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   9924篇
  免费   912篇
  国内免费   409篇
耳鼻咽喉   30篇
儿科学   152篇
妇产科学   47篇
基础医学   984篇
口腔科学   117篇
临床医学   1679篇
内科学   1177篇
皮肤病学   73篇
神经病学   445篇
特种医学   352篇
外国民族医学   2篇
外科学   1639篇
综合类   1771篇
现状与发展   1篇
预防医学   822篇
眼科学   155篇
药学   837篇
  9篇
中国医学   740篇
肿瘤学   213篇
  2024年   36篇
  2023年   207篇
  2022年   348篇
  2021年   573篇
  2020年   505篇
  2019年   454篇
  2018年   439篇
  2017年   470篇
  2016年   370篇
  2015年   403篇
  2014年   678篇
  2013年   675篇
  2012年   482篇
  2011年   634篇
  2010年   452篇
  2009年   468篇
  2008年   452篇
  2007年   440篇
  2006年   420篇
  2005年   366篇
  2004年   330篇
  2003年   283篇
  2002年   194篇
  2001年   184篇
  2000年   157篇
  1999年   119篇
  1998年   108篇
  1997年   141篇
  1996年   84篇
  1995年   105篇
  1994年   78篇
  1993年   79篇
  1992年   51篇
  1991年   45篇
  1990年   50篇
  1989年   42篇
  1988年   35篇
  1987年   36篇
  1986年   36篇
  1985年   33篇
  1984年   40篇
  1983年   22篇
  1982年   26篇
  1981年   31篇
  1980年   15篇
  1979年   7篇
  1978年   15篇
  1977年   5篇
  1976年   4篇
  1975年   7篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
风湿性心脏病二尖瓣置换术中细胞因子水平的变化   总被引:1,自引:0,他引:1  
目的测定风湿性心脏病二尖瓣置换术中细胞因子水平,了解它们的变化规律。方法 11例体外循环(CPB)下二尖瓣置换术患者,分别于术前,主动脉阻断前,主动脉阻断后5min,主动脉开放后10min、1h、2h、4h、24h测定白介素6(IL-6)、白介素8(IL-8)、白介素10(IL-10)以及肿瘤坏死因子(TNF)。结果IL-6、IL-8、IL-10水平在CPB开始后逐渐升高,在主动脉开放后2h左右达到高峰(P<0.01)。之后逐渐下降,到主动脉开放后24h已显著下降。TNF水平在CPB开始后逐渐升高,在主动脉开放后24h仍维持在很高的水平(P<0.01)。结论CPB下二尖瓣置换术中既有促炎因子水平的升高,又有抗炎因子的激活。  相似文献   
72.
Absence of predictable phenotypic expression in proximal 15q duplications   总被引:5,自引:0,他引:5  
We describe ten individuals with an insertional duplication 15q12----q13. Phenotypic analysis of these individuals and 15 previously reported cases of proximal 15q duplications fails to show any consistent clinical manifestations. It appears that a duplication of this region is phenotypically silent.  相似文献   
73.
Abstract: We have used heparin-bonded partial cardio-pulmonary bypass to support distal aortic circulation during aortic cross-clamping. However, there were no cardiotomy reservoirs with fully reliable thromboresistance. To resolve this problem, a short-acting anticoagulant (nafamostat mesilate) was added into a cardiotomy reservoir. The present study was designed to evaluate the efficacy of our distal perfusion system. From May 1995 through the end of May 1996, 27 patients underwent descending thoracic and thoracoabdominal aortic aneurysm repairs with this adjunct, 4 being excluded from the experiment. Twenty patients who had undergone conventional partial cardiopulmonary bypass were defined as the control group. There were no significant differences between the 2 groups in the morbidity, mortality, gas transfer, or transfusion requirements despite the fact that more complicated surgical procedures (shown by a two-fold increase in the prevalence of reoperation) were required in the group that had received the current distal perfusion adjunct. the heparin-bonded group. In conclusion, our perfusion system is very effective for descending thoracic and thoracoabdominal aortic aneurysm repairs.  相似文献   
74.
