全文获取类型
收费全文 | 62726篇 |
免费 | 2845篇 |
国内免费 | 43篇 |
专业分类
林业 | 2526篇 |
农学 | 1648篇 |
基础科学 | 429篇 |
6165篇 | |
综合类 | 14777篇 |
农作物 | 2479篇 |
水产渔业 | 2407篇 |
畜牧兽医 | 31103篇 |
园艺 | 659篇 |
植物保护 | 3421篇 |
出版年
2017年 | 555篇 |
2016年 | 541篇 |
2014年 | 548篇 |
2013年 | 1872篇 |
2012年 | 1208篇 |
2011年 | 1441篇 |
2010年 | 920篇 |
2009年 | 882篇 |
2008年 | 1433篇 |
2007年 | 1400篇 |
2006年 | 1384篇 |
2005年 | 1397篇 |
2004年 | 1335篇 |
2003年 | 1400篇 |
2002年 | 1362篇 |
2001年 | 1503篇 |
2000年 | 1480篇 |
1999年 | 1211篇 |
1998年 | 534篇 |
1997年 | 541篇 |
1995年 | 599篇 |
1994年 | 574篇 |
1993年 | 562篇 |
1992年 | 1311篇 |
1991年 | 1396篇 |
1990年 | 1452篇 |
1989年 | 1492篇 |
1988年 | 1402篇 |
1987年 | 1356篇 |
1986年 | 1401篇 |
1985年 | 1375篇 |
1984年 | 1150篇 |
1983年 | 1007篇 |
1982年 | 718篇 |
1981年 | 690篇 |
1980年 | 644篇 |
1979年 | 1127篇 |
1978年 | 916篇 |
1977年 | 820篇 |
1976年 | 770篇 |
1975年 | 860篇 |
1974年 | 1127篇 |
1973年 | 1063篇 |
1972年 | 1128篇 |
1971年 | 1081篇 |
1970年 | 1022篇 |
1969年 | 874篇 |
1968年 | 710篇 |
1967年 | 844篇 |
1966年 | 693篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
991.
Sibeko KP Collins NE Oosthuizen MC Troskie M Potgieter FT Coetzer JA Geysen D 《Veterinary parasitology》2011,181(2-4):120-130
Restriction fragment length polymorphism analysis of PCR products (PCR-RFLP) and sequencing of the variable region of the p104 and PIM genes was performed on samples obtained from South African T. parva parasites originating from cattle on farms with suspected theileriosis and from buffalo. p104 and PIM PCR-RFLP profiles similar to those of the T. parva Muguga stock, an isolate that causes ECF in Kenya, were obtained from three of seven cattle samples collected on a farm near Ladysmith in KwaZulu-Natal Province. Amino acid sequences of the p104 and PIM genes from two of these samples were almost identical to the T. parva Muguga p104 and PIM sequences. This result supports findings from a recent p67 study in which p67 alleles similar to those of the T. parva Muguga stock were identified from the same samples. While these results suggest the presence of a cattle-derived T. parva parasite, reports of cattle-to-cattle transmission could not be substantiated and ECF was not diagnosed on this farm. Although extensive diversity of p104 and PIM gene sequences from South African T. parva isolates was demonstrated, no sequences identical to known cattle-type p104 and PIM alleles were identified from any of the buffalo T. parva samples analyzed. 'Mixed' PIM alleles containing both cattle- and buffalo-type amino acid motifs were identified for the first time, and there appeared to be selection of cattle-type and 'mixed'-type PIM sequences in the cattle samples examined. 相似文献
992.
993.
Reasons for performing study: Assessing patients' quality of life (QOL) is a core part of clinical decision making. Various methodologies for assessing patients' QOL have been developed in human medicine and small animal veterinary disciplines. In contrast, the lack of aids for QOL assessment in equine veterinary practice leaves practitioners reliant on subjective assessments of QOL, which may be prone to avoidable errors. Objectives: This paper suggests pragmatic ways in which QOL may be enhanced, while remaining appropriate for the time, financial and owner‐based constraints within equine practice. Methods: Through interdisciplinary research, this paper identifies, adapts and applies insights from several areas of research and practical experience in order to develop an overarching approach to making QOL‐based decisions in clinical cases. Results: The paper identifies 6 steps involved in QOL‐based decision making and provides examples of how these steps may be practically applied. These include deciding what each clinician feels is important; deciding how to evaluate it, including taking owners' views into consideration; making decisions about each case and achieving the desired clinical outcomes. Conclusions: Practitioners can draw their own conclusions on how they may improve QOL assessment in practice and may usefully share these with colleagues. Reporting cases and sharing practical examples of QOL tools used on the ground are vital to the development of this field and appropriate methodologies. Potential relevance: Improvements in QOL assessment are relevant to all areas of equine veterinary practice, and several areas of research. Further research may develop QOL assessment in practice, but more important are the personal improvements that each practitioner may achieve. See also correspondence by Grove 相似文献
994.
