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   54981篇
  免费   3971篇
  国内免费   2206篇
耳鼻咽喉   217篇
儿科学   1245篇
妇产科学   648篇
基础医学   7567篇
口腔科学   576篇
临床医学   4173篇
内科学   14786篇
皮肤病学   738篇
神经病学   3539篇
特种医学   993篇
外国民族医学   3篇
外科学   4620篇
综合类   6023篇
现状与发展   5篇
预防医学   3757篇
眼科学   936篇
药学   7208篇
  7篇
中国医学   1753篇
肿瘤学   2364篇
  2023年   561篇
  2022年   1127篇
  2021年   1477篇
  2020年   1453篇
  2019年   2099篇
  2018年   2084篇
  2017年   1853篇
  2016年   1875篇
  2015年   2022篇
  2014年   3361篇
  2013年   3799篇
  2012年   2981篇
  2011年   3290篇
  2010年   2492篇
  2009年   2479篇
  2008年   2375篇
  2007年   2614篇
  2006年   2352篇
  2005年   2065篇
  2004年   1783篇
  2003年   1611篇
  2002年   1351篇
  2001年   1262篇
  2000年   1036篇
  1999年   976篇
  1998年   842篇
  1997年   866篇
  1996年   655篇
  1995年   674篇
  1994年   575篇
  1993年   436篇
  1992年   402篇
  1991年   335篇
  1990年   259篇
  1989年   230篇
  1988年   212篇
  1987年   183篇
  1985年   512篇
  1984年   639篇
  1983年   490篇
  1982年   464篇
  1981年   458篇
  1980年   396篇
  1979年   363篇
  1978年   296篇
  1977年   233篇
  1976年   267篇
  1975年   262篇
  1974年   204篇
  1973年   189篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Hepatitis C virus (HCV) infection is a major health care issue in liver and kidney transplantation. Besides negatively affecting both patient and graft survival, HCV is associated with a heightened risk for new onset diabetes mellitus (NODM). The mechanisms underlying the diabetogenicity of HCV are complex but are likely to involve insulin resistance caused by inhibitory actions of the virus on insulin regulatory pathways in the liver. The resultant glucose dysregulation is an important determinant of increased morbidity and mortality in liver and kidney recipients. This review highlights the concerns for outcomes in HCV-positive liver and kidney transplant patients with particular focus on the interrelationship between hepatitis C and diabetes. Data about the potential role of calcineurin inhibitors, corticosteroids and mycophenolate mofetil in HCV infection and HCV-associated NODM will also be discussed.  相似文献   
22.
Background and Aim: This study investigated the clinical features of hepatocellular carcinoma in patients with sustained virological response to interferon for hepatitis C viral (HCV) infection. Methods: A total of 7715 patients with HCV infection were treated with interferon and followed up for more than 1 year after withdrawal of interferon in 64 Japanese hospitals and clinics between July 1988 and August 2001. Sustained virological response was obtained in 2515 (32.6%) patients. Of these 2515 patients, clinical data were collected for 38 patients in whom hepatocellular carcinoma developed. Sustained virological response was defined as HCV RNA negativity more than 6 months after the termination of interferon. Results: All patients were HCV RNA negative at the time of diagnosis of hepatocellular carcinoma. The median period until the detection of hepatocellular carcinoma was 4.7 years (range 1.4–9.0 years). There were significant improvements in hepatic function including serum albumin, aspartate aminotransferase, alanine aminotransferase, indocyanine green test, platelet count and histological activity grade in comparison with those before interferon therapy and at the onset of hepatocellular carcinoma. The maximum tumor size in patients without medical follow‐up for 1 year or more (median: 60 mm) was significantly larger than in patients who were periodically followed up for 6 months or less (median: 25 mm) (P = 0.002). Conclusions: The present findings emphasize the importance of regular medical follow up of patients with HCV infection, as even patients showing a sustained virological response to interferon and in whom hepatic function has improved have the potential to develop hepatocellular carcinoma.  相似文献   
23.
本研究选择10μg/ml、20μg/ml、40μg/ml浓度的溴氰菊酯处理白纹伊蚊C6/36细胞,以MMC作为阳性对照物,观察溴氰菊酯处理24h后对C6/36细胞染色体畸变率和姐妹染色单体互换(SCE)频率的影响。结果显示,三个浓度的溴氰菊酯对C6/36细胞染色体畸变率均没有显著影响(P<0.05);溴氰菊酯浓度在40μg/ml时可诱导C6/36细胞SCE频率轻度增高(P>0.05),而溴氰菊酯浓度在10μg/ml、20μg/ml时,对C6/36细胞SCE频率没有诱导作用。表明溴氰菊酯对C6/36细胞的遗传学效应较弱  相似文献   
24.
25.
Abstract A high frequency of serum complement component C4A deficiency may explain the higher prevalence and greater severity of systemic lupus erythematosus reported in Australian Aborigines. Inherited deficiencies of serum complement components C4A, C4B, and C2 were examined in two Australian Aboriginal populations from Darwin and Alice Springs and compared with the prevalence of complement deficiencies in white Australian blood donors. The frequency of C4A deficiency alleles was 29% in Darwin Aborigines compared with 12% in Alice Springs and 17% in Canberra blood donors. Partial C4B deficiency was also higher in Darwin Aborigines than in the other populations. Inherited deficiency of serum complement component C2 was not observed.  相似文献   
26.
