全文获取类型
收费全文 | 145篇 |
免费 | 5篇 |
专业分类
林业 | 13篇 |
农学 | 2篇 |
基础科学 | 1篇 |
35篇 | |
综合类 | 15篇 |
农作物 | 8篇 |
水产渔业 | 17篇 |
畜牧兽医 | 40篇 |
园艺 | 4篇 |
植物保护 | 15篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 5篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 18篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1940年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有150条查询结果,搜索用时 15 毫秒
71.
Philippe Revol Brent E. Clothier Pascal Kosuth Georges Vachaud 《Irrigation Science》1996,16(4):169-173
The size of the free-water ponds under drippers is an important field characteristic of trickle irrigation. Here we review
four existing analytical theories that purport to describe 3-D infiltration. We show how they can be used to predict the extent
of the pond from basic soil parameters, and the dripper discharge rate. Via a numerical example it is shown that the different
theories give significantly different free-water pond radii, especially for high drip discharge rates when the flow is dominated
by gravity. We then describe field experiments that were carried out to permit a comparison of the measured and predicted
values using independently-measured soil parameters. This test of the different theories was conducted on a loamy soil. Raats'
(1971) solution gave the best estimates of the free-water pond radius, across the range of discharge rates. The free-water
pond radius, a determinant of the lateral spread away from the dripper, was found to vary only weakly with drip discharge
in the range of practical applications. Consequences for management are discussed.
Received: 24 September 1995 相似文献
72.
Development and comparison of four real-time polymerase chain reaction systems for specific detection and quantification of Zea mays L 总被引:5,自引:0,他引:5
Hernández M Duplan MN Berthier G Vaïtilingom M Hauser W Freyer R Pla M Bertheau Y 《Journal of agricultural and food chemistry》2004,52(15):4632-4637
Four real-time polymerase chain reaction systems aiming at the specific detection and quantification of maize DNA are described. They have been developed in four independent laboratories targeting different maize sequences, i.e., alcohol dehydrogenase (Adh1), high mobility group protein (hmga), invertase A (ivr1), and zein, respectively. They were all fully specific, showing a very similar quantification accuracy along a number of distantly related maize cultivars and being either single or low copy number genes. They were highly sensitive and exhibited limits of quantification below 100 maize genomic copies. In consequence, they are considered suitable for use as maize specific endogenous reference genes in DNA analyses, including GMO quantitative tests. 相似文献
73.
74.
Sex in reptiles is determined by genes on sex chromosomes or by incubation temperature. Previously these two modes were thought to be distinct, yet we show that high incubation temperatures reverse genotypic males (ZZ) to phenotypic females in a lizard with ZZ and ZW sex chromosomes. Thus, the W chromosome is not necessary for female differentiation. Sex determination is probably via a dosage-sensitive male-determining gene on the Z chromosome that is inactivated by extreme temperatures. Our data invite a novel hypothesis for the evolution of temperature-dependent sex determination (TSD) and suggest that sex chromosomes may exist in many TSD reptiles. 相似文献
75.
76.
Sarasa M Serrano E Soriguer RC Granados JE Fandos P Gonzalez G Joachim J Pérez JM 《Veterinary parasitology》2011,175(3-4):306-312
Testes mass is a key factor in male reproductive success and is potentially exposed to so-called 'parasitic castration'. This is the result of the direct destruction or alteration of reproductive cell lineages (parasitic castration sensu stricto), or the indirect detrimental effects - for example, via body condition - on the ability of progenitors to produce or rear offspring (parasitic castration sensu lato). There are enormous gaps in our knowledge on the effects of parasites on the testes of wild mammals and in an attempt to rectify this dearth of data we examined the relationship between the skin parasite Sarcoptes scabiei and testes mass in Iberian ibex Capra pyrenaica. We considered data from 222 males that were culled in the population from the Sierra Nevada in Spain. Our results provide evidence that sarcoptic mange is associated with reduced size-corrected testes mass in Iberian ibex which supports the hypothesis that parasitism is a determining factor in gonad plasticity in male mammals. We discuss several hypothetical causes of this relationship and highlight the need to deepen the sub-lethal effects of pathogens if we are to accurately understand their modulator effects on host population dynamics. 相似文献
77.
Espagne E Dupuy C Huguet E Cattolico L Provost B Martins N Poirié M Periquet G Drezen JM 《Science (New York, N.Y.)》2004,306(5694):286-289
Little is known of the fate of viruses involved in long-term obligatory associations with eukaryotes. For example, many species of parasitoid wasps have symbiotic viruses to manipulate host defenses and to allow development of parasitoid larvae. The complete nucleotide sequence of the DNA enclosed in the virus particles injected by a parasitoid wasp revealed a complex organization, resembling a eukaryote genomic region more than a viral genome. Although endocellular symbiont genomes have undergone a dramatic loss of genes, the evolution of symbiotic viruses appears to be characterized by extensive duplication of virulence genes coding for truncated versions of cellular proteins. 相似文献
78.
