全文获取类型
收费全文 | 104篇 |
免费 | 6篇 |
国内免费 | 3篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 11篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 1篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 4篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有113条查询结果,搜索用时 312 毫秒
61.
LAËTITIA BUISSON WILFRIED THUILLER SOVAN LEK PUY LIM GAËL GRENOUILLET 《Global Change Biology》2008,14(10):2232-2248
Stream fish are expected to be significantly influenced by climate change, as they are ectothermic animals whose dispersal is limited within hydrographic networks. Nonetheless, they are also controlled by other physical factors that may prevent them moving to new thermally suitable sites. Using presence–absence records in 655 sites widespread throughout nine French river units, we predicted the potential future distribution of 30 common stream fish species facing temperature warming and change in precipitation regime. We also assessed the potential impacts on fish assemblages' structure and diversity. Only cold-water species, whose diversity is very low in French streams, were predicted to experience a strong reduction in the number of suitable sites. In contrast, most cool-water and warm-water fish species were projected to colonize many newly suitable sites. Considering that cold headwater streams are the most numerous on the Earth's surface, our results suggested that headwater species would undergo a deleterious effect of climate change, whereas downstream species would expand their range by migrating to sites located in intermediate streams or upstream. As a result, local species richness was forecasted to increase greatly and high turnover rates indicated future fundamental changes in assemblages' structure. Changes in assemblage composition were also positively related to the intensity of warming. Overall, these results (1) stressed the importance of accounting for both climatic and topographic factors when assessing the future distribution of riverine fish species and (2) may be viewed as a first estimation of climate change impacts on European freshwater fish assemblages. 相似文献
62.
GUILLAUME MARTI MATTHIAS ERB JULIEN BOCCARD GAÉTAN GLAUSER GWLADYS R. DOYEN NEIL VILLARD CHRISTELLE A M. ROBERT TED C. J. TURLINGS SERGE RUDAZ JEAN‐LUC WOLFENDER 《Plant, cell & environment》2013,36(3):621-639
Plants respond to herbivory by reprogramming their metabolism. Most research in this context has focused on locally induced compounds that function as toxins or feeding deterrents. We developed an ultra‐high‐pressure liquid chromatography time‐of‐flight mass spectrometry (UHPLC‐TOF‐MS)‐based metabolomics approach to evaluate local and systemic herbivore‐induced changes in maize leaves, sap, roots and root exudates without any prior assumptions about their function. Thirty‐two differentially regulated compounds were identified from Spodoptera littoralis‐infested maize seedlings and isolated for structure assignment by microflow nuclear magnetic resonance (CapNMR). Nine compounds were quantified by a high throughput direct nano‐infusion tandem mass spectrometry/mass spectrometry (MS/MS) method. Leaf infestation led to a marked local increase of 1,3‐benzoxazin‐4‐ones, phospholipids, N‐hydroxycinnamoyltyramines, azealic acid and tryptophan. Only few changes were found in the root metabolome, but 1,3‐benzoxazin‐4‐ones increased in the vascular sap and root exudates. The role of N‐hydroxycinnamoyltyramines in plant–herbivore interactions is unknown, and we therefore tested the effect of the dominating p‐coumaroyltyramine on S. littoralis. Unexpectedly, p‐coumaroyltyramine was metabolized by the larvae and increased larval growth, possibly by providing additional nitrogen to the insect. Taken together, this study illustrates that herbivore attack leads to the induction of metabolites that can have contrasting effects on herbivore resistance in the leaves and roots. 相似文献
63.
目的:分析新疆地区近20年来胃癌流行病学特征,探讨其变化规律及发展趋势。方法:回顾性分析和比较1991年、2001年、2011年经新疆维吾自治区人民医院胃镜及病理学诊断确诊为胃癌的病例的一般资料、病理学及内镜下特点,包括性别、年龄、病理类型、发病部位。结果:1991年组:胃癌检出率为2.48%,中位年龄为54岁,男女之比为3-3:1.0,发病部位以胃窦部癌为主,占39.1%;2001年组:检出率为2.39%,中位年龄为61岁,男女之比为3.0:1.0,发病部位以胃体部癌为主,占42.1%;2011年组:检出率为1.48%,中位年龄为63岁,男女之比为3.9:1.0,发病部位以贵门胃底部为主,占34.8%。三组病理学类型均以腺癌为主,检出率有逐年升高趋势,但差异无统计学意义(P〉0.05)。结论:(1)近20年来胃癌发病部位有上移现象,且胃癌检发病率有下降趋势;(2)男性胃癌患者发病率明显高于女性,且近20年来胃癌患者男女比例无明显改变;(3)近20年来胃癌发病中位年龄逐渐增高,且随着年龄的增长发病率逐渐升高,以中老年发病率最高;(4)癌患者病理类型仍以腺癌为主,且近20年来腺癌所占比例无明显变化. 相似文献
64.
