全文获取类型
收费全文 | 4081篇 |
免费 | 388篇 |
国内免费 | 1篇 |
专业分类
林业 | 311篇 |
农学 | 171篇 |
基础科学 | 21篇 |
810篇 | |
综合类 | 170篇 |
农作物 | 276篇 |
水产渔业 | 520篇 |
畜牧兽医 | 1762篇 |
园艺 | 86篇 |
植物保护 | 343篇 |
出版年
2024年 | 7篇 |
2023年 | 44篇 |
2022年 | 117篇 |
2021年 | 186篇 |
2020年 | 212篇 |
2019年 | 238篇 |
2018年 | 234篇 |
2017年 | 230篇 |
2016年 | 199篇 |
2015年 | 139篇 |
2014年 | 192篇 |
2013年 | 256篇 |
2012年 | 318篇 |
2011年 | 318篇 |
2010年 | 169篇 |
2009年 | 165篇 |
2008年 | 215篇 |
2007年 | 184篇 |
2006年 | 156篇 |
2005年 | 120篇 |
2004年 | 100篇 |
2003年 | 98篇 |
2002年 | 88篇 |
2001年 | 63篇 |
2000年 | 59篇 |
1999年 | 42篇 |
1998年 | 30篇 |
1997年 | 17篇 |
1996年 | 25篇 |
1995年 | 19篇 |
1994年 | 13篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1977年 | 6篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1969年 | 4篇 |
1968年 | 6篇 |
排序方式: 共有4470条查询结果,搜索用时 15 毫秒
991.
Bruno Corrêa da Silva Felipe do Nascimento Vieira José Luiz Pedreira Mouriño Norha Bolivar Walter Quadros Seiffert 《Aquaculture Research》2016,47(2):612-623
Organic salts may improvement the animal performance, increasing the efficiency of nutrient utilization and modifying the intestinal microbiota. This study aimed to evaluate the effects of sodium butyrate and sodium propionate supplementation at different levels of dietary inclusions in the growth of Litopenaeus vannamei. In total, seven diets were evaluated: a control diet (without supplementation) and three diets from each sodium salt, propionate and butyrate, in concentrations of 0.5%, 1% and 2%. We used 21 tanks of 6000 L stocked with 150 shrimps (2.53 ± 0.03 g). The shrimps fed diets supplemented with propionate and butyrate, in all concentrations, increased their final weight. The feed efficiency, nitrogen retention, protein efficiency rate, survival and yield of shrimps fed the diet containing 2% butyrate were higher in comparison with control treatment. The shrimps supplemented with butyrate also showed lower counts of Vibrio sp. in the intestine. The shrimps fed the diet supplemented with butyrate and propionate also showed higher values of serum agglutination titre. Thus, it is possible to conclude that dietary supplementation with propionate and butyrate in different dietary concentrations modify the intestinal microbiota and improves the growth of L. vannamei. 相似文献
992.
Carlos Andre Amaringo Cortegano Aline Marculino de Alcntara Allana Feitoza da Silva Cludia Maiza Fernandes Epifnio Sunique Po Cordeiro Bentes Vanessa Jorge dos Santos Jesuí Vergílio Visentainer Ligia Uribe Gonalves 《Aquaculture Research》2019,50(4):1291-1299
The need for a sustainable aquaculture is increasing the use of plant ingredients in replacement to fishmeal and fish oil in diets for tambaqui Colossoma macropomum, which is leading to not detectable levels of docosahexaenoic acid (DHA) in its flesh. We evaluated the effect of a finishing plant diet supplemented with 5% of microalgae meal from Schizochytrium sp. (MD) on tambaqui growth, on proximal composition and fatty acid content of its flesh, comparing it to a non‐supplemented diet. One hundred and sixty‐two fish (489.67 g) were distributed into six tanks (2,000 L) and fed the experimental diets for a 90‐day period. Three fish per tank were euthanized for analyses every 15 days. The MD did not affect the growth and proximal composition of fish flesh. The MD increased the DHA content (from 14.81 to 38.60 mg/g of lipids) and the n‐3:n‐6 ratio (from 0.16 to 0.51) in the flesh of fish, beginning on the 15th day and reaching the highest DHA content on the 71st day (39.81 mg/g of lipids). We recommend C. macropomum to be fed with a finishing diet supplemented with microalgae meal for 71 days before slaughter to improve the DHA content and n‐3:n‐6 ratio in the flesh. 相似文献
993.
