全文获取类型
收费全文 | 365篇 |
免费 | 19篇 |
专业分类
林业 | 9篇 |
农学 | 1篇 |
基础科学 | 4篇 |
49篇 | |
综合类 | 34篇 |
农作物 | 8篇 |
水产渔业 | 20篇 |
畜牧兽医 | 206篇 |
园艺 | 2篇 |
植物保护 | 51篇 |
出版年
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 6篇 |
2009年 | 15篇 |
2008年 | 25篇 |
2007年 | 29篇 |
2006年 | 15篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 2篇 |
1968年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有384条查询结果,搜索用时 15 毫秒
81.
82.
Enhanced degradation of atrazine has been reported in the literature, indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine applications each year, Gossypium hirsutum L.-Z. mays rotation (CCR) receiving applications of atrazine once every 2 years and a no atrazine history soil (NAH). Subsequent laboratory and greenhouse experiments were conducted with soil collected from these cropping systems to determine atrazine degradation, mineralization and residual weed control. Field dissipation of atrazine followed first-order kinetics, and calculated half-life values for atrazine combined over 2003 and 2005 increased in the order of CC (9 d) = CCR (10 d) < NAH (17 d). Greenhouse studies confirmed that the persistence of atrazine was approximately twofold greater in NAH soil than in CC or CCR soil. Biometer flask mineralization studies suggested that enhanced degradation of atrazine was due to rapid catabolism of the s-triazine ring. Glasshouse efficacy studies revealed a loss of residual weed control in CC and CCR soil compared with NAH soil. These data indicate that, under typical Mississippi Delta field conditions and agronomic practices, the persistence of atrazine may be reduced by at least 50% if the herbicide is applied more than once every 24 months. Glasshouse studies suggest that under these conditions a loss of residual weed control is possible. 相似文献
83.
Best A La Ragione RM Clifford D Cooley WA Sayers AR Woodward MJ 《Veterinary microbiology》2006,113(1-2):63-72
Isolation of Shiga-toxin (Stx) positive Escherichia coli O157:H7 from commercially grown pigs has been reported. Furthermore, experimental infection studies have demonstrated that Stx-positive E. coli O157:H7 can persist in 12-week-old experimentally orally inoculated conventional pigs for up to 2 months and that persistence was not dependent upon intimin. We have shown that the flagellum of Stx-negative E. coli O157:H7 does not have a role to play in pathogenesis in ruminant models whereas, in poultry, the flagellum of E. coli O157:H7 was important for long-term persistent infection. The contribution of the flagellum of Stx-negative E. coli O157 in the colonisation of pigs was investigated by adherence assays on a porcine (IPI-21) cell line, porcine in vitro organ culture (IVOC) and experimental oral inoculation of conventional 14-week-old pigs. E. coli O157:H7 NCTC12900nal(r) and isogenic aflagellate and intimin deficient mutants adhered equally well to IPI-21 cells. In porcine IVOC association assays, E. coli O157:H7 NCTC12900nal(r) was associated in significantly higher numbers to tissues from the caecum and the terminal rectum than other sites. The aflagellate and intimin deficient mutants significantly adhered in greater numbers to more IVOC gastrointestinal tissues than the parent. Groups of 14-week-old pigs were dosed orally with 10(10)CFU/10ml of either E. coli O157:H7 NCTC12900nal(r) or isogenic aflagellate and intimin deficient mutants and recovery of each test strain was similar. Histological analysis of pig tissues at post mortem examination revealed that E. coli O157 specifically stained bacteria were associated with the mucosa of the ascending and spiral colon. These data suggest that colonisation and persistence of Stx-negative E. coli O157:H7 in pigs, involves mechanisms that do not require the flagellum or intimin. 相似文献
84.
Saper CB 《Science (New York, N.Y.)》2006,314(5800):773-774
85.
K. A. Skorupski C. O. Rodriguez E. L. Krick C. A. Clifford R. Ward M. S. Kent 《Veterinary and comparative oncology》2009,7(2):139-144
Histiocytic sarcoma (HS) is associated with a poor prognosis owing to the presence of metastasis at the time of diagnosis in most dogs. Improved outcome has been reported in several dogs with localized HS following local therapy, however, distant metastasis occurs in 70–91% of dogs suggesting that adjuvant systemic therapy is necessary. The purpose of this retrospective study was to describe clinical characteristics and outcome in dogs with localized HS treated with aggressive local therapy plus adjuvant CCNU chemotherapy. Data from 16 dogs were evaluated. The median disease‐free interval was 243 days. Two dogs had local recurrence and eight dogs developed metastatic disease with a median time to relapse of 201 days in these 10 dogs. The median survival time for all 16 dogs was 568 days. These results support the recommendation for aggressive local therapy combined with adjuvant CCNU chemotherapy in dogs with localized HS. 相似文献
86.
