全文获取类型
收费全文 | 124796篇 |
免费 | 7122篇 |
国内免费 | 73篇 |
专业分类
林业 | 4365篇 |
农学 | 4017篇 |
基础科学 | 709篇 |
14544篇 | |
综合类 | 22534篇 |
农作物 | 4826篇 |
水产渔业 | 6420篇 |
畜牧兽医 | 65229篇 |
园艺 | 1555篇 |
植物保护 | 7792篇 |
出版年
2019年 | 1125篇 |
2018年 | 1768篇 |
2017年 | 1963篇 |
2016年 | 1833篇 |
2015年 | 1586篇 |
2014年 | 1904篇 |
2013年 | 4754篇 |
2012年 | 3504篇 |
2011年 | 4246篇 |
2010年 | 2857篇 |
2009年 | 2792篇 |
2008年 | 4145篇 |
2007年 | 3985篇 |
2006年 | 3784篇 |
2005年 | 3529篇 |
2004年 | 3390篇 |
2003年 | 3429篇 |
2002年 | 3162篇 |
2001年 | 4342篇 |
2000年 | 4261篇 |
1999年 | 3385篇 |
1998年 | 1398篇 |
1997年 | 1283篇 |
1996年 | 1136篇 |
1995年 | 1424篇 |
1994年 | 1278篇 |
1993年 | 1208篇 |
1992年 | 2645篇 |
1991年 | 2753篇 |
1990年 | 2680篇 |
1989年 | 2690篇 |
1988年 | 2405篇 |
1987年 | 2541篇 |
1986年 | 2545篇 |
1985年 | 2406篇 |
1984年 | 1950篇 |
1983年 | 1719篇 |
1982年 | 1180篇 |
1981年 | 1044篇 |
1979年 | 1614篇 |
1978年 | 1302篇 |
1977年 | 1131篇 |
1976年 | 1071篇 |
1975年 | 1173篇 |
1974年 | 1416篇 |
1973年 | 1466篇 |
1972年 | 1424篇 |
1971年 | 1305篇 |
1970年 | 1230篇 |
1969年 | 1191篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
A 10-year survey of antimicrobial susceptibility of streptococcus suis isolates from swine in Japan 总被引:7,自引:0,他引:7
Kataoka Y Yoshida T Sawada T 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2000,62(10):1053-1057
A number of 689 Streptococcus suis isolates collected nationwide from diseased and healthy pigs from 1987 to 1996 were surveyed for antibiotic susceptibilities to 11 drugs. No isolates resistant to amoxicillin, chloramphenicol, and sulfamethoxazole/trimethoprim were found. Isolates were highly susceptible to penicillins (penicillin G, ampicillin, and amoxicillin) except cloxacillin. They were not susceptible to tetracycline, streptomycin, and kanamaycin (MIC90 50 microg/ml, > or = 100 microg/ml, and > or = 100 microg/ml, respectively). Multiple-resistant isolates (> or = 3 antimicrobial agents) were found in 20.3% of all isolates tested. 相似文献
942.
OBJECTIVE: To study the role of lectures from the perspective of staff and students involved in the veterinary course at The University of Queensland. METHODS: The Nominal Group Technique of Delbecq et al, which provides the maximum opportunity for group members to put forward points, was used to help develop a questionnaire which was completed by 351 students (a response rate of 84%) and 35 staff (76%) from the five years of the veterinary course, and was analysed using the SAS System for Windows. RESULTS: Almost all the staff and students agreed that lectures should fulfil many roles including stimulating and motivating students and encouraging them to think, as well as presenting ideas and concepts and an indication of the structure and relevance of the material. They should provide a guide for effective deep learning, but not encourage rote (or superficial) learning. A smaller percentage of staff and even fewer students agreed that lectures did fulfil these roles, especially those directed at encouraging students to look beyond simple memorisation of facts. The perceived disparity between reality and the ideal was greater amongst the older, clinical students than amongst their more junior colleagues. CONCLUSIONS: The focus of attention in lectures needs to change from the superficial, rote learning of information to deep, active learning directed at using information to solve problems that are perceived by the students to be relevant. If done in a stimulating and interesting way, this should develop skills in reasoning and critical analysis as well as providing a framework for storage and recall. It should also increase the motivation towards learning both during the veterinary course, and over the professional lifetime. Furthermore, the place of the lecture in veterinary education needs to be reassessed regularly in the face of newly-emerging educational technology. 相似文献
943.
