全文获取类型
收费全文 | 343篇 |
免费 | 17篇 |
专业分类
360篇 |
出版年
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 14篇 |
2012年 | 28篇 |
2011年 | 15篇 |
2010年 | 17篇 |
2009年 | 9篇 |
2008年 | 22篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 20篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 24篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1979年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有360条查询结果,搜索用时 0 毫秒
1.
2.
3.
Differential expression of cellular microRNAs in HPV-11 transfected cells. An analysis by three different array platforms and qRT-PCR 总被引:1,自引:0,他引:1
Dreher A Rossing M Kaczkowski B Nielsen FC Norrild B 《Biochemical and biophysical research communications》2010,403(3-4):357-362
Human papillomavirus type 11 (HPV-11) infects the genital and the respiratory tract leading to condylomas and respiratory papillomatosis. HPV infections are restricted to epithelial tissue and the progression through the virus lifecycle is tightly coordinated to the differentiation of the host cell. The changes of cellular microRNAs by HPV-11 gene expression were investigated in a cell culture model of HaCaT cells transfected with HPV-11, with the goal of understanding which cellular processes were affected by the virus. Human microRNA profiling was conducted on three different array platform systems and because very few microRNAs (miR-663, -638, -149* and -92b*) were consistently found in all three array data sets we performed extensive statistical analyses of the array data and the qRT-PCR validation. We assume that the most reliable differentially expressed microRNAs are the ones identified by more than one array platform. We also show that TaqMan? qRT-PCR validation is of limited use for less abundant microRNAs. 相似文献
4.
The impact of changing the season in which cereals are sown on the diversity of the weed flora in rotational fields in Denmark 总被引:1,自引:1,他引:1
Anna Bodil Hald 《Journal of Applied Ecology》1999,36(1):24-32
1. Surveys have shown that there has been a dramatic decrease in the weed flora of fields under rotational cultivation during the last 30 years. This trend has been particularly noticeable in winter cereals, a crop of increasing importance in the landscape.
2. The weed flora of spring and winter cereals was compared in 19 unsprayed fields during a 5-year study to test the hypothesis that cereal type exerts no effect on the flora or on the absolute and relative abundance of single species.
3. Plant and species densities, and accumulated species richness, were lower in winter than in spring cereals.
4. Floristic similarity was greater among spring cereal fields and between spring and winter cereals within the same fields than among winter cereal fields.
5. Species that occurred with unequal density in spring and winter cereals occurred at higher densities in the spring cereals; these species germinated mainly in the spring. However, for a few species the relative plant abundance was highest in winter cereals; these species were able to germinate both in the spring and autumn.
6. Some species – on the relative scale – occurred indifferently of season of sowing; all but one of these species were able to germinate both in the spring and autumn.
7. Plant species and taxa that are important food resources for arthropod herbivores occurred at greater densities in spring than in winter cereals and, in addition, occurred with the highest relative abundance in spring cereals.
8. Change in land use from spring to winter cereals involves not only an immediate reduction of more than 25% in the density of plants and species, but also a change and increased uncertainty in the composition of the weed flora. These findings may have serious implications for the ecology of wildlife in the agricultural landscape. 相似文献
2. The weed flora of spring and winter cereals was compared in 19 unsprayed fields during a 5-year study to test the hypothesis that cereal type exerts no effect on the flora or on the absolute and relative abundance of single species.
3. Plant and species densities, and accumulated species richness, were lower in winter than in spring cereals.
4. Floristic similarity was greater among spring cereal fields and between spring and winter cereals within the same fields than among winter cereal fields.
5. Species that occurred with unequal density in spring and winter cereals occurred at higher densities in the spring cereals; these species germinated mainly in the spring. However, for a few species the relative plant abundance was highest in winter cereals; these species were able to germinate both in the spring and autumn.
6. Some species – on the relative scale – occurred indifferently of season of sowing; all but one of these species were able to germinate both in the spring and autumn.
7. Plant species and taxa that are important food resources for arthropod herbivores occurred at greater densities in spring than in winter cereals and, in addition, occurred with the highest relative abundance in spring cereals.
8. Change in land use from spring to winter cereals involves not only an immediate reduction of more than 25% in the density of plants and species, but also a change and increased uncertainty in the composition of the weed flora. These findings may have serious implications for the ecology of wildlife in the agricultural landscape. 相似文献
5.
Binderup E Björkling F Hjarnaa PV Latini S Baltzer B Carlsen M Binderup L 《Bioorganic & medicinal chemistry letters》2005,15(10):2491-2494
To overcome pharmacokinetic and solubility problems observed in early clinical trials with the potent anticancer compound CHS828, we synthesised a series of prodrugs with improved properties. The best compound obtained was EB1627, with a tetraethyleneglycol moiety attached to the parent drug via a carbonate linkage. This compound was found soluble enough to be given i.v. and the drug was rapidly released in vivo exerting a very potent inhibitory activity alone and in combination with known cytostatics (etoposide) in animal models in vivo. 相似文献
6.
