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   2617篇
  国内免费   68篇
  完全免费   243篇
  综合类   2928篇
  2018年   21篇
  2017年   15篇
  2016年   42篇
  2015年   117篇
  2014年   282篇
  2013年   356篇
  2012年   431篇
  2011年   398篇
  2010年   209篇
  2009年   230篇
  2008年   188篇
  2007年   174篇
  2006年   114篇
  2005年   69篇
  2004年   51篇
  2003年   51篇
  2002年   55篇
  2001年   24篇
  2000年   32篇
  1999年   25篇
  1998年   9篇
  1997年   3篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1993年   2篇
  1992年   4篇
  1991年   10篇
  1990年   2篇
  1989年   6篇
  1988年   2篇
排序方式: 共有2928条查询结果,搜索用时 62 毫秒
1.
目的 探讨无创通气在慢性阻塞性肺疾病急性发作伴呼吸衰竭中的应用。方法 将 5 0例慢性阻塞性肺疾病急性发作伴Ⅱ型呼吸衰竭患者随机分为 2组 ,每组 2 5例 ,在进行抗感染、平喘、祛痰等常规治疗的同时 ,分别予持续静脉滴注可拉明及Bi PAP呼吸机无创通气治疗 4h。观察血气分析变化和临床结果。结果 经可拉明治疗 4h后 ,患者血 pH值和动脉血二氧化碳分压 (PaCO2 )较治疗前均无明显变化 (P >0 .0 5 ) ,而使用Bi PAP呼吸机治疗 4h后 ,PaCO2 明显下降 (P <0 .0 1) ,pH明显上升 (P <0 .0 1)。治疗前后两组动脉血氧分压(PaO2 )均有明显增高 (P <0 .0 1) ,且Bi PAP呼吸机治疗 4h较经可拉明治疗 4h的PaO2 增高更明显 (P <0 .0 1)。结论 Bi PAP呼吸机适用于慢性阻塞性肺疾病急性发作伴呼吸衰竭患者 ,其改善二氧化碳储留和低氧血症的疗效明显优于呼吸兴奋剂 ,且使用方便 ,患者易接受 ,还可缩短治疗时间 ,使部分患者能免于气管插管  相似文献
2.
为探讨丹参对自发性高血压大鼠(SHR)心肌纤维化的作用及其可能机制,以WKY大鼠为阴性对照,SHR大鼠为SHR阳性对照,观察丹参对SHR收缩压、胶原含量及心脏左心室醛固酮(ALD)、NO、超氧化物歧化酶(SOD)含量影响。结果显示:丹参组除收缩压(SBP)明显高于WKY组与SHR组无明显区别外,左室Ⅰ、Ⅲ型胶原及ALD含量明显低于SHR组,而明显高于WKY组;NO、SOD含量则明显高于SHR组,但仍明显低于WKY组(P<0.05)。结果提示:丹参具有预防和逆转自发性高血压大鼠心肌纤维化作用,其机制可能与抑制胶原合成,促进心脏局部胶原分解、抑制心肌局部醛固酮生成、改善心肌血液供应、调节氧自由基代谢等多方面的作用有关。  相似文献
3.
Context  Arterial puncture closing devices (APCDs) were developed to replace standard compression at the puncture site and to shorten bed rest following percutaneous coronary intervention. Objective  To assess the safety and efficacy of APCDs (Angioseal, Vasoseal, Duett, Perclose, Techstar, Prostar) compared with standard manual compression in patients undergoing coronary angiography or percutaneous vascular interventions. Data Sources  A systematic literature search of MEDLINE (1966-January 2003), EMBASE (1989-January 2003), PASCAL (1996-January 2003), BIOSIS (1990-January 2003), and CINHAL (1982-January 2003) databases and the Cochrane Central Register of Controlled Trials for relevant articles in any language. Study Selection  Included randomized controlled trials reporting vascular complications at the puncture site (hematoma, bleeding, arteriovenous fistula, pseudoaneurysm) and efficacy (time to hemostasis, time to ambulation, time to discharge from hospital). Data Extraction  Two reviewers abstracted the data independently and in duplicate. Disagreements were resolved by discussion among at least 3 reviewers. The most important criteria were adequacy of allocation concealment, whether the analysis was according to the intention-to-treat principle, and if person assessing the outcome was blinded to intervention group. Random-effects models were used to pool the data. Data Synthesis  Thirty trials met the selection criteria and included up to 4000 patients. When comparing any APCD with standard compression, the relative risk (RR) of groin hematoma was 1.14 (95% confidence interval [CI], 0.86-1.51; P = .35); bleeding, 1.48 (95% CI, 0.88-2.48; P = .14); developing an arteriovenous fistula, 0.83 (95% CI, 0.23-2.94; P = .77); and developing a pseudoaneurysm at the puncture site, 1.19 (95% CI, 0.75-1.88; P = .46). Time to hemostasis was shorter in the group with APCD compared with standard compression (mean difference, 17 minutes; range, 14-19 minutes), but there was a high degree of heterogeneity among studies. Only 2 studies explicitly reported allocation concealment, blinded outcome assessment, and intention-to-treat analysis. When limiting analyses to only trials that used explicit intention-to-treat approaches, APCDs were associated with a higher risk of hematoma (RR, 1.89; 95% CI, 1.13-3.15) and a higher risk of pseudoaneurysm (RR, 5.40; 95% CI, 1.21-24.5). Conclusions  Based on this meta-analysis of 30 randomized trials, many of poor methodological quality, there is only marginal evidence that APCDs are effective and there is reason for concern that these devices may increase the risk of hematoma and pseudoaneurysm.   相似文献
4.
