全文获取类型
收费全文 | 1868篇 |
免费 | 97篇 |
专业分类
林业 | 158篇 |
农学 | 82篇 |
基础科学 | 9篇 |
592篇 | |
综合类 | 85篇 |
农作物 | 99篇 |
水产渔业 | 152篇 |
畜牧兽医 | 553篇 |
园艺 | 33篇 |
植物保护 | 202篇 |
出版年
2024年 | 1篇 |
2023年 | 24篇 |
2022年 | 33篇 |
2021年 | 59篇 |
2020年 | 75篇 |
2019年 | 77篇 |
2018年 | 68篇 |
2017年 | 78篇 |
2016年 | 72篇 |
2015年 | 60篇 |
2014年 | 83篇 |
2013年 | 147篇 |
2012年 | 130篇 |
2011年 | 173篇 |
2010年 | 88篇 |
2009年 | 87篇 |
2008年 | 127篇 |
2007年 | 112篇 |
2006年 | 98篇 |
2005年 | 81篇 |
2004年 | 68篇 |
2003年 | 57篇 |
2002年 | 60篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1965条查询结果,搜索用时 26 毫秒
991.
992.
Lan PingNicolas Brosse Laurent ChruscielPaola Navarrete Antonio Pizzi 《Industrial Crops and Products》2011,33(1):253-257
The extraction of condensed tannins from grape pomace was examined using a mixture water-sodium hydroxide at 120 °C. The extracts were characterized by solution 13C NMR and have showed characteristic consistent with that of condensed tannins with dominant procyanidin units. The tannin fractions reactivity toward formaldehyde was studied by gel time analysis and thermomechanical analysis in bending. It has been demonstrated that the extracts obtained by using 10% of NaOH (w/w) displayed promising properties for adhesive applications. 相似文献
993.
Pasquale Chiaiese Gianluca Ruotolo Antonio Di MatteoAmalia De Santo Virzo Anna De MarcoEdgardo Filippone 《Industrial Crops and Products》2011,34(1):1072-1078
In order to apply state-of-the-art molecular breeding techniques in fibre crop it is necessary to have a good knowledge of major polymer biosynthesis gene sequences and their expression pattern. Polymerase chain reaction was employed to isolate sequences of the major genes for lignin and cellulose biosynthesis in a kenaf cultivar. CeSA, 4cl, c4h, cad, and ccr gene primers were designed according to their conservative regions; partial sequences of lignin and cellulose biosynthesis genes were obtained. One actin II gene sequence was also isolated from the kenaf genome as a housekeeping gene to be employed in qPCR analysis. Expression levels of genes c4h, cad and CeSA in bark and core from plants harvested at three different growth stages were evaluated. Using qPCR analyses it was found that the expression levels of the two biosynthesis lignin genes in bark tissues increased during plant growth, while a negative trend was recorded in core tissues. In both bark and core, the quantity of lignin was positively correlated to plant growth while cellulose content decreased. 相似文献
994.
Lan Ping Antonio PizziZhou Ding Guo Nicolas Brosse 《Industrial Crops and Products》2011,34(1):907-914
The extraction of condensed tannins from grape pomace was examined using water medium in the presence of NaOH, Na2CO3, NaHCO3 eventually in the presence of Na2SO3. The tannin fractions reactivity towards formaldehyde was studied by gel time analysis and thermomechanical analysis in bending and it was demonstrated that despite of their lower phenolic contents, some of these extracts displayed promising properties for adhesive applications. A resin formulation in which the total content of tannin is 75% of the total resin solids content gave good results and was employed for the elaboration of the first grape pomace based-wood particleboard which passed relevant international standard specifications for interior-grade panels. 相似文献
995.
Diphasic sedimentation technique complemented by a statistical approach as a useful tool to the quantification and the determination of dynamics of eggs produced by adult monogenean parasitizing groupers,Epinephelus marginatus (Lowe, 1834), in captivity 下载免费PDF全文
Mercedes Gracenea Elena Cubero Humbert Salvadó Antonio Monleón 《Aquaculture Research》2016,47(3):830-837
Monogenean parasites create problems in confined fish, such as at aquaculture and aquariums facilities. Strategic timing of antihelminthic treatments should be based on the dynamics of monogenean egg production which requires egg quantification, but there is no standardized analytical method. The WHO diphasic sedimentation method for helminth quantification of eggs was applied in samples with tetrahedral and fusiform monogenean eggs from six specimens of confined groupers (Epinephelus marginatus) (31 m3 sea water tank; water temperature 21.1–14.4°C; photoperiod 9:53–15 h light; November 2011 to June 2012). Helminth eggs remain in the pellet, while most organic matter was removed forming a cap. In contrast, monogenean eggs are distributed within both the pellet and cap. The diphasic sedimentation method is suitable to quantify tetrahedral and total egg number by counting those eggs in the pellet and incorporing water temperature data to obtain a statistically significant model expression (R2 = 0.943; R2 = 0.809), while this approach only weakly predicted fusiform egg numbers (R2 = 0.297). Fusiform egg numbers declined along November–December, and increased in February–March, until June. Tetrahedral eggs decreased in November–December, but did not increase until March. The trend of egg populations and best time for antihelminthic treatment application can be set by WHO technique with the statistical approach proposed. 相似文献
996.
