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   1047551篇
  免费   77742篇
  国内免费   2653篇
耳鼻咽喉   13710篇
儿科学   36043篇
妇产科学   29667篇
基础医学   152622篇
口腔科学   29599篇
临床医学   95120篇
内科学   202303篇
皮肤病学   24113篇
神经病学   84327篇
特种医学   40823篇
外国民族医学   305篇
外科学   156329篇
综合类   23905篇
一般理论   412篇
预防医学   81153篇
眼科学   23603篇
药学   75266篇
  3篇
中国医学   2103篇
肿瘤学   56540篇
  2018年   11687篇
  2017年   9210篇
  2016年   10620篇
  2015年   11574篇
  2014年   15559篇
  2013年   24133篇
  2012年   31654篇
  2011年   33866篇
  2010年   20093篇
  2009年   18455篇
  2008年   31868篇
  2007年   33688篇
  2006年   33893篇
  2005年   32516篇
  2004年   31738篇
  2003年   30614篇
  2002年   29557篇
  2001年   48876篇
  2000年   50603篇
  1999年   41588篇
  1998年   11640篇
  1997年   10514篇
  1996年   10468篇
  1995年   10044篇
  1994年   9363篇
  1993年   8748篇
  1992年   32460篇
  1991年   31633篇
  1990年   31181篇
  1989年   30106篇
  1988年   27345篇
  1987年   27501篇
  1986年   25625篇
  1985年   24826篇
  1984年   18665篇
  1983年   15736篇
  1982年   9506篇
  1981年   8571篇
  1979年   17058篇
  1978年   12368篇
  1977年   10486篇
  1976年   9916篇
  1975年   10323篇
  1974年   12439篇
  1973年   11984篇
  1972年   10956篇
  1971年   10179篇
  1970年   9446篇
  1969年   8801篇
  1968年   8193篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
Aim:To investigate the clinical characteristics of patients with Peyronie's disease(PD)and diabetes mellitus(DM).Methods:During an 8-year period,a total of 307 men seen at our outpatient clinic were diagnosed with PD.Clinicalcharacteristics,penile deformities and the erectile status of patients with PD and DM together(n=102)were retro-spectively analyzed and compared to patients with PD alone with no risk factors for systemic vascular diseases(n=97).Results:The prevalence of PD among men with DM and sexual dysfunction was 10.7%.The mean ageof diabetic patients with PD was(55.9±8.9)years;in the no risk factor group it was(48.5±9.0)years(P<0.05).The median duration of DM was 5 years.The majority of diabetic patients with PD(56.0%)presented in the chronicphase(P<0.05),and they were more likely to have a severe penile deformity(>60°)than the no risk factor group(P<0.05).In the diabetic group,the most common presenting symptom was penile curvature(81.4 %),followedby a palpable nodule on the shaft of the penis(22.5%)and penile pain with erection(14.7 %).A total of 19.6 % ofpatients were not aware of their penile deformities in the diabetic group.Erectile function,provided by history and inresponse to intracavernosal injection and a stimulation test,was significantly diminished in patients with PD and DM(P<0.05).Conclusion:DM probably exaggerates the fibrotic process in PD.Diabetic patients with PD have ahigher risk of severe deformity and erectile dysfunction(ED).PD seems to be a silent consequence of DM andshould be actively sought in diabetic men.(Asian J Androl 2006 Jan;8:75-79)  相似文献   
133.
Background: Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.

Methods: In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded.

Results: The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion.  相似文献   

134.
135.
Abstract: Background: Fetal pulse oximetry improves the assessment of fetal well‐being during labor. The objective of this study was to evaluate women's satisfaction with their experience with this additional technology. Methods: We surveyed women participating in the FOREMOST trial, a randomized controlled trial comparing the addition of fetal pulse oximetry (FPO) to conventional cardiotocograph (CTG) monitoring (intervention group), versus CTG‐only (control group), in the presence of nonreassuring fetal status during labor. Our survey evaluated 3 aspects of women's experience: labor, fetal monitoring, and participation in the research. The survey was administered within a few days of giving birth and repeated 3 months later. Results: No differences were found between the intervention and control groups for women's evaluations of their labor, fetal monitoring, research, or overall experiences when surveyed on both occasions. Within each study group, a small but statistically significant decline occurred in women's scores for their experience of labor and overall experience from the initial survey close to the time of giving birth, to 3 months later. The magnitude of differences in responses over time was similar for the both groups. Women were more satisfied after a spontaneous or assisted vaginal birth than after cesarean section. Length of time the research midwife was present had a significant positive effect on women's ratings of their experience several days after giving birth (p = 0.006), but no effect at 3 months. Conclusions: The addition of fetal pulse oximetry for the assessment of fetal well‐being during labor did not affect childbearing women's perceptions of fetal monitoring or their labor. Women evaluated their experience in the research process positively overall. Small changes occurred in women's perception of their satisfaction over time. (BIRTH 33:2 June 2006)  相似文献   
136.
B.  Greg  Brown  John  Growley  宋善俊 《美国医学会杂志》2006,25(2):124-126
过去15年来,有关动脉粥样硬化的流行病学、基础生物学和实验研究均支持下述假设:抗氧化剂可通过抑制动脉壁低密度脂蛋白的氧化而抑制动脉粥样硬化的发生。这种作用机制可抑制胆固醇酯通过巨噬细胞清除受体在动脉斑块内发生病理性沉积。胆固醇酯病理沉积是一种可引起斑块破裂及心血管事件的过程。同样,生物机制亦已确定,癌基因可被抗氧化剂阻断。  相似文献   
137.
138.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  相似文献   
139.
OBJECTIVE: To explore the impact of timing and type of ultrasound, particularly three-dimensional (3D), exposure on maternal-fetal attachment and maternal health behavior during pregnancy. METHODS: Subjects were 68 women aged 18 years or older expecting their first child who presented for a routine ultrasound scan at around either 12 or 18 weeks' gestation in Nepean Hospital, Western Sydney. Women completed questionnaires assessing maternal-fetal attachment and health behavior, and were then allocated arbitrarily to either two-dimensional (2D) or 3D ultrasound examination. Repeat questionnaires were completed 1 week later. RESULTS: Maternal-fetal attachment increased after both 2D and 3D ultrasound exposure, and the effect was moderated by the timing of exposure, with women receiving their first ultrasound examination at around 12 weeks showing the greatest change. Alcohol consumption was the only behavior to show significant change following ultrasound exposure, with a reduction in the reported average number of drinks per week. There was no significant difference in the pattern of change for 2D compared with 3D ultrasound exposure, and no effect of ultrasound exposure on maternal perception of the fetus. CONCLUSIONS: Ultrasound has a positive impact on maternal-fetal attachment, particularly in the first trimester. 3D ultrasound did not offer enhanced benefits. Associations between ultrasound exposure and alcohol consumption warrant further investigation. Larger samples are needed to clarify the moderating effects of gestational age and type of ultrasound exposure.  相似文献   
140.
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