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   16540篇
  免费   1511篇
  国内免费   236篇
耳鼻咽喉   77篇
儿科学   665篇
妇产科学   233篇
基础医学   860篇
口腔科学   519篇
临床医学   1960篇
内科学   2020篇
皮肤病学   89篇
神经病学   1518篇
特种医学   192篇
外科学   1025篇
综合类   1725篇
现状与发展   1篇
预防医学   5013篇
眼科学   98篇
药学   792篇
  32篇
中国医学   375篇
肿瘤学   1093篇
  2024年   63篇
  2023年   364篇
  2022年   643篇
  2021年   891篇
  2020年   802篇
  2019年   739篇
  2018年   685篇
  2017年   690篇
  2016年   640篇
  2015年   607篇
  2014年   1109篇
  2013年   1301篇
  2012年   987篇
  2011年   1068篇
  2010年   806篇
  2009年   890篇
  2008年   902篇
  2007年   831篇
  2006年   617篇
  2005年   500篇
  2004年   428篇
  2003年   373篇
  2002年   308篇
  2001年   251篇
  2000年   234篇
  1999年   181篇
  1998年   172篇
  1997年   137篇
  1996年   117篇
  1995年   130篇
  1994年   92篇
  1993年   92篇
  1992年   83篇
  1991年   70篇
  1990年   57篇
  1989年   63篇
  1988年   56篇
  1987年   35篇
  1986年   30篇
  1985年   58篇
  1984年   37篇
  1983年   25篇
  1982年   24篇
  1981年   22篇
  1980年   16篇
  1979年   16篇
  1978年   12篇
  1977年   7篇
  1976年   7篇
  1972年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
An investigation was undertaken to determine the factors influencing performance of medical students at the Faculty of Medicine, University of Kuwait. Data were collected for the first batch of 42 candidates who successfully passed the 7-year medical programme. Results showed high correlations between high-school admission grades and subsequent performance during the medical programme. Similar results were also obtained with English proficiency. A partial correlation controlling for English proficiency, however, showed a systematic decline in the magnitude of the correlations between high-school grades and performance during the medical programme. In fact the relationship between high-school GPA and clinical GPA was non-significant. A prominent influence of English proficiency on performance is indicated.  相似文献   
62.
BACKGROUND: Assessment of nutritional status in children with cystic fibrosis (CF) is clinically relevant. Methods to measure nutritional status should be reliable and non-invasive, and reference values should be available. AIM: To compare weight and height measurements and measurements of specific body compartments in children with CF. METHODS: In a cross-sectional survey of 58 children with CF (28 females), we compared height and weight (expressed as: weight-for-height, body mass index (BMI), height-for-age and weight-for-age) with fat mass (skinfold sum (SFS)), muscle mass (upper arm circumference (UAC)) and bioelectrical impedance analysis (BIA). Results were expressed as Z-scores, using Dutch reference values. RESULTS: BMI and weight-for-height were within the normal range (mean Z-score (range): -0.13 (-1.5, 2.7) and -0.02 (-1.7, 2.8)). Weight and height corrected for age were below normal (mean Z-score (range): -0.79 (-2.4, -0.05) and -1.2 (-2.8, 1.4) (P<0.01)). Lean body mass by skinfold sum (LBM(sfs)), UAC and BIA were also significantly below reference values (mean Z-score (range): -0.9 (-2.2, 1.8), -0.95 (-2.4, 1.8) and -1.1 (-3.6, 1.0) (P<0.01)). Lean body mass (LBM) by BIA correlated with LBM(sfs). BIA systematically underestimated LBM in both CF patients and in control subjects. CONCLUSION: Nutritional status of children with CF must be evaluated, using age-corrected weight and height expressed in Z-score. LBM estimated by SFS, UAC and by BIA appear to be useful, although longitudinal studies in CF children should be performed to evaluate their clinical significance in detecting changes in nutritional status.  相似文献   
63.
The aim of the study was to investigate if the stretch reflex of the soleus muscle was useful in quantifying upper motor neuron lesions. The soleus stretch reflex was recorded in 10 healthy subjects and 20 patients with active relapsing-remitting multiple sclerosis and correlated to the number of MRI lesions in cerebrum and clinical scores (expanded disability status scale and regional functional scoring system). The short latency stretch reflex was elicited by rotating the left ankle joint 4 degrees with a rise time in the interval of 40-640 ms. The amplitude of the stretch was larger in multiple sclerosis patients being 88.5 microV in patients and 12.8 microV in controls, P = 0.007. The sensitivity of the stretch reflex expressed as the slope of the best linear fit was increased in MS patients to 2.6 microVs/degree compared with 0.6 microVs/degree (0.1-2.2) in controls, P = 0.009. There was no correlation between amplitude of the stretch reflex and number of MRI lesions (r = -0.03). In conclusion, the soleus stretch reflex might be useful to quantify spasticity but is not useful in detecting dysfunction of upper motor neurons in MS.  相似文献   
64.
Based on experimental data from animal studies different theories regarding the size of an epileptic focus have been postulated which range from single pacemaker cells to extended neuronal networks. We report a case which gives further information about the size of a human epileptic focus which can trigger manifest epileptic seizures. We report a 22-year-old man with medically refractory temporal lobe epilepsy. This patient suffered from brief complex partial seizures and frequent epigastric auras. To differentiate a mesiotemporal from a temporolateral seizure origin the patient was implanted with a 10 contact depth electrode from a posterior approach into the right hippocampus, and additional temporobasal/temporolateral subdural strip electrodes. Depth recordings revealed an electrographic status with continuous rhythmic sharp wave activity (1 Hz), the field of which was confined to a diameter of less than 1 cm in the anterior hippocampus, whereas temporobasal subdural strip electrodes did not display this activity. Periodically, spread of this activity occurred to the amygdala, to the posterior part of the hippocampus, and less often to the temporobasal cortex. Most seizure patterns remained subclinical, few of them became symptomatic as partial seizures. This case demonstrates that a hippocampal epileptic focus causing electrographic focal status epilepticus may be limited to a volume of less than 1 cm in diameter. This observation is discussed with regard to implantation strategies and to possible superselective resective or modulatory approaches in the treatment of such limited epileptogenic areas.  相似文献   
65.
