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   33370篇
  免费   2903篇
  国内免费   1338篇
耳鼻咽喉   398篇
儿科学   650篇
妇产科学   623篇
基础医学   4138篇
口腔科学   573篇
临床医学   3561篇
内科学   5716篇
皮肤病学   756篇
神经病学   2200篇
特种医学   1079篇
外国民族医学   13篇
外科学   4313篇
综合类   4032篇
现状与发展   4篇
一般理论   21篇
预防医学   1982篇
眼科学   1169篇
药学   2685篇
  18篇
中国医学   1095篇
肿瘤学   2585篇
  2023年   406篇
  2022年   687篇
  2021年   1445篇
  2020年   1064篇
  2019年   1037篇
  2018年   1150篇
  2017年   1012篇
  2016年   1036篇
  2015年   1319篇
  2014年   1625篇
  2013年   1586篇
  2012年   2462篇
  2011年   2479篇
  2010年   1419篇
  2009年   1210篇
  2008年   1779篇
  2007年   1795篇
  2006年   1761篇
  2005年   1754篇
  2004年   1306篇
  2003年   1105篇
  2002年   999篇
  2001年   799篇
  2000年   800篇
  1999年   771篇
  1998年   448篇
  1997年   373篇
  1996年   280篇
  1995年   296篇
  1994年   239篇
  1993年   173篇
  1992年   312篇
  1991年   295篇
  1990年   281篇
  1989年   257篇
  1988年   223篇
  1987年   208篇
  1986年   200篇
  1985年   152篇
  1984年   109篇
  1983年   75篇
  1982年   51篇
  1981年   60篇
  1979年   74篇
  1978年   57篇
  1977年   55篇
  1976年   46篇
  1974年   66篇
  1973年   61篇
  1972年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
In view of the ability of ketones to partially replace glucose as an alternative fuel in the brain, the potential protective effects of diet-induced ketosis were examined in male NEDH rats with hypoglycaemia due to a serially transplantable radiation-induced insulinoma. Ketosis was induced by daily oral administration of medium chain triglycerides to normal rats and to insulinoma-bearing rats 1 day after subcutaneous subscapular implantation of tumours fragments. All rats treated with medium chain triglycerides became ketotic within 72 hours, and plasma 3-hydroxybutyrate concentrations remained 5-10 fold elevated at 24 days. Untreated insulinoma-bearing rats became moderately hyperinsuliaemic and hypoglycaemic by 17 days, with the later manifestation of more marked hyperinsulineamia (21.6 +/- 0.8 ng/ml, mean +/- SEM) severe hypoglycaemia (1.5 +/- 0.1 mmol/l) and death by 24-28 (26 +/- 1) days. Induction and maintenance of hyperketonaemia did not affect the development of hyperinsulineamia, hypoglycaemia or the exaggerated fall of plasma glucose produced by an 8 hour fast in these rats. However by day 21, the severity of hypoglycaemia was greater in insulinoma-bearing rats receiving medium chain triglycerides, culminating in accelerated death by 22-25 (23 +/- 1) days and an accompanying 50% decrease in final tumour weight. These results demonstrate that induction of ketosis in the face of marked hyperinsulinaemia did not afford protection against the profound hypoglycaemia produced by a serially transplantable rat insulinoma.  相似文献   
82.
83.
