全文获取类型
收费全文 | 1475篇 |
免费 | 174篇 |
专业分类
林业 | 137篇 |
农学 | 84篇 |
基础科学 | 14篇 |
344篇 | |
综合类 | 48篇 |
农作物 | 55篇 |
水产渔业 | 187篇 |
畜牧兽医 | 633篇 |
园艺 | 26篇 |
植物保护 | 121篇 |
出版年
2024年 | 3篇 |
2023年 | 27篇 |
2022年 | 24篇 |
2021年 | 66篇 |
2020年 | 77篇 |
2019年 | 68篇 |
2018年 | 107篇 |
2017年 | 116篇 |
2016年 | 106篇 |
2015年 | 63篇 |
2014年 | 83篇 |
2013年 | 95篇 |
2012年 | 111篇 |
2011年 | 116篇 |
2010年 | 63篇 |
2009年 | 41篇 |
2008年 | 71篇 |
2007年 | 66篇 |
2006年 | 65篇 |
2005年 | 83篇 |
2004年 | 55篇 |
2003年 | 47篇 |
2002年 | 29篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1985年 | 3篇 |
1969年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有1649条查询结果,搜索用时 562 毫秒
991.
Protein content and amino acid composition of eggs and endotrophic larvae from wild and captive fed sea urchin Paracentrotus lividus (Echinodermata: Echinoidea)
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Knowledge on the biochemistry of proteins and amino acids (AA) of eggs and larvae of echinoids is scarce and the possibility to modify their profiles by diet manipulations is unknown. The protein content of eggs, prisms and pre‐plutei and the amino acid composition of eggs of Paracentrotus lividus from captive broodstock fed prepared diets were analysed and compared with the ones obtained from wild broodstock. Diets differed on protein source (fish or soy meals) and on protein content (10–40% dry weight – DW). Total and soluble protein content of both eggs and larvae was higher than 400 g kg?1 DW and 200 g kg?1 DW respectively. Glycine was the most abundant free AA. Very few differences were found among P. lividus eggs and larvae biochemical parameters, suggesting that their AA composition can hardly be changed by broodstock diet manipulations. 相似文献
992.
Patrick Hainfellner Rafael Yutaka Kuradomi Thiago Gonalves de Souza Rafael Tomoda Sato Daniel Guimares Figueiredo‐Ariki Guilherme Antnio de Freitas Luciano Queiroz Wagner C. Valenti Patricia Moraes Valenti Wei Ge Sergio Ricardo Batlouni 《Aquaculture Research》2019,50(11):3382-3391
We evaluated the annual process of oocyte and ovarian development of the planktivorous Amazonian catfish, the mapará (Hypophthalmus marginatus), aiming to support captive reproduction for domestication. A total of 149 females were captured from the Tocantins River at the Tucuruí Dam (3°49'55"S, 49°39'9"W) in 13 sampling events. For each individual, we evaluated ovary histology and plasma steroid concentrations. Two annual reproductive cycles, with similar characteristics, including a long period of rest, a short vitellogenic stage and a well‐defined spawning season from November to March, were described. A 17β‐estradiol (E2) rise and a 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) peak were associated with vitellogenesis and spawning season, respectively, in the first cycle but not in the second reproductive cycle. In conclusion, the studied species presents a reproductive cycle similar to that of other migratory total spawners; however, unusually for this group of fish, there were three (but not two) batches of vitellogenic oocytes in “in maturation” and “mature” stage ovaries, pointing to the possibility of more than one spawn during the spawning season. 相似文献
993.
Marcus Frederico Martins Pinheiro Silvia Maria Guimarães de Souza & Leonardo José Gil Barcellos 《Aquaculture Research》2003,34(12):1047-1052
This experiment was conducted to evaluate the seminal characteristics of Nile tilapia males exposed to water‐borne 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP). Male Nile tilapia (Oreochromis niloticus L.) were exposed to the steroidal pre‐ovulatory pheromone 17,20βP, added to water at a concentration of 5×10?9 M. The pheromone‐exposed males had higher sperm volume and concentration. In addition, the spermatozoa contained in the sperm had higher motility and the motility duration was longer than ethanol‐exposed males (control group). The percentage of live spermatozoa was not affected by the treatments. Our results suggest that this pheromone can improve sperm quality characteristics and could become a non‐invasive method for enhancing spawning in Nile tilapia. 相似文献
994.
