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   3958篇
  免费   251篇
  国内免费   14篇
耳鼻咽喉   39篇
儿科学   107篇
妇产科学   76篇
基础医学   392篇
口腔科学   181篇
临床医学   296篇
内科学   1019篇
皮肤病学   46篇
神经病学   389篇
特种医学   91篇
外科学   721篇
综合类   26篇
一般理论   2篇
预防医学   270篇
眼科学   90篇
药学   226篇
中国医学   5篇
肿瘤学   247篇
  2023年   28篇
  2022年   64篇
  2021年   132篇
  2020年   86篇
  2019年   121篇
  2018年   129篇
  2017年   95篇
  2016年   106篇
  2015年   106篇
  2014年   149篇
  2013年   177篇
  2012年   279篇
  2011年   273篇
  2010年   178篇
  2009年   160篇
  2008年   266篇
  2007年   243篇
  2006年   250篇
  2005年   243篇
  2004年   208篇
  2003年   172篇
  2002年   174篇
  2001年   39篇
  2000年   25篇
  1999年   51篇
  1998年   37篇
  1997年   48篇
  1996年   33篇
  1995年   28篇
  1994年   16篇
  1993年   20篇
  1992年   21篇
  1991年   20篇
  1990年   15篇
  1989年   13篇
  1988年   13篇
  1987年   9篇
  1986年   13篇
  1985年   18篇
  1984年   13篇
  1983年   13篇
  1982年   20篇
  1981年   18篇
  1980年   11篇
  1979年   12篇
  1978年   9篇
  1977年   7篇
  1975年   8篇
  1974年   9篇
  1973年   10篇
排序方式: 共有4223条查询结果,搜索用时 0 毫秒
41.
F Raul  M Ledig  F Gosse  M Galluser  M Doffoel 《Alcohol》1987,4(5):405-408
Intestinal hydrolase activities were studied during postnatal development in the offspring of rats exposed to 20% ethanol during gestation; alcohol was withdrawn at birth. Controls received water during gestation. Sucrase, lactase, glucoamylase and aminopeptidase activities were determined 2 and 4 weeks after birth in the proximal jejunum. Offspring prenatally exposed to ethanol showed a deficit in body weight and lower aminopeptidase activity during the suckling period (2 weeks). These effects were reversible by 4 weeks when alcohol was withdrawn at birth. The prenatal exposure to ethanol did not change the pattern of sucrase maturation in the intestine of offsprings. The activities of lactase and glucoamylase were not modified following prenatal exposure to ethanol. In conclusion, exposure to ethanol during gestation caused decreased abilities for the intestine of the offspring to digest protein.  相似文献   
42.
The rate of cell proliferation is under the control of humoral factors, luminal nutrition and intestinal growth factors which maintain mucosal homeostasis by highly complex mechanisms. Among endocrine effectors, growth hormone (GH) has been noted to exert a trophic effect on the small intestine and stimulates the bowel morphologic and proliferative adaptation after resection. These effects may be mediated by IGF-I. The nutrients (lipids > proteins > polysacharids) and polyamines are the main effectors in the control of mucosal proliferation.A number of intestinal growth factors whose expression may be regulated by luminal or hormonal effectors may play an important role in the control of intestinal growth. Milk EGF (Epidermal Growth Factor) has a trophic effect in the suckling rat. In the adult only systemic EGF stimulates intestinal growth after resection, infection or treatment with methotrexate. TGFα (Transforming Growth Factor alpha), a ligand that binds to the same receptor as EGF, exerts the same trophic responses. TGFα may be the more physiologically ligand of the EGF receptor in the adult. In addition TGFα may be implicated in the progression of colonic tumours. IGF-I and IGF-II (Insulin-like Growth Factor), polypeptides structurally homologous to proinsulin, have mitogenic, morphogenic and metabolic properties. The members of the FGF (Fibroblast Growth Factor) family have only a moderate effect on the growth of intestinal epithelial cells and a main role in the repair of damaged tissue. TGFβ (Transforming Growth Factor) is an inhibitor of intestinal epithelial cell growth in the G1 phase of the cell cycle. TGFβ may be the physiological regulator of apoptosis in the colonic epithelium and the loss of this function may favour tumour progression. TGFβ also induces the production of constituents of the extracellular matrix and promotes the healing of wounded tissue.  相似文献   
43.
