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   3074篇
  免费   183篇
  国内免费   9篇
耳鼻咽喉   46篇
儿科学   200篇
妇产科学   69篇
基础医学   430篇
口腔科学   29篇
临床医学   222篇
内科学   586篇
皮肤病学   88篇
神经病学   129篇
特种医学   108篇
外科学   335篇
综合类   172篇
预防医学   290篇
眼科学   52篇
药学   271篇
中国医学   46篇
肿瘤学   193篇
  2023年   22篇
  2022年   55篇
  2021年   114篇
  2020年   58篇
  2019年   50篇
  2018年   82篇
  2017年   53篇
  2016年   70篇
  2015年   89篇
  2014年   119篇
  2013年   134篇
  2012年   195篇
  2011年   215篇
  2010年   137篇
  2009年   92篇
  2008年   156篇
  2007年   166篇
  2006年   163篇
  2005年   140篇
  2004年   100篇
  2003年   99篇
  2002年   85篇
  2001年   90篇
  2000年   89篇
  1999年   62篇
  1998年   17篇
  1997年   12篇
  1996年   26篇
  1995年   21篇
  1993年   17篇
  1992年   42篇
  1991年   44篇
  1990年   42篇
  1989年   47篇
  1988年   38篇
  1987年   24篇
  1986年   24篇
  1985年   27篇
  1984年   15篇
  1983年   14篇
  1979年   24篇
  1978年   15篇
  1977年   13篇
  1975年   13篇
  1974年   12篇
  1973年   21篇
  1972年   12篇
  1971年   17篇
  1970年   16篇
  1969年   16篇
排序方式: 共有3266条查询结果,搜索用时 46 毫秒
41.
42.
BACKGROUND: Fragmented QRS (fQRS) on a 12-lead electrocardiogram (ECG) is associated with myocardial scar in patients with coronary artery disease (CAD). OBJECTIVE: We postulated that fQRS is a predictor of cardiac events and mortality in patients who have known CAD or who are being evaluated for CAD. METHODS: The cardiac events (myocardial infarction, need for revascularization, or cardiac death) and all-cause mortality were retrospectively reviewed in 998 patients (mean age 65.5 +/- 11.9 years, male 967) who underwent nuclear stress test. The fQRS on a 12-lead ECG included various RSR' patterns (> or =1 R' prime or notching of S wave or R wave) without typical bundle branch block in 2 contiguous leads corresponding to a major coronary artery territory. RESULTS: All-cause mortality (93 [34.1%] vs 188 [25.9%]) and cardiac event rate (135 [49.5%] vs 200 [27.6%]) were higher in the fQRS group compared with the non-fQRS group during a mean follow-up of 57 +/- 23 months. A Kaplan-Meier survival analysis revealed significantly lower event-free survival for cardiac events (P <.001) and all-cause mortality (P = .02). Multivariate Cox regression analysis revealed that significant fQRS was an independent significant predictor for cardiac events but not for all-cause mortality. The Kaplan-Meier survival analysis showed no significant difference between fQRS and Q waves groups for cardiac events (P = .48) and all-cause mortality (P = .08). CONCLUSION: The fQRS is an independent predictor of cardiac events in patients with CAD. It is associated with significantly lower event-free survival for a cardiac event on long-term follow-up.  相似文献   
43.
44.
Objective:Lead (Pb) is a long-known poison of environment and industrial origin. Its prolonged exposure affects cellular material and alters cellular genetics and produces oxidative damages. In this study, we investigated the exposure of chronic sustained hypoxia or lead acetate alone or in combination with or without supplementation of α-tocopherol on hepatic oxidative and nitrosative stress in rats.Results:Exposure of both lead and hypoxia showed decreased body weight, altered serum lipid profile, oxidant and enzymatic antioxidants status, serum HIF-1α and VEGF concentrations. Simultaneous α-tocopherol supplementation showed beneficial effects to all these alterations. Histopathological observations also showed hepatic degenerative changes after lead or hypoxia exposure either alone or in combination, but remarkable improvement has been noticed after α-tocopherol supplementation.Conclusion:Supplementation of α-tocopherol is beneficial to counter both lead acetate and hypoxia induced hepatic cytotoxicities possibly by reducing oxidative and nitrosative stress.KEY WORDS: α-tocopherol, hypoxia, lead acetate, nitrosative stress, oxidative stress  相似文献   
45.
