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   1597篇
  免费   81篇
  国内免费   1篇
耳鼻咽喉   5篇
儿科学   52篇
妇产科学   14篇
基础医学   212篇
口腔科学   21篇
临床医学   161篇
内科学   484篇
皮肤病学   44篇
神经病学   74篇
特种医学   54篇
外科学   160篇
综合类   75篇
预防医学   91篇
眼科学   13篇
药学   104篇
中国医学   3篇
肿瘤学   112篇
  2023年   9篇
  2022年   12篇
  2021年   29篇
  2020年   12篇
  2019年   31篇
  2018年   33篇
  2017年   21篇
  2016年   26篇
  2015年   30篇
  2014年   42篇
  2013年   53篇
  2012年   73篇
  2011年   85篇
  2010年   52篇
  2009年   49篇
  2008年   98篇
  2007年   135篇
  2006年   93篇
  2005年   64篇
  2004年   55篇
  2003年   65篇
  2002年   50篇
  2001年   42篇
  2000年   51篇
  1999年   44篇
  1998年   8篇
  1997年   7篇
  1996年   19篇
  1995年   9篇
  1993年   10篇
  1992年   23篇
  1991年   26篇
  1990年   27篇
  1989年   32篇
  1988年   19篇
  1987年   17篇
  1986年   23篇
  1985年   14篇
  1984年   20篇
  1983年   11篇
  1982年   8篇
  1981年   9篇
  1979年   11篇
  1978年   7篇
  1976年   9篇
  1975年   8篇
  1974年   14篇
  1972年   8篇
  1970年   6篇
  1966年   11篇
排序方式: 共有1679条查询结果,搜索用时 15 毫秒
21.
Summary This is the second of three papers describing the use of electron microscopy and antigenic analyses intended to characterize and place in taxa more than 60 previously unclassified viruses. The first paper of the series describes the viruses we classified as provisional members of the familiesArenaviridae, Paramyxoviridae, orPoxviridae; another paper, published separately, discusses theRhabdoviridae. In this paper we report that electron microscopy provided sufficient evidence to place 17 of these viruses (Belem, Erve, Estero Real, Mojui dos Campos, Nyando, Odrenisrou, Okola, Pacora, Para, Santarem, Tanga, Telok Forest, Termeil, Thiafora, Thottapalayam, Wanowrie, and Yacaaba) in the familyBunyaviridae and to support the observations of others that Yogue and Kasokero viruses are members of this virus family. Subsequent antigenic studies allowed us to place some of these viruses in recognized antigenic groups and to establish new antigenic groups for others.  相似文献   
22.
Blood glucose measurement by infrared spectroscopy   总被引:2,自引:0,他引:2  
For the development of an implantable artificial endocrine pancreas, a sensor for blood glucose measurement is needed providing a long-term stability. This goal can be achieved by the application of infrared spectroscopy which, unlike electrochemical sensors, responds directly to the glucose molecule. An investigation under physiological conditions revealed five glucose absorption bands in the near and middle infrared range. These are 1040, 1085, 1109, 1160 and 1365 cm-1. Only the 1040 cm-1 frequency coincides with none of the other infrared-active blood substances like proteins, lipids and urea. Nevertheless, the other absorption bands too, especially the 1109 cm-1 frequency, can be used for blood glucose measurement, if the superimposed absorptions are compensated. Methods for the compensation have been found. Technically feasible embodiments of an infrared glucose sensor are described.  相似文献   
23.
The acute phase protein, C-reactive protein (CRP), when heat-aggregated (Agg-CRP), potentiates immunoglobulin G (IgG) Fc receptor-mediated luminol-enhanced chemiluminescence (CL) in human monocytes and neutrophils. Luminol-CL is a sensitive measure of phagocyte respiratory burst activity; however, the nature of oxidative products contributing to the light emission and their site of generation remain incompletely defined. To more precisely describe the oxidative burst of monocytes and neutrophils to Agg-CRP, superoxide anion release was measured by cytochrome c reduction. In addition, the extracellular release of hydrogen peroxide was distinguished from hydrogen peroxide generation using a phenol red oxidation assay. Finally, a flow cytometric determination of dichlorofluorescein (DCFH) oxidation was employed as an index of intracellular peroxide production. Although Agg-CRP alone did not stimulate hydrogen peroxide generation by either monocytes or neutrophils, it significantly enhanced hydrogen peroxide generation in response to heat-aggregated IgG (Agg-IgG). In contrast, Agg-CRP did not enhance the extracellular release of either hydrogen peroxide or superoxide anion from Agg-IgG-stimulated cells. The capacity of Agg-CRP to enhance selectively intracellular oxidative product generation was confirmed when measuring DCFH oxidation in Agg-IgG-stimulated cells. To evaluate whether this selective enhancement of intracellular oxidative events could be attributed, at least in part, to a scavenging effect of Agg-CRP, a cell-free oxygen radical-generating system was employed. Agg-CRP did not significantly diminish the lucigenin-amplified CL response induced by the xanthine/xanthine oxidase reaction. These results indicate that although Agg-CRP enhances the intracellular generation of reactive oxygen intermediates by monocytes and neutrophils, extracellular release of those products is not influenced by cell interaction with Agg-CRP. It is tempting to speculate that CRP can selectively boost the microbicidal activities of monocytes and neutrophils within an inflammatory site by amplifying the intracellular generation of reactive oxygen products without increasing damage to surrounding normal tissues.  相似文献   
24.
