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   161249篇
  免费   9589篇
  国内免费   920篇
耳鼻咽喉   1572篇
儿科学   5333篇
妇产科学   3876篇
基础医学   23558篇
口腔科学   4814篇
临床医学   14954篇
内科学   35914篇
皮肤病学   3794篇
神经病学   16284篇
特种医学   3764篇
外国民族医学   2篇
外科学   14601篇
综合类   762篇
现状与发展   1篇
一般理论   101篇
预防医学   15735篇
眼科学   2681篇
药学   11495篇
中国医学   547篇
肿瘤学   11970篇
  2024年   204篇
  2023年   1652篇
  2022年   3531篇
  2021年   5913篇
  2020年   3573篇
  2019年   4801篇
  2018年   5392篇
  2017年   4164篇
  2016年   4752篇
  2015年   5252篇
  2014年   6922篇
  2013年   8939篇
  2012年   13311篇
  2011年   13726篇
  2010年   7455篇
  2009年   6259篇
  2008年   10802篇
  2007年   10771篇
  2006年   9916篇
  2005年   9152篇
  2004年   8398篇
  2003年   7452篇
  2002年   6707篇
  2001年   864篇
  2000年   667篇
  1999年   956篇
  1998年   1161篇
  1997年   943篇
  1996年   761篇
  1995年   668篇
  1994年   629篇
  1993年   503篇
  1992年   419篇
  1991年   301篇
  1990年   285篇
  1989年   286篇
  1988年   276篇
  1987年   234篇
  1986年   266篇
  1985年   207篇
  1984年   252篇
  1983年   236篇
  1982年   265篇
  1981年   209篇
  1980年   217篇
  1979年   128篇
  1978年   140篇
  1977年   138篇
  1976年   99篇
  1975年   94篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
231.
BACKGROUND: A single elevated C-reactive protein (CRP) value predicts mortality in haemodialysis (HD) patients, but the relative importance of repeated vs occasional positive systemic inflammatory response findings is not known. METHODS: To assess the influence on survival of occasional inflammation, CRP, serum albumin (S-Alb) and fibrinogen were analysed bimonthly in 180 HD patients (54% male, 49+/-14 years). Clinically significant inflammation was defined as CRP >5.1 mg/l, based on the receiver operating characteristics curve for CRP as predictor of death. Based on four consecutive measurements of CRP, patients were assigned into three groups: group 1 (n = 74; 41%), no inflammation (CRP < or = 5.1 mg/l in all measurements); group 2 (n = 65; 36%), occasional inflammation (1-3 measurements of CRP > 5.1 mg/l); and group 3 (n = 41; 23%), persistent inflammation (all measurements of CRP >5.1 mg/l). The nutritional status was evaluated by subjective global assessment (SGA) and body mass index (BMI), and the survival (21 months of follow-up) by Kaplan-Meier curve and Cox model. RESULTS: The median and range of CRP values (mg/l) for group 1, 2 and 3 were: 3.2 (3.2-5.1), 3.6 (3.2-54.9) and 13.8 (5.2-82), respectively (P<0.001), whereas the prevalence of malnutrition, assessed by SGA and BMI, did not differ significantly between the groups. The survival rate by Kaplan-Meier analysis was significantly different among the groups (chi2 = 12.34; P = 0.0004). Patients in group 3 showed the highest mortality (34%; P = 0.001), compared with group 1 (8%) and group 2 (14%; P = 0.01), respectively, whereas there was no significant difference in mortality between groups 1 and 2. Age, CRP, S-Alb level and SGA were independent predictors of mortality. CONCLUSION: The patients with a persistent elevation of CRP had a higher mortality rate than the patients with occasional CRP elevation. Thus, persistent, rather than occasional, inflammation is an important predictor of death in HD patients.  相似文献   
232.
