全文获取类型
收费全文 | 116925篇 |
免费 | 6260篇 |
国内免费 | 122篇 |
专业分类
林业 | 4854篇 |
农学 | 3681篇 |
基础科学 | 831篇 |
13338篇 | |
综合类 | 21917篇 |
农作物 | 4675篇 |
水产渔业 | 5495篇 |
畜牧兽医 | 60085篇 |
园艺 | 1402篇 |
植物保护 | 7029篇 |
出版年
2018年 | 1497篇 |
2017年 | 1613篇 |
2016年 | 1562篇 |
2015年 | 1346篇 |
2014年 | 1515篇 |
2013年 | 4404篇 |
2012年 | 2929篇 |
2011年 | 3626篇 |
2010年 | 2445篇 |
2009年 | 2392篇 |
2008年 | 3647篇 |
2007年 | 3419篇 |
2006年 | 3187篇 |
2005年 | 3052篇 |
2004年 | 3047篇 |
2003年 | 3042篇 |
2002年 | 2910篇 |
2001年 | 3879篇 |
2000年 | 3879篇 |
1999年 | 2929篇 |
1998年 | 1208篇 |
1997年 | 1208篇 |
1995年 | 1369篇 |
1994年 | 1294篇 |
1993年 | 1220篇 |
1992年 | 2626篇 |
1991年 | 2823篇 |
1990年 | 2676篇 |
1989年 | 2710篇 |
1988年 | 2490篇 |
1987年 | 2602篇 |
1986年 | 2672篇 |
1985年 | 2550篇 |
1984年 | 2055篇 |
1983年 | 1892篇 |
1982年 | 1237篇 |
1981年 | 1186篇 |
1980年 | 1090篇 |
1979年 | 1877篇 |
1978年 | 1508篇 |
1977年 | 1208篇 |
1976年 | 1173篇 |
1975年 | 1219篇 |
1974年 | 1576篇 |
1973年 | 1653篇 |
1972年 | 1631篇 |
1971年 | 1567篇 |
1970年 | 1451篇 |
1969年 | 1319篇 |
1967年 | 1136篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Meat regulations also involve game inspection. This publication deals with the regulations concerning furred game intended for slaughter and furred game hunted for food. 相似文献
72.
R D Park 《Veterinary Clinics of North America: Equine Practice》1989,5(1):47-66
A complete radiographic examination of the equine foot consists of properly exposed, processed, and positioned radiographs. For radiographic interpretation, in addition to knowing radiographic signs of disease, a knowledge of normal radiographic anatomy and possible insignificant anatomic variations is necessary. 相似文献
73.
K Okada A Yamaguchi K Ohshima S Numakunai H Itoh Y Seimiya H Koyama 《Veterinary pathology》1989,26(2):136-143
Biopsies of skin from a 2-year-old heifer with spontaneously regressing dermal leukosis were examined. The heifer was not infected with bovine leukemia virus and was negative for tumor-associated antigens of enzootic bovine lymphosarcoma. By hematological standards for bovine leukemia, the heifer was positive at about 60 days post-occurrence of the disease (POD). At 53 days POD, lymphoblastic neoplastic cells in the dermis reacted with anti-T lymphocyte monoclonal antibody by the avidin biotin peroxidase complex method. The cells had intracytoplasmic clustered dense bodies under electron microscopy. From 53 to 83 days POD, figures of the transepithelial elimination (TE) against neoplastic cells and perivascular infiltration of small lymphocytes were in the dermis. Small lymphocytes reacted with anti-T lymphocyte monoclonal antibody. At necropsy there were no neoplastic lesions; there were flat lymph node-like tissues in the subcutis. Many germinal centers were seen in the lymphatic organs. Blood lymphocytes at 46 days POD were stimulated by phytohemagglutinin-P and concanavalin A. Sera, taken until 75 days POD and at necropsy, showed an inhibitory effect on mitogen-induced blastogenesis of normal bovine lymphocytes. These results suggested the existence of a spontaneous regressive mechanism against neoplastic lesions by TE and tumor immunity. 相似文献
74.
