全文获取类型
收费全文 | 4545篇 |
免费 | 310篇 |
国内免费 | 2篇 |
专业分类
林业 | 304篇 |
农学 | 128篇 |
基础科学 | 36篇 |
824篇 | |
综合类 | 851篇 |
农作物 | 195篇 |
水产渔业 | 233篇 |
畜牧兽医 | 1842篇 |
园艺 | 109篇 |
植物保护 | 335篇 |
出版年
2023年 | 31篇 |
2022年 | 34篇 |
2021年 | 67篇 |
2020年 | 77篇 |
2019年 | 82篇 |
2018年 | 96篇 |
2017年 | 89篇 |
2016年 | 110篇 |
2015年 | 79篇 |
2014年 | 120篇 |
2013年 | 202篇 |
2012年 | 229篇 |
2011年 | 284篇 |
2010年 | 178篇 |
2009年 | 149篇 |
2008年 | 254篇 |
2007年 | 244篇 |
2006年 | 259篇 |
2005年 | 239篇 |
2004年 | 189篇 |
2003年 | 221篇 |
2002年 | 182篇 |
2001年 | 72篇 |
2000年 | 81篇 |
1999年 | 86篇 |
1998年 | 45篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 32篇 |
1992年 | 39篇 |
1991年 | 54篇 |
1990年 | 49篇 |
1989年 | 47篇 |
1988年 | 33篇 |
1987年 | 60篇 |
1986年 | 40篇 |
1985年 | 58篇 |
1984年 | 38篇 |
1983年 | 46篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1978年 | 25篇 |
1976年 | 26篇 |
1973年 | 27篇 |
1970年 | 24篇 |
1969年 | 31篇 |
排序方式: 共有4857条查询结果,搜索用时 15 毫秒
41.
Fulmer R Loeb WF Martin DP Gard EA 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1984,13(1):19-25
The intravenous administration of 0.75 gm glucose per kg and the measurement of serum glucose pretest and at 10, 20, 30, 60, 90 and 120 minutes constitute a satisfactory protocol for intravenous glucose tolerance testing of Rhesus (Macaca mulatto) and African Green (Cercopithecus aethiops) monkeys. No significant differences were noted between animals restrained with ketamine hydrochloride and those restrained with sodium pentobarbital, but the African Green males and females and the male Rhesus monkeys yielded significantly different results while being manually restrained. 相似文献
42.
Mastitis Caused by Haemophilus somnus in a Dairy Cow 总被引:1,自引:1,他引:1
43.
Fenske M 《American journal of veterinary research》2007,68(3):225; author reply 225
44.
Kook PH Boretti FS Hersberger M Glaus TM Reusch CE 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(3):388-393
BACKGROUND: Measurement of high concentrations of urine catecholamines and metanephrines is useful in diagnosing pheochromocytoma in humans. Stress increases catecholamine excretion in urine. HYPOTHESIS: Stress of a hospital visit increases urinary catecholamine and metanephrine excretion in dogs. ANIMALS: Fourteen clinically normal dogs, 2 dogs with pheochromocytoma. METHODS: Voided urine samples were collected by the owners 7 days before (t-7), during the hospital visit immediately after diagnostic procedures (t0), as well as 1 (t1) and 7 days (t7) after the hospital visit. Urine catecholamine and metanephrine concentrations were measured using high-pressure liquid chromatography and expressed as ratios to urine creatinine concentration. RESULTS: In client-owned dogs epinephrine and norepinephrine ratios at t0 were significantly higher compared with ratios at t7. Metanephrine and normetanephrine ratios at t-7, t0, and t1 did not differ significantly from each other; however, at t7 they were significantly lower compared to values at t-7. In staff-owned dogs no significant differences were detected among the different collecting time points for any variable. Metanephrine and normetanephrine ratios were significantly higher in client-owned dogs compared to staff-owned dogs at t-7, t0, and t1 but not at t7. CONCLUSIONS AND CLINICAL IMPORTANCE: Stress associated with a hospital visit and with the sampling procedure causes increases in urine catecholamine and metanephrine excretion. Urine collection for the diagnosis of pheochromocytoma probably should take place at home after adaptation to the sampling procedure. 相似文献
45.
Martin PA Cameron AR Barfod K Sergeant ES Greiner M 《Preventive veterinary medicine》2007,79(2-4):98-115
A method for quantitative evaluation of surveillance for disease freedom has been presented in the accompanying paper (Martin et al., 2007). This paper presents an application of the methods, using as an example surveillance for classical swine fever (CSF) in Denmark in 2005. A scenario tree model is presented for the abattoir-based serology component of the Danish CSF surveillance system, in which blood samples are collected in an ad hoc abattoir sampling process, from adult pigs originating in breeding herds in Denmark. The model incorporates effects of targeting (differential risk of seropositivity) associated with age and location (county), and disease clustering within herds. A surveillance time period of one month was used in the analysis. Records for the year 2005 were analysed, representing 25,332 samples from 3528 herds; all were negative for CSF-specific antibodies. Design prevalences of 0.1-1% of herds and 5% of animals within an infected herd were used. The estimated mean surveillance system component (SSC) sensitivities (probability that the SSC would give a positive outcome given the animals processed and that the country is infected at the design prevalences) per month were 0.18, 0.63 and 0.86, for among-herd design prevalences of 0.001, 0.005 and 0.01. The probabilities that the population was free from CSF at each of these design prevalences, after a year of accumulated negative surveillance data, were 0.91, 1.00 and 1.00. Targeting adults and herds from South Jutland was estimated to give approximately 1.9, 1.6 and 1.4 times the surveillance sensitivity of a proportionally representative sampling program for these three among-herd design prevalences. 相似文献
46.
