全文获取类型
收费全文 | 202篇 |
免费 | 22篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 18篇 |
2013年 | 15篇 |
2012年 | 14篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 94 毫秒
121.
Polygordius antarcticus sp. nov. is described from benthic material collected at depths ranging between 31 and 61 m in Terra Nova Bay, Ross Sea,
during the 1987–1988 and 1988–1989 expeditions of the Italian National Research Program in Antarctica. This is the first named
species of the genus from Antarctic waters. Although no fully mature specimens were available, the new species appears unique
in combining the following features: a regular pygidium, inflated and with a single ring of round adhesive pads, a conical
prostomium with short antennae (only half as long as the prostomium) and shallow head fold, and a well-developed circulatory
apparatus, with circumoesophageal commissures entering the prostomium and long intersegmental commissures insinuating into
the ventrolateral compartments of the trunk. These and other significant features were investigated by light and scanning
electron microscopy. In the construction of the head and the scheme of the blood system, the new species resembles Polygordius triestinus Woltereck, described by Hempelmann in 1906, an aberrant species inhabiting muddy, anoxic sediments in the Adriatic Sea, but
it differs significantly from it in the shape of the mouth (in P. triestinus the upper lip is hypertrophied and strongly protruding) and the pygidium (in P. triestinus this region is stump-like and non-adhesive). The pygidium of P. antarcticus sp. nov. is encircled by 28–30 small adhesive pads, each with 15–20 glandular openings. Preterminal cirri are lacking, as
are perianal appendages. The anus is surrounded by six to seven lobes of which the midventral is largest and longest. A world
distribution map of the genus is provided.
Accepted: 27 August 1998 相似文献
122.
Interactive influences of climate and parent material on soil microbial community structure in Bornean tropical forest ecosystems 总被引:3,自引:0,他引:3
Rota Wagai Kanehiro Kitayama Takami Satomura Ryosuke Fujinuma Teri Balser 《Ecological Research》2011,26(3):627-636
Climate and parent material strongly control vegetation structure and function, yet their control over the belowground microbial
community is poorly understood. We assessed variation in microbial lipid profiles in undisturbed forest soils (organic and
surface mineral horizons) along an altitudinal gradient (700, 1,700, and 2,700 m a.s.l. mean annual temperature of 12–24°C)
on two contrasting parent materials (acidic metasedimentary vs. ultrabasic igneous rock) in Mt. Kinabalu, Borneo. Soil organic
carbon and nitrogen concentrations were generally higher at higher altitudes and, within a site, at upper soil horizons. Soil
pH ranged from 3.9 to 5.3, with higher values for the ultrabasic soils especially at higher altitudes. The major shifts in
microbial community structure observed were the decline in the ratio of fungal to bacterial lipid markers both with increasing
soil depth and decreasing altitude. The positive correlation between this ratio with soil C and N concentrations suggested
a strong substrate control in accord with the literature from mid to high-latitude ecosystems. Principal component analysis
using seven groups of signature lipids suggested a significant altitude by parent material interaction—the significant difference
in microbial community structure between the two rock types found at 2,700-m sites developed on weakly weathered soils diminished
with decreasing altitude towards 700-m sites where soils were strongly weathered. These results are consistent with the hypothesis
that parent material effect on soil microbial community (either directly via soil geochemistry or indirectly via floristic
composition) is stronger at an earlier stage of ecosystem development. 相似文献
123.
124.
125.
