全文获取类型
收费全文 | 1204篇 |
免费 | 75篇 |
国内免费 | 1篇 |
专业分类
林业 | 225篇 |
农学 | 26篇 |
基础科学 | 10篇 |
182篇 | |
综合类 | 89篇 |
农作物 | 26篇 |
水产渔业 | 45篇 |
畜牧兽医 | 546篇 |
园艺 | 24篇 |
植物保护 | 107篇 |
出版年
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 8篇 |
2018年 | 28篇 |
2017年 | 31篇 |
2016年 | 42篇 |
2015年 | 22篇 |
2014年 | 30篇 |
2013年 | 59篇 |
2012年 | 70篇 |
2011年 | 64篇 |
2010年 | 43篇 |
2009年 | 21篇 |
2008年 | 46篇 |
2007年 | 50篇 |
2006年 | 49篇 |
2005年 | 41篇 |
2004年 | 43篇 |
2003年 | 36篇 |
2002年 | 40篇 |
2001年 | 18篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1992年 | 9篇 |
1991年 | 18篇 |
1990年 | 13篇 |
1989年 | 22篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 17篇 |
1972年 | 15篇 |
1971年 | 13篇 |
1970年 | 12篇 |
1969年 | 12篇 |
1968年 | 8篇 |
1967年 | 12篇 |
1931年 | 8篇 |
1930年 | 9篇 |
1929年 | 28篇 |
1926年 | 11篇 |
排序方式: 共有1280条查询结果,搜索用时 15 毫秒
121.
Marcin K. Widomski Steffen Beck Broichsitter Alexander Zink Heiner Fleige Rainer Horn Witold Stępniewski 《植物养料与土壤学杂志》2015,178(3):401-412
At the end of waste disposal in 2005, a temporary mineral system was constructed to cover the waste body of the municipal landfill in Rastorf (N Germany). The aim of this study was to evaluate the effectiveness of this temporary cover system in limiting the infiltration of surface water into the waste body. The numerical modeling for the hydrological year 2012 was performed in FEFLOW 6.0. The required input data for modeling were achieved by laboratory measurements of the saturated hydraulic conductivity and the water retention characteristics of the mineral layers. The assumed initial and boundary conditions were based on in‐situ measurements of matrix potential and volumetric water content at three different measuring points by tensiometers, FDR sensors and observed meteorological conditions. The model was applied according to Darcy's and Richards' equations for variably saturated flow. Our results allowed assessing the components of water balance for a temporary cover system, especially water seepage into the waste body. The correlation between the measured and modeled volumetric soil water content in the layered temporary cover system was observed (R2 = 0.56 to 0.90). Deviations between the measured and modeled values are superficially related to the soil´s heterogeneity. In conclusion, the measured and modeled water balance parameters indicate that the temporary coverage system remains effective in limiting the infiltration rate. However, our studies revealed that the calculated and measured water seepage exceeded the values allowable by the German regulations. Additional studies have to assess variations in the soil water characteristics caused by weather‐related wetting and drying cycles and influence of waste settlement changing the profile of slope. 相似文献
122.
123.
Pathogenesis of experimental combined infections with Isospora suis and rotavirus in conventional and gnotobiotic piglets 总被引:1,自引:0,他引:1
J Vítovec B Koudela M Kudweis J St?pánek B Smíd R Dvorák 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1991,38(3):215-226
51 gnotobiotic and 63 conventional, one-, or two-days-old piglets were divided into five groups and infected orally either with Isospora suis or rotavirus alone, or with both agents simultaneously or successively with alternative sequences and various intervals. 15 gnotobiotic and 10 conventional piglets served as controls. The development of small intestinal lesions after infection with I. suis was biphasic. The dominant alteration resulting from rotavirus infection was villus atrophy, considerably more pronounced and extensive in gnotobiotic than in conventional piglets. Synergistic action of I. suis and rotavirus was manifested both clinically, and morphologically. This action culminated at the time of the actual, or presumed development of merogony of I. suis, i.e. on DPI 3 to 5. The action develops only if the intestinal epithelium is damaged functionally and morphologically by a preceding rotavirus infection. It is concluded that the synergistic action is based on a competition of rotavirus and I. suis for mature, enzymatically active absorptive cells. 相似文献
124.
