全文获取类型
收费全文 | 5444篇 |
免费 | 451篇 |
国内免费 | 4篇 |
出版年
2023年 | 32篇 |
2022年 | 47篇 |
2021年 | 106篇 |
2020年 | 75篇 |
2019年 | 87篇 |
2018年 | 107篇 |
2017年 | 96篇 |
2016年 | 145篇 |
2015年 | 237篇 |
2014年 | 248篇 |
2013年 | 315篇 |
2012年 | 411篇 |
2011年 | 378篇 |
2010年 | 298篇 |
2009年 | 235篇 |
2008年 | 343篇 |
2007年 | 320篇 |
2006年 | 281篇 |
2005年 | 305篇 |
2004年 | 249篇 |
2003年 | 225篇 |
2002年 | 235篇 |
2001年 | 77篇 |
2000年 | 50篇 |
1999年 | 63篇 |
1998年 | 80篇 |
1997年 | 48篇 |
1996年 | 66篇 |
1995年 | 47篇 |
1994年 | 45篇 |
1993年 | 47篇 |
1992年 | 44篇 |
1991年 | 43篇 |
1990年 | 29篇 |
1989年 | 25篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 19篇 |
1985年 | 38篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 28篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1974年 | 16篇 |
1973年 | 21篇 |
排序方式: 共有5899条查询结果,搜索用时 765 毫秒
171.
172.
Robin Somers-Yeates David Hodgson Peter K. McGregor Adrian Spalding Richard H. ffrench-Constant 《Biology letters》2013,9(4)
With moth declines reported across Europe, and parallel changes in the amount and spectra of street lighting, it is important to understand exactly how artificial lights affect moth populations. We therefore compared the relative attractiveness of shorter wavelength (SW) and longer wavelength (LW) lighting to macromoths. SW light attracted significantly more individuals and species of moth, either when used alone or in competition with LW lighting. We also found striking differences in the relative attractiveness of different wavelengths to different moth groups. SW lighting attracted significantly more Noctuidae than LW, whereas both wavelengths were equally attractive to Geometridae. Understanding the extent to which different groups of moth are attracted to different wavelengths of light will be useful in determining the impact of artificial light on moth populations. 相似文献
173.
Rida Mourtada Sonali B. Fonseca Simon P. Wisnovsky Mark P. Pereira Xiaoming Wang Rose Hurren Jeremy Parfitt Lesley Larsen Robin A. J. Smith Michael P. Murphy Aaron D. Schimmer Shana O. Kelley 《PloS one》2013,8(4)
We have successfully delivered a reactive alkylating agent, chlorambucil (Cbl), to the mitochondria of mammalian cells. Here, we characterize the mechanism of cell death for mitochondria-targeted chlorambucil (mt-Cbl) in vitro and assess its efficacy in a xenograft mouse model of leukemia. Using a ρ° cell model, we show that mt-Cbl toxicity is not dependent on mitochondrial DNA damage. We also illustrate that re-targeting Cbl to mitochondria results in a shift in the cell death mechanism from apoptosis to necrosis, and that this behavior is a general feature of mitochondria-targeted Cbl. Despite the change in cell death mechanisms, we show that mt-Cbl is still effective in vivo and has an improved pharmacokinetic profile compared to the parent drug. These findings illustrate that mitochondrial rerouting changes the site of action of Cbl and also alters the cell death mechanism drastically without compromising in vivo efficacy. Thus, mitochondrial delivery allows the exploitation of Cbl as a promiscuous mitochondrial protein inhibitor with promising therapeutic potential. 相似文献
174.
Jan Mládek Pavla Mládková Pavla Hejcmanová Miroslav Dvorsky Vilém Pavlu Francesco De Bello Martin Duchoslav Michal Hejcman Robin J. Pakeman 《PloS one》2013,8(7)
Background
Current plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.Methodology/Findings
We assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.Conclusions
Our findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level. 相似文献175.
Cleopatra K. Mugyenyi Salenna R. Elliott Fiona J. McCallum Robin F. Anders Kevin Marsh James G. Beeson 《PloS one》2013,8(7)
Background
Antibodies to P. falciparum apical membrane protein 1 (AMA1) may contribute to protective immunity against clinical malaria by inhibiting blood stage growth of P. falciparum, and AMA1 is a leading malaria vaccine candidate. Currently, there is limited knowledge of the acquisition of strain-specific and cross-reactive antibodies to AMA1 in humans, or the acquisition of invasion-inhibitory antibodies to AMA1.Methodology/Findings
We examined the acquisition of human antibodies to specific polymorphic invasion-inhibitory and non-inhibitory AMA1 epitopes, defined by the monoclonal antibodies 1F9 and 2C5, respectively. Naturally acquired antibodies were measured in cohorts of Kenyan children and adults. Antibodies to the invasion-inhibitory 1F9 epitope and non-inhibitory 2C5 epitope were measured indirectly by competition ELISA. Antibodies to the 1F9 and 2C5 epitopes were acquired by children and correlated with exposure, and higher antibody levels and prevalence were observed with increasing age and with active P. falciparum infection. Of note, the prevalence of antibodies to the inhibitory 1F9 epitope was lower than antibodies to AMA1 or the 2C5 epitope. Antibodies to AMA1 ectodomain, the 1F9 or 2C5 epitopes, or a combination of responses, showed some association with protection from P. falciparum malaria in a prospective longitudinal study. Furthermore, antibodies to the invasion-inhibitory 1F9 epitope were positively correlated with parasite growth-inhibitory activity of serum antibodies.Conclusions/Significance
Individuals acquire antibodies to functional, polymorphic epitopes of AMA1 that may contribute to protective immunity, and these findings have implications for AMA1 vaccine development. Measuring antibodies to the 1F9 epitope by competition ELISA may be a valuable approach to assessing human antibodies with invasion-inhibitory activity in studies of acquired immunity and vaccine trials of AMA1. 相似文献176.