Previous mouse liver studies with diazepam (DZ),N-desmethyldiazepam (NZ), and temazepam (TZ) confirmed that under first-order conditions, DZ formed NZ and TZ in parallel. Oxazepam (OZ) was generatedvia NZ and not TZ despite that preformed NZ and TZ were both capable of forming OZ. In the present studies, the concentration-dependent sequential metabolism of DZ was studied in perfused mouse livers and microsomes, with the aim of distinguishing the relative importance of NZ and TZ as precusors of OZ. In microsomal studies, theK ms andV maxs, corrected for binding to microsomal proteins, were 34 μM and 3.6 nmole/min per mg and 239 μM and 18 nmole/min per mg, respectively, forN-demthylation andC 3-hydroxylation of DZ. TheK ms andV maxs forN-demethylation andC 3-hydroxylation of TZ and NZ, respectively, to form OZ, were 58 μM and 2.5 nmole/min per mg and 311 μM and 2 nmole/min per mg, respectively. The constants suggest that at low DZ concentrations, NZ formation predominates and is a major source of OZ, whereas at higher DZ concentrations, TZ is the important source of OZ. In livers perfused with DZ at input concentrations of 13 to 35 μM, the extraction ratio of DZ (E{DZ}) decreased from 0.83 to 0.60. NZ was the major metabolite formed although its appearance was less than proportionate with increasing DZ input concentration. By contrast, the formation of TZ increased disporportionately with increasing DZ concentration, whereas that for OZ decreased and paralleled the behavior of NZ. Computer simulations based on a tubular flow model and thein vitro enzymatic parameters provided a poorin vitro-organ correlation. TheE{DZ}, appearance rates of the metabolites, and the extraction ratio of formed NZ (E{NZ, DZ}) were poorly predicted; TZ was incorrectly identified as the major precursor of OZ. Simulations with optimized parameters imporved the correlations and identified NZ as the major contributor of OZ. Saturation of DZN-demethylation at higher DZ concentrations increased the role of TZ in the formation of OZ. The poor aqueous solubility (limiting the concentration range of substrates usedin vitro), avid tissue binding and the coupling of enzymatic reactions in liver, favoring sequential metabolism, are possible explanations for the poorin vitro-organ correlation. This work emphasizes the complexity of the hepatic intracellular milieu for drug metabolism and the need for additional modeling efforts to adequately describe metabolite kinetics. This work was supported by the Medical Research Council of Canada (MA-9104).  相似文献   
75.
停跳或不停跳心脏手术对血清 S-100B蛋白表达的影响   总被引:2,自引:1,他引:1  
【目的】研究心脏手术围术期血清S-100B蛋白表达及其与停跳或不停跳心肺转流方式和时间的关系。【方法】体外循环心脏手术患者23例,测转流前、转流10min、转流末、转流后24h的血清S-100B蛋白表达水平。【结果】①血清S-100B蛋白质量浓度在体外循环前后动态变化:转流前(M)为0.27μg/L,转流10min后升至0.57μg/L(P<0.01),转流末达峰值1.80μg/L(P<0.01),转流后24h降为0.22μg/L(P>0.05)。转流末的血清S-100B蛋白质量浓度与转流时间呈正相关(r=0.488,P<0.05)。②停跳组(n=6)转流前、转流10min、转流末、转流后24h平均血清S-100B蛋白质量浓度分别为(0.17±0.09)μg/L、(0.48±0.13)μg/L、(1.65±0.52)μg/L和(0.19±0.04)μg/L,不停跳组(n=6)分别为(0.26±0.14)μg/L、(0.71±0.41)μg/L、(1.59±0.84)μg/L和(0.23±0.11)μg/L,两组差别无统计学意义(P>0.05)。【结论】体外循环可导致血清S-100B蛋白表达增高,其表达水平与心肺转流时间呈正相关,但与停跳或不停跳转流方式无关。  相似文献   
76.
