全文获取类型
收费全文 | 197篇 |
免费 | 15篇 |
专业分类
林业 | 9篇 |
农学 | 5篇 |
64篇 | |
综合类 | 7篇 |
农作物 | 22篇 |
水产渔业 | 19篇 |
畜牧兽医 | 51篇 |
园艺 | 6篇 |
植物保护 | 29篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有212条查询结果,搜索用时 46 毫秒
51.
52.
53.
54.
Ewa Smolska 《CATENA》2007
The density of gully network in the Suwa?ki Lakeland (northeastern Poland) with typical last-glaciation relief is 0.2 km/km2 on average and locally reaches 1.2 km/km2. Most gullies are isolated but sporadically they create dendritic patterns. The larger gullies are developed along dellies (bowl-shaped, dry valleys) or melt-out valleys. The smaller and shorter gullies occur on the slopes of melt-out depressions and tunnel valleys. Ages of peat covered by fans at the mouths of larger gullies indicate that gully erosion started between 3520 ± 70 to 2240 ± 100 BP. Two different units build the fans and infilled the gullies. The older unit in the lower part of fans is up to 5 m thick, contains sand and gravel that generally originated from the bottom and bank erosion of the gullies and resembles alluvium. The younger unit, about 2–3 m thick, consists of colluvium. The fans at the mouths of smaller and shorter gullies are mainly built of colluvium. The maximal grain diameter in both units is similar, which testifies to a similar intensity of extreme rainfalls. The analysed sediments have different characteristics, which indicate that the source material and depositional changes are linked to forest clearance and farmland expansion starting in the 7th century AD and continuing in the Middle Ages. 相似文献
55.
Ewa Wieczorek-Olchawa Maria Niklinska Jacek Miedzobrodzki Barbara Plytycz 《Pedobiologia》2003,47(5-6):702-709
56.
Karl Hammer Ewa Skolimowska Helmut Knüpffer 《Genetic Resources and Crop Evolution》1987,35(2):135-177
Zusammenfassung Die Genbank in Gatersleben verfügt über eine umfangreiche Wildroggen-Kollektion, die für die Aufgaben der Züchtungsforschung und Züchtung zur Verfügung steht. Probleme der Erhaltung dieser Kollektion in der Genbank werden diskutiert. In diesem Zusammenhang wird das Reproduktionssystem besonders untersucht.Zur Dokumentation des Materials ist seine Identifikation notwendig. Daher wurde die GattungSecale revidiert. Neukombinationen werden fürS. strictum (Presl) Presl — subsp.kuprijanovii (Grossh.) Hammer, subsp.anatolicum (Boiss.) Hammer, subsp.ciliatoglume (Boiss.) Hammer, subsp.africanum (Stapf) Hammer — und fürS. cereale L. — subsp.afghanicum (Vav.) Hammer — vorgeschlagen. Zur Determination der Sippen wird ein Bestimmungsschlüssel publiziert.Entwicklungstendenzen innerhalb der Gattung werden aufgezeigt.
Herrn Prof. Dr. Dr. h. c. mult.H. Stubbe aus Anlaß der 85. Wiederkehr seines Geburtstages gewidmet.
Der Beitrag von E. S. entstand im Ergebnis eines Studienaufenthaltes zur Vorbereitung ihrer Dissertation 1986 in Gatersleben. 相似文献
Preliminary work on monographs of wild plant collections:Secale L
Summary The Gatersleben gene bank holds a large collection of wild rye available for the tasks of breeding research and plant breeding. Problems of maintaining this collection in the gene bank are discussed. In this connection the breeding system is especially studied.A proper identification of the material is a necessary prerequisite for its documentation. Therefore, the genusSecale was revised. New combinations are proposed forS. strictum (Presl) Presl — subsp.kuprijanovii (Grossh.) Hammer, subsp.anatolicum (Boiss.) Hammer, subsp.ciliatoglume (Boiss.) Hammer, subsp.africanum (Stapf) Hammer — and forS. cereale L. — subsp.afghanicum (Vav.) Hammer. Keys for the determination of species and subspecies are given.Evolutionary trends within the genus are demonstrated.
