全文获取类型
收费全文 | 355篇 |
免费 | 28篇 |
专业分类
383篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 29篇 |
2014年 | 23篇 |
2013年 | 24篇 |
2012年 | 32篇 |
2011年 | 27篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 8篇 |
1999年 | 1篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1947年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有383条查询结果,搜索用时 10 毫秒
21.
22.
23.
We assessed the distribution and prevalence of growth anomalies (GAs) in Acropora from French Frigate Shoals (Hawaii, USA), Johnston Atoll and Tutuila (American Samoa), developed a nomenclature for gross morphology, characterized GAs at the cellular level and obtained preliminary indices of their spatial patterns and progression within coral colonies. Acropora GAs were found in all 3 regions, but the distribution, variety and prevalence of Acropora GAs was highest in American Samoa. GAs were grouped into 7 gross morphologies (exophytic, bosselated, crateriform, nodular, vermiform, fimbriate or annular). On histology, GAs consisted of hyperplastic basal body wall (calicodermis, mesoglea and gastrodermis apposed to skeleton) with 3 distinct patterns of necrosis. There was no evidence of anaplasia or mitotic figures (common but not necessarily required morphologic indicators of neoplasia). Compared to normal tissues, GAs had significantly fewer polyps, zooxanthellae within the gastrodermis of the coenenchyme, mesenterial filaments and gonads but significantly more necrosis. On 2 colonies with GAs monitored at 2 points over 11 mo, numbers of GAs per colony increased from 0.9 to 3 times the original number seen, and significant clustering of GAs occurred within colonies. The evidence of GAs being true neoplasias (tumors) is mixed, so a cautionary approach is urged in use of morphologic terminology. 相似文献
24.
Variation in parent–offspring kinship in socially monogamous systems with extra‐pair reproduction and inbreeding 下载免费PDF全文
Jane M. Reid Greta Bocedi Pirmin Nietlisbach A. Bradley Duthie Matthew E. Wolak Elizabeth A. Gow Peter Arcese 《Evolution; international journal of organic evolution》2016,70(7):1512-1529
Female extra‐pair reproduction in socially monogamous systems is predicted to cause cuckolded socially‐paired males to conditionally reduce paternal care, causing selection against extra‐pair reproduction and underlying polyandry. However, existing models and empirical studies have not explicitly considered that cuckolded males might be related to their socially‐paired female and/or to her extra‐pair mate, and therefore be related to extra‐pair offspring that they did not sire but could rear. Selection against paternal care, and hence against extra‐pair reproduction, might then be weakened. We derive metrics that quantify allele‐sharing between within‐pair and extra‐pair offspring and their mother and her socially‐paired male in terms of coefficients of kinship and inbreeding. We use song sparrow (Melospiza melodia) paternity and pedigree data to quantify these metrics, and thereby quantify the joint effects of extra‐pair reproduction and inbreeding on a brood's total allelic value to its socially‐paired parents. Cuckolded male song sparrows were almost always detectably related to extra‐pair offspring they reared. Consequently, although brood allelic value decreased substantially following female extra‐pair reproduction, this decrease was reduced by within‐pair and extra‐pair reproduction among relatives. Such complex variation in kinship within nuclear families should be incorporated into models considering coevolutionary dynamics of extra‐pair reproduction, parental care, and inbreeding. 相似文献
25.
Anne McHugh Paulette Bierzychudek Christina Greever Tessa Marzulla Richard Van Buskirk Greta Binford 《Journal of Insect Conservation》2013,17(6):1237-1253
The genetic structure of lineages can provide important information for delineating “evolutionarily significant units” (ESUs) for conservation, and for planning actions to protect and restore taxa threatened with extinction. Speyeria zerene hippolyta, the Oregon silverspot butterfly, is a U.S.A. federally threatened subspecies that is the focus of considerable conservation effort, but whose evolutionary relationships with other Speyeria taxa are not well-understood. We conducted a genetic analysis of nine Speyeria species and 25 subspecies from western U.S.A., using both mitochondrial and nuclear markers. Our goal was to determine whether such data supported (a) S. z. hippolyta’s designation as an ESU, and (b) the current morphologically-based taxonomy of Speyeria spp. Our data for S. z. hippolyta were equivocal; while nuclear markers resolved all these individuals into a single clade, mtDNA data suggested the existence of two clades. Aside from S. cybele, which was consistently supported as monophyletic, our data provided little support for most of the species currently recognized for western U.S. Speyeria, including S. zerene, and even less for the many subspecies designations. These genetic findings stand in contrast to the morphological differences recognized by experts, and suggest a relatively recent origin for many of these taxa. Two of 66 individuals screened for Wolbachia infection tested positive for this symbiont. Our results provide no persuasive evidence that S. z. hippolyta should lose its status as an ESU, but they have important implications for ongoing management actions such as population augmentation. 相似文献
26.
