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   113221篇
  免费   40943篇
耳鼻咽喉   1791篇
儿科学   5122篇
妇产科学   461篇
基础医学   24165篇
口腔科学   6644篇
临床医学   13869篇
内科学   26185篇
皮肤病学   4330篇
神经病学   18170篇
特种医学   5850篇
外科学   14978篇
综合类   1篇
一般理论   8篇
预防医学   7824篇
眼科学   1341篇
药学   9382篇
中国医学   1686篇
肿瘤学   12357篇
  2023年   22篇
  2022年   59篇
  2021年   1528篇
  2020年   5981篇
  2019年   11342篇
  2018年   10911篇
  2017年   12146篇
  2016年   11256篇
  2015年   11151篇
  2014年   10867篇
  2013年   11079篇
  2012年   10252篇
  2011年   10139篇
  2010年   8879篇
  2009年   5356篇
  2008年   5947篇
  2007年   4319篇
  2006年   4147篇
  2005年   3947篇
  2004年   3831篇
  2003年   3495篇
  2002年   3305篇
  2001年   2510篇
  2000年   1355篇
  1999年   228篇
  1998年   15篇
  1997年   16篇
  1996年   19篇
  1995年   12篇
  1994年   10篇
  1993年   9篇
  1992年   9篇
  1991年   16篇
  1990年   5篇
  1988年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This correlational and comparative study explored whether self-reports of self-efficacy and dyspnea perceptions predict the perceived level of functional performance in adults who have chronic obstructive pulmonary disease (COPD). The convenience sample included 97 Caucasian men (52) and women (45). Participants had to have a forced expiratory volume in 1 second (FEV1) of less than 70% predicted, and a FEV1/forced vital capacity (FVC) of less than 70%. Participants were recruited from pulmonary function laboratories and from better breather support groups in a Midwestern state. Three standardized, self-report instruments, COPD Self-Efficacy Scale (CSES), the Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ), and Functional Performance Inventory (FPI) were used to measure the participants' self-report of their perceptions of self-efficacy, dyspnea, and functional performance. Dyspnea predicted 38.1% of the variance in functional performance, with self-efficacy contributing an additional 6.5% to the variance in the total sample. Self-efficacy predicted 36.5% of the variance in functional performance in men, with dyspnea contributing an additional 7.2% to the variance. However, in women, only dyspnea was a significant predictor of functional performance, at 48.5% when both dyspnea and self-efficacy were entered as independent variables. To improve patients' perceptions of functional performance, nurses can use methods such as breathing techniques and upper- and lower-body exercises that increase optimal management of dyspnea. Nurses may increase the self-efficacy of managing dyspnea by helping patients master breathing techniques and exercise through coaching and providing vicarious experiences through patient support groups or pulmonary rehabilitation programs.  相似文献   
92.
A 55‐year‐old‐man had a laparoscopic resection of the sigmoid colon due to colon cancer with submucosal invasion. After the surgery he suffered ileus and had a laparotomy. Six months later he complained of frequent defecation. Colonoscopy confirmed a circular ulcer extending from the anal side of the anastomosis in the sigmoid colon to the mid rectum. Endoscopic ultrasound demonstrated thickening of all layers of the diseased colon and rectum. We diagnosed ischemic colitis. After intravenous drip infusion of prostaglandin, symptoms and colonic stricture gradually improved. Although abdominal angiography revealed a narrowing of the peripheral sigmoid branch of the inferior mesenteric artery, blood flow was unrestricted. Colonoscopy performed 84 days after discharge revealed an ulcer scar.  相似文献   
93.
Results are reported on the regioselective C‐deuteriation of 2‐methyl‐tetralone using a series of D‐sources and tertiary amines as potential mediators. The results presented further aid the understanding of kinetic deuteriation of both ‘base‐containing’ and ‘base‐free’ enolates. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
94.
