全文获取类型
收费全文 | 226664篇 |
免费 | 21697篇 |
国内免费 | 14889篇 |
专业分类
耳鼻咽喉 | 2035篇 |
儿科学 | 2488篇 |
妇产科学 | 2780篇 |
基础医学 | 25973篇 |
口腔科学 | 4055篇 |
临床医学 | 28830篇 |
内科学 | 32285篇 |
皮肤病学 | 2674篇 |
神经病学 | 11553篇 |
特种医学 | 8257篇 |
外国民族医学 | 109篇 |
外科学 | 23549篇 |
综合类 | 39469篇 |
现状与发展 | 49篇 |
一般理论 | 22篇 |
预防医学 | 15934篇 |
眼科学 | 5629篇 |
药学 | 24494篇 |
233篇 | |
中国医学 | 14349篇 |
肿瘤学 | 18483篇 |
出版年
2024年 | 875篇 |
2023年 | 3477篇 |
2022年 | 8908篇 |
2021年 | 11433篇 |
2020年 | 8765篇 |
2019年 | 7379篇 |
2018年 | 7836篇 |
2017年 | 7390篇 |
2016年 | 6895篇 |
2015年 | 10513篇 |
2014年 | 12821篇 |
2013年 | 12330篇 |
2012年 | 17793篇 |
2011年 | 19381篇 |
2010年 | 13032篇 |
2009年 | 10387篇 |
2008年 | 13115篇 |
2007年 | 12476篇 |
2006年 | 11936篇 |
2005年 | 11223篇 |
2004年 | 7725篇 |
2003年 | 7173篇 |
2002年 | 6096篇 |
2001年 | 4881篇 |
2000年 | 4716篇 |
1999年 | 4457篇 |
1998年 | 2662篇 |
1997年 | 2690篇 |
1996年 | 2047篇 |
1995年 | 1955篇 |
1994年 | 1721篇 |
1993年 | 1042篇 |
1992年 | 1368篇 |
1991年 | 1231篇 |
1990年 | 964篇 |
1989年 | 903篇 |
1988年 | 815篇 |
1987年 | 661篇 |
1986年 | 496篇 |
1985年 | 430篇 |
1984年 | 215篇 |
1983年 | 172篇 |
1982年 | 101篇 |
1981年 | 127篇 |
1980年 | 90篇 |
1979年 | 112篇 |
1978年 | 57篇 |
1977年 | 58篇 |
1976年 | 54篇 |
1974年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
本文通过Percoll梯度离心法分离获得大鼠中性粒细胞(PMNS)后,采用PMNS与玻璃珠粘附的模型,通过给予Dex及糖皮质激素受体(GR)阻断剂Mifepristone(RU_(38486))研究大鼠PMNS粘附过程中GR的作用。结果显示,Dex可以明显抑制PMNS的粘附,其作用随着Dex浓度的增大而增强;单纯给予不同浓度的RU_(38486)未发现明显的PMNS粘附增强,说明RU_(38486)本身对离体的PMNS粘附没有明显的作用;若同时给予Dex和RU_(38486),则Dex抑制PMNS粘附的作用逐渐减小,直至完全逆转。该结果强烈提示:糖皮质激素(GC)具有抑制PMNS粘附的作用,其作用是通过GR介导的,当GR被阻断时,这一抑制作用减弱,甚至消失。 相似文献
992.
Kazunaga Agematsu Tetsuji Kobata Feng-Chun Yang Takayuki Nakazawa Keitaro Fukushima Masashi Kitahara Tetsuo Mori Kanji Sugita Chikao Morimoto Atsushi Komiyama 《European journal of immunology》1995,25(10):2825-2829
CD27 is a T cell activation antigen expressed on a majority of peripheral blood T cells. CD27 is also expressed on a subpopulation of human B cells, and it is reported that CD27+ B cells secrete both IgG and IgM. CD70, a ligand for CD27, is expressed on activated T and B cells, suggesting an interaction between T and B cells via CD27/CD70 ligation. Here, we analyze B cell immunoglobulin synthesis using a CD70 transfectant and present functional data showing that B cells secrete large amounts of IgG and IgM as a result of the CD27/CD70 interaction. A flow cytometric analysis showed that CD27 expression was increased and CD70 was expressed on tonsillar and peripheral blood B cells after activation with Staphylococcus aureus Cowan strain (SAC) plus interleukin (IL-2). In addition, the proliferation of B cells was enhanced mildly by the addition of CD70 transfectant, and its proliferation was blocked by anti-CD70 mAb. More importantly, the CD70 transfectant enhanced IgG and IgM production by purified B cells greatly in the presence of SAC plus IL-2. The enhancement was completely blocked by the addition of either anti-CD70 mAb or anti-CD27 mAb. Strongly suggesting that the interaction of CD27 with its ligand, CD70, on B cells plays an important role in B cell growth and differentiation to produce IgG and IgM. 相似文献
993.
一体化假肢是以聚合物为材料从接受腔到假腿一体成型的新型下肢假肢,它比传统型假肢更经济、美观、轻便,具有较大的应用前景。目前的相关研究主要集中在设计与制作及少量的临床研究方面。由于一体化假肢与传统型假肢在结构上的差异,有必要对其进行应力分析。本研究的目的是开展内骨架一体化假肢的生物力学研究,本研究基于内骨架一体化小腿假肢的真实几何构型,建立三维有限元模型,计算该模型在模拟Heel OH步态时相的载荷作用下的应力分布;在保持该模型的几何形状不变的情况下,建立了三个不同壁面厚度的一体化小腿假肢的有限元模型,分析壁面厚度对一体化小腿假肢应力分布的影响;通过分别赋予模型四种不同高分子聚合物的材料力学特性值,分析不同材料的一体化假肢的应力分布特点;分别对模型施加与正常步态的五个典型时相对应的载荷,分析一体化小腿假肢在各步态时相的应力分布特点。本研究结果对一体化假肢设计有指导价值。 相似文献
994.