Hill PB Auxilia ST Munro E Genovese L Silkstone MA Kirby B 《The Journal of small animal practice》2000,41(11):519-523
A nine-year-old, neutered female Shetland sheepdog was presented with crusted, ulcerative skin lesions affecting the footpads, commissures of the lips and the lateral canthi of the eyes. Histopathological examination of skin biopsies revealed changes consistent with superficial necrolytic dermatitis and biochemical analysis demonstrated elevated liver enzymes. Abdominal radiography revealed a small liver which, on ultrasonography, appeared diffusely mottled and showed changes suggestive of periportal fibrosis. On exploratory laparotomy, the pancreas appeared normal, but the liver was small and had multiple nodules throughout the parenchyma. This appearance was confirmed as cirrhosis on histopathological examination. The dog was placed on a hepatic support diet and treated with colchicine, essential fatty acid supplementation and raw egg yolks. After four weeks, the skin lesions had resolved and the dog remained free of clinical signs over a 22-month follow-up period. 相似文献
944.
Yersinia ruckeri causes enteric red mouth (ERM) disease in salmonids. Serologic identification of Y. ruckeri is hampered by cross-reactivity with other bacterial isolates of fish origin. Oligonucleotide primers incorporating Y. ruckeri unique sequences were designed to amplify a 409 bp fragment of Y. ruckeri 16S rDNA. The primers did not amplify other genetically related Yersinia or a wide variety of other aquatic or piscine bacteria. This assay provides a rapid, definitive identification of Y. ruckeri that is not subject to the variability inherent in serologic methods. 相似文献
945.
C A Johnson-Delaney 《Veterinary Clinics of North America: Exotic Animal Practice》2000,3(1):173-81, vii
Exotic marsupials are becoming popular companion pets, yet little pharmacologic information is available to the practitioner. Species include sugar gliders (Petarus breviceps), South American (Brazilian) short-tailed opossums (Monodelphis domestica), brushtail possum or "phalanger" (Trichosurus vulpecula), and wallabies: Bennett's (Macropus rufogriseus rufogriseus) and Tammar or Dama (Macropus eugenii). Guidelines for logical choices of medications based on allometric scaling, gastrointestinal tract anatomy and physiology, and liver metabolism are given. An example of scaling and a formulary based on anecdotal, published medications are provided. 相似文献
946.
C A Ragle 《Veterinary Clinics of North America: Equine Practice》2000,16(2):317-28, vi
The ventral abdominal approach for laparoscopy is versatile. Reported techniques using a ventral approach in the mare include bilateral ovariectomy and granulosa cell tumor removal. Laparoscopic ovariectomy is performed by way of four instrument portals in the caudoventral aspect of the insufflated abdomen. The procedure has several advantages over the traditional approaches of colpotomy and celiotomy, including tension-free closure of all incisions and minimal invasiveness. 相似文献
947.
Cryptosporidial oocyst shedding was detected in a 2.5-year-old Quarterhorse stallion with diarrhoea. Based on the detection of cryptosporidial oocysts, and the absence of other aetiological agents or enteropathogens, cryptosporidiosis was presumptively diagnosed. This case was unusual because cryptosporidial oocyst shedding is primarily found in some immunocompromised or immature horses, and has not been reported in healthy mature horses. 相似文献
948.
Frisbie DD Sandler EA Trotter GW McIlwraith CW 《American journal of veterinary research》2000,61(4):436-441
OBJECTIVE: To determine response of interleukin-1alpha (IL-1alpha)-conditioned equine articular cartilage explants to insulin-like growth factor-1 (IGF-1). Sample Population-Cartilage from the trochlea and condyles of the femur of a clinically normal 4-year-old horse. PROCEDURE: Effects of IGF-1 (0 to 500 ng/ml) after addition of IL-1alpha were evaluated by assessing matrix responses, using a sulfated glycosaminoglycan (GAG) assay, matrix 35SO4 GAG incorporation, and release of GAG. Mitogenic response was assessed by 3H-thymidine incorporation into DNA and fluorometric assay of total DNA concentration. RESULTS: Human recombinant IL-1alpha (40 ng/ml) increased the amount of labeled GAG released and decreased labeled and total GAG remaining in explants, and IL-1alpha decreased mitogenic response. Addition of IGF-1 counteracted effects seen with IL-1alpha alone. In general, IGF-1 decreased total and labeled GAG released into the medium, compared with IL-1alpha-treated explants (positive-control sample). Values for these variables did not differ significantly from those for negative-control explants. A significant increase in total and newly synthesized GAG in the explants at termination of the experiment was observed with 500 ng of IGF-1/ml. Labeled GAG remaining in explants was greater with treatment at 50 ng of IGF-1/ml, compared with treatment with IL-1alpha alone. Concentrations of 200 ng of IGF-1/ml abolished actions of IL-1alpha and restored DNA synthesis to values similar to those of negative-control explants. CONCLUSIONS AND CLINICAL RELEVANCE: IGF-1 at 500 ng/ml was best at overcoming detrimental effects associated with IL-1alpha in in vitro explants. These beneficial effects may be useful in horses with osteoarthritis. 相似文献
949.