W A Priester D G Goodman G H Theilen 《Journal of the American Veterinary Medical Association》1977,170(8):823-826
An aged Boxer dog had 9 distinct primary tumors: chemodectoma, osteosarcoma, bronchiolo-alveolar adenocarcinoma, interstitial cell tumor, seminoma, basal cell tumor, fibropapilloma, adrenal cortical adenoma, and pancreatic adenoma. From this report, as well as from other studies, it is clear that Boxers have special susceptibilities to a variety of tumors. Analysis of clinical data on canine tumors indicated that the risk of Boxers for multiple tumors is only slightly higher than all tumors, indicating little or no specific predisposition for multiple tumors. In Boxers, however, certain tumor types occurred more frequently as multiple primary tumors than would be expected by chance. 相似文献
995.
C D Van Houweling W B Bixler J R McDowell 《Journal of the American Veterinary Medical Association》1977,171(11):1153-1156
Chemical contamination of animal feeds and feed ingredients is of concern to the Food and Drug Administration. Contamination by industrial chemicals such as polychlorinated biphenyls and polybrominated biphenyls; heavy metals such as lead, cadmium, and mercury; and pesticides such as dieldrin and chlordane exemplify the problem in feeds and the resulting problem of tissue residues in human foods. 相似文献
996.
Use of the indirect fluorescent antibody (IFA) tests is described to detect antibodies to Theileria mutans and Babesia major in the sera of infected cattle. When antisera against T mutans and B major were tested against homologous antigens high antibody titres were recorded: when they were tested against each other or against Babesia divergens antigen insignificant titres (1/40 or less) were recorded. Thus the test was found to be species specific. Animals recovered from T mutans and B major infections retained significant levels of IFA titres for 22 and 11 months respectively. It is suggested that the IFA test could be used for field survey of the piroplasms of cattle in Britain. 相似文献
997.
L S Sammons R H Kenyon G T Burger W R Beisel C E Pedersen 《American journal of veterinary research》1977,38(6):907-910
Acid-base alterations and changes in other selected serum constituents (free fatty acids, triglycerides, cholesterol, copper, cortisol, alpha1-acid glycoprotein, haptoglobin, and albumin) were measured during a study of Rocky Mountain spotted fever in 16 male rhesus macaques. Blood samples were taken from nonanesthetized macaques conditioned to repeated handling. Arterial pH increased and PCO2 decreased during the febrile period. Free fatty acids, triglycerides, copper, cortisol, alpha1-acid glycoprotein, and haptoglobin increased, whereas albumin decreased during the disease. Significant changes were not observed in arterial PO2. Cholesterol remained unchanged. The increase in arterial pH and decrease in PaCO2 indicated that respiratory alkalosis was present in macaques acutely affected with Rocky Mountain spotted fever. 相似文献
998.
The oestrogen levels were assessed in 180 urine samples taken from 20 cows. The animals had received over 15 days 40 mg one-per-cent oily solution of chloromadinone acetate. The solution had been applied orally or by pour-on methods. The curves of oestrogen excretion were identical for both methods of application, both during and after completed administration. In other words, the effect obtainable from pour-on application is just as good as that obtainable from oral administration. 相似文献
999.
Neoplasms of Equidae 总被引:7,自引:0,他引:7
J P Sundberg T Burnstein E H Page W W Kirkham F R Robinson 《Journal of the American Veterinary Medical Association》1977,170(2):150-152
In a retrospective study of neoplasms in Equidae pre;ented to the Animal Disease Diagnostic Laboratory, Purdue University, from Jan 1, 1970, to Dec 31, 1974, data were compiled on numbers and anatomic sites of neoplasms as well as on age, sex, and breed of subjects from which the neoplasms were taken. During this 5-year period, 21 neoplasms were diagnosed from 687 equine necropsies (3.1%) and 215 from 635 biopsies (33.9%), totaling 236 neoplasms from 1,322 cases (17.9%). The most common neoplasms were sarcoids (43.6%) and squamous cell carcinomas (24.6%). Papillomas (5.5%), nerve sheath tumors (4.2%), melanomas (3.8%), lipomas (3.0%), granulosa cell tumors (2.5%), fibromas (2.1%), cholesteatomas (1.3%), and lymphosarcomas (1.3%) were less common. 相似文献
1000.