全文获取类型
收费全文 | 4870篇 |
免费 | 542篇 |
国内免费 | 798篇 |
出版年
2024年 | 29篇 |
2023年 | 139篇 |
2022年 | 204篇 |
2021年 | 327篇 |
2020年 | 245篇 |
2019年 | 312篇 |
2018年 | 246篇 |
2017年 | 184篇 |
2016年 | 294篇 |
2015年 | 365篇 |
2014年 | 424篇 |
2013年 | 450篇 |
2012年 | 468篇 |
2011年 | 464篇 |
2010年 | 279篇 |
2009年 | 222篇 |
2008年 | 269篇 |
2007年 | 194篇 |
2006年 | 163篇 |
2005年 | 122篇 |
2004年 | 120篇 |
2003年 | 118篇 |
2002年 | 110篇 |
2001年 | 78篇 |
2000年 | 54篇 |
1999年 | 58篇 |
1998年 | 36篇 |
1997年 | 40篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有6210条查询结果,搜索用时 15 毫秒
21.
22.
Xiaohe Li Xiaoyang Ma Yang Miao Jianwei Zhang Buri Xi Wenqi Li Qianyi Zhang Li Chen Yue Yang Hongli Li Luqing Wei Honggang Zhou Cheng Yang 《Journal of cellular and molecular medicine》2023,27(3):422-434
Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease that seriously threatens the health of patients. The pathogenesis of IPF is still unclear, and there is a lack of effective therapeutic drugs. Myofibroblasts are the main effector cells of IPF, leading to excessive deposition of extracellular matrix (ECM) and promoting the progression of fibrosis. Inhibiting the excessive activation and relieving autophagy blockage of myofibroblasts is the key to treat IPF. PI3K/Akt/mTOR pathway plays a key regulatory role in promoting fibroblast activation and autophagy inhibition in lung fibrosis. Duvelisib is a PI3K inhibitor that can simultaneously inhibit the activities of PI3K-δ and PI3K-γ, and is mainly used for the treatment of relapsed/refractory chronic lymphocytic leukaemia (CLL) and small lymphocytic lymphoma tumour (SLL). In this study, we aimed to examine the effects of Duvelisib on pulmonary fibrosis. We used a mouse model of bleomycin-induced pulmonary fibrosis to evaluate the effects of Duvelisib on pulmonary fibrosis in vivo and further explored the potential pharmacological mechanisms of Duvelisib in lung fibroblasts in vitro. The in vivo experiments showed that Duvelisib significantly alleviated bleomycin-induced collagen deposition and improved pulmonary function. In vitro and in vivo pharmacological experiments showed that Duvelisib dose-dependently suppressed lung fibroblast activation and improved autophagy inhibition by inhibiting the phosphorylation of PI3K, Akt and mTOR. Our results indicate that Duvelisib can alleviate the severity of pulmonary fibrosis and provide potential drugs for the treatment of pulmonary fibrosis. 相似文献
23.
24.
Ying-Ying Li Xi Chen Jin-Xian Yang Qiang Chen Tie-Ying Song Jun-Qing Ge 《Journal of fish biology》2023,102(1):141-154
Eels are important aquaculture species for which an increasing number of reference genes are being identified and applied. In this study, five housekeeping genes [RPL7 (ribosomal protein L7), 18 S (18 S ribosomal RNA), EF1A (elongation factor 1α), ACTB (β-actin) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase)] were chosen to evaluate their reliability as reference genes for quantitative real-time PCR (qPCR) for the study of Anguilla anguilla. The expression of the selected genes in different eel tissues was determined using qPCR at different growth stages or upon challenge by Anguillid herpesvirus (AngHV), and the expression levels of these genes were then compared and evaluated using the geNorm and NormFinder algorithms. Then, RefFinder was used to comprehensively rank the examined housekeeping genes. Interestingly, the expression of the evaluated housekeeping genes exhibited tissue-dependent and treatment-dependent variations. In different growth periods A. anguilla tissues, the most stable genes were the following: ACTB in mucus; 18 S in skin and kidney; RPL7 in muscle, gill, intestine and brain; EF1A in heart and liver; and GAPDH in spleen. In contrast, in AngHV-challenged A. anguilla tissues, the most stable genes were the following: 18 S in mucus; RPL7 in skin, gill, heart, spleen, kidney and intestine; EF1A in muscle and liver; and ACTB in brain. Further comparison analysis indicated that the expression of RPL7 and EF1A was stable in multiple A. anguilla tissues in different growth periods and in eels challenged by AngHV. Nonetheless, the expression level of GAPDH in eel tissues was lower, and it was unstable in several tissues. These results indicated that the selection of reference genes for qPCR analysis in A. anguilla should be made in accordance with experimental parameters, and both RPL7 and EF1A could be used as reference genes for qPCR study of A. anguilla at different growth stages or upon challenge by AngHV. The reference genes identified in this study could improve the accuracy of qPCR data and facilitate further studies aimed at understanding the biology of eels. 相似文献
25.
