全文获取类型
收费全文 | 411篇 |
免费 | 33篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 31篇 |
2012年 | 30篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 9篇 |
2008年 | 25篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1950年 | 1篇 |
排序方式: 共有444条查询结果,搜索用时 671 毫秒
391.
When the chemical cues co-occurring with prey vary in time and space, foraging predators profit from an ability to repeatedly associate chemical cues with the presence of their prey. We demonstrate the ability of a predatory arthropod (the plant-inhabiting mite, Phytoseiulus persimilis) to learn the association of a positive stimulus (herbivorous prey, Tetranychus urticae) or a negative stimulus (hunger) with a chemical cue (herbivore-induced plant volatiles or green leaf volatiles). It has been suggested that the rate at which the integration of information becomes manifest as a change in behaviour, differs between categories of natural enemies (parasitoids versus insect predators; specialist versus generalist predators). We argue that these differences do not necessarily reflect differential learning ability, but rather relate to the ecologically relevant time scale at which the biotic environment changes. 相似文献
392.
393.
Sándor Hornok Krisztina Szőke Péter Estók Aleksandra Krawczyk Anne-Jifke Haarsma Dávid Kováts Sándor A. Boldogh Pál Morandini Sándor Szekeres Nóra Takács Jenő Kontschán Marina L. Meli Isabel G. Fernández de Mera José de la Fuente Miklós Gyuranecz Kinga M. Sulyok Beatrice Weibel Enikő Gönczi Arnout de Bruin Hein Sprong Regina Hofmann-Lehmann 《Antonie van Leeuwenhoek》2018,111(9):1707-1717
In Europe, several species of bats, owls and kestrels exemplify highly urbanised, flying vertebrates, which may get close to humans or domestic animals. Bat droppings and bird pellets may have epidemiological, as well as diagnostic significance from the point of view of pathogens. In this work 221 bat faecal and 118 bird pellet samples were screened for a broad range of vector-borne bacteria using PCR-based methods. Rickettsia DNA was detected in 13 bat faecal DNA extracts, including the sequence of a rickettsial insect endosymbiont, a novel Rickettsia genotype and Rickettsia helvetica. Faecal samples of the pond bat (Myotis dasycneme) were positive for a Neorickettsia sp. and for haemoplasmas of the haemofelis group. In addition, two bird pellets (collected from a Long-eared Owl, Asio otus, and from a Common Kestrel, Falco tinnunculus) contained the DNA of a Rickettsia sp. and Anaplasma phagocytophilum, respectively. In both of these bird pellets the bones of Microtus arvalis were identified. All samples were negative for Borrelia burgdorferi s.l., Francisella tularensis, Coxiella burnetii and Chlamydiales. In conclusion, bats were shown to pass rickettsia and haemoplasma DNA in their faeces. Molecular evidence is provided for the presence of Neorickettsia sp. in bat faeces in Europe. In the evaluated regions bat faeces and owl/kestrel pellets do not appear to pose epidemiological risk from the point of view of F. tularensis, C. burnetii and Chlamydiales. Testing of bird pellets may provide an alternative approach to trapping for assessing the local occurrence of vector-borne bacteria in small mammals. 相似文献
394.
Natasja de Bruin Nerea Ferreirós Mike Schmidt Martine Hofmann Carlo Angioni Gerd Geisslinger Michael John Parnham 《Chirality》2018,30(5):632-641
Flurbiprofen (F) is a nonsteroidal anti‐inflammatory drug (NSAID) used therapeutically as the racemate of (R)‐enantiomer and (S)‐enantiomer. The inversion of RF to SF and vice versa was investigated in C57Bl/6 and SJL mice and Dark Agouti and Lewis rats. The enzyme α‐methylacyl‐CoA racemase (AMACR) is involved in the chiral inversion pathway that converts members of the 2‐arylpropionic acid NSAIDs from the R‐enantiomer to the S‐enantiomer. We studied C57Bl/6 mice deficient in AMACR postulating that they should show reduced inversion of RF to SF. In line with the data of others in mice, (R)‐inversion to (S)‐inversion was relatively high in both the C57Bl/6 and SJL mice (fraction inverted, FI = 37.7% and 24.7%, respectively). In contrast, in AMACR deficient mice, there was no measurable peak for SF after administration of RF. The results in both rat strains (Dark Agouti and Lewis rats, FI = 1.4% and 4.1%, respectively) confirm the low chiral inversion of the enantiomers of flurbiprofen in the rat, as observed by other authors in the Sprague‐Dawley strain (<5%). From the present results, we conclude that for the study of flurbiprofen enantiomers, the rat is more suitable than the mouse as a model for the human in which (R)‐inversion to (S)‐inversion is negligible. 相似文献
395.
