首页 | 官方网站   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   214215篇
  免费   20520篇
  国内免费   15236篇
医药卫生   249971篇
  2024年   244篇
  2023年   3159篇
  2022年   4925篇
  2021年   10832篇
  2020年   8560篇
  2019年   7557篇
  2018年   8070篇
  2017年   7108篇
  2016年   6680篇
  2015年   10272篇
  2014年   12580篇
  2013年   10717篇
  2012年   16037篇
  2011年   17990篇
  2010年   10516篇
  2009年   8199篇
  2008年   11133篇
  2007年   11109篇
  2006年   11237篇
  2005年   11327篇
  2004年   7014篇
  2003年   6623篇
  2002年   5494篇
  2001年   4941篇
  2000年   5357篇
  1999年   5689篇
  1998年   3512篇
  1997年   3483篇
  1996年   2754篇
  1995年   2610篇
  1994年   2145篇
  1993年   1378篇
  1992年   1892篇
  1991年   1596篇
  1990年   1293篇
  1989年   1092篇
  1988年   1014篇
  1987年   857篇
  1986年   716篇
  1985年   525篇
  1984年   335篇
  1983年   242篇
  1982年   149篇
  1981年   145篇
  1980年   111篇
  1979年   142篇
  1978年   47篇
  1977年   53篇
  1975年   57篇
  1974年   56篇
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
91.
安息香为安息香科白花树Styrax tonkinensis (Pierre) Craib ex Hart.的干燥树脂,主要化学成分为香脂酸类和三萜类物质,及少数木脂素类物质,其中香脂酸类化合物是其主要活性成分。安息香主要药理活性有抗炎解热、抗肿瘤、血脑屏障保护等。本文对安息香药材的化学成分和药理作用进行了综述,并从多角度分析预测了安息香可能的质量标志物,为安息香药材的质量控制、合理开发与利用提供参考。  相似文献   
92.
孤独症谱系障碍(autism spectrum disorders,ASD)是一种起始于婴幼儿时期的神经发育障 碍性疾病,除社会交往障碍、认知缺失、重复刻板行为等核心症状外,还存在明显的多感官异常,其中 ASD患者疼痛异常会做出重复性的自我伤害行为,这种障碍不仅给患者也对其家庭造成了较为严重的 伤害,引起家庭和社会的广泛关注。对患儿疼痛敏感程度及影响疼痛敏感性的原理及机制进行深入研 究,不仅可以减轻患儿的痛苦体验,也能够为ASD患儿治疗方面提供新的思路。现对近年来在ASD 人 群中流行病学、临床实验、遗传学、影像学及ASD 动物模型的痛觉敏感程度及可能机制的研究进行综述, 在今后的研究中,可以尝试探索优化干预方案,为进一步推广临床提供理论依据。  相似文献   
93.
Background:Gastrointestinal complications and malnutrition are common problems that affect postoperative rehabilitation and survival of patients with esophageal cancer. Evidence has shown that probiotics have a positive effect on improving gastrointestinal complications and nutritional status of patients with esophageal cancer after surgery, but there is a lack of prospective studies on this topic. We designed this prospective randomized controlled trial to evaluate the effects of probiotics on gastrointestinal complications and nutritional status in patients with postoperative esophageal cancer.Methods:This is a prospective, randomized, double-blind, placebo-controlled trial. It was approved by the Clinical Research Ethics Committee of our hospital. 192 patients will be randomly divided into probiotics group and the placebo group in a 1:1 ratio. After operation, probiotics and placebo will be given orally for 8 weeks. The indexes of nutritional status and incidence of digestive tract complications will be recorded and the data will be analyzed by SPSS 18.0 software.Discussion:This study will evaluate the effect of probiotics on gastrointestinal complications and nutritional status of postoperative patients with esophageal cancer. The results of this study will provide clinical basis for the use of probiotics in postoperative treatment of esophageal cancer.Trial registration:OSF Registration number: D DOI 10.17605/OSF.IO/QHW86  相似文献   
94.
目的 利用筛选出十堰的天师栗中高多态性SSR位点评价天师栗种质资源的遗传多样性,结合有效药用成分含量,构建十堰地区天师栗核心种质库。方法 收集十堰地区114份天师栗种质资源,以七叶树基因组为参考,采用荧光毛细管电泳筛选出高多态性SSR位点,对天师栗种质资源进行遗传多样性分析。利用HPLC测定不同种质干燥娑罗子中七叶皂苷的含量。采用最小距离逐步聚类取样策略(LDSS),根据遗传多样性保留程度初步筛选出核心种质,并对该核心种质与原始种质的遗传多样性参数进行T检验,选择与原种质差异不显著的核心种质为最佳核心种质。结果 筛选出13对高多态性SSR分子标记,遗传多样性评价结果表明十堰地区天师栗种质资源遗传多样性较高,遗传分化较小,存在着较大的基因流,114份种质资源未分为不同的亚群,周家坝和辽叶居群间具有较近的遗传亲缘关系,且周家坝居群娑罗子中的七叶皂苷A及七叶皂苷B含量普遍较高。最终筛选出的核心种质共23份,占总种质资源的20.17%,其中周家坝12份样本、辽叶6份样本、普龄5份样本。结论 将SSR分子标记与主要有效药用成分结合,采用LDSS取样策略构建十堰地区天师栗种质资源核心种质库的方法具有可行性,能够有效的保存与管理天师栗种质资源,也为当地天师栗品种改良、新品种选育研究等提供了研究基础。  相似文献   
95.
miR-30c has been acknowledged as a tumor suppressor in various human cancers, such as ovarian cancer, gastric cancer, and prostate cancer. However, the role of miR-30c in glioblastoma (GBM) needs to be investigated. In our study, we found that the expression of miR-30c was significantly downregulated in GBM tissues and cell lines. We found that overexpression of miR-30c inhibited cellular proliferation of GBM cells in vitro and in vivo. More GBM cells were arrested in the G0 phase after miR-30c overexpression. Moreover, we showed that miR-30c overexpression suppressed the migration and invasion of GBM cells. Mechanistically, we found that SOX9 was a direct target of miR-30c in GBM cells. Overexpression of miR-30c inhibited the mRNA and protein levels of SOX9 in GBM cells. Moreover, there was a negative correlation between the expression of miR-30c and SOX9 in GBM tissues. Finally, we showed that restoration of SOX9 in GBM cells reversed the proliferation, migration, and invasion of GBM cells transfected with miR-30c mimic. Collectively, our results demonstrated that miR-30c suppressed the proliferation, migration, and invasion of GBM cells via targeting SOX9.  相似文献   
96.
97.
1. To investigate Genkwa Flos hepatotoxicity, a cell metabolomics strategy combined with serum pharmacology was performed on human HL-7702 liver cells in this study.