The interstitial cells of Cajal (ICC) have been reported to regulate gastrointestinal motility. We investigated the distribution and the morphological and morphometric characteristics of the immunohistochemical reaction against c-kit in the forestomachs of fetal, newborn and adult cows. The anti-c-kit reaction revealed different populations of ICC among age groups and organs. ICC were more numerous and smaller in fetuses. Larger ICC were identified in newborns, except for those in the rumen. During the earliest stages of development, ICC were abundant in the inner layer of the muscularis and were consistently associated with this layer. In all samples, ICC were found in the outer layer of the tunica muscularis. ICC were found between the two muscle layers in the omasum at all ages; however, they were identified only in the rumen of the adult. Our study demonstrated that ICC are present in the forestomach of bovines. 相似文献
65.
Effect of T cell-derived lymphokines containing B cell differentiation factor(s) for IgG (BCDF gamma) on gamma-specific mRNA in murine B cells 总被引:5,自引:0,他引:5
S Jones Y W Chen P Isakson J Layton E Pure C Word P H Krammer P Tucker E S Vitetta 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(6):3049-3051
Cytoplasmic RNA was isolated from cells cultured with LPS and LPS plus a T cell-derived supernatant (SN) (PK 7.1) containing B cell differentiation factors. The steady state levels of isotype-specific mRNA were assessed by Northern blot analysis with gamma-specific CH3 probes. It was demonstrated that the SN induces an increase in the level of mRNA for gamma 1 and a concomitant decrease in the levels of mRNA for gamma 2b and gamma 3. 相似文献
66.
Background
Genome and metagenome studies have identified thousands of protein families whose functions are poorly understood and for which techniques for functional characterization provide only partial information. For such proteins, the genome context can give further information about their functional context. 相似文献67.
68.
69.
Partial suppression of an ochre mutation in Saccharomyces cerevisiae by multicopy plasmids containing a normal yeast tRNAGln gene 总被引:24,自引:0,他引:24
We screened a yeast genomic library for recombinant DNA plasmids that complemented the ultraviolet (u.v.) sensitivity of a strain of Saccharomyces cerevisiae designated rad4-3 that is defective in excision repair of DNA. A multicopy plasmid (pNF4000) with a 9.4 X 10(3) base-pair yeast DNA insert partially complemented the u.v. sensitivity of rad4-3, but not of two other rad4 allelic mutants (rad4-2 and rad4-4), or of other u.v.-sensitive rad mutants. The yeast insert was analyzed by restriction mapping, DNA-DNA hybridization, DNA-tRNA hybridization and DNA sequencing. This analysis revealed the presence of a normal tRNAGln gene, a yeast sigma element situated 5' to the transfer RNA gene, a Ty element and a solo delta element. Deletion analysis of pNF4000 showed that the tRNAGln gene is required for partial complementation of the u.v. sensitivity of rad4-3. Furthermore, a multicopy plasmid containing a tRNAGln gene derived from a different region of the yeast genome also partially complemented the u.v. sensitivity of rad4-3. The rad4-3 mutation is suppressed following transformation with a plasmid containing the known ochre suppressor SUP11-o, indicating that it is an ochre mutation. We therefore conclude that when expressed in sufficient quantity, normal tRNAGln (which usually decodes the sense codon CAA) can weakly suppress the nonsense ochre codon UAA, and suggest that this represents an example of wobble occurring at the first rather than at the third position of the codon. 相似文献
70.
Cross-hybridizing snake satellite, Drosophila, and mouse DNA sequences may have arisen independently 总被引:2,自引:0,他引:2
Previous reports have interpreted hybridization between snake satellite DNA
and DNA clones from a variety of distant taxonomic groups as evidence for
evolutionary conservation, which implies common ancestry (homology) and/or
convergence (analogy) to produce the cross- hybridizing sequences. We have
isolated 11 clones from a genomic library of Drosophila melanogaster, using
a cloned 2.5-kb snake satellite probe of known nucleotide sequence. We have
also analysed published sequence data from snakes, mice, and Drosophila.
These data show that (1) all of the cross-hybridization between the snake,
fly, and mouse clones can be accounted for by the presence of either of two
tandem repeats, [GATA]n and [GACA]n and (2) these tandem repeats are
organized differently among the different species. We find no evidence that
these sequences are homologous apart from the existence of the simple
repeat itself, although their divergence from a common ancestral sequence
cannot be ruled out. The sequences contain a variety of homogeneous
clusters of tandem repeats of CATA, GA, TA, and CA, as well as GATA and
GACA. We suggest that these motifs may have arisen by a self-accelerating
process involving slipped-strand mispairing of DNA. Homogeneity of the
clusters might simply be the result of a rate of accumulation of tandem
repeats that exceeds that of other mutations.
相似文献