全文获取类型
收费全文 | 4528篇 |
免费 | 567篇 |
国内免费 | 685篇 |
出版年
2024年 | 16篇 |
2023年 | 53篇 |
2022年 | 131篇 |
2021年 | 228篇 |
2020年 | 211篇 |
2019年 | 234篇 |
2018年 | 217篇 |
2017年 | 203篇 |
2016年 | 213篇 |
2015年 | 290篇 |
2014年 | 363篇 |
2013年 | 336篇 |
2012年 | 417篇 |
2011年 | 349篇 |
2010年 | 221篇 |
2009年 | 200篇 |
2008年 | 246篇 |
2007年 | 226篇 |
2006年 | 170篇 |
2005年 | 144篇 |
2004年 | 203篇 |
2003年 | 211篇 |
2002年 | 255篇 |
2001年 | 194篇 |
2000年 | 118篇 |
1999年 | 90篇 |
1998年 | 57篇 |
1997年 | 29篇 |
1996年 | 30篇 |
1995年 | 19篇 |
1994年 | 25篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有5780条查询结果,搜索用时 31 毫秒
171.
Wensu Yuan Carlos F. Ibez Zhi Lin 《Biological reviews of the Cambridge Philosophical Society》2019,94(4):1282-1293
The death domain (DD) is a globular protein motif with a signature feature of an all‐helical Greek‐key motif. It is a primary mediator of a variety of biological activities, including apoptosis, cell survival and cytoskeletal changes, which are related to many neurodegenerative diseases, neurotrauma, and cancers. DDs exist in a wide range of signalling proteins including p75 neurotrophin receptor (p75NTR), a member of the tumour necrosis factor receptor superfamily. The specific signalling mediated by p75NTR in a given cell depends on the type of ligand engaging the extracellular domain and the recruitment of cytosolic interactors to the intracellular domain, especially the DD, of the receptor. In solution, the p75NTR‐DDs mainly form a symmetric non‐covalent homodimer. In response to extracellular signals, conformational changes in the p75NTR extracellular domain (ECD) propagate to the p75NTR‐DD through the disulfide‐bonded transmembrane domain (TMD) and destabilize the p75NTR‐DD homodimer, leading to protomer separation and exposure of binding sites on the DD surface. In this review, we focus on recent advances in the study of the structural mechanism of p75NTR‐DD signalling through recruitment of diverse intracellular interactors for the regulation and control of diverse functional outputs. 相似文献
172.
Ajith Anand Emily Wu Zhi Li Sue TeRonde Maren Arling Brian Lenderts Jasdeep S. Mutti William Gordon‐Kamm Todd J. Jones Nicholas Doane Chilcoat 《Plant biotechnology journal》2019,17(8):1636-1645
An efficient Agrobacterium‐mediated site‐specific integration (SSI) technology using the flipase/flipase recognition target (FLP/FRT) system in elite maize inbred lines is described. The system allows precise integration of a single copy of a donor DNA flanked by heterologous FRT sites into a predefined recombinant target line (RTL) containing the corresponding heterologous FRT sites. A promoter‐trap system consisting of a pre‐integrated promoter followed by an FRT site enables efficient selection of events. The efficiency of this system is dependent on several factors including Agrobacterium tumefaciens strain, expression of morphogenic genes Babyboom (Bbm) and Wuschel2 (Wus2) and choice of heterologous FRT pairs. Of the Agrobacterium strains tested, strain AGL1 resulted in higher transformation frequency than strain LBA4404 THY‐ (0.27% vs. 0.05%; per cent of infected embryos producing events). The addition of morphogenic genes increased transformation frequency (2.65% in AGL1; 0.65% in LBA4404 THY‐). Following further optimization, including the choice of FRT pairs, a method was developed that achieved 19%–22.5% transformation frequency. Importantly, >50% of T0 transformants contain the desired full‐length site‐specific insertion. The frequencies reported here establish a new benchmark for generating targeted quality events compatible with commercial product development. 相似文献
173.
Ning Jiang Chao Zhang Jun‐Ying Liu Zhi‐Hong Guo Zong‐Ying Zhang Cheng‐Gui Han Ying Wang 《Plant biotechnology journal》2019,17(7):1302-1315
Many plant viruses with monopartite or bipartite genomes have been developed as efficient expression vectors of foreign recombinant proteins. Nonetheless, due to lack of multiple insertion sites in these plant viruses, it is still a big challenge to simultaneously express multiple foreign proteins in single cells. The genome of Beet necrotic yellow vein virus (BNYVV) offers an attractive system for expression of multiple foreign proteins owning to a multipartite genome composed of five positive‐stranded RNAs. Here, we have established a BNYVV full‐length infectious cDNA clone under the control of the Cauliflower mosaic virus 35S promoter. We further developed a set of BNYVV‐based vectors that permit efficient expression of four recombinant proteins, including some large proteins with lengths up to 880 amino acids in the model plant Nicotiana benthamiana and native host sugar beet plants. These vectors can be used to investigate the subcellular co‐localization of multiple proteins in leaf, root and stem tissues of systemically infected plants. Moreover, the BNYVV‐based vectors were used to deliver NbPDS guide RNAs for genome editing in transgenic plants expressing Cas9, which induced a photobleached phenotype in systemically infected leaves. Collectively, the BNYVV‐based vectors will facilitate genomic research and expression of multiple proteins, in sugar beet and related crop plants. 相似文献
174.