Ane T Laugen Georg H Engelhard Rebecca Whitlock Robert Arlinghaus Dorothy J Dankel Erin S Dunlop Anne M Eikeset Katja Enberg Christian Jørgensen Shuichi Matsumura Sébastien Nusslé Davnah Urbach Loїc Baulier David S Boukal Bruno Ernande Fiona D Johnston Fabian Mollet Heidi Pardoe Nina O Therkildsen Silva Uusi‐Heikkilä Anssi Vainikka Mikko Heino Adriaan D Rijnsdorp Ulf Dieckmann 《Fish and Fisheries》2014,15(1):65-96
Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries‐induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life‐history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries. 相似文献
994.
The concentrations of 14 mineral elements (Na, K, Ca, P, Mg, Fe, Zn, Cu, Mn, Co, Cr, Ni, Cd and Pb), together with pH, moisture, ash and NaCl content, were determined in 38 feeds commonly available in Europe for trout (starter, fingerling, grower, brood), salmon (starter, fingerling, grower), eel (grower), and larval fishes.Large differences in the mineral composition, particularly the trace elements Fe, Zn, Cu, Mn, Co and Pb, exist within and between the different feed categories tested. The results obtained are discussed in the context of available information on the dietary mineral requirements of these fish species. 相似文献
995.
Tricaine as an anaesthetic for larvae and juveniles of Lophiosilurus alexandri,a carnivorous freshwater fish 下载免费PDF全文
996.
The expansion of Integrated Pest Management (IPM), including biological control, has had several positive consequences for the agricultural environment and participants in the production chain. To enable successful operation and applications of biological control, production of insects used for rearing natural enemies (parasitoids and predators) must be optimized to reduce time and costs and improve production both qualitatively and quantitatively. The present study evaluated the effect of wheat varieties, the main component of artificial diets for Ephestia kuehniella, on the reproductive performance and biological parameters of this flour moth, which is used for mass production of Trichogramma spp. (Hymenoptera: Trichogrammatidae) and other parasitoids and predators. Four varieties of wheat were compared: BRS 327, BRS Marcante, BRS Parrudo, and KBR, with and without the addition of corn E. kuehniella reared on 97% BRS 327 wheat flour + 3% nutritional yeast had the best biological parameters and substitution of corn for about half of the wheat increased the number of eggs per female. 相似文献
997.
Rosario Martínez Alejandro García-Beltrn Garyfallia Kapravelou Cristina Mesas Laura Cabeza Gloria Perazzoli Palmira Guarnizo Alberto Rodríguez-Lpez Roberto Andrs Vallejo Milagros Galisteo Pilar Aranda Jose Prados María Lpez-Jurado Consolacin Melguizo Jesus M. Porres 《Marine drugs》2022,20(5)
Nannochloropsis gaditana is a microalga with interesting nutritional and functional value due to its high content of protein, polyunsaturated fatty acids, and bioactive compounds. However, the hardness of its cell wall prevents accessibility to these components. This work aimed to study the effect of a treatment to increase the fragility of the cell wall on the bioavailability of its nutrients and functional compounds. The antioxidant and antiproliferative capacity of functional extracts from treated and untreated N. gaditana was assessed, and the profile of bioactive compounds was characterized. Furthermore, to study the effect of treatment on its nutrient availability and functional capacity, an in vivo experiment was carried out using a rat experimental model and a 20% dietary inclusion level of microalgae. Functional extracts from treated N. gaditana exhibited higher antioxidant activity than the untreated control. Furthermore, the treated microalga induced hypoglycemic action, higher nitrogen digestibility, and increased hepatic antioxidant activity. In conclusion, N. gaditana has interesting hepatoprotective, antioxidant, and anti-inflammatory potential, thus proving itself an ideal functional food candidate, especially if the microalga is treated to increase the fragility of its cell wall before consumption. 相似文献
998.
