全文获取类型
收费全文 | 23834篇 |
免费 | 2265篇 |
国内免费 | 1186篇 |
专业分类
耳鼻咽喉 | 379篇 |
儿科学 | 305篇 |
妇产科学 | 406篇 |
基础医学 | 5442篇 |
口腔科学 | 741篇 |
临床医学 | 1450篇 |
内科学 | 3429篇 |
皮肤病学 | 435篇 |
神经病学 | 1424篇 |
特种医学 | 505篇 |
外科学 | 2713篇 |
综合类 | 3300篇 |
预防医学 | 940篇 |
眼科学 | 381篇 |
药学 | 2012篇 |
3篇 | |
中国医学 | 556篇 |
肿瘤学 | 2864篇 |
出版年
2023年 | 163篇 |
2022年 | 383篇 |
2021年 | 601篇 |
2020年 | 484篇 |
2019年 | 375篇 |
2018年 | 506篇 |
2017年 | 585篇 |
2016年 | 833篇 |
2015年 | 961篇 |
2014年 | 1338篇 |
2013年 | 1525篇 |
2012年 | 1446篇 |
2011年 | 1635篇 |
2010年 | 1383篇 |
2009年 | 1440篇 |
2008年 | 1523篇 |
2007年 | 1549篇 |
2006年 | 1471篇 |
2005年 | 1298篇 |
2004年 | 1033篇 |
2003年 | 958篇 |
2002年 | 743篇 |
2001年 | 652篇 |
2000年 | 566篇 |
1999年 | 478篇 |
1998年 | 359篇 |
1997年 | 327篇 |
1996年 | 280篇 |
1995年 | 277篇 |
1994年 | 254篇 |
1993年 | 224篇 |
1992年 | 188篇 |
1991年 | 143篇 |
1990年 | 142篇 |
1989年 | 148篇 |
1988年 | 131篇 |
1987年 | 110篇 |
1986年 | 81篇 |
1985年 | 88篇 |
1984年 | 91篇 |
1983年 | 47篇 |
1982年 | 71篇 |
1981年 | 65篇 |
1980年 | 59篇 |
1979年 | 47篇 |
1978年 | 44篇 |
1977年 | 28篇 |
1976年 | 26篇 |
1973年 | 19篇 |
1972年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Objective To study the altered radiobiological effect of simulative intensity-modulated radiotherapy (SIMR) in cultured human nasopharyngeal carcinoma (NPC) cells and the related mechanism. Methods Single cell suspension of exponentially growing CNE-2 cells, a poor differentiated NPC cell line, was seeded and cultured for 12 hours, then the cells were irradiated in two different models by 6 MV X-ray beams at 3 Gy/min. In single fraction irradiation (SFR) model, cells were irradiated a single fraction of 0, 2, 4, 6 or 8 Gy within 0 to 3 minutes. In S1MR model, cells were irradiated 0, 2, 4, 6 or 8 Gy in 5 frac-tions with interval of 8.0-8.5 minutes between. Clonogenic assay was performed to determine the radiosen-sitivity. Cellular apoptosis was measured by flow cytometry. RT-PCR was used to detect mRNA expressions of Bax and Bcl-2, Respectively. Results Compared with SFR group, the survival fraction in SIMR group was higher at all the dose levels. The values of α, β, D0 and Dq were higher in SIMR group than in SFR group. At dose levels of 2 Gy, 4 Gy and 6 Gy, The early and late apoptotic cells in SIMR group were lower than in SFR group (21.20%: 15.89%, F=18.51, P=0.020;13.00%: 10.20, F=15.67, P=0.040).The mRNA expression of Bax was upregulated in a dose-dependent manner in the both groups. Compared with SFR group, the mRNA expression of Bax in SIMR group was lower at all the dose levels (Mean value of 76.75% : 62.50%, F =36.57, P =0.000). Bcl-2 mRNA expression at every dose level had no significant difference between the two groups (Mean value of 29.25% : 29.75%, F=0.74, P=0.800). Conclusions Prolonged delivery time in SIMR model can decrease the radiobiological effects. 相似文献
102.
黄连素对缺血再灌注心肌细胞损伤的保护作用 总被引:28,自引:1,他引:27
目的 研究黄连素对新生大鼠心肌细胞缺血再灌注损伤的保护作用。方法 取体外培养的新生大鼠心肌细胞于缺氧 2 4h复氧 1h造成缺血再灌注 ( I/ R)模型 ,观察细胞损伤情况 ;并将黄连素以 1.5× 10 - 6 m ol/ L、1.5× 10 - 5m ol/ L、1.5× 10 - 4 mol/ L 三种浓度分别加入培养基中 ,预处理 2 4h后 ,再置于上述缺氧复氧环境中培养 ,检测以上不同条件下细胞上清液中的乳酸脱氢酶 ( L DH)、丙二醛 ( MDA)、超氧化物歧化酶 ( SOD)含量 ,并检测各组细胞的凋亡率。结果 与正常对照组相比 ,缺血及再灌组细胞上清液中 L DH、MDA含量明显升高 ( P<0 .0 1) ,SOD活力则显著降低 ( P<0 .0 1) ,缺血组和再灌组凋亡率均升高明显 ( P<0 .0 1)。而用黄连素预处理后缺血及再灌组的 L DH、MDA显著低于用药前 ( P<0 .0 1) ,SOD则高于单纯缺血和再灌组 ( P<0 .0 1) ,上述作用在本实验黄连素浓度为 1.5× 10 - 6 m ol/ L~ 1.5× 10 - 4 mol/ L 范围内 ,随浓度升高而更加明显。特别是用黄连素 1.5× 10 - 5mol/ L 浓度预处理后 ,缺血组和再灌组的细胞凋亡率分别是 14.4%和 2 0 % ,分别与用药前 ( 17.4%和 41% )比较有显著性差异 ( P<0 .0 1)。结论 黄连素对缺血再灌心肌细胞有保护作用 ,其作用与浓度有一定依赖关系 相似文献
103.