CONTEXT: Severe, uncompensated, traumatic hemorrhagic shock causes significant morbidity and mortality, but resuscitation with an oxygen-carrying fluid might improve patient outcomes. OBJECTIVE: To determine if the infusion of up to 1000 mL of diaspirin cross-linked hemoglobin (DCLHb) during the initial hospital resuscitation could reduce 28-day mortality in traumatic hemorrhagic shock patients. DESIGN AND SETTING: Multicenter, randomized, controlled, single-blinded efficacy trial conducted between February 1997 and January 1998 at 18 US trauma centers selected for their high volume of critically injured trauma patients, but 1 did not enroll patients. PATIENTS: A total of 112 patients with traumatic hemorrhagic shock and unstable vital signs or a critical base deficit, who had a mean (SD) patient age of 39 (20) years. Of the infused patients, 79% were male and 56% were white. An exception to informed consent was used when necessary. INTERVENTION: All patients were to be infused with 500 mL of DCLHb or saline solution. Critically ill patients who still met entry criteria could have received up to an additional 500 mL during the 1-hour infusion period. MAIN OUTCOME MEASURES: Twenty-eight day mortality, 28-day morbidity, 48-hour mortality, and 24-hour lactate levels. RESULTS: Of the 112 patients, 98 (88%) were infused with DCLHb or saline solution. At 28 days, 24 (46%) of the 52 patients infused with DCLHb died, and 8 (17%) of the 46 patients infused with the saline solution died (P = .003). At 48 hours, 20 (38%) of the 52 patients infused with DCLHb died and 7 (15%) of the 46 patients infused with the saline solution died (P = .01). The 28-day morbidity rate, as measured by the multiple organ dysfunction score, was 72% higher in the DCLHb group (P = .03). There was no difference in adverse event rates or the 24-hour lactate levels. CONCLUSIONS: Mortality was higher for patients treated with DCLHb. Although further analysis should investigate whether the mortality difference was solely due to a direct treatment effect or to other factors, DCLHb does not appear to be an effective resuscitation fluid.  相似文献
5.
急性百草枯中毒所致急性肺损伤机制研究   总被引:28,自引:2,他引:26  
目的从病理学改变、酶学指标、肺组织细胞内钙离子浓度变化等方面,探讨急性百草枯中毒的损伤机制。方法取SD大鼠36只,随机分为2组,实验组大鼠腹腔内注射百草枯20mg/kg,用无菌生理盐水配成5mg/mL的溶液,一次性染毒。对照组大鼠腹腔内注入等体积无菌生理盐水。在6个不同时间点观察其肺组织病理学改变,测量肺组织匀浆内的丙二醛(MDA)含量、超氧化物歧化酶(SOD)活力及肺组织细胞内钙离子浓度变化。结果百草枯中毒可引起弥漫性毛细血管内皮细胞和肺泡上皮细胞损害,主要表现为肺泡水肿、出血、透明膜形成和程度不等的肺泡炎,炎症细胞浸润;肺组织匀浆内MDA含量显著高于对照组(P<0·01);SOD活力下降(P<0·01);肺组织细胞浆内钙离子浓度明显升高,与对照组比较差异有统计学意义(P<0·01),以第2~4d明显,钙离子荧光强度分别为82·91±28·68和55·42±29·61。结论急性百草枯中毒的损伤机制可能与联吡啶阳离子产生反应态氧、胞内钙稳态失衡有关,最终导致不可逆的肺间质纤维化。  相似文献
6.
