全文获取类型
收费全文 | 395篇 |
免费 | 20篇 |
专业分类
林业 | 5篇 |
农学 | 7篇 |
基础科学 | 2篇 |
37篇 | |
综合类 | 93篇 |
农作物 | 42篇 |
水产渔业 | 6篇 |
畜牧兽医 | 207篇 |
园艺 | 6篇 |
植物保护 | 10篇 |
出版年
2018年 | 6篇 |
2017年 | 4篇 |
2014年 | 8篇 |
2013年 | 15篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 14篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 12篇 |
1970年 | 10篇 |
1969年 | 7篇 |
1967年 | 3篇 |
1966年 | 5篇 |
1960年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有415条查询结果,搜索用时 15 毫秒
21.
The pathology of Johne''s disease in sheep 总被引:4,自引:0,他引:4
The clinical, gross and histopathological findings in 50 sheep affected with Johne's disease are described. Clinically 90% were emaciated and 20% showed severe diarrhoea. On necropsy there was thickening of the walls of the intestines, particularly of the ileum, caecum and less frequently the jejunum, but in 36% of sheep the changes were only mild. Histologically there was a granulomatous enteritis, typhlitis and colitis, with the most severe changes in the terminal ileum. High numbers of acid-fast organisms were present in the terminal ileum in over 70% of sheep. Mycobacterium paratuberculosis was cultured from only 8% of the sheep examined. 相似文献
22.
23.
Absorption of calcium fumarate salts is equivalent to other calcium salts when measured in the rat model 总被引:3,自引:0,他引:3
Weaver CM Martin BR Costa NM Saleeb FZ Huth PJ 《Journal of agricultural and food chemistry》2002,50(17):4974-4975
Calcium absorption from fumarate salts (calcium fumarate and calcium malate fumarate), which have recently been considered for use as sources for food and beverage enrichment, was compared to that from calcium citrate malate, calcium citrate, and calcium carbonate. Salts were instrinsically labeled with 45Ca and orally administered to Sprague-Dawley rats. Fractional absorption of calcium from each salt was determined using the femur uptake model. Fractional absorption from the five salts (0.30-0.27) was not significantly different (p > 0.05). Thus, when measured in the rat model, calcium from calcium fumarate and calcium malate fumarate is absorbed equally well as compared to other salts, which are common calcium sources in many foods, beverages, and supplements. 相似文献
24.
Summary Clovers are widely used forage legumes on acidic soils in Texas and need inoculation with appropriate rhizobia when first introduced. Acidic soils are not conducive to survival of clover rhizobia. A survey of pastures was undertaken to determine the number of rhizobia present. The effect of liming acidic soils on the survival of clover rhizobia was also evaluated in the laboratory. The number of clover rhizobia was more than 100 cells g-1 soil in 70% of the pastures surveyed but populations within pastures varied by more than two orders of magnitude. The number of years of clover production beyond 1 year did not affect the rhizobial population density. The soil pH of twelve samples was below 5.0 and six samples had populations of rhizobial lower than 100 g-1 soil. Eleven out of sixteen samples from fields that had grown clover and had pH values above 6.0 had populations exceeding 1000 g-1 soil and only three samples had populations lower than 100 g-1 soil. Incubating indigenous or inoculated rhizobia in well-mixed soils having pH values of 5.1 or below resulted in populations declining to below 10 g-1 soil in 6 weeks. Mixing of soils with pH values of up to 5.4 induced reduction of rhizobial numbers, possibly by destroying microsites. Liming of soils to increase pH values above 5.5 improved survival of native or inoculated rhizobia in most cases. 相似文献
25.
