全文获取类型
收费全文 | 624篇 |
免费 | 20篇 |
专业分类
林业 | 13篇 |
农学 | 11篇 |
45篇 | |
综合类 | 119篇 |
农作物 | 7篇 |
水产渔业 | 8篇 |
畜牧兽医 | 411篇 |
园艺 | 8篇 |
植物保护 | 22篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 26篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 30篇 |
2007年 | 29篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 29篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1971年 | 8篇 |
1970年 | 8篇 |
1969年 | 5篇 |
1960年 | 4篇 |
排序方式: 共有644条查询结果,搜索用时 15 毫秒
131.
Borostyankoi F Rooks RL Kobluk CN Reed AL Littledike ET 《Journal of the American Veterinary Medical Association》2003,222(1):54-59
OBJECTIVE: To evaluate feasibility of single-session bilateral triple pelvic osteotomy with 8-hole iliac bone plates in dogs with bilateral hip dysplasia. DESIGN: Retrospective study. ANIMALS: 95 dogs with bilateral hip dysplasia. PROCEDURE: Medical records were reviewed, and information was obtained on signalment; body weight; angles of subluxation and reduction prior to surgery; durations of surgery and hospitalization; postoperative mobility; severity of lameness, radiographic grade of hip dysplasia, Norberg angle, and femoral head coverage before and after surgery; time required for radiographic evidence of iliac healing; change in pelvic diameter; implant integrity; and complications. RESULTS: Mean age at the time of surgery was 10.8 months, and mean weight was 35.2 kg (77.4 lb). Prior to surgery, mean angles of subluxation were 2.2 degrees on the right and 2.6 degrees on the left; mean angles of reduction were 25.9 degrees on the right and 27.3 degrees on the left. Mean surgical time was 95 minutes. All but 1 dog were able to walk on their own by the fourth day after surgery. Mean hospitalization time was 7.5 days. Clinical signs of lameness and radiographic grade of hip dysplasia were significantly improved during follow-up examinations. Mean time for radiographic iliac healing was 8 weeks. None of the plates and only 7 of the 1,520 (0.5%) screws loosened after surgery. Nineteen dogs had complications, but all complications were minor. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that single-session bilateral triple pelvic osteotomy with 8-hole iliac bone plates is effective for treatment of dogs with bilateral hip dysplasia. 相似文献
132.
Benign masses in the pericardium of two dogs 总被引:1,自引:0,他引:1
Two miniature Schnauzer dogs were treated for pericardial masses. In one dog the mass consisted of necrotic fat that was attached to the apex of the pericardium by a pedicle. No obvious communication with the abdomen was present. The second dog had a peritoneopericardial hernia associated with a chronic cystic haematoma. In each case the mass was presumed to have arisen following congenital displacement of the omentum into the pericardium. The pericardial mass was removed and subtotal pericardectomy performed in both dogs. Recovery was complete in each case. 相似文献
133.
Blood samples were collected from 41 cats presented for pre-anaesthetic assessments, routine geriatric screening, or re-assessment of ongoing chronic medical disorders. Samples were either left to clot or anticoagulated with lithium heparin, then assessed for their potassium concentration within 1h of collection, and again after remaining in contact with their cell pellet for 48 h. There was a significantly higher potassium concentration in the serum samples compared to the plasma samples, both in the basal and 48-h samples (although this difference was most marked in the basal samples). Ageing of both serum and plasma samples also resulted in an increase in the potassium concentration when compared with the basal values for each sample type. The mean difference (basal serum minus basal plasma) in potassium concentration was 0.47 mmol/l. While it is probable that the potassium came from either leukocytes and/or thrombocytes the mean total leukocyte count and the mean thrombocyte count were below the upper limit of the reference intervals for our laboratory and the rise in the potassium level did not appear to be directly related to either of these values. 相似文献
134.
Suppurative lower airway disease is a common debilitating disease in performance horses and, while rarely fatal, is often recalcitrant to conventional therapy. A variety of treatments have been used to combat this condition and we conducted two types of studies to determine if caprine serum fraction--immunomodulator (CSFI), a nonspecific immunomodulator, improved recovery from lower respiratory disease. Two dose response studies were performed to ascertain the efficacy of CSFI. Horses were maintained daily on conventional antibiotic therapy. Respiratory tract exudate, nasal discharge, dyspnoea, chest auscultation and cough frequency were monitored weekly. One hundred percent of the horses treated with 2 i.m. injections of either 60 or 120 mg CSFI one week apart showed significant improvement with each weekly evaluation and were fully recovered by week 3. Horses treated with 15 or 30 mg CSFI did not differ significantly from the control group. Only 10% of the control horses responded to conventional antibiotic therapy. An expanded field trial utilising 80 horses diagnosed with lower respiratory disease and housed at 4 equine clinics was conducted. Thirty-five percent of the 40 control horses, treated solely by conventional antibiotic therapies, recovered while 75% of the horses treated with a supplemental administration of 60 mg CSFI as described above recovered. The combined data from these studies showed that CSFI was able to promote an overall recovery from lower respiratory disease of 86%. 相似文献
135.
