全文获取类型
收费全文 | 155737篇 |
免费 | 9051篇 |
国内免费 | 83篇 |
专业分类
林业 | 6028篇 |
农学 | 5478篇 |
基础科学 | 1041篇 |
18925篇 | |
综合类 | 26846篇 |
农作物 | 6272篇 |
水产渔业 | 8110篇 |
畜牧兽医 | 80173篇 |
园艺 | 2024篇 |
植物保护 | 9974篇 |
出版年
2019年 | 1517篇 |
2018年 | 2330篇 |
2017年 | 2733篇 |
2016年 | 2528篇 |
2015年 | 2163篇 |
2014年 | 2662篇 |
2013年 | 6152篇 |
2012年 | 4692篇 |
2011年 | 5674篇 |
2010年 | 3746篇 |
2009年 | 3699篇 |
2008年 | 5502篇 |
2007年 | 5197篇 |
2006年 | 5032篇 |
2005年 | 4489篇 |
2004年 | 4309篇 |
2003年 | 4345篇 |
2002年 | 4054篇 |
2001年 | 5322篇 |
2000年 | 5190篇 |
1999年 | 4107篇 |
1998年 | 1726篇 |
1997年 | 1712篇 |
1996年 | 1494篇 |
1995年 | 1742篇 |
1994年 | 1559篇 |
1993年 | 1568篇 |
1992年 | 3200篇 |
1991年 | 3280篇 |
1990年 | 3180篇 |
1989年 | 3226篇 |
1988年 | 2823篇 |
1987年 | 2921篇 |
1986年 | 2973篇 |
1985年 | 2852篇 |
1984年 | 2277篇 |
1983年 | 1976篇 |
1982年 | 1424篇 |
1979年 | 1949篇 |
1978年 | 1550篇 |
1977年 | 1303篇 |
1976年 | 1297篇 |
1975年 | 1466篇 |
1974年 | 1726篇 |
1973年 | 1717篇 |
1972年 | 1624篇 |
1971年 | 1559篇 |
1970年 | 1528篇 |
1969年 | 1448篇 |
1967年 | 1304篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
B.D. Scott BS MS G.D. Potter PhD J.W. Evans PhD J.C. Reagor PhD G.W. Webb PhD S.P. Webb MS 《Journal of Equine Veterinary Science》1989,9(4)
Twenty-four yearlings were used to evaluate the efficacy of feeding feed-grade fat to growing horses. All horses were started on trial at 13-months-of-age and were fed for 112 days. The experimental diets, containing similar nutrient-to-calorie ratios, were: 1) control (no added fat; 2) 5% added fat and; 3) 10% added fat. There was a trend for yearlings fed the 10% added fat diet to grow faster and eat less feed than those on the control diet. Data from this study indicate that feed-grade fat can be safely fed to growing horses. Feeding fat to yearlings stimulated growth and efficiency of feed utilization initially, but these effects were not maintained as the yearlings grew toward maturity. 相似文献
992.
993.
R L Hamlin C A Buffington 《Veterinary Clinics of North America: Small Animal Practice》1989,19(3):527-538
Nutritional deficiencies (e.g., carnitine in dogs, taurine in cats) resulting in cardiomyopathy, and nutritional excesses (e.g., calories leading to obesity, sodium leading to hypertension) have emerged as important considerations in cardiology. These dietary factors may become particularly exaggerated in altered physiological and/or pathological states (e.g., pregnancy, old age, primary cardiovascular disease). Unfortunately, we do not have complete information on requirements for essential nutrients, nor do we know the precise role nutrition may play in the production of so-called old-age diseases or on the interactions among other organ systems (e.g., kidney, liver) and the heart. 相似文献
994.
J Bentinck-Smith A A Padhye W R Maslin C Hamilton R K McDonald B J Woody 《Journal of veterinary diagnostic investigation》1989,1(4):295-298
Pythium insidiosum was isolated from the subcutaneous tissue of a 1-year-old tan crossbreed dog and from the intestinal tract of an 18-month-old Samoyed male. Gomori's methenamine silver stain was superior to hematoxylin and eosin in demonstrating the organism in tissue sections. The agent was identified as P. insidiosum by zoospore formation in an aqueous yeast extract solution containing grass blades. Exoantigens produced in culture were shown to be identical to known P. insidiosum antigens by microimmunodiffusion. 相似文献
995.
U.S Salisu C.A Kudi J.O.O. Bale M Babashani B.Y Kaltungo S.N.A Saidu A Asambe A.Y Baba 《Tropical animal health and production》2017,49(5):1041-1046
A cross-sectional study was carried out to determine the status of Brucella infection in one-humped (Dromedary) camels in the North and Central senatorial districts of Katsina State, Nigeria. Nine hundred and eighty serum samples from live and slaughtered camels were tested. Modified Rose Bengal plate test (RBPT) and serum agglutination test (SAT) with ethylenediaminetetraacetic acid, (EDTA) were used as screening and standard tests, respectively. The prevalence of Brucella antibodies were 110 (11.2%) and 103 (10.5%) for RBPT and SAT, respectively. Of the 472 and 508 serum samples tested from the herds and abattoirs, respectively, 63 (13.3%) and 47 (9.3%) were positive by RBPT while 62 (13.1%) and 41 (8.1%) were positive by SAT, respectively. Based on the results, it was concluded that Brucella antibodies were present in camels in the study area. Poor management practices and mixing of camels with other species of livestock as well as unrestricted movement of camels were proposed to be the reasons for the prevalence of the disease in the study area. In view of the public health importance of the disease, it is recommended that there is the need to develop a strategic plan to decrease spread of brucellosis in the study area. 相似文献
996.
