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   731篇
  免费   50篇
  国内免费   5篇
耳鼻咽喉   6篇
儿科学   32篇
妇产科学   14篇
基础医学   91篇
口腔科学   23篇
临床医学   57篇
内科学   183篇
皮肤病学   55篇
神经病学   27篇
特种医学   11篇
外科学   137篇
综合类   5篇
预防医学   62篇
眼科学   9篇
药学   41篇
中国医学   5篇
肿瘤学   28篇
  2023年   7篇
  2022年   19篇
  2021年   28篇
  2020年   19篇
  2019年   26篇
  2018年   26篇
  2017年   13篇
  2016年   16篇
  2015年   21篇
  2014年   30篇
  2013年   33篇
  2012年   44篇
  2011年   49篇
  2010年   33篇
  2009年   30篇
  2008年   51篇
  2007年   53篇
  2006年   45篇
  2005年   39篇
  2004年   50篇
  2003年   28篇
  2002年   37篇
  2001年   4篇
  2000年   6篇
  1999年   10篇
  1998年   7篇
  1997年   7篇
  1996年   2篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1991年   4篇
  1989年   3篇
  1987年   2篇
  1986年   2篇
  1984年   3篇
  1983年   2篇
  1979年   3篇
  1976年   3篇
  1975年   5篇
  1974年   1篇
  1973年   3篇
  1972年   3篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1968年   2篇
  1967年   1篇
  1962年   1篇
  1923年   1篇
排序方式: 共有786条查询结果,搜索用时 15 毫秒
21.
Glycerol is the main co-product from biodiesel production and has been recognized as a sustainable solvent. Herein, we used glycerol and waste glycerol in synthesis of two bioactive α,β-unsaturated ketones (E,E)-1,5-diphenylpenta-2,4-dien-1-one (1) and (E,E)-2,6-dibenzylidenecyclohexanone (2), using aldol mono- and di-condensation reactions, respectively. Crude yield values were calculated from product mass after precipitation and drying. Purity was measured by High Performance Liquid Chromatography with Photodiode Array (HPLC-PAD) using analytical curves and reference compounds. Glycerol and waste glycerol were able to furnish 1 and 2 in higher crude yields and HPLC-PAD purities values than other protic solvents (ethanol, methanol, PEG-400 and water). In order to investigate reasons of glycerol efficiency when compared to water efficiency, we performed computational calculations using Density Functional Theory (DFT). Theoretical predictions confirmed the E1cB mechanism, as well as favourable energy barrier using glycerol in comparison to water, corroborating their sustainable properties. In addition, waste glycerol from corn and sunflower oil transesterifications were used in the synthesis of 1 and 2 for four recycles, displaying good crude yields and HPLC-purities.  相似文献   
22.
23.
24.
PURPOSE: To describe a case involving perforation of a previously placed aortic Dacron graft by the uncovered proximal stent of a thoracic stent-graft. CASE REPORT: A 76-year-old man with a surgically treated type A dissection presented with residual type B dissection. Thoracic stent-grafting of the entry site was performed successfully. After 2 years, the patient was admitted for evaluation of a non-pulsating parasternal mass. Computed tomography showed a large, hypodense liquid-like mass affecting the mediastinum up to the subcutaneous tissue. A false aneurysm at the proximal end of the stent-graft was observed arising from an aortic perforation by the uncovered stent. One week later, the mass had almost completely resolved, and the patient has been scheduled for close surveillance. CONCLUSION: This case illustrated the importance of thoroughly examining the long-term durability and compatibility of prosthetic materials.  相似文献   
25.
Highly active antiretroviral therapy has decreased the morbidity and mortality of human immunodeficiency virus (HIV) infection, but latently infected cells remain for prolonged periods. CD4(+) CD45RO(+) T cells are a major latent virus reservoir in HIV-infected persons. Replication-competent, latently HIV-infected T cells can be generated in vitro by infecting peripheral blood mononuclear cells with HIV and then eliminating the HIV-producing cells with an anti-CD25 immunotoxin (IT). The CD25(-) latently infected cells then can be eliminated with an anti-CD45RO IT. This study determined whether this IT also could kill latently infected CD4 T cells from HIV-infected persons with or without detectable plasma viremia. The results show that ex vivo treatment of cells from HIV-positive persons by anti-CD45RO IT reduces the frequency of both productively and latently infected cells. In contrast, CD4(+) CD45RA(+) naive T cells and a proportion of CD4(+) CD45RO(lo) memory T cells are spared.  相似文献   
26.
