全文获取类型
收费全文 | 5768篇 |
免费 | 241篇 |
国内免费 | 8篇 |
专业分类
林业 | 492篇 |
农学 | 209篇 |
基础科学 | 52篇 |
1343篇 | |
综合类 | 739篇 |
农作物 | 273篇 |
水产渔业 | 365篇 |
畜牧兽医 | 1928篇 |
园艺 | 176篇 |
植物保护 | 440篇 |
出版年
2023年 | 28篇 |
2022年 | 57篇 |
2021年 | 103篇 |
2020年 | 115篇 |
2019年 | 140篇 |
2018年 | 107篇 |
2017年 | 128篇 |
2016年 | 132篇 |
2015年 | 99篇 |
2014年 | 158篇 |
2013年 | 271篇 |
2012年 | 330篇 |
2011年 | 404篇 |
2010年 | 254篇 |
2009年 | 205篇 |
2008年 | 347篇 |
2007年 | 349篇 |
2006年 | 362篇 |
2005年 | 373篇 |
2004年 | 322篇 |
2003年 | 297篇 |
2002年 | 310篇 |
2001年 | 77篇 |
2000年 | 72篇 |
1999年 | 86篇 |
1998年 | 66篇 |
1997年 | 54篇 |
1996年 | 55篇 |
1995年 | 45篇 |
1994年 | 29篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 35篇 |
1990年 | 39篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 35篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1974年 | 16篇 |
1973年 | 18篇 |
1972年 | 14篇 |
排序方式: 共有6017条查询结果,搜索用时 15 毫秒
11.
12.
Bersenas AM Mathews KA Allen DG Conlon PD 《American journal of veterinary research》2005,66(3):425-431
OBJECTIVE: To identify the normal gastric acid secretion profile in dogs and determine the degree of gastric acid suppression associated with 4 gastric acid suppressants. ANIMALS: 12 healthy Beagles. PROCEDURE: Intragastric pH was measured continuously for 24-hour periods with a digital recording system placed via a gastrostomy tube. Baseline measurements were obtained when food was withheld and when dogs were fed a standard diet. Dogs were then treated with ranitidine (2 mg/kg, IV, q 12 h), famotidine (0.5 mg/kg, IV, q 12 h), pantoprazole (1 mg/kg, IV, q 24 h), omeprazole (1 mg/kg, PO, q 24 h), or saline solution for 7 days; intragastric pH was recorded on days 0, 2, and 6. Subsequently, the effects of administering famotidine (0.5 mg/kg, IV, q 8 h; 6 dogs) and omeprazole as a suspension (1 mg/kg, PO, q 12 h; 6 dogs) were evaluated. Median 24-hour intragastric pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were determined. RESULTS: Median pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were all significantly higher when food was withheld than when dogs were fed. Famotidine, pantoprazole, and omeprazole significantly suppressed gastric acid secretion, compared with saline solution, as determined on the basis of median 24-hour pH and percentages of time pH was > or = 3 or > or = 4. However, ranitidine did not. Omeprazole suspension suppressed gastric acid secretion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in healthy dogs, famotidine, pantoprazole, and omeprazole significantly suppress gastric acid secretion. Twice daily administration of a suspension of omeprazole, was the only regimen tested that approached the potential therapeutic efficacy for acid-related disease when assessed by criteria used for human patients. 相似文献
13.
14.
The aim of this investigation was, through a meta-analysis, to review the published literature concerning the effect of PCV2 vaccination on the average daily weight gain (ADG) and on the mortality rate in pigs from weaning to slaughter. The review was restricted to studies investigating the effect of vaccines against PCV2 published from 2006 to 2008, identified using computerised literature databases. Only studies that met the following criteria were included: commercial vaccines were used, pigs or pens were assigned randomly to vaccination versus control groups in herds naturally infected with PCV2, and vaccinated and non-vaccinated pigs were housed together. Furthermore, it was a requirement that sample size, age at vaccination, and production period were stated. The levels of ADG and mortality rate had to be comparable to those seen in modern intensive swine production. In total, 107 studies were identified; 70 were excluded because they did not fulfil the inclusion criteria and 13 were identical to results published elsewhere. A significant effect of PCV2 vaccination on ADG was found for pigs in all production phases. The largest increase in ADG was found for finishing pigs (41.5g) and nursery-finishing pigs (33.6g) with only 10.6g increase in the nursery pigs. Mortality rate was significantly reduced for finishing pigs (4.4%) and nursery-finishing pigs (5.4%), but not for nursery pigs (0.25%). Herds negative for PRRS had a significantly larger increase in ADG compared to herds positive for PRRS. The PRRS status had no effect on mortality rate. 相似文献
15.
