全文获取类型
收费全文 | 883篇 |
免费 | 46篇 |
国内免费 | 14篇 |
专业分类
儿科学 | 51篇 |
妇产科学 | 5篇 |
基础医学 | 82篇 |
口腔科学 | 17篇 |
临床医学 | 132篇 |
内科学 | 141篇 |
皮肤病学 | 35篇 |
神经病学 | 58篇 |
特种医学 | 220篇 |
外科学 | 67篇 |
综合类 | 38篇 |
预防医学 | 24篇 |
眼科学 | 3篇 |
药学 | 57篇 |
肿瘤学 | 13篇 |
出版年
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 25篇 |
2012年 | 33篇 |
2011年 | 24篇 |
2010年 | 25篇 |
2009年 | 31篇 |
2008年 | 20篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 17篇 |
2004年 | 8篇 |
2003年 | 18篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 26篇 |
1998年 | 40篇 |
1997年 | 50篇 |
1996年 | 38篇 |
1995年 | 42篇 |
1994年 | 24篇 |
1993年 | 31篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 19篇 |
1981年 | 12篇 |
1980年 | 22篇 |
1979年 | 4篇 |
1978年 | 12篇 |
1977年 | 23篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1966年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有943条查询结果,搜索用时 15 毫秒
61.
62.
目的:分析力学刺激体外骨髓间充质干细胞所产生增殖分化等生物学效应的影响及其力化学信号转导途径。资料来源:因特网上检索PubMed数据库中2000-01/2006-06期间有关力学刺激对骨髓干细胞作用效应进展的英文文章,检索词“stem cel1,marrow mesenchymal stem cells,mechanical stimulation,stress”,同时检索CNKI中国知网医学文献数据库2000-01/2006-06期间的相关文章,检索词为“干细胞、骨髓间充质干细胞、机械刺激、应力”。资料选择:对资料进行筛选,选取相关文章查找全文。纳入标准:①骨髓间充质干细胞相关生物学特性。②体外细胞加载的应力分类及相应力学装置的特点。③应力对细胞影响的研究。④能获取文章的全文。排除标准:①较陈旧的文献。②重复研究。资料提炼:共收集关于86篇体外骨髓干细胞及力学干预的相关文献。其中30篇符合纳入标准。资料综合:①骨髓干细胞具有高度增殖及多向分化能力,可通过体外培养、干预作为细胞组织工程的理想种子细胞。②力学刺激是体外调节细胞生物学效应的重要途径,其中力学分类有:流体切应力、静止压应力、张应力、离心力以及单个细胞的吸吮力等,介绍各种力以及相应的力学装置的特点。③骨髓干细胞加载各种应力干预后产生的生物学效应,以及细胞应力学刺激的机制、信号转导途径。结论:力学刺激可影响骨髓间充质干细胞生物学特性,在适当的力学刺激条件下,促进细胞的增殖与分化,为骨组织工程提供新的技术手段,同时也为临床应用牵拉成骨的骨再生过程提供理论依据。 相似文献
63.
Although reactions to granulocyte transfusions in neonates are rarely reported, we observed a near-fatal pulmonary reaction, presumably due to white cell antibodies, in a neonate with Rh hemolytic disease. The hemolytic disease was being treated with exchange transfusions, and at 2 days after the infant's birth, bacterial sepsis was suspected and granulocyte transfusions were begun. The first granulocyte transfusion (Day 3) was uneventful. Five minutes after the beginning of the second granulocyte transfusion (Day 4), severe respiratory distress, hypotension, bradycardia, cyanosis, and acidosis suddenly occurred. The infant's serum obtained after the reaction contained granulocytotoxic and B-lymphocytotoxic antibodies that reacted with leukocytes from the second granulocyte donor. Antibodies could not be detected either in the initial infant serum or in maternal serum. However, an antileukocyte antibody was present in the serum of a parous woman donor. We used plasma from this woman to prepare reconstituted whole blood for the exchange transfusion that we performed immediately preceding the second granulocyte transfusion. Despite the sequence of events, an irrefutable cause-and-effect mechanism could not be established because the properties of the donor and neonatal antibodies were similar, but not identical. However, this catastrophic event emphasizes both the potential for adverse effects of granulocyte transfusions in neonates and the need for caution when transfusing blood from parous women. 相似文献
64.
