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   19849篇
  免费   1951篇
  国内免费   452篇
耳鼻咽喉   63篇
儿科学   1798篇
妇产科学   283篇
基础医学   2210篇
口腔科学   163篇
临床医学   1410篇
内科学   3023篇
皮肤病学   175篇
神经病学   908篇
特种医学   358篇
外科学   1282篇
综合类   3131篇
现状与发展   2篇
预防医学   1801篇
眼科学   267篇
药学   897篇
  11篇
中国医学   4218篇
肿瘤学   252篇
  2024年   77篇
  2023年   351篇
  2022年   684篇
  2021年   1124篇
  2020年   999篇
  2019年   704篇
  2018年   646篇
  2017年   847篇
  2016年   810篇
  2015年   724篇
  2014年   1319篇
  2013年   1274篇
  2012年   1067篇
  2011年   1150篇
  2010年   853篇
  2009年   774篇
  2008年   732篇
  2007年   762篇
  2006年   709篇
  2005年   594篇
  2004年   549篇
  2003年   479篇
  2002年   385篇
  2001年   401篇
  2000年   348篇
  1999年   315篇
  1998年   295篇
  1997年   265篇
  1996年   215篇
  1995年   252篇
  1994年   227篇
  1993年   197篇
  1992年   185篇
  1991年   197篇
  1990年   165篇
  1989年   157篇
  1988年   158篇
  1987年   124篇
  1986年   127篇
  1985年   161篇
  1984年   122篇
  1983年   80篇
  1982年   117篇
  1981年   102篇
  1980年   77篇
  1979年   92篇
  1978年   48篇
  1977年   47篇
  1976年   52篇
  1975年   31篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
基于"WD倒谱"法分析人体脾组织的超声散射微结构特征   总被引:1,自引:1,他引:1  
本文提出了一种对超声散射信号分析的新方法--“WD倒谱”法,并利用该方法对人体正常脾和脾增生组织的回波信号进行了分析,对软组织中散射子的平均间距进行了估计,结果表明:两种脾组织散射子的平均同距明显不同;“WD倒谱”能有效的反映软组织的微观结构特征,说明“WD倒谱”是软组织超声散射信号分析与软组织散射子平均间距定征的一种有效方法。  相似文献   
132.
Whole blood samples of known methylene tetrahydrofolate reductase (MTHFR) genotypes from 24 individuals were examined at site C677T. Their amplified DNA products were assessed by two-color fluorescence cross-correlation measurements and agarose gel electrophoresis/capillary gel electrophoresis. DNA subpopulations were identified which were not associated with the proper genotype by primer combinations and cycling conditions called multiplexes. We confirmed that DNA analysis by two-color fluorescence cross-correlation measurements allowed the detection of fluorescence signals specifically associated with the proper genotypes in a mixture of amplified nontarget DNA molecules without DNA sizing. The measurement approach does not require complex, follow-up mathematical analysis and is applicable to any single nucleotide polymorphisms. The simple immunogenetic model showed how the approach works to reveal specific DNA target by preventing detection of nontarget DNA. Under those experimental conditions, a new ultrasensitive, and specific method for clinical immunologists is born.  相似文献   
133.
目的 探讨新生儿C6PD缺陷病和晚发性维生素K缺乏症的危害与预防措施。方法 回顾分析1995-2000年儿内科住院的1周-2月(不含2月)的婴儿3104例次,其中病死56例。结果 1周-2月的小婴儿占住院患儿的19.34%,其中新生儿G6PD缺陷病239例,占7.70%;晚发性维生素K缺乏症92例,占2.96%。死因的第2、3位分别是晚发性维生素K缺乏症(13例,占23.21%)和新生儿C6PD缺陷病(12例,占21.43%),两者的病死率分别为14.13%和5.02%,极显著高于(x^2=17.59,P<0.01)或相近于(x^2=0.88,P>0.05)肺炎的3.57%。新生儿G6PD缺陷病合并感染占38.49%、低氧血症占23.35%、低血糖占19.25%、酸中毒占15.90%,继发胆红素脑病占13.81%。晚发性维生素K缺乏症出现抽搐占90.22%、胃肠、注射部位出血占60.89%;CT证实颅内出血占98.91%。结论 1周-2月的小婴儿约占住院患儿的两成,新生儿G6PD缺陷病和晚发性维生素K缺乏症的病死率均很高,两者是除肺炎外最主要的死因。提议制定并推广预防这2种疾病的常规措施,并参照国内外相应的现状拟出其具体内容。  相似文献   
134.
灵芝多糖对小鼠脾脏树突状细胞的增殖作用   总被引:5,自引:0,他引:5  
目的 观察灵芝多糖(GP)对小鼠脾脏树突状细(dendrirtie cells,DCs)的增殖作用。方法采用MTT法,以细胞因子(GM-CSF+IL-4)作比较,观察不同质量浓度GP以及细胞因子+不同浓度的GP对小鼠脾脏DCs的增殖作用。结果GP(5-80μg/mL)可明显刺激小鼠脾脏DCs增殖,与细胞因子组相比,其较高质量浓度组(20、40、80μg/mL)作用明显;GP+细胞因子,与对照组相比均有显著的增殖作用,且明显高于细胞因子组。结论GP不仅能促进小鼠脾脏DCs的增殖,而且与细胞因子有显著的协同作用。具有类生长因子和协同生长因子的作用。  相似文献   
135.
