全文获取类型
收费全文 | 666篇 |
免费 | 43篇 |
专业分类
709篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 32篇 |
2017年 | 25篇 |
2016年 | 43篇 |
2015年 | 48篇 |
2014年 | 48篇 |
2013年 | 25篇 |
2012年 | 75篇 |
2011年 | 49篇 |
2010年 | 36篇 |
2009年 | 24篇 |
2008年 | 26篇 |
2007年 | 32篇 |
2006年 | 22篇 |
2005年 | 27篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 5篇 |
1966年 | 1篇 |
排序方式: 共有709条查询结果,搜索用时 15 毫秒
21.
Massive excretion of calcium oxalate from late prepupal salivary glands of Drosophila melanogaster demonstrates active nephridial‐like anion transport
下载免费PDF全文
![点击此处可从《Development, growth & differentiation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Robert Farkaš Ludmila Pečeňová Lucia Mentelová Milan Beňo Denisa Beňová‐Liszeková Silvia Mahmoodová Václav Tejnecký Otakar Raška Pavel Juda Silvie Svidenská Matúš Hornáček Bruce A. Chase Ivan Raška 《Development, growth & differentiation》2016,58(6):562-574
The Drosophila salivary glands (SGs) were well known for the puffing patterns of their polytene chromosomes and so became a tissue of choice to study sequential gene activation by the steroid hormone ecdysone. One well‐documented function of these glands is to produce a secretory glue, which is released during pupariation to fix the freshly formed puparia to the substrate. Over the past two decades SGs have been used to address specific aspects of developmentally‐regulated programmed cell death (PCD) as it was thought that they are doomed for histolysis and after pupariation are just awaiting their fate. More recently, however, we have shown that for the first 3–4 h after pupariation SGs undergo tremendous endocytosis and vacuolation followed by vacuole neutralization and membrane consolidation. Furthermore, from 8 to 10 h after puparium formation (APF) SGs display massive apocrine secretion of a diverse set of cellular proteins. Here, we show that during the period from 11 to 12 h APF, the prepupal glands are very active in calcium oxalate (CaOx) extrusion that resembles renal or nephridial excretory activity. We provide genetic evidence that Prestin, a Drosophila homologue of the mammalian electrogenic anion exchange carrier SLC26A5, is responsible for the instantaneous production of CaOx by the late prepupal SGs. Its positive regulation by the protein kinases encoded by fray and wnk lead to increased production of CaOx. The formation of CaOx appears to be dependent on the cooperation between Prestin and the vATPase complex as treatment with bafilomycin A1 or concanamycin A abolishes the production of detectable CaOx. These data demonstrate that prepupal SGs remain fully viable, physiologically active and engaged in various cellular activities at least until early pupal period, that is, until moments prior to the execution of PCD. 相似文献
22.
Jaime Resano‐Mayor Joan Real Marcos Moleón José Antonio Sánchez‐Zapata Luís Palma Antonio Hernández‐Matías 《Oikos》2016,125(2):262-270
Understanding the mechanisms that shape animal population dynamics is of fundamental interest in ecology, evolution and conservation biology. Food supply is an important limiting factor in most animal populations and may have demographic consequences. Optimal foraging theory predicts greater consumption of preferred prey and less diet diversity when food is abundant, which may benefit key fitness parameters such as productivity and survival. Nevertheless, the correspondence between individual resource use and demographic processes in populations of avian predators inhabiting large geographic areas remains largely unexplored, particularly in complex ecosystems such as those of the Mediterranean basin. Based on a long‐term monitoring program of the diet and demography of Bonelli's eagle Aquila fasciata in western Europe, here we test the hypothesis that a predator's diet is correlated to its breeding productivity and survival at both the territorial and population levels, and ultimately to its population growth rate. At the territorial level, we found that productivity increased with greater consumption of European rabbits Oryctolagus cuniculus, the Bonelli's eagle's preferred prey, and pigeons, an important alternative prey for this predator. The survival of territorial pairs was negatively affected by higher diet diversity, which probably reflected the inability to find sufficient high quality prey. Diet effects at the population level were similar but more noticeable than at the territorial level, i.e. a greater consumption of rabbits, together with lesser consumption of small‐to‐medium avian species (‘other birds’; non‐preferred prey), increased productivity, while greater diet diversity and lower consumption of rabbits was associated with reduced survival and population growth rate. Overall, our study illustrates how the diet of a predator species can be closely related to key individual vital rates, which, in turn, leave a measurable fingerprint on population dynamics within and among populations across large spatial scales. 相似文献
23.
According to receptor theory, the effect of a ligand depends on the amount of agonist–receptor complex. Therefore, changes in receptor abundance should have quantitative effects. However, the response to pheromone in Saccharomyces cerevisiae is robust (unaltered) to increases or reductions in the abundance of the G‐protein‐coupled receptor (GPCR), Ste2, responding instead to the fraction of occupied receptor. We found experimentally that this robustness originates during G‐protein activation. We developed a complete mathematical model of this step, which suggested the ability to compute fractional occupancy depends on the physical interaction between the inhibitory regulator of G‐protein signaling (RGS), Sst2, and the receptor. Accordingly, replacing Sst2 by the heterologous hsRGS4, incapable of interacting with the receptor, abolished robustness. Conversely, forcing hsRGS4:Ste2 interaction restored robustness. Taken together with other results of our work, we conclude that this GPCR pathway computes fractional occupancy because ligand‐bound GPCR–RGS complexes stimulate signaling while unoccupied complexes actively inhibit it. In eukaryotes, many RGSs bind to specific GPCRs, suggesting these complexes with opposing activities also detect fraction occupancy by a ratiometric measurement. Such complexes operate as push‐pull devices, which we have recently described. 相似文献
24.
