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   531篇
  免费   43篇
  国内免费   2篇
儿科学   32篇
妇产科学   68篇
基础医学   62篇
口腔科学   5篇
临床医学   68篇
内科学   73篇
皮肤病学   12篇
神经病学   43篇
特种医学   54篇
外科学   46篇
综合类   5篇
预防医学   61篇
眼科学   2篇
药学   18篇
肿瘤学   27篇
  2023年   1篇
  2022年   8篇
  2021年   10篇
  2020年   9篇
  2019年   9篇
  2018年   11篇
  2017年   6篇
  2016年   8篇
  2015年   15篇
  2014年   13篇
  2013年   24篇
  2012年   15篇
  2011年   16篇
  2010年   14篇
  2009年   20篇
  2008年   20篇
  2007年   29篇
  2006年   30篇
  2005年   16篇
  2004年   20篇
  2003年   19篇
  2002年   15篇
  2001年   14篇
  2000年   14篇
  1999年   14篇
  1998年   18篇
  1997年   11篇
  1996年   14篇
  1995年   19篇
  1994年   12篇
  1993年   7篇
  1992年   12篇
  1991年   7篇
  1990年   13篇
  1989年   4篇
  1988年   8篇
  1987年   11篇
  1986年   11篇
  1985年   15篇
  1984年   14篇
  1983年   5篇
  1982年   6篇
  1981年   3篇
  1980年   3篇
  1978年   3篇
  1977年   2篇
  1976年   6篇
  1975年   1篇
  1962年   1篇
排序方式: 共有576条查询结果,搜索用时 15 毫秒
101.
Trauma affects up to 8% of pregnancies and is the leading cause of death among pregnant women in the United States. A pregnancy test is mandated for all females of childbearing age who are involved in trauma. Orthopaedic trauma in the pregnant patient is managed similarly to that for all trauma patients. Initial resuscitation efforts should focus on the pregnant patient because stable patient vital signs provide the best chance for fetal survival. In the stable patient, fetal assessment and a pelvic examination are mandatory. Radiographs as well as abdominal ultrasound of the patient and fetal ultrasound are useful. No known biologic risks are associated with magnetic resonance imaging, and no specific fetal abnormalities have been linked with standard low-intensity magnetic resonance imaging. Emergency surgery can be safely performed in most pregnant patients. Avoiding patient hypotension and using left lateral decubitus positioning increase the likelihood of success for the patient and fetus. An experienced multidisciplinary team consisting of an obstetrician, perinatologist, orthopaedic surgeon, anesthesiologist, radiologist, and nursing staff will optimize the treatment of both the pregnant patient and her fetus.  相似文献   
102.
The aim of this study was to search for the existence of behavioural states in the human fetus and to describe their developmental course. In a longitudinal study, 14 low-risk fetuses were studied at 2-week intervals from 32 weeks of gestation onward. Fetal body movements as well as fetal eye movements, visualized by means of real-time ultrasonic imaging, and fetal heart rate patterns, recorded by means of a cardiotocograph, were used as state variables.At 38 and 40 weeks, four distinct behavioural states, named states 1F through 4F and corresponding respectively to states 1 through 4 of the neonate, could be identified. That these constellations of parameters represented true behavioural states was demonstrated by the stability of association of parameters for prolonged periods and by the simultaneity of change of parameters at state transitions. There is evidence for episodes of wakefulness in the fetus. Before 36 weeks, cycles were present in each of the state variables, and combinations of parameters typical of particular states were observed. However, the relatively short durations of these combinations and the lack of simultaneity of change in the three state variables support the conclusion that these periods of coincidence occurred by chance and did not represent organized behavioural states.  相似文献   
103.
Crystalline retinopathy   总被引:4,自引:0,他引:4  
A 34-year-old woman had crystalline dystrophy of the retina associated with atrophy of the choriocapillaris and pigment epithelium, and pigment clumping in the fundus periphery. Consanguinity of her parents suggested an autosomal recessive inheritance pattern for this type of crystalline retinal dystrophy. The patient did not have corneal crystals. Her electroretinogram was normal, although her electro-oculogram was abnormal.  相似文献   
104.

Background and purpose:

Lipid rafts and caveolae are membrane microdomains with important roles in cell survival signalling involving the Akt pathway. Cholesterol is important for the structure and function of these microdomains. The ginsenoside Rh2 exhibits anti-tumour activity. Because Rh2 is structurally similar to cholesterol, we investigated the possibility that Rh2 exerted its anti-tumour effect by modulating rafts and caveolae.

Experimental approach:

A431 cells (human epidermoid carcinoma cell line) were treated with Rh2 and the effects on cell apoptosis, raft localization and Akt activation measured. We also examined the effects of over-expression of Akt and active-Akt on Rh2-induced cell death.

Key results:

Rh2 induced apoptosis concentration- and time-dependently. Rh2 reduced the levels of rafts and caveolae in the plasma membrane and increased their internalization. Furthermore, Akt activity was decreased and consequently, Akt-dependent phosphorylation of Bad, a pro-survival protein, was decreased whereas the pro-apoptotic proteins, Bim and Bax, were increased upon Rh2 treatment. Unlike microdomain internalization induce by cholesterol depletion, Rh2-mediated internalization of rafts and caveolae was not reversed by cholesterol addition. Also, cholesterol addition did not restore Akt activation or rescue cells from Rh2-induced cell death. Rh2-induced cell death was attenuated in MDA-MB-231 cells over-expressing either wild-type or dominant-active Akt.

