全文获取类型
收费全文 | 659篇 |
免费 | 69篇 |
专业分类
林业 | 27篇 |
农学 | 9篇 |
基础科学 | 4篇 |
62篇 | |
综合类 | 83篇 |
农作物 | 21篇 |
水产渔业 | 22篇 |
畜牧兽医 | 482篇 |
园艺 | 9篇 |
植物保护 | 9篇 |
出版年
2023年 | 13篇 |
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 40篇 |
2019年 | 33篇 |
2018年 | 30篇 |
2017年 | 23篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 24篇 |
2013年 | 29篇 |
2012年 | 37篇 |
2011年 | 43篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 38篇 |
2007年 | 29篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1978年 | 2篇 |
1974年 | 3篇 |
1970年 | 2篇 |
1928年 | 3篇 |
1925年 | 2篇 |
1900年 | 1篇 |
1899年 | 1篇 |
1898年 | 1篇 |
1897年 | 1篇 |
1896年 | 1篇 |
排序方式: 共有728条查询结果,搜索用时 15 毫秒
71.
To assess the diagnostic accuracy of survey radiography for canine thoracolumbar intervertebral disc protrusion, survey radiographs (lateral and ventrodorsal) of 64 dogs with surgically-confirmed thoracolumbar intervertebral disc protrusion, 51 dogs with negative myelograms and 29 dogs with various spinal conditions other than disc protrusion were reviewed by three independent observers who were unaware of any clinical information. There were marked differences in observer performance for diagnosis of intervertebral disc protrusion, although there were no significant differences in intraobserver diagnostic accuracy for small vs. large dogs. Accuracy of observers for determining sites of intervertebral disc protrusion using survey radiography was in the range 51-61%. All observers had low accuracy for identification of second sites of intervertebral disc protrusion. The most useful radiographic sign, narrowed intervertebral space, had only moderate sensitivity (range 64-69%) and moderate predictive value (range 63-71%) for intervertebral disc protrusion. Vacuum phenomenon was an infrequent but accurate sign of intervertebral disc protrusion. Recognition of multiple radiographic signs of intervertebral disc protrusion at one site was associated with increased accuracy of diagnosis. No observer was accurate enough to justify attempting targeted surgical treatment of intervertebral disc protrusion without myelography. 相似文献
72.
Jonathan L. Stowater DVM MS Christopher R. Lamb MA VETMB 《Veterinary radiology & ultrasound》1989,30(5):232-239
The ultrasonographic features of paraprostatic cysts in nine dogs are described along with historical, clinical, surgical and pathologic findings. Cysts occurred predominantly in older, large breed dogs (mean age 8 years, range 3–11 years). The most common presenting complaints were depression, inappetance, stranguria, tenesmus and bloody penile discharge. A palpable abdominal mass was the most common physical finding. Ultrasonographically, paraprostatic cysts were usually large anechoic structures; many contained internal septa. Moderately large anechoic cavities or cysts were also detected in the prostatic parenchyma of five dogs, and in two of these communication with the paraprostatic cyst was visualized. There were no clearly distinct ultrasonographic criteria to discriminate septic from nonseptic paraprostatic cysts. 相似文献
73.
74.
Lawrence J. Kleine DVM MS Christopher R. Lamb MA ETMB MRCVS 《Veterinary radiology & ultrasound》1989,30(3):133-141
Diagnostic radiology of the esophagus, stomach, small and large intestine, mesentery, and pancreas is reviewed. Survey and contrast radiography remain the principal imaging methods used to evaluate gastrointestinal diseases in animals. Of the other imaging techniques, scintigraphy has potential in assessment of esophageal and gastric motility disorders, and detection of intestinal hemorrhage. Ultrasonography is useful for imaging the pancreas and gastrointestinal mass lesions. 相似文献
75.
