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   88256篇
  免费   8028篇
  国内免费   6561篇
耳鼻咽喉   723篇
儿科学   921篇
妇产科学   1061篇
基础医学   10799篇
口腔科学   1651篇
临床医学   12084篇
内科学   13252篇
皮肤病学   835篇
神经病学   4799篇
特种医学   3237篇
外国民族医学   61篇
外科学   8592篇
综合类   15056篇
现状与发展   30篇
一般理论   3篇
预防医学   5242篇
眼科学   2546篇
药学   9172篇
  68篇
中国医学   4832篇
肿瘤学   7881篇
  2024年   320篇
  2023年   1649篇
  2022年   3859篇
  2021年   4691篇
  2020年   3509篇
  2019年   3066篇
  2018年   3143篇
  2017年   2883篇
  2016年   2622篇
  2015年   4141篇
  2014年   4954篇
  2013年   4204篇
  2012年   6335篇
  2011年   7146篇
  2010年   4286篇
  2009年   3283篇
  2008年   4204篇
  2007年   4509篇
  2006年   4430篇
  2005年   4556篇
  2004年   2787篇
  2003年   2559篇
  2002年   2231篇
  2001年   1917篇
  2000年   2158篇
  1999年   2508篇
  1998年   1673篇
  1997年   1589篇
  1996年   1222篇
  1995年   1063篇
  1994年   890篇
  1993年   604篇
  1992年   716篇
  1991年   610篇
  1990年   553篇
  1989年   476篇
  1988年   393篇
  1987年   350篇
  1986年   248篇
  1985年   192篇
  1984年   93篇
  1983年   76篇
  1982年   41篇
  1981年   46篇
  1980年   29篇
  1979年   30篇
  1965年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Alport's syndrome is characterized clinically by a nonimmune glomerulopathy, often accompanied by sensorineural hearing loss and lens abnormalities, frequently due to mutations in the COL4A5 gene. The association of AS with diffuse leiomyomatosis, a benign proliferation of smooth muscle that occurs most often in the esophagus, trachea, and female genitalia, has been reported. Recently, a deletion involving both the COL4A5 and COL4A6 genes has been reported in four unrelated families. We report an additional case with Alport's syndrome associated with leiomyomatosis carrying a deletion of both COL4A5 and COL4A6 genes. A detailed characterization of the genomic region involved in the deletion event has been performed. Our results demonstrate that the deletion removed exon l of COL4A5 and exons l and 2 of COL4A6. © 1994 Wiley-Liss, Inc.  相似文献   
92.
93.
94.
脐带血清对骨髓粒—巨噬细胞集落形成的影响   总被引:1,自引:0,他引:1  
在骨髓细胞半固体琼脂培养体系中,研究脐带血清(CBs)对骨髓粒—巨噬细胞集落形成单位(CFU-GM)的影响,单纯应用CBs培养可使骨髓CFU-GM(x±s为26.0375±10.2327)显著的高于正常成人外周血清(PBs)组(x±s为11.5917±3.6047;P<0.001)。CBs加粒-巨噬细胞刺激因子,GM-CSF组CFU-GM(x±s为119.0792±35.0991)是单纯CBs组的4.57倍;而PBs加GMC-SF组(x±s为97.125±26.7559)是单纯PBs组的8.38倍。有白细胞介素-6(IL-6)存在的CBs组,CFU-GM(x±s为31.9333±10.9144)明显的高于单纯CBs组(P<0.02)。提示CBs中含有较高水平的内源性GM-CSF。  相似文献   
95.
We report that gp49B1, a mast cell membrane receptor with two immunoreceptor tyrosine-based inhibitory motifs (ITIM), constitutively inhibits mast cell activation-secretion induced by stem cell factor (SCF), a tissue-derived cytokine that also regulates mast cell development. The intradermal injection of SCF into the ears of gp49B1 null (gp49B(-/-)) mice elicited approximately 4- and 2.5-fold more degranulating mast cells and tissue swelling caused by edema, respectively, than in gp49B(+/+) mice. SCF did not induce tissue swelling in mast cell-deficient mice, and the responsiveness of gp49B(-/-) mice to mast cell-associated amine and lipid mediators was unaltered. When gp49B(+/+) and gp49B(-/-) mice were pretreated with antagonists of the amines, SCF-induced tissue swelling was reduced by >90% and 60%, respectively, and it was reduced by >90% in both genotypes when a cysteinyl leukotriene receptor antagonist was also provided. Hence, the dominant contribution of secretory granule amines to SCF-induced tissue swelling is the result of gp49B1-mediated inhibition of the production of cysteinyl leukotrienes by mast cells. Our findings also provide the first example of an ITIM-bearing receptor that constitutively suppresses inflammation generated in vivo independently of the adaptive immune response by a receptor that signals through intrinsic tyrosine kinase activity rather than immunoreceptor tyrosine-based activation motifs.  相似文献   
96.
胃动素对血管灌流大鼠离体胃运动的作用   总被引:8,自引:1,他引:8  
通过血管灌流大鼠离体胃,探讨胃动素对胃运动的影响。结果表明:(1)胃动素可以明显地兴奋胃窦自发的胃运动;(2)胃动素抗血清可以完全消除胃动素兴奋胃窦运动的作用;(3)阿托品可以阻断胃动素兴奋胃窦运动的作用。上述结果提示,胃动素可特异性兴奋血管灌流大鼠胃窦收缩运动,该作用通过壁内胆碱能神经介导。  相似文献   
97.
