全文获取类型
收费全文 | 203113篇 |
免费 | 18828篇 |
国内免费 | 11816篇 |
专业分类
耳鼻咽喉 | 1684篇 |
儿科学 | 3118篇 |
妇产科学 | 1348篇 |
基础医学 | 13155篇 |
口腔科学 | 3917篇 |
临床医学 | 25444篇 |
内科学 | 18990篇 |
皮肤病学 | 2257篇 |
神经病学 | 4806篇 |
特种医学 | 6864篇 |
外国民族医学 | 21篇 |
外科学 | 17411篇 |
综合类 | 54095篇 |
现状与发展 | 56篇 |
一般理论 | 1篇 |
预防医学 | 23711篇 |
眼科学 | 2775篇 |
药学 | 24890篇 |
275篇 | |
中国医学 | 18744篇 |
肿瘤学 | 10195篇 |
出版年
2024年 | 887篇 |
2023年 | 2290篇 |
2022年 | 5935篇 |
2021年 | 7403篇 |
2020年 | 6593篇 |
2019年 | 4128篇 |
2018年 | 4073篇 |
2017年 | 5491篇 |
2016年 | 4300篇 |
2015年 | 7818篇 |
2014年 | 10419篇 |
2013年 | 12254篇 |
2012年 | 17902篇 |
2011年 | 19075篇 |
2010年 | 17226篇 |
2009年 | 15631篇 |
2008年 | 16030篇 |
2007年 | 15661篇 |
2006年 | 14251篇 |
2005年 | 11514篇 |
2004年 | 8396篇 |
2003年 | 6949篇 |
2002年 | 5425篇 |
2001年 | 4734篇 |
2000年 | 3542篇 |
1999年 | 1693篇 |
1998年 | 704篇 |
1997年 | 704篇 |
1996年 | 535篇 |
1995年 | 419篇 |
1994年 | 433篇 |
1993年 | 272篇 |
1992年 | 186篇 |
1991年 | 151篇 |
1990年 | 144篇 |
1989年 | 95篇 |
1988年 | 74篇 |
1987年 | 87篇 |
1986年 | 59篇 |
1985年 | 47篇 |
1984年 | 22篇 |
1983年 | 30篇 |
1982年 | 29篇 |
1980年 | 7篇 |
1959年 | 15篇 |
1958年 | 19篇 |
1957年 | 14篇 |
1956年 | 7篇 |
1955年 | 7篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Ping Xu Shuichi Hashimoto Hiroyuki Miyazaki Koushi Asabe Sachiko Shiraishi K. Sueishi 《Virchows Archiv : an international journal of pathology》1998,432(1):17-25
Morphometric analyses of the immunohistochemical expression of the Clara cell secretory 10-kDa protein (CC10) and surfactant
apoproteins A and B (SP-A and -B) were carried out on the developing bronchi and bronchioles of human fetuses and neonates.
We analysed the ratio of the number of CC10-positive cells per subepithelial length of the bronchial or bronchiolar basement
membrane and found that both the bronchial and the bronchiolar population of CC10-positive cells was significantly higher
than that of either SP-A or SP-B. In addition, CC10 was found to be distributed mainly in the bronchiole. CC10-positive cells
began to be recognized in the late pseudoglandular phase (15 weeks of gestation) and thereafter gradually increased in the
canalicular and terminal sac phases, which correspond to the active development period of the acini or peripheral airways.
The earliest expression of SP-A was also noted at 15 weeks of gestation, but its positive epithelial cells were present mainly
in the larger bronchi. Double immunohistochemical staining for CC10 and SP-A revealed that the CC10-positive cells lining
both the bronchi and bronchioles were different from the SP-A-positive cells. This finding suggests that CC10-positive cells
are functionally and developmentally heterogeneous in both fetal and neonatal lungs in humans
Received: 22 May 1997 / Accepted: 21 July 1997 相似文献
92.