Christiaan L. Slim Francisco Lázaro-Diéguez Marjolein Bijlard Mathilda J. M. Toussaint Alain de Bruin Quansheng Du Anne Müsch Sven C. D. van IJzendoorn 《PLoS biology》2013,11(12)
The development and maintenance of polarized epithelial tissue requires a tightly controlled orientation of mitotic cell division relative to the apical polarity axis. Hepatocytes display a unique polarized architecture. We demonstrate that mitotic hepatocytes asymmetrically segregate their apical plasma membrane domain to the nascent daughter cells. The non-polarized nascent daughter cell can form a de novo apical domain with its new neighbor. This asymmetric segregation of apical domains is facilitated by a geometrically distinct “apicolateral” subdomain of the lateral surface present in hepatocytes. The polarity protein partitioning-defective 1/microtubule-affinity regulating kinase 2 (Par1b/MARK2) translates this positional landmark to cortical polarity by promoting the apicolateral accumulation of Leu-Gly-Asn repeat-enriched protein (LGN) and the capture of nuclear mitotic apparatus protein (NuMA)–positive astral microtubules to orientate the mitotic spindle. Proliferating hepatocytes thus display an asymmetric inheritance of their apical domains via a mechanism that involves Par1b and LGN, which we postulate serves the unique tissue architecture of the developing liver parenchyma. 相似文献
396.
Ruben G. Duijnhoven Sabine M. J. M. Straus June M. Raine Anthonius de Boer Arno W. Hoes Marie L. De Bruin 《PLoS medicine》2013,10(3)
Background
At the time of approval of a new medicine, there are few long-term data on the medicine''s benefit–risk balance. Clinical trials are designed to demonstrate efficacy, but have major limitations with regard to safety in terms of patient exposure and length of follow-up. This study of the number of patients who had been administered medicines at the time of medicine approval by the European Medicines Agency aimed to determine the total number of patients studied, as well as the number of patients studied long term for chronic medication use, compared with the International Conference on Harmonisation''s E1 guideline recommendations.Methods and Findings
All medicines containing new molecular entities approved between 2000 and 2010 were included in the study, including orphan medicines as a separate category. The total number of patients studied before approval was extracted (main outcome). In addition, the number of patients with long-term use (6 or 12 mo) was determined for chronic medication. 200 unique new medicines were identified: 161 standard and 39 orphan medicines. The median total number of patients studied before approval was 1,708 (interquartile range [IQR] 968–3,195) for standard medicines and 438 (IQR 132–915) for orphan medicines. On average, chronic medication was studied in a larger number of patients (median 2,338, IQR 1,462–4,135) than medication for intermediate (878, IQR 513–1,559) or short-term use (1,315, IQR 609–2,420). Safety and efficacy of chronic use was studied in fewer than 1,000 patients for at least 6 and 12 mo in 46.4% and 58.3% of new medicines, respectively. Among the 84 medicines intended for chronic use, 68 (82.1%) met the guideline recommendations for 6-mo use (at least 300 participants studied for 6 mo and at least 1,000 participants studied for any length of time), whereas 67 (79.8%) of the medicines met the criteria for 12-mo patient exposure (at least 100 participants studied for 12 mo).Conclusions
For medicines intended for chronic use, the number of patients studied before marketing is insufficient to evaluate safety and long-term efficacy. Both safety and efficacy require continued study after approval. New epidemiologic tools and legislative actions necessitate a review of the requirements for the number of patients studied prior to approval, particularly for chronic use, and adequate use of post-marketing studies. Please see later in the article for the Editors'' Summary 相似文献397.
