全文获取类型
收费全文 | 29664篇 |
免费 | 907篇 |
国内免费 | 6篇 |
专业分类
林业 | 4587篇 |
农学 | 1725篇 |
基础科学 | 223篇 |
5552篇 | |
综合类 | 1264篇 |
农作物 | 2596篇 |
水产渔业 | 3078篇 |
畜牧兽医 | 7184篇 |
园艺 | 1300篇 |
植物保护 | 3068篇 |
出版年
2023年 | 103篇 |
2022年 | 160篇 |
2021年 | 315篇 |
2020年 | 302篇 |
2019年 | 274篇 |
2018年 | 3165篇 |
2017年 | 3092篇 |
2016年 | 1694篇 |
2015年 | 498篇 |
2014年 | 576篇 |
2013年 | 796篇 |
2012年 | 1653篇 |
2011年 | 2901篇 |
2010年 | 2493篇 |
2009年 | 1685篇 |
2008年 | 1991篇 |
2007年 | 2231篇 |
2006年 | 612篇 |
2005年 | 703篇 |
2004年 | 602篇 |
2003年 | 600篇 |
2002年 | 472篇 |
2001年 | 324篇 |
2000年 | 353篇 |
1999年 | 259篇 |
1998年 | 80篇 |
1996年 | 62篇 |
1995年 | 55篇 |
1993年 | 53篇 |
1992年 | 153篇 |
1991年 | 125篇 |
1990年 | 126篇 |
1989年 | 145篇 |
1988年 | 136篇 |
1987年 | 136篇 |
1986年 | 119篇 |
1985年 | 113篇 |
1984年 | 89篇 |
1983年 | 82篇 |
1982年 | 52篇 |
1981年 | 61篇 |
1980年 | 55篇 |
1979年 | 106篇 |
1978年 | 94篇 |
1977年 | 88篇 |
1976年 | 56篇 |
1974年 | 101篇 |
1973年 | 73篇 |
1972年 | 96篇 |
1971年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 5 毫秒
91.
Forzán MJ McClure JT 《The Canadian veterinary journal. La revue veterinaire canadienne》2005,46(4):342-344
Necropsy of a 3-day-old Holstein heifer revealed proximal megacolon and distal colorectal hypoplasia. Histologically, the hypoplastic distal colon and rectum lacked submucosal and myenteric ganglia. Clinical history, physical examination, and pathologic findings were consistent with intestinal aganglionosis, a congenital anomaly well documented in humans and foals but not previously reported in cattle. 相似文献
92.
Canine babesiosis in Hungary has always been a severe and frequent disease, attributed to infection with Babesia canis transmitted by Dermacentor reticulatus. Identification of the disease agent has been based merely on size and morphology of the intraerythrocytic parasites and no evidence has been found concerning the subspecies (genotype) of B. canis. Therefore, a molecular survey on natural Babesia infection of dogs in Hungary using PCR and sequence analysis was attempted to clarify the subspecies (genotype) and to obtain information on the occurrence of B. canis. A total of 44 blood samples from dogs showing clinical signs of babesiosis were collected. A piroplasm-specific PCR amplifying the partial 18S rRNA gene yielded an approximately 450 bp PCR product in 39 (88.6%) samples. Thirteen positive samples originated from Budapest and 26 from 21 other locations. Five PCR products were chosen randomly for sequencing. The partial 18S rDNA sequences were submitted to GenBank (accession numbers AY611729; AY611730; AY611731; AY611732 and AY611733). The sequences showed 100% homology to one another or differed by one nucleotide. BLAST search against GenBank revealed the highest similarity (99.8 or 100%) with Babesia canis canis. The implication of these data, for the further study and diagnosis of canine babesiosis is discussed. 相似文献
93.
Larsen RS Nutter FB Augspurger T Rocke TE Tomlinson L Thomas NJ Stoskopf MK 《Journal of the American Veterinary Medical Association》2002,221(1):80-85
OBJECTIVE: To characterize clinical features of avian vacuolar myelinopathy (AVM) in American coots. DESIGN: Case-control study. ANIMALS: 26 AVM-affected American coots and 12 unaffected coots. PROCEDURES: Complete physical, neurologic, hematologic, and plasma biochemical evaluations were performed. Affected coots received supportive care. All coots died or were euthanatized, and AVM status was confirmed via histopathologic findings. RESULTS: 3 severely affected coots were euthanatized immediately after examination. Seventeen affected coots were found dead within 7 days of admission, but 5 affected coots survived > 21 days and had signs of clinical recovery. Abnormal physical examination findings appeared to be related to general debilitation. Ataxia (88%), decreased withdrawal reflexes (88%), proprioceptive deficits (81%), decreased vent responses (69%), beak or tongue weakness (42%), and head tremors (31%), as well as absent pupillary light responses (46%), anisocoria (15%), apparent blindness (4%), nystagmus (4%), and strabismus (4%) were detected. Few gross abnormalities were detected at necropsy, but histologically, all AVM-affected coots had severe vacuolation of white matter of the brain. None of the control coots had vacuolation. CONCLUSIONS AND CLINICAL RELEVANCE: Although there was considerable variability in form and severity of clinical neurologic abnormalities, clinical signs common in AVM-affected birds were identified. Clinical recovery of some AVM-affected coots can occur when supportive care is administered. Until the etiology is identified, caution should be exercised when rehabilitating and releasing coots thought to be affected by AVM. 相似文献
94.