Conclusions and implications:

Rh2 induced internalization of rafts and caveolae, leading to Akt inactivation, and ultimately apoptosis. Because elevated levels of membrane rafts and caveolae, and Akt activation have been correlated with cancer development, internalization of these microdomains by Rh2 could potentially be used as an anti-cancer therapy.  相似文献   
105.
106.
Responsive outcome measures are needed to follow the disease status of Duchenne muscular dystrophy (DMD) patients, as new therapeutic approaches become available for affected boys. Quantitative muscle ultrasound (QMUS) is potentially an attractive follow up tool for DMD because it reflects the severity of the dystrophic process without the need for invasive procedures, by quantifying echo intensity (i.e., mean grey level of muscle images) and muscle thickness. We performed a longitudinal follow-up of lower and upper extremity QMUS in 18 DMD patients and compared this with physical functioning in 11 of these patients. QMUS could be performed in every patient, and no patient was subjected to more than a total of 20min of ultrasound scanning time for this study. As expected we found a significant increase of echo intensity with age, reflecting increasing dystrophic muscle changes. This increase was related to ambulatory status, functional grading, muscle strength and motor ability. Our study establishes QMUS as a practical and child-friendly tool for the longitudinal follow up of DMD patients.  相似文献   
107.
Objectives:Congenital heart defects (CHD) are the most prevalent congenital anomalies. This study aims to examine the association between maternal occupational exposures to organic and mineral dust, solvents, pesticides, and metal dust and fumes and CHD in the offspring, assessing several subgroups of CHD.Methods:For this case–control study, we examined 1174 cases with CHD from EUROCAT Northern Netherlands and 5602 controls without congenital anomalies from the Lifelines cohort study. Information on maternal jobs held early in pregnancy was collected via self-administered questionnaires, and job titles were linked to occupational exposures using a job exposure matrix.Results:An association was found between organic dust exposure and coarctation of aorta [adjusted odds ratio (ORadj) 1.90, 95% confidence interval (CI) 1.01–3.59] and pulmonary (valve) stenosis in combination with ventricular septal defect (ORadj 2.68, 95% CI 1.07–6.73). Mineral dust exposure was associated with increased risk of coarctation of aorta (ORadj 2.94, 95% CI 1.21–7.13) and pulmonary valve stenosis (ORadj 1.99, 95% CI 1.10–3.62). Exposure to metal dust and fumes was infrequent but was associated with CHD in general (ORadj 2.40, 95% CI 1.09–5.30). Exposure to both mineral dust and metal dust and fumes was associated with septal defects (ORadj 3.23, 95% CI 1.14–9.11). Any maternal occupational exposure was associated with a lower risk of aortic stenosis (ORadj 0.32, 95% CI 0.11–0.94).Conclusions:Women should take preventive measures or avoid exposure to mineral and organic dust as well as metal dust and fumes early in pregnancy as this could possibly affect foetal heart development.  相似文献   
108.
Restrictive dermopathy is a rare autosomal recessive lethal skin dysplasia. It has been assumed that the characteristic morphologic abnormalities should allow a reliable prenatal diagnosis on fetal skin biopsies at about 20 weeks pregnancy. We report on a false-negative prenatal diagnosis.  相似文献   
109.
Previous dynamic posturography studies demonstrated clear abnormalities in balance responses in Parkinson's disease (PD) patients compared to controls at the group level, but its clinical value in the diagnostic process and fall risk estimation in individual patients leaves for improvement. Therefore, we investigated whether a new approach, focusing on the balance responses to the very first and fully unpractised trial rather than a pooled mean response to a series of balance perturbations, could further improve the diagnostic utility of dynamic posturography. Following the first trial, subjects were exposed to repeated balance perturbations, which also permitted us to investigate the training responses. Fourteen patients with PD and 18 age-matched controls were enrolled, who received a series of multidirectional postural perturbations, induced by support surface rotations. We measured trunk and upper arm kinematics and electromyographic responses, and evaluated group differences at three levels: the postural response to the very first backward perturbation; pooled first and habituated postural responses; and habituation rates. Analysis of the first trial responses yielded similar results as evaluation of the mean response over trials: forward flexion of the trunk induced by backward perturbations was decreased in patients, accompanied by increased muscle responses present. Moreover, trunk movement and muscle activity were equally present in both groups—suggesting a preserved training response in PD patients. Early masseter activity in both groups might be indicative of a startle-like component to the balance response. In terms of diagnostic utility, focusing on the first trial response or habituation rate is no better than analysis of pooled responses to a series of perturbations. The apparently preserved training response in PD patients suggests that balance reactions in PD can be improved by repeated exposure, and this may have implications for future exercise studies. Early masseter activity warrants further studies to evaluate a potential startle component in the pathophysiology of balance disorders.  相似文献   
110.
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