全文获取类型
收费全文 | 923篇 |
免费 | 80篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 13篇 |
2020年 | 4篇 |
2019年 | 16篇 |
2018年 | 5篇 |
2017年 | 16篇 |
2016年 | 26篇 |
2015年 | 32篇 |
2014年 | 35篇 |
2013年 | 52篇 |
2012年 | 55篇 |
2011年 | 62篇 |
2010年 | 54篇 |
2009年 | 47篇 |
2008年 | 56篇 |
2007年 | 60篇 |
2006年 | 53篇 |
2005年 | 60篇 |
2004年 | 63篇 |
2003年 | 54篇 |
2002年 | 30篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 16篇 |
1997年 | 18篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有1003条查询结果,搜索用时 93 毫秒
61.
Guillaume Le Flohic Peggy Motsch Hélène DeNys Simon Childs Amos Courage Tony King 《PloS one》2015,10(3)
Rehabilitation of animals followed by reintroduction into the wild can benefit conservation by supplementing depleted wild populations or reintroducing a species in an area where it has been extirpated or become extinct. The western lowland gorilla (WLG, Gorilla g. gorilla) is persistently poached; infants are often illegally traded and used as pets. Some are confiscated and rehabilitated, then kept in sanctuaries or reintroduced into the wild. Prior to reintroduction, the ability of the orphans to survive independently in their environment needs to be assessed. Here, we performed a multivariate analysis, including diet composition, activity-budget, and pattern of strata using of a group of five juvenile WLG in the process of rehabilitation and distinguished three sub-periods of ecological significance: the high furgivory period, the Dialium fruits consumption period, and the high folivory period. The consequences of these variations on their well-being (play behaviour) and the group cohesion (spatial proximity and social interactions) were examined. Like wild WLGs, diets shifted seasonally from frugivorous to folivorous, while the same staple foods were consumed and large amounts of Dialium fruits were seasonally gathered high in trees. When succulent fruit intake was the highest, thus providing high energy from sugar, juveniles spent less time feeding, more time playing and group cohesion was the highest. Conversely, the cohesion decreased with increasing folivory, individuals spent more time feeding and less time playing together. Nonetheless, the group cohesion also decreased after the death of one highly social, wild-born orphan. This may underscore the importance of skilled individuals in the cohesion and well-being of the entire group and, ultimately, to rehabilitation success. This study evaluates the rehabilitation success with regards to the methods used and highlights the need to consider a set of individual and environmental factors for enhancing rehabilitation while preserving the local biodiversity and individual well-being. 相似文献
62.
Julie Hoover-Fong Nara Sobreira Julie Jurgens Peggy Modaff Carrie Blout Ann Moser Ok-Hwa Kim Tae-Joon Cho Sung?Yoon Cho Sang?Jin Kim Dong-Kyu Jin Hiroshi Kitoh Woong-Yang Park Hua Ling Kurt?N. Hetrick Kimberly?F. Doheny David Valle Richard?M. Pauli 《American journal of human genetics》2014,94(1):105-112
63.
64.
Novel tumour-specific promoters for transcriptional targeting of hepatocellular carcinoma by herpes simplex virus vectors 总被引:1,自引:0,他引:1
65.
66.
Extreme population fluctuations, or outbreaks, are driven by interacting processes that are often more complex than isolated changes in consumer or resource control. Blooms of the macroalga Caulerpa sertularioides in the eastern tropical Pacific overgrew and killed reef-building corals, with blooms onto reefs corresponding to cool La Niña phases of inter-decadal fluctuations of the El Niño–Southern Oscillation. We quantified factors responsible for the maintenance of C. sertularioides patches in off-reef areas, namely an associational mutualism with an epiphytic cyanobacteria (Lyngbya majuscula), coupled with spatial refuges at the scales of individual thalli and habitat. Maintenance of near reef algal populations with a strong response to nutrient addition showed that these populations were primed to bloom onto reefs in response to enhanced nutrient delivery, such as those potentially associated with La Niña conditions. However, our experiments demonstrated that no single factor related to consumer or resource control was likely to stimulate bloom formation in isolation. Rather, we propose a novel model of reef bloom formation where off-reef blooms are sustained by processes reducing consumer control, and then bloom onto reefs through an interaction between increased allochthonous nutrient input and an uncoupling of consumer control by an association with epiphytic cyanobacteria. 相似文献
67.
Kaufman MG Pelz-Stelinski KS Yee DA Juliano SA Ostrom PH Walker ED 《Ecological Entomology》2010,35(5):586-593
1. Detritus that forms the basis for mosquito production in tree hole ecosystems can vary in type and timing of input. We investigated the contributions of plant- and animal-derived detritus to the biomass of Aedes triseriatus (Say) pupae and adults by using stable isotope ((15)N and (13)C) techniques in lab experiments and field collections.2. Lab-reared mosquito isotope values reflected their detrital resource base, providing a clear distinction between mosquitoes reared on plant or animal detritus.3. Isotope values from field-collected pupae were intermediate between what would be expected if a single (either plant or animal) detrital source dominated the resource base. However, mosquito isotope values clustered most closely with plant-derived values, and a mixed feeding model analysis indicated tree floral parts contributed approximately 80% of mosquito biomass. The mixed model also indicated that animal detritus contributed approximately 30% of mosquito tissue nitrogen.4. Pupae collected later in the season generally had isotope values that were consistent with an increased contribution from animal detritus, suggesting this resource became more nutritionally important for mosquitoes as plant inputs declined over the summer. 相似文献
68.