Xiu Ming Wang Paul I. Terasaki George W. Rankin Jr. David Chia Hui Ping Zhong Steven Hardy 《Human immunology》1993,37(4)
We present a microtest for cell-mediated immunity, based on the use of the Tarasaki tray and calcein AM vital dye. The number of target cells needed has been reduced to 500 per test with a corresponding tenfold reduction in the number of effector cells needed. Results were read at the rate of 1 second per test using a fluorimeter attached to a microscope. Each reaction was also confirmed visually with the use of ethidium bromide as a counterstain for dead cells. The calcein AM dye used to stain the living cells was shown to have a low spontaneous leakage rate—less than 15% in 4 hours at 37°C. Dilutions of targets stained by calcein AM had a linear relationship with measured fluorescence values. NK cells, LAKs, and CTLs were readily detectable by this microtest. Quantitation of killing and kinetic analysis was readily performed with this test system. A significant positive correlation to 51Cr-release results was found. We conclude that the microtest should find wide application in studies of cell-mediated immunity. 相似文献
93.
刘平 《生物医学工程学杂志》1992,9(1):61-70
本系统是为自动测试人体韧带或类似组织的动态力学特性试验而研制的。在试验时,受控的加载过程和数据采集过程同时进行。系统向韧带试件提供一个快速的匀速可控的拉伸载荷,模拟人体剧烈运动的实况,同时实时采集力和变形的数据。系统还提供对所采集数据的分析手段,从而得到力、变形、应力、应变、弹性模量和变形能等参数之间的关系,并可以图形和文字形式输出。系统亦可将各数据文件转换为其它应用软件包可接受的形式,以便利用标准商品软件包的数据和图象处理能力。系统采用菜单提示的人机对话方式进行监控。 相似文献
94.
肝素酶和碱性成纤维细胞生长因子与非小细胞肺癌转移和预后的关系 总被引:6,自引:0,他引:6
目的 探讨肝素酶(heparanase)和碱性成纤维细胞生长因子(bFGF)在人非小细胞肺癌(NSCLC)组织中表达的临床意义及其与肺癌转移和预后的关系。方法 采用免疫组织化学、原位杂交和Western blot方法,检测115例人NSCLC石蜡切片和45例新鲜肺癌及对应癌旁正常组织中肝素酶和bFGF的表达情况。采用χ^2检验、t检验、生存曲线和Cox比例风险回归等方法分析肝素酶和bFGF分别表达及共表达的意义。结果 免疫组织化学染色证实肝素酶(91/115)和bFGF(89/115)主要表达在癌细胞质和(或)细胞膜中,在正常肺泡上皮和支气管上皮中则呈阴性表达。Western blot也证实肝素酶在肺癌中的表达明显增高(P=0.041)。统计分析结果显示:肝素酶和bFGF的表达具有明显的一致性(P:0.0001),二者单独表达和共表达均与肺癌的分期、血管侵袭、淋巴结转移、微血管密度和预后有关,其中,二者共表达时与分期和微血管密度的相关性更显著;另外,bFGF还与肺癌的分化程度有关。多因素分析结果显示,肺癌的分化程度、血管浸润、淋巴结转移和bFGF的表达可以作为判断肺癌预后的危险因素,但肝素酶不是影响预后的独立因素。结论 肝素酶和bFGF均与肺癌的转移、血管生成和预后密切相关。 相似文献
95.
为了考察海藻酸钙/聚组氨酸微胶囊的毒性特征,我们利用MTT比色法和小鼠尾静脉注射法,分别考察了该微胶囊的细胞毒性和急性全身毒性。结果表明:微胶囊浓度≤1.0mg/mL时,材料对L929细胞生长无明显抑制作用;微胶囊浸提液即使在高浸提比(10.0mg/mL)下,浸提产物也无细胞毒性作用。急性全身毒性试验结果显示:微胶囊浸提液不引起急性全身毒性反应,表明微胶囊浸提液无有毒的沥滤物和降解产物产生。说明海藻酸钙/聚组氨酸微胶囊无明显毒性。 相似文献
96.
97.
对于科学研究工作来说,时间分辨率和空间分辨率都是十分重要的,在设计相应的图像处理系统时必须两者兼顾。对于生命科学及工业等领域而言,希望图像处理系统不仅有较高的时间分辨率,还要有较高的空间分辨率。本文提出一种利用多部CCD数码相机、采用移相法获取高分辨牢和高摄录帧率的技术,此技术可应用于普通CCD数码相机组成的复合摄录系统。 相似文献
98.
