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   106970篇
  免费   6019篇
  国内免费   648篇
耳鼻咽喉   1041篇
儿科学   3472篇
妇产科学   2449篇
基础医学   15359篇
口腔科学   3921篇
临床医学   9696篇
内科学   24049篇
皮肤病学   2708篇
神经病学   10559篇
特种医学   2509篇
外国民族医学   1篇
外科学   9488篇
综合类   399篇
一般理论   48篇
预防医学   10699篇
眼科学   1716篇
药学   7472篇
中国医学   417篇
肿瘤学   7634篇
  2024年   120篇
  2023年   1027篇
  2022年   2210篇
  2021年   3651篇
  2020年   2292篇
  2019年   3076篇
  2018年   3489篇
  2017年   2663篇
  2016年   3100篇
  2015年   3427篇
  2014年   4503篇
  2013年   5875篇
  2012年   8928篇
  2011年   9297篇
  2010年   5061篇
  2009年   4258篇
  2008年   7382篇
  2007年   7379篇
  2006年   6790篇
  2005年   6333篇
  2004年   5687篇
  2003年   5054篇
  2002年   4547篇
  2001年   543篇
  2000年   387篇
  1999年   586篇
  1998年   787篇
  1997年   642篇
  1996年   545篇
  1995年   449篇
  1994年   427篇
  1993年   349篇
  1992年   285篇
  1991年   188篇
  1990年   191篇
  1989年   177篇
  1988年   170篇
  1987年   141篇
  1986年   156篇
  1985年   109篇
  1984年   132篇
  1983年   128篇
  1982年   155篇
  1981年   115篇
  1980年   123篇
  1979年   71篇
  1978年   76篇
  1977年   70篇
  1976年   58篇
  1974年   54篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Spinocerebellar ataxia (SCA) types 2 and 3 are autosomal-dominant neurodegenerative disorders caused by mutations in two different genes. We identified mutations for SCA2 and SCA3 segregating simultaneously in a single Brazilian family. The index patient had SCA2, whereas her two second-degree cousins had SCA3. Disease was more rapidly progressive in the SCA2 patient, who presented severe brainstem and pancerebellar atrophy, as opposed to the two SCA3 patients, who had only mild cerebellar vermian atrophy. In such situations, molecular confirmation of all patients may avoid misdiagnosis of SCA subtypes and eventual errors in predictive testing of unaffected family members.  相似文献   
12.
13.
BACKGROUND: Oral hairy leukoplakia (OHL) may be an indicator of the progression of Human Immunodeficiency Virus (HIV)-induced immuno-depression, and the evaluation of risk factors leading to OHL is important in the management of these HIV-infected patients. However, there are few studies that analyze risk factors leading to OHL in the Brazilian population. The aim of this case-control study is to present data about prevalence rates and risk factors leading to OHL in a sample of HIV-infected adults in Brazil. METHODS: This case-control study included 111 HIV-infected patients treated at a clinic for sexually transmitted diseases and HIV. In the initial examinations with dentists, variables were collected from all patients. Diagnosis of OHL was performed in accordance with the International Classification System and cytological features. The Fisher and the chi-squared tests were used for statistical analysis. The proportional prevalence and odds ratio were estimated. RESULTS: Outcome presented a positive, statistically significant association among the presence of OHL and viral load of 3000 copies/mul or greater (P = 0.0001; odds ratio (OR) = 5.8), presence of oral candidiasis (P = 0.0000; OR = 11.1), previous use of fluconazole (P = 0.0000; OR = 24.6), and use of systemic acyclovir (P = 0.032; OR = 4.3). Antiretroviral medication presented a negative, statistically significant association with the presence of OHL (P = 0.002; OR = 8.4). CONCLUSIONS: Prevalence of OHL was 28.8%. Viral load, oral candidiasis, previous use of fluconazole, and systemic acyclovir were determined to be risk factors for OHL. Antiretroviral medication proved to be protective against the development of OHL.  相似文献   
14.