Coppieters K Van Beneden K Jacques P Dewint P Vervloet A Vander Cruyssen B Van Calenbergh S Chen G Franck RW Verbruggen G Deforce D Matthys P Tsuji M Rottiers P Elewaut D 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(4):2300-2309
The glycosphingolipid alpha-galactosylceramide (alpha-GalCer) has been shown to be a potent activator of invariant NKT (iNKT) cells, rapidly inducing large amounts of both Th1 and Th2 cytokines upon injection in mice. The C-glycoside analog of alpha-GalCer (alpha-C-GalCer), by contrast, results in an enhanced Th1-type response upon activation of iNKT cells. We administered a single dose of these Ags to DBA/1 mice during the early induction phase of collagen-induced arthritis and demonstrated therapeutic efficacy of alpha-GalCer when administered early rather than late during the disease. Surprisingly, the Th1-polarizing analog alpha-C-GalCer also conferred protection. Furthermore, a biphasic role of IFN-gamma in the effect of iNKT cell stimulation was observed. Whereas in vivo neutralization of IFN-gamma release induced by either alpha-GalCer or alpha-C-GalCer early during the course of disease resulted in partial improvement of clinical arthritis symptoms, blockade of IFN-gamma release later on resulted in a more rapid onset of arthritis. Although no phenotypic changes in conventional T cells, macrophages, or APCs could be detected, important functional differences in T cell cytokine production in serum were observed upon polyclonal T cell activation, 2 wk after onset of arthritis. Whereas alpha-GalCer-treated mice produced significantly higher amounts of IL-10 upon systemic anti-CD3 stimulation compared with PBS controls, T cells from alpha-C-GalCer-treated mice, by contrast, produced substantially lower levels of cytokines, suggesting the involvement of different protective mechanisms. In conclusion, these findings suggest long-term, ligand-specific, time-dependent, and partially IFN-gamma-dependent immunomodulatory effects of iNKT cells in collagen-induced arthritis. 相似文献
69.
Distinct functions of the Drosophila Nup153 and Nup214 FG domains in nuclear protein transport 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sabri N Roth P Xylourgidis N Sadeghifar F Adler J Samakovlis C 《The Journal of cell biology》2007,178(4):557-565
The phenylanine-glycine (FG)-rich regions of several nucleoporins both bind to nuclear transport receptors and collectively provide a diffusion barrier to the nuclear pores. However, the in vivo roles of FG nucleoporins in transport remain unclear. We have inactivated 30 putative nucleoporins in cultured Drosophila melanogaster S2 cells by RNA interference and analyzed the phenotypes on importin alpha/beta-mediated import and CRM1-dependent protein export. The fly homologues of FG nucleoporins Nup358, Nup153, and Nup54 are selectively required for import. The FG repeats of Nup153 are necessary for its function in transport, whereas the remainder of the protein maintains pore integrity. Inactivation of the CRM1 cofactor RanBP3 decreased the nuclear accumulation of CRM1 and protein export. We report a surprisingly antagonistic relationship between RanBP3 and the Nup214 FG region in determining CRM1 localization and its function in protein export. Our data suggest that peripheral metazoan FG nucleoporins have distinct functions in nuclear protein transport events. 相似文献
70.
Angiogenesis is not impaired in connective tissue growth factor (CTGF) knock-out mice. 总被引:3,自引:0,他引:3
Esther J Kuiper Peggy Roestenberg Christoph Ehlken Vincent Lambert Henny Bloys van Treslong-de Groot Karen M Lyons Hans-Jürgen T Agostini Jean-Marie Rakic Ingeborg Klaassen Cornelis J F Van Noorden Roel Goldschmeding Reinier O Schlingemann 《The journal of histochemistry and cytochemistry》2007,55(11):1139-1147
Connective tissue growth factor (CTGF) is a member of the CCN family of growth factors. CTGF is important in scarring, wound healing, and fibrosis. It has also been implicated to play a role in angiogenesis, in addition to vascular endothelial growth factor (VEGF). In the eye, angiogenesis and subsequent fibrosis are the main causes of blindness in conditions such as diabetic retinopathy. We have applied three different models of angiogenesis to homozygous CTGF(-/-) and heterozygous CTGF(+/-) mice to establish involvement of CTGF in neovascularization. CTGF(-/-) mice die around birth. Therefore, embryonic CTGF(-/-), CTGF(+/-), and CTGF(+/+) bone explants were used to study in vitro angiogenesis, and neonatal and mature CTGF(+/-) and CTGF(+/+) mice were used in models of oxygen-induced retinopathy and laser-induced choroidal neovascularization. Angiogenesis in vitro was independent of the CTGF genotype in both the presence and the absence of VEGF. Oxygen-induced vascular pathology in the retina, as determined semi-quantitatively, and laser-induced choroidal neovascularization, as determined quantitatively, were also not affected by the CTGF genotype. Our data show that downregulation of CTGF levels does not affect neovascularization, indicating distinct roles of VEGF and CTGF in angiogenesis and fibrosis in eye conditions. 相似文献