26.
He Xi Jiang Yifan Chen Sumei Chen Fadi Chen Feng 《Journal of Plant Growth Regulation》2023,42(2):1144-1157
Journal of Plant Growth Regulation - Terpenoids are a class of structurally diverse natural products involved in various plant biological processes. Their primary function is believed to provide... 相似文献
27.
28.
囊萼紫草属与滇紫草属花粉形态比较研究 总被引:3,自引:1,他引:2
本文借助光学显微镜和扫描电镜研究了囊萼紫草属3种和滇紫草属12种植物的花粉形态。囊萼紫草属的花粉为哑铃形或茧形,中等大小,P/E比为1.6一1.67,三孔沟,内孔横长;具小刺状纹饰。滇紫草属的花粉为近长球形或近卵球形,P/E为l—1.23;三孔沟或三合沟孔,内孔一般纵长,具皱波状纹饰,在皱波上具密集的小瘤或微颗粒。从花粉形态的角度,本文支持把囊萼紫草属从滇紫草属(广义)中分离出来的观点。值得注意的是,在滇紫草属的花粉中首次观察到了一种比较少见且特化的花粉即单极三合沟孔的花粉。 相似文献
29.
薏苡胚乳传递细胞的超微结构 总被引:3,自引:1,他引:2
传粉后10 d,薏苡(Coix lacrym a-jobiL.)颖果基部胚乳最外层传递细胞具长而多的壁内突,第二层细胞的壁内突较第一层的短而少,均具瓣裂的细胞核、丰富的线粒体、粗糙内质网、核糖体、产生小泡的高尔基体及与壁内突质膜相连的、含深色物质的囊泡。线粒体分布于壁内突附近或其间。授粉后25 d,第一、二层细胞壁内突发达,几乎充满了细胞,但细胞器可见。第四层传递细胞具树枝状及网状的壁内突,大量线粒体、具质体膜的淀粉粒、脂体存在壁内突附近或壁内突的间隙内。高尔基体常见,仅见很少的片段内质网。第五层传递细胞具短的壁内突、较大的淀粉粒及许多小蛋白质体。两个时期的第一、二层细胞内均未观察到胞间连丝。授粉后25 d,第四层及以上的传递细胞的细胞壁和呈网状的壁内突均含有胞间连丝。还讨论了各种细胞器的作用及各层传递细胞的功能 相似文献
30.
将水稻(Oryza sativa L.)幼苗悬浮培养于含有羧基化多壁碳纳米管MWCNTs-COOH(0、2.5、5.0、10.0 mg/L)、50 mmol/L混合盐(1NaCl:9Na2SO4:9NaHCO3:1Na2CO3),以及MWCNTs-COOH+混合盐的复合溶液中,10 d后检测叶片生理生化指标变化,研究MWCNTs-COOH复合盐碱胁迫对水稻幼苗的毒性及生态风险。结果显示,与对照组相比,MWCNTs-COOH单一组诱导下水稻叶片O2·-和H2O2的产生不明显,而混合盐组和混合盐+MWCNTs-COOH复合组均诱导了O2·-和H2O2产物的大量累积。MWCNTs-COOH与混合盐复合后,加剧了O2·-和H2O2的累积,并有明显的浓度效应。活性氧(ROS)作为信号分子在一定程度上诱导了各处理组部分抗氧化酶(SOD、CAT、POD、APX)活性的升高;与混合盐组相比,低浓度混合盐+MWCNTs-COOH复合组中叶绿素a和胡萝卜素含量呈一定程度的升高;MWCNTs-COOH与混合盐复合后,抑制了叶片中可溶性糖(SS)和脯氨酸(Pro)的合成,致使相对电导率(REC)和丙二醛(MDA)含量显著升高。上述抗氧化酶活性及叶绿素a和胡萝卜素含量的升高对缓解水稻叶片氧化损伤、维持正常的光合电子传递及对过剩光能的热耗散是有益的,是水稻幼苗重要的防御机制。本研究表明MWCNTs-COOH单一处理在一定程度上诱导了水稻叶片的氧化胁迫和应激响应,与混合盐复合后加剧了叶片的氧化胁迫和应激损伤。 相似文献