全文获取类型
收费全文 | 340087篇 |
免费 | 18081篇 |
国内免费 | 689篇 |
专业分类
林业 | 25173篇 |
农学 | 14369篇 |
基础科学 | 3013篇 |
49135篇 | |
综合类 | 46533篇 |
农作物 | 17852篇 |
水产渔业 | 18919篇 |
畜牧兽医 | 150515篇 |
园艺 | 6639篇 |
植物保护 | 26709篇 |
出版年
2019年 | 3794篇 |
2018年 | 4660篇 |
2017年 | 5067篇 |
2016年 | 5260篇 |
2015年 | 4626篇 |
2014年 | 6028篇 |
2013年 | 16733篇 |
2012年 | 8864篇 |
2011年 | 11414篇 |
2010年 | 8512篇 |
2009年 | 8810篇 |
2008年 | 10680篇 |
2007年 | 9952篇 |
2006年 | 10175篇 |
2005年 | 9363篇 |
2004年 | 9198篇 |
2003年 | 9003篇 |
2002年 | 8300篇 |
2001年 | 9545篇 |
2000年 | 9176篇 |
1999年 | 7928篇 |
1998年 | 4478篇 |
1997年 | 4529篇 |
1996年 | 4247篇 |
1995年 | 4900篇 |
1994年 | 4368篇 |
1993年 | 4034篇 |
1992年 | 6391篇 |
1991年 | 6692篇 |
1990年 | 6610篇 |
1989年 | 6587篇 |
1988年 | 5969篇 |
1987年 | 6031篇 |
1986年 | 6008篇 |
1985年 | 6022篇 |
1984年 | 5289篇 |
1983年 | 4847篇 |
1982年 | 3668篇 |
1981年 | 3476篇 |
1980年 | 3381篇 |
1979年 | 4681篇 |
1978年 | 4003篇 |
1977年 | 3600篇 |
1976年 | 3324篇 |
1975年 | 3319篇 |
1974年 | 3915篇 |
1973年 | 4008篇 |
1972年 | 3703篇 |
1971年 | 3443篇 |
1970年 | 3386篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
321.
Y. SANTOS I. BANDIN S. NUÑEZ K. GRAVNINGEN A. E. TORANZO 《Journal of fish diseases》1991,14(3):407-411
Abstact. The potency of a whole-cell bacterin (WCB) and a toxoid enriched whole-cell vaccine (WCEB) administered intraperitoncally into rainbow trout, Oncorhynchus mykiss (Richardson), were compared. The most effective vaccine was further evaluated by bathing turbot, Scophthalmus maximus (L.). These vaccines were composed of three strains of V. anguillarun , of the serotypes 01 and 02. Both vaccines conferred the highest protection against strains of serotype 01 within 4 weeks. With the toxoid enriched vaccine giving the best results (77 RPS). When trout were revaccinated after 7 weeks with this vaccine, good protection was achieved against strains of serotypes 01 and 02. Interestingly, when the WCEB was administered by bath to turbot, acceptable levels of protection against strains of both serotypes were obtained after 4 weeks of immunization. 相似文献
322.
323.
324.
Polysaccharide-induced protection of carp, Cyprinus carpio L., against bacterial infection 总被引:5,自引:0,他引:5
Abstract. The efficacy of 10 polysaccharides (curdlan, inulin, krestin, laminaran, lentinan, levan, schizophylian, selerogiucan, yeast glucan and zymosan) to enhance protection of carp, Cyprinus carpio L., against bacterial infection was investigated. Carp were intraperitoneally injected with the polysaceharides (2–l0 mgkg-1 ) on days 1 and 4, and challenged with Edwardsiella tarda on day 7. Among the polysaccharides tested, lentinan, schizophyllan and scleroglucan, which are l,6-branchcd-β-l,3-glucans, significantly increased the survival rate. They also induced a protective effect against Aeromonas hydrophila at a dose of 5 mg kg-1 . The ability of the polysaccharides to activate the alternative complement pathway (ACP) was examined by incubating the polysaccharides with carp serum and measuring the residual ACP activity. At a final concentration of 0.l mgml-1 , l,6-branched-β-1,3-glucans greatly reduced (76–77%) the ACP activity. Therefore, it is suggested that the protective effect of the l,6-branched-β-1,3-glucans may be associated with the activation of ACP. 相似文献
325.
326.