104.
We describe a new method that uses straightforward physics to apply force to substrate-attached cells. In this method, collagen-coated
magnetic ferric oxide beads attach to the dorsal surface of cells via receptors of the integrin family, and a magnetic field
gradient is applied to produce a force. In this paper we present a complete characterization of the method in a configuration
that is easy to use, in which a permanent magnet provides a fairly uniform gradient over a relatively large area. This allows
a fairly uniform average force that can be controlled in magnitude, direction, and duration to be applied to a large number
of cells. We show how to determine the applied force per cell by measuring the force per unit volume of magnetic bead, the
distribution of bead diameters, and the distribution of beads per cell. We also show how to calculate the force per unit volume
of bead in a three-dimensional region near the permanent magnet on the basis of field measurements, and present results for
three of the magnets. An upward force applied to fibroblasts by this method produces a measurable time-dependent increase
in attachment of cytoskeletal actin filaments to the force application points, and an increase in actin cross-linking. This
is accompanied by an actin-dependent retraction of the force-induced upward movement of the dorsal surface of the cells.
Received: 27 February 1997 / Received after revision: 10 August 1997 / Accepted: 1 September 1997 相似文献
105.
Y. Naito Y. Ohtawara S. Kageyama M. Nakano A. Ichiyama M. Fujita K. Suzuki K. Kawabe I. Kino 《Urological research》1997,25(1):59-65
Cell culture models of calcium phosphate renal stone formation were established using the MDCK cell line. Renal microliths were detected within pseudocysts in three-dimensional soft agar cultures, and were also observed in the basal region of cells lining the cell sheet, and immediately beneath domes or blisters in monolayers and collagen gel cultures. Light and scanning electron microscopy indicated that these microliths had a similar lamellated and spherical appearance to those in humans. These microliths were first detected microscopically after 21 days of culture, and were found to be composed of calcium phosphate by X-ray and microinfrared spectroscopic analyses. These culture models may provide a powerful new tool to study the pathogenesis of renal stone diseases and/or calcium phosphate stone formation in humans and animals. 相似文献
106.
本文报告了小牛胸腺肽(CTP)治疗乙肝患者50例(慢迁肝23例,慢活肝16例,重症肝炎11例)和HBsAg携带者10例的结果,CTP对消除或减轻临床症状和体征,改善肝功能具有明显的疗效,对慢迁肝,慢活肝和重症肝炎的治疗效果基本相同,各组间无显著性差异。对HBV血清学指标无重要改变,对HBsAg携带者疗效不侍。并对剂景、疗程与疗效的关系进行了讨论。 相似文献
107.
本文报道了应用细胞培养方法研究炭素纤维人工食管材料对细胞的毒性作用。实验结果表明,该材料对于体外培养细胞的形态、细胞的增殖等方面均无不良影响及毒性作用,从而为炭素纤维人工食管材料的应用提供了细胞学根据。 相似文献
108.
109.
骨髓间充质干细胞的分离培养及生物学特性研究 总被引:3,自引:0,他引:3
目的:通过体外细胞的培养方法将骨髓间充质干细胞由骨髓血中分离出来并加以纯化,进一步在体外培养条件下研究其增殖及生长特征,从而为探讨后续利用组织工程学方法修复肌肉骨骼系统组织缺损的可能性提供实验基础。方法:从骨髓血中提取间充质干细胞,体外培养扩增,再以相差显微镜、电镜观察并绘制生长曲线。结果:(1)通过离体培养,可以使体内环境下低丰度的骨髓间充质干细胞实现数目扩增。(2)体外培养条件下骨髓间充质干细胞具有成纤维细胞的生长特性。(3)体外单层培养条件下贴壁生长的骨髓间充质干细胞会出现“返祖现象”。(4)骨髓间充质干细胞内细胞器与其生物活性变化相一致。结论:骨髓间充质干细胞体外培养成功为今后利用自体间充质干细胞通过组织工程学方法修复肌肉骨骼系统的组织缺损提供功能细胞奠定了基础。 相似文献
110.
目的 研究p38MAPK基因对大鼠胶质瘤细胞C6生长周期的影响。方法 利用脂质体将p38MAPK基因导入C6细胞中,用免疫细胞化学染色检测其在转染前后的表达,用HE染色、流式细胞仪、TUNEL等研究其对细胞形态、粘着状况和生长周期的影响。结果 pCMV5-p38MAPK组P38MAPK蛋白表达阳性,细胞形态发生变化,贴壁性降低,G1期百分比增加,而S期和G2期百分比减低,并出现凋亡峰。结论 p38MAPK基因可影响C6细胞的生长周期,并诱导C6细胞凋亡。 相似文献