全文获取类型
收费全文 | 2234篇 |
免费 | 213篇 |
国内免费 | 234篇 |
专业分类
2681篇 |
出版年
2024年 | 13篇 |
2023年 | 51篇 |
2022年 | 98篇 |
2021年 | 155篇 |
2020年 | 110篇 |
2019年 | 112篇 |
2018年 | 120篇 |
2017年 | 90篇 |
2016年 | 127篇 |
2015年 | 175篇 |
2014年 | 201篇 |
2013年 | 183篇 |
2012年 | 196篇 |
2011年 | 188篇 |
2010年 | 98篇 |
2009年 | 107篇 |
2008年 | 120篇 |
2007年 | 104篇 |
2006年 | 87篇 |
2005年 | 89篇 |
2004年 | 65篇 |
2003年 | 38篇 |
2002年 | 36篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 2篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有2681条查询结果,搜索用时 0 毫秒
151.
以拟南芥为材料,在红光和蓝光下对PRRs(pseudo-response regulators)突变体prr5p、rr7、prr9和toc1及其野生型的下胚轴表型进行比较观察,并采用实时定量PCR方法对突变体中光信号通路相关基因ZTL(zeitlupe)和CO(constans)的节律表达进行分析.结果表明:在红光下,prr5和toc1的下胚轴长度比野生型显著增长,在蓝光下,prr7p、rr9和toc1较野生型短,表明突变体降低了拟南芥对红光的敏感性,却增强了对蓝光的敏感性.红光和蓝光下,PRRs突变体中ZTL和CO的mRNA节律表达与野生型明显不同,其中红光下prr5和prr7、蓝光下prr5和toc1中的ZTLmRNA的表达显著下降且节律消失;红光下prr7和prr9以及蓝光下prr5突变体中的COmRNA表现基本无节律.因此推测,PRRs与ZTL的相互作用很可能在红光和蓝光信号转导途径中发挥作用,且PRRs基因极有可能参与了红光和蓝光对CO的调控. 相似文献
152.
该研究探讨氰酸盐(cyanate)诱导肾小管上皮细胞氧化应激损伤和促进肾纤维化的作用。氰酸盐作用HK-2肾小管上皮细胞后, CCK8法检测其对细胞活力的影响;倒置显微镜观察细胞形态的改变; DCFH-DA法检测细胞ROS水平;细胞免疫荧光和Western blot分别检测E-cadherin、Fibronectin、α-SMA的表达; Western blot检测TGF-β的表达水平。结果显示, 2 mmol/L氰酸盐明显下调HK-2细胞的活力(P<0.05),细胞形态变为长梭形。氰酸盐作用24 h后, HK-2细胞内ROS水平呈浓度依赖性升高。免疫荧光和Western blot结果均显示,氰酸盐作用24 h后, HK-2的Fibronectin、α-SMA表达升高, E-cadherin表达下降; TGF-β的表达水平随氰酸盐浓度升高而上调(P<0.05)。以上结果表明,氰酸盐诱导肾小管上皮细胞产生过量ROS,上调TGF-β水平促进细胞上皮–间充质细胞转化(epithelia-mesenchymal transition, EMT)。 相似文献
153.
Ren‐Tao Zeng Xue‐Yun Dong Xing Fang Niao Yang Zhi‐Ran Shi Zhi‐Guo Zhuo Yun‐Heng Shen Wei‐Dong Zhang 《化学与生物多样性》2017,14(2)
Three new sesquiterpenoids, 4α‐hydroxyeudesm‐11(13)‐en‐12‐yl 3‐methylbutanoate ( 1 ), diaspanolide E ( 2 ), and (13α)‐germacra‐1(10),4‐dien‐12,8α‐olid‐15‐oic acid ( 3 ), along with eight known sesquiterpenoids ( 4 – 11 ), were isolated from the aerial parts of Ainsliaea henryi. The chemical structures of compounds 1 – 3 were elucidated by spectroscopic analysis (1D‐, 2D‐NMR, MS and HR/MS). All isolates were evaluated for their inhibitory activities against nitric oxide (NO) production in lipopolysaccharide‐induced RAW264.7 macrophage cells. Compound 10 exhibited significantly inhibition against NO release with an IC50 value of 6.54 ± 0.16 μm . Also, all isolated compounds were tested for cytotoxicity against three human tumor cell lines A549, MGC803, and HCT116, among which compound 5 significantly inhibited the proliferation of MGC803 cell lines with an IC50 value of 2.2 ± 0.2 μm . 相似文献
154.