C. A.G. Haasnoot S. H. de Bruin R. G. Berendsen H. G.J.M. Janssen T. J.J. Binnendijk C. W. Hilbers 《Journal of biomolecular structure & dynamics》2013,31(1):115-129
Abstract The hairpin-to-coil equilibrium of the hexadecadeoxynucleotide d(ATCCTATTTTTAGGAT) was extensively studied by means of NMR, T-jump and UV. The thermodynamic and kinetic parameters for this equilibrium were determined, yielding a consistent picture of the dynamical behavior of this hairpin structure, which is shown to be a clear example of a situation in which the linebroadening of the imino proton resonances is not determined by the lifetime of the double helix. A comparative study of the homologous hairpins in which the size of the loop was elongated from 4 to 7 thymidine residues shows a monotonous decrease in Tm for the hairpin-to-coil transitions. This finding is in contrast with the view that the stability of hairpins reaches a maximum with a loop size of 6–7 residues. The NMR results indicate that the accessibility of the thymine bases in the loop towards solvent molecules or complementary nucleotides greatly depends on the size of the loop. 相似文献
398.
Samir Câmara Magalhães Carlos Vitorino Souza Tiago Rocha Dias Pedro Felipe Carvalhedo de Bruin 《Chronobiology international》2013,30(5):917-924
Parkinson's disease (PD) is a chronic progressive motor disorder that may present with a spectrum of symptoms and disease severity. Therapy is frequently associated with motor fluctuations and dyskinesias; therefore, monitoring of motor fluctuations and daily abilities is important for adequate management. The Social Rhythm Metric (SRM) is a diary‐like questionnaire that quantifies the extent to which a person's life is regular vs. irregular on a daily basis with respect to event timing. Lifestyle regularity has been assessed by the SRM in other clinical situations. The aim of this study was to evaluate lifestyle regularity in a population with PD using the SRM and its relationship to clinical and therapeutic factors. Twenty‐eight consecutive patients with PD and 14 control subjects were studied. Severity of motor dysfunction was evaluated with the Unified Parkinson's Disease Rating Scale (UPDRS). Depressive symptoms were assessed with the Montgomery Asberg Depressive Rating Scale (MADRS), sleep quality with the Pittsburgh Sleep Quality Index (PSQI), and subjective daytime sleepiness with the Epworth sleepiness scale. Daily lifestyle regularity was assessed by the SRM for 2 weeks. Patients with PD had lower SRM scores than controls, and those with motor fluctuations had even lower scores (p=0.04). Patients with motor fluctuations showed more clinical disability (p=0.01), a worse quality of sleep (p=0.02), and more depressive symptoms (p=0.02). SRM results were correlated with PSQI values (p=0.016). Our findings show that the regularity of daily activities as measured by the SRM is disorganized in patients with PD and that this irregularity is related to sleep quality. 相似文献
399.
Jiaqiang Cai Xavier Fradera Mario van Zeeland Maureen Dempster Kenneth S. Cameron D. Jonathan Bennett John Robinson Lucy Popplestone Mark Baugh Paul Westwood John Bruin William Hamilton Emma Kinghorn Clive Long Joost C.M. Uitdehaag 《Bioorganic & medicinal chemistry letters》2010,20(15):4507-4510
Using computer aided modelling studies, a new extended P2/S2 interaction was identified. This extended region can accommodate a variety of functional groups, such as aryls and basic amines. It was discovered that the N3 nitrogen of the pyrimidine-2-carbonitrile is critical for its cathepsin cysteine protease inhibition. N1 nitrogen also contributes to the inhibitory activity, but to a very limited degree. An ‘in situ double activation’ mechanism was proposed to explain these results. 相似文献
400.
Manon JM van Oosten Radboud JEM Dolhain Jan W Koper Elisabeth FC van Rossum Marieke Emonts Khik H Han Jacques MGW Wouters Johanne MW Hazes Steven WJ Lamberts Richard A Feelders 《Arthritis research & therapy》2010,12(4):R159