AIMS: Increased levels of inflammatory biomarkers, especially C-reactive protein (CRP), are associated with increased risk for cardiovascular disease (CVD) events, such as myocardial infarction, stroke, peripheral vascular disease, and sudden cardiac death. Medical interventions that increase CRP levels, such as hormone replacement therapy (HRT) in post-menopausal women, are under increasing scrutiny. The effect of HRT on CRP levels in women with Type 2 diabetes (T2DM) is not well documented, and conflicting conclusions have been reported. The aim of this study was to determine the influence of HRT on women with diabetes in a large cross-sectional study. METHODS: Three hundred and twenty-seven post-menopausal women with T2DM from the Diabetes Heart Study participated. Current use of HRT was determined and serum CRP levels were measured using a high-sensitivity ELISA kit. Generalized estimating equation methods were used to assess the relationship of multiple clinical and lifestyle (e.g. smoking) measures on CRP levels including differences between women taking HRT (HRT+) and not taking HRT (HRT-). RESULTS: Overall serum CRP levels were strongly associated with body mass index (P < 0.0001) and age (P < 0.0001). Of the women, 243 were not using HRT and 84 were using HRT. HRT+ and HRT- women did not differ significantly in measures of clinical traits, with the exception of higher mean low-density lipoprotein cholesterol in HRT- women (P = 0.004). In all models tested, HRT+ women had significantly higher circulating CRP levels, with P-values ranging from 0.0045 to 0.010. CONCLUSIONS: In this study of serum CRP concentration as a function of HRT in women with Type 2 diabetes, there was consistent evidence for increased circulating CRP levels in women receiving oestrogen-containing HRT. Whether HRT-induced increases in CRP can account for the adverse cardiovascular effects of HRT remains to be established; however, based on these data, there is little reason to believe that diabetic women would be spared from such an effect.  相似文献   
95.
AIMS: To investigate the contribution of regulatory T cells and co-stimulatory molecules in CD4(+) T cells to the development of Type 1 diabetes (T1D). METHODS: Twelve patients with T1D, nine patients with systemic lupus erythematosus (SLE), and 12 age-matched healthy control subjects participated. We analysed the proportions of CD25(+)CD4(+) T cells and natural killer T cells (NKT cells), and the expression levels of Foxp3, CTLA-4, CD28, ICOS, PD-1 and BTLA in peripheral blood mononuclear cells and purified CD4(+) T cells. RESULTS: There were no significant differences in the proportions of CD25(+) CD4(+) T cells or NKT cells among the three groups. PD-1 expression levels of peripheral CD4(+) T cells from T1D patients were significantly lower than those from healthy control subjects (P = 0.00066). In contrast, PD-1 expression levels were similar in SLE patients and healthy control subjects. The expression levels of Foxp3, CTLA-4, CD28, ICOS and BTLA were similar in the three groups. CONCLUSIONS: Decreased expression of the PD-1 gene in CD4(+) T cells may contribute to the development and/or maintenance of autoimmune T1D. As the population studied was small and heterogeneous, further studies are required to confirm the findings.  相似文献   
96.
97.
Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17) is a hereditary progressive neurodegenerative disorder. FTDP‐17 was originally defined in Ann Arbor, Michigan, in 1996. Since then, more than 100 families with FTDP‐17 have been described throughout the world, including 18 families identified in Japan. Genetic studies have identified 40 different mutations in the microtubule‐associated protein tau (MAPT) gene. The clinical features of FTDP‐17 are characterized by behavioral, cognitive and motor disturbances that may occur in various combinations and degrees. Neuropathologic examination shows that various degrees of atrophy may be present in the frontal and temporal lobes, basal ganglia, amygdala and hippocampus. All the brains from patients with FTDP‐17 have also shown the presence of tau deposits in neurons and glial cells. Mutations in MAPT may result in the increased splicing of exon 10, leading to 4‐repeat tau depositions in both neurons and glial cells. MAPT mutations outside of exon 10 show 3‐ and 4‐repeat tau deposits, predominantly in neurons with less glial pathology. Neuronal pathology may resemble that of Alzheimer’s disease or Pick’s disease because of the presence of neurofibrillary tangles or Pick‐like bodies, whereas glial pathology may resemble that of progressive supranuclear palsy or corticobasal degeneration because of the presence of coiled bodies, tufted astrocytes or astrocytic plaques. Correlations between genetic mutations and the heterogeneity of clinical and neuropathologic features remain unclear.  相似文献   
98.