S. A. BROWN J. D.JACOBSON S. M. HARTSFIELD 《Journal of veterinary pharmacology and therapeutics》1993,16(4):419-425
Brown, S.A., Jacobson, J.D., Hartsfield, S.M. Pharmacokinetics of midazolam administered concurrently with ketamine after intravenous bolus or infusion in dogs. J. vet. Pharmacol. Therap. 16 , 419–425. Midazolam, a water-soluble benzodiazepine tranquilizer, has been considered by some veterinary anaesthesiologists to be suitable as a combination anaesthetic agent when administered concurrently with ketamine because of its water solubility and miscibility with ketamine. However, the pharmacokinetics of midazolam have not been extensively described in the dog. Twelve clinically healthy mixed breed dogs (22.2–33.4 kg) were divided into two groups at random and were administered ketamine (10 mg/kg) and midazolam (0.5 mg/kg) either as an intravenous bolus over 30 s (group 1) or as an i.v. infusion in 0.9% NaCl (2 ml/kg) over 15 min. Blood samples were obtained immediately before the drugs were injected and periodically for 6 h afterwards. Serum concentrations were determined using gas chromatography with electron-capture detection. Serum concentrations were best described using a two-compartment open model and indicated a t½α of 1.8 min and t½β.p of 27.8 min after i.v. bolus, and t½α f 1–35 min and t½β of 31.6 min after i.v. infusion. The calculated pharmacokinetic coefficient B was significantly smaller after i.v. infusion (429 ± 244 ng/ml) than after i.v. bolus (888 ± 130 ng/ml, P = 0.004). Furthermore, AUC was significantly smaller after i.v. infusion (29 800 ±6120 ng/h/ml) than after i.v. bolus (42 500 ± 8460 ng/h/ml, P < 0.05), resulting in a larger ClB after i.v. infusion (17.4 ± 4.00 ml/min/kg than after i.v. bolus (12.1 ± 2.24 ml/min/kg, P < 0.05). No other pharmacokinetic value was significantly affected by rate of intravenous administration. 相似文献
327.
RICHARD G. HARVEY 《Veterinary dermatology》1993,4(4):175-179
Abstract— The physiology of essential fatty acid metabolism in the cat is reviewed. Emphasis is placed on those aspects of the n:6 and n:3 fatty acids, their metabolites and interactions, which relate primarily to the skin. The functional roles, if known, of the fatty acids are discussed. Recent clinical research into the use of essential fatty acid supplements in the management of feline dermatoses is presented. Current indications for the therapeutic supplementation with essential fatty acids are summarised. 相似文献
328.
Clifford R. Berry DVM Kathy N. Wright DVM Edward B. Breitschwerdt DVM Jerome M. Feldman MD 《Veterinary radiology & ultrasound》1993,34(1):52-55
A 13-year-old neutered female Yorkshire terrier presented with a history of progressive episodic weakness and disorientation of 4 months duration. Physical and neurologic examinations were normal at presentation. Abdominal ultrasound revealed a mass involving the right adrenal gland. Standard planar scintigraphy was performed at 4, 18, and 24 hours after intravenous injection 185 MBq (5mCi) of 123 I-labeled metaiodobenzylguanidine (123 I-MIBG). An area of focal intense uptake was identified in the area of the right adrenal gland. A pheochromocytoma was confirmed histologically after surgical excision. 相似文献
329.
Zheng Xiaoxian Liu Donglan College of Forest Resources Environment Beijing Forestry University Beijing P.R.China 《中国林学(英文版)》1996,(1)
该文探讨了不用编制削度表直接建立高精度立木干曲线的方法.当采用干曲线是3次多项式时,通常根据10分法测定树干各部位直径,用最小二乘法求出该方程式的参数.从数学角度,只要知道树干任意3个部位的直径,就可以用最小二乘法或联立方程式求解干曲线参数.本文以樟子松为例,探讨用树干哪3个部位直径拟合的干曲线最接近实际干曲线,为建立立木干曲线提供有效方法.利用9个部位半径(方法Ⅰ)和利用其中3个部位半径(方法Ⅱ,28种组合)分别拟合干曲线,结果表明方法Ⅱ的6种半径组合的精度良好,其中的3种组合,(r1.3,r0.3,r0.7),(r1.3,r0.4,r0.7)和(r1.3,r0.4,r0.8)是拟合现实干曲线的有效方法. 相似文献
330.
J Weikel 《Tier?rztliche Praxis》1991,19(6):596-598
This is the first report of the simultaneous occurrence of sheep pulmonary adenomatosis and lymphoid interstitial pneumonia (Maedi) in the same animal in the Federal Republic of Germany. Seven adult sheep of the Merino Landrace were tested by immunodiffusion-assay for antibodies against Maedi/Visna-virus. Five of them originating from three different flocks had a positive reaction. In all pulmonary foci, which were examined by light microscopy, we found proliferations of the alveolar epithelium and therefore made a diagnosis of pulmonary adenomatosis. The animals with antibodies against Maedi-virus were additionally affected by a non-purulent peribronchitis and interstitial pneumonia. The diagnostic difficulties in double infections like those reported here are discussed. Eradication is complicated by the unknown epidemiologic situation. 相似文献