全文获取类型
收费全文 | 12153篇 |
免费 | 874篇 |
专业分类
林业 | 1216篇 |
农学 | 467篇 |
基础科学 | 59篇 |
2807篇 | |
综合类 | 746篇 |
农作物 | 518篇 |
水产渔业 | 941篇 |
畜牧兽医 | 4819篇 |
园艺 | 317篇 |
植物保护 | 1137篇 |
出版年
2024年 | 21篇 |
2023年 | 106篇 |
2022年 | 143篇 |
2021年 | 255篇 |
2020年 | 248篇 |
2019年 | 189篇 |
2018年 | 578篇 |
2017年 | 548篇 |
2016年 | 514篇 |
2015年 | 402篇 |
2014年 | 458篇 |
2013年 | 700篇 |
2012年 | 939篇 |
2011年 | 876篇 |
2010年 | 491篇 |
2009年 | 396篇 |
2008年 | 765篇 |
2007年 | 707篇 |
2006年 | 575篇 |
2005年 | 591篇 |
2004年 | 539篇 |
2003年 | 502篇 |
2002年 | 406篇 |
2001年 | 293篇 |
2000年 | 271篇 |
1999年 | 237篇 |
1998年 | 78篇 |
1997年 | 63篇 |
1996年 | 44篇 |
1995年 | 65篇 |
1994年 | 39篇 |
1993年 | 36篇 |
1992年 | 79篇 |
1991年 | 67篇 |
1990年 | 63篇 |
1989年 | 57篇 |
1988年 | 53篇 |
1987年 | 47篇 |
1986年 | 48篇 |
1985年 | 48篇 |
1984年 | 42篇 |
1983年 | 35篇 |
1979年 | 37篇 |
1974年 | 26篇 |
1973年 | 21篇 |
1972年 | 22篇 |
1971年 | 23篇 |
1970年 | 27篇 |
1969年 | 25篇 |
1968年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
de Ramos Eduarda Kalena Kirsch Pazdiora Paulo Cesar Dallagnol Leandro José de Souza Mayara Rodrigues de Araujo Filho Jeronimo Vieira 《植物病害和植物保护杂志》2023,130(1):211-214
Journal of Plant Diseases and Protection - Tobacco (Nicotiana tabacum L.) is one of the major nonfood crops in the Southern of Brazil. During 2019/2020 and 2020/2021 crop seasons, Root Knot... 相似文献
32.
Three trickle irrigation schedules, two of which were scheduled according to soil water potential ( soil) (tensiometer method) and daily stem contraction (DSC) (dendrometer method) respectively and the other one was a schedule of restricted water supply, were applied to a mature peach orchard.The annual water application based on soil was greater than that based on DSC. However, tree growth, fruit size and leaf water potential (leaf) on the trees in the dendrometer scheduling plot did not differ from those in the tensiometer scheduling plot while the premature fruit drop and fruit bud initiation were greatly different. The restricted water supply treatment limited significantly both tree and fruit growth. In addition, the lower leaf was observed on the trees in this plot.Further study shows that use of the dendrometer method for scheduling irrigation satisfies the water needs of the plant and that the tensiometer method is less accurate.Abbreviations leaf
leaf water potential
- soil
soil water potential
- DSC
daily stem contraction
- LVDT
linear variable displacement transducer
- PET
potential evapotranspiration 相似文献
33.
Faridy Juárez-Chairez Milagros Stephanie Cid-Gallegos María Gabriela Meza-Márquez Ofelia Cristian Jiménez-Martínez 《Plant foods for human nutrition (Dordrecht, Netherlands)》2020,75(2):142-153
Plant Foods for Human Nutrition - Chickpea is one of the most consumed legumes worldwide. Among their benefits are the high protein concentration that reflects not only at the nutritional level but... 相似文献
34.
Machado Rui Godinho Sérgio Guiomar Nuno Gil Artur Pirnat Janez 《Landscape Ecology》2020,35(6):1291-1308
Landscape Ecology - The Portuguese montado is an agro-silvopastoral system, similar to the Spanish dehesa, known for its cultural, economic and ecological value. Despite its importance, contrasting... 相似文献
35.