Long Xing‐yu Gong Jiang‐ning Deng Mao Wu Di Chen Zhuo Xia Pin‐hua Gong Xiao‐jian Deng Qin Shi Zhi‐hui Yan Xue‐mei Tian Ru‐qing Jiang Cai‐yun 《Luminescence》2019,34(3):316-323
A novel, rapid and sensitive chemiluminescence (CL) method for the determination of oxytetracycline hydrochloride (OTCH) is described in this paper. The presented method was based on the fact that OTCH could immensely enhance the CL of the reaction of cerium sulfate and tris(2,2‐bipyridyl) ruthenium (II) in acidic medium. Under optimal experimental conditions, CL intensity was favorably linear for OTCH in the range 5.0 × 10?7 to 5.0 × 10?5 g/ml, with a detection limit of 1.5 × 10?7 g/ml (S/N = 3). The relative standard detection was 4.76% for 5.0 × 10?6 g/ml (n = 11). This method was successfully applied to the analysis of OTCH in milk and egg white samples. According to the results of the kinetic curves for OTCH in the Ru(bipy)32+–Ce(SO4)2 CL system, together with CL and ultraviolet (UV)–visible spectra, the possible mechanism of the CL reaction is discussed briefly. 相似文献
175.
Jin‐Zhi Guo Zhen‐Yi Gu Xin‐Xin Zhao Mei‐Yi Wang Xu Yang Yang Yang Wen‐Hao Li Xing‐Long Wu 《Liver Transplantation》2019,9(38)
Flexible Na/K‐ion batteries (NIBs/KIBs) exhibit great potential applications and have drawn much attention due to the continuous development of flexible electronics. However, there are still many huge challenges, mainly the design and construction of flexible electrodes (cathode and anode) with outstanding electrochemical properties. In this work, a unique approach to prepare flexible electrode is proposed by utilizing the commercially available cotton cloth–derived carbon cloth (CC) as a flexible anode and the substrate of a cathode. The binder‐free, self‐supporting, and flexible cathodes (FCC@N/KPB) are prepared by growing Prussian blue microcubes on the flexible CC (FCC). Na/K‐ion full batteries (FCC//FCC@N/KPB) are assembled by using FCC and FCC@N/KPB as anode and cathode, respectively. Electrochemical performance, mechanical flexibility, and practicability of FCC//FCC@N/KPB Na/K‐ion full batteries are evaluated in both coin cells and flexible pouch cells, demonstrating their superior energy‐storage properties (excellent rate performance and cycling stability) and remarkable flexibility (they can work under different bending states). This work provides a new and profound strategy to design flexible electrodes, promoting the development of flexible NIBs/KIBs to be practical and sustainable. 相似文献
176.
Wei Wang Kun Lv Ji‐Rui Wang Jing Zhou Jian‐Qiang Gu Guo‐Xin Zhou Zhi‐Hong Xu 《Entomological Research》2019,49(3):113-122
In the present study, partial sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene of 22 island populations of the springtail Homidia socia in the Thousand Island Lake were sequenced. Across all sequences, 37 haplotypes were identified for the 510‐bp mitochondrial (mt) DNA COI gene. Haplotype 2 was the most common, and was distributed in the most of the 22 island populations. Haplotype diversity ranged from 0.065 to 0.733, and the total genetic diversity was 0.56216. The genetic characteristics of the 22 island populations were analyzed using the fixation index and gene flow, with values of 0.00043–0.94900 and 0.02703–703.72540, respectively. Comparison between (island area and isolations) with population genetic diversity revealed that there were no significant correlations between them, except for a significant correlation between the number of haplotypes and island area. Mantel tests showed that there was no significant correlation between geographic distance and genetic distance among various groups. All the results indicated that there were no obvious relationships between island characteristics and the genetic diversity of the springtails. We consider that the low dispersal capacity of springtails and the island patches surrounded by water in the Thousand Island Lake are the major factors affecting the genetic diversity of H. socia. 相似文献
177.
Yanmei Li Yunpeng Luan Xiaoguang Yue Fei Xiang Dechang Mao Yong Cao Zhi Xiong 《Saudi Journal of Biological Sciences》2019,26(2)
As a complicated micro-ecosystem, gut microbes are closely related to metabolic disease, immune disease and tumor (such as constipation. Long-term constipation would cause intestinal mucosal injury, enteritis, ileus, etc., thus inducing intestine cancer). In this research, intestine cancer model group and Codonopsis foetens treatment group were successfully constructed, and the variation of intestinal microbes were analyzed by 16S rRNA sequence. Results showed that there were changes in bacteria abundance of Firmicutes, Bacteroidetes, Proteobacteria, Deferribacteres, Tenericutes, and Actinobacteria, etc. Codonopsis foetens could directly or indirectly affect the growth and metabolism of Deferribacteres by altering the nutritional ingredient and pH value of intestine “medium”, thus affecting the occurrence and development of intestinal microbes. 相似文献
178.
