全文获取类型
收费全文 | 20866篇 |
免费 | 302篇 |
国内免费 | 3篇 |
专业分类
林业 | 3922篇 |
农学 | 1467篇 |
基础科学 | 180篇 |
3728篇 | |
综合类 | 1125篇 |
农作物 | 2278篇 |
水产渔业 | 2324篇 |
畜牧兽医 | 2723篇 |
园艺 | 1210篇 |
植物保护 | 2214篇 |
出版年
2023年 | 34篇 |
2022年 | 79篇 |
2021年 | 116篇 |
2020年 | 131篇 |
2019年 | 167篇 |
2018年 | 2914篇 |
2017年 | 2836篇 |
2016年 | 1335篇 |
2015年 | 214篇 |
2014年 | 187篇 |
2013年 | 284篇 |
2012年 | 1080篇 |
2011年 | 2444篇 |
2010年 | 2277篇 |
2009年 | 1439篇 |
2008年 | 1574篇 |
2007年 | 1836篇 |
2006年 | 285篇 |
2005年 | 317篇 |
2004年 | 315篇 |
2003年 | 319篇 |
2002年 | 224篇 |
2001年 | 93篇 |
2000年 | 132篇 |
1999年 | 68篇 |
1998年 | 30篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 28篇 |
1994年 | 12篇 |
1993年 | 25篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 29篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1969年 | 13篇 |
1968年 | 8篇 |
1967年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Quereda JJ Gómez S Seva J Ramis G Cerón JJ Muñoz A Pallarés FJ 《The Veterinary record》2012,170(1):21
The concentrations of haptoglobin (Hp), C-reactive protein (CRP) and serum amyloid A (SAA) were measured in wasted pigs, first to evaluate their usefulness in the diagnosis of infectious, wasting diseases in pigs, and second, to evaluate whether their concentrations can distinguish the lymphoid depletion score in the lymph tissues of wasted affected pigs. Fifty-three wasted pigs and seven specific pathogen free (SPF) pigs were postmortem examined. Gross lesions were evaluated and samples for histopathological, immunohistochemical, molecular biology and microbiological analysis were taken. Thirty-one pigs were diagnosed as postweaning multisystemic wasting syndrome (PMWS) and 22 as porcine respiratory disease complex (PRDC). Lymphoid depletion degree in lymph tissues of PMWS and PRDC affected pigs was determined. Serum Hp was significantly higher in pigs with PRDC in comparison with the PMWS affected pigs. Serum CRP concentration was significantly lower in pigs with PRDC than in PMWS affected pigs (P<0.001). CRP and SAA levels increased with the lymphoid depletion score, presenting statistical differences between pigs with no depletion and pigs with low, moderate or severe lymphoid depletion (P<0.05, P<0.05 and P<0.001 for CRP and P<0.01, P<0.01 and P<0.01 for SAA, respectively). Hp was higher in pigs with no or low depletion compared with the pigs suffering severe lymphoid depletion (P<0.001 and P<0.05, respectively). 相似文献
62.
Mitchell B. Stephenson Jerry D. Volesky Walter H. Schacht Nevin C. Lawrence Jon Soper Jessica Milby 《Strength and Conditioning Journal》2019,72(1):103-111
Several studies have evaluated the spatial distribution of cool- and warm-season grasses across different topographic positions in the Nebraska Sandhills, but limited research has explored topographic differences in total plant production or production of plant functional groups in relation to variable amounts of precipitation. This study evaluated how spring and growing season precipitation influenced plant production at four topographic positions common in the eastern Nebraska Sandhills. Plant production data were collected from annually moved grazing exclosures in mid-June (peak cool-season grass production) and mid-August (peak warm-season grass production) during a 17-yr period from 2001 to 2017. Total plant production and precipitation use efficiency were 35 ? 58% greater on interdune positions, and precipitation marginal response for total plant production was more sensitive to increases in spring and growing season precipitation on interdune compared with dune positions in both mid-June and mid-August. The greater precipitation marginal response of total plant production on interdune positions was driven primarily by greater increases in cool-season grass production with increasing spring or growing season precipitation. Warm-season grass precipitation marginal response was not different among the topographic positions, but production was 23 ? 70% greater on interdune compared with dune topographic positions in mid-August. When differences in the amount of each topographic position at the study location were accounted for, growing season precipitation explained 49% of the variation for total plant production in mid-August, but spring precipitation only explained 23% of the variation for total plant production in mid-June. Because of the differential response of plant production at dune and interdune positions, incorporating the relative amount of each topographic position into estimates of plant production at the pasture or ranch scale will provide better information for adjusting stocking rates to more accurately match animal demand with forage availability. 相似文献
63.