Monde Mapekula Michael Chimonyo Cletos Mapiye Kennedy Dzama 《Tropical animal health and production》2010,42(7):1413-1419
Understanding the utilisation patterns of milk assists in designing appropriate dairy development schemes in rural communities.
The objective of the study was to determine milk utilisation patterns in different smallholder farming systems in the Eastern
Cape Province of South Africa. Data were collected through the administration of recording sheets to 130 randomly selected
households in Alice, Fort Beaufort and Queenstown districts. Amounts of milk produced per household ranged from 9 to 21 l
per household per day. Milk consumption/household/day was similar among the three districts. Milk consumption in the early
lactation doubled the amount consumed in late lactation (P < 0.05). Milk in the communal areas was largely utilised as fresh or sour milk. Fresh milk was mostly used in tea/coffee
or to make porridge for children. Sour milk was consumed with thick boiled maize meal. Fort Beaufort (10.2 ± 1.37 l/day) had
the highest sour milk sales whilst Queenstown had the highest fresh milk sales (9.7 ± 5.57 l/day). It was concluded that quantities
of milk consumed or sold as fresh or sour were generally low and varied across smallholder farming systems. 相似文献
95.
Jemberu Dessie Solomon Melaku Firew Tegegne Kurt J. Peters 《Tropical animal health and production》2010,42(5):841-848
The experiment consisting of 7 days of digestibility and 90 days of feeding trial was conducted at Wogda (Ethiopia) to determine
the effect of supplementation of graded levels of concentrate mix (CM) on feed intake, digestibility, and body weight (BW)
change in hay-based feeding of Simada sheep. Twenty-yearling Simada sheep with a mean initial BW of 17.9 ± 0.81 kg (mean ±
SD) were used in randomized complete block design arranged into five blocks of four animals. The four dietary treatments that
consisted of hay alone (T1), hay +150 g dry matter (DM; T2, low), hay +250 g DM (T3, medium), and hay +350 g DM (T4, high)
CM were randomly assigned to each sheep within a block. The CM consisted of wheat bran (WB), noug seed (Guizotia abyssinica) meal and safflower (Carthamus tinctorius) seed meal at the ratio of (2:1:1), respectively. Supplementation with T2 and T3 increased (P < 0.001) total DM and organic matter intake than the control treatment. Overall, supplementation improved (P < 0.001) crude protein intake, digestibility, feed conversion efficiency, BW gain, and profitability compared to the control,
whereas sheep on the high than the low and medium level of supplementation performed better in these parameters among the
supplemented treatments. From the results of this study, T4 is recommended as the best level of supplementation since it resulted
in better nutrient utilization, animal performance, and profitability. 相似文献
96.
Kagira JM Kanyari PN Githigia SM Maingi N Ng'ang'a JC Gachohi JM 《Tropical animal health and production》2012,44(3):657-664
Nematode infections are a serious constraint to pig production, especially where free range pig keeping is practiced. This
study investigated the epidemiology of nematodes in free range pigs in Busia District, Kenya. Three hundred and six pigs from
135 farms were sampled for faeces that were analysed for nematode eggs per gram (EPG) of faeces using the McMaster technique.
The nematode eggs were also identified to genus and species based on morphology. A questionnaire on risk factors was also
administered to the pig owners. The overall prevalence and mean nematode EPG were 84.2% and 2,355, respectively. The nematode
eggs were identified as those belonging to Oesophagostomum spp. (75%), Strongyloides ransomi (37%), Ascaris suum (18%), Metastrongylus spp. (11%), Trichuris suis (7%) and Physocephalus sexalatus (3%). The prevalence of nematodes was positively correlated (p < 0.05) with the amount of rainfall in the division of the pigs' origin (all nematodes except S. ransomi). The prevalence of nematodes was also associated with the age of the pigs. A lower burden of nematodes was associated (p < 0.05) with a history of deworming (A. suum) and the provision of night housing (S. ransomi and Metastrongylus spp.). In conclusion, this study has provided information on nematode infections and the associated risk factors for free
range pigs in Busia District, which can be used when implementing integrated control measures. 相似文献
97.
