全文获取类型
收费全文 | 130篇 |
免费 | 12篇 |
专业分类
林业 | 16篇 |
农学 | 1篇 |
1篇 | |
综合类 | 10篇 |
农作物 | 2篇 |
水产渔业 | 1篇 |
畜牧兽医 | 107篇 |
植物保护 | 4篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 32篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
排序方式: 共有142条查询结果,搜索用时 15 毫秒
71.
SAA Butler NJ Phillips GB Boe‐Hansen GA Bo BM Burns K Dawson MR McGowan 《Reproduction in domestic animals》2012,47(3):463-471
The primary objective of this study was to investigate the impact of animal‐level factors including energy balance and environmental/management stress, on the ovarian function of Bos indicus heifers treated to synchronize ovulation. Two‐year‐old Brahman (BN) (n = 30) and BN‐cross (n = 34) heifers were randomly allocated to three intravaginal progesterone‐releasing device (IPRD) treatment groups: (i) standard‐dose IPRD [Cue‐Mate® (CM) 1.56 g; n = 17]; (ii) half‐dose IPRD [0.78 g progesterone (P4); CM 0.78 g; n = 15]; (iii) half‐dose IPRD + 300 IU equine chorionic gonadotrophin at IPRD removal (CM 0.78 g + G; n = 14); (iv) and a control group, 2× PGF2α [500 μg prostaglandin F2α (PGF2α)] on Day ?16 and ?2 (n = 18). Intravaginal progesterone‐releasing device‐treated heifers received 250 μg PGF2α at IPRD insertion (Day ?10) and IPRD removal (Day ?2) and 1 mg oestradiol benzoate on Day ?10 and ?1. Heifers were managed in a small feedlot and fed a defined ration. Ovarian function was evaluated by ultrasonography and plasma P4 throughout the synchronized and return cycles. Energy balance was evaluated using plasma insulin‐like growth factor 1 (IGF‐I) and glucose concentrations. The impact of environmental stressors was evaluated using plasma cortisol concentration. Heifers that had normal ovarian function had significantly higher IGF‐I concentrations at commencement of the experiment (p = 0.008) and significantly higher plasma glucose concentrations at Day ?2 (p = 0.040) and Day 4 (p = 0.043), than heifers with abnormal ovarian function. There was no difference between the mean pre‐ovulatory cortisol concentrations of heifers that ovulated or did not ovulate. However, heifers that ovulated had higher cortisol concentrations at Day 4 (p = 0.056) and 6 (p = 0.026) after ovulation than heifers that did not ovulate. 相似文献
72.
Focussing on four types of parenchyma cell around pith regions of branches of Robinia pseudoacacia L. var. inermis, we examined the timing and role of cell death during heartwood formation. Large parenchyma cells that were located in the
inner part of the pith died within a year. By contrast, other parenchyma cells died within 4 years, with the timing of cell
death depending on the type of cell. Axial parenchyma cells of the xylem close to the pith died first. Then, small parenchyma
cells died in the perimedullary zone in the outer part of the pith. Finally, ray parenchyma cells in the xylem close to the
pith died. Variations in the autofluorescence of cell walls, which might have been due to deposition of heartwood substances,
were observed first in xylem ray parenchyma cells and small parenchyma cells in the perimedullary zone. Our results indicate
that the initiation of heartwood formation occurs within 4 years in pith regions of branches in Robinia pseudoacacia L. var. inermis. Moreover, it appears that not only xylem ray parenchyma cells but also small parenchyma cells in the perimedullary zone
might be involved in the synthesis of heartwood substances. 相似文献
73.
Yusuke Yamagishi Takenao Sato Hiromu Uchiyama Joto Yoshimoto Remi Nakagawa Satoshi Nakaba Takafumi Kubo Ryo Funada 《Journal of Wood Science》2012,58(6):557-562
Differentiated cells were recognized in calli derived from needles of Torreya nucifera and in calli derived from immature zygotic embryos of Cryptomeria japonica. Some differentiated cells resembled tracheary elements of primary xylem with spiral or reticulate thickening of cell walls. Other cells resembled tracheary elements with thick cell walls and bordered pits, which are features of secondary xylem. These tracheary elements were formed in cell clusters. Tracheary elements in calli of T. nucifera formed more highly developed structures, such as bordered pits and spiral thickening, than those of C. japonica. Cultured cells derived from conifers might provide a good model for studies of the differentiation of secondary xylem in vitro. 相似文献
74.
