全文获取类型
收费全文 | 344篇 |
免费 | 30篇 |
专业分类
林业 | 27篇 |
农学 | 4篇 |
基础科学 | 6篇 |
39篇 | |
综合类 | 4篇 |
农作物 | 6篇 |
水产渔业 | 142篇 |
畜牧兽医 | 126篇 |
园艺 | 11篇 |
植物保护 | 9篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 1篇 |
2020年 | 7篇 |
2019年 | 2篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 13篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 7篇 |
2009年 | 22篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 7篇 |
2003年 | 16篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有374条查询结果,搜索用时 890 毫秒
81.
R. R. Sharitz D. C. Adriano J. E. Pinder III J. C. Luvall T. G. Ciravolo 《Journal of plant nutrition》2013,36(12):1671-1698
Growth and macronutrient uptake in two species of cattail, Typha latifolia and T. domingensis, were determined during an annual growth cycle in Par Pond, a thermally‐graded nuclear reactor cooling reservoir in South Carolina. Shoots of the same age class were sampled periodically from the initiation of growth in early spring to senescence in late autumn. Although differences between thermal regimes were mostly statistically non‐significant, growth and macronutrient uptake, especially of N, P, and K, tended to be enhanced by elevated water temperatures. The pattern for growth and N, P, and K uptake in decreasing order were: “Warm”; > “Intermediate”; > “Ambient”; regimes. The non‐significant statistics were attributed to large between‐stand and between‐temperature regime variations. Both Typha species exhibited sharp declines in N, P, and K concentrations in the shoots, and some decline in the rhizomes, early in the growing season, followed by either a more gradual decline or leveling off of concentrations until senescence. Calcium in shoots of both species increased with season, whereas Mg remained fairly constant. Thermal effluents can alter the growth form of Typha, as confirmed by the elimination of T. domingensis in the “Warm”; regime, and can affect their mineral nutrition. 相似文献
82.
Zucchini squash (Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO3):ammonium (NH4) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO3:NH4 ratio (1:0, 1:1, 1:3, or 3:1) treatments. Changing the original nitrogen (N) form ratio significantly affected plant growth, fruit yield, nutrient element, and water uptake. Growth of plants was better when NO3‐N (1:0) was the sole form of N than when NH4‐N was part of the N treatment. Fruit yields for plants fertilized with 1:0 or 1:3 N‐form ratio were double those of plants grown continuously with 3:1 N ratio. The largest leaf area and plant water use were obtained with 1:0 N ratio treatment Total uptake of calcium (Ca), magnesium (Mg), and potassium (K) decreased with increasing NH4‐N proportion in the nutrient solution which suggest NH4‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO3‐N source fertilizer through the vegetative growth stage and by shifting the NO3:NH4 ratio during the reproductive phase. 相似文献
83.
84.
Black walnut (Juglans nigra L.) produces both valuable lumber and a nut crop. Because of this, it is an important tree for agroforestry plantings in
the Midwest USA. However, during processing of the nut crop, the outer tissue of the nut (husks) accumulates in great quantities.
Applying this material to pastures is a possible method of disposal. However, black walnut has been implicated in allelopathic
interactions with numerous plant species and may inhibit the growth of pasture species. Greenhouse and field studies and a
chemical analysis of the husks were conducted to determine the effects of applying walnut husks to orchardgrass (Dactylis glomerata L.) or red clover (Trifolium pratense L.) pastures. Applying husks at rates up to 68 Mg ha−1 to pot-grown orchardgrass resulted in root and shoot yields that were greater than in pots receiving no husks. Field studies
indicated that orchardgrass and red clover benefited from the application of husks. For orchardgrass, significant increases
in growth occurred when husks were applied at a rate of 34 Mg ha−1 while red clover responded to rates up to 68 Mg ha−1. A chemical analysis of husks indicated that significant quantities of N and K were present in walnut husks. A whole effluent
toxicity test (WETT) indicates that runoff from walnut husk-treated pastures, at the rates used in this study, would not adversely
affect aquatic organisms. 相似文献
85.
Kevin T. Corley BSc BVMSm PhD MRCVS Harold C. McKenzie III DVM MS Lisa M. Amoroso DVM Martin O. Furr DVM DACVIM 《Journal of Veterinary Emergency and Critical Care》2000,10(4):267-276
Seven critically ill foals that continued to be hypotensive despite fluid resuscitation and the infusion of dobutamine and/or dopamine were treated with an infusion of norepinephrine (noradrenaline). The norepinephrine was administered concurrently with dobutamine, and the combination therapy was titrated by use of indirect mean arterial pressure measurements. The highest dose of norepinephrine used was 1.5 mcg/kg/min. In six foals the administration of norepinephrine was associated with an increase in blood pressure. In one foal the mean arterial pressure did not increase in response to the doses of norepinephrine administered. All of the foals experienced an increase in urine output coincident with the start of the norepinephrine infusion. Three of the foal survived to hospital discharge. 相似文献
86.