Performance standards for toric soft contact lenses.   总被引:1,自引:0,他引:1  
PURPOSE: To simplify the clinical assessment of toric soft contact lens (TSCL) on-eye behavior by establishing a set of standard clinical evaluation techniques. The likely performance range expected among the TSCL wearing population was determined for a series of lens designs and acceptable performance standards indicated for each variable. METHODS: Four prism-ballast, two peri-ballast and one dynamic stabilization TSCL designs were each worn by groups of 20 subjects in a nondispensing study. After 20 min of lens wear, lenses were assessed, in right eyes only, for subjective comfort (100-point scale), lens mislocation (degrees deviation from vertical) and rotational recovery after deliberate 30 degrees mislocation (degrees/10 blinks). The percentage of lenses orienting within +/-10 degrees of target orientation (zero rotation) and the variability of orientation (standard deviation of mislocation) were also calculated for each lens group. RESULTS: Based on partitioning of the data distributions for each variable, performance was designated as excellent, acceptable or poor. Corresponding performance cut-offs were determined at > or =90, 89 to 80, and <80 for subjective comfort, < or =+/-6 degrees , +/-7 degrees to 10 degrees , and >+/-10 degrees for mislocation, >10 degrees /10 blinks, 10 degrees to 6 degrees /10 blinks, and <6 degrees /10 blinks for rotational recovery. For groups of wearers the appropriate cut-offs were > or =90%, 89 to 70%, and <70% of lenses orienting within +/-10 degrees of target orientation and <+/-6 degrees , +/-6 degrees to 10 degrees , and >+/-10 degrees for variability of orientation. CONCLUSION: Techniques suitable for the evaluation of TSCL clinical performance have been described and guidelines for the assessment of such lenses established. In the process, we have identified potential performance differences that may relate to variations in TSCL design.  相似文献   
84.
本文通过用四氧嘧啶复制小白鼠糖尿病模型,以血清中血糖及胰岛素水平为指标,研究了地黄合剂对高糖动物的降血糖作用。结果表明,注射四氧嘧啶前小白鼠血糖为173.47±5.23mg/100ml注射后血糖升高至419.78±22.70mg/100ml(P<0.01),差异有高度显著性。实验组服用地黄合剂后,血糖值从410.25±2739mg/100ml下降至313.51±29.39mg/100ml(P<0.05)差异有显著性。因而认为地黄合剂对于四氧嘧啶性糖尿病有显著的降血糖作用。  相似文献   
85.
Lymphoid clusters (LC) containing CD20-positive B cells in kidney allografts undergoing acute cellular rejection (ACR) have been identified in small studies as a prognostic factor for glucocorticoid resistance and graft loss. Allograft biopsies obtained during the first episode of ACR in 120 recipients were evaluated for LC, immunostained with CD20 antibody, and correlated with conventional histopathologic criteria, response to treatment and outcome. LC were found in 71 (59%) of the 120 biopsies. All contained CD20 positive B cells that accounted for 5-90% of the LC leukocyte content. The incidence of LC was highest in the patients who had no lymphoid depletion or had been treated with Thymoglobulin preconditioning (79% vs. 75%, respectively) compared to 37% in patients pretreated with Campath (p = 0.0001). Banff 1a/1b ACR were more frequent in the LC-positive than the LC-negative group (96% vs. 80%, respectively; p = 0.0051). With a posttransplant follow-up of 953 +/- 430 days, no significant differences were detected between LC-postitive and LC-negative groups in time to ACR, steroid resistance, serum creatinine and graft loss. CD20+LC did not portend glucocorticoid resistance or worse short to medium term outcomes. CD20+LC may represent a heterogenous collection in which there may be a small still to be fully defined unfavorable subgroup.  相似文献   
86.
目的探讨肾动脉狭窄支架植入术的临床疗效.方法1997年1月~2004年12月,我院行支架介入治疗肾动脉狭窄27例.对27例术前、术后及随访期内血压、肾功能以及生活质量进行评估,并与同期单纯药物治疗肾动脉狭窄27例进行比较.结果介入组27例植入支架40枚,手术成功24例(88.9%,24/27),失败3例(11.1%,3/27),手术并发症5例(18.5%,5/27).术后在血压下降(包括收缩压舒张压)肌酐下降,肾小球滤过率增加方面,介入组获益率明显优于药物组,两组比较差异均有显著性,术后随访6个月~8年6个月,中位数为1年9个月,介入组有19例能比较健康的生活和工作,药物组仅12例能维持生活和工作.结论支架介入治疗较单纯药物治疗肾动脉狭窄疗效显著.  相似文献   
87.