2. Firstly, cell viability and biochemical indicators were determined and the cell morphology was observed to confirm the cell injury and develop a cell hepatotoxicity model. Then, with the help of cell metabolomics based on UPLC-MS, the Genkwa Flos group samples were completely separated from the blank group samples in the score plots and seven upregulated as well as two down-regulated putative biomarkers in the loading plot were identified and confirmed. Besides, two signal molecules and four enzymes involved in biosynthesis pathway of lysophosphatidylcholine and the sphingosine kinase/sphingosine-1-phosphate pathway were determined to investigate the relationship between Genkwa Flos hepatotoxicity and these two classic pathways. Finally, the metabolic pathways related to specific biomarkers and two classic metabolic pathways were analyzed to explain the possible mechanism of Genkwa Flos hepatotoxicity.

3. Based on the results, lipid peroxidation and oxidative stress, phospholipase A2/lysophosphatidylcholine pathway, the disturbance of sphingosine-1-phosphate metabolic profile centered on sphingosine kinase/sphingosine-1-phosphate pathway and fatty acid metabolism might be critical participators in the progression of liver injury induced by Genkwa Flos.  相似文献   

98.
Programmed death ligand 1(PD-L1) mediated immune escape play important roles in the development of cancer. The gene polymorphism of PD-L1, in particular rs4143815 C?>?G, has been associated with the cancer risks, but with conflicting results. Therefore, this meta-analysis was aimed to assess the association between rs4143815 C?>?G and cancer susceptibility. A systematic literature search was performed to select the studies and the pooled odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the strength of association. Eleven eligible studies containing 3711 cases and 3704 controls were enrolled in the meta-analysis. The results suggested that there is a strong association between rs4143815 C?>?G and the cancer risks (G vs. C: OR?=?1.386, 95% CI: 1.132–1.696, p?=?0.002; GG vs. CG?+?CC: OR?=?1.843 95% CI: 1.300–2.613, p?=?0.002; GG?+?CG vs. CC: OR?=?1.280, 95% CI: 1.040–1.576, p?=?0.020). Subgroup analysis based on cancer type suggested that PD-L1 rs4143815 C?>?G might increase the susceptibility to gastric cancer (G vs. C: OR?=?1.842, 95% CI: 1.403–2.418, p?<?0.001) and bladder cancer (G vs. C: OR?=?2.015, 95% CI: 1.556–2.608, p?<?0.001), and genotype GG carriers of PD-L1 rs4143815 C?>?G might have higher risks of HCC (GG vs. CG?+?CC: OR?=?2.226 95% CI: 1.562–3.172, p?<?0.001). PD-L1 rs4143815 C?>?G might confer an increased cancer risk, indicating this SNP may contribute to the pathogenesis of cancer and might be used as a potential biomarker to predict the susceptibility to cancer.  相似文献   
99.
Gastric cancer, one of the most common disease, has become a major public health problem worldwide. Cisplatin (DDP) has been a widely used drug for the treatment of cancer, also usually applied in gastric cancer in clinic. However, the side effects including toxicity and drug-resistance restricted the usage of DDP in clinic, so we prepared a DDP-complexed hydrogel (DDP-Gel) and investigated its efficacy in gastric cancer. For in vivo studies, MKN45-Luc cells were injected into BLAB/C node mice subcutaneously to establish gastric cancer with orthotopically grown tumors. Mice bearing tumors were treated with normal saline, DDP and DDP-Gel. Body weight and survival condition were observed and recorded. The treatment efficacy in vivo was detected by luciferase imaging and histological evaluation was performed by H&E staining of different organs. Additionally, normal ICR mice were treated with different doses of DDP/DDP-Gel to calculate their LD50 in vivo. The results showed that DDP-Gel prolonged survival time and ameliorated body weight changes of mice bearing tumors. DDP-Gel exhibited higher efficacy to inhibit tumor growth and metastasis, compared to DDP. Besides, LD50 of DDP-Gel was 166.0?mg/kg, 13.2 folds higher than DDP. As a conclusion, DDP-Gel showed a more effective and safer function than DDP in gastric cancer, which indicating that DDP-Gel might be a novel strategy for gastric cancer therapy.  相似文献   
100.
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-23

京公网安备 11010802026262号