全文获取类型
收费全文 | 5716篇 |
免费 | 293篇 |
国内免费 | 3篇 |
专业分类
林业 | 269篇 |
农学 | 135篇 |
基础科学 | 33篇 |
830篇 | |
综合类 | 919篇 |
农作物 | 259篇 |
水产渔业 | 423篇 |
畜牧兽医 | 2665篇 |
园艺 | 153篇 |
植物保护 | 326篇 |
出版年
2021年 | 78篇 |
2020年 | 92篇 |
2019年 | 103篇 |
2018年 | 95篇 |
2017年 | 97篇 |
2016年 | 116篇 |
2015年 | 73篇 |
2014年 | 128篇 |
2013年 | 233篇 |
2012年 | 224篇 |
2011年 | 316篇 |
2010年 | 160篇 |
2009年 | 146篇 |
2008年 | 261篇 |
2007年 | 297篇 |
2006年 | 304篇 |
2005年 | 279篇 |
2004年 | 288篇 |
2003年 | 269篇 |
2002年 | 268篇 |
2001年 | 114篇 |
2000年 | 108篇 |
1999年 | 97篇 |
1998年 | 75篇 |
1997年 | 67篇 |
1996年 | 69篇 |
1995年 | 54篇 |
1994年 | 48篇 |
1993年 | 49篇 |
1992年 | 67篇 |
1991年 | 91篇 |
1990年 | 77篇 |
1989年 | 72篇 |
1988年 | 63篇 |
1987年 | 51篇 |
1986年 | 75篇 |
1985年 | 78篇 |
1984年 | 50篇 |
1983年 | 53篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 47篇 |
1979年 | 37篇 |
1978年 | 50篇 |
1975年 | 37篇 |
1974年 | 45篇 |
1973年 | 33篇 |
1972年 | 39篇 |
1971年 | 39篇 |
1970年 | 32篇 |
排序方式: 共有6012条查询结果,搜索用时 21 毫秒
51.
Paula de Aguiar Silva Gleidson Giordano Pinto de Carvalho Aureliano José Vieira Pires Stefanie Alvarenga Santos Douglas dos Santos Pina Robério Rodrigues Silva Carlindo Santos Rodrigues Luis Henrique Almeida de Matos Carlos Emanuel Eiras Daiane Novais-Eiras Wilson Souza Nunes 《Tropical animal health and production》2018,50(4):721-726
In this study, we evaluated the effects of including cassava wastewater in the diet on the feeding behavior of feedlot lambs in 35 male uncastrated Santa Inês × Dorper crossbred lambs at an approximate age of 3 months, with an average live weight of 20.0?±?3.4 kg. Diets were formulated with hay of cassava shoots (roughage) and a concentrate based on corn and soybean, with a roughage:concentrate ratio of 50:50, plus inclusion of cassava wastewater at the levels of 0, 12, 24, 36, or 48 g/kg of the total diet. Feeding behavior was evaluated between the 46th and 52nd days of the experiment. Increasing cassava wastewater levels in the diet reduced (P?<?0.05) the intakes (kg/day) of dry matter and neutral detergent fiber as well as the efficiency of rumination (g/cud and g/h) of dry matter and neutral detergent fiber. The other behavioral parameters were not affected by wastewater inclusion in the diet. Therefore, the inclusion of up to 48 g/kg of cassava wastewater on fresh matter of diets is not recommended for feedlot lambs. 相似文献
52.
53.
Removal of hemangiosarcoma cells from canine blood with a cell salvage system and leukocyte reduction filter 下载免费PDF全文
54.
Single and multiple dose pharmacokinetics of a novel mirtazapine transdermal ointment in cats 下载免费PDF全文
William Buhles Jessica M. Quimby Daizie Labelle Valentine S. Williams 《Journal of veterinary pharmacology and therapeutics》2018,41(5):644-651
Single and multiple dose pharmacokinetics (PK) of mirtazapine transdermal ointment applied to the inner ear pinna of cats were assessed. Study 1 was a randomized, cross‐over single dose study (n = 8). Cats were treated once with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner ear pinna (treatment) or administered orally (control) and then crossed over after washout. Plasma was collected predose and at specified intervals over 96 hr following dosing. Study 2 was a multiple dose study (n = 8). Cats were treated daily for 14 days with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner pinna. Plasma was collected on Day 13 predose and at specified intervals over 96 hr following the final dose. In Study 1, single transdermal administration of mirtazapine resulted in mean Tmax = 15.9 hr, Cmax = 21.5 ng/mL, AUC0‐24 = 100 ng*hr/mL, AUC0‐∞ = 260 ng*hr/mL and calculated half‐life = 26.8 hr. Single oral administration of mirtazapine resulted in mean Tmax = 1.1 hr, Cmax = 83.1 ng/mL, AUC0‐24 = 377 ng*hr/mL, AUC0‐∞ = 434 ng*hr/mL and calculated half‐life = 10.1 hr. Mean relative bioavailability (F) of transdermal to oral dosing was 64.9%. In Study 2, daily application of mirtazapine for 14 days resulted in mean Tmax = 2.1 hr, Cmax = 39.6 ng/mL, AUC0‐24 = 400 ng*hr/mL, AUC0‐∞ = 647 ng*hr/mL and calculated half‐life = 20.7 hr. Single and repeat topical doses of a novel mirtazapine transdermal ointment achieve measurable plasma concentrations in cats. 相似文献
55.