ABSTRACT: Background: The percentage of United States’ births delivered by cesarean section has increased rapidly in recent years, even for women considered to be at low risk for a cesarean section. The purpose of this paper is to examine infant and neonatal mortality risks associated with primary cesarean section compared with vaginal delivery for singleton full‐term (37–41 weeks’ gestation) women with no indicated medical risks or complications. Methods: National linked birth and infant death data for the 1998–2001 birth cohorts (5,762,037 live births and 11,897 infant deaths) were analyzed to assess the risk of infant and neonatal mortality for women with no indicated risk by method of delivery and cause of death. Multivariable logistic regression was used to model neonatal survival probabilities as a function of delivery method, and sociodemographic and medical risk factors. Results: Neonatal mortality rates were higher among infants delivered by cesarean section (1.77 per 1,000 live births) than for those delivered vaginally (0.62). The magnitude of this difference was reduced only moderately on statistical adjustment for demographic and medical factors, and when deaths due to congenital malformations and events with Apgar scores less than 4 were excluded. The cesarean/vaginal mortality differential was widespread, and not confined to a few causes of death. Conclusions: Understanding the causes of these differentials is important, given the rapid growth in the number of primary cesareans without a reported medical indication. (BIRTH 33:3 September 2006)  相似文献   
99.
Several isotopomers of ABT‐578 ( I , II , III , and IV ) were prepared starting from different labeled precursors: [5'‐3H]‐tetrazole ( 1 ), [5'‐14C]‐tetrazole ( 2 ), [40‐3H]rapamycin ( 3 ), and [2,11,31‐3H]rapamycin ( 4 ). It was shown that the tritium label at the 40 position of rapamycin is lost during an attempted synthesis of [40‐3H]ABT‐578 ( III ). Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
100.
《Movement disorders》2006,21(6):809-815
Although multiple system atrophy (MSA) is a neurodegenerative disorder leading to progressive disability and decreased life expectancy, little is known about patients' own evaluation of their illness and factors associated with poor health‐related quality of life (Hr‐QoL). We, therefore, assessed Hr‐QoL and its determinants in MSA. The following scales were applied to 115 patients in the European MSA‐Study Group (EMSA‐SG) Natural History Study: Medical Outcome Study Short Form (SF‐36), EQ‐5D, Beck Depression Inventory (BDI), Mini‐Mental state examination (MMSE), Unified MSA Rating Scale (UMSARS), Hoehn & Yahr (H&Y) Parkinson's disease staging scale, Composite Autonomic Symptom Scale (COMPASS), and Parkinson's Disease Sleep Scale (PDSS). Forty‐six percent of patients had moderate to severe depression (BDI ≥ 17); Hr‐QoL scores on the SF‐36 and EQ‐5D were significantly impaired. Pain, the only domain with similar scores in MSA and published PD patients, was reported more frequently in patients with MSA‐P (predominantly parkinsonian motor subtype) than MSA‐C (predominantly cerebellar motor subtype; 76% vs. 50%; P = 0.005). Hr‐QoL scores correlated most strongly with UMSARS motor, COMPASS, and BDI scores but not with MMSE scores, age at onset, or disease duration. The COMPASS and UMSARS activities of daily living scores were moderate‐to‐strong predictors for the SF‐36 physical summary score and the BDI and UMSARS motor scores for the SF‐36 mental summary score. This report is the first study to show that Hr‐QoL is significantly impaired in MSA. Although not all possible factors related to impaired Hr‐QoL in MSA could be assessed, autonomic dysfunction, motor impairment, and depression were most closely associated with poor Hr‐QoL, and therapeutic management, therefore, should concentrate upon these aspects of the disease. © 2006 Movement Disorder Society  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