Circulating oxidative stress status in dromedary camels infested with sarcoptic mange 总被引:2,自引:0,他引:2
Oxidative stress is an imbalance between radical-generating and radical-scavenging activity, resulting in oxidation products
and tissue damage. This study was aimed to evaluate the status of oxidative stress indices in blood of camels naturally infested
with S. scabiei. Forty-seven male camels (Camelus dromedaries) were divided according to the extent of the infested area with Sarcoptes scabiei into four groups, mild (MID, n = 12), moderate (MOD, n = 10), severely infested (SEV, n = 10) and healthy control group (n = 15). Blood was used for determination of red cell count (RBC), hemoglobin (Hb), packed cell volume (PCV), serum nitric
oxide (NO•, a free radical), ascorbate and albumin concentrations, and erythrocytic values of malondialdehyde (MDA, a marker of lipid
peroxidation), protein carbonyls (PC, an indicator of protein oxidation), glutathione (GSH) superoxide dismutase (SOD) and
catalase (CAT). Decreased levels (P < 0.05) of RBC, Hb, PCV, albumin and ascorbate were noticed in MOD and SEV compared to controls with the lowest values (P < 0.05) in SEV except for ascorbate, where MOD did not differ from SEV. Compared to controls, NO• gradually increased (P < 0.05) in MID followed by MOD and SEV, whereas MDA and PC were higher (P < 0.05) in MOD and SEV. PC was higher (P < 0.05) in MOD than SEV. In addition, the antioxidants GSH, SOD and CAT were higher (P < 0.05) in MID and lower (P < 0.05) in MOD and SEV compared to controls. GSH was lower (P < 0.05) in SEV compared to MOD. Besides, Hb was negatively correlated with NO• (r = −0.68, P < 0.001), MDA (r = −0.53, P < 0.001) and PC (r = −0.73, P < 0.001). In conclusion, dromedary sarcoptosis is accompanied by a state of oxidative stress process, which increased by
increasing the area of infestation, and may contribute to the pathogenesis of the disease. 相似文献
64.
65.
Oral administration of yeast, Saccharomyces cerevisiae, enhances the cellular innate immune response of gilthead seabream (Sparus aurata L.) 总被引:3,自引:0,他引:3
Ortuño J Cuesta A Rodríguez A Esteban MA Meseguer J 《Veterinary immunology and immunopathology》2002,85(1-2):41-50
The effects of including lyophilised whole yeast, Saccharomyces cerevisiae, in the diet on the seabream innate immune response were investigated. Gilthead seabream (Sparus aurata L.) specimens were fed four different diets for 4 weeks: a commercial diet as control and the same diet supplemented with 1, 5 or 10 g/kg yeast. After 1, 2 and 4 weeks, serum complement titres, as a humoral parameter, and phagocytic, respiratory burst, myeloperoxidase and natural cytotoxic activities of head-kidney leucocytes, as cellular parameters, were evaluated. The results showed that yeast supplements enhanced all the latter responses, but not the humoral response. This enhancement was dose-dependent except for the cytotoxic activity that was only stimulated by the lower dose of yeast assayed. As yeast cell walls are able to enhance the seabream cellular innate immune response, these results support the possible use of whole yeast as natural inmunostimulants in common fish diets. 相似文献
66.
67.