目的探讨血清B细胞淋巴瘤相关蛋白-2(Bcl-2)和半胱氨酸天冬氨酸蛋白酶-9(Caspase-9)对儿童癫痫持续状态(SE)近期预后的预测价值。 方法选择SE患儿62例为SE组,选择同期体检健康儿童62例为对照组;按照预后将SE患儿分为预后不良组和预后良好组。癫痫持续状态严重程度量表(STESS)评估SE患儿SE严重程度。ELISA检测各组血清Bcl-2和Caspase-9水平。结果SE组Bcl-2和Caspase-9水平高于对照组(P<0.05)。预后不良组和预后良好组STESS评分、Bcl-2和Caspase-9水平比较,差异有显著性(P<0.05)。STESS评分、Bcl-2和Caspase-9是影响SE患儿近期预后的独立影响因素(P<0.05);入院血清Bcl-2和Caspase-9联合检测对SE患者近期预后具有较好的预测效能(P<0.05)。 结论血清Bcl-2和Caspase-9是SE患儿近期预后的有效预测指标。  相似文献   
66.
Immunologic changes have been reported in the dementing illnesses of mid and late life. The results of two studies of drug-free males meeting research diagnostic criteria for primary neuronal degeneration of the Alzheimer's type suggest that serum IgG levels decrease with the progression of dementia. Serum IgG levels were inversely correlated with duration of illness and the levels of psychiatric symptomatology. Performance on the mini-mental status examination was positively associated with serum IgG concentrations.  相似文献   
67.
Chronic arthritis may have great impact on the patient but also on his or her family, relatives and friends. The assessment of the consequences of chronic arthritis and the effect of therapy not only in terms of physical, but also psychological and social dimensions deserves more attention. Functional ability and health status can be measured using a questionnaire or ‘instrument’, high-lighting important aspects not quantified with more traditional measurements. In this paper, arguments to apply such instruments more frequently are given. Health status instruments can be used not only to assess beneficial but also deleterious (side-)effects of therapeutic interventions. The properties are summarized of the most frequently used instruments assessing functional ability and health status. Many of these instruments have been evaluated sufficiently for validity and reliability; their sensitivity to detect change seems to be satisfactory. Therefore it is advisable to choose an internationally accepted, frequently used instrument, reflecting the area of interest.  相似文献   
68.
We report here a case of primary osteoclastoma that despite possessing HLA-DR-positive status and ‘functional’ calcitonin receptors, exhibited aggressive in vitro and in vivo bone resorptive activity. In the osteoclast bone slice assay employing scanning electron microscopy, the giant cell-mediated bone resorption was uninhibited by salmon calcitonin (10 nM) and significantly inhibited by raised extracellular calcium (20 mM). In Fura-2AM based microspectrofluorimetric assays, the presence of the ‘functional’ calcitonin receptors was ascertained by a rise in intracellular calcium induced by calcitonin and high extracellular calcium. These findings provide evidence for a hitherto unrecognized subtype of giant cells that have HLA-DR-positive status, exhibit avid bone resorptive activity, but remain insensitive to calcitonin despite possessing calcitonin receptors.  相似文献   
69.
The ageing process is accompanied by the disregulation of interleukin 2 (IL2) and interleukin 6 (IL6) production. In our paper, we asked whether the age between 60 and 70 years is a turning point for the disregulation of both IL2 and IL6 production. Fifty volunteers 60–70 years old, 25 aged 36–59, and 50 of 20–35 years old were enrolled into the study. Their health status was graded according to the criteria of the Senieur Protocol (SP) as ‘healthy' and ‘almost-healthy'. The cytokines level was determined in the sera of the volunteers. Moreover, the spontaneous release of IL6 by peripheral blood mononuclear cells (PBMC) and the activity of the IL6 gene in non-stimulated PBMC were also analysed. Cytokine levels were measured by biological assays, mRNA for IL6 was detected by RT-PCR method. The results showed that the production of IL2 is not disregulated in the ‘healthy' people until the age of 60–70. People not fulfilling all SP criteria are characterised by a lower level of IL2 in the sera. The overproduction of IL6 into the sera and supernatants from non-stimulated PBMC and PBL as well as the activation of IL6 gene start between the ages 36 and 59 and is more pronounced in the ‘almost-healthy'.  相似文献   
70.
A procedure is described for standardising the determination of adenosine 5-triphosphate and phosphocreatine concentration ([ATP] and [PC], respectively, in absolute arbitrary units) in human muscle by nuclear magnetic resonance (NMR) spectroscopy. The individual 31phosphorus (21P)-NMR spectra obtained on equal hemispherical tissue volumes (muscle plus skin and fat) were corrected for the thickness of the skin and of the subcutaneous fat. The volumes investigated were standardised using an external reference. The procedure described made possible the comparison of high energy phosphate concentrations among different subjects. It was applied to the assessment of [ATP] and [PC] in four groups of sedentary subjects (children, and adults aged 20–35, 35–50 and over 50 years), and in a group of athletes (volleyball players). The [ATP] and [PC] were not statistically different in the groups investigated.  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