Paulo Roberto Campagnoli de Oliveira Filho Elisabete Maria Macedo Viegas Eliana Setsuko Kamimura Marco Antonio Trindade 《Journal Of Aquatic Food Product Technology》2013,22(3):222-237
This study evaluates the effects of inclusion level (60 to 100%) and washing cycles (0 to 2) of minced fish from Nile tilapia fillet by-products on proximate composition, mineral contents, color, hardness, and sensory acceptance of sausages. A complete 22 factorial experimental design was used. Regression models for protein, fat, moisture, minerals, color, and hardness were developed. The optimum combinations for the independent variables are sausages made with 100% non-washed minced fish, which represents a better use of by-products without generating washing residues, leading to less expensive sausage with higher nutritional value. 相似文献
997.
Juan Antonio De Anda-Montañez Ricardo Perez-Enriquez Susana Martínez-Aguilar Fidencio Hernández-Martínez Francisco Javier García-Rodríguez Alberto Amador-Buenrostro 《Fisheries Science》2013,79(1):21-32
This study reports the distribution, estimated abundance and biomass, and genetic population structure of the red crab Pleuroncodes planipes along the western coast of the Baja California Peninsula, Mexico. Using a hybrid conical net for fish and crustaceans, bottom trawls with stratified depth were performed at transect sites perpendicular to the coast. Red crab was observed to distribute widely in the study area, particularly in upwelling areas such as Bahia Magdalena and its surroundings, and the greatest catches were recorded at depths between 51 and 100 m, and between 201 and 300 m, with values of 2,297 and 3,223 kg/h of trawl, respectively. The population genetic analysis using mitochondrial DNA sequencing revealed no significant population differentiation. The total estimated biomass was 611,525 metric tons, supporting the proposal that the red crab is a viable exploitation resource in the study area. 相似文献
998.
Fabricio F. T. Domingos Ralph G. Thomé Fabio P. Arantes Antonio Carlos S. Castro Yoshimi Sato Nilo Bazzoli Elizete Rizzo 《Fish physiology and biochemistry》2012,38(6):1709-1719
River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodus argenteus, from the S?o Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34?km of the river after the dam (site 1) and the second 34–54?km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17β-estradiol and 17α-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions. 相似文献
999.
Rebeca Cerezuela Francisco Antonio Guardiola José Meseguer M. ángeles Esteban 《Fish physiology and biochemistry》2012,38(6):1729-1739
The present study assessed the effects of three orally administered microalgae (Nannochloropsis gaditana, Tetraselmis chuii and Phaeodactylum tricornutum) on different immune parameters and immune-related gene expression of gilthead seabream (Sparus aurata L.). Fish were fed a control or one of six experimental diets and sampled at 2 and 4?weeks of treatment. At the end of the trial, growth performance and different systemic and local immune activities were measured (natural haemolytic complement activity, IgM levels, phagocytosis and respiratory burst). The expression levels of different immune-associated genes (EF-1α, IgMH, TCR-β, MHCIα, MHCIIα, CSF-1R and β-defensin) were analysed in head-kidney and gut. Administration of N. gaditana and T. chuii resulted in a significant increase in haemolytic complement activity, phagocytic capacity, as well expression level of β-defensin, as well as MHCIIα and CSF-1R, respectively. The P. tricornutum-supplemented diet provoked immunostimulation, and very little effect on gene expression was observed. These results suggest that dietary microalgae enhance gilthead seabream defence activity, which could be very important in order to consider such microalgae as a possible additive in fish diets. 相似文献
1000.
Nutrient load estimation in the waste of Nile tilapia Oreochromis niloticus (L.) reared in cages in tropical climate conditions 下载免费PDF全文
We sought to estimate the nutrient load in the waste released into aquatic environments based on the feeding of Nile tilapia (Oreochromis niloticus, L.) reared in cages that were installed in artificial reservoirs. For the calculation, an analysis of the chemical composition of commercial feeds intended for this species in their various stages of production was conducted (N = 130). We combined this information with a meta‐analysis of published data from commercial producers in Brazil about expected feed intake, feed conversion and other animal production indices, and body composition. With these data, it was possible to estimate the load. We estimated that 18% of the feed given to the animals is not consumed and is lost in the aquatic environment. The calculated average digestibility was 71.97% for the organic matter in the diet, 84.06% for protein and 54.40% for phosphorus. The estimated nutrient deposition efficiency, with respect to what was actually consumed by the tilapia, was 26.39% for organic matter, 43.25% for protein and 34.07% for phosphorus. The total nutrient load in the waste per tonne of biomass of produced tilapias was estimated to be 1040.63 kg of organic matter, 44.95 kg of nitrogen and 14.26 kg of phosphorus, representing 78%, 65% and 72% of the respective nutrient amounts supplied by the feed. The information obtained in this study serves as a reference for predicting the potential impact of tilapia farming in reservoirs and to establish scientific parameters for the planning of this activity. 相似文献