St 《Journal of pest science》1929,5(10):132
Ohne Zusammenfassung 相似文献
125.
G St Jean L R Bramlage P D Constable 《Journal of the American Veterinary Medical Association》1989,194(9):1309-1311
Repair of a comminuted fracture of the proximal portion of the radius and ulna in a 4-month-old llama was achieved by use of internal fixation. An 8-hole narrow dynamic compression plate was applied to the lateral aspect of the radius and a 7-hole narrow dynamic compression plate was applied to the cranial aspect of the radius. One year after surgery, the llama had a normal gait and the cosmetic appearance of the limb was excellent. 相似文献
126.
The activity of alkaline phosphatase (EC 3.1.3.1.) was studied in the small intestines of piglets infected with the coccidia Isospora suis on the first and fifth day of age. Alkaline phosphatase activity is reduced significantly the third to fourth day after infection (DAI) throughout the small intestine in piglets infected on the fifth day of age. Similar results were obtained in the piglets killed the eighth to tenth DAI which had also been infected on the fifth day of their age. Piglets infected the first day of age and killed on the 8th to 13th DAI exhibited no larger differences from the above-mentioned groups, but alkaline phosphatase activity was distributed more regularly all over the surface of the villi. The normal values, comparable with the controls, were not obtained within 13 days after infection (piglet age 14 days). 相似文献
127.
128.
Seven adult cows developed abomasal volvulus immediately following correction of left displacement by casting and rolling. Three cows were rolled to provide temporary relief from left displaced abomasum because of concurrent disease and 4 were rolled as the principal therapy for left displacement. In each animal surgical correction of abomasal volvulus was accomplished via right paralumbar fossa celiotomy and inclusion of an omentopexy during abdominal closure. Surgery was performed within 24 hours of casting and rolling. All 7 cows recovered after surgery and were reported to have satisfactory milk production and appetite 6 weeks later. 相似文献
129.
130.
The effect of two anti-inflammatory drugs on the development and persistence of clinical signs in cattle experimentally infected with bovine ephemeral fever (BEF) virus was investigated by their administration, either before or after the commencement of fever. A total of 16 cattle was given phenylbutazone sodium (PBZ). The drug prevented fever and other clinical signs in six cattle when given daily during the incubation period, and at 8-h intervals for 5 days when clinical disease might be expected. When treatment with PBZ was deferred until 2-4 h after the commencement of fever, the rectal temperature returned to normal within 4 h in four of six cattle and the development of other clinical signs was suppressed. Clinical signs of ephemeral fever occurred in four untreated cattle infected at the same time. Viraemia, the development of neutralizing antibodies (at 8-11 days), resistance to subsequent challenge with BEF virus, neutrophilia, lymphopenia and a rise in plasma fibrinogen occurred in all BEF-infected animals whether treated or untreated, despite different clinical appearances. The mean peak of plasma fibrinogen in the untreated cattle was 6.9 g l-1; 3.2 g l-1 when treated 2-4 h after fever developed and 3.8 g l-1 when treated from 18-h post-infection. BEF virus was isolated from leucocytes of each of the cattle, but the frequency of isolation was lower in the treated group. The results indicate that treatment with PBZ blocked the host response which produces the clinical signs and did not have an anti-viral effect. In a similar experiment, a long-acting anti-inflammatory drug, flunixin meglumine, failed to prevent BEF or to modify the clinical signs once they had developed, except for the rectal temperature which returned to normal within 2-4 h of the administration of the drug. The efficacy of this drug was not improved by increasing the dosage to two or three times the recommended level. 相似文献