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   27924篇
  免费   1448篇
  国内免费   115篇
耳鼻咽喉   349篇
儿科学   668篇
妇产科学   480篇
基础医学   3625篇
口腔科学   1878篇
临床医学   1972篇
内科学   6855篇
皮肤病学   482篇
神经病学   2303篇
特种医学   540篇
外国民族医学   2篇
外科学   3891篇
综合类   243篇
一般理论   10篇
预防医学   2414篇
眼科学   558篇
药学   1726篇
中国医学   130篇
肿瘤学   1361篇
  2023年   209篇
  2022年   506篇
  2021年   943篇
  2020年   527篇
  2019年   779篇
  2018年   962篇
  2017年   623篇
  2016年   673篇
  2015年   834篇
  2014年   1170篇
  2013年   1407篇
  2012年   2322篇
  2011年   2331篇
  2010年   1293篇
  2009年   1133篇
  2008年   1884篇
  2007年   1941篇
  2006年   1713篇
  2005年   1595篇
  2004年   1370篇
  2003年   1147篇
  2002年   1117篇
  2001年   276篇
  2000年   248篇
  1999年   264篇
  1998年   233篇
  1997年   175篇
  1996年   118篇
  1995年   99篇
  1994年   108篇
  1993年   79篇
  1992年   139篇
  1991年   108篇
  1990年   98篇
  1989年   97篇
  1988年   88篇
  1987年   68篇
  1986年   73篇
  1985年   77篇
  1984年   73篇
  1983年   58篇
  1982年   54篇
  1981年   51篇
  1980年   37篇
  1979年   28篇
  1978年   40篇
  1977年   37篇
  1976年   29篇
  1975年   22篇
  1973年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We performed proton magnetic resonance spectroscopic imaging of the temporal lobes between, during, and soon after nonconvulsive seizures in 20 patients with documented temporal lobe epilepsy, 5 patients with primary generalized epilepsy, and 2 patients with secondary generalized epilepsy. Our objective was to determine whether there were metabolic changes observable by magnetic resonance spectroscopic imaging during seizures and whether these changes were specific for focal or generalized nonconvulsive seizures. We found a significant increase in lactate to creatine plus phosphocreatine (lactate/creatine) values, reflecting an imbalance in energy supply and demand or an adaptation in response to ictal neuronal discharges, during and soon after complex partial seizures, but not during or soon after absence seizures associated with generalized epilepsy. In patients with temporal lobe epilepsy, the N-acetylaspartate resonance relative to creatine plus phosphocreatine was low in one or both temporal lobes, indicating neuronal loss or damage. This was not observed in patients with primary generalized epilepsy. The regions with abnormal lactate/creatine and N-acetylaspartate/creatine values corresponded to the epileptogenic focus as defined by clinical-electroencephalographic investigation. There was no change in the N-acetylaspartate/creatine values in the temporal lobes between the interictal, ictal, or postictal states. We conclude that (1) partial seizures are associated with abnormally high lactate levels, but absence seizures are not, and (2) no short-term changes of N-acetylaspartate occur during or soon after complex partial seizures or absence seizures. These findings may be related to the lack of postictal confusion in patients with absence seizures, as well as with the more benign course of primary generalized epilepsy with nonconvulsive attacks.  相似文献   
22.
ABSTRACT: A case study of the creation and implementation of a four-tier, integrated system of health care services in a sparsely populated, rural province in Argentina is described and discussed. Begun in 1970 in a diverse geographical area with a tradition of poor health status and inadequate health care resources, the provincial government set out to develop the human, physical and technological resources needed to provide a system of preventive and curative services appropriate to the health care needs of its residents. Innovative programs included training in management techniques, and epidemiological perspective of high risk, an emphasis on personnel development through a rural general medicine residency and an expanded nursing program as well as programs to attack infectious diseases, poor sanitation and dental problems were all developed in response to the distinctive features of the physical and social environment of the province. Improvements in traditional health indicators are reviewed and attributed to the program and administrative structures that were developed.  相似文献   
23.
From the data submitted to the Pan American Health Organization (PAHO) by nationwide programs against sexually transmitted diseases (STD), HIV infection, and AIDS (2002), one can estimate the overall prevalence of syphilis among pregnant women to be 3.1% and to range from 1.00% in Peru to 6.21% in Paraguay. According to these data, the incidence of congenital syphilis ranges from 1.4 per 1000 live births in El Salvador to 12.0 per 1000 live births in Honduras. Among men who engage in sex with other men, who often classify themselves as heterosexual, as well as in female sex workers, the prevalence of syphilis ranged from 5% to 15%. Factors that determine the persistence of congenital syphilis as public health problem include a lack of awareness of the seriousness of the problem among politicians, health officials, and health care providers, difficult access to prenatal care, and screening services, a low demand for the test among users, and the stigma and discrimination that surround sexually transmitted diseases (STD). This paper seeks to focus the attention of health professionals on maternal and congenital syphilis so they will undertake actions, using an interprogrammatic approach, to eliminate congenital syphilis from Latin America and the Caribbean. Eliminating congenital syphilis will only become possible if interventions targeting vulnerable groups are also implemented. PAHO's role in eliminating congenital syphilis includes determining the baseline situation in the Region as a whole and in each country, developing communication and procurement strategies, supporting nationwide programs, promoting operational research, and facilitating interprogrammatic coordination.  相似文献   
24.