Daniele M. Nascimento Letícia R. Oliveira Luana L. Melo João C. Silva José M. Soman Karine T. Girotto Renan P. Eburneo Marcos R. Ribeiro-Junior Maria M. P. Sartori Tadeu A. F. Silva Júnior Antonio C. Maringoni 《Plant pathology》2020,69(7):1357-1367
Weeds are important alternative hosts of pathogens, responsible for the survival and spread of phytopathogenic bacteria. Our study evaluated the potential of weeds as hosts of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), causal agent of bacterial wilt, one of the main diseases of common beans. Cff survival was evaluated in the phyllosphere and in the rhizosphere of 21 weeds, in four experiments under field conditions, during the years 2018 and 2019. The aerial part of the plant was inoculated by spraying bacterial suspension (107 cfu/ml) of Cff, while the soil of the growing pots was infested with the same suspension. Cff survival was evaluated every 7 days, for 70 days. The identity of the bacterium was confirmed by PCR with the specific primers CffFOR2 and CffREV4, from strains recovered from all samples. Principal component analysis (PCA) showed that high temperatures and rainfall reduced Cff survival in the phyllosphere, while high temperatures reduced the survival of the bacterium in the rhizosphere. Our results demonstrated that Amaranthus viridis (family Amaranthaceae), Conyza bonariensis, Emilia fosbergii, Galinsoga parviflora, Gnaphalium purpureum (Asteraceae), Raphanus sativus, Lepidium virginicum (Brassicaceae), Commelina benghalensis (Commelinaceae), Ipomoea triloba (Convolvulaceae), Cyperus rotundus (Cyperaceae), Senna obtusifolia (Fabaceae), Digitaria insularis (Poaceae), Nicandra physalodes, and Solanum americanum (Solanaceae) are potential hosts for Cff. Their eradication in common bean fields is recommended, especially in fields with a history of bacterial wilt occurrence. 相似文献
995.
Paixão Sonália Ferreira Fritzen Juliana Torres Tomazi Alfieri Alice Fernandes Alfieri Amauri Alcindo 《Tropical animal health and production》2018,50(4):911-914
Tropical Animal Health and Production - Serological evidence shows that the bovine viral diarrhea virus (BVDV) infections are present in Brazilian dairy and beef water buffalo herds. As few reports... 相似文献
996.
da Rocha Ulisses Nunes Andreote Fernando Dini de Azevedo João Lúcio van Elsas Jan Dirk van Overbeek Leo S. 《Journal of Soils and Sediments》2010,10(2):326-339
Purpose
The role of dominant bacterial groups in the plant rhizosphere, e.g., those belonging to the phyla Acidobacteria and Verrucomicrobia, has, so far, not been elucidated, and this is mainly due to the lack of culturable representatives. This study aimed to isolate hitherto-uncultured bacteria from the potato rhizosphere by a combination of cultivation approaches. 相似文献997.
Oliveira AP Pereira JA Andrade PB Valentão P Seabra RM Silva BM 《Journal of agricultural and food chemistry》2007,55(19):7926-7930
Cydonia oblonga Miller leaves phenolic compounds were analyzed by reversed-phase HPLC/DAD and HPLC/UV. Qualitative and quantitative analysis of phenolics were carried out in a total of 36 samples of quince leaves from three different geographical origins of Northern (Bragan?a and Carrazeda de Ansi?es) and Central Portugal (Covilh?) and three collection months (June, August, and October of 2006). These leaves presented a common phenolic profile composed by nine compounds: 3- O-, 4- O- and 5- O-caffeoylquinic acids, 3,5- O-dicaffeoylquinic acid, quercetin-3- O-galactoside, quercetin-3- O-rutinoside, kaempferol-3- O-glycoside, kaempferol-3- O-glucoside, and kaempferol-3- O-rutinoside. 5- O-caffeoylquinic acid was the major phenolic compound (36.2%), followed by quercetin 3- O-rutinoside (21.1%). Quince leaves are characterized by higher relative contents of kaempferol derivatives than fruits (pulps, peels, and seeds), especially in what concerns kaempferol-3- O-rutinoside (12.5%). C. oblonga leaves total phenolic content was very high, varying from 4.9 to 16.5 g/kg dry matter (mean value of 10.3 g/kg dry matter), indicating that these leaves can be used as a good and cheap source of bioactive constituents. Significantly differences were observed in 3- O-caffeoylquinic and 3,5- O-dicaffeoylquinic acids contents, according to geographical provenance and harvesting month, suggesting a possible use of these compounds as geographical origin and/or maturity markers. 相似文献
998.