Peter Irwin 《Australian veterinary journal》1994,71(4):128-128
Veterinary Virology, 2nd edition, FJ Fenner, EPJ Gibbs, FA
Murphy, R Roitt, MJ Studded and DO White, Russia. 相似文献
Murphy, R Roitt, MJ Studded and DO White, Russia. 相似文献
16.
A three-year-old, male, entire, Yorkshire terrier was presented with peracute onset of abdominal pain and vomitus. Clinicopathological abnormalities included severely increased serum lipase activity, immeasurably high serum trypsin-like immunoreactivity and mild hypocalcaemia. Canine pancreatic lipase immunoreactivity (cPLI) was intended to be measured, however, the sample got lost. Ultrasonography revealed a hypoechoic pancreas with small amounts of peripancreatic fluid and hyperechogenic mesentery. Acute pancreatitis (AP) was diagnosed and the dog recovered with appropriate therapy within 48 hours. Clomipramine, a selective serotonin reuptake inhibitor (SSRI) for alleviating signs of separation anxiety had been given for seven weeks. Two similar, albeit less severe, episodes associated with previous courses of clomipramine had occurred eight months earlier that responded to discontinuing clomipramine and supportive care. As SSRIs are associated with AP in human beings and no other trigger could be identified, we conclude that clomipramine should be considered as a potential cause when investigating causes for AP in susceptible breeds or other dogs presenting with compatible clinical signs. 相似文献
17.
18.
19.
Peter D. Constable BSc Phd Robert N. Streeter Gerard J. Koenig Nigel R. Perkins Hani M. Gohar Dawn E. Morin 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1997,11(2):71-79
The objectives of this study were to investigate the determinants of the anion gap (AG) in cattle and to evaluate the utility of AG in detecting hyperlactatemia in sick neonatal calves and adult cattle. The AG was calculated as AG = ([Na+] + [K+]) - ([Cl-] + [HCO3]), with all values in mEq/L. The AG of healthy neonatal calves (n = 16) was 29.6 ± 6.2 mEq/L (mean ± SD), and the blood L-lactate concentration ranged from 0.5 to 1.2 mM/L. The AG was significantly (P > .05) correlated with serum phosphate (r = .66) and creatinine (r = .51) concentrations. The AG of neonatal calves with experimentally induced diarrhea (n = 16) was 28.6 ± 5.6 mEq/L, and the blood L-lactate concentration ranged from 1.1 to 2.9 mM/L. The AG was significantly correlated with blood L-lactate concentration (r = .67), serum phosphate concentration (r = .63), creatinine concentration (r = .76), and blood pH (r = -.61). The AG of adult cattle with abomasal volvulus (n = 41) was 20.5 ± 7.8 mEq/L, and the blood L-lactate concentration ranged from 0.6 to 15.6 mM/L. The AG was significantly correlated with blood L-lactate concentration (r = .60), serum phosphate concentration (r = .71), creatinine concentration (r = .65), albumin concentration (r = .47), total protein concentration (r = .54), blood pyruvate concentration (r = .67), and blood pH (r = -.41) but not plasma β-OH butyrate concentration. The results indicate that the AG in cattle is only moderately correlated with blood L-lactate concentration and is similarly correlated with serum phosphate and creatinine concentrations in neonatal calves and adult cattle, as well as with serum albumin and total protein concentrations in adult cattle. Anion gap determination is of limited usefulness in predicting blood L-lactate concentration in sick cattle, whereas the correlation between AG and serum creatinine concentration in sick cattle suggests that an increased AG should alert the clinician to the potential presence of uremic anions. 相似文献
20.