调查了90具童尸用状腺的基本形态,可分四型。其中以甲状腺由两侧叶及峡部组成者为最多,占50.22%。测量了甲状腺各部的长、宽、厚。分年龄组进行了数据的统计学处理,并计算出儿童与成人甲状腺各部相应值的百分比。结果显示:小儿甲状腺侧叶的长度和宽度在幼儿期(1—3岁)就已发育近成人的一半。随着年龄的增长,甲状腺各部的均值逐渐增加。除各部的宽度以及锥体叶的长度外,各相邻两组间同项均数的比较,经双侧T检验发现差异具有高度显著性(P<0.01)。  相似文献   
98.
The medullary raphe (MR) and the retrotrapezoid nucleus (RTN) in the ventral medulla are two of many central chemoreceptor sites. We examine their combined function in conscious rats by focal inhibition using microdialysis. Inhibition of RTN neurons with the GABAA receptor agonist muscimol, with simultaneous dialysis of artificial cerebrospinal fluid (ACSF) in or near to the caudal MR, causes hypoventilation (decrease in the ratio of minute ventilation to oxygen consumption,     ) and reduces the ventilatory response to 7% CO2 by 24%. Inhibition of caudal MR serotonergic neurons with the 5-HT1A receptor agonist ( R )-(+)-8-hydroxy-2(di- n -propylamino)tetralin (8-OH-DPAT), with simultaneous dialysis of ACSF in or near to the RTN, causes hypoventilation but has no significant effect on the CO2 response. Inhibition of both the RTN and the caudal MR simultaneously produces enhanced hypoventilation and a 51% decrease in the CO2 response. The effects of treatment on the CO2 response are similar in wakefulness and in non-rapid eye movement sleep. Comparison of the effect of 8-OH-DPAT microdialysed into a more rostral portion of the MR, where the CO2 response is reduced by 22%, demonstrates heterogeneity within the MR of the function of serotonergic neurons in breathing. We conclude that serotonergic neurons within the caudal MR provide a non-CO2-dependent tonic drive to breathe and potentiate the effects of RTN neurons that contribute to a resting chemical 'drive to breathe' as well as the response to added CO2. These effects of caudal MR serotonergic neurons could be at a chemoreceptor site, e.g. the RTN, or at 'downstream' sites involved in rhythm and pattern generation.  相似文献   
99.
AIM: To clone human anti-TNF-alpha scFv from large phage antibody library. METHODS: Panning of large phage library against TNF-alpha was conducted to select specific antibodies. The antigen binding activity and DNA sequence were determined and analyzed by ELISA, restriction enzyme map. RESULTS: After 4 rounds of panning, 62 positive clones were obtained and 27 clones had specific binding ability to TNF-alpha. DNA fingerprinting of the 27 clones showed 7 different stripes indicated 7 different positive clones. 5 of the 7 clones expressed soluble anti-TNF-alpha activity. DNA sequence analysis showed that the variable regions of these scFvs belonged to different subgroups. CONCLUSION: Human TNF-alpha scFv have been successfully obtained from large phage antibody library.  相似文献   
100.
Thickening of the tubular basement membrane (TBM) occurs in diabetic nephropathy, but the effects of high glucose on the functional aspects of proximal tubular epithelial cells are not clearly understood. In the present study, we examined the effects of elevated glucose concentrations on (a) integrin expression by human proximal tubular epithelial cells (HK-2) and integrin-mediated interactions with type IV collagen (colIV) and laminin, major components of TBM; (b) the expression of matrixins/matrix metalloproteinases (MMPs), which is regulated by integrins; and (c) the expression of tissue inhibitors of metalloproteinases (TIMPs). HK-2 cells cultured in 25 mM glucose underwent a reduction of the expression of alpha3, beta1, alpha(v)beta3, and alpha5 integrin subunits, with a concomitant increase of the alpha2 subunit, compared with cells grown in 5 mM glucose. Adhesion experiments demonstrated that high glucose led to increased cell adhesion on either colIV or laminin. Experiments of competition of adhesion using anti-integrin antibodies indicated that HK-2 cells in 5 mM glucose used mainly alpha(v)beta3 and alpha5beta1 integrins to adhere to colIV, whereas in 25 mM glucose they additionally used alpha2beta1. In the case of laminin, a beta1-mediated adhesion was observed when HK-2 cells were in 5 mM glucose, whereas in 25 mM glucose, alpha2beta1 and alpha(v)beta3 were also involved. Elevated glucose concentrations resulted in decreased expression of MMP-9 and MMP-2, whereas an increase in TIMP-1 and a decrease in TIMP-2 expression were observed. We also examined which integrins mediated the expression and secretion of matrixins MMP-2 and MMP-9. Ligation of alpha3beta1 with mAbs resulted in induction of MMP-2 expression and secretion, whereas antibody ligation of alpha(v)beta3 led to down-regulation of MMP-9. The above data implicate integrins of proximal tubular epithelial cells in the regulation of MMPs and in the development of TBM thickening in diabetic nephropathy.  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