Michal Hlodák Peter Matúš Lucia Kořenková 《International journal of phytoremediation》2016,18(2):195-199
Heavy metal phytotoxicity assessments usually use soluble metal compounds in spiked soils to evaluate metal bioaccumulation, growth inhibition and adverse effects on physiological parameters. However, exampling mercury phytotoxicity for barley (Hordeum vulgare) this paper highlights unsuitability of this experimental approach. Mercury(II) in spiked soils is extremely bioavailable, and there experimentally determined bioaccumulation is significantly higher compared to reported mercury bioaccumulation efficiency from soils collected from mercury-polluted areas. Our results indicate this is not affected by soil sorption capacity, thus soil ageing and formation of more stable mercuric complexes with soil fractions is necessary for reasonable metal phytotoxicity assessments. 相似文献
25.
26.
Oulehle Filip Wright Richard F. Svoboda Miroslav Bače Radek Matějka Karel Kaňa Jiří Hruška Jakub Couture Raoul-Marie Kopáček Jiří 《Ecosystems》2019,22(4):725-741
Ecosystems - Forest ecosystems worldwide are subjected to human-induced stressors, including eutrophication and acidification, and to natural disturbances (for example, insect infestation,... 相似文献
27.
28.
The present study was designed 1) to examine the influence of cumulus cells, ovary storage time and oocyte size on the penetrability of immature pig oocytes, and 2) to investigate the effect of 2 methods of treating the semen from different boars on the inter-assay variability of homologous in vitro penetration tests of boar sperm fertility. In Experiment 1, cumulus oocyte complexes, oocytes with spontaneous loss of the cumulus cells during collection, and oocytes mechanically stripped of cumulus cells were used. No differences were observed in oocyte penetrability among the 3 types of oocyte, although mechanical removal of the cumulus caused an increase (P < 0.005) in the degeneration rate compared with the other oocyte types. In Experiment 2, the oocytes were recovered from ovaries kept in PBS (30 degrees C) for 2, 4 or 6 h after slaughter of prepuberal gilts. Ovary storage did not modify the penetrability of oocytes but increased (P < 0.02) their degeneration rates. In Experiment 3, the diameters of fresh oocytes were determined after co-incubation with spermatozoa. They were classified into 4 groups according to diameter: A) < 105 microm, B) 105-115 microm, C) 116-120 microm and D) > 120 microm. Oocytes from Groups C and D exhibited higher (P < 0.05) penetrability than oocytes from the other groups. In Experiment 4, stored, diluted spermatozoa from 4 boars were pretreated by centrifugation at 50 x g for 3 min and subsequent concentration of the supernatants at 1,200 x g for 3 min. The pellets were treated (washed twice and preincubated for 40 minutes) before co-incubation with immature oocytes or used directly as untreated samples (unwashed and non-preincubated). A boar effect (P < 0.001) was evident for the parameters of in vitro penetration, independently of sperm treatment. When the oocytes were inseminated with untreated spermatozoa, the effects of the replicate and the boar-by-replicate interaction on the variability in oocyte penetrability were not significant. The results of this study indicate that the use of standardized immature pig oocytes and stored untreated, diluted spermatozoa can provide a useful method for optimizing the homologous in vitro penetration (hIVP) assay of boar fertility. 相似文献
29.
Microarrays can provide genome-wide expression patterns for various cancers, especially for tumor sub-types that may exhibit substantially different patient prognosis. Using such gene expression data, several approaches have been proposed to classify tumor sub-types accurately. These classification methods are not robust, and often dependent on a particular training sample for modelling, which raises issues in utilizing these methods to administer proper treatment for a future patient. We propose to construct an optimal, robust prediction model for classifying cancer sub-types using gene expression data. Our model is constructed in a step-wise fashion implementing cross-validated quadratic discriminant analysis. At each step, all identified models are validated by an independent sample of patients to develop a robust model for future data. We apply the proposed methods to two microarray data sets of cancer: the acute leukemia data by Golub et al. and the colon cancer data by Alon et al. We have found that the dimensionality of our optimal prediction models is relatively small for these cases and that our prediction models with one or two gene factors outperforms or has competing performance, especially for independent samples, to other methods based on 50 or more predictive gene factors. The methodology is implemented and developed by the procedures in R and Splus. The source code can be obtained at http://hesweb1.med.virginia.edu/bioinformatics. 相似文献
30.
Composting technique was used for bioremediation of industrial soil originating from a former tar-contaminated site. The composting
process was regulated by aeration to keep optimal temperature gradient and concentrations of O2 and CO2 inside the composting pile. The efficiency of bioremediation was evaluated by performing analysis of 11 individual three-
to six-ring unsubstituted aromatic hydrocarbons (PAH) and estimating of changes in ecotoxicity of the contaminated soil. After
42 d of composting, PAH with 3–4 rings were removed from 42 to 68%, other higher-molar mass PAH from 35 to 57%. Additional
100 d of compost maturation in open-air field did not result in a further decrease of PAH. Ecotoxicity tests performed with
bioluminescent bacteriaVibrio fischerii showed a decrease in toxicity both after composting and maturation phases. However, toxicity tests on mustard-seed germination
did not reveal any significant changes during composting and maturation phases. 相似文献