Background: Pediatric cardiopulmonary arrest (CPA) outside of the hospital has a very high mortality rate. Objectives: To evaluate the etiology and initial compromise of pediatric CPA cases in hopes of developing strategies to improve out‐of‐hospital resuscitation. Methods: The Ontario Prehospital Advanced Life Support (OPALS) study was a large multicenter initiative to evaluate the impact of emergency medical services (EMS) programs on 17 communities with 40,000 critically ill and injured patients who were older than 11 years. As part of this study, the authors conducted a retrospective observational cohort study that included all children younger than 18 years of age with out‐of‐hospital CPA, during an 11‐year period from 1991–2002. CPA was defined as patient being pulseless, apneic, and requiring chest compressions. Data were collected from ambulance call reports and centralized dispatch data and were reviewed by two independent investigators. Results: There were 503 children with CPA in the sample. Mean age was 5.6 years (range, 0–17 yr); 58.4% of patients were male, and 37.8% were younger than 1 year of age. Cardiopulmonary resuscitation (CPR) first was started by a bystander in 32.4% of cases, whereas 66.0% were unwitnessed arrests. Initial rhythms were asystole 77.2% of the time, pulseless electrical activity 16.4% of the time, and ventricular fibrillation or ventricular tachycardia 4% of the time. Annual incidence was 9.1/100,000 children. CPA was witnessed in 34.0% of cases; 80.7% of these were bystander‐witnessed, and 18.1% were EMS‐witnessed. Primary pathogenic cause of arrest was medical in 61.2% of cases, trauma in 37.2% of cases, and indeterminate in 1.6% of cases. Initial underlying physiologic compromise of witnessed arrests was judged to be respiratory in 39.8% of cases, sudden collapse (presumed electrical) in 16.4% of cases, progressive shock in 1.2% of cases, and indeterminate in 42.6% of cases. Presumed etiology was trauma, 37.6%; sudden infant death syndrome (SIDS), 20.3%; and respiratory disease, 11.6%, most commonly. Survival to hospital discharge was 2.0%. Conclusions: This is one of the largest population‐based, prospective cohorts of pediatric CPA reported to date, and it reveals that most pediatric arrests are unwitnessed and receive no bystander CPR. Those that are witnessed most often are caused by respiratory arrests or trauma. Trauma, SIDS, and respiratory disease are the most common etiologies overall. These data are vital to planning large resuscitation trials looking at specific interventions (i.e., increasing bystander CPR) and highlight the need for better strategies for prevention and early recognition.  相似文献   
77.
78.
Abstract Immunological data have been suggested to be a potential tool in the diagnosis, classification and monitoring of periodontal diseases. However, the role of circulating antibodies in periodontal patients is poorly understood. Patients suffering from localized juvenile periodontitis (LJP) are often reported to show high titers of serum IgG antibodies against Aetinobaeillus actinomycetemcomitans (A. actinomycetemcotnitans), but several affected patients do not. Most studies use well-known reference strains of the bacterium for testing against the patients' sera. The aim of the present investigation was to study the relationship between serum IgG antibody levels to autologous A. actinomycetemcomitans strains and clinical attachment loss (CAL). In addition, we wanted to assess the patients’serum titers against 4 well-known reference strains of the bacterium as well as their general potential immunoglobulin response. Intravenous blood samples were taken from 23 LJP patients and 10 healthy individuals, and autologous A. actinomycetemcomitans strains were cultured from 18 of the L.JP patients. CAL was measured at 4 different sites around ail present teeth and assessed as a % of teeth with at least 1 site moderately ≥2<5 mm) or severely (≥5 mm) involved. An enzyme-linked immunosorbent assay (ELISA) was performed to evaluate the serum titers of IgG antibodies to A. actinomycetemcomitans antigens. No significant correlation was found between serum IgG antibody titers to autologous strains and CAL. However, there was a trend that low responders had more moderately affected teeth than had high responders and patients with undetectable A. actinomycetemcomitans levels, which is in agreement with a hypothetically protective role of the antibodies. The total counts of immunoglobulin assessed in all participants showed that the predominant class was IgG and the reference group displayed significantly less (p<0.05) IgG and IgG1 counts than the LJP patients. Both the reaction pattern against reference and autologous strains varied widely. We conclude that the specific antibody response against A. actinomycetemcomitans shows a weak correlation to clinical attachment levels in LJP patients.  相似文献   
79.