Guadalupe Gómez-Hernández Juana Claudia Leyva-Aguilera Sheila Delhumeau-Rivera Georges Seingier Fernando Ricardo Elorriaga-Verplancken Gisela Heckel 《水产资源保护:海洋与淡水生态系统》2021,31(4):841-852
- Marine mammals are indicators of ecosystem health, and thus stranding records are an invaluable information source. The response to marine mammal stranding (RMMS) must be comprehensive, taking into account three components: (i) operations, (ii) research, and (iii) information dissemination. Although RMMS had previously been practised in several coastal locations in Mexico, the recent enforcement of a new regulation for RMMS has posed a challenge to actors as they adapt to it.
- To understand the functioning of RMMS in Mexico, Bahía Todos Santos and Bahía de La Paz, two localities with over 20 years of experience in RMMS, were selected. To achieve this goal, a document review to identify the actors involved and their functions was undertaken together with a social network analysis to identify relevant actors in each locality and semi-structured interviews to identify key topics for RMMS.
- The composition of the involved actors was similar at both locations. Some actors were found to have mandatory functions (i.e. governmental actors), while others (i.e. civil society organizations) performed functions beyond those established in official documents. Governmental agencies, the academic sector, and civil society organizations were the most connected actors and could help disseminate information, facilitate communication within the network, and influence decision-making.
- The main topics identified were, in order of relevance: (i) economic constraints; (ii) actors' involvement; (iii) stranding response logistics; and (iv) recognition among actors.
- In conclusion, several limitations to the RMMS exist at both localities, mainly related to the lack of economic resources, but actors involved in RMMS actions are motivated by their own interests. This study proposes the integration of actors into local networks that take into consideration the biological, physical, and social characteristics of each place.
79.
Sabrine Attia Kaouthar Lebdi Grissa Georges Lognay Ellyn Bitume Thierry Hance Anne Catherine Mailleux 《Journal of pest science》2013,86(3):361-386
The two-spotted spider mite, Tetranychus urticae Koch, is a phytophagous pest that can cause significant yield losses in many agricultural crops, including fruits, cotton, vegetables, and ornamentals. To date, 3877 host species have been reported around the world in both outdoor crops and greenhouses. In this paper, we present the common methods to control this pest including chemical and biological practices. While synthetic acaricides have been widely used to manage T. urticae, in recent years, interest in pesticides derived from plants has increased considerably as a result of environmental concerns and pest population resistance to conventional pesticides. Some botanical pesticides can be easily produced, are relatively efficient against pests, and with few exceptions, their mammalian toxicity and persistence in the environment is low. Thus, the use of plant extracts appears to be a promising alternative strategy for pest management. The present paper reviews studies on the biocidal activities of plant extracts, including essential oils, against T. urticae, a plant-feeding mite found worldwide and a serious agricultural and home garden pest. 相似文献
80.
BACKGROUND: The pea aphid, Acyrthosiphon pisum (Harris), is a cosmopolitan pest that attacks a wide range of legume crops and vectors important plant virus diseases. In this project, essential oils from the leaf (L) and bark (B) of Laurelia sempervirens (Ruiz & Pavón) Tul. (L) and Drimys winteri JR Forster & G Forster (D) were extracted, and their deterrent and insecticidal activities were tested under laboratory conditions. RESULTS: By use of GC‐MS, safrole was found as the main constituent in LL and LB oils, while the main constituents were more diverse in DL and DB oils. In the deterrent bioassays with A. pisum under choice conditions, the four oils were active, with LL being the most active, followed by LB, DB and DL. The respective deterrence indices were 1.0, 0.89, 0.87 and 0.46 when aphids were exposed for 24 h to 4 µL mL?1. Although there was no aphid mortality when oils were sprayed on faba bean leaves before aphid infestation, there was 58 and 42% mortality when settled aphids were directly sprayed with 4.0 µL mL?1 of LL and LB respectively; DB and DL oils caused ≤18% mortality. In a third series, the essential oils of LL and LB caused 100% mortality when applied at a dose of 64 µL L?1 air by fumigation to faba bean plants infested with A. pisum; at the same dose, DB and DL oils caused 68 and 63% mortality respectively. When fumigation was limited to 2 h, the respective LC50 values for LL and LB oils were 10.6–14.3 µL L?1 air and 9.8–13.2 µL L?1 air. CONCLUSION: Because of their high deterrent and insecticidal activities, the essential oils from leaf and bark of L. sempervirens may be explored as potential natural aphicides. Copyright © 2010 Society of Chemical Industry 相似文献