去带盲升结肠可控膀胱术后远期并发症(附105例报告)   总被引:2,自引:0,他引:2  
目的 探讨去带盲升结肠可控膀胱术后远期并发症的发生及防治.方法 回顾性分析1995年10月至2003年1月105例去带盲升结肠可控膀胱术后患者资料.男83例,女22例.年龄32~78岁,平均60岁.随访时间9~82个月,平均40.5个月.结果 发生远期并发症27例(25.7%),其中导尿插管困难4例(3.8%),3例行尿道扩张后治愈,1例再次手术利用末段回肠重建输出道;贮尿囊结石5例(4.8%),4例行贮尿囊切开取石治愈,1例无自觉症状者未行处理;贮尿囊穿孔1例(0.9%),行手术修补后痊愈;贮尿囊过度扩张1例(0.9%),行贮尿囊缩小术;肾积水8例(7.6%),合并输尿管返流1例,合并下段输尿管狭窄4例,其中2例行狭窄段输尿管切除再吻合,1例术前为氮质血症者发展为尿毒症需行规律血透;血氯增高7例(6.7%),1例出现高氯性酸中毒需长期口服碳酸氢钠;单纯表现为症状性泌尿系感染1例(0.9%).27例中另合并症状性泌尿系感染10例,根据尿培养结果予敏感抗生素治愈.结论 去带盲升结肠可控膀胱术后远期并发症多与症状性泌尿系感染相关,积极防治泌尿系感染,规律、充分的贮尿囊冲洗及定时清洁导尿对远期并发症的预防有重要作用.  相似文献   
88.
Pulmonary thromboembolism is the leading direct cause of maternal deaths in the UK. The majority of deaths occur in the puerperium. Caesarean section has been recognised as a risk factor but there is concern that more attention to thromboprophylaxis after vaginal births is needed. The hospital maternity unit in Dumfries has written guidelines on thromboprophylaxis after vaginal births. This audit assessed the compliance with these guidelines within this maternity unit. The case notes relating to spontaneous vaginal births over a 2-month period (n=148) and instrumental vaginal births over a 7-month period (n=29) were reviewed. Information concerning venous thromboembolism risk and any thromboprophylaxis given was extracted. The audit showed that 9% of spontaneous vaginal births and 62% of instrumental vaginal births required specific thromboprophylaxis. However, only 31% of the spontaneous vaginal births and 22% of the instrumental vaginal births in which thromboprophylaxis was indicated did indeed receive the required treatment. Failure to respond to venous thromboembolism risk factors was common. Measures to increase the awareness of maternity staff to these factors are suggested.  相似文献   
89.
This review tries to summarize the efforts over the past 20 years to construct a tissue-engineered trachea. After illustrating the main technical bottlenecks faced nowadays, we discuss what might be the solutions to these bottlenecks. You may find out why the focus in this research field shifts dramatically from the construction of a tubular cartilage tissue to reepithelialization and revascularization of the prosthesis. In the end we propose a novel concept of 'in vivo bioreactor', defined as the design of a perfusion system inside the scaffold, and explain its potential application in the construction of a tissue-engineered trachea.  相似文献   
90.
A double-blind randomised controlled trial of the effect of low dose lofepramine (70 mg once daily) against placebo was carried out on depressed elderly inpatients on general medical wards for the elderly, comparing measures of depression and side-effects between the randomised groups. Patients were identified for the study using the Geriatric Depression Scale (GDS) and the Brief Assessment Schedule Depression Cards (BASDEC). Sixty-three subjects were randomised: 46 patients completed the entire trial of 28 days treatment. BASDEC and GDS were administered on day 8 post-admission, and depressed patients were randomised double-blind to either low dose lofepramine (70 mg daily) (n = 23) or placebo (n = 23). Assessment of changes in depressive states were made using the Montgomery Asberg Depression Rating Scale (MADRS) on days 8, 18 and 36 post-admission. Both groups improved by a similar amount during the trial. Lofepramine tended to be more effective than placebo in those patients who were more depressed (GDS > or = 18). On the other hand, subjects who were less depressed (i.e. GDS < 18) improved more on placebo than lofepramine. Low dose lofepramine may prove useful in moderately or severely depressed patients treated for only 4 weeks. However, low dose lofepramine is not indicated for mild (GDS 15-18) depression.  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