Xue Liu Yu Meng Zanpei Zhang Yihan Wang Xiaodong Geng Mingwan Li Zhi Li Dangquan Zhang 《Saudi Journal of Biological Sciences》2019,26(6):1227-1246
Cinnamomum camphora is an excellent tree species for construction of forest construction of Henan Province, China. The diverse bioactive components of nano-catalyzed pyrolyzates form cold-acclimated C. camphora branch (CCB) in North China were explored. The raw powder of CCB treated with nano-catalyst (Ag, NiO, 1/2Ag + 1/2NiO) were pyrolyzed at two temperatures (550 °C and 700 °C), respectively. The main pyrolyzates are bioactive components of bioenergy, biomedicines, food additive, spices, cosmetics and chemical, whose total relative contents at 550 °C pyrolyzates are higher than those at 700 °C pyrolyzates. There are abundant components of spices and biomedicine at 550 °C pyrolyzates, while more spices and food additive at 700 °C pyrolyzates. At 550 °C, the content of biomedicine components reaches the highest by 1/2Ag + 1/2NiO nanocatalysis, while the contents of spices and food additive components reach the highest by NiO nanocatalysis. At 700 °C, the content of bioenergy components reaches the highest by 1/2Ag + 1/2NiO nanocatalysis, and the content of cosmetics components reaches the highest by Ag nanocatalysis. The findings suggested that the branch of the cold-acclimated C. camphora have the potential to develop into valued-added products of bioenergy, biomedicine, cosmetics, spices and food additive by nanocatalysis. 相似文献
179.
Jin Zhou Xiao‐Hui Dong Feng‐Zhi Zhang Hui‐Min Zhu Tong Hao Xiao‐Xia Jiang Wei‐Bo Zheng Tao Zhang Pei‐Zhe Wang Hong Li Jie Na Chang‐Yong Wang 《Cell proliferation》2019,52(3)
Induced pluripotent stem cells (iPSCs) are reprogrammed somatic cells that gained self‐renewal and differentiation capacity similar to embryonic stem cells. Taking the precious opportunity of the TianZhou‐1 spacecraft mission, we studied the effect of space microgravity (µg) on the self‐renewal capacity of iPSCs. Murine iPSCs carrying pluripotency reporter Oct4‐GFP were used. The Oct4‐EGFP‐iPSCs clones were loaded into the bioreactor and exposed to μg in outer space for 14 days. The control experiment was performed in identical device but on the ground in earth gravity (1 g). iPSCs clones were compact and highly expressed Oct4 before launch. In μg condition, cells in iPSC clones spread out more rapidly than those in ground 1 g condition during the first 3 days after launch. However, in 1 g condition, as the cell density increases, the Oct4‐GFP signal dropped significantly during the following 3 days. Interestingly, in μg condition, iPSCs originated from the spread‐out clones during the first 3 days appeared to cluster together and reform colonies that activated strong Oct4 expression. On the other hand, iPSC clones in 1 g condition were not able to recover Oct4 expression after overgrown. Our study for the first time performed real‐time imaging on the proliferation process of iPSCs in space and found that in μg condition, cell behaviour appeared to be more dynamic than on the ground. 相似文献
180.
Shijin Tang Yinping Pan Deshuai Lou Shunlin Ji Liancai Zhu Jun Tan Na Qi Qiong Yang Zhi Zhang Biling Yang Wenyan Zhao Bochu Wang 《Protein science : a publication of the Protein Society》2019,28(5):910-919
7α‐Hydroxysteroid dehydrogenase (7α‐HSDH) is an NAD(P)H‐dependent oxidoreductase belonging to the short‐chain dehydrogenases/reductases. In vitro, 7α‐HSDH is involved in the efficient biotransformation of taurochenodeoxycholic acid (TCDCA) to tauroursodeoxycholic acid (TUDCA). In this study, a gene encoding novel 7α‐HSDH (named as St‐2‐1) from fecal samples of black bear was cloned and heterologously expressed in Escherichia coli. The protein has subunits of 28.3 kDa and a native size of 56.6 kDa, which suggested a homodimer. We studied the relevant properties of the enzyme, including the optimum pH, optimum temperature, thermal stability, activators, and inhibitors. Interestingly, the data showed that St‐2‐1 differs from the 7α‐HSDHs reported in the literature, as it functions under acidic conditions. The enzyme displayed its optimal activity at pH 5.5 (TCDCA). The acidophilic nature of 7α‐HSDH expands its application environment and the natural enzyme bank of HSDHs, providing a promising candidate enzyme for the biosynthesis of TUDCA or other related chemical entities. 相似文献