Y. C. Agrofoglio V. C. Delfosse M. F. Casse H. E. Hopp I. Bonacic Kresic V. Ziegler-Graff A. J. Distéfano 《Plant pathology》2019,68(6):1059-1071
Cotton blue disease (CBD) is the most important disease present in cotton crops in South America and cotton leafroll dwarf virus (CLRDV) is the causal agent. The disease has been controlled by sowing cotton varieties resistant to CLRDV. However, in the 2009/10 growing season, an outbreak due to an atypical CLRDV isolate (CLRDV-at) occurred in northwest Argentina. Although CLRDV and CLRDV-at genomes are very closely related, the symptoms they produce in cotton plants are quite different. P0 is the most divergent protein between the isolates and in CLRDV is a silencing suppressor protein. This work characterized the silencing suppressor activity of the P0 protein encoded by CLRDV-at (P0CL-at) and evaluated its role in Cbd-resistance break in cotton plants. It was demonstrated that P0CL-at, despite having a mutation in the consensus of the F-box-like motif, was able to suppress local RNA silencing, but displayed lower activity than P0CL. P0CL and P0CL-at showed no differences in the interaction with Gossypium hirsutum SKP1 orthologue (GSK1) and Nicotiana benthamiana SKP1 and both P0 proteins triggered destabilization of ARGONAUTE1. However, when the ability to enhance PVX symptoms was evaluated, P0CL-at was shown to be a weaker pathogenicity factor than P0CL in N. benthamiana. Interestingly, trans-expressed P0CL-at enabled CLRDV to systemically infect CBD-resistant plants, and a chimeric CLRDV-P0CL-at infectious clone succeeded in establishing infection in CBD-resistant cotton varieties with symptoms resembling those produced by CLRDV-at. These results strongly suggest that P0CL-at is the avirulence (Avr) determinant involved in breaking cotton Cbd gene-based resistance. 相似文献
36.
Wild olive (Olea europaea subsp. europaea var. sylvestris) is an important component of Mediterranean forests and a key genetic source for olive improvement programmes. Since 2009, a severe decline caused by Phytophthora cryptogea and P. megasperma has been detected in a protected wild olive forest of high ecological value (Dehesa de Abajo, Seville, Spain). In this natural forest, sampling of roots and soil was carried out on 25 wild olives with symptoms in 2014 and 2015. Apart from the already known P. cryptogea A1 and P. megasperma, a third Phytophthora species was consistently isolated from wild olive rootlets with symptoms. These isolates conformed morphologically with the newly described species P. oleae and were confirmed by analysis of their ITS regions and cox1 sequences. Temperature–growth relationships showed a maximum growth at 19.9 °C on carrot agar medium, making it the lowest temperature Phytophthora species infecting wild olive roots. Pathogenicity was confirmed on 1-year-old healthy wild olive seedlings and was similar to the previously known pathogenic phytophthoras. As temperature requirements are quite different, the three Phytophthora species may be active against wild olive roots in different seasons. However, the prevalence of P. oleae infecting wild olives in recent years could be due to its introduction as a new invasive pathogen. The probable invasive nature of P. oleae, together with increasing rain episodes concentrated in short periods frequent in southern Spain, would allow the outbreak of infections in wild olive forests, and also put cultivated olive orchards at risk. 相似文献
37.
