全文获取类型
收费全文 | 1512篇 |
免费 | 113篇 |
国内免费 | 2篇 |
专业分类
林业 | 117篇 |
农学 | 41篇 |
基础科学 | 6篇 |
313篇 | |
综合类 | 168篇 |
农作物 | 47篇 |
水产渔业 | 235篇 |
畜牧兽医 | 509篇 |
园艺 | 62篇 |
植物保护 | 129篇 |
出版年
2024年 | 6篇 |
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 29篇 |
2020年 | 37篇 |
2019年 | 53篇 |
2018年 | 53篇 |
2017年 | 48篇 |
2016年 | 61篇 |
2015年 | 58篇 |
2014年 | 44篇 |
2013年 | 83篇 |
2012年 | 101篇 |
2011年 | 110篇 |
2010年 | 91篇 |
2009年 | 70篇 |
2008年 | 94篇 |
2007年 | 82篇 |
2006年 | 89篇 |
2005年 | 77篇 |
2004年 | 72篇 |
2003年 | 79篇 |
2002年 | 55篇 |
2001年 | 23篇 |
2000年 | 16篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有1627条查询结果,搜索用时 0 毫秒
31.
Catherine Taverny Isabelle Ortusi Charles Roqueplo Mario Lepage Patrick Lambert 《Ecology of Freshwater Fish》2012,21(1):87-99
Abstract – Habitat requirements of lamprey ammocoetes (Petromyzon marinus and Lampetra genus) were investigated, for the first time, from shallow to deep waters, at different spatial scales across the Gironde‐Dordogne continuum, thanks to a water suction dredge. Fish‐habitat relationships were assessed through two complementary statistical analyses: habitat‐use curves and habitat suitability models using the Boosted Regression Trees (BRT) technique. Analyses were performed on a small‐size data set that was characterised by the low prevalence of lamprey. The sea lamprey larvae occurred in deeper areas than their Lampetra genus counterparts. ‘Pools’ of 2 m’ depth and more were optimal habitats for the former species. Among the environmental variables retained to model lamprey occurrences, the mesohabitat (a categorical variable) was demonstrated to be highly influential, in terms of fine grain‐size substratum and vegetation cover. These preliminary results suggest that monitoring using the water suction dredge method may contribute to sea lamprey conservation. 相似文献
32.
33.
Treatment of 4th and 5th instar larvae of Heliothis virescens with different amounts of fenoxycarb induced an increase in weight of the 5th larval instar, prolongation of the 5th larval instar period, or the formation of dauer larvae. No effects were observed during the 4th instar and the moult to the 5th larval instar. To check whether these effects were due to persistence of fenoxycarb in treated larvae, metabolism of this chemical was analysed. Larvae were fed with radio-labelled fenoxycarb at the first day of the 4th or at the first day of the 5th larval instar. Behaviour of the radio-labelled compounds was followed during each instar. At the time of gut purge, the whole of the radio-labelled material was excreted. The effects observed during the 5th instar of 4th-instar-treated larvae do not appear to be due to the persistence of fenoxycarb. The main metabolites of fenoxycarb were identified using coupled gas chromatography and mass spectrometry. 相似文献
34.
Armando García-Ortega E. A. Huisman Patrick Sorgeloos Johan Verreth 《Journal of the World Aquaculture Society》2001,32(3):317-329
Abstract.— The protein quality of carboxymethylcellulose microbound diets (MBDs) made with decapsulated cysts of Artemia andlor fishmeal as protein sources was used as an indicator of their suitability as starter feed for fish larvae. Studies on the proximate, fatty acid and amino acid composition. in vitro protein digestibility. diet solubility, and protein structure were combined with an in vivo feeding experiment with African catfish Clarias gariepinus larvae to evaluate the protein quality of the MBDs and a commercial diet. The growth of catfish larvae was higher when fed Artemia -based MBDs than with fishmeal-based MBDs, despite the higher protein and amino acid content of the latter. The in vitro protein digestibility was high for all the MBDs in comparison to a commercial diet. Differences were found in the protein molecular weight among the diets. Most of the proteins in the fishmeal-based diets had low molecular weight in the range between 7.4 and 49.2 kDa. The Artemia-based MBDs had larger protein fractions between 29.4 and 82 kDa. Decapsulated cysts improved the utilization of the MBDs when used in combination with fishmeal. Besides the effect of chemical attractants, the explanation for the positive effect of Artemia has yet to be elucidated. However, attention should be given to interactions between nutrients (e.g., protein-lipid) in live food, which might have an effect on the functional properties of food proteins. 相似文献
35.
