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   110525篇
  免费   9541篇
  国内免费   6304篇
耳鼻咽喉   1173篇
儿科学   1598篇
妇产科学   2339篇
基础医学   12953篇
口腔科学   2011篇
临床医学   14696篇
内科学   17184篇
皮肤病学   958篇
神经病学   5903篇
特种医学   3906篇
外国民族医学   58篇
外科学   12053篇
综合类   16016篇
现状与发展   27篇
一般理论   20篇
预防医学   6471篇
眼科学   2960篇
药学   11374篇
  65篇
中国医学   5194篇
肿瘤学   9411篇
  2024年   315篇
  2023年   1608篇
  2022年   4132篇
  2021年   5324篇
  2020年   3905篇
  2019年   3452篇
  2018年   3774篇
  2017年   3171篇
  2016年   3054篇
  2015年   4738篇
  2014年   6050篇
  2013年   5362篇
  2012年   7900篇
  2011年   8668篇
  2010年   5227篇
  2009年   4069篇
  2008年   5525篇
  2007年   5808篇
  2006年   5680篇
  2005年   5935篇
  2004年   4008篇
  2003年   3561篇
  2002年   3180篇
  2001年   2575篇
  2000年   2774篇
  1999年   2880篇
  1998年   1645篇
  1997年   1551篇
  1996年   1363篇
  1995年   1205篇
  1994年   1013篇
  1993年   656篇
  1992年   1018篇
  1991年   819篇
  1990年   699篇
  1989年   608篇
  1988年   597篇
  1987年   533篇
  1986年   426篇
  1985年   330篇
  1984年   208篇
  1983年   159篇
  1982年   85篇
  1981年   98篇
  1980年   83篇
  1979年   115篇
  1978年   54篇
  1977年   56篇
  1975年   44篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
首先简要回顾了微电子机械系统技术研究进展,然后介绍了一种基于微处理器的消化道内按摩装置的基本结构,工作原理和特点。尤其详细介绍了采用MSP430F123微处理器产生周期脉冲,来控制整个按摩胶囊的供电。总的说来,消化道内按摩装置具有重要的临床应用价值和商业价值,开发消化道内按摩装置对我国生物医学工程产业和微电子机械系统产业的发展都有着积极和深远的意义。  相似文献   
992.
眉部运动的显微外科解剖学研究及其临床意义   总被引:8,自引:0,他引:8  
目的:为解决除皱术中眉毛上提效果欠佳,不够持久的问题。方法:对10例新鲜尸体进行了大体及显微解剖。结果:证实了额肌深面“滑动层”和“滑动间隙”的存在,观察了眉内侧2/3自皮肤向深面发出固定到眉嵴处的眉毛支持韧带,外侧上方的颞融合线和下方的眉限制韧带静态固定结构,上述结构决定了眉毛的形态;阐述了额肌、皱眉肌和降眉肌的眉毛动力机制,探讨了老年性外侧眉毛下垂主要由于外侧的滑动脂肪垫向下“疝出”所致。结论:通过破坏“滑动间隙”,切断颞融合线和眉限制韧带,切除外侧滑动脂肪垫,达到眉部上提的良好、持久效果。  相似文献   
993.
994.
995.
In Xenopus, localized factors begin to regionalize embryonic fates prior to the inductive interactions that occur during gastrulation. We previously reported that an animal-to-vegetal signal that occurs prior to gastrulation promotes primary spinal neuron fate in vegetal equatorial (C-tier) blastomere lineages. Herein we demonstrate that maternal mRNA encoding noggin is enriched in animal tiers and at low concentrations in the C-tier, suggesting that the neural fates of C-tier blastomeres may be responsive to early signaling from their neighboring cells. In support of this hypothesis, experimental alteration of the levels of Noggin from animal equatorial (B-tier) or BMP4 from vegetal (D-tier) blastomeres significantly affects the numbers of primary spinal neurons derived from their neighboring C-tier blastomeres. These effects are duplicated in blastomere explants isolated at cleavage stages and cultured in the absence of gastrulation interactions. Co-culture with animal blastomeres enhanced the expression of zygotic neural markers in C-tier blastomere explants, whereas co-culture with vegetal blastomeres repressed them. The expression of these markers in C-tier explants was promoted when Noggin was transiently added to the culture during cleavage/morula stages, and repressed with the transient addition of BMP4. Reduction of Noggin translation in B-tier blastomeres by antisense morpholino oligonucleotides significantly reduced the efficacy of neural marker induction in C-tier explants. These experiments indicate that early anti-BMP signaling from the animal hemisphere recruits vegetal equatorial cells into the neural precursor pool prior to interactions that occur during gastrulation.  相似文献   
996.