995.
Thymocyte-thymocyte interaction for efficient positive selection and maturation of CD4 T cells 总被引:2,自引:0,他引:2
Despite numerous reports on MHC class II expression by T cells from a wide spectrum of mammalian species including humans, the biological relevance of this phenomenon has never been tested with appropriately designed animal models. To address this issue, we developed mouse models in which immature thymocytes are the only positively selecting antigen-presenting cells in the thymus. In these mice, CD4+ T cells were generated with the appropriate maturation phenotype and showed a diverse repertoire of TCR Vbetas. The CD4+ T cells were functionally competent, mediating effective allogeneic responses that involved polyclonal TCR Vbetas. These results suggest that the thymocyte-thymocyte (T-T) interaction operates as an independent pathway for CD4+ T cell selection in the thymi of species with MHC II-positive thymocytes. This T-T interaction appears to be the basis for the generation of donor MHC-restricted CD4+ T cells in xenogeneic hosts. 相似文献
996.
Identification of testis development and spermatogenesis-related genes in human and mouse testes using cDNA arrays 总被引:12,自引:0,他引:12
Sha J Zhou Z Li J Yin L Yang H Hu G Luo M Chan HC Zhou K;Spermatogenesis study group 《Molecular human reproduction》2002,8(6):511-517
We have constructed cDNA microarrays from the human testis large insert cDNA library, containing 9216 genes, together with several housekeeping genes. The cDNA microarrays were used to identify gene expression differences between human fetal and adult testes. Of >8700 hybridized clones, 731 exhibited significant differential expression characteristics. About 7500 genes were identified when the same cDNA microarrays were used for hybridization with cDNA probes from mouse testis, with 256 genes having significant differential expression between the age of 1-4 weeks. Among these genes, 101 were identified as critically related to testis development and possibly to spermatogenesis since they were found in both human and mouse testes, and expressed differentially at different stages of testis development. Of the 101 development-related genes, 59 full-length cDNAs have been sequenced previously, while the full-length cDNAs of the other 42 genes have not been published. We have obtained 11 full-length sequences of the 42 genes and deposited them in the GenBank. The conserved testis development-related genes found in both human and mouse testes may include genes that are likely to be involved in testicular functions, especially spermatogenesis, thus providing a basis for further functional characterization of the genes in mouse models. 相似文献
997.
We develop an integrated model of isolated rat arterial resistance vessel (RV), which can simulate its major property of myogenic response. The vascular smooth muscle cell is an important component of the wall of this vessel, and serves as a vasomotor organ providing the active tension generation that underlies the myogenic response of the wall to stretch. In the previous study, we focused on the development of a smooth muscle cell model that can mimic the strain-sensing and force-generating features of the myogenic mechanism. In the current model, we embed this cell model in a larger vessel wall configuration, and couple the time course of cellular contractile activation to macroscopic changes in vessel diameter. The integrated model is used to mimic published pressure-vessel diameter data obtained from isolated RVs that are mounted in a hydraulic test apparatus. The model provides biophysically based insights into the myogenic mechanism as it responds to changes in transmural pressure, in the presence and absence of Ca2+ blockers applied to the bathing fluid.It mimics measured data very well and provides a model that is able to link events at subcellular level to macroscopic changes in vessel diameter. The model initiates a mechanistic approach to investigate myogenic response, which has not been taken previously by any other models. 相似文献
998.
目的探讨CTLA4Ig基因转染猪皮治疗中小面积浅Ⅱ度烧伤创面的临床疗效与安全性。方法将自2005年5月~2007年5月我院收治的浅Ⅱ度烧伤患者60例随机分为2组,每组30例。基因转染猪皮治疗组:伤后创面简单清创,去除水疱,用复温后的基因转染猪皮覆盖创面。对照组:创面简单清创,除颜面、会阴部位创面外,均予包扎治疗,保留水疱皮,其后常规换药治疗。结果基因转染猪皮治疗组创面愈合时间5~10d,对照组为8~14d。基因转染猪皮治疗组疼痛明显减轻,未观察到寒战、高热等全身不良反应及局部排斥反应。两组均未出现瘢痕,但对照组部分病例出现色素改变。结论应用基因转染猪皮治疗中小面积浅Ⅱ度烧伤创面能明显缩短创面愈合时间,能明显减轻创面疼痛,减少换药次数,预防色素改变及瘢痕形成。 相似文献
999.
1000.
为获取有功能的IV型II类反式激活因子基因 (CIITA IV ) ,诱导肿瘤细胞表达MHCII类分子 ,从IFN γ刺激的THP 1细胞中以RT PCR获得CIITA IV ,将其连接到pGEMT easy载体。对所构建的pcDNA3 1 CIITA IV型表达载体进行反复测序后发现 ,所获得的CIITA IV基因存在结构变异 ,在 2 87位插入了 3个核苷酸TAG ,使 2 86 2 88位的AAG改变成为ATAGAG(2 86 2 90 ) ,并引起其他 8个座位核苷酸 (及推导的氨基酸残基 )发生改变。将表达载体转入原先不表达MHCII类分子的HeLa细胞中 ,检测到所获得的IV型CIITA变异体具有诱导人II类分子HLA DR表达的能力。空载体和CIITA IV基因导入的HeLa细胞中 ,DR阳性细胞百分率分别为 0 0 1 %和 37 6 4 %。该基因已从GenBank得到登录号 ,表明这是一个具有诱导HLA DR分子表达功能的IV型CIITA新基因。 相似文献