Water collected on the spring equatorial Pacific Joint GlobalOcean Flux Study (JGOFS) was placed in ultra-clean bottles inan incubator on deck under the direction of the team of J.H.Martin.Half of the bottles were enriched with 2.53 mM iron; the otherhalf served as controls. Cell counts increased, while the numberof species was reduced, in both the controls and the treatedsamples over the period of the experiment. Diatoms dominated,and after an early growth spurt in the Fe-enriched bottles,most diatom species showed greater growth in the controls atthe end of the 6 day experiment. However, as the experimentwas terminated, more cells overall were noted in the Fe-enrichedsamples, with the most abundant diatom, Cylindrotheca closterium.principally responsible for the difference. Growth rates werehigh in both the controls and the treated samples, with overallrates of 1.33.0 divisions day1 in the Fe-treatedsamples and 1.93.4 divisions day1 in the controls.The group of smaller pennate diatoms averaged 2.9 divisionsday1 in the Fe-treated samples and 3.3 divisions day1in the controls over the entire experiment. 相似文献
27.
T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies 总被引:2,自引:0,他引:2
Garrido G Lorenzano P Sánchez B Beausoleil I Alonso DF Pérez R Fernández LE 《Cancer immunology, immunotherapy : CII》2007,56(11):1701-1710
Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis
had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment
of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs
have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated
the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb
significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects
on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect.
In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly,
7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic
sites. More strikingly, depletion of CD8+ and CD4+ T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant.
This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction
of an adjuvant effect.
This work was supported by the Cuban Government. 相似文献
28.
Stefanie Rettcher Felicitas Jungk Christoph Kühn Hans-Joachim Krause Greta N?lke Ulrich Commandeur Rainer Fischer Stefan Schillberg Florian Schr?per 《Applied and environmental microbiology》2015,81(9):3039-3048
Plant pathogens cause major economic losses in the agricultural industry because late detection delays the implementation of measures that can prevent their dissemination. Sensitive and robust procedures for the rapid detection of plant pathogens are therefore required to reduce yield losses and the use of expensive, environmentally damaging chemicals. Here we describe a simple and portable system for the rapid detection of viral pathogens in infected plants based on immunofiltration, subsequent magnetic detection, and the quantification of magnetically labeled virus particles. Grapevine fanleaf virus (GFLV) was chosen as a model pathogen. Monoclonal antibodies recognizing the GFLV capsid protein were immobilized onto immunofiltration columns, and the same antibodies were linked to magnetic nanoparticles. GFLV was quantified by immunofiltration with magnetic labeling in a double-antibody sandwich configuration. A magnetic frequency mixing technique, in which a two-frequency magnetic excitation field was used to induce a sum frequency signal in the resonant detection coil, corresponding to the virus concentration within the immunofiltration column, was used for high-sensitivity quantification. We were able to measure GFLV concentrations in the range of 6 ng/ml to 20 μg/ml in less than 30 min. The magnetic immunoassay could also be adapted to detect other plant viruses, including Potato virus X and Tobacco mosaic virus, with detection limits of 2 to 60 ng/ml. 相似文献
29.
Montipora white syndrome (MWS) results in tissue-loss that is often lethal to Montipora capitata, a major reef building coral that is abundant and dominant in the Hawai'ian Archipelago. Within some MWS-affected colonies in Kane'ohe Bay, Oahu, Hawai'i, we saw unusual motile multicellular structures within gastrovascular canals (hereafter referred to as invasive gastrovascular multicellular structure-IGMS) that were associated with thinning and fragmentation of the basal body wall. IGMS were in significantly greater densities in coral fragments manifesting tissue-loss compared to paired normal fragments. Mesenterial filaments from these colonies yielded typical M. capitata mitochondrial haplotypes (CO1, CR), while IGMS from the same colony consistently yielded distinct haplotypes previously only found in a different Montipora species (Montipora flabellata). Protein profiles showed consistent differences between paired mesenterial filaments and IGMS from the same colonies as did seven microsatellite loci that also exhibited an excess of alleles per locus inconsistent with a single diploid organism. We hypothesize that IGMS are a parasitic cellular lineage resulting from the chimeric fusion between M. capitata and M. flabellata larvae followed by morphological reabsorption of M. flabellata and subsequent formation of cell-lineage parasites. We term this disease Montiporaiasis. Although intra-specific chimerism is common in colonial animals, this is the first suspected inter-specific example and the first associated with tissue loss. 相似文献
30.