparé les compétences et les problèmes de comportement et affectifs rapportés par les parents d'un échantillon d'enfants grecs et américains âgés de 6 à 11 ans appariés démographiquement. Les parents de 356 enfants de chaque nationalité ont rempli la Child Behavior Checklist (CBCL). Les scores de compétence étaient plus élevés pour les enfants américains excepté pour la compétence scolaire pour laquelle les scores étaient plus élevés chez les enfants grecs. Les scores grecs étaient significativement plus hauts que les scores américains quant au retrait, l'anxiété-dépression, les problèmes d'attention, le comportement délinquant, le comportement agressif, les échelles d'internalisation, d'externalisation et de problèmes totaux. Pour le syndrome anxiodépressif, la nationalité intervenait pour une variance de 14%. Il y avait peu d'effets principaux en ce qui concerne le sexe et l'âge. Les scores de problèmes les plus élevés dans les échantillons grecs étaient en partie dûs à la tendance des parents grecs à utiliser des items extrêmes. Quand les items étaient cotés présents versus absents, les scores grecs étaient plus élevés seulement en ce qui concerne le retrait, l'anxiété-dépression, l'internalisation et les problèmes totaux tandis que les scores américains étaient plus hauts en ce qui concerne les plaintes somatiques et les problèmes de pensée. Les différences de nationalité en ce qui concerne les taux de référence à des services de santé mentale et les différences des échantillons dans les critères d'exclusion pour l'utilisation antérieure de services de santé mentale, peuvent avoir contribué aux différences dans les scores de problèmes. Les résultats sont comparés aux autres études transculturelles.
  相似文献   
38.

Background

Previous studies show sex-related differences in left ventricular (LV) response to exercise. It is not clear, however, whether these differences are also seen in younger healthy subjects.

Methods and Results

This study examined the changes in LV performance during dynamic upright exercise in 11 healthy men and 19 healthy young women according to the Bruce protocol and an individualized ramp protocol. There were no significant differences between the two protocols for either men or women in heart rate, blood pressure, LV ejection fraction (EF) (measured by ambulatory nuclear detector), and measured oxygen consumption. The peak oxygen consumption was higher in men than in women (44±13 vs 36±9 ml/kg/min; p<0.05), but the peak heart rate, systolic blood pressure, and EF were similar. The change in EF (from rest to exercise) was 19%±8% in men and 19%±11% in women with the Bruce protocol (difference not significant) and 26%±9% in men and 19%±6% in women with the ramp protocol (difference not significant). At peak exercise, both men and women showed an increase in end-diastolic volume (29%±14% vs 23%±11%; difference not significant) and a decrease in end-systolic volume (41%±15% vs 43%±21%) (difference not significant). The increase in cardiac output during exercise was due to an increase in heart rate and stroke volume in both men and women. At submaximal exercise, however, the decrease in end-systolic volume was less in women than in men (p<0.05).

Conclusions

There are no sex-related differences in compensatory mechanism during dynamic execise in healthy subjects. The changes in contractility and LV volume are not affected by the exercise protocol.  相似文献   
39.
40.
BACKGROUND: Children with neurodevelopmental disorders can have feeding problems. Malnutrition and recurrent aspiration pneumonia can increase the risk of morbidity and mortality. Video-fluoroscopic study of swallowing (VFSS) is essential in understanding the pathological mechanisms involved during swallowing. METHODS: The aim of the present study was to assess the role of VFSS in assessment and management of four children with various neurodevelopmental disorders in a multidisciplinary feeding team. We describe the team approach, with the participation of child neurologist, radiologist with the rehabilitation team including the speech therapist, occupational therapist and dietician, in the assessment and plan of management. RESULTS: Video-fluoroscopic study of swallowing had been useful in assessing the type of swallowing problems with treatment goals targeted to the basic underlying pathophysiological mechanism. CONCLUSION: A child neurologist should be involved in the multidisciplinary oromotor rehabilitation program for neurologically impaired children with feeding problems.  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