全文获取类型
收费全文 | 226317篇 |
免费 | 12183篇 |
国内免费 | 892篇 |
专业分类
林业 | 9892篇 |
农学 | 7510篇 |
基础科学 | 1671篇 |
28590篇 | |
综合类 | 40758篇 |
农作物 | 8967篇 |
水产渔业 | 11124篇 |
畜牧兽医 | 112842篇 |
园艺 | 3249篇 |
植物保护 | 14789篇 |
出版年
2019年 | 2337篇 |
2018年 | 3291篇 |
2017年 | 3746篇 |
2016年 | 3435篇 |
2015年 | 3018篇 |
2014年 | 3690篇 |
2013年 | 8702篇 |
2012年 | 6855篇 |
2011年 | 8451篇 |
2010年 | 5684篇 |
2009年 | 5658篇 |
2008年 | 8191篇 |
2007年 | 7672篇 |
2006年 | 7189篇 |
2005年 | 6754篇 |
2004年 | 6395篇 |
2003年 | 6502篇 |
2002年 | 6017篇 |
2001年 | 6803篇 |
2000年 | 6823篇 |
1999年 | 5470篇 |
1998年 | 2472篇 |
1997年 | 2336篇 |
1996年 | 2190篇 |
1995年 | 2507篇 |
1994年 | 2275篇 |
1993年 | 2166篇 |
1992年 | 4395篇 |
1991年 | 4674篇 |
1990年 | 4613篇 |
1989年 | 4480篇 |
1988年 | 4152篇 |
1987年 | 4137篇 |
1986年 | 4229篇 |
1985年 | 4042篇 |
1984年 | 3413篇 |
1983年 | 3027篇 |
1982年 | 2025篇 |
1979年 | 3092篇 |
1978年 | 2521篇 |
1977年 | 2111篇 |
1976年 | 2151篇 |
1975年 | 2265篇 |
1974年 | 2705篇 |
1973年 | 2762篇 |
1972年 | 2631篇 |
1971年 | 2443篇 |
1970年 | 2377篇 |
1969年 | 2404篇 |
1967年 | 2078篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
K G Braund H S Steinberg A Shores J E Steiss J R Mehta M Toivio-Kinnucan K A Amling 《Journal of the American Veterinary Medical Association》1989,194(12):1735-1740
Six dogs with laryngeal paralysis had clinical, electrophysiologic, and pathologic evidence of a more generalized polyneuropathy. Three of the dogs were young Dalmatians, one was a young Bouvier des Flandres, and two were older, large-breed dogs. The results of this study suggest that laryngeal paralysis in dogs may frequently be one clinical sign of an underlying, more generalized polyneuropathy. Two forms of this generalized polyneuropathy may exist: an early form, as seen in young dogs with congenital or hereditary disease, and a delayed-onset form that is usually found in older dogs with so-called idiopathic laryngeal paralysis, some of which may have hypothyroidism. 相似文献
102.
DV COUSINS SN WILLIAMS R. REUTER† D. FORSHAW† B. CHADWICK§ D. COUGHRAN¶ P. COLLINS# N. GALES 《Australian veterinary journal》1993,70(3):92-97
SUMMARY Tuberculosis was diagnosed in 3 otariid seals found dead on beaches at 3 locations on the south coast of Western Australian between May 1990 and March 1991. This confirms that tuberculosis is present in the 2 native seals (Neophoca cinerea and Arctocephalus forsteri) in Western Australian waters. Mycobacterium sp isolated from the lungs of 2 of the seals were studied to determine the similarity of the strains to each other, to the strains isolated during 1986 from Australian sea lions and New Zealand fur seals kept in captivity at a marine park near Perth, Western Australia, and to a strain isolated in 1988 from a seal trainer who worked with the infected captive seals for 3 years. After restriction endonuclease analysis (REA) with the endonucleases Bst Ell, Bcl I and Pvu II, one of the wild seal strains appeared to have identical DNA fragment patterns to the strains from the captive seals and the seal trainer. The other wild seal isolate had identical REA profiles using Bst EII and Bcl I, but a minor difference was detected using Pvu II. Differences in these isolates were more clearly seen in restriction fragment length polymorphisms after hybridisation with two DNA probes. The secretory protein MPB70, present in M bovis, was not detected in wild seal isolates using sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blotting techniques. Analysis of protein and DNA fragment profiles indicated that seal tuberculosis isolates form a unique cluster within the M tuberculosis complex. 相似文献
103.
In this clinical study, a diaphragmatic peritoneo-pericardial hernia in an eight month-old Persian cat is reported. The diagnostic procedure is described, and the clinical symptoms and diagnostic possibilities are discussed. 相似文献
104.
105.