Wilson Wasielesky Jr Paulo César Abreu Luis Henrique Poersch Fabiano Thompson Eduardo Luis Cupertino Ballester 《Aquaculture Research》2012,43(5):706-712
A reduction in light intensity may increase shrimp activity, although it may also negatively affect the development of photoautotrophic organisms present in biofilm, an important natural food source for shrimp. This experiment evaluated the influence of light intensity on biofilm development and on the growth of cultured Farfantepenaeus paulensis juveniles. Six cages were deployed in a shrimp culture pond and stocked with 60 juveniles (0.72 ± 0.03 g). Three cages were randomly chosen and covered with five layers of polyamide net to reduce light incidence (shaded treatment), while the other three cages were not covered (control treatment). Biofilm chlorophyll a and microorganism abundance, as well as shrimp growth, were monitored during the experiment. Chlorophyll a concentration and the abundance of bacteria and flagellates were significantly lower in the shaded treatment (P<0.05). After 75 rearing days, shrimp stocked in control treatment achieved significantly higher (5.98 g) (P<0.05) mean weight than shrimp reared in shaded treatment cages (5.13 g). Similarly, the biomass produced was also significantly higher (P<0.05) in the control treatment (322.92 g) than in the shaded treatment (287.31 g). The results of this study demonstrate that light intensity has a huge influence on shrimp performance mainly due to the increase in natural food availability. 相似文献
38.
Rémi Mongruel Olivier Thébaud 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3):163-181
ABSTRACT Most marine aquaculture activities remain strongly dependent on coastal ecosystems. In the case of shellfish farming, this dependency is related mainly to water quality and to the various ecological interactions resulting from the dynamics of coastal food webs. Such ecological constraints have influenced the overall evolution of blue mussel farming in the Mont-Saint-Michel Bay, leading producers to negotiate collective arrangements regarding production capacity and techniques and to develop production strategies at the farm level. This article presents an analysis of the location choices of mussel farmers in the Mont-Saint-Michel Bay based on an empirical investigation conducted in 2002. A typology of farms with respect to their land structure is developed in which some farms choose to concentrate their activity in a single part of the bay while others distribute their activity more widely. Determinants of the location choices of each farm category, including distance to port, natural productivity differentials, and predation of mussel stocks, are analyzed. The role of the institutional arrangements allowing mussel farmers to develop these location strategies is also discussed. 相似文献
39.
Gaspar Soria Miguel F. Lavín Iván Martínez‐Tovar Alberto Macías‐Duarte 《Aquaculture Research》2013,44(9):1383-1398
We evaluated recruitment of larvae of catarina scallop, Argopecten ventricosus, in the area of Puerto Peñasco, NE Gulf of California. We moored artificial collectors in six sites from June 2007 to August 2008 and replaced them every 2 months. We used monthly (July 2002–September 2011) sea surface temperature (SST, °C) and surface chlorophyll‐a concentration (SSChl, mg m?3) Aqua/MODIS satellite data to describe seasonal environmental behaviour study area. Also, we recorded bottom temperature at each site every 4 h, and every 2 months measured sea surface salinity, temperature and dissolved oxygen. We used a repeated measures anova to evaluate differences in the number of recruited spat between main factors, and analysed the presence of multimodal spat shell size frequency distributions. Overall, spat recruitment was negatively correlated with seawater temperature and showed higher spat recruitment abundances throughout winter, which is the season with the highest surface chlorophyll a concentration. We estimated multimodal shell size frequency distributions characterized by more than one modal size. The natural collection of A. ventricosus spat on artificial collectors in the area can be successfully performed over a protracted period (November–December to May–June). Our results extend the area where collection of A. ventricosus spat can be successful. 相似文献
40.
Raico E Laria Lamela Yanis Cruz Quintana Raquel Silveira Coffigny Mercedes Martínez Norma González Herrate 《Aquaculture Research》2008,39(12):1316-1321
Formalin is used in shrimp industry to eliminate ectoparasites and as a disinfectant. However, the effect of formalin on shrimp's defense mechanism is unknown. Several biomarkers were used to assess the immune response of juveniles of the shrimp Litopenaeus schmitti exposed to different concentrations of formalin (10, 25 and 50 mg L?1) during 24 and 48 h. Formalin concentrations of 25 and 50 mg L?1 produced a significant reduction in the total haemocyte count at both 24 and 48 h. Peroxidase and phenoloxidase activity did not show variations. The total protein concentration in haemolymph of shrimps was not significantly different between experimental groups. Histological analysis showed hyperplasia in the gills of animals exposed at 10 mg L?1 for 24 h; however, the exposure at 25 and 50 mg L?1 caused necrosis in gills, hepathopancreas and the antennal gland. 相似文献