全文获取类型
收费全文 | 600篇 |
免费 | 84篇 |
专业分类
684篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 2篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 36篇 |
2013年 | 38篇 |
2012年 | 48篇 |
2011年 | 37篇 |
2010年 | 24篇 |
2009年 | 20篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 11篇 |
2005年 | 27篇 |
2004年 | 37篇 |
2003年 | 24篇 |
2002年 | 28篇 |
2001年 | 18篇 |
2000年 | 25篇 |
1999年 | 20篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有684条查询结果,搜索用时 15 毫秒
71.
72.
Adhihetty PJ Taivassalo T Haller RG Walkinshaw DR Hood DA 《American journal of physiology. Endocrinology and metabolism》2007,293(3):E672-E680
Mitochondrial myopathy patients (MMPs) have impaired oxidative phosphorylation and exercise intolerance. Endurance training of MMPs improves exercise tolerance, but also increases mutational load. To assess the regulation of mitochondrial content in MMPs, we measured proteins involved in 1) biogenesis, 2) oxidative stress, and 3) apoptosis in MMPs and healthy controls (HCs) both before and after endurance training. Before training, MMPs had a greater mitochondrial content, along with a 1.4-fold (P < 0.05) higher expression of the biogenesis regulator peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha). The DNA repair enzyme 8-oxoguanine DNA glycolase-1 (OGG-1), the antioxidant manganese superoxide dismutase (MnSOD), and the apoptotic proteins AIF and Bcl-2 were higher in MMPs compared with HCs. Aconitase, an enzyme sensitive to oxidative stress, was 52% lower (P < 0.05) in MMPs when calculated based on an estimate of mitochondrial volume and oxidative stress-induced protein modifications tended to be higher in MMPs compared with HCs. Endurance training (ET) induced increases in mitochondrial content in both HC subjects and MMPs, but there was no effect of training on the regulatory proteins Tfam or PGC-1alpha. In MMPs, training induced a selective reduction of OGG-1, an increase in MnSOD, and a reduction in aconitase activity. Thus, before training, MMPs exhibited an adaptive response of nuclear proteins indicative of a compensatory increase in mitochondrial content. Following training, several parallel adaptations occurred in MMPs and HCs, which may contribute to previously observed functional improvements of exercise in MMPs. However, our results indicate that muscle from MMPs may be exposed to greater levels of oxidative stress during the course of training. Further investigation is required to evaluate the long-term benefits of endurance training as a therapeutic intervention for mitochondrial myopathy patients. 相似文献
73.
Interferon-induced Mx proteins in antiviral host defense 总被引:7,自引:0,他引:7
74.
Viral suppression of the interferon system 总被引:5,自引:0,他引:5
Type I interferons (IFN-alpha/beta) were originally discovered by their strong and direct antiviral activity [A. Isaacs, J. Lindenmann, Virus interference. I. The interferon, Proc. R. Soc. Lond. B Biol. Sci. 147 (1957) 258-267]. (see review by J. Lindenmann on p. 719, in this issue). Nevertheless, only very recently it was entirely realized that viruses would not succeed without efficient tools to undermine this potent host defense system. Current investigations are revealing an astonishing variety of viral IFN antagonistic strategies targeting virtually all parts of the IFN system, often in a highly specific manner. Viruses were found to interfere with induction of IFN synthesis, IFN-induced signaling events, the antiviral effector proteins, or simply shut off the host cell macromolecule synthesis machinery to avoid booting of the antiviral host defense. Here, we will describe a few well-characterized examples to illustrate the sophisticated and often multi-layered anti-IFN mechanisms employed by viruses. 相似文献
75.
76.
Chu LJ Yang H Shih P Kao Y Tsai YS Chen J Huang G Weng RR Ting YS Fang X von Haller PD Goodlett DR Ng WV 《Journal of proteome research》2011,10(7):3261-3273
The 1310 Haloarcula marismortui proteins identified from mid-log and late-log phase soluble and membrane proteomes were analyzed in metabolic and cellular process networks to predict the available systems and systems fluctuations upon environmental stresses. When the connected metabolic reactions with identified proteins were examined, the availability of a number of metabolic pathways and a highly connected amino acid metabolic network were revealed. Quantitative spectral count analyses suggested 300 or more proteins might have expression changes in late-log phase. Among these, integrative network analyses indicated approximately 106 were metabolic proteins that might have growth-phase dependent changes. Interestingly, a large proportion of proteins in affected biomodules had the same trend of changes in spectral counts. Disregard the magnitude of changes, we had successfully predicted and validated the expression changes of nine genes including the rimK, gltCP, rrnAC0132, and argC in lysine biosynthesis pathway which were downregulated in late-log phase. This study had not only revealed the expressed proteins but also the availability of biological systems in two growth phases, systems level changes in response to the stresses in late-log phase, cellular locations of identified proteins, and the likely regulated genes to facilitate further analyses in the postgenomic era. 相似文献
77.
In a study with rats it was determined whether dietary magnesium concentration affects plasma esterase activities. The feeding of a diet with 0.01% (w/w) instead of 0.04% magnesium reduced plasma magnesium concentration by 50%. Plasma total esterase, arylesterase and butyrylcholinesterase activities were significantly decreased in the magnesium-deficient rats. In rats fed a diet containing 0.02% magnesium, plasma magnesium concentration was lowered by 30%, and group mean plasma total esterase activity was decreased, but not the activities of arylesterase and butyrylcholinesterase. 相似文献
78.