Shyh Ren Chiang Hung Jen Tang Ping Chin Chang Kuo Chen Cheng Wen Chien Ko Chung Hua Chen Yin Ching Chuang 《Journal of microbiology, immunology, and infection》2007,40(2):123-133
BACKGROUND AND PURPOSE: Vibrio vulnificus causes primary bacteremia and necrotizing wound infection, leading to high morbidity and mortality in humans. This study aimed to evaluate the antimicrobial effect of cefotaxime and minocycline on proinflammatory cytokine levels in a murine model of V. vulnificus infection. METHODS: We investigated the dynamics of proinflammatory cytokines and their modulation by antimicrobial agents using a murine model of V. vulnificus infection. The change in cytokine levels was followed over a time course to identify the antimicrobial activity of the drugs against V. vulnificus. BALB/c female mice were challenged with an intraperitoneal infection using a clinical invasive isolate of Vv05191, and their cytokine levels were assayed over various time points. RESULTS: Serum levels of tumor necrosis factor-alpha, interleukin (IL)-1 beta, and IL-6 post-infection were found to be inoculum dose-dependent and positively correlated to the subsequent fatality rate in the infected mice. With an inoculum of 6.6 x 10(6) colony-forming units and intraperitoneal administration of cefotaxime, minocycline, or both, the serum and peritoneal fluid cytokine levels increased and then declined gradually. Comparison of the 3 antimicrobial regimens revealed that the magnitude of reduction in cytokine levels was greatest in mice treated with cefotaxime-minocycline combination. Moreover, the peritoneal fluid cytokine level in the combination group was significantly lower than that in the groups treated with minocycline or cefotaxime alone. CONCLUSIONS: The current results support the superiority of the combination therapy in treating invasive V. vulnificus infections. 相似文献
99.
目的:临床评价增殖性瘢痕的颜色需要定量测量.本实验主要研究增殖性瘢痕色度的测量方法,实现瘢痕颜色的定量测量,为临床诊治提供量化依据.材料与方法:采用以光电积分式测量原理设计的色彩分析仪对增殖性瘢痕患者19人,共65个测试点按不同部位分为四组进行色度测量,并与正常组对照.用CIE-XYZ色度标准表达测量值,配合色度图直接观察瘢痕的疗效.结果:增殖性瘢痕各部位组的色度坐标值与相应的对照组比较均有显著性差异(P<0.05).结论:本实验的测量方法是有效的,能准确、定量反映增殖性瘢痕颜色的变化.可用量化指标总结、分析、报告治疗结果. 相似文献
100.
H. Ping Ting-Beall Florence M. Burgess Laszlo Dux Anthony Martonosi 《Journal of muscle research and cell motility》1987,8(3):252-259
Summary Two distinct forms of Ca2+-ATPase crystals have been analysed in sarcoplasmic reticulum (SR) membranes. The E1-type crystals, induced by Ca2+ or lanthanide ions, consist of single chains of ATPase monomers, and the E2-type crystals, induced by vanadate ions, consist of dimer chains. Using improved freeze-fracture techniques we have obtained high-resolution images of complementary surface replicas of SR membranes containing these crystal forms. In E1 crystals, the concave fracture (P) faces display obliquely oriented rows of intramembrane particles (IMPs) spaced at - 6–7 nm along both crystal axes, while the convex fracture (E) faces show corresponding rows of pits. In E2 crystals, regular arrays of oblique parallel ridges with spacing of - 10.5–11 nm appear on the P-faces and complementary grooves or furrows on the E-faces. In many instances the ridges break up into elongated particles repeating every 5.5 nm. When the direction of the shadow is almost parallel to the axis of the ridges, these 9.5 nm particles can be resolved into two domains, which represent intramembranous contacts between the two monomers of the two adjacent dimer chains. Complementary grooves on the E-faces can also be resolved into rows of pits complementary to the particles of the ridges on the P-faces. In the control SR membranes, randomly dispersed IMPs and corresponding pits are observed on the P- and E-faces, respectively. The data suggest that transport of Ca2+ involves significant structural changes of the enzyme molecule, reflected in the ATPase-ATPase interactions both on the cytoplasmic surface and in the lipid bilayer. 相似文献