全文获取类型
收费全文 | 417篇 |
免费 | 10篇 |
国内免费 | 3篇 |
出版年
2021年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 24篇 |
2010年 | 34篇 |
2009年 | 33篇 |
2008年 | 20篇 |
2007年 | 32篇 |
2006年 | 29篇 |
2005年 | 30篇 |
2004年 | 24篇 |
2003年 | 27篇 |
2002年 | 21篇 |
2001年 | 8篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 4篇 |
1958年 | 6篇 |
1955年 | 1篇 |
1954年 | 2篇 |
1951年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有430条查询结果,搜索用时 31 毫秒
101.
BRONWYN W. WILLIAMS DWAYNE R. ETTER DANIEL W. LINDEN KELLY F. MILLENBAH SCOTT R. WINTERSTEIN KIM T. SCRIBNER 《The Journal of wildlife management》2009,73(1):26-34
ABSTRACT Estimation of abundance is important for assessing population responses to management actions. Accurate abundance estimates are particularly critical for monitoring temporal variation following reintroductions when the management goal is to attain population sizes capable of sustaining harvest. Numerous reintroductions have taken place in the Great Lakes region of North America, including efforts to restore extirpated fishers (Martes pennanti) and American martens (M. americana). We used a DNA-based noninvasive hair-snaring method based on one trap design and trapping -grid configuration, and evaluated capture—mark—recapture (CMR) analytical approaches to simultaneously estimate population size for co-distributed fishers and American martens in a 671-km2 area of the Ottawa National Forest in the western Upper Peninsula of Michigan, USA. We included harvest as a final recapture period to increase probability of recapture and to evaluate potential violations of geographic closure assumptions. We used microsatellite markers to identify target species, eliminate congener species, and provide individual identity for estimation of abundance. Population estimates for fishers and martens on the study area ranged from 35 to 60 and 8 to 28, respectively. Estimators incorporating harvest data resulted in up to a 40% increase in abundance estimates relative to estimators without harvest. We considered population estimates not including harvest data the most appropriate for the study due to timing of sampling and environmental factors, but inclusion of harvested individuals was shown to be useful as a means to detect violations of the assumption of geographic closure. We suggest improvements on future CMR sampling designs for larger landscape scales of relevance to management through incorporation of habitat or historical harvest data. Noninvasive genetic methods that simultaneously estimate the numerical abundance of co-distributed species can greatly decrease assessment costs relative to traditional methods, and increase resulting demographic and ecological information. 相似文献
102.
Sangmin Kim Jae Hyuck Choi Hye In Lim Se-Kyung Lee Wan Wook Kim Sungjin Cho JEE SOO KIM Jung-Han Kim Jun-Ho Choe Seok Jin Nam Jeong Eon Lee Jung-Hyun Yang 《Cellular signalling》2009,21(6):892-898
The number of epidermal growth factor receptors (EGFRs) and their ligands are highly expressed in malignant tumor cells. The EGF signaling pathway is also activated in up to one-third of patients with breast cancer. In this study, we investigated the novel function of the JAK3 inhibitor, WHI-P131, on EGF-induced MMP-9 expression and the regulatory mechanism of EGF-induced MMP-9 expression in SKBR3 cells. We observed that EGF increased MMP-9 mRNA and protein expression in a dose-dependent manner. EGF also induced the phosphorylation of EGFR, ERK, and STAT-3, and these effects were inhibited by the EGFR inhibitor, AG1478. To investigate the involvement of the STAT-3 pathway on EGF-induced MMP-9 expression, we pretreated SKBR3 cells with JAK1, JAK2, and JAK3 inhibitors prior to EGF treatment. The results showed that the JAK3 inhibitor, WHI-P131, as well as JAK3 siRNA transfection, but not the JAK1 and JAK2 inhibitors, significantly decreased EGF-induced MMP-9 expression. In addition, EGF-induced STAT-3 phosphorylation was only inhibited by WHI-P131. We then transfected cells with adenoviral STAT-3 (Ad-STAT-3), followed by treatment with EGF. Interestingly, EGF-induced MMP-9 expression was decreased by Ad-STAT-3 overexpression in a dose-dependent manner, while it was significantly increased by STAT-3 siRNA transfection. Our results also showed that basal levels of MMP-9 expression were significantly increased by constitutive active-MEK (CA-MEK) overexpression. EGF-induced ERK phosphorylation was prevented by WHI-P131, but not by JAK1 and JAK2 inhibitors. On the other hand, EGF-induced MMP-9 expression was decreased by the MEK1/2 inhibitor, UO126. Therefore, for the first time, we suggest that the JAK3 inhibitor, WHI-P131, inhibits EGF-induced STAT-3 phosphorylation as well as ERK phosphorylation. The JAK3/ERK pathway may play an important role in EGF-induced MMP-9 expression in SKBR3 cells. 相似文献
103.