Rohrbach BW Legendre AM Baldwin CA Lein DH Reed WM Wilson RB 《Journal of the American Veterinary Medical Association》2001,218(7):1111-1115
OBJECTIVE: To determine proportions of cats in which feline infectious peritonitis (FIP) was diagnosed on an annual, monthly, and regional basis and identify unique characteristics of cats with FIP. DESIGN: Case-control study. SAMPLE POPULATION: Records of all feline accessions to veterinary medical teaching hospitals (VMTH) recorded in the Veterinary Medical Data Base between January 1986 and December 1995 and of all feline accessions for necropsy or histologic examination at 4 veterinary diagnostic laboratories. PROCEDURE: Proportions of total and new feline accessions for which a diagnosis of FIP was recorded were calculated. To identify characteristics of cats with FIP, cats with FIP were compared with the next cat examined at the same institution (control cats). RESULTS: Approximately 1 of every 200 new feline and 1 of every 300 total feline accessions at VMTH in North America and approximately 1 of every 100 accessions at the diagnostic laboratories represented cats with FIP. Cats with FIP were significantly more likely to be young, purebred, and sexually intact males and significantly less likely to be spayed females and discharged alive than were control cats. The proportion of new accessions for which a diagnosis of FIP was recorded did not vary significantly among years, months, or regions of the country. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that FIP continues to be a clinically important disease in North America and that sexually intact male cats may be at increased risk, and spayed females at reduced risk, for FIP. The high prevalence of FIP and lack of effective treatment emphasizes the importance of preventive programs, especially in catteries. 相似文献
136.
D. H. Putnam R. Long B. A. Reed & W. A. Williams 《Journal of Agronomy and Crop Science》2001,187(2):75-81
Many alfalfa ( Medicago sativa L.) fields are sprayed each year with insecticides to control Egyptian alfalfa weevil ( Hypera brunneipennis ) and the alfalfa weevil ( Hypera postica ). Overseeding various species of legumes and grasses into established alfalfa has been proposed as a method to mitigate weevil damage without insecticides. Established fields of alfalfa were overseeded with legumes and grasses in randomized complete block designs in three years of study in a Mediterranean climate in the Sacramento Valley of California, USA. Several overseeding practices maintained or increased yields compared with the insecticide-sprayed treatment. Overseeding increased or maintained forage yield, eliminating the need for insecticides. However, overseeding did not prevent weevil damage to alfalfa. Overseeding is best used to extend the life of alfalfa stands in the final year of production, since overseeding can thin alfalfa stands. Market acceptance for mixed-species hay and harvest management of overseeded forages are the most important limitations to overseeding practices. 相似文献
137.
1 -Antitrypsin deficiency: a variant with no detectable 1 -antitrypsin 总被引:14,自引:0,他引:14
No alpha(1)-antitrypsin could be detected in the serum of a 24-year-old man with advanced pulmonary emphysema by agarose electrophoresis, immnuno-electrophoresis, double diffusion in agarose gel, or alpha(1)-antitrypsin genetic typing by a combination of starch-gel electrophoresis and crossed antigen-antibody electrophoresis. A circulating alpha(1)-antitrypsin inactivator could not be demonstrated. Evidence was obtained in family members of genetic transmission of this new alpha(1)-antitrypsin variant. 相似文献
138.
Evidence of pathotypes among Australian isolates of crown rust infecting perennial ryegrass 总被引:2,自引:0,他引:2
Fifty‐three genotypes of perennial ryegrass selected from a range of cultivars and ecotypes were evaluated for their reaction to crown rust isolates collected from Western Australia, Victoria, Queensland, South Australia or New South Wales in Australia. The reactions of the clones to inoculation provided evidence for the development of a differential set of perennial ryegrass genotypes, but also demonstrated that a large number of genotypes displayed universal reactions to infection with any of the crown rust isolates. 相似文献
139.
Access to the Internet is an essential determinant of innovation, which has received little attention in the literature. This paper emphasizes the role of Internet accessibility in lowering information costs and therefore boosting regional innovation activity. We construct a simple theoretical model to illustrate the positive impact of decreased discovery costs, proxied by the accessibility of the Internet, on innovation. To test this hypothesis, we exploit a county‐level data set in the U.S. and run three types of regression with and without instruments: OLS, negative binomial, and Poisson. Within each method, we employ four levels of download speeds. We find a positive relationship between the access to the Internet and the number of patents filed in that specific county. This effect is particularly strong in the case of access to download speeds of 10 Mbps. Our analysis suggests that access to the Internet lowers information disseminating costs and therefore encourages more patents filed in the county. The results also indicate that access to the Internet matters more than faster Internet speed for innovation. Policy implications for these results suggest that if there were a minimum Internet access initiative, there could potentially be a significant increase in innovation by the U.S. 相似文献
140.
Farms and ranches constitute one of the most hazardous work environments in America, and perhaps in the world, yet farm scenes are often portrayed as tranquil, picture-perfect settings. A review of 293 photographs that included persons and tractors, livestock, powered equipment, all-terrain vehicles, or bodies of water was undertaken by two independent reviewers. Predetermined criteria that captured best safety practices in agriculture were applied to each photograph. A rating of 1 (best practices), 2 (unsafe practices) or 3 (mixed messages) was given to each photograph. Three popular farm periodicals with various geographic distribution areas across the U.S. were examined. Issues from June 2005 through October 2006 were included in the review. Results revealed that only 56.7% of the photographs illustrated best practices for safety. Of the 27 photographs that included children, only 18.5% depicted best practices. Photographs in advertisements, where the settings can be staged, illustrated best practices 56.5% of the time. Editors, photo-journalists, and advertisers should take every opportunity to promote safety in this high-risk industry through portrayal of safe work practices and safe work environments in photographs that are used in farm periodicals. 相似文献