XAVIER JEANRENAUD JÜRG SCHLÄPFER MARTIN FROMER NICOLE AEBISCHER LUKAS KAPPENBERGER 《Pacing and clinical electrophysiology : PACE》1997,20(2):293-300
Clinical improvement with dual chamber pacing bas largely been reported in patients suffering from hypertrophic obstructive cardiomyopathy and mainly attributed to the reduction of the subaortic pressure gradient. To be effective, pacing must induce a permanent and complete capture of the LV. In two patients of our collective, symptoms (angina and dyspnea NYHA Class III and/or syncopes) persisted or relapsed despite pacing. This was related to the inability to obtain full LV capture due to a too-short native PR interval. RF ablation of the AV junction was therefore performed in botb patients, resulting in permanent AV block in one and prolonged PR interval up to 310 ms in the second. Pacing was thereafter associated with an immediate and significant clinical improvement related to permanent LV capture, whatever the patient's activity. After RF ablation, the AV delay was set up to induce the best LV filling, as assessed by Doppler analysis of mitral flow. Our observations suggest that RF ablation or modification of the AV junction can be a successful procedure in some patients with residual or recurrent symptoms, when the latter result from a loss of capture or from the inability to program an AV delay tbat does not compromise the active component to LV filling. Doppler echocardiography is a simple and effective mean to assess the hemodynamic effect of AV interval modulation in this setting. 相似文献
65.
慢性失眠症患者的思维特点 总被引:1,自引:0,他引:1
目的:观察慢性失眠症患者的认知行为特征和其症状的产生及发展的关系,分析慢性失眠症患者的思维特点。方法:随机抽取北京中医药大学国医堂睡眠障碍门诊2004-01/07失眠症患者90例和配对睡眠正常者90人进行问卷调查,包括匹兹堡睡眠质量指数问卷、关于睡眠的非功能性的信念和态度量表修订版问卷以及思维控制问卷。匹兹堡睡眠质量指数问卷包括7个因子,每个因子按0~3等级记分,得分越高表示睡眠质量越差。关于睡眠的非功能性的信念和态度量表修订版由10个条目组成,5级评分,得分越高表示关于睡眠的非功能性的信念和态度越多。思维控制问卷由30个条目组成,包括6个纬度:认知转移、行为转移、社会支持、担心、惩罚和再评价,每个纬度的得分越高表示使用此种思维控制的方式越多。结果:发放问卷180份,回收完整问卷158份,有效率87.8%。最终病例组和对照组各79人,进入结果分析。①慢性失眠症患者关于失眠的短期影响、长期影响和对于睡眠的控制的非功能性的态度和信念得分均高于对照组(19.48±2.90,14.14±5.87;11.06±1.79,8.11±2.74;7.82±1.44,5.01±2.07;t=9.86,7.25,8.01,P<0.01)。②慢性失眠症患者使用担心和惩罚的思维控制方式得分高于睡眠正常组(10.7±2.6,8.5±2.9;11.6±2.8,9.0±3.1;t=5.08,5.43,P<0.01)。③关于睡眠的非功能性的信念和态度与担心和惩罚的思维控制方式呈正相关(r=0.41,0.24,P<0.01)。结论:对于失眠症患者进行认知行为治疗时,要注意纠正失眠症患者关于睡眠的非功能性的信念和态度,并指导失眠症患者学习有效的思维控制方式。 相似文献
66.