Yong Hun JO Mi Young NOH Se Won KANG Dong Hyun KIM Seung Han OH Yong Seok LEE In Seok BANG Sook Jae SEO Iksoo KIM Yeon Soo HAN 《Entomological Research》2009,39(2):123-128
14-3-3 proteins are known to play a pivotal role in cell survival, apoptosis and signal transduction. The 14-3-3ζ isoform has been cloned and characterized from many eukaryotic organisms, including the fruit fly and silkworm. However, no study on mosquito 14-3-3 has been reported to date. In an attempt to investigate the function of 14-3-3 in midgut epithelial cells undergoing apoptosis, a cDNA library was generated from the malaria vector, Anopheles sinensis , which was treated with apoptosis-inducing Actinomycin-D. We were able to identify and obtain A. sinensis 14-3-3ζ cDNA ( Ansi14-3-3ζ ) from expressed sequence tags (EST) analysis after conducting massive sequencing of the A. sinensis cDNA library. Ansi14-3-3ζ has very high homology to 14-3-3 homologs of various insects, such as Anopheles gambiae (100%), Aedes aegypti (100%), Drosophila melanogaster (96%), Bombyx mori (93%), Apis mellifera (93%) and Mus musculus (81%), indicating that mosquito 14-3-3ζ is a highly conserved gene in diverse organisms. Analysis of temporal expression patterns showed that Ansi14-3-3ζ mRNA is highly expressed in egg, early pupae and adult stages and is also expressed, although at low levels, in fourth instar larvae and late pupae. In response to two immune elicitors (lipopolysaccharide and laminarin), no striking induction of 14-3-3ζ mRNA was observed in A. sinensis . Further studies of the precise biological function, inducibility and subcellular distribution of 14-3-3ζ are required in Plasmodium invasion-induced apoptotic midgut cells in A. sinensis in the context of the Time Bomb model. 相似文献
104.
Waseem AKRAM Faisal HAFEEZ Unsar Naeem ULLAH Yeon Kook KIM Aftab HUSSAIN Jong-Jin LEE 《Entomological Research》2009,39(2):107-113
Adults and immatures of Aedes mosquito populations were collected at temperatures between 40 and 44°C (summer), while larvae were collected at 0°C (winter). Major mosquito activities were observed from February to mid-December at various collection sites that yielded high populations of Aedes spp. from May to September, and high populations of Culex spp. and Anopheles spp. from March to September. In June to July, mosquito activity was suspended because the relative humidity was high (70%); a result of the monsoon rains. In August, with temperature ranging from 38 to 42°C, the populations of Culex , Anopheles and Aedes began to increase (36.8, 32.1 and 26.3%, respectively). Population estimates (through standard prototype Centers for Disease Control (CDC) and Biogents (BG)-sentinel) and species composition of Aedes in forest habitats indicated a rapid increase in the populations of Ae. albopictus (52.3%), Ae. aegypti (19.1%) and Ae. vittatus (28.5%) following the rainy season in July. Areas positive for Ae. albopictus had identical population levels and distribution ranges of Ae. vittatus , however, there were no Ae. aegypti in Ae. albopictus areas from August to September. The population level, seasonal distribution, habitat and areas of adult activity marked by global positioning system (GPS) coordinates are being used for reference and for species composition data of Anopheles spp. (2), Culex spp. (10) and Aedes spp. (5) in addition to associated temperature, relative humidity and physico-chemical factors of larval habitat. Global meteorological changes have caused an expansion of the active period, leading to the mosquito's possibility of being a vector of disease increasing, resulting in the spread of dengue fever. 相似文献
105.
106.
ROBERT S. SANSOM KIM FREEDMAN SARAH E. GABBOTT RICHARD J. ALDRIDGE MARK A. PURNELL 《Palaeontology》2010,53(6):1393-1409
Abstract: The anatomy and affinities of Jamoytius kerwoodi White have long been controversial, because its complex taphonomy makes unequivocal interpretation impossible with the methodology used in previous studies. Topological analysis, model reconstruction and elemental analysis, followed by anatomical interpretation, allow features to be identified more rigorously and support the hypothesis that Jamoytius is a jawless vertebrate. The preserved features of Jamoytius include W‐shaped phosphatic scales, 10 or more pairs of branchial openings, optic capsules, a circular, subterminal mouth and a single terminal nasal opening. Interpretations of paired ‘appendages’ remain equivocal. Phylogenetic analysis places Jamoytius and Euphanerops together (Jamoytiiformes), as stem‐gnathostomes rather than lamprey related or sister taxon to Anaspida. 相似文献
107.
108.