: Secale L
, . . . . Secale. . S. strictum (Presl) Presl — subsp.kuprijanovii (Grossh.) Hammer, subsp.anatolicum (Boiss.) Hammer, subsp.ciliatoglume (Boiss.) Hammer, subsp.africanum (Stapf) Hammer — S. cereale L. — subsp.afghanicum (Vav.) Hammer. . .
Herrn Prof. Dr. Dr. h. c. mult.H. Stubbe aus Anlaß der 85. Wiederkehr seines Geburtstages gewidmet.
Der Beitrag von E. S. entstand im Ergebnis eines Studienaufenthaltes zur Vorbereitung ihrer Dissertation 1986 in Gatersleben. 相似文献
57.
Staffan Åkerblom Erland Bååth Lage Bringmark Ewa Bringmark 《Biology and Fertility of Soils》2007,44(1):79-91
This study compared the toxic effects of adding chromium (Cr), zinc (Zn), lead (Pb), molybdenum (Mo), nickel (Ni), and cadmium
(Cd) at three dose levels to mor layer samples in laboratory experiments. Microbial activity in the form of soil respiration
was monitored for 64 days. At the end of the experimental period, the composition of the soil microbial community structure
was analysed by phospholipid fatty acid (PLFA) analysis. The metals added induced changes in the microbial community structure
and affected respiration negatively, indicating toxicity. The microbial community structure (principal component analysis
of the PLFA pattern) for all metals was significantly related to microbial activity (cumulative respiration), indicating intimate
links between microbial community structure and activity. The most striking result in this study was that the shift in the
microbial community because of metal stress was similar for all metals. Thus, the PLFA i16:0 increased most in relative abundance
in metal-polluted soils, followed by other PLFAs indicative of Gram-positive bacteria (10Me16:0, 10Me17:0, 10Me18:0, a17:0
and br18:0). The PLFA 16:1ω5 was consistently negatively affected by metal stress, as were the PLFAs 18:1, 18:1ω7 and 19:1a.
However, a significant separation between Cr- and Cd-polluted soils was observed in the response of the PLFA cy19:0, which
decreased in abundance with Cr stress, and increased with Cd stress. Furthermore, the PLFA 18:2w6, indicating fungi, only
increased with Cr and Zn stress. The effective doses of the metals, ranked with regard to background metal concentrations,
decreased in the order: Zn > Cr > Pb > Mo > Ni > Cd. We concluded that interpretation of results of microbial activity from
experiments of metal toxicity should include microbial structural patterns and background metal concentrations. 相似文献
58.
Joanna Szlendak Christine Adler Jakob Scherzer Anna Niwinska Ewa Kautz Ricardo Faundez 《Reproduction in domestic animals》2020,55(6):691-700
The aim of the present study was to evaluate the effect of sperm selection by single-layer centrifugation (SLC) performed before freezing on sperm quality after thawing of Fleckvieh bull semen. Ejaculates from 22 bulls were collected by artificial vagina and divided into two aliquots. One aliquot (control sample) was diluted with Steridyl® and frozen over nitrogen vapour in a Digitcool freezer (IMV Technologies). Sperm from the second aliquot (SLC sample) was selected using the SLC technique with Bovicoll colloid and then frozen over nitrogen vapour in a Digitcool freezer. After thawing, both samples (control and SLC) were evaluated by computer-aided sperm analysis (CASA; SCA 6.4 System; Microptic S.L) for sperm motility parameters. Integrity of the plasma membrane (viability), high mitochondrial membrane potential (HMMP) and acrosome integrity were assessed using a Guava® easyCyte flow cytometer (IMV Technologies). Morphological examination of spermatozoa was performed by Differential Interference Contrast microscopy (Leica DMi8). Morphological examination of live, immobilized spermatozoa was analysed under high magnification (≥6,600×). After thawing, the mean sperm viability of the control sample was 51.57%, compared to 40.37% for the SLC sample (p < .01). HMMP was higher (p < .01) in the control sample (40.37% versus 28.96%), and the mean of live spermatozoa with damaged acrosome was significantly higher (p < .03) in the SLC sample (1.63% versus 1.95%). The mean percentage of motile spermatozoa was 80.17% in the control sample, compared to 75.14% in the SLC sample (p < .0195), and rapid subpopulation reduced from 20.08% to 8.99% (p < .0001) after SLC. Percentage of hyperactivated sperm decreased from 12.23% to 4.28% (p < .0001) after SLC. Given the overall results, the sperm quality of thawed Fleckvieh bull semen was not improved when sperm were selected by SLC before freezing. 相似文献
59.
