全文获取类型
收费全文 | 159028篇 |
免费 | 8374篇 |
国内免费 | 79篇 |
专业分类
林业 | 6808篇 |
农学 | 4887篇 |
基础科学 | 1099篇 |
18332篇 | |
综合类 | 29629篇 |
农作物 | 6293篇 |
水产渔业 | 7250篇 |
畜牧兽医 | 81419篇 |
园艺 | 1882篇 |
植物保护 | 9882篇 |
出版年
2018年 | 1919篇 |
2017年 | 2126篇 |
2016年 | 2031篇 |
2015年 | 1721篇 |
2014年 | 2063篇 |
2013年 | 5981篇 |
2012年 | 3976篇 |
2011年 | 4814篇 |
2010年 | 3229篇 |
2009年 | 3203篇 |
2008年 | 4904篇 |
2007年 | 4551篇 |
2006年 | 4310篇 |
2005年 | 4081篇 |
2004年 | 4082篇 |
2003年 | 4153篇 |
2002年 | 3904篇 |
2001年 | 4796篇 |
2000年 | 4746篇 |
1999年 | 3642篇 |
1998年 | 1559篇 |
1997年 | 1643篇 |
1995年 | 1869篇 |
1994年 | 1685篇 |
1993年 | 1635篇 |
1992年 | 3359篇 |
1991年 | 3619篇 |
1990年 | 3552篇 |
1989年 | 3606篇 |
1988年 | 3326篇 |
1987年 | 3314篇 |
1986年 | 3531篇 |
1985年 | 3383篇 |
1984年 | 2785篇 |
1983年 | 2511篇 |
1982年 | 1706篇 |
1981年 | 1561篇 |
1979年 | 2576篇 |
1978年 | 2077篇 |
1977年 | 1757篇 |
1976年 | 1714篇 |
1975年 | 1784篇 |
1974年 | 2252篇 |
1973年 | 2365篇 |
1972年 | 2312篇 |
1971年 | 2203篇 |
1970年 | 2074篇 |
1969年 | 1966篇 |
1968年 | 1610篇 |
1967年 | 1734篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
Luis A. Saavedra-Jiménez Rodolfo Ramírez-Valverde Rafael Núñez-Domínguez José G. García-Muñiz Nicolas Lopez-Villalobos Agustín Ruíz-Flores 《Tropical animal health and production》2013,45(7):1489-1494
The objective of this study was to determine the magnitude of genotype by climate interaction (GCI) in the national genetic evaluation for weaning (WW) and yearling (YW) weights of Mexican Braunvieh cattle. The numbers of performance records and animals in the pedigree were 12,364 and 25,173 for WW, and 7,991 and 18,072 for YW, respectively. Performance records were clustered based on climatological variables into: dry tropic (DT), wet tropic (WT), and temperate (TE) climates. Animal models were used to estimate genetic parameters and predict breeding values in each of the climates. Bivariate analyses were carried out for pairwise combinations of climates on each trait, considering the same trait in different climates as a different trait. Criteria to evaluate GCI were genetic correlations (r g), correlations between predicted breeding values (r BV), and frequencies of coincidence (FC) in the ranking of the top 25 sires. Results of comparisons between pairs of climates were variable, depending on specific cases. For WW, the r g, r BV, and FC ranged from ?0.36 to 0.84, ?0.60 to 0.97, and 0.16 to 0.92, respectively; whereas for YW, they fluctuated between 0.23 and 0.99, 0.33 and 1.00, and 0.60 and 1.00, respectively. For both traits, the results suggest absence of GCI between DT and TE; however, GCI was detected in the other pairs of climates, where WT was involved. To maximize genetic progress, the joint genetic evaluation should be performed only for animals with performance data in DT and TE, whereas a separated evaluation is suggested for animals with performance records generated under WT conditions. 相似文献
972.
Relationship between the serum concentrations of serotonin and lipids and aggression in dogs 总被引:1,自引:0,他引:1
The serum concentrations of serotonin and lipids--triglycerides, total cholesterol, low density lipoprotein, high density lipoprotein and very low density lipoprotein--were determined in 18 normal dogs and 23 dogs diagnosed as aggressive on the basis of interviews with their owners and an assessment of their behaviour with reference to a canine overt aggression chart. The serum serotonin levels in the aggressive dogs were significantly lower than in the normal dogs (P<0.01), but the differences in serum lipids between the two groups were not statistically significant. 相似文献
973.
Effect of previous locoweed (Astragalus and Oxytropis species) intoxication on conditioned taste aversions in horses and sheep 总被引:1,自引:0,他引:1
Locoweed species (Astragalus and Oxytropis spp.) are a serious toxic plant problem for grazing livestock. Horses and sheep have been conditioned to avoid eating locoweed using the aversive agent LiCl. The objective of this study was to determine if previous locoweed intoxication affects food aversion learning in horses and sheep. Horses and sheep were divided into 3 treatment groups: control (not fed locoweed and not averted to a novel feed); locoweed-novel feed averted (fed locoweed and averted to a novel feed); and averted (not fed locoweed and averted to a novel feed). Animals in the locoweed-novel feed averted groups were fed locoweed during 2 periods of 21 and 14 d, respectively, with each feeding period followed by a 14-d recovery period. Animals were averted to a novel test feed at the end of the first locoweed-feeding period, and periodically evaluated for the strength and persistence of the aversion. During the first recovery period, locoweed-novel feed averted horses ate less (9.5% of amount offered) of the test feed than did control horses (99.8%) and did not generally differ from averted horses (0%). During recovery period 2, locoweed-novel feed averted horses (4.3%) differed (P = 0.001) in consumption (% of offered) of the test feed from controls (100%) and the averted group (0%). Locoweed-novel feed averted sheep differed (P = 0.001) from controls (14.4 vs. 99.5%, respectively, during recovery period 1), whereas locoweed-novel feed averted sheep did not differ (P > 0.50) from averted sheep (0.6%). During the second recovery period, control sheep (100%) differed (P < 0.05) from averted (0%) and locoweed-novel feed averted (12.2%) groups. Two intoxicated sheep (locoweed-novel feed averted) partially extinguished the aversion during the first recovery period, but an additional dose of LiCl restored the aversion. Two of 3 intoxicated horses had strong aversions that persisted without extinction; 1 horse in the locoweed-novel feed averted group had a weaker aversion. These findings suggest that horses and sheep previously intoxicated by locoweeds can form strong and persistent aversions to a novel feed, but in some animals, those aversions may not be as strong as in animals that were never intoxicated. 相似文献
974.
