全文获取类型
收费全文 | 30393篇 |
免费 | 3271篇 |
国内免费 | 2009篇 |
专业分类
耳鼻咽喉 | 319篇 |
儿科学 | 560篇 |
妇产科学 | 556篇 |
基础医学 | 2779篇 |
口腔科学 | 448篇 |
临床医学 | 3519篇 |
内科学 | 3888篇 |
皮肤病学 | 328篇 |
神经病学 | 1409篇 |
特种医学 | 1071篇 |
外国民族医学 | 11篇 |
外科学 | 3566篇 |
综合类 | 6046篇 |
现状与发展 | 6篇 |
一般理论 | 2篇 |
预防医学 | 2778篇 |
眼科学 | 506篇 |
药学 | 3305篇 |
36篇 | |
中国医学 | 2185篇 |
肿瘤学 | 2355篇 |
出版年
2024年 | 157篇 |
2023年 | 581篇 |
2022年 | 1372篇 |
2021年 | 1801篇 |
2020年 | 1392篇 |
2019年 | 1099篇 |
2018年 | 1108篇 |
2017年 | 1138篇 |
2016年 | 998篇 |
2015年 | 1586篇 |
2014年 | 1875篇 |
2013年 | 2065篇 |
2012年 | 2721篇 |
2011年 | 2731篇 |
2010年 | 2040篇 |
2009年 | 1591篇 |
2008年 | 1796篇 |
2007年 | 1597篇 |
2006年 | 1444篇 |
2005年 | 1252篇 |
2004年 | 889篇 |
2003年 | 827篇 |
2002年 | 718篇 |
2001年 | 565篇 |
2000年 | 454篇 |
1999年 | 341篇 |
1998年 | 142篇 |
1997年 | 175篇 |
1996年 | 118篇 |
1995年 | 109篇 |
1994年 | 111篇 |
1993年 | 56篇 |
1992年 | 110篇 |
1991年 | 106篇 |
1990年 | 90篇 |
1989年 | 75篇 |
1988年 | 80篇 |
1987年 | 65篇 |
1986年 | 57篇 |
1985年 | 37篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1971年 | 8篇 |
1970年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Meyer PE Jessen ME Patel JB Chao RY Malloy CR Meyer DM 《The Annals of thoracic surgery》2000,70(1):264-269
BACKGROUND: Lung transplantation requires a period of storage and ischemia; we examined the largely unknown effects of that period on intermediary metabolism. METHODS: Two groups of isolated rat lung blocks (n = 16 each) were flushed with Euro-Collins solution and harvested. The lung blocks were immediately ventilated and either perfused for 30 minutes with an erythrocyte-based solution containing carbon 13 labeled substrates (group 1) or stored for 6 hours at 1 degree C and then reperfused (group 2). Half of each group was reperfused at a physiologic Po2 the other half at high Po2. Analysis of carbon 13 isotopomers was performed to determine substrate utilization through aerobic pathways in lung tissue. RESULTS: Lungs from both groups oxidized all major substrates. The contribution of fatty acids to acetylcoenzyme acid oxidized in the citric acid cycle was significantly higher in group 2 than in group 1 (31.3% +/- 2.2% versus 22.0% +/- 2.1%, p < 0.05). Perfusate Po2 did not affect substrate preference. Gas exchange was worse in stored lungs. CONCLUSIONS: After a period of hypothermic ischemia and storage, substrate preference in lung tissue exhibits a switch towards fatty acids. As fatty acid oxidation occurring after ischemia is deleterious in other organs, strategies to inhibit this process in stored lungs may warrant further investigation. 相似文献
62.
近十年日本植物多糖提取纯化技术的发明专利 总被引:4,自引:0,他引:4
通过专利检索,介绍近十年来日本在植物多糖提取纯化方面的发明专利,简介多糖提取纯化的新工艺以及多糖的新资源和多糖的新用途。 相似文献
63.