Background and AimsHorizontal gene transfer (HGT) is an important evolutionary mechanism because it transfers genetic material that may code for traits or functions between species or genomes. It is frequent in mitochondrial and nuclear genomes but has not been demonstrated between plastid genomes of different green land plant species.MethodsWe Sanger-sequenced the nuclear internal transcribed spacers (ITS1 and 2) and the plastid rpl16 G2 intron (rpl16). In five individuals with foreign rpl16 we also sequenced atpB-rbcL and trnLUAA-trnFGAA.Key ResultsWe discovered 14 individuals of a moss species with typical nuclear ITSs but foreign plastid rpl16 from a species of a distant lineage. None of the individuals with three plastid markers sequenced contained all foreign markers, demonstrating the transfer of plastid fragments rather than the entire plastid genome, i.e. entire plastids were not transferred. The two lineages diverged 165–185 Myr BP. The extended time interval since lineage divergence suggests that the foreign rpl16 is more likely explained by HGT than by hybridization or incomplete lineage sorting.ConclusionsWe provide the first conclusive evidence of interspecific plastid-to-plastid HGT among land plants. Two aspects are critical: it occurred at several localities during the massive colonization of recently disturbed open habitats that were created by large-scale liming as a freshwater biodiversity conservation measure; and it involved mosses whose unique life cycle includes spores that first develop a filamentous protonema phase. We hypothesize that gene transfer is facilitated when protonema filaments of different species intermix intimately when colonizing disturbed early succession habitats. 相似文献
7.
The regular sea urchin, Strongylocentrotus pallidus (G.O. Sars, 1871), is a widespread epibenthic species in high-Arctic waters. However, little is known about its distribution, standing stock, population dynamics and production. In the northern Barents Sea, S. pallidus was recorded on seabed still photographs at 10 out of 11 stations in water depths of 80–360?m. Mean abundances along photographic transects of 150–300 m length ranged between <0.1 and 14.7?ind. m?2 yielding a grand average of 3.6?ind.?m?2. The small-scale distribution along the transects was patchy, with densities varying from nil to an overall maximum of 25.5 ind. m?2, and exhibited a significant relation to the number of stones present. Sea urchin test diameters, measured on scaled photographs, extended from 7 to 90?mm. Median values at single stations varied from 14 to 46?mm, showing a significant inverse relationship to water depth. Biomass, estimated by combining photographic abundances, size frequencies and a size-mass function established with trawled specimens, ranged between <0.1 and 3.0?g ash-free dry mass m?2, averaging about 1.0?g ash free dry mass m?2. An analysis of skeletal growth bands in genital plates was carried out with 143 trawled individuals ranging in test diameter (D) from 4 to 48?mm. Assuming these bands to represent annual growth marks, the ages of the specimens analysed ranged between 3 and 42 years. A von Bertalanffy function was fitted to size-at-age data to model individual growth pattern (D∞?=?102.3?mm, k?=?0.011 year?1, t0?=?0.633?year). The annual mortality rate Z of the population in the northern Barents Sea was estimated from a size-converted catch curve to be 0.08 year?1. Applying the weight-specific growth rate method, the average P/B ratio and the mean annual production of this population were estimated as 0.07 year?1 and 0.076?g AFDM m?2 year?1, respectively. In conclusion, S. pallidus is characterized by slow growth, low mortality, high longevity and low productivity. Because of its relatively high biomass, it is considered to contribute significantly to total benthic standing stock and carbon flux in the study area. 相似文献
8.
Hypoxia, mainly caused by eutrophication, is a common and growing problem on marine soft bottoms. Echinoderms are known for their ability to regenerate tissue after wounding but hypoxia has a negative influence on regeneration and also on reproduction in echinoderms. We have investigated the cellular and molecular responses to wounding stress and hypoxia in the sea star Asterias rubens by using the total coelomocyte count (TCC) and the expression of heat shock proteins (HSPs). As early as 1 h after wounding, sea stars under hypoxic conditions show significantly increased TCC and, after 6 h, cell numbers increase approximately two-fold. After a 3-h hypoxia exposure of wounded animals, Western blot analysis reveals highly elevated coelomocyte cytoplasmic HSP70 expression. Non-wounded sea stars exposed to hypoxia and wounded animals kept in normoxia show enhanced HSP70 expression only after 24 h. Immunocytochemical analysis has not demonstrated any translocation of HSP70 from the cytoplasm to the nucleus. We conclude that both wounding and hypoxia elicit a stress response in sea stars and that the combined stress produces synergistic effects that may inhibit the initial processes of wound healing and regeneration. 相似文献
9.
Background
Microscopic colitis (MC) is a disease manifested by diarrhoea and is divided into collagenous and lymphocytic colitis. The aetiology is unknown, but auto-immunity is suggested. Auto-antibodies have been only rarely examined in this entity. The aim of the study was to examine the prevalence of auto-antibodies, and to examine associations between the presence of antibodies and clinical findings.Methods and Findings
Women with MC verified by biopsy and younger than 73 years, at any Department of Gastroenterology, in the district of Skåne, between 2002 and 2010 were invited to participate in this study. The patients were asked to complete both a questionnaire describing their medical history and the Gastrointestinal Symptom Rating Scale (GSRS). Blood samples were collected. Anti-nuclear antibodies (ANA), anti-neutrophil cytoplasmic antibodies (ANCA), anti-Saccharomyces cerevisiae antibodies (ASCA), and antibodies against glutamic acid decarboxylase (anti-GAD), islet antigens-like insulin 2 (anti-IA2), thyroid peroxidase (anti-TPO), and thyrotropin receptor (TRAK) were analysed. Of 240 women identified, 133 were finally included in the study, median age 63 (59–67) years. Apart from the MC diagnosis, 52% also suffered from irritable bowel syndrome, 31% from hypertension and 31% from allergy. The prevalence of ANA (14%), ASCA IgG (13%), and anti-TPO antibodies (14%) for these patients was slightly higher than for the general population, and were found together with other concomitant diseases. Patients had more of all gastrointestinal symptoms compared with norm values, irrespective of antibody expression.Conclusions
Women with MC have a slightly increased prevalence of some auto-antibodies. These antibodies are not associated with symptoms, but are expressed in patients with concomitant diseases, obscuring the pathophysiology and clinical picture of MC. 相似文献10.