P. Banik 《Journal of Agronomy and Crop Science》1996,176(5):289-294
A field experiment was conducted during the winter season of 1992–93 and 1993–94 at Agricultural Experimental Farm, Giridih, Bihar to evaluate the intercropping systems of legumes, gram ( Cicer arietinum L.), pea ( Pisum sativum ) and lentil ( Lens culinaris ) with wheat ( Triticum aestivum ) in 1:1 and 2:1 'row replacement series'. Intercropping systems were assessed on the basis of new indices termed as actual yield loss (AYL) and intercropping advantage (IA). This paper highlights the comparative effectiveness of evaluating the intercropping systems through the existing intercropping indices like LER, RCC, aggressivity. The indices AYL and IA seem to be more appropriate particularly when per plant yield is considered. Intercropping reduced the yield of component crops compared with respective pure stands. Wheat + pea in 1:1 row replacement series gave the highest wheat yield equivalent value (3.02 t ha−1 ) followed by wheat + lentil (2.91 tha−1 ). When the actual sown proportion was considered wheat + lentil (1:1) resulted in maximum AYL (+0.610) and IA (+0.279) values. This treatment also gave the maximum monetary advantage (Rs 5985.45 ha−1 ). 相似文献
106.
Abstract. Leaching losses of nitrate-nitrogen were measured from a set of eight hydrologically isolated plots on a clay loam soil over the period from September 1987 to February 1990. Variable drainflow recovery from the plots hampered accurate estimation of nitrate loading, but results suggest that, when inorganic nitrogen fertilizer is applied up to the recommended amount, there is little influence of the amount applied on the amount leached. We did, however, observe the following effects on nitrate leaching: leguminous green manure incorporated in autumn increased leaching of nitrate-nitrogen by 10–15 kg per hectare during the winter; autumn cultivation caused some increase in leaching compared with no cultivation in one year; some systematic variations in nitrate leaching occurred between years and between plots, but were unrelated to treatments.
From the results we conclude that green manuring does not provide sufficient nitrogen for organically grown crops on this soil but contributes significantly to nitrate leaching, and that growing spring cereals, with the land remaining in stubble as long as possible in autumn, may be the best strategy to minimize nitrate leaching. 相似文献
From the results we conclude that green manuring does not provide sufficient nitrogen for organically grown crops on this soil but contributes significantly to nitrate leaching, and that growing spring cereals, with the land remaining in stubble as long as possible in autumn, may be the best strategy to minimize nitrate leaching. 相似文献
107.
L A Wyant 《Veterinary Clinics of North America: Equine Practice》2001,17(2):297-303
The Internet is a fast-growing technology that allows information (text as well as images) to be shared across the world in an instant. As computer systems, software, and Internet services become less expensive options, the world becomes more experienced and comfortable with these technologies. In the foreseeable future, equine veterinarians are likely to be better educated about diseases and treatments, better connected with specialists for consultations on difficult cases, able to respond to client communications more efficiently, able to accurately educate clients, and able to communicate with colleagues from across the country and the world. Additionally, there is likely to be a time when using the Internet and computers is profitable in all these ways as well as economically. Improving doctor-client relationships and patient care are goals for all veterinarians, and the Internet holds the technology to render these now and in the future. 相似文献
108.
109.
Jamie S. Harmon Kim G. Michelsen Dr. Mark A. Sheridan 《Fish physiology and biochemistry》1991,9(4):361-368
Trialcylglycerol (TG) lipase was isolated and partially purified from rainbow trout liver. Triacylglycerol lipase activity was assayed by measuring14C-oleic acid release from14C-triolein.14C-oleic acid release was linear for up to two hours. Optimal activity occurred at pH 7.0 and 15°C. Most of the lipase activity was recovered in the cytosolic fraction. A 27,000-fold purification was achieved after Sepharose (Bio-gel A 0.5 M, 200–400 mesh) chromatography of a resuspended 20% ammonium sulfate fraction. The molecular weight of the trout hepatic lipase as determined by size-exclusion chromatography and by SDS-polyacrylamide gel electrophoresis was 40–43 kD. Lipase-mediated hydrolysis of TG resulted in the production of diacylglycerols, monoacylglycerols, and fatty acids. Kinetic analysis indicated that Vmax=0.016 nmol/h/mg protein and that Km=0.28 mM triolein. Lipolytic activity was enhanced in the presence of cAMP/ATP-Mg2+. These results suggest that the liver of trout possesses a neutral TG lipase that is responsible for mobilizing stored TG and is catalytically activated by phosphorylation.A part of this work was presented at the Annual Meeting of the American Society of Zoologists, December 26–30, 1990, San Antonio, TX. 相似文献
110.
The technique of cystocentesis in dogs and cats was studied. The indications and contraindications of this method are discussed, using illustrations. 相似文献