全文获取类型
收费全文 | 127912篇 |
免费 | 6280篇 |
国内免费 | 60篇 |
专业分类
林业 | 5145篇 |
农学 | 3668篇 |
基础科学 | 856篇 |
15412篇 | |
综合类 | 23702篇 |
农作物 | 5149篇 |
水产渔业 | 5489篇 |
畜牧兽医 | 65886篇 |
园艺 | 1451篇 |
植物保护 | 7494篇 |
出版年
2018年 | 1656篇 |
2017年 | 1826篇 |
2016年 | 1713篇 |
2015年 | 1359篇 |
2014年 | 1686篇 |
2013年 | 4973篇 |
2012年 | 3206篇 |
2011年 | 4000篇 |
2010年 | 2707篇 |
2009年 | 2654篇 |
2008年 | 4008篇 |
2007年 | 3744篇 |
2006年 | 3456篇 |
2005年 | 3151篇 |
2004年 | 3271篇 |
2003年 | 3173篇 |
2002年 | 3056篇 |
2001年 | 3804篇 |
2000年 | 3818篇 |
1999年 | 2834篇 |
1998年 | 1252篇 |
1995年 | 1437篇 |
1994年 | 1330篇 |
1993年 | 1273篇 |
1992年 | 2624篇 |
1991年 | 2803篇 |
1990年 | 2745篇 |
1989年 | 2799篇 |
1988年 | 2508篇 |
1987年 | 2607篇 |
1986年 | 2730篇 |
1985年 | 2631篇 |
1984年 | 2152篇 |
1983年 | 1993篇 |
1982年 | 1312篇 |
1981年 | 1271篇 |
1979年 | 2137篇 |
1978年 | 1679篇 |
1977年 | 1421篇 |
1976年 | 1478篇 |
1975年 | 1538篇 |
1974年 | 1921篇 |
1973年 | 1961篇 |
1972年 | 1881篇 |
1971年 | 1742篇 |
1970年 | 1664篇 |
1969年 | 1587篇 |
1968年 | 1358篇 |
1967年 | 1444篇 |
1966年 | 1340篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
1. The aim of the present study was to investigate whether grain type (barley or oats) and ss-glucanase inclusion influence the performance and the gastrointestinal ecosystem of broiler chickens, taking the concentrations of short-chain fatty acids and lactic acid, pH, ileal viscosity, and the weight of the caeca and liver into consideration. 2. The inclusion of beta-glucanase in the oat-based diet improved body weight gains. Enzyme supplementation of barley-based diets improved feed conversion efficiency and reduced intestinal viscosity. 3. Irrespective of the type of cereal, beta-glucanase supplementation increased the lactic acid concentration and lowered the pH of the crop contents. No such changes in fermentation were observed in the contents of the gizzard and ileum. 4. Larger amounts of total dietary fibre and its fractions (arabinoxylans and beta-glucans) in oats decreased the weight of the caeca. 5. Molar ratios of acetate, propionate and butyrate in the caecal chyme were affected by cereal type but not by enzyme supplementation. The barley-based diet increased the butyrate:propionate ratio but the opposite effect was observed with the oat-based diet. 相似文献
972.
Phumoonna T Muscatello G Chicken C Gilkerson JR Browning GF Barton MD Heuzenroeder MW 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2006,53(3):126-132
A total of 227 field samples from naturally exposed foals aged between 3 weeks and 6 months were used in an evaluation of a peptide-based enzyme-linked immunosorbent assay (ELISA) for diagnosis of Rhodococcus equi infection. A biotinylated peptide derived from the virulence-associated protein A (VapA) of R. equi, a horse pathogen, was synthesized and designated as PN11-14. The peptide corresponds to the N-terminal B-cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein. Based upon a serum immunoglobulin (Ig)G titre of 512 as a positive cut-off value for the R. equi infection, the ELISA provided the overall sensitivity of 47.62%, specificity of 69.67% and an accuracy of 59.47% with a positive predictive value of 57.47% for true R. equi pneumonia. The assay was improved by detecting VapA-specific IgGb antibodies against N-terminal B-cell epitope of the VapA protein rather than IgG antibodies. The VapA-IgGb ELISA showed the overall sensitivity of 70.47%, specificity of 72.13% and accuracy of 71.36% with a positive predictive value of 68.52%. Diagnosis of R. equi disease in 6-week-old foals showed that the VapA-IgGb ELISA provided an increasing trend (P=0.0572) in sensitivity of 82.4% in comparison with the VapA-IgG ELISA which showed the sensitivity of 58.8%. However, differences in specificity of both tests were statistically insignificant (P=0.357) as analysed by the McNemar test. These results indicated that detection of VapA-specific IgGb antibodies may be a better predictor of R. equi disease in foals. 相似文献
973.
Surgical gloves were collected after 231 first opinion and referral surgical procedures performed at the University of Liverpool Small Animal Hospital. They were tested for defects by the water load test and the site of any defects was recorded; 10.2 per cent of the gloves had defects, and at least one glove became defective during 51 (22.1 per cent) of the surgical procedures. Significantly more defects occurred during orthopaedic procedures and the likelihood of a defect occurring increased with the duration of the surgical procedure. The majority (78 per cent) of the defects occurred in the gloves worn on the non-dominant hand and 64 per cent of them were in the index finger. The surgeon or assistant was aware of a glove being punctured in only 3.8 per cent of cases. 相似文献
974.
975.