PDB is genetically heterogeneous. Mutations of the sequestosome1 gene have been reported in sporadic and familial forms of Paget's in patients of French Canadian and British descent. Mutational analyses in different ethnic groups are needed to accurately investigate hereditary diseases. We describe two novel mutations of sequestosome1 in 62 Italian sporadic patients, confirming the role of the encoded protein in this disorder. INTRODUCTION: Paget's disease of bone (PDB) is a relatively common disease of bone metabolism reported to affect up to 3% of whites over 55 years of age. The disorder is genetically heterogeneous, and at present, there is scientific evidence that at least eight different human chromosomal loci are correlated with its pathogenesis. Mutations of the sequestosome1 (SQSTM1) gene were identified as responsible for most of the sporadic and familial forms of Paget in patients of French Canadian and British descent. Such mutations were located at exon 7 and 8 levels, encoding for the ubiquitin protein-binding domain (UBA) and representing a mutational hot spot area. MATERIALS AND METHODS: To verify the involvement of this gene in Italian subjects affected by PDB, we performed mutational analysis in 62 sporadic PDB cases. RESULTS: We described three different mutations at exon 8 level: P392L, already described in the French Canadian population and families predominantly of British descendent, and two novel mutations consisting of the amino acid substitutions M404V and G425R. No significant differences in the clinical history of PDB have been observed in patients with SQSTM1 mutations in respect to those without. CONCLUSIONS: Even though our findings suggest a minor involvement of the SQSTM1 gene in the pathogenesis of sporadic Italian Paget's cases, the identification of different significant mutations within the SQSTM1 gene in unrelated, but clinically similar individuals, offers extremely convincing evidence for a causal relationship between this gene and PDB. Longitudinal studies are needed to assess the penetrance of genotype/phenotype correlations. Our findings confirm the evidence of a clustered mutation area at this level in this disorder.  相似文献   
233.
OBJECTIVES: Recurrent glottic carcinoma after radiotherapy (RT) may be managed by open neck or endoscopic surgery. The impact of endoscopic treatment with CO(2) laser for recurrent glottic carcinoma after RT is reported. METHODS: We present the oncologic and vocal outcomes of a retrospective study based on a series of 16 patients with rT1 and rT2 glottic carcinoma who were endoscopically managed between February 1995 and December 1999 after RT failure. All patients were males with a mean age of 68.7 years (range, 50 to 87 years). Before RT, the lesions had been staged as T1 N0 in 11 patients and T2 N0 in 5, and after RT as rT1 N0 in 12 and rT2 N0 in 4. According to the European Laryngological Society classification, a total of 9 transmuscular, 3 total, and 4 extended cordectomies were performed. Mean follow-up was 45 months (range, 9 to 79 months). RESULTS: Endoscopic salvage surgery was successful in 14 patients. One of them developed a second recurrence and was definitively cured with an additional endoscopic procedure. Two of the 16 patients had recurrent disease after salvage laser surgery and died due to progression of disease. Ultimate local control with laser alone at 3 years was 87.1%, according to the Kaplan-Meier method. Laryngeal preservation was obtained in all survivors after endoscopic rescue surgery. Voice analysis showed a clear correlation between the amount of vocal cord tissue resected and decrease of the vocal outcome. CONCLUSIONS: The present series indicates that selected recurrences after primary RT for T1 and T2 glottic carcinoma are eligible for endoscopic salvage surgery with oncologic results comparable to those with open neck procedures but with a lower complication rate and a favorable functional outcome.  相似文献   
234.
235.
Background: Anesthetic preconditioning (APC) with sevoflurane reduces myocardial ischemia-reperfusion injury. The authors tested whether two brief exposures to sevoflurane would lead to a better preconditioning state than would a single longer exposure and whether dual exposure to a lower (L) concentration of sevoflurane would achieve an outcome similar to that associated with a single exposure to a higher (H) concentration.