背景与目的:颅叫管瘤为难治性肿瘤,其预后不良,复发机制尚不清楚。本研究检测颅Ⅱ阏管瘤组织中微血管密度(microvascular density,MVD)及血管内皮生长因子vascular endothelial growth factor,VEGF表达.分析其与肿瘤预后等生物学行为的关系。方法:采取前瞻性队列研究方案,经纳入、排除标准筛选卅颅咽管釉质上皮型肿瘤32例、鳞形乳头瘤型肿瘤31例,平均随访843个月,收集原发及复发患者的肿瘤组织标本,应用单克隆抗体CD34、VEGF抗体检测肿瘤组织MVD及VEGF蛋白表达,计算机辅助成像系统对其作出定量分析,分析其与肿瘤复发等生物学行为的关系。结果:VEGF蛋白、MVD计数在颅咽管瘤队列复发组、非复发组间不具有显著性差异(P〉0.05),而在颅咽管瘤不同病理类型间差异则具有显著性(P〈0.05)。结论:VEGF蛋白、MVD计数与肿瘤复发无关,不能预测颅咽管瘤复发的危险性,但可为了解肿瘤的同有侵袭性行为提供参考。 相似文献
64.
目的 探讨COX-2基因与基质金属蛋白酶在星形细胞瘤中的表达及二者相关性。方法 用原位杂交的方法检测星形细胞瘤组织中COX-2 mRNA的表达;用Ultrasensitive S-P法(链霉素抗生物素蛋白-过氧化物免疫组化染色)检测同等标本中基质金属蛋白酶-2和基质金属蛋白酶-9蛋白的表达;并将COX-2 mRNA与基质金属蛋白酶的表达作相关性分析。结果 COX-2 mRNA及MMP2、MMP9在星形细胞瘤中高度表达,表达阳性率分别为62.69%、56.70%和58.20%;COX-2 mRNA与MMP2和MMP9均有正相线性关系,Pearson积距相关系数分别为0.260、0.347,P<0.05。结论 COX-2基因和基质金属蛋白酶在星形细胞瘤组织中的表达密切相关,说明它在星形细胞瘤向周围组织侵袭中起重要作用。 相似文献
65.
Elias JJ Nagao M Chu YH Carbone JJ Lennox DW Chao EY 《Clinical orthopaedics and related research》2000,(370):250-258
Intraoperative proximal femur fractures are a significant concern during noncemented total hip arthroplasty. The current study was performed to investigate the hypothesis that broaching the femur and inserting the stem without using mallet applied impact loads will reduce the risk of intraoperative fracture. Rosette strain gauges were applied to the medial and anteromedial cortex of six human anatomic specimen femurs to compare the strain distribution for broaching and stem insertion. Eight additional femurs were used to compare the strain distribution for stem insertion using impact loading and constant rate stem insertion. For the impact loading stem insertions, the soft tissues surrounding the femur were modeled. Constant rate stem insertions were performed using a mechanical testing machine. The largest strains measured at the medial and anteromedial sites primarily were aligned with the femur hoop axis. The largest strain magnitude, orientation, and sign (tensile or compressive) varied widely among femurs. The stem insertion strains were significantly larger than the broaching strains (two-way analysis of variance with replication). The impact stem insertion strains were not significantly different from the constant rate stem insertion strains. The results indicate that the femur geometry and material properties have a greater influence on the strain distribution than does the implantation technique. 相似文献
66.
目的:应用金磁微粒标记蛋白质技术,建立可目视化蛋白质芯片检测体系,比较金磁微粒和胶体金标记蛋白质技术应用于蛋白质芯片检测效果的优劣。方法:将人IgG点制于环氧基修饰的玻片上,分别与金磁微粒和胶体金标记的羊抗人IgG温育,银染显色,肉眼观察并用普通扫描仪记录结果。结果:基于金磁微粒的蛋白质芯片人IgG最佳点样浓度为0.2mg/ml,37℃温育2h,银染10~15min,检测结果信噪比高;基于胶体金的蛋白质芯片人IgG最佳点样浓度为0.1mg/ml,37℃温育1h,银染15~20min.检测结果信噪比高。结论:金磁微粒标记蛋白质技术应用于蛋白质芯片的检测,具有和胶体金一致的可目视化检测效果。且其标记技术简单,标记的蛋白质可定量。 相似文献
67.