Y Zhou V Moennig C O Coulibaly J Dahle B Liess 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(1):76-80
Monoclonal antibodies against hog cholera and bovine viral diarrhoea viruses were assayed on organ tissue sections of experimentally infected animals. The animals had been infected simultaneously with both viruses. The antibodies were tested using an indirect immunofluorescence test and an indirect enzyme immunoassay with a biotin/streptavidin/peroxidase detection system. A polyclonal hyperimmune serum was used as a control in direct immunofluorescence tests. Both techniques based on monoclonal antibodies were more sensitive and more specific than the conventional test, the enzyme immunoassay being more sensitive than the immunofluorescence test. Small amounts of BVD viral antigen were demonstrable with monoclonal antibodies in most organ tissues. 相似文献
75.
Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals. 相似文献
76.
T R Thedford L W Johnson 《Veterinary Clinics of North America: Food Animal Practice》1989,5(1):145-157
Although there are notable infectious conditions that are capable of producing clinical disease in the NWC, overall, these species are quite healthy. Of the bacterial diseases, enterotoxemia caused by Clostridium perfringens types C and D would be deemed the most significant in North America, while type A also would be regarded as important in South America. Other important bacterial infections of potential concern are tuberculosis, Johne's disease, anthrax, malignant edema, actinomycosis, tetanus, and the South American condition referred to as alpaca fever, which, to date, has not been observed in North America. Fungal infections include classical ringworm, principally caused by Trichophyton spp., and the cases of coccidioidomycosis that are associated with the arid desert lands of the southwestern United States. Most notable of naturally occurring viral infections in the NWC would be rabies, ecthyma, and a recently described blindness neuropathy that has been associated with the equine herpesvirus I. NWC can be infected experimentally with agents causing hoof-and-mouth disease and vesicular stomatitis, but naturally occurring cases do not seem to occur. Serological evidence of exposure to many viral agents, including blue tongue, parainfluenza 3, bovine respiratory syncytial virus, bovine herpesvirus I, bovine viral diarrhea, influenza A, and rotavirus, has been demonstrated; however, no clinical disease associated with these agents, as yet, is apparent. 相似文献
77.
W Ahne J R Winton T Kimura 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(8):561-567
Infectious diseases remain one of the most important limitations to the successful propagation of aquatic animals. Most of the losses caused by pathogens in aquaculture could be prevented by health inspection, adequate environment and sound management practices. Effective control measures, mainly based upon 1) avoidance of pathogens 2) modification of the environment 3) improvement of host resistance 4) vaccination and 5) chemoprophylaxis are described. 相似文献
78.
A survey of the potential use of synthetic oligopeptides in the field of virology is given. The potential value of synthetic peptides as vaccines and diagnostic antigens is discussed. The advantages compared to conventional vaccines as well as the limitations, e.g. the poor efficiency of immune response, are described. 相似文献
79.
Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil (tillage) transport coefficient. It is argued here that this is counter-intuitive and causes significant problems in modelling tillage erosion in areas of complex terrain. This article examines whether a re-modelling of tillage erosion is possible that separates tillage direction (an interaction with the landform) from the soil transport coefficient (a measure of tillage intensity representing the combination of implement erosivity and soil erodibility). Experimental data for mouldboard ploughing upslope, downslope and cross-slope at Coombe Barton Farm, Devon are examined. Integration of data for all directions into a single relationship, which relates translocation in the direction of tillage to slope in the direction of tillage and translocation perpendicular to tillage to slope perpendicular to tillage, is not possible using previously published methods of analysis. However, when total translocation distance is regressed against the tangent of the slope at 45° to the tillage direction (bisecting the tillage direction and the direction of overturning) it is found that a single relationship can be used to describe tillage in all three directions. Therefore, this relationship is used to determine a single value of the soil transport coefficient ( k fTa ) for constant soil and implement conditions but different tillage directions. This redefinition of tillage is important both for true estimation of tillage erosion severity, the adirectional coefficient being 40% larger than the directional coefficient, and for modelling of tillage erosion in complex terrain. These improvements are vital when tillage erosion simulation is used to direct soil conservation strategies. 相似文献
80.