Miika Laihonen Kari Saikkonen Marjo Helander Toomas Tammaru 《Ecology and evolution》2020,10(14):7242-7249
Variation in plant communities is likely to modulate the feeding and oviposition behavior of herbivorous insects, and plant‐associated microbes are largely ignored in this context. Here, we take into account that insects feeding on grasses commonly encounter systemic and vertically transmitted (via seeds) fungal Epichloë endophytes, which are regarded as defensive grass mutualists. Defensive mutualism is primarily attributable to alkaloids of fungal origin. To study the effects of Epichloë on insect behavior and performance, we selected wild tall fescue (Festuca arundinacea) and red fescue (Festuca rubra) as grass–endophyte models. The plants used either harbored the systemic endophyte (E+) or were endophyte‐free (E?). As a model herbivore, we selected the Coenonympha hero butterfly feeding on grasses as larvae. We examined both oviposition and feeding preferences of the herbivore as well as larval performance in relation to the presence of Epichloë endophytes in the plants. Our findings did not clearly support the female's oviposition preference to reflect the performance of her offspring. First, the preference responses depended greatly on the grass–endophyte symbiotum. In F. arundinacea, C. hero females preferred E+ individuals in oviposition‐choice tests, whereas in F. rubra, the endophytes may decrease exploitation, as both C. hero adults and larvae preferred E? grasses. Second, the endophytes had no effect on larval performance. Overall, F. arundinacea was an inferior host for C. hero larvae. However, the attraction of C. hero females to E+ may not be maladaptive if these plants constitute a favorable oviposition substrate for reasons other than the plants' nutritional quality. For example, rougher surface of E+ plant may physically facilitate the attachment of eggs, or the plants offer greater protection from natural enemies. Our results highlight the importance of considering the preference of herbivorous insects in studies involving the endophyte‐symbiotic grasses as host plants. 相似文献
79.
It is often claimed that some organisms maximise individual growth rates (within limits set by physiological and environmental constraints) whereas others do not. Adequate experimental protocol to test for these hypotheses has not been available. We proceeded from the idea that a maximiser should be unable to further improve its growth performance, i.e. there should be no adaptive plasticity in relative growth rates. In the case of an insect larva always maximising its weight gain, we should thus expect no increase in growth rate following a short-term environmental perturbation. Another prediction is that initial and final weights of a larval instar should be highly correlated. We applied this approach to test for the growth rate maximiser status of the geometrid moth Epirrita autumnata . Based on various lines of ecological evidence it had previously been suggested that this spring-feeding species is strongly selected for high growth rates, and may be growing at its maximum physiological potential. Contrary to expectations, the larvae responded to starvation treatments by a subsequent compensatory increase in their relative growth rates. Such a plasticity may indicate that the rates of gaining weight are not maximised even in a 'classical' example a time-constrained organism. This observation supports the idea that endogenous regulation of growth rates is widespread, and it remains to be shown if true maximisation ever exists in nature. In contrast, possibilities to compensate for adverse conditions experienced early in larval development appeared to be limited. This was indicated by the strong correlation between initial weight in the last instar, and pupal weight. Though consistent with our expectations, such an inability to compensate can hardly be ascribed to growth rate maximisation, as indicated by quantitatively similar patterns found in an unrelated species with different ecology, the butterfly Polygonia c-album . 相似文献
80.
Large-scale identification of expressed sequence tags involved in rice and rice blast fungus interaction 总被引:15,自引:0,他引:15 下载免费PDF全文
Jantasuriyarat C Gowda M Haller K Hatfield J Lu G Stahlberg E Zhou B Li H Kim H Yu Y Dean RA Wing RA Soderlund C Wang GL 《Plant physiology》2005,138(1):105-115
To better understand the molecular basis of the defense response against the rice blast fungus (Magnaporthe grisea), a large-scale expressed sequence tag (EST) sequencing approach was used to identify genes involved in the early infection stages in rice (Oryza sativa). Six cDNA libraries were constructed using infected leaf tissues harvested from 6 conditions: resistant, partially resistant, and susceptible reactions at both 6 and 24 h after inoculation. Two additional libraries were constructed using uninoculated leaves and leaves from the lesion mimic mutant spl11. A total of 68,920 ESTs were generated from 8 libraries. Clustering and assembly analyses resulted in 13,570 unique sequences from 10,934 contigs and 2,636 singletons. Gene function classification showed that 42% of the ESTs were predicted to have putative gene function. Comparison of the pathogen-challenged libraries with the uninoculated control library revealed an increase in the percentage of genes in the functional categories of defense and signal transduction mechanisms and cell cycle control, cell division, and chromosome partitioning. In addition, hierarchical clustering analysis grouped the eight libraries based on their disease reactions. A total of 7,748 new and unique ESTs were identified from our collection compared with the KOME full-length cDNA collection. Interestingly, we found that rice ESTs are more closely related to sorghum (Sorghum bicolor) ESTs than to barley (Hordeum vulgare), wheat (Triticum aestivum), and maize (Zea mays) ESTs. The large cataloged collection of rice ESTs in this study provides a solid foundation for further characterization of the rice defense response and is a useful public genomic resource for rice functional genomics studies. 相似文献