Henry CJ Turnquist SE Smith A Graham JC Thamm DH O'Brien M Clifford CA 《Journal of Feline Medicine and Surgery》1999,1(3):165-170
A search from databases of four veterinary colleges and one private referral practice between January 1992 and April 1998 provided 20 cases diagnosed with primary renal neoplasia. Review of these cases revealed 19 primary renal tumours, excluding lymphoma. Of the 20 histologically reviewed cases, the diagnosis was amended in eight. There were 13 renal carcinomas (11 tubular and two tubulopapillary), three transitional cell carcinomas, one malignant nephroblastoma, one haemangiosarcoma and one adenoma. The haemangiosarcoma is, to our knowledge, the first reported case of this tumour type as a primary renal tumour in the cat. Most cats were presented for non-specific clinical signs such as anorexia and weight loss. One cat presented with tumour-associated polycythaemia which has not, to our knowledge, been reported previously. The metastatic rate for cats with complete staging was 64%, and 100% for transitional cell carcinomas. 相似文献
87.
88.
89.
Gregory B. Daniel DVM MS Robert C. Denovo DVM Dorothy S. Sharp BS Karen Tobias DVM MS Clifford Berry DVM 《Veterinary radiology & ultrasound》2004,45(1):78-84
The purpose of this study was to evaluate nonuniform patterns of vascular distribution of pertechnetate in the dog during per-rectal portal scintigraphy. Ninety-two studies were reviewed retrospectively to document the patterns of radionuclide distribution. Forty-five studies were classified as normal and 47 were classified as diagnostic for a macrovascular portosystemic shunt. In these dogs, shunt fractions were calculated and compared using a t-test. In dogs with sufficient liver radioactivity for evaluation, the study was classified as having uniform, dorsal, central, or ventral radiopharmaceutical distributions. There were 51 animals (45 normal and six dogs with low-magnitude portosystemic shunts) with sufficient liver activity to assess the radionuclide distribution within the liver. A one-way ANOVA was used to compare shunt fractions between each of the distribution patterns. Two dogs were anesthetized and selective portovenograms were performed. Portovenograms were compared with the scintigraphic images to correlate the vascular distribution of the right, central, and left divisional branches of the portal vein. The shunt fraction in the 45 normal dogs was significantly lower than in the dogs with portosystemic shunts (5.7% +/- 4.8% vs. 78.6% +/- 20.0% (mean +/- SD), P < 0.001). Of the 51 dogs with sufficient liver activity to classify the pattern of distribution, there were 15/51 (31.4%) with uniform radionuclide distribution, 10/51 (19.6%) with focal dorsal distribution, 15/51 (29.4%) with focal ventral distribution, and 10/51 (19.6%) with focal central distribution. There was no significant difference in the shunt fractions between the groups. There were six dogs diagnosed with low-magnitude portosystemic shunt with sufficient liver radioactivity to categorize the vascular distribution of the radionuclide within the liver. Of these six dogs, two had focal dorsal distribution, one had focal central, one had focal ventral and two had uniform distribution. Focal dorsal distribution could result from streamlining of the radionuclide into the right divisional branch of the portal vein. Focal ventral distribution could result from streamlining the radionuclide into the left divisional branch of the portal vein. Focal central distribution could result from streamlining the radionuclide into the central divisional branch of the portal vein. 相似文献
90.
Andrew B. Prather Clifford R. Berry Donald E. Thrall 《Veterinary radiology & ultrasound》2005,46(2):114-121
Computed tomography (CT) of the thorax was performed in 28 dogs and five cats and findings were compared with previous thoracic radiographs. The sample population included all animals that had thoracic radiographs and a CT study within 5 days of each other, where the complete imaging studies were available for review. Thoracic radiographs were considered indeterminate in 31 patients and CT examinations were done to acquire additional information. The presence of additional information from CT relating to presence of pathology, location of pathology, extent of pathology, and involvement of mediastinal structures was recorded. Whether there was a change in diagnosis based on the CT findings was also recorded. In only 4/33 animals (all dogs) did CT fail to provide any new information for the parameters evaluated when compared with survey thoracic radiographs. Additional information about the pathology that was present was gained by CT in 5/5 cats and 21/ 28 dogs. New information on compartmental location of pathology was seen in 4/5 cats and 19/28 dogs. New information on pathology extent was noted in 5/5 cats and 20/28 dogs. Additional information regarding involvement of mediastinal structures was obtained in 2/5 cats and 10/28 dogs. A change in diagnosis was made in 3/5 cats and 13/28 dogs. In conclusion, CT is a valuable tool for evaluating intrathoracic disease. CT provides additional cross-sectional anatomic information that can aid in anatomic localization and evaluation of the extent of the pathology in question. 相似文献