The aim of this study was to determine the relationship between serum magnesium and TNF-alpha levels in obese subjects. A cross-sectional population based study that included 192 non-diabetic, non-hypertensive subjects allocated in three categories of body mass index (BMI) <25; > or =25 to <30 kg/m2; and > or =30 kg/m2. Elevation of TNF-alpha levels was defined by serum levels > or =3.5 pg/mL, and low serum magnesium by levels < or = 0.74 mmol/L. Multivariate odds ratios (OR) adjusted by age, HOMA-IR index, and glucose tolerance status are presented. Obese subjects exhibited higher serum concentration of TNF-alpha (p = 0.002) and lower serum magnesium levels (p < 0.0001) than lean and overweight subjects. Ninety-one (47.4%) subjects showed elevated levels of TNF-alpha, of them 7 (10.9%), 31 (48.4%), and 43 (67.2%) in the groups with BMI <25, > or = 25 to < 0, and > or =0 kg/m2, respectively. Multivariate OR between low serum magnesium and TNF-alpha levels in obese subjects was of 1.8, Cl95% 1.2-9.1, P = 0.001, whereas in the lean and overweight individuals of 1.1, Cl95% 0.7-8.7, P = 0.12, and 1.3, Cl95% 0.9-10.8, P = 0.09, respectively. These data shows that low serum magnesium levels and elevated TNF-alpha are related in the obese subjects. It will be necessary to conduct more studies in order to add new data on this issue.  相似文献   
25.
The aim of this research was to quantify sleep problems in patients suffering from Parkinson's disease by means of the new Parkinson's Disease Sleep Scale (PDSS) and to correlate such problems with the possible influence of current drug treatment. A total of 70 patients (36 men and 34 women) with a diagnosis of Parkinson's disease were enrolled. Their mean age was 69.7 +/- 8.2 years, and duration of disease was 7.4 +/- 4.8 years. All patients completed the PDSS and the Unified Parkinson's Disease Rating Scale (UPDRS Parts I-IV). Drug consumption and doses were registered. The mean score on the PDSS scale was 109.23 +/- 19.75 and on the UPDRS III scale was 25.24 +/- 11.35. The lowest scores were obtained in Item 3 (sleep fragmentation): 5.53 (2.46); and in Item 8 (nocturia): 5.75 (2.91). There was a weak correlation between the PDSS and UPDRS III (cc = -0.355, P = 0.003), PDSS and UPDRS I (cc = -0.272, P = 0.02), and PDSS and UPDRS IV (cc = -0.416, P < 0.001). Motor conditions, mental state, and drug complications influence sleep quality. Although this effect was significant, it was not of a great magnitude. Dopaminergic drugs did not increase daytime sleepiness. As a whole, sleep quality in patients who took dopaminergic agonists did not differ from that of patients who took levodopa in monotherapy.  相似文献   
26.
An important aspect of preventive medicine is to identify subjects at risk as soon as possible, so preventive strategies can be introduced at early ages. The justification for this strategy is twofold: firstly, the assumption that children maintain a particular high value of a risk factor for disease throughout life; and secondly, the assumption that lowering the level of the risk factor in early life will have a greater impact on the disease than will risk factor changes in later life. In epidemiology the analysis of such factors over time is referred to as tracking. Tracking analysis has been applied to risk factors for cardiovascular diseases (CVD) in pediatric years. The aims of this study were: I) to analyze the stability of biological risk factors [high blood pressure (BP), high percentage of fat mass (%FM) and high total cholesterol (TC)] and lifestyle risk factors [low physical activity index (PAI)] in isolation; and II) to analyze the stability of zero, one, two or three biological risk factors. There were two evaluations in 692 children and adolescents (325 boys and 367 girls), aged between 8 and 15 years. The quartiles, adjusted for age and gender, were the criterion used to identify subjects with biological risk factors (fourth quartile) and with lifestyle risk factors (first quartile) for CVD. The stability was calculated through the relative frequency of subjects who maintained or changed quartile between the two evaluations. There is stability for biological risk factors as well as for behavioral and/or lifestyle risk factors. However, the highest stability is seen in biological risk factors.  相似文献   
27.
28.
29.
30.
Summary An incident is reported in which 2 intravenous drug abusers died as the result of uncontrolled experimentation with intravenous injection of the common anti-hypertensive and anti-anginal drug Nifedipine (Adalatt.m. Bayer), probably in mistake for the commonly abused short-acting benzodiazepine drug Temazepam. Large quantities of Nifedipine were identified in the blood of both deceased men by gas chromatography. Apart from intense gastric mucosal congestion, pulmonary oedema and general visceral congestion, the autopsy findings were entirely nonspecific. The similarity in colour, shape and texture between capsules of Nifedipine and those of Temazepam is likely to have prompted the mistake.  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