Robin Lombard Emilie Doz Florence Carreras Mathieu Epardaud Yves Le Vern Dominique Buzoni-Gatel Nathalie Winter 《PloS one》2016,11(2)
During chronic infection with Mycobacterium tuberculosis (Mtb), bacilli multiplication is constrained within lung granulomas until excessive inflammation destroys the lung. Neutrophils are recruited early and participate in granuloma formation, but excessive neutrophilia exacerbates the tuberculosis disease. Neutrophils thus appear as potential targets for therapeutic interventions, especially in patients for whom no antibiotic treatment is possible. Signals that regulate neutrophil recruitment to the lung during mycobacterial infection need to be better understood. We demonstrated here, in the mouse model, that neutrophils were recruited to the lung in two waves after intranasal infection with virulent Mtb or the live attenuated vaccine strain Bacillus Calmette Guérin (BCG). A first wave of neutrophils was swiftly recruited, followed by a subsequent adaptive wave that reached the lung together with IFN-γ- and IL-17A-producing T cells. Interestingly, the second neutrophil wave did not participate to mycobacteria control in the lung and established contacts with T cells. The adaptive wave was critically dependent on the expression of IL-17RA, the receptor for IL-17A, expressed in non-hematopoietic cells. In absence of this receptor, curtailed CXCL-1 and 5 production in the lung restrained neutrophil recruitment. CXCL-1 and 5 instillation reconstituted lung neutrophil recruitment in BCG-infected IL17RA-/- mice. 相似文献
177.
The complexity of behavioural interactions in predator-prey systems has recently begun to capture trait-effects, or non-lethal effects, of predators on prey via induced behavioural changes. Non-lethal predation effects play crucial roles in shaping population and community dynamics, particularly by inducing changes to foraging, movement and reproductive behaviours of prey. Prey exhibit trade-offs in behaviours while minimizing predation risk. We use a novel evolutionary ecosystem simulation EcoSim to study such behavioural interactions and their effects on prey populations, thereby addressing the need for integrating multiple layers of complexity in behavioural ecology. EcoSim allows complex intra- and inter-specific interactions between behaviourally and genetically unique individuals called predators and prey, as well as complex predator-prey dynamics and coevolution in a tri-trophic and spatially heterogeneous world. We investigated the effects of predation risk on prey energy budgets and fitness. Results revealed that energy budgets, life history traits, allocation of energy to movements and fitness-related actions differed greatly between prey subjected to low-predation risk and high-predation risk. High-predation risk suppressed prey foraging activity, increased total movement and decreased reproduction relative to low-risk. We show that predation risk alone induces behavioural changes in prey which drastically affect population and community dynamics, and when interpreted within the evolutionary context of our simulation indicate that genetic changes accompanying coevolution have long-term effects on prey adaptability to the absence of predators. 相似文献
178.
S. Samoudi D. Latour J. Robin M. Sabart B. Misson H. Ait Hammou Kh. Mouhri M. Loudiki 《Contemporary Problems of Ecology》2016,9(5):554-562
The first results of the horizontal distribution of the cell abundance and toxicity of Microcystis in the hypereutrophic Moroccan reservoir Lalla Takerkoust are reported. An unexpected spatio-temporal heterogeneity has been shown between Microcystis abundance and microcystins concentrations. The principal determining factors were analyzed in order to identify the most likely sites for the proliferation and/or accumulation of Microcystis in this reservoir. The horizontal heterogeneity seems to be mainly influenced by the wind direction and inflows. The results can serve as reference data for monitoring cyanobacterial water blooms and associated cyanotoxins in the lake. 相似文献
179.
Memories compete for retrieval when they are related to a common retrieval cue. Previous research has shown that retrieval of a target memory may lead to subsequent retrieval-induced forgetting (RIF) of currently irrelevant competing memories. In the present study, we investigated the time course of competitive semantic retrieval and examined the neurocognitive mechanisms underlying RIF. We contrasted two theoretical accounts of RIF by examining a critical aspect of this memory phenomenon, namely the extent to which it depends on successful retrieval of the target memory. Participants first studied category-exemplar word-pairs (e.g. Fruit—Apple). Next, we recorded electrophysiological measures of brain activity while the participants performed a competitive semantic cued-recall task. In this task, the participants were provided with the studied categories but they were instructed to retrieve other unstudied exemplars (e.g. Fruit—Ma__?). We investigated the event-related potential (ERP) correlates of retrieval success by comparing ERPs from successful and failed retrieval trials. To isolate the ERP correlates of continuous retrieval attempts from the ERP correlates of retrieval success, we included an impossible retrieval condition, with incompletable word-stem cues (Drinks—Wy__) and compared it with a non-retrieval presentation baseline condition (Occupation—Dentist). The participants’ memory for all the studied exemplars was tested in the final phase of the experiment. Taken together, the behavioural results suggest that RIF is independent of target retrieval. Beyond investigating the mechanisms underlying RIF, the present study also elucidates the temporal dynamics of semantic cued-recall by isolating the ERP correlates of retrieval attempt and retrieval success. The ERP results revealed that retrieval attempt is reflected in a late posterior negativity, possibly indicating construction of candidates for completing the word-stem cue and retrieval monitoring whereas retrieval success was reflected in an anterior positive slow wave. 相似文献
180.
Araminta E. W. Ledger Erica D. Scurr Julie Hughes Alison Macdonald Toni Wallace Karen Thomas Robin Wilson Martin O. Leach Maria A. Schmidt 《PloS one》2016,11(3)