This paper reports the results of a 2 × 2 factorial experiment on bush snap beans ‘Oregon 1604’. The treatments were 2 contrasted irrigation regimes and 2 contrasted plant densities, and were applied in 1978 and repeated in 1979. Data were collected on the number of flowers and pods, and pod size, at each node of the terminal inflorescence (6-T) of the main stem, and at each node of the oldest inflorescence (2-A) at Node 2. High and low plant densities were 45 and 18 plants m?2 in 1978 and 54 and 33 plants m?2 in 1979. High temperatures, frequently above 32°C, prevailed during bloom and pod development in 1978, but for the most part occurred only during the week prior to bloom in 1979. Inflorescences 6-T and 2-A usually formed 4 and 3 RN's, respectively, in 1978 and 3 and 2 RN's in 1979. The flowers at the proximal nodes of each inflorescence all opened within a few days of one another (duration of flowering at proximal nodes between 3 and 5 days); the flowering-periods of adjacent nodes overlapped, and the flowering period increased acropetally within the inflorescence (duration of flowering at distal nodes between 7 and 13 days). In general, number of flowers, pods formed, pods harvested and percent set decreased acropetally within each inflorescence. The rate of acropetal decline was lessened by high irrigation or low plant density. In both years, high irrigation increased the percent set of all RN's of the 2-A inflorescences, but few other consistent effects between years were observed. The 2 most proximal RN's together produced 93% or more of the yield of each inflorescence. High irrigation significantly increased the total number of pods harvested from these RN's of inflorescences 6-T and 2-A, and low density had a similar effect on 2-A. 相似文献
36.
Ellsworth MA Brown MJ Fergen BJ Ficken MD Tucker CM Bierman P TerHune TN 《Veterinary therapeutics : research in applied veterinary medicine》2003,4(2):120-127
A combination vaccine (Bovi-Shield FP4 + L5, Pfizer Animal Health) containing modified-live virus (MLV) components against bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus BVDV), parainfluenza virus-3 (PI3), bovine respiratory syncytial virus (BRSV), and inactivated cultures of Leptospira canicola, grippotyphosa, hardjo, icterohaemorrhagiae, and pomona was evaluated for safety in pregnant beef and dairy animals. Heifers vaccinated prebreeding with the minimum immunizing dose (lowest antigen level initiating immunizing effects) of the vaccine's MLV BHV-1 or BVDV components and during pregnancy (approximately 200 days of gestation) with vaccine containing 10x doses of the same BHV-1 and BVDV components delivered live, healthy calves that were determined to be serologically negative (titer less than 1:2) for neutralizing antibodies to BHV-1 and BVDV prior to nursing. Additionally, in three field safety studies, previously vaccinated cows and heifers that received a field dose (vaccine containing antigen levels required for commercial sale of the MLV combination vaccine during either the first, second, or third trimester of pregnancy had abortion rates similar to those of pregnant cows and heifers vaccinated during the same stage of pregnancy with sterile water diluent. 相似文献
37.