Geisbauer E Khol JL Wassertheurer M Damoser J Osterreicher E Dünser M Revilla-Fernández S Baumgartner W 《The Veterinary quarterly》2007,29(4):138-148
Paratuberculosis (Johne's disease), which is widely distributed throughout the world, is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Diagnosis of subclinically infected cattle is challenging and is especially problematic in herds with low prevalence of MAP. The aim of this long-term study was the comparison of different diagnostic tests for MAP and specific antibodies in a herd with low prevalence of MAP. Three different commercially available serum-ELISA (Svanovir-ELISA, Svanova, Uppsala, Sweden; IDEXX-ELISA, IDEXX Laboratories, Maine, USA; Pourquier-ELISA, Institut Pourquier, Montpellier, France) and two milk ELISA (Svanovirm-ELISA Svanova, Uppsala, Sweden; Pourquier-ELISA, Institut Pourquier, Montpellier, France) were compared. Apart from these indirect diagnostic tests, two methods for the detection of the etiologic agent (bacteriologic culture and real-time PCR of faecal samples) were performed. In January 2005 the first and in April 2005 the second herd investigation of all animals older than 2 years (n=335) were carried out. Blood, milk and faecal samples were taken. From November 2005 until April 2006 follow up investigations were performed. For this purpose, blood-, milk- and faecal samples were monthly taken from 63 selected animals. The highest number of blood- and milk samples with a detectable antibody-level was found by the Svanovir-ELISA. There was a significant correlation between serum- and milk- Svanovir-ELISA results, whereas the agreement between ELISA and faecal culture/PCR was low. Significant correlations between Svanovir-serum-ELISA results and milk somatic cell counts could be registered. Moreover, there was significant agreement between IDEXX-serum-ELISA results with the age and number of lactations of the cows, as well as the mother's MAP-status. 相似文献
98.
Genetic variation within and between G1 and G3 genotypes of Echinococcus granulosus in Italy revealed by multilocus DNA sequencing 总被引:1,自引:0,他引:1
Busi M Snábel V Varcasia A Garippa G Perrone V De Liberato C D'Amelio S 《Veterinary parasitology》2007,150(1-2):75-83
Numerous studies have provided evidence that Echinococcus granulosus exists as a complex of different strains, that differ in a wide variety of criteria that have an impact on the epidemiology, pathology and control of cystic hydatid disease (CHD) and, to date, 10 distinct genotypes (G1-G10) have been identified. In Italy, sequence analysis of the mitochondrial cox1 and nad1 genes showed the occurrence of the G1 genotype, the common sheep strain, the G3 genotype, the buffalo strain and of one isolate identified as G2 genotype, the Tasmanian sheep strain. In the present work, we have analysed E. granulosus strains in Italy, by genotyping a large sample of isolates and by checking out the genetic differentiation within and among the G1 and G3 genotypes using an additional mitochondrial gene as marker, the rrnS gene. Sequencing of the rrnS gene revealed a significant genetic differentiation between isolates identified as belonging to the G1 and G3 genotypes, with fixed nucleotide substitutions. This study provides further evidence of the occurrence of the E. granulosus G3 buffalo strain in Italy, a strain previously thought to be confined to the Indian region. 相似文献
99.
Evaluation of an antigen capture ELISA for the early diagnosis of Hypoderma lineatum in cattle under field conditions 总被引:1,自引:0,他引:1
Panadero R Vázquez L Colwell DD López C Dacal V Morrondo P Díez-Baños P 《Veterinary parasitology》2007,147(3-4):297-302
An antigen capture or sandwich ELISA (sELISA) was evaluated for the diagnosis of Hypoderma lineatum in cattle under field conditions in northwestern Spain. The kinetics of circulating hypodermin C (HyC) and specific antibodies during the course of natural infestation were determined in a group of 10 Frisian calves. In addition, oesophagi and blood samples were taken from 105 cows at a slaughterhouse in order to compare three methods for the diagnosis of H. lineatum: sandwich ELISA for the detection of the antigen HyC (sELISA), indirect ELISA for the detection of antibodies anti-HyC (iELISA) and the detection of first instars (L1) in the oesophagus. In naturally infested cattle, HyC was present in circulation at low levels during the early and late phases of the infestation. However, in the middle phase, coinciding with the presence of L1 in the oesophagus, two peaks of increased HyC concentration were observed. Specific antibodies increased progressively until the first appearance of larvae in warbles on the back. There was no correlation between antigen or antibody levels and the number of grubs in the back. Prevalence of first instars in the oesophagi of slaughtered cows was 21.9% (23/105). The percentage of cattle that were positive for circulating antigen was slightly higher (24.8%), suggesting the recent destruction of migrating larvae in some animals. However, there was no correlation between the number of L1 and HyC levels. With the iELISA, 79% of the animals were positive to Hypoderma, which means that a high percentage of those animals have been exposed to the parasite but they had no apparent current infestation. The sELISA is a good tool to follow larval development within the host; however, the episodic elevation of HyC levels limits the usefulness of this test for the early diagnosis of Hypoderma under field conditions. 相似文献
100.