Ribeiro SG Martin DP Lacorte C Simões IC Orlandini DR Inoue-Nagata AK 《Phytopathology》2007,97(6):702-711
ABSTRACT Tomato chlorotic mottle virus (ToCMoV) is an emerging begomovirus species widely distributed throughout tomato-growing regions of Brazil. ToCMoV appears to have expanded its geographic range recently, invading tomato-growing areas that were free of begomovirus infection before 2004. We have determined the first complete genome sequence of an infectious ToCMoV genome (isolate BA-Se1), which is the first begomovirus species isolated in the northeast of Brazil. When introduced by particle bombardment into tomato, the cloned ToCMoV-[BA-Se1] DNA-A and DNA-B components caused typical chlorotic mottle symptoms. The cloned virus was whitefly-transmissible and, although it was infectious in hosts such as Nicotiana benthamiana, pepper, tobacco, and Nicandra physaloides, it was unable to infect Arabidopsis thaliana, bean, N. glutinosa, and Datura metel. Sequence and biological analyses indicate that ToCMoV-[BA-Se1] is a typical New World begomovirus sp. requiring both DNA-A and DNA-B components to establish systemic infections. Although evidence of multiple recombination events was detected within the ToCMoV-[BA-Se1] DNA-A, they apparently occurred relatively long ago, implying that recombination probably has not contributed to the recent emergence of this species. 相似文献
999.
Magalhães PJ Carvalho DO Guido LF Barros AA 《Journal of agricultural and food chemistry》2007,55(20):7995-8002
In this work, ergosterol and ergocalciferol were identified for the first time in hop. In addition, in this article, a simple and reliable analytical methodology for analysis of these compounds in different commercial forms of hop is presented. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (higher than 70%), repeatability (lower than 3 %), linearity ( r(2) > 0.9988) and limits of detection (ranging from 0.034 for ergocalciferol to 0.058 mg/L for ergosterol) and quantification (ranging from 0.113 for ergocalciferol to 0.195 mg/L for ergosterol). On the basis of standard additions applied with the optimized procedure and high-performance liquid chromatography with diode array detection, it appears that the Nugget hop plant (crop 2006) contains 1.84 +/- 0.09 microg/g of ergosterol and 1.95 +/- 0.05 microg/g of ergocalciferol. The identity of the compounds was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry in the positive ion mode. The presence of ergosterol here reported should have great potential for the assessment of hop as related to the fungal contamination proportion and hence the quality of this raw material. 相似文献
1000.
Ferreres F Sousa C Valentão P Andrade PB Seabra RM Gil-Izquierdo A 《Journal of agricultural and food chemistry》2007,55(25):10187-10193
The flavonoids present in passion fruit (Passiflora edulis) leaves were identified by a high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS) method. Sixteen apigenin or luteolin derivatives were characterized, which included four mono-C-glycosyl, eight O-glycosyl- C-glycosyl, and four O-glycosyl derivatives. With the exceptions of C-hexosyl luteolin and C-hexosyl apigenin, all the compounds exhibited a deoxyhexose moiety. Moreover, the uncommon C-deoxyhexosyl derivatives of luteolin and apigenin have been identified for first time in P. edulis by HPLC-DAD-MS/MS. The antioxidative capacity of passion fruit leaves was checked against DPPH radical and several reactive oxygen species (superoxide radical, hydroxyl radical, and hypochlorous acid), revealing it to be concentration-dependent, although a pro-oxidant effect was noticed for hydroxyl radical. 相似文献