低氧暴露对运动性贫血大鼠抗氧化能力的影响 总被引:2,自引:0,他引:2
目的:观察低氧暴露对运动性贫血大鼠某些抗氧化酶的影响,探讨低氧条件下抗氧化系统的反应是否有利于改善运动性贫血。方法:实验于2005-07/09在广东省高等学校运动生物化学教学重点实验室完成。选择6周龄健康雄性SD大鼠40只,均为运动性贫血动物模型,大鼠适应环境1周后采用6周递增负荷跑台运动方式建立。按随机数字表法分为1h低氧暴露组、2h低氧暴露组和间歇性低氧暴露组、常氧恢复组,每组10只。采用人工常压低氧环境,低氧浓度控制在14.5%左右,按分组每天在常压低氧舱进行1,2h和间歇性低氧暴露(低氧暴露1h,中间间歇3h,再低氧暴露1h),其余时间在舱外常氧中自由活动,每周6d,持续3周。常氧恢复组大鼠在常氧中自由活动。3周后测试运动性贫血大鼠血清丙二醛含量、超氧化物歧化酶活性和血浆过氧化氢酶、谷胱甘肽过氧化酶活性。结果:纳入动物40只,均进入结果分析。①低氧暴露3周后1h低氧暴露组、2h低氧暴露组、间歇性低氧暴露组血清丙二醛含量均显著低于常氧恢复组[分别为(2.62±0.16),(2.60±0.22),(2.55±0.06),(3.36±0.34)μmol/L,P<0.05]。②低氧暴露3周后血清超氧化物歧化酶和血浆谷胱甘肽过氧化酶、过氧化氢酶活性均高于常氧恢复组,2h低氧暴露组与常氧恢复组比较差异有显著性意义[分别为(4239.68±169.53),(3190.30±339.40)μkat/L;(20622.46±2002.07),(15556.44±607.79)μkat/L;(50.01±6.67),(35.17±4.50)μkat/L,P<0.05]。③各低氧暴露组间除2h低氧暴露组血清超氧化物歧化酶活性显著高于1h低氧暴露组外[分别为(4239.68±169.53),(2126.41±161.20)μkat/L,P<0.05],其他指标组间差异无显著性意义(P>0.05)。结论:低氧暴露可提高运动性贫血大鼠机体的抗氧化能力,有利于促进运动性贫血的恢复。 相似文献
67.
Commentary on the safety of red cells preserved in extended-storage media for neonatal transfusions 总被引:2,自引:0,他引:2
Red cells preserved in extended-storage media are the standard product dispensed by many regional blood centers. When the red cells are intended for neonatal transfusion, concern exists about the safety of the relatively high quantities of additives present in these media. Definitive studies to address these concerns are not available. Therefore, to estimate the effects of additives and to delineate circumstances in which they might be harmful, the quantities transfused in defined clinical settings were calculated, and the following recommendations are offered for transfusing infants less than 4 months of age. First, red cells preserved in extended-storage media should present no substantive risks when used for small-volume (approximately 10 mL/kg) transfusions of premature infants and can be used without additional processing. Second, the risks of the most premature neonatal patients or those with severe renal and/or hepatic insufficiency cannot be defined clearly, and, because data are not available to ensure safety for these infants, removal of the additive medium and resuspension of the red cells in saline or albumin solution immediately before transfusion are recommended. Third, following a similar rationale, it seems prudent to avoid using entire units of red cells preserved in extended-storage media in massive transfusion settings (e.g., exchange transfusion, cardiac surgery, and extracorporeal membrane oxygenation). In these settings, the preservative medium should be removed and the red cells resuspended in the fluid that is most appropriate for the procedure that is planned. It must be emphasized that these recommendations are based on calculations and hypothetical settings, not actual data. Accordingly, they are tentative and should be altered as definitive information becomes available. 相似文献
68.
Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes 总被引:9,自引:1,他引:9
下载免费PDF全文
![点击此处可从《The Journal of experimental medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J Bauer T M Bauer T Kalb T Taga G Lengyel T Hirano T Kishimoto G Acs L Mayer W Gerok 《The Journal of experimental medicine》1989,170(5):1537-1549
IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions. 相似文献
69.
Intraindividual Reproducibility of Heart Rate Variability 总被引:1,自引:0,他引:1
STEFAN H. HOHNLOSER THOMAS KLINGENHEBEN MARKUS ZABEL FRANK SCHRÖDER HANJÖRG JUST 《Pacing and clinical electrophysiology : PACE》1992,15(11):2211-2214
Heart rate variability was determined from three consecutive Holter recordings performed on days 1, 7, and 28 in 17 normal subjects, in 13 patients with angiographically normal coronary arteries, and in 9 patients with remote myocardial infarctions. Group data of several time and frequency domain measures of heart rate variability were highly reproducible (correlation coefficients 0.629–0.894). However, some individuals exhibited considerably larger day-to-day variations in heart rate variability. Single heart rate indices differed by up to 50% between two Holter recordings. Such potential differences must be considered when repeated heart rate variability determinations are used to assess changes in neurocardiac reflex regulation or effects of therapeutic interventions. 相似文献
70.