Electrically Contacted Bienzyme‐Functionalized Mesoporous Carbon Nanoparticle Electrodes: Applications for the Development of Dual Amperometric Biosensors and Multifuel‐Driven Biofuel Cells 下载免费PDF全文
The capping of electron relay units in mesoporous carbon nanoparticles (MPC NPs) by crosslinking of different enzymes on MPC NPs matrices leads to integrated electrically contacted bienzyme electrodes acting as dual biosensors or as functional bienzyme anodes and cathodes for biofuel cells. The capping of ferrocene methanol and methylene blue in MPC NPs by the crosslinking of glucose oxidase (GOx) and horseradish peroxidase (HRP) yields a functional sensing electrode for both glucose and H2O2, which also acts as a bienzyme cascaded system for the indirect detection of glucose. A MPC NP matrix, loaded with ferrocene methanol and capped by GOx/lactate oxidase (LOx), is implemented for the oxidation and detection of both glucose and lactate. Similarly, MPC NPs, loaded with 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid), are capped with bilirubin oxidase (BOD) and catalase (Cat), to yield a bienzyme O2 reduction cathode. A biofuel cell that uses the bienzyme GOx/LOx anode and the BOD/Cat cathode, glucose and/or lactate as fuels, and O2 and/or H2O2 as oxidizers is assembled, revealing a power efficiency of ≈90 μW cm?2 in the presence of the two fuels. The study demonstrates that multienzyme MPC NP electrodes may improve the performance of biofuel cells by oxidizing mixtures of fuels in biomass. 相似文献
155.
156.
Xiong H Ran Y Xing J Yang X Li Y Chen Z 《Journal of biochemistry and molecular biology》2005,38(4):414-419
The production of recombinant antibodies has been generally recognized as time-consuming and labor-intensive. The aim of our study is to construct mammalian expression vectors containing the cDNA encoding the human constant regions and murine variable regions to massively and cost-effectively produce full-length chimeric antibodies. Unique restriction sites flanking the Ig variable region were designed to allow for the replacement of variable regions generated by PCR. Western blot analysis of the chimeric antibodies revealed that the expressed products were of the predicted size, structure and specificity. The usefulness of the vectors was confirmed by construction of human-mouse chimeric antibody-HCAb which secretes murine antibody against the human colorectal cancer. Selected in medium containing gradually increasing methotrexate (MTX), clones with increased expression of the product gene can be efficiently generated. The secretion of recombinant chimeric antibody-HCAb yielded 30 pg cell(-1) day(-1) at 10(-6 )M MTX. With this high-level expression from pools, the convenient and rapid production of over 100 milligram amounts per liter of recombinant antibodies may be achieved, which indicates the significant roles of pYR-GCEVH and pYR-GCEVL in the production of chimeric antibodies. 相似文献
157.
158.
159.
Zhai Wenjie Zhou Xiuman Zhai Mingxia Li Wanqiong Ran Yunhui Sun Yixuan Du Jiangfeng Zhao Wenshan Xing Lingxiao Qi Yuanming Gao Yanfeng 《中国科学:生命科学英文版》2021,64(4):548-562
The interaction of PD-1/PD-L1 allows tumor cells to escape from immune surveillance. Clinical success of the antibody drugs has proven that blockade of PD-1/PD-L1 pathway is a promising strategy for cancer immunotherapy. Here, we developed a cyclic peptide C8 by using Ph.D.-C7 C phage display technology. C8 showed high binding affinity with h PD-1 and could effectively interfere the interaction of PD-1/PD-L1. Furthermore, C8 could stimulate CD8+T cell activation in human peripheral blood mononuclear cells(PBMCs). We also observed that C8 could suppress tumor growth in CT26 and B16-OVA, as well as anti-PD-1 antibody resistant B16 mouse model. CD8+T cells infiltration significantly increased in tumor microenvironment, and IFN-γ secretion by CD8+T cells in draining lymph nodes also increased. Simultaneously, we exploited T cells depletion models and confirmed that C8 exerted anti-tumor effects via activating CD8+T cells dependent manner. The interaction model of C8 with h PD-1 was simulated and confirmed by alanine scanning. In conclusion, C8 shows anti-tumor capability by blockade of PD-1/PD-L1 interaction, and C8 may provide an alternative candidate for cancer immunotherapy. 相似文献
160.
Ran Chao Li Yu Ma Xufa Xie Yadong Xie Mingxu Zhang Yuting Zhou Wei Yang Yalin Zhang Zhen Zhou Li Wei Kaijian Zhou Zhigang 《中国科学:生命科学英文版》2021,64(9):1437-1448
Viral diseases cause serious economic loss in farmed animals industry. However, the efficacy of remedies for viral infection in farmed animals is limited, and treatment strategies are generally lacking for aquatic animals. Interactions of commensal microbiota and viral infection have been studied in recent years, demonstrating a third player in the interaction between hosts and viruses. Here, we discuss recent developments in the research of interactions between commensal bacteria and viral infection,including both promotion and inhibition effect of commensal bacteria on viral pathogenesis, as well as the impact of viral infection on commensal microbiota. The antiviral effect of commensal bacteria is mostly achieved through priming or regulation of the host immune responses, involving differential microbial components and host signaling pathways, and gives rise to various antiviral probiotics. Moreover, we summarize studies related to the interaction between commensal bacteria and viral infection in farmed animals, including pigs, chickens, fish and invertebrate species. Further studies in this area will deepen our understanding of antiviral immunity of farmed animals in the context of commensal microbiota, and promote the development of novel strategies for treatment of viral diseases in farmed animals. 相似文献