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   21925篇
  免费   2180篇
  国内免费   1870篇
耳鼻咽喉   155篇
儿科学   178篇
妇产科学   279篇
基础医学   2794篇
口腔科学   238篇
临床医学   3081篇
内科学   3146篇
皮肤病学   192篇
神经病学   1276篇
特种医学   856篇
外国民族医学   13篇
外科学   2077篇
综合类   3698篇
现状与发展   5篇
一般理论   1篇
预防医学   1491篇
眼科学   655篇
药学   2522篇
  29篇
中国医学   1517篇
肿瘤学   1772篇
  2024年   72篇
  2023年   393篇
  2022年   972篇
  2021年   1206篇
  2020年   963篇
  2019年   734篇
  2018年   765篇
  2017年   762篇
  2016年   716篇
  2015年   1076篇
  2014年   1340篇
  2013年   1135篇
  2012年   1585篇
  2011年   1905篇
  2010年   1169篇
  2009年   989篇
  2008年   1165篇
  2007年   1140篇
  2006年   1132篇
  2005年   1151篇
  2004年   727篇
  2003年   701篇
  2002年   561篇
  2001年   485篇
  2000年   509篇
  1999年   525篇
  1998年   311篇
  1997年   323篇
  1996年   247篇
  1995年   243篇
  1994年   204篇
  1993年   120篇
  1992年   132篇
  1991年   91篇
  1990年   95篇
  1989年   79篇
  1988年   70篇
  1987年   68篇
  1986年   53篇
  1985年   25篇
  1984年   9篇
  1983年   8篇
  1982年   7篇
  1981年   5篇
  1980年   2篇
  1979年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
目的 探讨不同生长激素分泌状态下矮身材儿童血脂水平的差异,为生长激素缺乏对儿童体脂代谢的影响提供理论依据。方法 收集矮身材儿童188例,依据生长激素药物激发试验峰值分为生长激素完全缺乏(cGHD)组、生长激素部分缺乏(pGHD)组、非生长激素缺乏性(nGHD)组,研究对象均禁食禁水10 h后空腹测定总胆固醇(TC)、三酰甘油(TG)、低密度脂蛋白胆固醇(LDL)和高密度脂蛋白胆固醇(HDL)4项血脂水平。结果 3组儿童HDL水平比较差异无统计学意义(P>0.05);3组儿童TC、TG、LDL、non-HDL水平比较差异均有统计学意义(P<0.05);组间两两比较,cGHD组TC、LDL、non-HDL水平较其他组明显升高(P<0.05),cGHD组TG水平较nGHD明显升高(P<0.05),与pGHD组比较差异无统计学意义(P>0.05)。pGHD、nGHD组高TC、高LDL及高non-HDL的发生率明显低于cGHD组(P<0.05),nGHD组临界高LDL的发生率明显低于cGHD组(P<0.05)。而3组间TG、HDL的异常发生率及TC、TG...  相似文献   
102.
The Brca2 tumor-suppressor gene contributes to genomic stability, at least in part by a role in homologous recombinational repair. BRCA2 protein is presumed to function in homologous recombination through interactions with RAD51. Both exons 11 and 27 of Brca2 code for domains that interact with RAD51; exon 11 encodes eight BRC motifs, whereas exon 27 encodes a single, distinct interaction domain. Deletion of all RAD51-interacting domains causes embryonic lethality in mice. A less severe phenotype is seen with BRAC2 truncations that preserve some, but not all, of the BRC motifs. These mice can survive beyond weaning, but are runted and infertile, and die very young from cancer. Cells from such mice show hypersensitivity to some genotoxic agents and chromosomal instability. Here, we have analyzed mice and cells with a deletion of only the RAD51-interacting region encoded by exon 27. Mice homozygous for this mutation (called brca2(lex1)) have a shorter life span than that of control littermates, possibly because of early onsets of cancer and sepsis. No other phenotype was observed in these animals; therefore, the brca2(lex1) mutation is less severe than truncations that delete some BRC motifs. However, at the cellular level, the brca2(lex1) mutation causes reduced viability, hypersensitivity to the DNA interstrand crosslinking agent mitomycin C, and gross chromosomal instability, much like more severe truncations. Thus, the extreme carboxy-terminal region encoded by exon 27 is important for BRCA2 function, probably because it is required for a fully functional interaction between BRCA2 and RAD51.  相似文献   
103.
活性氧自由基在生物体内参与生理,病理过程并起重大作用,在筛选和评价抗氧化药物时,越来越需要一种快速,简便,价廉而又可靠的抗氧化活性测定方法,本文发展了一种具备了上述优点新方法,SOD(超氧化物歧化酶)及其模拟物的工作已有很多,很多文献报道了其活性一;Cu(Ⅱ)。本文着重研究了另一个金属辅基,Zn^2+并且发现了Zn^2+独特的,但为人们忽视了的;抗氧化活性加强作用。  相似文献   
104.
Summary. To elucidate the mode of transmission of Puumala-related hantavirus in a population of gray red-backed voles, Clethrionomys rufocanus bedfordiae, in Hokkaido, Japan, we analyzed the kin structure and dispersal patterns of individual voles using microsatellite and mitochondrial DNA markers. Siblings or dam/offsprings was identified within the population based on the relatedness calculation with the microsatellite data. The pairwise relatedness values obtained could reveal kinship among all vole individuals within the population. Based on the assessment of kinship, we did not find a positive relationship between hantavirus transmission and close kinship. Males infected with the hantavirus carried a relatively uncommon mitochondrial haplotype. However, these infected males shared low relatedness values and were not considered closely related, i.e., they were not siblings or parent/offspring. These observations imply that hantavirus transmission in the vole population may not be related to close kinship but by random horizontal infection.  相似文献   
105.
The possible characteristics of spinal interaction between sildenafil (phosphodiesterase 5 inhibitor) and morphine on formalin-induced nociception in rats was examined. Then the role of the opioid receptor in the effect of sildenafil was further investigated. Catheters were inserted into the intrathecal space of male Sprague-Dawley rats. For induction of pain, 50 µL of 5% formalin solution was applied to the hind-paw. Isobolographic analysis was used for the evaluation of drug interaction between sildenafil and morphine. Furthermore, naloxone was intrathecally given to verify the involvement of the opioid receptor in the antinociception of sildenafil. Both sildenafil and morphine produced an antinociceptive effect during phase 1 and phase 2 in the formalin test. The isobolographic analysis revealed an additive interaction after intrathecal delivery of the sildenafil-morphine mixture in both phases. Intrathecal naloxone reversed the antinociception of sildenafil in both phases. These results suggest that sildenafil, morphine, and the mixture of the two drugs are effective against acute pain and facilitated pain state at the spinal level. Thus, the spinal combination of sildenafil with morphine may be useful in the management of the same state. Furthermore, the opioid receptor is contributable to the antinocieptive mechanism of sildenafil at the spinal level.  相似文献   
106.
A locus for spondylocarpotarsal synostosis syndrome at chromosome 3p14   总被引:3,自引:0,他引:3  
Spondylocarpotarsal synostosis syndrome is a rare autosomal recessive disorder characterised by vertebral fusions, frequently manifesting as an unsegmented vertebral bar, as well as fusions of the carpal and tarsal bones.