BACKGROUND: In the central nervous system, several neuropeptides are believed to be involved in the pathophysiology of Alzheimer's disease (AD). Indeed, previous studies have documented that glucagon-like peptide 1 (GLP-1) possesses neurotropic properties and can reduce amyloid-beta peptide levels in the brain in vivo. Moreover, the concentrations of neuropeptide Y (NPY) seem to be altered in the cerebrospinal fluid of patients with AD and in subjects with major depression. Finally, among the modifications induced by aging, a dysregulation of the ghrelin-growth hormone (GH) system has been reported. METHODS: We investigated the plasma concentrations of these neuropeptides in 14 subjects with AD. Data obtained from these patients were compared with data from an age- and weight-matched healthy group. RESULTS: No significant differences were found between the two groups in relation to plasma levels of GLP-1, NPY, ghrelin and GH. Peripheral NPY concentrations were positively correlated with ghrelin levels in both groups, and with plasma GLP-1 concentration only in controls. CONCLUSION: On the basis of our results, peripheral levels of these neuropeptides seem not to serve as biochemical markers of AD.  相似文献   
15.
16.
17.
18.
Idiopathic Headache as a Possible Risk Factor for Phantom Tooth Pain   总被引:1,自引:0,他引:1  
Following tooth pulp extirpation, some subjects suffer from persistent pain which affects edentate sites in absence of any local pathology. As regards this peculiar pain, called phantom tooth pain (PTP), what is puzzling is the fact there is a low prevalence of PTP in a very large population showing identical conditions of tooth pulp extirpation. The present investigation indicates that PTP mainly affects migraine (M) and cluster headache (CH) sufferers, whereas it does not affect subjects who have a negative personal and family history for idiopathic headache (IH). These results circumscribe the presence of PTP to a specific section of the population. The present results, besides indicating that PTP may be the result of a peculiar neuronal predisposition relating to IH pathogenesis, suggests some practical therapeutic hints. In fact, successful anti- M and anti-CH prophylactic treatment greatly improve PTP syndrome.  相似文献   
19.
Pressure ulcers are a high-risk, high-volume, and high-cost problem for persons with disabilities. This article describes four tools published in the literature and reports the validity, reliability, strengths, and limitations of each. These tools include the Pressure Ulcer Scale for Healing (PUSH), the Pressure Sore Status Tool (PSST), the Sussman Wound Healing Tool (SWHT), and the Sessing Scale. Rehabilitation nurses should use a consistent framework with accurate quantification to assess, document, and monitor changes in pressure ulcers over time. Such a measurement tool must prove valid for the disabled population in which the tool is used. This will enable healthcare providers to communicate more effectively and evaluate the therapeutic plan of care.  相似文献   
20.
To evaluate the impact of pregnancy on bone, we studied bone turnover at the first (T1) and third (T3) trimester of gestation in 58 adolescents and 28 healthy adolescents who had never been pregnant. Total body (TB) and lumbar spine (LS) bone mineral density (BMD) and body composition were evaluated by dual-energy X-ray absorptiometry in all control patients (C) and after parturition in 28 pregnant patients (G). Paired and unpaired t tests, Mann-Whitney and Pearson correlation tests were used. Bone turnover markers were above the reference range for adult women in more than 80% of the adolescents, with no difference between C and G patients at T1. Increase in urinary N-telopeptide crosslinks of type I collagen and serum bone-specific alkaline phosphatase, markers of bone turnover, was seen during pregnancy ( p < 0.0001). Body composition did not differ between groups, but LS BMD, percentage of expected LS BMD, LS Z-score, percentage of expected TB BMD and TB Z-score were lower in G than C patients ( p < 0.05). TB BMD was positively correlated with LS BMD (r2 = 0.52). The inverse correlations between bone markers and LS BMD suggest that the increased bone turnover during pregnancy probably explains the low bone density after parturition. The impact on future peak bone mass must be studied.  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