The aim of the study was to evaluate the diagnostic quality of the real-time RT-PCR assay described by Hoffmann et al. [Hoffmann, B., Beer, M., Schelp, C., Schirrmeier, H., Depner, K., 2005. Validation of a real-time RT-PCR assay for sensitive and specific detection of classical swine fever. J. Virol. Methods 130, 36-44] for the routine intra vitam diagnosis of classical swine fever (CSF). We compared the assay with conventional diagnostic methods by using defined diagnostic material from an animal experiment with pigs showing different clinical forms of CSF. Compared to virus isolation and antigen ELISA an enhanced sensitivity of the real-time RT-PCR could be shown. We were able to detect all infected pigs regardless of the clinical course of CSF. CSF infection was detected already during the incubation period, during the entire clinical phase as well as at the beginning of convalescence when the first antibodies were detected and no virus could be isolated any more. In most cases, positive PCR results were obtained 2 days earlier than with virus isolation and 2-4 days earlier than with the antigen ELISA. 相似文献
47.
Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely 总被引:3,自引:0,他引:3
Twenty Polypay-sired ewes (Group P) and 14 Suffolk ewes (Group S) were bled at 48-h intervals for 10 d beginning on April 6, 1989, and the serum was assayed for progesterone to determine which ewes were anestrous; 9/20 Group P ewes were anestrous, compared with 14/14 Group S ewes (P less than .001). Catheters were placed into the jugular vein of anestrous ewes from both breed groups (eight of Group P, seven of Group S), and samples of serum were collected at 12-min intervals for 4 h. Then, the ewes were exposed to mature, intact rams, and additional samples were taken at 12-min intervals for 4 h after ram exposure. The serum was later analyzed to determine the secretion of LH in response to ram introduction. After the acute bleeding period, all Group P and Group S ewes were commingled and exposed to a ram continuously for 42 d. Samples of serum were collected thrice weekly and analyzed for progesterone to monitor ovulatory response to ram introduction through the 42-d period. In addition, breeding activity and lambing data were recorded. When all Group P ewes were compared to Group S ewes, a greater proportion (P less than .001) of Group P ewes were mated (20/20 vs 3/13; one Group S ewe died during the 42-d mating period) by the end of the 42-d period and more (P less than .001) ewes lambed in the fall (17/20 Group P vs 2/13 Group S).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
48.
R S Shoemaker G S Martin D J Hillmann P F Haynes J R McClure H L Schneiter 《Journal of the American Veterinary Medical Association》1991,198(1):120-122
Two horses became acutely lame following a fall during strenuous exercise and were diagnosed as having disruption of the caudal component of the reciprocal apparatus. Clinical signs consisted of lameness of the right pelvic limb, characterized by flexion of the hock and simultaneous extension of the stifle. Radiography revealed an avulsion fracture from the supracondylar tuberosity and fossa of the distal portion of the femur in one horse. Clinical and radiographic findings indicated avulsion of the lateral origin of the gastrocnemius and superficial digital flexor muscles. Treatment consisted of stall rest, limb immobilization, and phenylbutazone administration. One horse recovered to soundness and the other deteriorated and was euthanatized. 相似文献
49.
Martin Bonamy Sabrina Kluska Elisa Peripolli Marcos Vinícius Antunes de Lemos Sabrina Thaise Amorim Roberto Jose Vaca Raysildo Barbosa Lbo Letícia Mendes de Castro Carina Ubirajara de Faria Fabio Borba Ferrari Fernando Baldi 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2019,136(1):15-22
The aim of this study was to estimate genetic parameters for different precocious calving criteria and their relationship with reproductive, growth, carcass and feed efficiency in Nellore cattle using the single‐step genomic BLUP. The reproductive traits used were probability of precocious calving (PPC) at 24 (PPC24), 26 (PPC26), 28 (PPC28) and 30 (PPC30) months of age, stayability (STAY) and scrotal circumference at 455 days of age (SC455). Growth traits such as weights at 240 (W240) and 455 (W455) days of age and adult weight (AW) were used. Rib eye area (REA), subcutaneous fat thickness (SFT), rump fat thickness (RFT) and residual feed intake (RFI) were included in the analyses. The estimation of genetic parameters was performed using a bi‐trait threshold model including genomic information in a single‐step approach. Heritability for PPC traits was moderate to high (0.29–0.56) with highest estimates for PPC24 (0.56) and PPC26 (0.50). Genetic correlation estimates between PPC and STAY weakened as a function of calving age. Correlation with SC455, growth and carcass traits were low (0.25–0.31; ?0.22 to 0.04; ?0.09 to 0.18, respectively), the same occurs with RFI (?0.09 to 0.08), this suggests independence between female sexual precocity and feed efficiency traits. The results of this study encourage the use of PPC traits in Nellore cattle because the selection for such trait would not have a negative impact on reproductive, growth, carcass and feed efficiency indicator traits. Stayability for sexual precocious heifers (PPC24 and PPC26) must be redefined to avoid incorrectly phenotype assignment. 相似文献
50.