997.
Eight strains of Taylorella equigenitalis were identified by a polymerase chain reaction using a primer pair specific to the 16S rDNA of T equigenitalis. These eight strains were chosen because they had previously been shown to represent eight distinct genotypes by pulsed-field gel electrophoresis analysis after separate digestion of the genomic DNA with ApaI or NotI. The eight strains could be classified into six or seven types by random amplified polymorphic DNA analysis using different kinds of primers. Amplified rDNA restriction analysis after separate digestion with five restriction enzymes, including AluI and MboI, of the 1,500 bp fragments of rDNA amplified by polymerase chain reaction did not discriminate the genomic variations among the eight strains of T equigenitalis. Thus, pulsed-field gel electrophoresis was shown to discriminate these eight organisms better than random amplified polymorphic DNA analysis, while amplified rDNA restriction analysis was found to be unsuitable for subtyping T equigenitalis. 相似文献
998.
R S Walton 《Veterinary Clinics of North America: Small Animal Practice》2001,31(4):729-59, ix
Thoracoscopy is a minimally invasive operative endoscopic procedure designed for visual inspection of the thoracic cavity. The use of small, highly maneuverable, rigid telescopes allows visualization beyond what is possible by standard operative techniques. The use of a small video camera attached to a standard rigid telescope allows the operator and assistants to view a simultaneous, enlarged, and clear image. This article focuses on the basic diagnostic and surgical techniques used in veterinary video-assisted thoracoscopy. 相似文献
999.
Dixon PM McGorum BC Railton DI Hawe C Tremaine WH Pickles K McCann J 《Equine veterinary journal》2001,33(5):452-458
Referred cases (n = 375) of laryngeal paralysis (1985-1998) from a mixed-breed equine population included 351 (94%) cases of recurrent laryngeal neuropathy (RLN) (idiopathic laryngeal hemiplegia) and 24 cases (6%) of laryngeal paralysis from causes other than RLN. Laryngeal movements were classified endoscopically into one of 6 grades, in contrast to the usual 4 grades. The RLN cases had a median grade 4 laryngeal paralysis, of which 96% were left-sided, 2% right-sided and 2% bilaterally affected. RLN cases included 204 (58%) Thoroughbred, 96 (27%) Thoroughbred-cross, 23 (7%) draught, 16 (5%) Warmbloods and 10 (3%) other breeds, including only 4 (1%) ponies. The median age of RLN cases at referral was 6 years (range 2-12) and their median height was 170.2 cm. The work of RLN horses included National Hunt racing (42%), flat racing (1%), hunting (19%), eventing (16%) and miscellaneous work (22%). Reported presenting signs in RLN-affected horses included abnormal exercise-related respiratory sounds in 90% and reduced exercise tolerance in only 64%. However, many horses were referred before their exercise tolerance could be fully assessed. Forty percent of the RLN cases had intercurrent disorders, including 10% with additional upper respiratory and 7% with lower respiratory tract diseases. The 24 nonidiopathic RLN cases included 12 with bilateral laryngeal paralysis, 11 (92%) of which were ponies. Bilateral laryngeal paralysis occurred with hepatic encephalopathy in 7 cases and following general anaesthesia in 2 cases. The 12 cases of acquired unilateral laryngeal paralysis included 7 caused by guttural pouch mycosis. 相似文献
1000.
Marg H Scholz HC Arnold T Rösler U Hensel A 《Berliner und Münchener tier?rztliche Wochenschrift》2001,114(9-10):385-388
In this study a Salmonella Typhimurium infection model in swine was used in order to investigate the influence of pre-mortal stress induced by long time period transportation on the re-activation of Salmonella in experimentally infected pigs. Salmonella free pigs were exposed to a highly virulent strain of Salmonella Typhimurium DT104 by direct intragastrical administration. Clinical parameters were monitored and the shedding rate in faeces was qualitatively and quantitatively determined by standard bacteriological procedures for 21 days. The distribution of the challenge organism in 14 different internal organs of transported and nontransported animals was determined. All infected animals developed clinical signs of salmonellosis 12 to 24 hours post infection. About 88 to 100% of the fecal samples were culture-positive up to post exposure day 6, and then varied from 71 to 92% until slaughter, respectively. At necropsy S. Typhimurium was recovered most frequently from caecum and ileocolic lymph nodes (83%), colon (79%), palatine tonsils (71%) and mandibular lymph nodes (62.5%). A negative impact of transportation stress on the shedding rate and the general condition of the animals was observed. 相似文献