Peter M. Groffman James M. Tiedje Delbert L. Mokma Stephen Simkins 《Landscape Ecology》1992,7(1):45-53
Large scale analyses of biogeochemical processes are necessary for understanding anthropogenic effects on global climate and
environmental quality. Regional scale estimates of denitrification from forest soils in southern lower Michigan USA were produced
by stratifying the region into landscape experimental units using soil texture and natural drainage classes, and extrapolating
data to larger areas using a geographic information system (GIS). Previous landscape-scale research established relationships
between soil texture and drainage and denitrification and quantified annual denitrification N loss in nine soil texture/drainage
groups. All forest soils within the region (64 series) were assigned to one of these nine groups based on their texture and
drainage characteristics and were assigned an annual denitrification N loss value. A regional estimate of denitrification
was produced by multiplying the areal extent of each of the nine soil groups by their annual denitrification N loss value.
Loam-textured soils underlie 47% of the regional forest and accounted for 73% of the forest denitrification. Sandy soils were
found under 44% of the regional forest but produced only 5% of the regional denitrification. Clay loam soils underlie 9% of
the regional forest and produced 22% of the denitrification. Annual denitrification N loss for the region was estimated as
1.4×107 kg N/yr. We used denitrification enzyme activity (DEA) as a proxy for annual denitrification N loss to determine if the relationship
between denitrification and soil texture and natural drainage that we observed at the landscape scale held up at the regional
scale. DEA was measured in 22 soils across the region and was strongly related to soil texture and natural drainage (r2=0.61), suggesting that extrapolation of data from the landscape to the regional scale was justified. 相似文献
87.
Joseph D. Moxley Waldemar Rossi Alejandro Buentello Camilo Pohlenz Delbert M. Gatlin Joseph R. Tomasso 《Journal of the World Aquaculture Society》2014,45(2):192-198
The continued expansion of intensive aquaculture activities requires that substitutes for fish meal‐based protein be identified. In this study, we evaluated partial (50 and 75%) replacement of fish meal in red drum, Sciaenops ocellatus, diets with soy protein concentrate (S) and barley protein concentrate (B). Growth, feed efficiency, survival, tolerance to low temperature, and tolerance to handling in warm, hypersaline water were evaluated. Only the diet with a 50% replacement of fish meal with S yielded results comparable to fish fed a nonsubstituted fish meal diet. However, the low‐temperature studies were complicated by differences in mean fish weight among the groups. The results of this study indicate S may be partially substituted for fish meal in red drum diets. 相似文献
88.
89.
Ronald S. Veazey David W. Horohov James L. Krahenbuhl H. Wayne Taylor Julian L. Oliver Theron G. Snider III 《Comparative immunology, microbiology and infectious diseases》1996,19(4):289-304
The accumulation of various T cell subsets in Bcg-susceptible (C57BL/6) and -resistant (C3H/HeN) strains of mice were compared following an intraperitoneal infection with Mycobacterium paratuberculosis. Groups of mice from both strains were killed at 3, 5, 10, 15, 30, and 150 days after infection and lymphocytes were harvested from the peritoneal exudate cells (PEC), spleen, intestinal epithelial lymphocytes (IEL), lamina propria lymphocytes (LPL), Peyer's patches, and mesenteric lymph node (MLN) and labelled with monoclonal antibodies to CD3, CD4, CD8, γδ TCR, CD25, and CD44 for flow cytometric analysis. Uninfected C3H/HeN mice had higher proportions of CD4+ cells in the spleen, MLN, LPL, IEL and Peyer's patches, while uninfected C57BL/6 mice had higher proportions of CD8+ and/or γδ T cells. Significant increases in accumulation of CD8+ and γδ T cells were detected in the peritoneum and other tissues in both strains of mice after infection. Higher CD4/CD8 ratios were observed in most lymphoid tissues of C3H/HeN mice, while increased proportions of CD8+ and/or γδ T cells were present in C57BL/6 mice. These results indicate that significant differences in T cell profiles exist between these two strains of mice, both inherently and in response to infection with M. paratuberculosis. Innately lower levels of CD4+ cells and/or higher percentages of CD8+ and γδ T cells may play a role in the increased susceptibility of C57BL/6 mice to infection with M. paratuberculosis. 相似文献
90.
Carrie M. Van De Wiele DVM Daniel F. Hogan DVM Henry W. Green III DVM Nolie K. Parnell DVM 《Journal of Veterinary Cardiology》2008,10(2):155-161
Superior vena caval syndrome is a rare, but reported complication of transvenous pacemaker implantation in humans. This syndrome can occur secondary to fibrotic and/or thrombotic obstruction of venous blood flow into the right atrium. The therapeutic approach depends on the suspicion of the presence of an active thrombus and may include antithrombotics, angioplasty and/or surgical venoplasty. We describe two dogs that developed severe pleural effusion secondary to stricture formation in the cranial vena cava 4 years after dual chamber transvenous pacemaker implantation. The stenosis was most likely due to fibrosis secondary to the transvenous pacemaker leads. Balloon angioplasty of the lesion resulted in resolution of the pleural effusion in both patients. Balloon angioplasty appears to be a viable therapeutic approach in dogs with cranial vena caval syndrome caused by focal stenotic lesions. 相似文献