皮肤对紫外线红斑反应敏感度的季节因素研究 总被引:1,自引:0,他引:1
目的:比较春夏秋冬4个季节不同部位皮肤对紫外线红斑反应的敏感性,了解皮肤紫外线红斑反应敏感度的影响因素。方法:春夏秋冬4个季节分别在40名受试者的前臂伸侧(曝光部位)和上臂屈侧(非曝光部位)使用中波紫外线(UVB)(181.44、140.40、88.56、56.16mJ)及长波紫外线(UVA)+UVB03.49J/364.80mJ,9.91J/273.60mJ,6.62J/190.00mJ,4.45J/125.40mJ)西各4个剂量进行照射。照射前及照射后10min、24h、48h、第7天、第14天进行临床评分和使用Mexameter(皮肤黑素和血红素测定仪)进行检测,计算皮肤红斑指数改变率(EIR)。结果:①非曝光部位红斑反应强度在春季显著大于其他季节(P〈0.05),与非曝光部位的四季皮肤基础色素情况完全一致,且具有相关性(P〈0.05)。②春季和其他3个季节间曝光部位红斑反应强度差异均有统计学意义(P〈0.05)。结论:四季中春季对紫外线红斑反应的敏感性最高。表皮中黑素含量会影响皮肤对紫外线的敏感性。 相似文献
68.
69.
Xue Gong Xinyue Zhang Dang Liu Chao Yang Rong Zhang Zhibo Xiao Wenzhi Chen Jinyun Chen 《The Journal of international medical research》2022,50(5)
ObjectiveTo evaluate the effect of different levels of physician experience on the high-intensity focused ultrasound (HIFU) ablation of uterine fibroids and to provide a reference for the use of non-perfused volume ratio (NPVR) standards during training.MethodsThis prospective multicentre study enrolled patients with uterine fibroids. The effect of the physician’s level of experience on the outcomes under different NPVR standards and the learning curve of six centres without HIFU experience were analysed. The impact of patient demographic and clinical characteristics were also evaluated.ResultsA total of 1352 patients from 20 centres were included in the study. The median NPVRs were 92.00%, 88.10% and 92.86% in the no experience group, inexperienced group and experienced group, respectively. Posterior wall fibroids, lateral wall fibroids and fundus fibroids were inversely correlated with NPVR, while experienced physicians were positively correlated with NPVR. With NPVR ≥ 70% and NPVR ≥ 80% standards, physicians in the no experience group completed the learning curve on the 11th and 16th procedure, respectively. Physicians under a standard of an NPVR ≥ 90% did not complete the learning curve.ConclusionsNPVR ≥ 80% is a standard that is worth using for HIFU treatment of uterine fibroids. 相似文献
70.
Graphene is one of the most promising two-dimensional nanomaterials with broad applications in many fields. However, the variations and fluctuations in the material and geometrical properties are challenging issues that require more concern. In order to quantify uncertainty and analyze the impacts of uncertainty, a stochastic finite element model (SFEM) is proposed to propagate uncertainty for carbon atomic interactions under resonant vibration. Compared with the conventional truss or beam finite element models, both carbon atoms and carbon covalent bonds are considered by introducing plane elements. In addition, the determined values of the material and geometrical parameters are expanded into the related interval ranges with uniform probability density distributions. Based on the SFEM, the uncertainty propagation is performed by the Monte Carlo stochastic sampling process, and the resonant frequencies of graphene are provided by finite element computation. Furthermore, the correlation coefficients of characteristic parameters are computed based on the database of SFEM. The vibration modes of graphene with the extreme geometrical values are also provided and analyzed. According to the computed results, the minimum and maximum values of the first resonant frequency are 0.2131 and 16.894 THz, respectively, and the variance is 2.5899 THz. The proposed SFEM is an effective method to propagate uncertainty and analyze the impacts of uncertainty in the carbon atomic interactions of graphene. The work in this paper provides an important supplement to the atomic interaction modeling in nanomaterials. 相似文献