Tatsuya Nakayama Michio Jinnai Ryuji Kawahara Khong Thi Diep Nguyen Nam Thang Tran Thi Hoa Le Kieu Hanh Pham Ngoc Khai Yoshinori Sumimura Yoshimasa Yamamoto 《Tropical animal health and production》2017,49(1):31-37
Reports of livestock infections with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E) are increasing. Based on interviews conducted over a 6-month period, we found that veterinarians in the Vietnamese province of Thai Binh prefer to prescribe colistin-based drugs (CBD) in chicken farms. We aimed to clarify whether CBD use selects for strains of colistin-resistant ESBL-E. With the cooperation of seven local households, we detected ESBL-E in chickens’ feces after treating chickens with CBD. Phylogenetic groupings and the presence of CTX-M/AmpC genes were determined, and the multi-antibiotic susceptibility of isolates was analyzed. Our results showed that ESBL-E presented in seven chickens’ feces from two households. Seventy-two percent of ESBL-E isolates harbored CTX-M9 and the phylogenetic group A; the colistin minimum inhibitory concentration (MIC) of all isolated ESBL-E ranged from 0.064 to 1 μg mL?1. Moreover, ESBL-E isolates were used to experimentally select for colistin resistance, and the effect of commercial CBD on ESBL-E was investigated. The results showed that an ESBL-E strain with a colistin MIC of 4 μg mL?1 was able to grow in media with CBD. Although CBD treatment was effective, in vitro experiments demonstrated that ESBL-E can easily acquire colistin resistance. Therefore, restrictions on colistin use are necessary to prevent the emergence of colistin-resistant bacteria. 相似文献
68.
Ouédraogo-Koné S Kaboré-Zoungrana CY Ledin I 《Tropical animal health and production》2008,40(2):155-164
Foliage of Afzelia africana, Pterocarpus erinaceus and Khaya senegalensis, from 10 trees per species, was collected every two weeks during the late dry, rainy and cool season to determine the seasonal
effects on chemical composition. Fifteen rams of the Djallonké breed, weighing on average 20.0 kg, were used to evaluate the
voluntary intake and digestibility of hay of A. gayanus, foliage of A. africana (as a sole feed), and A. africana, P. erinaceus and K. senegalensis offered with 30% of the diet as A. gayanus hay. The crude protein (CP) content of A. africana, and P. erinaceus decreased significantly from the late dry season to the cool season when that of K. senegalensis tended to increase. The mean CP of A. africana, P. erinaceus and K. senegalensis differed significantly (173 g, 139 g and 114 g/kg DM, respectively). The DM intake of A. africana offered with hay (571 g/d) or as a sole feed (598 g/d) were not significantly different, but was higher than that of P. erinaceus (428 g/d) and K. senegalensis (298 g/d). The digestibility calculated by difference of DM and CP of A. africana (582 g/kg DM and 795 g/kg CP, respectively) did not differ significantly from A. africana as a sole feed, but were higher than for the other species. The nutritive value of A. africana seems to justify the high preference of herders for this species. 相似文献
69.
S. Kennou Sebei R. Bergaoui M. Ben Hamouda R. G. Cooper 《Tropical animal health and production》2009,41(7):1427-1438
The aim of the current investigation was to determine wild ostrich reproductive behaviour in Orbata Nature Reserve by observing
16 hens and 28 cocks over a seven-year period. Intense laying commenced in January, one month after the cessation of the rainy
season, and 92% of the eggs were produced during the dry season (January to May, peaking in March). Over the seven years,
1,322 eggs were laid in 69 nests, which corresponded to an annual average production of 19.2 ± 9.1 eggs/nest and 11.8 eggs/hen.
24 nests (34.78%) were non-brooded, 17 nests (24.64%) were deserted in the course of incubation, and 28 nests (40.58%) possessed
hatched eggs. All the non-incubated nests had egg losses equivalent to 46.6 ± 12.6%. Hatchability success of incubated eggs
was 41.9 ± 12.0%. Ostriches tended to dig their nests adjacent to the reserve enclosure which had direct access by road and
track, the latter subjecting them to human disturbance and predation. The systematic obstruction of these nests stimulated
ostriches to build additional nests within the reserve perimeter. The authors discussed the results recorded in an ostrich
flock in relation to the environmental factors (climatic factors, food disponibility and predation) and suggested possibilities
for improved wildlife management. 相似文献
70.