Methods: Langendorff-prepared guinea pig hearts were exposed to 0.4 mm sevoflurane once for 15 min (H1-15; n = 8) or 0.4 mm (H2-5; n = 8) or 0.2 mm sevoflurane (L2-5; n = 8) twice for 5 min, with a 5-min washout period interspersed. Sevoflurane was then washed out for 20 min before 30 min of global no-flow ischemia and 120 min of reperfusion. Control hearts (n = 8) were not subjected to APC. Left ventricular pressure was measured isovolumetrically. Ventricular infarct size was determined by tetrazolium staining and cumulative planimetry. Values are expressed as mean +/- SD.

Results: The authors found a better functional return and a lesser percentage of infarction on reperfusion in H2-5 (28 +/- 9%) than in H1-15 (36 +/- 8%; P < 0.05), L2-5 (43 +/- 6%; P < 0.05), or control hearts (52 +/- 7%; P < 0.05).  相似文献   

236.
BACKGROUND: Seroreversion, negativation of anti-hepatitis C virus previously positive, is sometimes found in some chronic hepatitis C-sustained responders (SRs) to antiviral therapy. AIMS: To determine the probability of seroreversion in SR treatment with Interferon and Ribavirin, and lymphocyte T helper (CD4+) reactivity to HCV antigens. METHODS: Thirty SR were followed on average for 54.8 months. Anti-HCV was tested by third generation test. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood and cultured to evaluate CD4+ proliferation in response to 2 microg/ml of eight HCV recombinant antigens from core, NS3, NS4, NS5 regions. RESULTS: Seroreversion was verified in 23% of patients (7/30), appearing at 47.5+/-24.0 months. The probability of anti-HCV loss in this group was 25% at 56 months after ending therapy. In 57% (4/7), anti-HCV returned to positive. These 7 SR patients with seroreversion also showed weaker CD4+ reactivity in 5% of tests (3/56) than the remaining 23 anti-HCV-positive SRs who showed stronger reactivity in 18% of tests (33/184), P=0.036. CONCLUSIONS: One-quarter of the SR showed seroreversion of anti-HCV and weaker CD4+ specific HCV proliferation than those who remained anti-HCV positive. The data suggest that complete viral eradication is a possible and achievable clinical objective.  相似文献   
237.
Ischemia negatively affects mitochondrial function by inducing the mitochondrial permeability transition (MPT). The MPT is triggered by oxidative stress, which occurs in mitochondria during ischemia as a result of diminished antioxidant defenses and increased reactive oxygen species production. It causes mitochondrial dysfunction and can ultimately lead to cell death. Therefore, drugs able to minimize mitochondrial damage induced by ischemia may prove to be clinically effective. We analyzed the effect of carvedilol, a beta-blocker with antioxidant properties, on mitochondrial dysfunction. Carvedilol decreased levels of TBARS (thiobarbituric acid reactive substances), an indicator of oxidative stress, which is consistent with its antioxidant properties. Regarding cell death by apoptosis, although ischemia did increase caspase-8-like activity, there were no changes in caspase-3-like activity, which is activated downstream of caspase-8; this may indicate that the apoptotic cascade is not activated by 60 minutes of ischemia. We conclude that carvedilol protects ischemic mitochondria by preventing oxidative mitochondrial damage, and, by so doing, it may also inhibit the formation of the MPT pore.  相似文献   
238.
239.
This paper is part of a systematic literature review and presents methodological issues within studies, investigating therapeutic applications of music in cancer patients. This review focuses on published international research from the USA, Canada, Australia and European countries using four electronic databases: PSYCHINFO, WEB OF SCIENCE, MEDLINE and SCIENCEDIRECT. Thirty-two papers were identified and each paper was coded in terms of sample type, basic research question, research design and methodological details, results and implications for future research. This paper addresses questions related to study design and methodology. It explores and discusses the relative advantages and disadvantages of various approaches.  相似文献   
240.
An unusual association with Raynaud's phenomenon   总被引:1,自引:1,他引:0  
A 36-yr-old lady with a year of typical Raynaud's and polyarthralgiahad a normal examination other than cold peripheries and bloodpressure of  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