PurposeAbout half of pediatric blunt trauma patients undergo an abdominopelvic computed tomographic (CT) scan, while few of these require intervention for an intraabdominal injury. We evaluated the effectiveness of an evidence-based guideline for blunt abdominal trauma at a Level I pediatric trauma center.MethodsPediatric blunt trauma patients (n = 998) age 0–15 years who presented from the injury scene were evaluated over a 10 year period. After five years, we implemented our guideline in which the decision for CT was standardized based on mental status, abdominal examination, and laboratory results (alanine aminotransferase, aspartate aminotransferase, hemoglobin, urinalysis).ResultsThere were no differences in age, GCS, SIPA or ISS scores between the patients before or after guideline implementation. Nearly half of the patients (48.3%) underwent CT scan before guideline implementation compared to 36.7% after (p < 0.0002). There was no difference in ISS (p = 0.44) between CT scanned patients in either group. No statistical differences were found in rate of intervention (p = 0.20), length of stay (p = 0.65), or readmission rate (0.2%) before versus after guideline implementation. There were no missed injuries.ConclusionImplementation of an evidence-based clinical guideline for pediatric patients with blunt abdominal trauma decreases the rate of CT utilization while accurately identifying significant injuries.Level of evidenceIII.  相似文献   
25.
The management of choledocholithiasis in children and teenagers is often a two-procedure process with laparoscopic cholecystectomy (LC) and either pre- or post-operative endoscopic retrograde cholangiopancreatography (ERCP). The addition of laparoscopic common bile duct exploration (LCBDE) during LC can provide definitive treatment for choledocholithiasis during a single anesthetic event. In an effort to minimize sedation and radiation exposure from fluoroscopy, we have employed dilating balloons via a transcystic approach to stretch the sphincter of Oddi with subsequent ductal flushing. We describe the technique of balloon sphincteroplasty as a straightforward adjunct within the pediatric surgeon's skill set to manage choledocholithiasis during LC and our clinical experience.  相似文献   
26.
Monoclonal antibodies Leu 11a (CD16) and Leu 19 (CD56) were tested for reactivity with cells from 36 patients with acute myelogenous leukemia (AML) using two-colour flow cytometry. Blast cells were identified by a broad panel of monoclonal antibodies. In 33% (12/36) the monoclonal antibody Leu 19, which has been demonstrated to bind to the 140 kD isoform of the human neural cellular adhesion molecule N-CAM, found on peripheral natural killer (NK)-cells, neuroectodermal cells, activated T-cells, and myeloma cells, was shown to bind strongly to the leukemic cells. The monoclonal antibody Leu 11a, which recognizes a surface differentiation antigen associated with the low affinity FcRIII for IgG, expressed on NK-cells, granulocytes and macrophages were found to bind to leukemic cells of four of the 12 Leu-19 positive cases. 50% (6/12) of Leu-19 positive patients were classified as having M4 according to the French-American-British (FAB) morphology criteria. The potential diagnostic and clinical importance of CD 56 and/or CD 16 expression in acute myelogenous leukemia is presently under investigation.  相似文献   
27.
The number of acute flaccid paralysis (AFP) cases reported to World Health Organization (WHO) decreased from 1988 (48 cases) to 1996 (8 cases), but the real endemic situation of poliomyelitis is unknown. Cases are under or misreported. Very often, notifications are delayed; virological investigations of the etiology could not be performed as well as the environment studies and the immunization ripostes. In 1996, only one AFP case was confirmed by isolation of wild poliovirus. The immunization coverage in children under one by OPV (3 doses) was 73.0% in 1996 from the statistics of the Public Health Services but only 54.7% from randomized studies. The eradication of poliomyelitis by the year 2000 has engaged Madagascar in the disease prevention by improving the immunization coverage within the Expanded Immunization Programme in association with the Organization of National Immunization Days in October and November 1997. Likewise, the Virological Unit of the Pasteur Institute was recognized as the National WHO Reference Centre for Polio.  相似文献   
28.
29.
An 18-year-old woman with bilateral pheochromocytomas and an asymptomatic islet cell adenoma of the pancreas represents the 11th patient to be described with this combination of endocrine tumors. No other components of any multiple endocrine adenomatosis (MEA) syndromes were present. Because of this "overlap syndrome," in which tumors that have traditionally been considered to be components of separate and mutually exclusive MEA syndromes have occurred concomitantly in the same patient, a question is raised regarding the validity of a rigid classification of these various MEA syndromes. The possibility of a pancreatic tumor should be kept in mind in any patient with a pheochromocytoma, especially if it is bilateral of multicentric in origin.  相似文献   
30.
BACKGROUND: The goal of this study was to investigate psychosocial disability in relation to depressive symptom severity during the long-term course of unipolar major depressive disorder (MDD). METHODS: Monthly ratings of impairment in major life functions and social relationships were obtained during an average of 10 years' systematic follow-up of 371 patients with unipolar MDD in the National Institute of Mental Health Collaborative Depression Study. Random regression models were used to examine variations in psychosocial functioning associated with 3 levels of depressive symptom severity and the asymptomatic status. RESULTS: A progressive gradient of psychosocial impairment was associated with a parallel gradient in the level of depressive symptom severity, which ranges from asymptomatic to subthreshold depressive symptoms to symptoms at the minor depression/dysthymia level to symptoms at the MDD level. Significant increases in disability occurred with each stepwise increment in depressive symptom severity. CONCLUSIONS: During the long-term course, disability is pervasive and chronic but disappears when patients become asymptomatic. Depressive symptoms at levels of subthreshold depressive symptoms, minor depression/ dysthymia, and MDD represent a continuum of depressive symptom severity in unipolar MDD, each level of which is associated with a significant stepwise increment in psychosocial disability.  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