全文获取类型
收费全文 | 5816篇 |
免费 | 460篇 |
国内免费 | 1篇 |
出版年
2023年 | 38篇 |
2022年 | 85篇 |
2021年 | 185篇 |
2020年 | 119篇 |
2019年 | 146篇 |
2018年 | 194篇 |
2017年 | 168篇 |
2016年 | 250篇 |
2015年 | 316篇 |
2014年 | 388篇 |
2013年 | 398篇 |
2012年 | 426篇 |
2011年 | 393篇 |
2010年 | 223篇 |
2009年 | 219篇 |
2008年 | 285篇 |
2007年 | 247篇 |
2006年 | 199篇 |
2005年 | 206篇 |
2004年 | 169篇 |
2003年 | 152篇 |
2002年 | 140篇 |
2001年 | 126篇 |
2000年 | 104篇 |
1999年 | 100篇 |
1998年 | 47篇 |
1997年 | 44篇 |
1996年 | 38篇 |
1995年 | 29篇 |
1994年 | 37篇 |
1993年 | 28篇 |
1992年 | 56篇 |
1991年 | 64篇 |
1990年 | 52篇 |
1989年 | 42篇 |
1988年 | 40篇 |
1987年 | 43篇 |
1986年 | 57篇 |
1985年 | 37篇 |
1984年 | 35篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1975年 | 30篇 |
1974年 | 20篇 |
1971年 | 17篇 |
排序方式: 共有6277条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
Jasmina Vidic Charles-Adrien Richard Christine Péchoux Bruno Da Costa Nicolas Bertho Sandra Mazerat Bernard Delmas Christophe Chevalier 《The Journal of biological chemistry》2016,291(2):739-751
PB1-F2 is a small accessory protein encoded by an alternative open reading frame in PB1 segments of most influenza A virus. PB1-F2 is involved in virulence by inducing mitochondria-mediated immune cells apoptosis, increasing inflammation, and enhancing predisposition to secondary bacterial infections. Using biophysical approaches we characterized membrane disruptive activity of the full-length PB1-F2 (90 amino acids), its N-terminal domain (52 amino acids), expressed by currently circulating H1N1 viruses, and its C-terminal domain (38 amino acids). Both full-length and N-terminal domain of PB1-F2 are soluble at pH values ≤6, whereas the C-terminal fragment was found soluble only at pH ≤ 3. All three peptides are intrinsically disordered. At pH ≥ 7, the C-terminal part of PB1-F2 spontaneously switches to amyloid oligomers, whereas full-length and the N-terminal domain of PB1-F2 aggregate to amorphous structures. When incubated with anionic liposomes at pH 5, full-length and the C-terminal part of PB1-F2 assemble into amyloid structures and disrupt membrane at nanomolar concentrations. PB1-F2 and its C-terminal exhibit no significant antimicrobial activity. When added in the culture medium of mammalian cells, PB1-F2 amorphous aggregates show no cytotoxicity, whereas PB1-F2 pre-assembled into amyloid oligomers or fragmented nanoscaled fibrils was highly cytotoxic. Furthermore, the formation of PB1-F2 amyloid oligomers in infected cells was directly reflected by membrane disruption and cell death as observed in U937 and A549 cells. Altogether our results demonstrate that membrane-lytic activity of PB1-F2 is closely linked to supramolecular organization of the protein. 相似文献
945.
Testing monophyly of the freshwater fish Leporinus (Characiformes,Anostomidae) through molecular analysis 下载免费PDF全文
J. L. Ramirez L. F. Carvalho‐Costa P. C. Venere D. C. Carvalho W. P. Troy P. M. Galetti Jr. 《Journal of fish biology》2016,88(3):1204-1214
Monophyly of the genus Leporinus (Characiformes: Anostomidae) was tested by sequencing and analysing a total of 4732 bp, including two mitochondrial [cytochrome oxidase subunit 1 (CO1) and cytochrome b (Cytb)] and three nuclear [myosin heavy chain 6 cardiac muscle alpha (Myh6), recombination activating gene 1 (RAG1) and recombination activating gene 2 (RAG2)] loci for 22 species of Leporinus, or c. 25% of all described species in the genus. Phylogenetic tree analyses (maximum parsimony, maximum likelihood and Bayesian species tree) indicate Leporinus to be paraphyletic, with monophyly being rejected by both Kishino–Hasegawa and Shimodaira–Hasegawa tests. The sequenced species of Leporinus are distributed across five clades that are interleaved among other anostomid genera. Several taxonomic changes are suggested as being necessary to restore monophyly for the group. The clade containing the type species, Leporinus fasciatus, should be considered Leporinus sensu stricto and at least three new genera should be described for other species currently considered part of Leporinus. 相似文献
946.
Genetic structure and host–parasite co‐divergence: evidence for trait‐specific local adaptation 下载免费PDF全文
Clément Lagrue Arnaud Joannes Robert Poulin Isabel Blasco‐Costa 《Biological journal of the Linnean Society. Linnean Society of London》2016,118(2):344-358
Host–parasite co‐evolution can lead to genetic differentiation among isolated host–parasite populations and local adaptation between parasites and their hosts. However, tests of local adaptation rarely consider multiple fitness‐related traits although focus on a single component of fitness can be misleading. Here, we concomitantly examined genetic structure and co‐divergence patterns of the trematode Coitocaecum parvum and its crustacean host Paracalliope fluviatilis among isolated populations using the mitochondrial cytochrome oxidase I gene (COI). We then performed experimental cross‐infections between two genetically divergent host–parasite populations. Both hosts and parasites displayed genetic differentiation among populations, although genetic structure was less pronounced in the parasite. Data also supported a co‐divergence scenario between C. parvum and P. fluviatilis potentially related to local co‐adaptation. Results from cross‐infections indicated that some parasite lineages seemed to be locally adapted to their sympatric (home) hosts in which they achieved higher infection and survival rates than in allopatric (away) amphipods. However, local, intrinsic host and parasite characteristics (host behavioural or immunological resistance to infections, parasite infectivity or growth rate) also influenced patterns of host–parasite interactions. For example, overall host vulnerability to C. parvum varied between populations, regardless of parasite origin (local vs. foreign), potentially swamping apparent local co‐adaptation effects. Furthermore, local adaptation effects seemed trait specific; different components of parasite fitness (infection and survival rates, growth) responded differently to cross‐infections. Overall, data show that genetic differentiation is not inevitably coupled with local adaptation, and that the latter must be interpreted with caution in a multi‐trait context. 相似文献
947.
Effect of copper oxide nanoparticles on growth,morphology, photosynthesis,and antioxidant response in Oryza sativa 总被引:1,自引:0,他引:1
The physiological and biochemical behaviour of rice (Oryza sativa, var. Jyoti) treated with copper (II) oxide nanoparticles (CuO NPs) was studied. Germination rate, root and shoot length, and biomass decreased, while uptake of Cu in the roots and shoots increased at high concentrations of CuO NPs. The accumulation of CuO NPs was observed in the cells, especially, in the chloroplasts, and was accompanied by a lower number of thylakoids per granum. Photosynthetic rate, transpiration rate, stomatal conductance, maximal quantum yield of PSII photochemistry, and photosynthetic pigment contents declined, with a complete loss of PSII photochemical quenching at 1,000 mg(CuO NP) L?1. Oxidative and osmotic stress was evidenced by increased malondialdehyde and proline contents. Elevated expression of ascorbate peroxidase and superoxide dismutase were also observed. Our work clearly demonstrated the toxic effect of Cu accumulation in roots and shoots that resulted in loss of photosynthesis. 相似文献
948.
949.