Genetic typing of classical swine fever virus 总被引:18,自引:0,他引:18
Paton DJ McGoldrick A Greiser-Wilke I Parchariyanon S Song JY Liou PP Stadejek T Lowings JP Björklund H Belák S 《Veterinary microbiology》2000,73(2-3):137-157
Three regions of the classical swine fever virus (CSFV) genome that have been widely sequenced were compared with respect to their ability to discriminate between isolates and to segregate viruses into genetic groups. Sequence data-sets were assembled for 55 CSFVs comprising 150 nucleotides of the 5' non-translated region, 190 nucleotides of the E2 envelope glycoprotein gene and 409 nucleotides of the NS5B polymerase gene. Phylogenetic analysis of each data-set revealed similar groups and subgroups. For closely related viruses, the more variable or larger data-sets gave better discrimination, and the most reliable classification was obtained with sequence data from the NS5B region. No evidence was found for intertypic recombination between CSFVs. A larger data-set was also analysed comprising 190 nucleotides of E2 sequence from 100 CSFVs from different parts of the world, in order to assess the extent and global distribution of CSFV diversity. Additional groups of CSFV are evident from Asia and the nomenclature of Lowings et al. (1996) [Lowings, P., Ibata, G., Needham, J., Paton, D., 1996. J. Gen. Virol. 77, 1311-1321] needs to be updated to accommodate these. A tentative assignment, adapting rather than overturning the previous nomenclature divides CSF viruses into three groups with three or four subgroups: 1.1, 1.2, 1.3; 2.1, 2.2, 2.3; 3.1, 3.2, 3.3, 3.4. The expanding data-base of CSFV sequences should improve the prospects of disease tracing in the future, and provide a basis for a standardised approach to ensure that results from different laboratories are comparable. 相似文献
950.
Reichel CL Grant AL Everett RS Bidwell CA Gerrard DE 《Domestic animal endocrinology》2000,18(3):337-348
Development of a recombinant insulin like growth factor I (IGF-I) that is distinguishable from its endogenous counterpart would provide a powerful tool for delineating the role of IGF in myogenesis. Therefore, the objective of this study was to create an epitope-tagged IGF-I that retains biological activity and determine whether expression of this construct is possible in muscle tissue following direct DNA injection. Expression vectors were created that encoded porcine IGF-I containing a T7 (11-amino acid) epitope-tag (TIGF). Immunoreactivity of the purified recombinant TIGF was confirmed using monoclonal antibodies. Biological activity was evaluated by examining differentiation of myoblasts cultured with TIGF or transfected with TIGF plasmid DNA. Addition of purified TIGF to myoblast cultures stimulated (P < 0.05) muscle creatine kinase levels similar to insulin (10(-5) M). Likewise, transfection of L6A1 with TIGF DNA hastened (P < 0.01) differentiation compared to control pcDNA-transfected myoblasts. The integrity of the recombinant protein was confirmed using a sandwich-configured enzyme linked immunosorbent assay. Finally, recombinant TIGF DNA was injected in porcine muscle and the ability to detect TIGF protein was evaluated. TIGF expression was detected in muscle fibers of injected porcine muscle. These data show that a T7 amino acid tag placed on the amino terminus of the IGF-I protein remains intact during processing and does not interfere with the biological activity of the molecule. Use of this DNA construct is an excellent tool for investigating the role of IGFs in control muscle development and provides a model to investigate other regulators of animal growth. 相似文献