Mateus N Silva AM Vercauteren J de Freitas V 《Journal of agricultural and food chemistry》2001,49(10):4836-4840
Several anthocyanin-derived pigments that showed UV-visible spectra different from those of the original grape anthocyanins were detected by HPLC-DAD analysis in 1-year-old bottled Port wines from the Douro region. Among these, three malvidin 3-glucoside derived pigments were detected in large amounts, representing approximately 60% of the total anthocyanidin monoglucosides content. These pigments were isolated, purified, and identified by LSI-MS and NMR ((1)H, DQF-COSY, ROESY, HSQC, and HMBC) techniques. The major pigment is malvidin 3-glucoside pyruvic adduct, previously characterized, and the other two corresponded to its respective acetyl and coumaroyl glucoside derivatives. The latter is reported for the first time in red wines. 相似文献
999.
Muratore G Licciardello F Restuccia C Puglisi ML Giudici P 《Journal of agricultural and food chemistry》2006,54(3):860-863
The influence of concentration and water activity (a(w)) on the formation of 5-hydroxymethyl-2-furancarboxaldehyde (HMF) in thermally treated grape must was evaluated. Must was cryoconcentrated and then heated to study the pure effect of sugar concentration. Moreover, NaCl was added to the must to lower a(w), maintaining the same sugar concentration, with the purpose of evaluating the pure effect of a(w). Finally, the influence of minimal pH changes on the formation of HMF was evaluated by means of a model solution. The results showed that a(w) and sugar concentration are both determinant in the formation of HMF in grape must. Sugar concentration influences the reaction by supplying substrates; low a(w) enhances the formation of HMF by changing the equilibrium in the dehydration step of the reaction. 相似文献
1000.
Martínez-Villaluenga C Gulewicz P Pérez A Frías J Vidal-Valverde C 《Journal of agricultural and food chemistry》2006,54(19):7391-7398
Microbial population and bioactive amine profile and levels of two lupin species (Lupinus luteus L. cv. 4492 and Lupinus angustifolius L. var. zapaton) and fenugreek (Trigonella foenum-graecum L.) seeds as affected by germination were investigated. Microbial population increased considerably mainly in the first stage of germination (2 days), then small changes in bacterial numbers were observed up to 5 days to levels between 7.8 and 8.9 log colony-forming units/g. Microorganisms belonging to the Enterobacteriaceae family were dominant for the legumes tested. Ungerminated legume seeds contained putrescine, cadaverine, histamine, tyramine, spermidine, and spermine. Bioactive amine levels found in fenugreek seeds were between 3- and 4-fold higher than those found in lupin seeds. The highest total amine levels were found in fenugreek seeds [162 mg/kg of dry weight (dw)], followed by L. angustifolius var. zapaton seeds (84 mg/kg of dw) and, finally, L. luteus cv. 4492 (46 mg/kg of dw) seeds. The concentration of individual amines showed a gradual rising trend during the germination period in all tested sprouts, reaching levels >3 times higher than those found in ungerminated seeds. After 5 days of germination, the fenugreek sprouts contained the highest amount of total bioactive amines. Tyramine was the predominant amine in both lupin varieties, whereas cadaverine was the main bioactive amine detected in fenugreek. The results of this work thus indicated that microbial population and biogenic amine levels in the studied lupin and fenugreek sprouts are not a risk for healthy consumers or for individuals with restricted activity of detoxification enzymes. 相似文献