Byron CR Orth MW Venta PJ Lloyd JW Caron JP 《American journal of veterinary research》2003,64(6):666-671
OBJECTIVE: To characterize potential mechanisms of action of glucosamine inhibition of matrix metalloproteinase (MMP) expression and activity in lipopolysaccharide (LPS)-stimulated equine chondrocytes. SAMPLE POPULATION: Chondrocytes cultured from samples of metacarpophalangeal articular cartilage collected from cadaveric limbs of horses. PROCEDURE: The effect of glucosamine on MMP activity in conditioned medium from LPS-stimulated cartilage explants was determined by a colorimetric assay with azocoll substrate. Treatments consisted of negative and positive controls, glucose (50 mM), and glucosamine (50, 25, 6.25, 3, and 1.5 mM). The influence of glucosamine on MMP synthesis was determined in chondrocytes in pellet culture incubated with LPS (20 microg/mL). Concentration of MMP-13 was quantified in spent medium via ELISA; nonspecific MMP activity was determined via azocoll digestion in organomercurial-activated medium. Effects of glucosamine on MMP mRNA concentration in similarly treated chondrocytes were determined by northern blot hybridization with MMP-1, -3, and -13 probes. Statistical analyses were performed with 2-way ANOVA. RESULTS: Glucosamine had no effect on activated MMP activity but inhibited MMP protein expression, as determined by azocoll digestion (glucosamine, 3 to 50 mM) and MMP-13 ELISA (glucosamine, 1.5 to 50 mM). Resting mRNA concentrations for MMP-1, -3, and -13 mRNA were significantly lower in cultures exposed to glucosamine at concentrations of 50 and 25 mM than those of positive controls. CONCLUSIONS AND CLINICAL RELEVANCE: Glucosamine appears capable of pretranslational, and possibly also translational, regulation of MMP expression; data suggest a potential mechanism of action for chondroprotective effects of this aminomonosaccharide. 相似文献
38.
Holbrook TC Munday JS Brown CA Glover B Schlievert PM Sanchez S 《Journal of the American Veterinary Medical Association》2003,222(5):620-3, 601-2
A 3-year-old Thoroughbred gelding was examined because of clinical signs of pneumonia and shock. Mucous membrane petechiation and ventral edema were observed and considered to be a result of vasculitis. Epidermal necrosis developed on the distal portions of the limbs. The horse had a persistent high fever that was unresponsive to nonsteroidal anti-inflammatory treatment, and Staphylococcus aureus was isolated from a nasal swab specimen and 2 transtracheal wash fluid samples. Antimicrobial, anti-inflammatory, and supportive treatment resulted in clinical improvement. However, resolution of the pulmonary infection required long-term (42 days) antimicrobial administration. Staphylococcus aureus strains isolated from this horse were positive for the toxic shock syndrome toxin-1 gene and were shown to produce toxic shock syndrome toxin-1, the causative factor in toxic shock syndrome in humans. The horse's clinical signs were attributed to toxic shock syndrome secondary to pulmonary S. aureus infection. 相似文献
39.
40.
Van de Walle GR Favoreel HW Nauwynck HJ Van Oostveldt P Pensaert MB 《Veterinary microbiology》2002,86(1-2):51-57
Addition of pseudorabies virus (PrV)-specific polyclonal immunoglobulins to PrV-infected monocytes induces internalization of plasma membrane anchored viral glycoproteins. This process may interfere with antibody-dependent cell lysis and resembles the well-studied physiological endocytosis process. A confocal study was designed to investigate whether the major cellular components, involved in physiological endocytosis (clathrin, actin, dynein and microtubules), play a role in this virological internalization process. In order to visualize the interaction of endosomes, which contain the internalized viral glycoproteins, with clathrin, actin, dynein and microtubules, a double labeling of viral glycoproteins and different cellular proteins was performed. Porcine monocytes were inoculated with the PrV-strain 89V87 at a multiplicity of infection of 50 for 13h. After the addition of FITC-labeled porcine polyclonal PrV-specific antibodies, cells were fixed with para-formaldehyde at different time points and afterwards permeabilized. The different cellular components were visualized with monoclonal antibodies and a Texas Red-conjugate, with the exception of actin, which was stained with phalloidin-Texas Red. The cells were analyzed by confocal microscopy. A clear co-localization was observed between the viral glycoproteins and clathrin and dynein during the internalization process. The microtubules were in close contact with the internalized vesicles. For actin no co-localization could be observed. It can be stated that clathrin, dynein and microtubules, important components during physiological endocytosis, are also of importance during the antibody-induced internalization of viral glycoproteins. 相似文献