Widyanto Dwi Nugroho Sri Nugroho Marsoem Koh Yasue Takeshi Fujiwara Toshiko Nakajima Masanori Hayakawa Satoshi Nakaba Yusuke Yamagishi Hyun-O Jin Takafumi Kubo Ryo Funada 《Journal of Wood Science》2012,58(3):185-194
The anatomical characteristics and density of wood were examined in 23-year-old Acacia mangium trees that had been planted in Yogyakarta, Indonesia. The seeds had been collected from trees of five different provenances. The distance from the pith of the boundary between juvenile and mature wood was also examined to clarify the maturity of the wood. Lengths of wood fibers near the pith and the distance from the pith of the boundary between juvenile and mature wood differed significantly among provenances. By contrast, other anatomical characteristics of the wood such as fiber wall area, fiber wall thickness, fiber diameter, vessel lumen area, vessel diameter, vessel frequency and wood density did not differ significantly among provenances. Wood density was strongly correlated with the area of fiber walls. Our observations suggest that Sidei and Daintree might be more appropriate provenances among those examined for the Acacia mangium tree-breeding programs in Indonesia that are aimed at improving wood quality, because these provenances are associated with longer initial wood fibers and narrower juvenile areas than the other provenances studied. 相似文献
75.
76.
77.
MC Esteso MR Fernández-Santos AJ Soler V Montoro A Quintero-Moreno JJ Garde 《Reproduction in domestic animals》2006,41(3):241-246
Computer-automated sperm-head morphometry was used in this study to determine the effects of cryopreservation on red deer sperm-head morphometry. Epididymal sperm samples were collected from 40 mature stags and were divided. One portion was diluted at room temperature in a Tris-citrate egg yolk medium, containing 6% glycerol. A microscope slide was prepared from single extended sperm samples prior to freezing. The remainder of each sample was frozen in nitrogen vapours. After thawing, sperm smears were prepared as described above. All slides were air dried and stained with Hemacolor. The sperm-head dimensions for length, width, area, perimeter and shape factor (length/width), for a minimum of 135 spermatozoa were determined for each slide by means of the Sperm-Class Analyser (SCA). Firstly, our results show that cryopreservation substantially reduced (p < 0.001) sperm motility and plasma membrane and acrosome integrities. In addition, sperm heads were significantly smaller in cryopreserved spermatozoa than in the companion extended samples for area (32.05 microm2 vs 32.56 microm2; p < 0.05), length (8.46 microm vs 8.53 microm; p < 0.0001) and shape factor (1.833 vs 1.849; p < 0.0001) for all stags. These differences were found within 29 of 40 stags (75%) for at least three of the morphometric parameters. The individual variability (CV) of sperm head measurements from extended samples was negatively correlated (p < 0.005) with the per cent of change in sperm head measurements after cryopreservation for area (r = -0.465), width (r = -0.483) and perimeter (r = -0.375). Thus, the lower the sperm head variability in the extended samples, the greater the sperm change as a consequence of the cryopreservation. These results suggest that the variability (heterogeneity) in sperm head dimensions of individual stags may be a good indicator of sperm freezability. 相似文献
78.
The total amounts of endogenous indole-3-acetic acid (IAA), cytokinins, and abscisic acid (ABA) were quantified by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) in cambial regions of the main stems ofLarix kaempferi during the spring season. During the sampling period, cambium in the dormant state entered the active meristematic state. The total amount of IAA did not change at the onset of cambial reactivation but increased when the active division of cambial cells became apparent. Four cytokinins —trans- andcis-ribosylzeatin (RZ),N
6-isopentenyladenine (iP),N
6-isopentenyladenosine (iPA) — were quantified, but no zeatin (Z) was detected. The total amount of the four cytokinins together and the total amount of isopentenyl-type cytokinins (iP and iPA) varied during the sampling period but did not appear to be specifically associated with cambial activity. The total amounts oftrans- andcis-RZ remained relatively constant during the sampling period, as did the total amount of ABA. The results suggest that there is little correlation between total amounts of endogenous plant hormones in the cambial region and reactivation of the cambium during the spring. 相似文献
79.
RE Dunin-Borkowski MR McCartney RB Frankel DA Bazylinski M Posfai PR Buseck 《Science (New York, N.Y.)》1998,282(5395):1868-1870
Off-axis electron holography in the transmission electron microscope was used to correlate the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. The magnetite crystals were all single magnetic domains, and the magnetization directions of small superparamagnetic crystals were constrained by magnetic interactions with larger crystals in the chains. Shape anisotropy was found to dominate magnetocrystalline anisotropy in elongated crystals. A coercive field between 300 and 450 oersted was determined for one chain. 相似文献
80.
Morphological changes in the cytoskeleton, nuclei, and vacuoles were monitored during the cell death of short-lived ray tracheids
in the conifer Pinus densiflora. After formation of the dentate thickenings that occurred at the final stage of formation of cell walls, organelles started
to disappear in differentiating ray tracheids. First, the microtubules and vacuoles disappeared. Then actin filaments disappeared
in the differentiating ray tracheids adjacent to ray tracheids that lacked nuclei, and, finally, the nuclei disappeared. These
features indicate that cell death in ray tracheids might differ from the programmed cell death of tracheary elements that
has been studied in vitro in the Zinnia culture system.
This study was presented at the 57th Annual Meeting of the Japan Wood Research Society, August 8–10, 2007, Hiroshima, Japan 相似文献