Pathogens in the gastrointestinal tract exist within a vast population of microbes. We examined associations between pathogens and composition of gut microbiota as they relate to Shigella spp./enteroinvasive Escherichia coli infection. We analyzed 3,035 stool specimens (1,735 nondiarrheal and 1,300 moderate-to-severe diarrheal) from the Global Enteric Multicenter Study for 9 enteropathogens. Diarrheal specimens had a higher number of enteropathogens (diarrheal mean 1.4, nondiarrheal mean 0.95; p<0.0001). Rotavirus showed a negative association with Shigella spp. in cases of diarrhea (odds ratio 0.31, 95% CI 0.17–0.55) and had a large combined effect on moderate-to-severe diarrhea (odds ratio 29, 95% CI 3.8–220). In 4 Lactobacillus taxa identified by 16S rRNA gene sequencing, the association between pathogen and disease was decreased, which is consistent with the possibility that Lactobacillus spp. are protective against Shigella spp.–induced diarrhea. Bacterial diversity of gut microbiota was associated with diarrhea status, not high levels of the Shigella spp. ipaH gene.  相似文献   
46.
Curcumin has been transformed to several diversely substituted bis-pyrrolizidino/thiopyrrolizidino oxindolo/acenaphthyleno curcuminoids via a sequential azomethine ylide cycloaddition reaction using isatins/acenaphthoquinone and proline/thioproline as the reagents. The products were separated via extensive chromatography and characterized by 1D/2D NMR and HRMS analysis.

Curcumin has been transformed to several diversely substituted bis-pyrrolizidino/thiopyrrolizidino oxindolo/acenaphthyleno curcuminoids via a sequential azomethine ylide cycloaddition reaction.  相似文献   
47.
Secretory immunoglobulin A (S-IgA), coproantibody titre (antiamoebic) and IgA, IgG, IgM immunocytes in rectal mucosa were studied in 13 patients with amoebic liver abscess (ALA) prior to and 4-6 weeks after completion of antiamoebic therapy. Ten asymptomatic Entamoeba histolytica cyst passers and 17 healthy age and sex matched volunteers served as controls. Fecal S-IgA levels and counts of IgA bearing immunocytes in mucosa were significantly higher in patients with ALA and cyst passers as compared to healthy controls and showed a significant fall after treatment. Fecal antiamoebic antibodies were high in cyst passers and in cases of ALA after treatment. Raised levels of S-IgA and IgA class immunocyte counts probably indicate a local mucosal immune response directed at containing the infection.  相似文献   
48.
49.
Exercise testing remains a key tool in the management of patientswith ischaemic heart disease (IHD) both in a diagnostic andrehabilitation setting. A familiar scenario involves performingan exercise test to identify inducible ischaemia either to determinewhether IHD is a likely diagnosis or as a prelude to a structuredexercise programme in individuals with a recent acute coronarysyndrome or with chronic symptoms in whom IHD has already beendiagnosed. Consequently, the prospect of prescribing exerciseto patients is a problem faced regularly by clinicians. However,there is still an appropriate level of concern in recommendingan activity which increases myocardial work and may provokean imbalance between myocardial oxygen supply and demand. Thisis despite the risk of exercise  相似文献   
50.
Dextrocardia is a rare clinical phenomenon with a reported incidence of one in 10 000. Consequently, acute coronary syndromes in such patients are rare. When chest pain occurs in this setting, it is important to be aware of the unique problems that may occur if coronary intervention is contemplated. Previous case reports have shown successful attempts at reperfusing one coronary artery percutaneously. In this case, coronary stents were successfully deployed in two vessels of a man with situs inversus, which has not been reported before. Additionally, the angiographic results that followed from successful intervention did not produce the expected haemodynamic and electrocardiographic changes.  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