C. R. Lamb M. A. Forster-van Hijfte R. N. White F. J. McEvoy H. C. Rutgers 《The Journal of small animal practice》1996,37(5):205-209
Twenty-four cats with clinical and, or, clinico-pathological signs compatible with portosystemic shunting were examined prospectively using two-dimensional grey-scale, duplex and colourflow Doppler ultrasonography. Diagnosis of congenital portosystemic shunt was subsequently confirmed in 14 cats using operative mesenteric portography and surgery. Of the 14 affected cats, nine were purebred; eight were male and six female. The mean age at the time of diagnosis was nine months (range four to 27 months). Ultrasonographic evidence of a small liver was present in seven cats (50 per cent); visibility of intrahepatic portal vessels was reduced in three (21 per cent). An anomalous blood vessel was identified ultrasonographically in each cat; in 10 cats (71 per cent) the vessel was observed to originate from the portal vein and drain into the caudal vena cava. Abnormally variable portal blood flow waspresent in eight of the 10 cats in which it was measured. At surgery, six shunts were intrahepatic and eight extrahepatic; the ultrasonographic diagnosis of intra- versus extra-hepatic shunt was correct in 13 cats (93 per cent). No anomalous blood vessels or abnormalities affecting the portal vein were detected ultrasonographically in any of the 10 cats that did not have congenital portosystemic shunting. Hence, the accuracy of ultrasonography for diagnosis of congenital portosystemic shunting in this series was 100 per cent. 相似文献
76.
77.
78.
Angus (A), Charolais (C), Hereford (H), Limousin (L), and Simmental (S) breeds were included in deterministic computer models simulating integrated cow-calf-feedlot production systems. Three mating systems were used: pure-breeding and two-and three-breed rotational crossbreeding. Breed information was taken from the literature. Herd sizes were unrestricted; however, 100 heifers were saved as replacements. Cows were removed for reproductive failure, age (greater than 10.5 yr), or death. Calves produced in the cow-calf segment were fed in a custom feedlot to four slaughter end points: 440 d, 457 d, 288-kg carcass weight, and low Choice. All animals were fed to requirements. Cull cows were slaughtered after weaning. Biological and economic efficiencies improved with crossbreeding; however, rankings of breed combinations depended on how efficiencies were measured (weight, lean, or value basis). Among purebreds, reproductive performance had a large influence on breed rankings at age and weight end points, whereas feedlot performance was important at the low Choice end point. Crossbred combinations involving British (A or H) and Continental (C or S) breeds were more efficient than other crossbred combinations at all end points. However, choosing specific breed combinations for integrated systems depends on slaughter end points, market end points (weight vs lean), and measures of efficiency (weight, lean, or value basis). 相似文献
79.
THE FIRST TWENTY-ONE YEARS OF VETERINARY DIAGNOSTIC ULTRASOUND 总被引:2,自引:0,他引:2
Christopher R. Lamb MA VETMB MRCVS Jon L. Stowater DVM MS Frank S. Pipers DVM PhD 《Veterinary radiology & ultrasound》1988,29(1):37-45
The veterinary literature of 1966–1986 was searched for articles and books related to the use of diagnostic ultrasound in animals. There were 492 references, categorized as follows: general, 30; small animal applications, 169; large animal applications, 248; blood pressure measurement, 23; ultrasound-guided biopsy, 4; miscellaneous, 18. 相似文献
80.
OBJECTIVE: To determine the prevalence of asymptomatic idiopathic macrothrombocytopenia in the population of Cavalier King Charles Spaniels (CKCS) in New South Wales (NSW) and to determine if it exhibits an autosomal recessive inheritance pattern. We also aimed to determine if significant differences existed when counting platelets manually, by auto analyser or by blood smear estimation in CKCS and mixed breed dogs. METHODS: Blood was collected from 172 dogs (152 CKCS and 20 mixed breed) and placed into sodium-citrate anticoagulant. Platelet counts were performed manually, by auto analyser and by blood smear estimates in CKCS and mixed breed dogs. Blood smears were also examined for platelet clumping and erythrocyte, leukocyte and platelet morphology. Pedigree analysis was performed to determine if an autosomal recessive inheritance pattern was supported. RESULTS: A statistically significant difference was found in platelet counts between CKCS and mixed breed dogs (P < 0.0001). CKCS had a platelet count that was 32% that of the controls (95% confidence interval, 28 to 37%). There was no significant difference between methods used to count platelets. Thirty percent of CKCS had macrothrombocytes. Pedigree analysis and examination of obtained and expected segregation ratios from 17 CKCS families supported an autosomal recessive pattern of Mendelian inheritance. CONCLUSIONS: A high prevalence of idiopathic macrothrombocytopenia exists in CKCS in NSW and automated or blood smear estimates are sufficient to count platelet numbers. Data supports an autosomal recessive inheritance pattern. 相似文献