镍钛合金加压吻合技术应用于腹腔镜胃肠吻合的临床研究   总被引:1,自引:1,他引:0  
目的评价一种新型的腹腔镜镍钛记忆合金加压吻合夹(LapCAC)进行胃肠吻合的安全性及有效性。方法2007年3月,对l例行全胃切除术和2例行远端胃大部切除术的胃癌患者,使用LapCAC进行Roux-en-Y空肠-空肠侧侧吻合和胃肠吻合;术后观察有无发生与胃肠吻合相关的并发症,并观察肠道恢复排气时间及LapCAC的排出时间。结果患者术后均未出现与吻合相关的吻合口瘘、吻合口狭窄及肠梗阻等并发症,术后肠道排气、排便均无异常。LapCAC均于术后12~18d排出体外。结论应用LapCAC进行腹腔镜胃肠吻合安全、可靠。  相似文献   
44.
Context  Little is known about the incidence of secondary neoplasms after 15 to 20 years in children and adolescents who were treated for acute lymphoblastic leukemia. Objectives  To investigate the cumulative incidence of secondary neoplasms in pediatric patients treated for acute lymphoblastic leukemia over 30 years and to characterize late-occurring tumors. Design, Setting, and Patients  Retrospective study of 2169 patients with acute lymphoblastic leukemia treated between 1962 and 1998 at St Jude Children's Research Hospital, Memphis, Tenn, who achieved complete remission and had a median follow-up time of 18.7 years (range, 2.4-41.3 years). Main Outcome Measures  Cumulative incidences of secondary neoplasms in first remission and standard incidence ratios of observed rates compared with rates of cancer development in the general US population. Results  Secondary neoplasms developed as the first event in 123 patients and comprised 46 myeloid malignancies, 3 lymphomas, 14 basal cell carcinomas, 16 other carcinomas, 6 sarcomas, 16 meningiomas, and 22 other brain tumors. The cumulative incidence of secondary neoplasm was 4.17% (SE, 0.46%) at 15 years and increased substantially after 20 years, reaching 10.85% (SE, 1.27%) at 30 years. When meningiomas and basal cell carcinomas were excluded, the overall cumulative incidence was 3.99% (SE, 0.44%) at 15 years and 6.27% (SE, 0.83%) at 30 years, representing a 13.5-fold increase in overall risk compared with the general population. The cumulative incidence of each tumor type at 30 years was 2.19% (SE, 0.32%) for myeloid malignancy, 0.17% (SE, 0.10%) for lymphoma, 3.00% (SE, 0.59%) for brain tumor, 4.91% (SE, 1.04%) for carcinoma, and 0.57% (SE, 0.37%) for sarcoma. Conclusions  The cumulative incidence of secondary neoplasms increases steadily over 30 years after treatment of acute lymphoblastic leukemia. Although the majority of the late-occurring secondary neoplasms are low-grade tumors, the increase in incidence of more aggressive malignant neoplasms is significantly higher than expected in the general population. These results suggest that lifelong follow-up of acute lymphoblastic leukemia survivors is needed to ascertain the full impact of treatment and other leukemia-related factors on secondary neoplasm development.   相似文献   
45.
This paper examines the extent to which food intake in malnourished populations is affected by increasing the availability of the dietary staples. Free amounts of corn and beans were supplied to 47 families in a rural Guatemalan community during eight weeks. Relative to a six‐week baseline period, adults increased their intakes by about 400 kcal (1.68 MJ) and 15 gof protein per day. The average changes for pre‐school children were 198 kcl (0.83 MJ) and 5.8 g of protein per day. The findings suggest that it is possible for adults to satisfy their energy and protein needs by consuming more corn and beans. In children, bulk may be a limiting factor and it may be necessary to resort to additional measures, such as increasing the energy density of the diet, to satisfy needs.  相似文献   
46.
47.