Zafar TA Weaver CM Jones K Moore DR Barnes S 《Journal of agricultural and food chemistry》2004,52(10):2827-2831
The effect of inulin on isoflavone absorption and the effect of isoflavones and synergy with inulin on calcium absorption in rats was investigated. Rats (n = 48) were divided into three groups and fed inulin (50 mg/g), isoflavone (8 mg/g) or inulin + isoflavone (50 mg/g + 8 mg/g) diets for 21 days. After a 2-h fast, rats were given (45)Ca orally or intraperitoneally, together with 25 mg of calcium as calcium acetate. Blood and femurs were collected 4 days later. Sera were analyzed for isoflavones using HPLC-MS, femurs for (45)Ca by beta-scintillation counting, and total femoral calcium by atomic absorption spectroscopy. Both groups fed isoflavones had similar and significantly higher weight-adjusted total femoral calcium content compared to the inulin-fed group (p < 0.0001). (45)Ca absorption was significantly higher (p < 0.01) when isoflavones were added to the diet, and serum equol was significantly lower (p < 0.01) when inulin was added to the diet containing isoflavones. We conclude that isoflavones enhance calcium absorption, without synergy from inulin, and that inulin decreases equol production. 相似文献
26.
Simonne AH Smith M Weaver DB Vail T Barnes S Wei CI 《Journal of agricultural and food chemistry》2000,48(12):6061-6069
Isoflavones and carotenoids in four experimental genotypes and Hutcheson cultivar soybeans were evaluated as a function of processing treatments and maturity. Total isoflavone and carotenoid contents were affected by genotypes and maturity stages (p < 0.0001). Total isoflavones ranged from 472 microg/g (in NTCPR93-40) to 2280 microg/g (in Hutcheson). Lutein contents ranged from 895 (in NTCPR93-286) to 2119 (in Honey Brown), and beta-carotene ranged from 291 (in Hutcheson) to 491 (in NICPR92-40) microg/100 g. Mean total isoflavone retention percentages in immature Hutcheson soybeans were 46% (boiling), 53% (freezing), and 40% (freeze-drying). Mean retentions of lutein and beta-carotene, respectively, were 92 and 73% in frozen, 62 and 62% in boiled, and 34 and 27% in freeze-dried soybeans. Boiling caused a substantial increase in daidzin, genistin, and genistein. The results show that post-harvest changes in total isoflavones and carotenoids in soybeans are influenced by processing methods, but genotype has an effect on isoflavone and carotenoid profiles during seed development. 相似文献
27.
28.
Overlayer structures can be formed on surfaces by the deposition of clusters containing hundreds or thousands of atoms. Cluster assembly alters the reaction pathway at the surface so that novel structures with unique chemical and physical properties can be stabilized. This article discusses the process of cluster assembly. Cluster-assembled interfaces are compared to those obtained by conventional techniques, and examples are given for metal-semiconductor and semiconductor-high temperature superconductor systems. 相似文献
29.
Grundy WM Buratti BJ Cheng AF Emery JP Lunsford A McKinnon WB Moore JM Newman SF Olkin CB Reuter DC Schenk PM Spencer JR Stern SA Throop HB Weaver HA;New Horizons Team 《Science (New York, N.Y.)》2007,318(5848):234-237
The New Horizons spacecraft observed Jupiter's icy satellites Europa and Ganymede during its flyby in February and March 2007 at visible and infrared wavelengths. Infrared spectral images map H2O ice absorption and hydrated contaminants, bolstering the case for an exogenous source of Europa's "non-ice" surface material and filling large gaps in compositional maps of Ganymede's Jupiter-facing hemisphere. Visual wavelength images of Europa extend knowledge of its global pattern of arcuate troughs and show that its surface scatters light more isotropically than other icy satellites. 相似文献
30.
Bockelée-Morvan D Biver N Moreno R Colom P Crovisier J Gérard E Henry F Lis DC Matthews H Weaver HA Womack M Festou MC 《Science (New York, N.Y.)》2001,292(5520):1339-1343
The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (=30-centimeter radius) was comparable to the mass in the large fragments seen in optical images. The mass budget after breakup suggests a small nucleus ( approximately 100- to 300-meter radius) that had been losing debris for weeks. The HNC, H2CO, H2S, and CS abundances relative to H2O measured during breakup are consistent with those obtained in other comets. However, a deficiency in CH3OH and CO is observed. 相似文献