全文获取类型
收费全文 | 11255篇 |
免费 | 738篇 |
国内免费 | 1篇 |
专业分类
林业 | 937篇 |
农学 | 406篇 |
基础科学 | 56篇 |
2330篇 | |
综合类 | 380篇 |
农作物 | 443篇 |
水产渔业 | 996篇 |
畜牧兽医 | 5178篇 |
园艺 | 173篇 |
植物保护 | 1095篇 |
出版年
2023年 | 78篇 |
2022年 | 112篇 |
2021年 | 240篇 |
2020年 | 221篇 |
2019年 | 154篇 |
2018年 | 460篇 |
2017年 | 502篇 |
2016年 | 491篇 |
2015年 | 362篇 |
2014年 | 450篇 |
2013年 | 621篇 |
2012年 | 791篇 |
2011年 | 678篇 |
2010年 | 373篇 |
2009年 | 350篇 |
2008年 | 570篇 |
2007年 | 518篇 |
2006年 | 418篇 |
2005年 | 459篇 |
2004年 | 375篇 |
2003年 | 353篇 |
2002年 | 299篇 |
2001年 | 256篇 |
2000年 | 249篇 |
1999年 | 219篇 |
1998年 | 48篇 |
1997年 | 38篇 |
1996年 | 50篇 |
1992年 | 135篇 |
1991年 | 115篇 |
1990年 | 109篇 |
1989年 | 128篇 |
1988年 | 120篇 |
1987年 | 124篇 |
1986年 | 114篇 |
1985年 | 103篇 |
1984年 | 81篇 |
1983年 | 75篇 |
1982年 | 45篇 |
1981年 | 57篇 |
1980年 | 50篇 |
1979年 | 103篇 |
1978年 | 92篇 |
1977年 | 83篇 |
1976年 | 53篇 |
1975年 | 47篇 |
1974年 | 99篇 |
1973年 | 70篇 |
1972年 | 93篇 |
1971年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The role of neutrophil apoptosis in the resolution of bovine mammary gland injury induced by intramammary administration of physiological buffered saline (PBS) or lipopolysaccharide (LPS) was investigated. Twenty mammary glands of five non-pregnant heifers were used in the two studies and each animal received both stimuli. Samples of cell populations were collected by mammary gland lavages before and 24, 48, 72 and 96 hours after treatment and examined by light microscopy and staining for myeloperoxidase (MPO). A marked influx of neutrophils into the mammary gland was observed 24 hours after stimulation. At the same time, apoptotic neutrophils and MPO-positive macrophages (MAC) were identified in the samples. The numbers increased to reach maximum values at 48 hours after stimulation with PBS and at 72 hours after stimulation with LPS. The observed differences in the length of the resolution period indicate that neutrophil viability can be modulated by delaying the apoptotic process. Apoptosis of neutrophils and their subsequent phagocytosis by MAC can be regarded as a significant mechanism in the removal of neutrophils from the acutely injured mammary glands and, hence, in the resolution of bovine mastitis. 相似文献
63.
Júlia P. Gonçalves Aleksandra Oliveira-Menezes Arnaldo Maldonado Junior Técia M.U. Carvalho Wanderley de Souza 《Veterinary parasitology》2013
Echinostomiasis is a food-borne, intestinal, zoonotic, snail-mediated helminthiasis caused by digenean trematodes of the family Echinostomatidae with seven species of the genus Echinostoma infecting humans or domestic and wildlife animals. Echinostoma paraensei is a peristomic 37-collar-spined echinostome belonging to the “revolutum group”. 相似文献
64.
Hernández Juan Augusto Lepe Marissa Macedo Rafael Arredondo Victalina Cortez Carlos Eliseo García Luis Jorge Prado Omar 《Tropical animal health and production》2017,49(1):173-178
Tropical Animal Health and Production - A study was conducted with the objective to characterize the morphology of Socorro Island Merino sheep. A total of 67 sheep, 62 females, 26 purebred and 36... 相似文献
65.
Gerardo Ordaz-Ochoa Aureliano Juárez-Caratachea Rosa Elena Pérez-Sánchez Rafael María Román-Bravo Ruy Ortiz-Rodríguez 《Tropical animal health and production》2017,49(5):1025-1033
The effect of spineless cactus intake (Opuntia ficus-indica) on blood glucose (BG) levels in lactating sows and its impact on daily and total feed intake (dFI?1 and TFI, respectively), body weight loss (BWL), and weaning-estrus interval length (WEI) were evaluated. Thirty-four hybrid (Yorkshire × Landrace × Pietrain) sows in lactation phase were used. Sows were divided into two groups: G1 (n = 17) where they received commercial feed and G2 (n = 17) provided with commercial feed plus an average of 2.0 ± 0.5 kg spineless cactus, based on a sow’s body weight. The variables evaluated were BG, dFI?1, TFI, BWL, and WEI. Statistical analysis was performed by using a fixed and mixed model methodology, under a repeated measurements experiment. Group effects were found on all analyzed variables (P < 0.05). The BG was lower in G2 (55.2 and 64.5 mg/dL pre- and post-prandial, respectively), compared to that in G1 (70.9 and 80.1 mg/dL pre- and post-prandial, respectively) (P < 0.05). G2 showed better performance than G1 for dFI?1, BWL, and WEI (P < 0.05) whose averages were 5.5 ± 1.8 kg, 7.4 ± 4.5%, and 5.3 ± 1.2 days, respectively. Averages for these variables in G1 were 4.7 ± 1.5 kg, 16.8 ± 4.6%, and 6.1 ± 1.6 days, respectively. Intake of spineless cactus reduced BG levels in lactating sows, generating greater dFI?1, lower BWL at the end of lactation, and a lower WEI. 相似文献
66.