Agnieszka Nowak Joanna Kochan Ewa Świętek Barbara Kij Sylwia Prochowska Wojciech Witarski Monika Bugno-Poniewierska Wojciech Niżański 《Reproduction in domestic animals》2020,55(8):992-997
The aim of this study was to evaluate the applicability of the Cryotech technique for the vitrification of domestic cat (Felis catus) oocytes, as a model for other feline species threatened with extinction. This technique, in which oocytes are stored in a minimal volume of medium, is already widely used in human assisted reproductive technology. In the first part of this study, a viability test (EtBr/FDA) was used to evaluate the toxicity of the vitrification media (solutions). After IVM, oocytes were placed in vitrification and warming solutions according to the manufacturer's procedure, with or without exposure to liquid nitrogen. The solutions and the vitrification procedure each caused a reduction in oocyte viability, with survival rates of 71.4% in oocytes exposed to the Cryotech media (without cooling in liquid nitrogen), and 62% in oocytes that were vitrified. In the second part of the experiment, parthenogenetic activation was used to evaluate the developmental potential of oocytes previously vitrified using the Cryotech method. After warming, the oocytes were activated using a combination of 0.7 µM ionomycin in TCM 199 medium (5 min) followed by 2 mM 6-DMAP in TCM 199 supplemented with 10% FBS (3 hr), then cultured and evaluated every 24 hr for parthenogenetic cleavage. In the experimental group, 23/50 (46%) cleaved embryos were obtained. Domestic cat oocytes, vitrified by the Cryotech method, are characterized by high survival rates. However, it is necessary to improve the technique to increase the developmental competence of embryos obtained from vitrified oocytes. 相似文献
60.
Ewa Łukaszewicz Anna Jerysz Bronisława Chełmońska 《Reproduction in domestic animals》2020,55(8):943-950
Avian semen dilution with appropriate extender allows to prolong the fertilizing ability of sperm stored in vitro. In the present study, the impact of extenders and time of storage on morphology of Muscovy duck (Cairina moschata) drake semen were examined. Semen was collected twice a week, using male stimulation by a female method, from 12 adults (29 weeks old) drakes kept individually in cages, under controlled environmental conditions. Freshly collected, pooled ejaculates were divided into three part: neat undiluted sample, and diluted 1:1 with Schramm (SCH) or Watanabe (W) extender and stored at 4°C. Morphological examination of all samples was conducted after dilution and then, after 3 and 6 hr of storage. The storage of undiluted semen caused decrease (p ≤ .01) in live morphologically normal sperm, from 79.73% in the freshly collected ejaculates to 55.75% and to 12.12% after 3 and 6 hr of storage, respectively (average calculated for the entire reproductive season). In the semen diluted with Schramm's extender the adequate values attained 86.84, 79.65 and 61.66%, and using Watanabe extender 84.77, 83.58 and 75.25%, respectively. The period of semen storage and the type of extender caused significant (p ≤ 0,05; p ≤ 0,01) changes in sperm morphology. The longer period of storage contributed to the decrease in number of morphologically normal sperm, whereas their content in Watanabe extender after 3 and 6 hr of storage was higher (p ≤ .01) than in semen diluted in Schramm extender. 相似文献