R T Huang  K Wahn  H D Klenk  R Rott 《Virology》1979,97(1):212-217
Envelope glycoproteins of virus N (an avian influenza virus) were artificially associated with liposomes, using octylglucoside as detergent which could be readily removed by dialysis. The prepared liposomes, about 0.1-1 μm in diameter, contained specific hemagglutinin and neuraminidase activities. The total amounts of proteins incorporated into liposomes were about the same irrespective of the lipid composition. Similarly, the neuraminidase activity of liposomes remained unchanged by altering lipids. However, the hemagglutinating and cell-adsorbing properties of liposomes varied greatly depending on the composition of lipids. As both lipid and protein components can be altered, the present system may be elaborated for the study of protein-lipid interactions and functions of viral membranes.  相似文献   
997.
Rh (Rhesus) proteins are homologues of ammonium transport (Amt) proteins. Physiological and structural evidence shows that Amt proteins are gas channels for NH(3), but the substrate of Rh proteins, be it CO2 as shown in green alga, or NH3/NH4+ as shown in mammalian cells, remains disputed. We assembled a large dataset generated of Rh and Amt to explore how Rh originated from and evolved independently of Amt relatives. Analysis of this rich data implies that Rh was split from Amt first to emerge in archaeal species. The Rh ancestor underwent divergence and duplication along speciation, leading to neofunctionalization and subfunctionalization of the Rh family. The characteristic organismal distribution of Rh vs. Amt reflects their early separation and subsequent independent evolution: they coexist in microbes and invertebrates but do not in fungi, vascular plants or vertebrates. Rh gene-duplication was prominent in vertebrates: while epithelial RhBG/RhCG displayed strong purifying selection, erythroid Rh30 and RhAG experienced different episodes of positive selection in each of which adaptive evolution occurred at certain time points and in a few codon sites. Mammalian Rh30 and RhAG were subject to particularly strong positive selection in some codon sites in the lineage from rodents to human. The grounds of this adaptive evolution may be driven by the necessity to increase the surface/volume ratio of biconcave erythrocytes for facilitative gas diffusion. Altogether, these results are consistent with Rh proteins not being the orthologue of Amt proteins but having gained the function for CO2/HCO3- transport, with important roles in systemic pH regulation.  相似文献   
998.
本文在大鼠内毒素休克模型上,观察了肝线粒体结构和功能与Ca^2+,Mg^2+含量变化的关系。结果发现:休克动物肝组织和线粒体的Ca^2+浓度升高,Mg^2+浓度下降与正常对照组相比有非常显著性差异;用图像分析仪定量分析显示线粒体结构明显受损,线粒体标志酶之一-琥珀酸脱氢酶(SDH)活性明显下降,本文认为组织和线粒体内Mg^2+/Ca^2+比值下降是休克细胞不可逆损伤重要因素之一。  相似文献   
999.
P物质在大鼠脑室管膜中定位分布的免疫组织化学研究   总被引:1,自引:0,他引:1  
黄卫  李海标 《解剖学报》1996,27(2):158-160
  相似文献   
1000.
将人工合成的恶性疟原虫杂合74肽抗原基因克隆到表达载体pWR450-1中,获得了重组质粒pWRC,将其先转化到减毒伤寒沙门氏菌LB5000修饰后,再转化到SL3261,得到重组减毒鼠伤寒沙门氏菌SL3261(pWRC)。pWRC在SL3261中以β-半乳糖苷酶-杂合多肽抗原C融合蛋白(GZ-C)形式表达,表达量约占菌体蛋白总量的11.3%.Westernblot及免疫双扩散显示GZ-C可与兔抗GZ-C抗原的免疫血清发生特异反应。GZ-C识别兔抗GZ-C及鼠抗恶性疟原虫抗血清的ELISA滴度分别为1:3200及1:5120。初步结果表明SL3261(pWRC)表达的GZ-C具有抗原性。连续传代SL3261(pWRC)未见质粒pWRC丢失及对宿主有明显的毒性。  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