975.
Galuppi R. Avenoso A.M. Leotti G. Ostanello F. Poglayen G. Tampieri M. P. 《Veterinary research communications》2007,31(1):233-236
Veterinary Research Communications - Galuppi, R., Avenoso, A.M., Leotti, G., Ostanello, F., Poglayen, G. and Tampieri, M.P., 2007. Diagnosis of sarcoptic mange in slaughtered swine. Veterinary... 相似文献
976.
Lobetti RG 《Journal of the South African Veterinary Association》2007,78(3):175-177
A 9-year-old male cat was presented for evaluation of chronic weight loss and was subsequently diagnosed with pericardial effusion. The effusion was quantified as a septic exudate caused by the anaerobic bacterium Peptostreptococcus. Antibiotic therapy resulted in complete resolution of the pericardial effusion. As Peptostreptococcus is a common oral bacterium and the cat had a previous dental procedure, it is speculated that the pericardial effusion was secondary to bacteraemia from the dental procedure. 相似文献
977.
OBJECTIVE: To compare procedure time, complications, mortality, and short-term outcome in dogs with patent ductus arteriosus (PDA) treated by surgical ligation (SL) or transarterial coil occlusion (TCO). STUDY DESIGN: Retrospective study. ANIMALS: Dogs with PDA (n=204). METHODS: Medical records of dogs treated for PDA were reviewed. Dogs treated by SL when it was the primary method used for PDA treatment (1993-1998) were compared with dogs treated by TCO when it was the primary method used for PDA treatment (1999-2003). Dogs treated during the transition between techniques, dogs treated with SL (1999-2003) and dogs treated with TCO before 1999, as well as dogs with pulmonary hypertension, or bidirectional or reversed (right-to-left) flow through the PDA were excluded from analysis. RESULTS: Age, weight, gender distribution, and procedure times (P=.43) were similar for both groups. Major complications were more common with SL (12% versus 4.3%; P=.035) whereas minor complications were more common with TCO (12% versus 26%; P=.015). Initial success rate was higher for SL (94%) compared with TCO (84%; P=.027). There was no significant difference in mortality between SL (5.6%) and TCO (2.6%; P=.27). CONCLUSIONS: Both SL and TCO are acceptable PDA treatments with comparable mortality; however, SL was associated with a higher risk of major complications and TCO was associated with a lower initial success rate. 相似文献
978.
Beth A Valentine Wilson K Rumbeiha Terry S Hensley Richard R Halse 《Journal of veterinary diagnostic investigation》2007,19(2):212-215
Over a 12-day period, 13 animals in a herd of 110 beef cattle developed ataxia with profound muscle fasciculations progressing to recumbency. Twelve animals (5 adults and 7 calves from 8-10 months of age) died, and 1 cow was euthanized. Hemorrhagic diarrhea occurred in some, but not all, animals. The onset of clinical signs was at least 12 hours after the cattle had gained access to contents of old buildings used for storage, and the majority of deaths occurred within 24 to 48 hours after the onset of clinical signs. Approximately 9 kg of unidentified pellets were found strewn in the barn area where the cattle had been. Autolysis considered more severe than expected for the postmortem interval, suggestive of high body temperature before death, and congestion of body tissues were the only significant findings detected in the cow that was euthanized and submitted for necropsy examination. The clinical history and lack of postmortem lesions were most consistent with toxicity. A toxic level of arsenic (6.18 ppm) was detected in the kidney, and metaldehyde was detected in the liver. The pellets were analyzed and found to contain both arsenic and metaldehyde, consistent with a discontinued molluscicidal product. 相似文献
979.
Synovial hemangioma was diagnosed in an 8-year-old castrated male Belgian Sheepdog with lameness of 3 months' duration. Pain, soft-tissue swelling, and hemarthrosis were localized to the left stifle joint. Projections of synovial membrane with reddish-purple nodules, excised via arthrotomy, were composed histologically of variably sized vascular channels that were lined by well-differentiated endothelial cells and separated by fibrous septa. Distension of some channels resulted in endothelial disruption, thrombosis, hemorrhage, necrosis, and focal spindle-cell proliferation. The limb was amputated to remove remaining neoplastic tissue. The hemangioma extended focally into the joint capsule and popliteal soft tissue but did not invade skeletal muscle or bone. The dog was free of detectable neoplasia 6 months after amputation. Synovial hemangioma is a rare benign vascular proliferation in people, most commonly in the knee, and should be included in the differential diagnosis for canine synovial tumors. 相似文献
980.
J C Lewis A J Fitzgerald F M Gulland C M Hawkey P Kertesz J K Kirkwood R A Kock 《The British veterinary journal》1989,145(4):394-396
Clinical experience of 73 cases of necrobacillosis in red-necked wallabies (Macropus rufogriseus) over a 6-year period is reviewed. Diagnostic methods and the medical and surgical treatment options are detailed. It is suggested that survival curves are necessary to assess the outcome of treatment. 相似文献