In search for a possible explanation of the phenotypic heterogeneity in IgA deficiency, we studied the function of B cells from IgA-deficient (IgAd) individuals. Two groups of IgAd individuals, one frequently infected and one clinically apparently healthy, as well as normal controls, were studied. Peripheral blood mononuclear cells (PBMC) and B cells from IgAd individuals and controls were cultured with Staphylococcus aureus Cowan I strain and with anti-CD40 MoAb presented on the CD32-transfected fibroblast cell line in the presence of IL-10. In this experimental system PBMC and B cells from the infection-prone IgAd individuals produced only minute amounts of IgA. In contrast, PBMC and B cells from healthy IgAd subjects secreted significantly more IgA1 and IgA2 in comparison with infection-prone IgAd patients (P < 0.05). These data suggest that the abnormalities of B cell differentiation in IgAd could be of heterogeneous origin. Thus, whereas in healthy IgAd subjects IgA production may be efficiently up-regulated in vitro by addition of IL-10 to CD40-activated B cell culture, the corresponding B cell differentiation does not occur in infection-prone IgAd patients. These observations provide a conceptual framework for phenotypic heterogeneity in IgAd subjects.  相似文献   
136.
137.
目的 初步了解中国汉族女性雄激素过多症患者中2 1-羟化酶缺陷症(2 1- hydroxylasedeficiency,2 1- OHD)携带者发生率,探讨促肾上腺皮质激素(adrenocorticotropic hormone,ACTH)兴奋试验结果与基因突变检测结果的相关性。方法 82例汉族女性雄激素过多症患者及14名健康女性进行ACTH兴奋试验,并应用PCR扩增产生限制性酶切位点方法检测已知的9个2 1- OHD常见突变位点。结果 雄激素过多组(n=82 ) F0 显著高于正常对照组(P<0 .0 1) ;17- OHP0 及17- OHP6 0 也显著高于对照组(P<0 .0 1) ,而F6 0 差异没有统计学意义(P>0 .0 5 )。比较17- OHP净增值及17- OHP净增值/ F净增值,雄激素过多组也均显著高于正常对照组(P<0 .0 1)。正常对照组未检测出细胞色素P4 5 0 (cytochrome P4 5 02 1,CYP2 1)基因突变。发现雄激素过多组4例CYP2 1基因突变携带者(4/ 82 ,4 .9% ) ,分别携带V2 81L(2例) ,i2 g及Q318X(各1例) ,携带者的ACTH兴奋试验结果与正常对照及未检出突变的雄激素过多症患者的结果存在一定的交叉。结论 82例汉族雄激素过多症女性中2 1- OHD携带者为4例,占4 .9%。ACTH兴奋试验不能用以发现携带者,应进行基因检测确定。  相似文献   
138.
139.
Muscle cell leakage due to long distance training   总被引:3,自引:0,他引:3  
Summary Abnormal myoglobinemia (above 77 g/1) and free hemoglobin in plasma were found in 16 runners and in nine non runners immediately following distance running. The same abnormalities were found in six elite rowers following rowing. In parallel with the rise in myoglobin and free hemoglobin a rise was found in serum concentrations of cellular enzymes (LDH, CK, ASAT, alkaline phosphatase) and of various metabolites. We found no proteinuria nor casts in the urine. Non runners had a higher rise in serum myoglobin than runners. Competitive running caused a rise in the serum concentration of the heart specific fraction of creatine kinase in seven of the nine (healthy) elite runners. The abnormal findings are only explainable on the basis of leakage of proteins from muscle cells to the circulation in otherwise healthy, well trained persons. Myoglobinemia and a transient rhabdomyolysis is a common phenomenon in long distance running, but evidently also occurs in distance rowing. Three months of running training prevented most of the muscle damage from relaxed jogging in the nine previous non runners. Neither the observed myoglobinemia nor the hemoglobinemia resulted in any significant loss of iron in the urine.Supported by IdrÆttens Forskningsråd, Dansk IdrÆtsforbund  相似文献   
140.
Class switch recombination (CSR), somatic hypermutation, and gene conversion are immunoglobulin diversification mechanisms that are strictly dependent on the activity of the activation-induced cytidine deaminase (AID). The precise role and substrate(s) of AID in these processes remain to be well defined. The closest homologue of AID is APOBEC-1, a bona fide mRNA-editing enzyme, which shares with AID the ability to deaminate cytidines within single-stranded DNA in vitro and in prokaryotic cells. To determine whether APOBEC-1 can therefore substitute for AID in activated B cells, we expressed human AID, a catalytic mutant thereof, and rat APOBEC-1 in AID-deficient murine B cells. Whereas AID rescued CSR, neither the inactive mutant nor APOBEC-1 could complement AID deficiency. This indicates that cytidine deaminase activity is necessary but not sufficient to initiate CSR, and suggests that AID is specifically targeted to its cognate substrate, the immunoglobulin genes or a distinct mRNA, by an as-yet-unknown mechanism.  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