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   38896篇
  免费   2406篇
  国内免费   1567篇
耳鼻咽喉   299篇
儿科学   874篇
妇产科学   522篇
基础医学   6326篇
口腔科学   875篇
临床医学   3632篇
内科学   5370篇
皮肤病学   1217篇
神经病学   1668篇
特种医学   818篇
外国民族医学   6篇
外科学   1863篇
综合类   6209篇
现状与发展   4篇
预防医学   2539篇
眼科学   409篇
药学   7014篇
  13篇
中国医学   1236篇
肿瘤学   1975篇
  2024年   54篇
  2023年   406篇
  2022年   711篇
  2021年   1244篇
  2020年   1016篇
  2019年   939篇
  2018年   912篇
  2017年   990篇
  2016年   971篇
  2015年   1067篇
  2014年   2031篇
  2013年   2124篇
  2012年   2088篇
  2011年   2469篇
  2010年   2082篇
  2009年   1925篇
  2008年   2018篇
  2007年   2126篇
  2006年   1804篇
  2005年   1885篇
  2004年   1568篇
  2003年   1509篇
  2002年   1290篇
  2001年   1126篇
  2000年   1065篇
  1999年   1026篇
  1998年   922篇
  1997年   804篇
  1996年   649篇
  1995年   711篇
  1994年   613篇
  1993年   448篇
  1992年   402篇
  1991年   287篇
  1990年   206篇
  1989年   155篇
  1988年   139篇
  1987年   120篇
  1986年   90篇
  1985年   146篇
  1984年   138篇
  1983年   107篇
  1982年   109篇
  1981年   96篇
  1980年   67篇
  1979年   48篇
  1978年   36篇
  1977年   41篇
  1976年   38篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 271 毫秒
81.
82.
The expression of MHC isoforms in the skeletal muscles of nine patients with Duchenne muscular dystrophy (DMD) (from 2.5 to 15 yr of age) and three DMD carriers was studied using different specific anti-MHC MAbs. We also analyzed muscle fiber size and fiber reactivity with acridine orange and/or with a surface antigen marker. One-quarter of all fibers of DMD patients, or less with age, were of normal size and contained only adult slow MHC. Half of the muscle fibers contained adult and developmental MHCs. Only half of these fibers were representative of an active regenerative process. MHC co-expression also altered the proportion of normal fast or slow fibers. Adult fast MHCs were expressed as unique MHC only in small and very small fibers in the oldest DMD patients. In DMD carrier muscles, the greatest alterations in MHC expression were observed in patients with the most reduced dystrophin expression. However, MHC changes in dystrophin-positive fibers were similar to those observed in dystrophin-free fibers. In conclusion, disruptions or delays in the switching of all genes coding for adult fast and slow MHC and developmental MHC coincided with dystrophin deletion and with perturbations in its expression.  相似文献   
83.
84.
[背景]观察抗结核药物的不良反应.[病例报告]对293例应用抗结核药物后出现不良反应的患者资料进行分析,抗结核药物常见不良反应的有肝脏损害、胃肠道反应、听力障碍及关节痛等.[讨论]应依据患者的具体情况,选择不同的抗结核药物进行联合应用.  相似文献   
85.
OBJECTIVES: Vesicoureteral reflux (VUR) is the most common congenital urinary tract anomaly. This disease can pose a major threat to the kidneys as twenty percent of patients with endstage renal disease are reported to have VUR. Although genetic studies for uroplakin III (UPIII) have been reported recently, no study has focused on UPIII gene expression in VUR patients. We describe here the up-regulation of UPIII mRNA in exfoliated urinary cells from primary VUR patients. METHODS: A real-time RT-PCR for UPIII mRNA was performed on exfoliated urothelial cells from 18 primary VUR and 38 control samples. UPIII mRNA copies were calculated for each sample. The statistical differences were assessed by the Mann-Whitney U test. Receiver operator characteristic curves were constructed for analysis of the diagnostic values. RESULTS: UPIII mRNA was found to be up-regulated to a greater extent in VUR than in control exfoliated urinary cells (mean +/- SE: 497.0 +/- 178.5 copies vs. 69.0 +/- 10.0 copies, respectively, P < 0.001). In evaluating the measurement of urinary UPIII mRNA as a screening test for VUR, the sensitivity was 77.8% and the specificity was 76.3% by the best diagnostic cutoff point. CONCLUSIONS: This is the first report demonstrating up-regulation of UPIII in mRNA levels in VUR patients. We submit that the quantitative measurement of urinary UPIII mRNA has a potential of developing into the first non-invasive screening test for VUR.  相似文献   
86.