Santosh Revadi Silvia Vitagliano Marco V. Rossi Stacconi Sukanya Ramasamy Suzan Mansourian Silvia Carlin Urska Vrhovsek Paul G. Becher Valerio Mazzoni Omar Rota‐Stabelli Sergio Angeli Teun Dekker Gianfranco Anfora 《Physiological Entomology》2015,40(1):54-64
Drosophila suzukii Matsumura, an endemic pest in southeast Asia, has invaded Europe and the U.S.A. Unlike most of its closely related sibling species, the serrated ovipositor of D. suzukii permits ovipositing in undamaged fresh fruits. In the present study, volatiles are identified from host plants that are potentially involved in D. suzukii host recognition and oviposition behaviour. It is shown that mated females are attracted to volatiles emitted from intact fruits. The antennally‐active suite of compounds released from the fresh fruits is identified by gas chromatography coupled with electroantennographic detection, as well as gas chromatography‐mass spectrometry. In olfactometer bioassays, mated females are significantly attracted to an electroantennographically active volatile, isoamyl acetate, when tested at 10 µg of synthetic compound in a rubber septa, which has a release rate comparable to that of fresh fruits. In addition, a genomic survey shows that D. suzukii not only possesses the full repertoire of genes encoding odorant receptors activated by isoamyl acetate in D. melanogaster, but also that one of the genes, OR67a, is represented by five duplicated copies. These results indicate that D. suzukii uses olfactory cues to select oviposition sites. The identification of volatiles emitted by host fruits that attract D. suzukii may aid in the development of a selective and efficient synthetic lure for monitoring this pest. As a close relative of Drosophila melanogaster, D. suzukii provides a unique opportunity for understanding the physiological mechanisms involved in the shift of this species from use of rotten to ripe fruits for oviposition. 相似文献
126.
Sixty-three embryos were recovered out of 83 estrous cycles (75.9%) and 98 ovulations (64.3%) of five Pantesca jennies, 2 to 5 yr old, naturally mated or artificially inseminated with fresh semen. Embryo recovery rate was influenced by number of ovulations per cycle (133% and 63% for double and single ovulations, respectively), by the day of embryo recovery attempt (12%, 83%, and 75% at Days 7, 8, and 9 after ovulation, respectively), and by the repetition of the embryo recovery attempt on successive cycles (60%, 79%, and 100% for cycles 1 to 7, 8 to 14, and 15 to 24, respectively). All recovered embryos but three were classified as good or excellent. Of 58 nonsurgical embryo transfers to Ragusana jenny recipients, 13 (22.4%), 10 (17.2%), and 9 (15.5%) resulted in a pregnancy at Days 14, 25, and 50, respectively. Recipients’ pregnancy rate was not influenced by the evaluated parameters: embryo quality and age, media employed to wash embryos, days after ovulation of the recipient, experience of the operator. Between 14 and 50 d of pregnancy, 4 of 13 (30.7%) embryos were lost with an influence of the days from ovulation of the recipient: recipients at Days 5 or 6 kept all pregnancies (N = 7), whereas recipients at Days 7 or 8 lost 3 of 4 pregnancies, as one of the two recipients at Day 3. More studies are needed before embryo transfer could be considered a reliable tool to preserve endangered donkey breeds. 相似文献
127.
GW Patton R Stephens IA Sidorov X Xiao RA Lempicki DS Dimitrov RH Shoemaker G Tudor 《BMC bioinformatics》2006,7(1):81
Background
Microarrays used for gene expression studies yield large amounts of data. The processing of such data typically leads to lists of differentially-regulated genes. A common terminal data analysis step is to map pathways of potentially interrelated genes. 相似文献128.
Roel GW Verhaak Frank JT Staal Peter JM Valk Bob Lowenberg Marcel JT Reinders Dick de Ridder 《BMC bioinformatics》2006,7(1):105-15
Background
Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers. 相似文献129.
130.
Benzoyl peroxide is commonly used in the treatment of acne, even though some adverse effects have been reported, probably mediated by the formation of peroxide-derived free radicals and the depletion of antioxidants. In the present work we have studied, in a chemical system, the effect of alpha-tocopherol on benzoyl peroxide radical decomposition to analyse the presence of an interaction between these two compounds, leading to an enhanced peroxide-cytotoxicity, as we have previously reported. Under our experimental conditions alpha-tocopherol strongly amplified the peroxide free radical decomposition occurring either in the presence or in the absence of UV irradiation, and lead to the formation of an unknown radical species in addition to benzoyloxy, phenyl and tocopheroxyl free radicals. The results of this study show that the enhancement of benzoyl peroxide toxicity in cells exposed simultaneously to this peroxide and alpha-tocopherol, is likely due to the generation of the detected radical species. 相似文献