976.
van Wuijckhuise L Dercksen D Muskens J de Bruijn J Scheepers M Vrouenraets R 《Tijdschrift voor diergeneeskunde》2006,131(18):649-654
For the first time Bluetongue (BT) has been diagnosed in the Netherlands. The clinical symptoms of BT on five farms during the first outbreak ever in the Netherlands are described. Fever and swollen sensitive coronets leading to reluctance to stand and walk were sometimes the first symptoms. Later lesions in the mouth occurred with foamy salivation and respiratory problems. In other cases a swollen head with swollen lips and foamy salivation were the first clinical signs. Also sudden death occurred. In the first sixteen confirmed cases morbidity and mortality were lower than described in outbreaks in other countries. Good collaboration between practitioners, specialists of the Animal Health Service (GD-Deventer), and specialists of the Food and Consumer Product Safety Authority (VWA) and CIDC-Lelystad (Wageningen UR) led to a rapid notification and ultimately confirmation of the suspected diagnosis BT. 相似文献
977.
Séguin MJ Friendship RM Kirkwood RN Zanella AJ Widowski TM 《Journal of animal science》2006,84(5):1227-1237
The objective of this study was to determine the effects of boar presence on aggression, shoulder scratches, and salivary cortisol in group-housed sows during the period after mixing, which is when dominance hierarchies are formed. A total of 225 York-shire sows were used. Five groups of 15 sows were each exposed to 1 of 3 levels of boar presence (n = 15): physical (boar in pen with sows; 2.15 m2 per sow), fenceline (boar housed adjacent to sows; 2.3 m2 per sow), or control (no boar in the room; 2.3 m2 per sow). The experiment was divided into 2 phases. In phase 1, behavioral measurements were taken for 48 h after mixing and boar introduction. In phase 2, behavioral measurements were taken beginning on d 6 after mixing and included 24 h before and 48 h after boar removal. In phases 1 and 2, shoulder scratches were scored 24 h before and 24 h after mixing and boar removal, respectively. Saliva samples were collected each morning (0600 to 0700) and afternoon (1600 to 1700) during both phases. Frequencies of intersow aggressive contact (bite, body knock, and head knock) and threats as well as frequencies and durations of fighting bouts were determined from video recordings during daily feeding (49.6 +/- 1.4 min) and nonfeeding (21 +/- 0.2 h) periods. During phase 1, boar presence did not affect the frequency of threats during either the feeding or nonfeeding periods. Control groups had fewer aggressive contacts at feeding during the 25- to 48-h period compared with the fenceline groups (P = 0.01). Total duration of fighting and average fighting bout duration were unaffected by treatment. However, the number of fights occurring during feeding 25 to 48 h postmixing was lower in the physical groups than in the fenceline groups (P = 0.023); measures for the control groups were intermediate. Physical sows also received fewer shoulder scratches postmixing than did control sows (P = 0.048). After mixing, physical sows showed greater morning (P = 0.08) and afternoon (6 h postmixing, P = 0.01; 32 h postmixing, P = 0.08) salivary cortisol concentrations compared with fenceline sows, although they were only numerically greater than those for control sows. During phase 2, removing the boar did not increase fighting among sows or affect shoulder scratches or salivary cortisol concentrations. The presence of a boar was minimally effective at reducing fighting and scratches during the postmixing period, and sows showed a greater stress response in the presence of a boar. 相似文献
978.
Sixteen boa constrictors (Boa constrictor), three royal pythons (Python regius) and 15 Burmese pythons (Python molurus bivittatus) were examined endoscopically by access through the air sac. The snakes were immobilised in a ventral position using a half-open anaesthetic system with assisted ventilation and a mixture of isoflurane and oxygen. The rigid endoscope was introduced percutaneously and the internal structure of the lungs and the air sac, and the shape, size and external surface of the liver were visible in the cranial direction. In the smaller snakes the bifurcation and caudal part of the trachea could be viewed, provided the endoscope was positioned in a retrograde orientation. The caudal orientation of the endoscope made it possible to view the gall bladder and the size, shape and surface of the spleen. In some cases, the pancreas and the surface of the stomach and colon could be monitored. Endoscopy through the air sac also made it possible to check the major veins in the coelom. The snakes were monitored for at least 30 days after the intervention and no changes in their respiratory function or general health were observed. 相似文献
979.
The effect of low grade chronic Fasciola hepatica infection on the concentration of plasma glutamate dehydrogenase (GD), gamma-glutamyl transpeptidase (gamma-GT) and aspartate aminotransferase (AST) was investigated in sheep dosed daily with three (AL3), eight (AL8) or 14 (AL14) metacercariae over 22 weeks or given a single dose of 200 metacercariae. Significant increases in plasma GD activity first occurred after nine, 12 and 23 weeks and in gamma-GT activity after 12, 24 and 32 weeks for groups AL14, AL8 and AL3 respectively. Changes in AST activity were not as clearly related to dose level. In sheep with single infection, both GD and gamma-GT were capable of detecting liver damage resulting from the migration of 10 or more flukes. Plasma GD and gamma-GT activities are more sensitive indicators of liver cell damage in chronic subclinical fascioliasis than AST activity and gamma-GT may be more suitable as a diagnostic aid on account of its greater stability. 相似文献
980.
N. W. Holfeld B. Schiefer B. R. Boycott 《The Canadian veterinary journal. La revue veterinaire canadienne》1980,21(4):103-105
Nine cases of granulomatous dermatitis in carnivores (eight dogs, one cat) are described. In three cases, in which there were no fungi in hair shafts, nor any other evidence of mycotic infection initially, fungal elements were demonstrated in the granulomas with the aid of special stains (PAS and Grocott). Granulomatous dermatitis in case of dermatophyte infections is thought to be an hypersensitivity reaction and has been reported to occur in a variety of mammals. It is suggested that pyogranulomatous skin reactions and trichogranulomas could be associated with dermatophytes and it is recommended to carry out further laboratory studies in order to detect fungi in such cases. 相似文献