徐碧霞  姚卫光 《中国全科医学》2023,26(16):1965-1971
背景 我国分级诊疗制度建设已取得一定成效,但基层医疗卫生机构发展速度依旧相对缓慢。目的分析2013—2020年广东省基层医疗卫生机构诊疗人次的变化情况及影响因素,为政府深化分级诊疗制度建设提供参考依据。方法 于2021年12月,从2013—2015年《广东省卫生统计年鉴》、2016—2017年《广东省卫生和计划生育统计年鉴》、2018—2020年《广东省卫生健康统计年鉴》提取基层医疗卫生机构诊疗人次数据,作为参考序列;从《广东统计年鉴2021》提取人口数据及居民人均可支配收入,从2015—2017年《中国卫生和计划生育统计年鉴》和2018—2021年《中国卫生健康统计年鉴》提取基层医疗卫生机构财政补助收入和医疗保险参保人数,作为比较序列。采用灰色关联分析法评价各影响因素与基层医疗卫生机构诊疗人次的关联强度。结果 2013—2019年,广东省医院诊疗人次从33 459.2万人次增长至40 131.7万人次,年均增长3.08%,同期全省基层医疗卫生机构诊疗人次年均增长2.10%,2019年全省基层医疗卫生机构诊疗人次已达43 731.7万人次。2020年受新型冠状病毒感染疫情的影响,医院和...  相似文献   
80.
目的 探讨阻塞性睡眠呼吸暂停(OSA)与甘油三酯葡萄糖(TyG)指数的相关性。方法 选取2021年1月—2022年12月中南大学湘雅二医院行睡眠呼吸监测的270例OSA患者。根据甘油三酯和空腹血糖计算TyG指数,根据TyG指数的三分位数将患者分为Q1组、Q2组、Q3组,根据睡眠呼吸暂停低通气指数(AHI)将患者分为轻度组、中度组、重度组。采用多元线性分析评估TyG指数与AHI之间的关系,有序Logistic回归分析TyG指数与OSA严重程度之间的关系。结果 TyG指数越高的患者AHI、体质量指数(BMI)、总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白胆固醇(LDL-C)、空腹血糖越高,而血清高密度脂蛋白胆固醇(HDL-C)水平则越低(P <0.05)。TyG指数越高的患者肥胖和糖尿病、冠心病比例越高,男性比例越高,年龄更低(P <0.05)。随着患者AHI的增加,TyG指数、BMI增加,TG、空腹血糖上升,最低血氧饱和度下降(P <0.05),OSA越严重的患者肥胖、高血压和冠心病比例越高(P <0.05)。Pearson相关性分析结果显示,TyG指数与AHI水平呈正相关(r =0.282,P <0.05)。多元线性回归分析结果显示,AHI(b =0.002)、BMI(b =0.017)、TG(b =0.361)、空腹血糖(b =0.109)和性别(b =0.083)是TyG的影响因素(P <0.05)。有序Logistic模型结果显示:轻度OSA[O^R=0.396(95% CI:0.207,0.757)]和中度OSA[O^R=0.281(95% CI:0.163,0.484)]患者的TyG等级较重度OSA低,说明OSA严重程度增加是TyG指数升高的影响因素。非肥胖患者[O^R=0.424(95% CI:0.253,0.710)]、不吸烟患者[O^R=0.506(95% CI:0.283,0.904)]、非糖尿病患者[O^R=0.268(95% CI:0.156,0.460)]、非冠心病患者[O^R=0.452(95% CI:0.253,0.807)]、女性[O^R=0.409(95% CI:0.221,0.760)]的TyG等级较低,故吸烟、肥胖、糖尿病、冠心病、男性是TyG指数升高的影响因素(P <0.05)。结论 TyG指数与OSA严重程度相关,可以考虑将TyG指数用于OSA患者胰岛素抵抗的观察,从而进行干预,使患者获益。  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