目的探索以虚拟现实技术为基础的枢椎椎弓根螺钉置人方法。方法选取8具成人颅一颈椎标本,采用改良四柱式定位框架固定于枕颈,使颅-颈-肩形成统一刚体,保持空间位置恒定,CT薄层扫描获取枢椎三维定位信息,采用Aero—Tech立体定向手术规划系统三维建模,设计安全、可视化、个体化的虚拟置钉路径,反复虚拟演示验证钉道安全后,导向弓把持下置人导向钢针,复查CT评价置钉的准确性。结果16个枢椎椎弓根置钉过程中,方向出现偏差(横突孔突破)1个,失败率为6.25%。结论目标椎弓根的容积三维重建、置钉路径可视化设计和虚拟演示,使操作过程简单、直观而精确,不需要线形和角性参数的测量;加上导向抓持装置提供的稳定性,使该技术具有很好的临床应用前景。  相似文献   
27.
Abstract: Irradiation of human keratinocytes with UVB (280–320 nm) in vitro and in vivo activates the metabolism of 7‐dehydrocholesterol to hormonally active calcitriol. The production of calcitriol in the skin strongly depends on the photosynthesis of vitamin D3 which is biologically inactive in the first instance. Vitamin D3 serves as the starting substrate for two subsequent enzymatic hydroxylation steps in epidermal keratinocytes. Both the amount of vitamin D3 and the activity of anabolic and catabolic vitamin D hydroxylases determine the cutaneous level of calcitriol. The hormonally active metabolite of vitamin D3 regulates a huge number of genes in keratinocytes, and thus acts in an autocrine and/or paracrine manner. This local pathway of vitamin D3 is unique, but its relevance for healthy and diseased skin is widely unknown, yet. Experimental findings implicate several questions: ( 1 ) Is UVB‐induced formation of calcitriol involved in regulation of growth and differentaition of epidermal cells as well as immunological and skin protective processes? ( 2 ) What endogenous and exogenous factors including drugs affect the cutaneous vitamin D3 pathway? From a therapeutical point of view, it has been known for a long time that topical application of calcitriol and its analogs can improve hyperproliferative skin diseases like psoriasis. In spite of many encouraging studies in recent years, the fields of the routinely therapeutical application of calcitriol or vitamin D analogs in dermatology (e.g. treatment of immunological, inflammatory, malignancies and infectious skin diseases) have not been intensified. Why is that?  相似文献   
28.
29.
目的:观察早期大剂量应用抗坏血酸(维生素C)对重症急性胰腺炎(SAP)大鼠的核因子-!B(NF-!B)的影响,研究其作用机制。方法:将72只SAP模型SD大鼠随机分成3组,每组各24只。A组:由大鼠股静脉滴注生理盐水5 ml/kg。B组:大鼠股静脉滴注Vit C 15 mg/kg加生理盐水至5 ml/kg。C组:由大鼠股静脉滴注Vit C 150 mg/kg加生理盐水至5 ml/kg。另取8只SD大鼠作为正常对照组。各组分别于8 h和24 h处死8只大鼠,采血测淀粉酶、脂肪酶、维生素C(PV-C)、超氧化物歧化酶(SOD)、TNF-αI、L-6。大鼠处死时分别取胰头组织3份,一份组织HE染色,行光镜检查,按Kusske的方法,对水肿、炎症、出血和坏死分别评分;一份制成超薄切片,行电镜检查;另一份SP法进行免疫组化染色,检测NF-!B的表达。每组另外8只大鼠观察3 d内存活情况,计算3 d成活率。结果:各组大鼠3 d内的生存率为正常对照组100%(8/8),A组0%(0/8),B组12.5%(1/8),C组50%(4/8),C组的3 d生存率显著高于其他两组(P<0.05)。各组的4项病理学评分均高于正常对照组(P<0.01),C组的4项病理学评分均低于A、B组(P<0.05)。透射电镜检查示C组中分泌颗粒较少,其包膜完整、内质网轻度肿胀、线粒体清晰,未见大片坏死。SAP大鼠体内淀粉酶、脂肪酶、细胞因子TNF-α和IL-6的水平明显增高,血清SOD和P-VC降低,胰腺组织中NF-!B活化阳性胰腺细胞数明显增多。C组的血清淀粉酶和脂肪酶低于A、B组(P<0.05),SOD和P-VC水平高于A、B组(P<0.05),血清TNF-αI、L-6水平低于A、B组(P<0.05),胰腺组织NF-!B活化水平低于A、B组(P<0.05)。结论:早期大剂量应用Vit C有助于及时提高SAP大鼠的P-VC、E-SOD水平,降低体内淀粉酶、脂肪酶、TNF-αI、L-6水平,其作用机制可能与大剂量Vit C抑制SAP大鼠体内NF-!B活化、在整体水平上抑制细胞因子基因表达、有助于机体免受自由基和过量细胞因子的损伤及减轻胰腺组织的病理性改变等因素有关。  相似文献   
30.
云南省600例0~5岁儿童维生素A缺乏调查   总被引:3,自引:3,他引:0  
李慰  仇赛云  万英  包汉平 《中国妇幼保健》2005,20(15):1973-1975
目的:了解云南省城乡0~5岁儿童维生素A营养状况及影响因素。方法:省、地、县随机整群抽取600例儿童,采用微量荧光光度法检测VitA含量。结果:VitA缺乏发生率16·17%,地、县明显高于省会城市;0岁儿童明显高于其他年龄组;腹泻儿童明显高于正常儿童;VitA缺乏的影响因素:近1周内进食鸡蛋、奶类制品、鱼虾类、肝类、黄绿色蔬菜、鱼肝油等食物有利于维生素A的吸收,急性呼吸道感染、发烧与维生素A缺乏发生率差异不明显。结论:维生素A缺乏发生率城市明显低于农村地、县两级,说明维生素A缺乏防治工作重点在农村,特别是0岁儿童,防治的主要措施是采取合理膳食,均衡营养,控制腹泻流行。  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