Objective To investigate the effects of magnesium sulfate on neuron apoptosis and the expressions of caspase-3,bax and bcl-2 after cerebral ischemia-reperfusion injury. Methods Thirty-six gerbils were randomly divided into three groups: Sham-operation group (So, n=12), ischemia-reperfusion group (I-R, n=12) and magnesium sulfate group (Ms, n=12). The neuron apoptosis was detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-fluorescence nick end labeling (TUNEL stain), and the protein expressions of caspase-3, bax and bcl-2 were detected by immunohistochemisty stain.Results Apoptotic neurons and the expressions of caspase-3 and bax were significantly increased in I-R and Ms groups, compared with those in So group. Apoptotic neurons and the expressions of bax and caspase-3 in Ms group were significantly less than those in I-R group. There was no significant difference in the expression of bcl-2 among three groups.Conclusions Magnesium sulfate decreases neuron apoptosis after cerebral ischemia-reperfusion injury, which may be related with the suppressed expressions of caspase-3 and bax.  相似文献
7.
产碳青霉烯酶KPC-2肺炎克雷伯菌局部流行   总被引:22,自引:0,他引:22  
目的 了解我院对碳青霉烯类抗生素敏感性下降的肺炎克雷伯茵的耐药机制及其同源性分析.方法 收集2006年3月~9月我院对碳青霉烯类抗生素敏感性下降的肺炎克雷伯菌共10株,采用Etest法测定细菌对各抗菌药物的最低抑菌浓度(MIC);通过等电聚焦电泳(IEF)检测所产生的β-内酰胺酶.并通过聚合酶链反应(PCR)及序列分析确定其基因型;接合试验和Southern杂交进行基因定位;采用脉冲场凝胶电泳(PFGE)对这些菌株进行同源性分析.结果 10株肺炎克雷伯菌均产KPC-2(pl 6.7)、DHA-1(pl 7.8)和SHV-28(pl 7.6),其中3株同时产TEM-1广谱酶(pl 5.4).blaKPC-2位于60kb左右可接合性质粒上.10株菌株对β-内酰胺类抗生素呈多重耐药,但对多黏菌素,替加环素,复方SMZ敏感.PFGE证实为同一克隆株的传播.结论 质粒介导的KPC-2造成肺炎克雷伯菌对碳青霉烯类抗生素敏感性下降.并在我院短暂流行;携带KPC-2基因的临床菌株同时携带多种耐药基因.  相似文献
8.
Coronary perfusion pressure (CPP), the aortic-to-right atrial pressure gradient during the relaxation phase of cardiopulmonary resuscitation, was measured in 100 patients with cardiac arrest. Coronary perfusion pressure and other variables were compared in patients with and without return of spontaneous circulation (ROSC). Twenty-four patients had ROSC. Initial CPP (mean +/- SD) was 1.6 +/- 8.5 mm Hg in patients without ROSC and 13.4 +/- 8.5 mm Hg in those with ROSC. The maximal CPP measured was 8.4 +/- 10.0 mm Hg in those without ROSC and 25.6 +/- 7.7 mm Hg in those with ROSC. Differences were also found for the maximal aortic relaxation pressure, the compression-phase aortic-to-right atrial gradient, and the arterial PO2. No patient with an initial CPP less than 0 mm Hg had ROSC. Only patients with maximal CPPs of 15 mm Hg or more had ROSC, and the fraction of patients with ROSC increased as the maximal CPP increased. A CPP above 15 mm Hg did not guarantee ROSC, however, as 18 patients whose CPPs were 15 mm Hg or greater did not resuscitate. Of variables measured, maximal CPP was most predictive of ROSC, and all CPP measurements were more predictive than was aortic pressure alone. The study substantiates animal data that indicate the importance of CPP during cardiopulmonary resuscitation.  相似文献
9.
Context  Previous surveillance studies have documented increasing rates of antimicrobial resistance in US intensive care units (ICUs) in the early 1990s. Objectives  To assess national rates of antimicrobial resistance among gram-negative aerobic isolates recovered from ICU patients and to compare these rates to antimicrobial use. Design and Setting  Participating institutions, representing a total of 43 US states plus the District of Columbia, provided antibiotic susceptibility results for 35 790 nonduplicate gram-negative aerobic isolates recovered from ICU patients between 1994 and 2000. Main Outcome Measures  Each institution tested approximately 100 consecutive gram-negative aerobic isolates recovered from ICU patients. Organisms were identified to the species level. Susceptibility tests were performed, and national fluoroquinolone consumption data were obtained. Results  The activity of most antimicrobial agents against gram-negative aerobic isolates showed an absolute decrease of 6% or less over the study period. The overall susceptibility to ciprofloxacin decreased steadily from 86% in 1994 to 76% in 2000 and was significantly associated with increased national use of fluoroquinolones. Conclusions  This study documents the increasing incidence of ciprofloxacin resistance among gram-negative bacilli that has occurred coincident with increased use of fluoroquinolones. More judicious use of fluoroquinolones will be necessary to limit this downward trend.   相似文献
10.
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