本文对1984年1~3月和1985年3~8月共107例急性下呼吸道感染的住院患儿,采用间接免疫荧光法检测其急性期血清抗RSV特异性IgM抗体,并与病毒分离和/或中和试验比较,敏感性为82.1%,特异性为71.8%。RSV感染患儿发病后3天内大多数病例即可从血清中检测出RSV-IgM,因此该法具有早期诊断价值。  相似文献   
87.
Abstract Over the past 15–20 years, research has progressively focused on the mucosal T cell as the central factor in the initiation of physiological or pathological changes, first in the growth and maturation of the early (postnatal) intestine, and second in adult-type enteropathies resulting from sensitivity to either food or pathogen-derived antigens. T cell-mediated events may be measured, for example, in terms of specific immunopathologic patterns of change and injury, such as type 1 (lymphocyte infiltration), type 2 (crypt hyperplasia) and type 3 (flat-destructive), which can be recognized and quantitated microscopically; by determination of lymphocyte reactivity through secretion of interleukin-2 receptors (IL-2R) into plasma or expression by mucosal lymphocytes; by quantitation of lymphocyte subsets emigrating into inflamed tissues by immunoperoxidase-labelled monoclonal antibodies; or by the determination of T cell receptor polymorphisms. Alterations in intestinal growth, structure and function at weaning are likely to be T cell-mediated as they are analogous to the same type 1/2 lesions that reflect modulation of adult mucosal architecture in food and parasite-induced hypersensitivity reactions. Enteropathies associated with HIV infection and T cell deficiency display a milder degree of villous flattening and impaired crypt hyperplasia than that typical of gluten-sensitivity, suggesting a reversion to lesser degrees of mucosal pathology (type 1/2). Clearly more information will accrue; meanwhile the remarks in this brief survey should provide a firm basis whereby clinician and scientist can meet, and together recognize and further dissect the modulatory effect of T lymphocytes on mucosal structure and function.  相似文献   
88.
巢式PCR检测先天性心脏病心脏石蜡标本中B19病毒的感染   总被引:2,自引:0,他引:2  
王晓明  张国成 《医学争鸣》1998,19(3):271-273
目的:探讨微小病毒B19与先天性心脏病(CHD)的相关性及可能致畸机理。方法:采用病例对照研究,病例组为29例CHD尸解心脏组织,对照组为30例同期非先天性畸形尸解心脏组织,应用巢式PCR扩增B19-DNA,单纯疱疹病毒(HSV),兔弓形虫(TOX),巨细胞病毒(CMV),结果:29例CHDB19-DNA5例阳性,全瓿对照组为均阴性(P=0.0237),HSV,TOX两组中均阴性,CMV在两组中均  相似文献   
89.
ltiswellknownthattheskinofextensivelyburnedcasesthemselvesisinsufficienttoprovidecoverageforwounds.Thoughallogeneicskincancoverthewoundstemporari1y,itwillberejectedwithin2-3weeks.Thiscanthreatenthepatient'slifeifthereisnoenoughautogenousskintoreplacetherejectedoneontime.GreenetalL1]reportedthattheburnwoundsofpatientswithextensiveburnscouldbetreatedbytransplantingepidermalautograftsafterautologousepidermalcellsmulti-plyforthousandsoftimesinvltrowithinashortperiodoftime-Butittakesatleast2-3weeks…  相似文献   
90.
以环己酮为起始原料,经与苯肼缩合、氧化、Mannich 反应制得1,2,3,9-四氢-3-二甲胺基甲基-4H-咔唑-4-酮盐酸盐(5),后者再与2-甲基咪唑缩合、甲基化合成翁丹西隆,总收率为10.4%。  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