The impact of truncating data on the predictive ability for single‐step genomic best linear unbiased prediction 下载免费PDF全文
Jeremy T. Howard Tom A. Rathje Caitlyn E. Bruns Danielle F. Wilson‐Wells Stephen D. Kachman Matthew L. Spangler 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2018,135(4):251-262
Simulated and swine industry data sets were utilized to assess the impact of removing older data on the predictive ability of selection candidate estimated breeding values (EBV) when using single‐step genomic best linear unbiased prediction (ssGBLUP). Simulated data included thirty replicates designed to mimic the structure of swine data sets. For the simulated data, varying amounts of data were truncated based on the number of ancestral generations back from the selection candidates. The swine data sets consisted of phenotypic and genotypic records for three traits across two breeds on animals born from 2003 to 2017. Phenotypes and genotypes were iteratively removed 1 year at a time based on the year an animal was born. For the swine data sets, correlations between corrected phenotypes (Cp) and EBV were used to evaluate the predictive ability on young animals born in 2016–2017. In the simulated data set, keeping data two generations back or greater resulted in no statistical difference (p‐value > 0.05) in the reduction in the true breeding value at generation 15 compared to utilizing all available data. Across swine data sets, removing phenotypes from animals born prior to 2011 resulted in a negligible or a slight numerical increase in the correlation between Cp and EBV. Truncating data is a method to alleviate computational issues without negatively impacting the predictive ability of selection candidate EBV. 相似文献
56.
Northern Lake Huron (Ontario, Canada) supports the largest concentration of freshwater salmonid cage culture farms in Canada and receives inputs of domestic‐strain rainbow trout (Oncorhynchus mykiss) through escapement. We assessed the potential effects of these domestic fish on the naturalised rainbow trout of this ecosystem by comparing their respective ecologies. Mature adults were sampled from spawning tributaries, primarily in spring, and to a lesser extent in fall. Fish of domestic origin comprised ~80% of rainbow trout sampled from sites near cage culture facilities but <20% of rainbow trout sampled from more distant sites. Domestic adults in spawning condition (gametes free‐flowing) were present in the spawning tributaries in both spring and fall sampling seasons, whereas naturalised fish in spawning condition were only observed in the spring. Domestic adults were younger and smaller (in length), appeared to have shorter lifespan and had a higher male to female ratio compared with their naturalised counterparts. Growth rates (change in length with age) of naturalised and domestic females in the wild were similar, but domestic males grew more slowly than naturalised males. Domestic females also produced smaller eggs than naturalised females. Food web positions (inferred from δ13C and δ15N) of domestic and naturalised fish were very similar but varied more strongly with body size in the former. Domestic‐strain rainbow trout of cage culture origin can survive, grow and attempt to spawn in northern Lake Huron and have the potential to compete for food, mates and spawning habitat with naturalised rainbow trout. 相似文献
57.
Precision Agriculture - Golf course superintendent’s knowledge of variability may be an overlooked and underutilized tool for precision turfgrass management (PTM). This case study used a... 相似文献
58.
59.
60.
Elayna Cristina da Silva Maciel Edivaldo Sampaio de Almeida Filho William Bertoloni Janessa Sampaio de Abreu 《Journal of the World Aquaculture Society》2014,45(1):35-44
Different stunning methods (carbon dioxide [CO2] and hypothermia) used in industrial fish processing were compared with asphyxia in air, which is used in traditional fishing, to evaluate the effects of these methods on the stress responses and the meat quality of the Amazon hybrid surubim, Pseudoplatystoma fasciatum female × Leiarius marmoratus male. After the application, blood and behavioral indicators were evaluated. Following death by gill cutting, the fish were gutted, and analyses of muscle pH, rigor mortis, the exudation of the meat, and coloration were performed. Significantly higher levels of cortisol and glucose were exhibited by the fish subjected to asphyxia than by the fish stunned by either CO2 or hypothermia. The fish subjected to asphyxia displayed decreasing muscle pH during the first 2 h after death and showed higher rates of rigor mortis after 3 h than the fish that were stunned by the other two methods. The asphyxia is a practice that exposes fish to suffering by causing an increase in stress responses, which affects meat quality. The immersion of fish in water and ice (hypothermia) for 5 min was more effective stunning method than the use of CO2, resulting in higher loss of sensibility and greater welfare. 相似文献