YEONG DU YOO HAE JIN JEONG NAM SEON KANG JAE YOON SONG KWANG YOUNG KIM GITACK LEE JUHYOUNG KIM 《The Journal of eukaryotic microbiology》2010,57(2):145-158
ABSTRACT. To investigate the feeding by the newly described mixotrophic dinoflagellate Paragymnodinium shiwhaense (GenBank accession number=AM408889), we explored the feeding process and the kinds of prey species that P. shiwhaense is able to feed on using several different types of microscopes, including a transmission electron microscope and high‐resolution video‐microscopy. In addition, we measured the growth and ingestion rates of P. shiwhaense on its optimal algal prey Amphidinium carterae as a function of prey concentration. We also measured these parameters for edible prey at a single concentration at which the growth and ingestion rates of P. shiwhaense on A. carterae were saturated. Paragymnodinium shiwhaense feed on algal prey using a peduncle after anchoring the prey by a tow filament. Among the algal prey offered, P. shiwhaense ingested small algal species that had equivalent spherical diameters (ESDs) ≤11 μm (e.g. the prymnesiophyte Isochrysis galbana, the cryptophytes Teleaulax sp. and Rhodomonas salina, the raphidophyte Heterosigma akashiwo, and the dinoflagellates Heterocapsa rotundata and A. carterae). However, it did not feed on larger algal species that had ESDs ≥12 μm (e.g. the dinoflagellates Prorocentrum minimum, Heterocapsa triquetra, Scrippsiella trochoidea, Alexandrium tamarense, Prorocentrum micans, Gymnodinium catenatum, Akashiwo sanguinea, and Lingulodinium polyedrum) or the small diatom Skeletonema costatum. The specific growth rates for P. shiwhaense feeding upon A. carterae increased rapidly with increasing mean prey concentration before saturating at concentrations of ca. 350 ng C/ml (5,000 cells/ml). The maximum specific growth rate (i.e. mixotrophic growth) of P. shiwhaense on A. carterae was 1.097/d at 20 °C under a 14:10 h light–dark cycle of 20 μE/m2/s, while its growth rate (i.e. phototrophic growth) under the same light conditions without added prey was ?0.224/d. The maximum ingestion and clearance rates of P. shiwhaense on A. carterae were 0.38 ng C/grazer/d (5.4 cells/grazer/d) and 0.7 μl/grazer/h, respectively. The calculated grazing coefficients for P. shiwhaense on co‐occurring Amphidinium spp. was up to 0.07/h (i.e. 6.7% of the population of Amphidinium spp. was removed by P. shiwhaense populations in 1 h). The results of the present study suggest that P. shiwhaense can have a considerable grazing impact on algal populations. 相似文献
109.
水稻低温发芽势的遗传及数量性状基因座分析 总被引:6,自引:0,他引:6
利用籼粳交“密阳23/吉冷1号”的F2:3代200个家系作为作图群体,在14℃条件下鉴定萌发7d、11d、14d和17d时低温发芽势,并利用由SSR标记构建的分子连锁图谱为基础,对不同萌发阶段的低温发芽势进行了数量性状基因座(QTLs)检测,同时进行了低温发芽势与其他耐冷性状间的相关分析。结果表明,萌发7d时低温发芽势及其低温反应指数呈现向低发芽势和低的低温反应指数的偏态分布,而萌发11d、14d和17d时低温发芽势及其低温反应指数均呈现接近正态的单峰连续分布。萌发14d时低温发芽势与其他耐冷性的相关性较萌发7d、11d和17d时低温发芽势更为密切,与芽期耐冷性、幼苗期耐冷性、低温下幼苗生长能力和孕穗期耐冷性表现为显著或极显著的正相关。位于第2染色体RM29-RM262区间的qLVG2和第7染色体RM336-RM118区间的qLVG7-2、qCIVG7-2在萌发11d、14d和17d时均检测到;位于RM29-RM262区间的qCIVG2在萌发11d和14d时均检测到,并对表型变异的贡献率随着萌发进程而逐渐增加。与低温发芽势相关的qLVG2贡献率从6.9%增加到14.2%,qLVG7-2贡献率从9.9%增加到11.2%,而与发芽势的低温反应指数相关的qCIVG2贡献率从6.3%增加到9.0%,qCIVG7-2贡献率从8.3%增加12.9%。这些QTL的增效等位基因均来自强耐冷亲本吉冷1号,基因作用方式主要为部分显性。 相似文献
110.
KYUNG‐HO MA KWANG‐HO KIM ANUPAM DIXIT JAE‐WOONG YU JONG‐WOOK CHUNG JEONG‐HEUI LEE EUN‐GI CHO TAE SAN KIM YONG‐JIN PARK 《Molecular ecology resources》2006,6(3):689-691
A microsatellite‐enriched library of Job's tears (Coix lacryma‐jobi L. var. Ma‐yuen Stapf) was constructed using a modified biotin–streptavidin capture method. After screening, 17 polymorphic microsatellites were used for diversity analysis among 30 Job's tears accessions. The number of alleles ranged from one to five alleles per locus with an average of 2.8 alleles. Expected heterozygosity (HE) and polymorphism information content (PIC) ranged from 0 to 0.676 and from 0 to 0.666, respectively. The newly developed microsatellite markers are expected to be very valuable tools for evaluation of genetic diversity among large germplasm collection of Job's tears present in our Korean Gene Bank. 相似文献