Accurate office blood pressure measurement remains crucial in the diagnosis and management of hypertension worldwide, including Latin America (LA). Office blood pressure (OBP) measurement is still the leading technique in LA for screening and diagnosis of hypertension, monitoring of treatment, and long‐term follow‐up. Despite this, due to the increasing awareness of the limitations affecting OBP and to the accumulating evidence on the importance of ambulatory BP monitoring (ABPM), as a complement of OBP in the clinical approach to the hypertensive patient, a progressively greater attention has been paid worldwide to the information on daytime and nighttime BP patterns offered by 24‐h ABPM in the diagnostic, prognostic, and therapeutic management of hypertension. In LA countries, most of the Scientific Societies of Hypertension and/or Cardiology have issued guidelines for hypertension care, and most of them include a special section on ABPM. Also, full guidelines on ABPM are available. However, despite the available evidence on the advantages of ABPM for the diagnosis and management of hypertension in LA, availability of ABPM is often restricted to cities with large population, and access to this technology by lower‐income patients is sometimes limited by its excessive cost. The authors hope that this document might stimulate health authorities in each LA Country, as well as in other countries in the world, to regulate ABPM access and to widen the range of patients able to access the benefits of this technique.  相似文献   
27.
Leishmania (Viannia) braziliensis, a protozoan parasite widespread in the New World, is responsible for the infection of different mammal orders, including humans. This species is considered to be a major etiological agent of American cutaneous leishmaniasis. A proteomic study was carried out to identify proteins expressed by L. (V.) braziliensis. One hundred and one spots representing 75 protein entries were identified by MALDI-TOF-TOF. Isoelectric point values estimated by gel electrophoresis matched closely with predicted values, although some discrepancies existed suggesting that post-translational protein modifications may be common in L. braziliensis. Moreover, 20 hypothetical proteins were experimentally identified. Identified proteins were classified into 15 groups according to biological process. Among the proteins identified, approximately 40% have not been previously reported in a proteomic map of Leishmania. In addition, a number of potential virulence factors and drug targets were identified in this protein map, including some proteins associated with the metastatic phenotype. This study describes the first compilation of a proteomic reference map for L. braziliensis (pI 4-7, M(r) 10-130 kDa) and provides a very useful tool for comparative studies of strains isolated from patients presenting different clinical manifestations of leishmaniasis as well as a potential tool to identify markers for clinical diagnosis, therapeutics, and prognosis.  相似文献   
28.
29.
The role of rhinoviruses (RVs) in children with clinical syndromes not classically associated with RV infections is not well understood. We analyzed a cohort of children ≤21 years old who were PCR+ for RV at a large Pediatric Hospital from 2011 to 2013. Using univariate and multivariable logistic regression, we analyzed the associations between demographic, clinical characteristics, microbiology data, and clinical outcomes in children with compatible symptoms and incidental RV detection. Of the 2473 children (inpatients and outpatients) with an RV+ PCR, 2382 (96%) had compatible symptoms, and 91 (4%) did not. The overall median age was 14 months and 78% had underlying comorbidities. No differences in RV viral loads were found according to the presence of compatible symptoms, while in children with classic RV symptoms, RV viral loads were higher in single RV infections versus RV viral co-infections. Bacterial co-infections were more common in RV incidental detection (7.6%) than in children with compatible symptoms (1.9%, p < 0.001). The presence of compatible symptoms independently increased the odds ratio (OR, 95% CI) of hospitalization 4.8 (3.1–7.4), prolonged hospital stays 1.9 (1.1–3.1), need for oxygen 12 (5.8–25.0) and pediatric intensive care unit (PICU) admission 4.13 (2.0–8.2). Thus, despite comparable RV loads, disease severity was significantly worse in children with compatible symptoms.  相似文献   
30.
The Cuatro Ciénegas Basin (CCB) in the central part of the Chihuahan desert (Coahuila, Mexico) hosts a wide diversity of microorganisms contained within springs thought to be geomorphological relics of an ancient sea. A major question remaining to be answered is whether bacteria from CCB are ancient marine bacteria that adapted to an oligotrophic system poor in NaCl, rich in sulfates, and with extremely low phosphorus levels (<0.3 μM). Here, we report the complete genome sequence of Bacillus coahuilensis, a sporulating bacterium isolated from the water column of a desiccation lagoon in CCB. At 3.35 Megabases this is the smallest genome sequenced to date of a Bacillus species and provides insights into the origin, evolution, and adaptation of B. coahuilensis to the CCB environment. We propose that the size and complexity of the B. coahuilensis genome reflects the adaptation of an ancient marine bacterium to a novel environment, providing support to a “marine isolation origin hypothesis” that is consistent with the geology of CCB. This genomic adaptation includes the acquisition through horizontal gene transfer of genes involved in phosphorous utilization efficiency and adaptation to high-light environments. The B. coahuilensis genome sequence also revealed important ecological features of the bacterial community in CCB and offers opportunities for a unique glimpse of a microbe-dominated world last seen in the Precambrian.  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