Abstract

The aim of this study was to investigate the effects of malnutrition, induced by a regional basic diet (RBD), on motor development. RBD is a 7.87%-protein diet based on aliments typical of Northeastern Brazil, elaborated after nutritional investigation by Teodosio et al. (1979). Female rats were treated with RBD during lactation. The reflex ontogenesis and the development of locomotor activity in their offspring were assessed. Malnourished (MN) rats showed a delay in reflex maturation and in locomotor activity evolution. The decreased locomotor activity may be related to the reduced movement experiences induced by the delay in the reflex maturation. Occurring during the critical period of brain development, this fact could jeopardize all the steps in future locomotion evolution. The present results confirm deleterious effects of RDB-induced malnutrition on the somatic development and maturation of the nervous system (NS).  相似文献   
48.
Chloroquine (CQ) is officially used for the primary treatment of Plasmodium falciparum malaria in Honduras. In this study, the therapeutic efficacy of CQ for the treatment of uncomplicated P. falciparum malaria in the municipality of Puerto Lempira, Gracias a Dios, Honduras was evaluated using the Pan American Health Organization—World Health Organization protocol with a follow-up of 28 days. Sixty-eight patients from 6 months to 60 years of age microscopically diagnosed with uncomplicated P. falciparum malaria were included in the final analysis. All patients who were treated with CQ (25 mg/kg over 3 days) cleared parasitemia by day 3 and acquired no new P. falciparum infection within 28 days of follow-up. All the parasite samples sequenced for CQ resistance mutations (pfcrt) showed only the CQ-sensitive genotype (CVMNK). This finding shows that CQ remains highly efficacious for the treatment of uncomplicated P. falciparum malaria in Gracias a Dios, Honduras.  相似文献   
49.
Infection of mosquitoes by humans is not always successful in the setting of patent gametocytemia. This study tested the hypothesis that pro- or anti-inflammatory cytokines are associated with transmission of Plasmodium vivax to Anopheles darlingi mosquitoes in experimental infection. Blood from adults with acute, non-severe P. vivax malaria was fed to laboratory-reared F1 An. darlingi mosquitoes. A panel of cytokines at the time of mosquito infection was assessed in patient sera and levels compared among subjects who did and did not infect mosquitoes. Overall, blood from 43 of 99 (43%) subjects led to mosquito infection as shown by oocyst counts. Levels of IL-10, IL-6, TNF-α, and IFN-γ were significantly elevated in vivax infection and normalized 3 weeks later. The anti-inflammatory cytokine IL-10 was significantly higher in nontransmitters compared with top transmitters but was not in TNF-α and IFN-γ. The IL-10 elevation during acute malaria was associated with P. vivax transmission blocking.  相似文献   
50.
INTRODUCTION: The purpose of this study was to investigate the effect of ablation of right atrial flutter upon sinus node function in humans. METHODS AND RESULTS: This study enrolled 35 patients. Twenty-four patients (16 men and 8 women; age 68 +/- 11 years) were referred for ablation of persistent atrial flutter (duration 8 +/- 11 months). After ablation, there was abnormal sinus node function defined as a corrected sinus node recovery time (CSNRT) > or = 550 msec. The control group consisted of 11 patients who were undergoing pacemaker implantation for sinus node disease but did not have a history of atrial dysrhythmias or ablation. Within 24 hours of ablation or pacemaker implantation, baseline maximal CSNRT was measured through a permanent pacemaker by AAI pacing at six cycle lengths: 600, 550, 500, 450, 400, and 350 msec. CSNRT then was measured in the same manner at 48 hours, 14 days, and 3 months after ablation/pacemaker implantation. P wave amplitude and duration, and percent atrial sensing also were assessed at the same intervals. For patients undergoing atrial flutter ablation, there was progressive temporal recovery of CSNRT (1,204 +/- 671 msec at baseline vs 834 +/- 380 msec at 3 months; P < 0.001) and a significant increase in the percent atrial sensing and P wave amplitude at 3 months compared with baseline (P < 0.001). In control subjects, there was no change in the CSNRT, percent atrial pacing, or P wave amplitude. CONCLUSION: After ablation of persistent atrial flutter, there is temporal recovery of CSNRT and increase in spontaneous atrial activity. These findings suggest that atrial flutter induces reversible changes in sinus node function.  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