67.
Identification of carcass and meat quality quantitative trait loci in a Landrace pig population selected for growth and leanness 总被引:1,自引:0,他引:1
Vidal O Noguera JL Amills M Varona L Gil M Jiménez N Dávalos G Folch JM Sánchez A 《Journal of animal science》2005,83(2):293-300
The identification of QTL related to production traits that are relevant for the pig industry has been mostly performed by using divergent crosses. The main objective of the current study was to investigate whether these growth, fatness, and meat quality QTL, previously described in diverse experimental populations, were segregating in a Landrace commercial population selected for litter size, backfat thickness, and growth performance. We have found QTL for carcass weight (posterior P > 0.75), cutlet weight (posterior P > 0.99), weight of ham (posterior P > 0.75), shoulders weight (posterior probability > 0.99), and shear firm-ness (posterior P > 0.99) on pig Chromosome 2. Moreover, QTL with posterior P > 0.75 for fat thickness between the 3rd and 4th ribs (Chromosome 7), rib weights (Chromosome 8), backfat thickness (Chromosomes 8, 9, and 10), and b Minolta color component (Chromosome 7) were identified. These results indicate that commercial purebred populations retain a significant amount of genetic variation, even for traits that have been selected for many generations. 相似文献
68.
Pathogenesis in visceral leishmaniosis is associated with depressed cellular immunity and a significant rise of antileishmanial antibodies. We assessed the relative levels of immunoglobulin E anti-Leishmania infantum, together with those of IgG, IgG1 and IgG2, using the enzyme-linked immunosorbent assay (ELISA) test, in non-infected and infected dogs with or without symptoms, and their association with symptoms to differentiate the stages of the infection. The expression of all immunoglobulins (IgG, IgG1, IgG2 and IgE) was higher in symptomatic dogs than in all other categories. IgG and IgG2 expression was higher in the infected asymptomatic group than in the non-infected group, whereas IgG1 and IgE expression was only higher in symptomatic animals. This correlation between the expression of IgG1 and IgE and the pathology of leishmaniosis points to their potential role as markers of the active disease. 相似文献
69.
Martínez CM Peñafiel-Verdú C Vilafranca M Ramírez G Méndez-Gallego M Buendía AJ Sánchez J 《Veterinary pathology》2011,48(6):1204-1211
A direct relationship has been firmly established between cyclooxygenase-2 (COX-2) expression and malignant behavior in human melanoma. This report examines the relationship between COX-2 expression and tumor location, mitotic and proliferative indices, degree of T CD3(+) lymphocyte infiltration, overall survival, and frequency of recurrence and metastasis of 57 melanocytic tumors (25 oral and 32 cutaneous). COX-2 was highly or moderately expressed in 88% of oral neoplasms (22 of 25), whereas for their cutaneous counterparts, COX-2 expression was low or insignificant in 75% of cases (24 of 32). High and moderate COX-2 expression levels were observed in 73% of melanocytic tumors with a mitotic index ≥ 3 per 10 high-power fields (26 of 36), whereas in 81% of tumors with a mitotic index < 3 (17 of 21), expression was mild or absent. There were 41 cases with known clinical outcomes; of those showing high, moderate, and mild COX-2 expression, 83.3% (10 of 12), 37.5% (3 of 8), and 25% (2 of 8) died, respectively, whereas 100% of animals showing no COX-2 expression (13 of 13) were still alive at the last follow-up. COX-2 expression was statistically correlated with tumor location, mitotic and percentage Ki-67 proliferative indices, and overall survival, frequency of neoplastic recurrence and metastasis. Regression analysis also showed disease-specific predictive value for COX-2 expression for subjects with melanocytic neoplasms. Additionally, only high COX-2 expression showed significant differences in overall survival, in comparison with moderate, mild, or absent expression. These results suggest that high COX-2 expression may be considered a prognostic biomarker and potentially as a target for therapeutic and preventive strategies in canine melanocytic neoplasms. 相似文献
70.
Ribeiro VL dos Santos JC Martins JR Schripsema J Siqueira IR von Poser GL Apel MA 《Veterinary parasitology》2011,179(1-3):195-198
Calea serrata Less. (Asteraceae), an endemic species of south Brazil known as "quebra-tudo", is used in Afro-Brazilian religious rituals and in folk medicine for treating liver disorders. Phytochemical studies of the n-hexane extract of this plant demonstrated the presence of precocene II, a benzopyran derivative known for its insecticidal activity. The aim of this work was to isolate this benzopyran and determine the chemical composition of the essential oil of C. serrata and further to evaluate the acaricidal activity of the essential oil and precocene II against the larvae of Rhipicephalus (Boophilus) microplus. The LC(99.9) and LC(50) values obtained with the oil, which presents precocene II and sesquiterpenes, were 3.94 μL/mL and 0.28 μL/mL, respectively. For precocene II this values were 4.25mg/mL and 1.78 mg/mL, respectively. The results indicate a synergistic interaction between the components of the oil and precocene II. 相似文献