In a study of three consanguineous families and one non-consanguineous family, linkage analysis was used to establish the chromosomal location of the disease gene. Linkage analysis localised the disease gene to chromosome 3p14. A maximum lod score of 6.49 (q = 0) was obtained for the marker at locus D3S3532 on chromosome 3p. Recombination mapping narrowed the linked region to the 5.7 cM genetic interval between the markers at loci D3S3724 and D3S1300. A common region of homozygosity was found between the markers at loci D3S3724 and D3S1300, defining a physical interval of approximately 4 million base pairs likely to contain the disease gene.

Identification of the gene responsible for this disorder will provide insight into the genes that play a role in the formation of the vertebral column and joints.

  相似文献   
107.
目的 探讨不同剂量生长激素 (GH)在体外受精 -胚胎移植 (IVF -ET)中 ,对低反应患者超排卵周期的作用。方法 前一IVF周期卵巢低反应的患者 30例 ,她们在前一周期采用促性腺激素释放激素激动剂 (GnRH -a)和促性腺激素(Gn)治疗 ,本周期采用GnRH -a、Gn、GH(两种不同剂量 )治疗 ,比较两种不同剂量生长激素的作用。结果 两种剂量生长激素均可提高受精率 ,增加优质胚胎数 ,提高妊娠率 ,且不同剂量生长激素间的作用无显著差异。结论 生长激素在IVF超排卵中有辅助作用 ,且不同剂量作用无显著差异  相似文献   
108.
目的近年来有研究发现α2-巨球蛋白基因(α2-macroglobulin,A2M)Ile1000Val多态与阿尔茨海默氏病(Alzheimer’s disease,AD)发病有关联,但也有相悖的研究结果报道。因此.我们利用较大的样本,观察了A2M基因Ile1000Val多态在广州及成都地区汉族老年人中的分布,并探讨其与散发AD的相关性。方法以广州地区257例散发AD患者和242名正常老年人、成都地区112例散发AD患者和113名正常老年人为对象进行病例一对照研究。用聚合酶链反应一限制性片段长度多态性方法分析A2M基因11000V多态性和载脂蛋白E基因(apolipoprotelnE,apoE)多态性。结果(1)在两地合并样本中,AD患者与对照组中等位基因A2M-1000V的频率分别为7.7%与8.7%,广州与成都地区AD患者与对照组中A2M基因I1000V多态的分布差异无统计学意义。(2)散发AD无论按是否伴有apoE—ε4或按发病年龄分成不同亚组后,A2M基因I1000V多态的分布在病例组与对照组之间差异无统计学意义。结论广州与成都汉族人群中A2M基因I1000V多态与散发AD不具有关联。  相似文献   
109.
不同浓度的甘油蔗糖保护剂对人类精子冻存效果的研究   总被引:1,自引:0,他引:1  
王燕蓉  马宁芳 《解剖学报》1992,23(2):221-224
  相似文献   
110.
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