全文获取类型
收费全文 | 70922篇 |
免费 | 3978篇 |
国内免费 | 34篇 |
专业分类
林业 | 3225篇 |
农学 | 2529篇 |
基础科学 | 478篇 |
8698篇 | |
综合类 | 11422篇 |
农作物 | 2607篇 |
水产渔业 | 3640篇 |
畜牧兽医 | 36660篇 |
园艺 | 907篇 |
植物保护 | 4768篇 |
出版年
2018年 | 1057篇 |
2017年 | 1131篇 |
2016年 | 1058篇 |
2015年 | 916篇 |
2014年 | 1140篇 |
2013年 | 2635篇 |
2012年 | 2058篇 |
2011年 | 2464篇 |
2010年 | 1688篇 |
2009年 | 1754篇 |
2008年 | 2592篇 |
2007年 | 2362篇 |
2006年 | 2326篇 |
2005年 | 2127篇 |
2004年 | 2194篇 |
2003年 | 2165篇 |
2002年 | 2036篇 |
2001年 | 2367篇 |
2000年 | 2375篇 |
1999年 | 1926篇 |
1998年 | 915篇 |
1997年 | 823篇 |
1996年 | 784篇 |
1995年 | 863篇 |
1994年 | 843篇 |
1993年 | 770篇 |
1992年 | 1523篇 |
1991年 | 1543篇 |
1990年 | 1662篇 |
1989年 | 1508篇 |
1988年 | 1450篇 |
1987年 | 1340篇 |
1986年 | 1384篇 |
1985年 | 1336篇 |
1984年 | 1128篇 |
1983年 | 1025篇 |
1982年 | 628篇 |
1979年 | 1005篇 |
1978年 | 795篇 |
1977年 | 717篇 |
1976年 | 676篇 |
1975年 | 719篇 |
1974年 | 766篇 |
1973年 | 830篇 |
1972年 | 805篇 |
1971年 | 748篇 |
1970年 | 729篇 |
1969年 | 744篇 |
1967年 | 658篇 |
1966年 | 631篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Twenty-four red deer hinds with their calves were released on to a newly established pure red clover sward and, 2 days later, red staining of the tail, perineum and hocks was observed. This was presumed to be of urinary origin. Observation of micturition showed that when urine was passed, it was a normal straw colour but it turned scarlet-red about 1 hour after exposure to air. Midstream urine remained the normal colour when held under a pure nitrogen atmosphere immediately after micturition, but it turned red when held in air in the dark, suggesting that the colour change was due to an oxidative rather than a photosensitive reaction. All deer grazing red clover were affected but this did not occur in deer grazing ryegrass/white clover swards. No adverse effects were observed in the deer grazing the red clover, and calf growth was significantly higher than on ryegrass/white clover, suggesting that the red urine had no effect on health or productivity. Blood and urine analyses showed no signs of haemolysis, haematuria or haemoglobinuria. Preliminary chemical analyses suggest that the compounds involved are not those found in the urine of sheep grazing oestrogenic clover. The nature of the compounds have yet to be determined. 相似文献
992.
A. Das S. Katole M. Choubey S. P. Gupta M. Saini V. Kumar D. Swarup 《Journal of animal physiology and animal nutrition》2013,97(1):80-90
A feeding trial was conducted to know the level of concentrates in the diet of Antelope cervicapra at which diet digestibility and mineral utilization were optimum. Fifteen blackbucks (25–33 kg BW) were distributed into three groups of five each. Fresh oat (Avena sativa) and berseem (Trifolium alexandrinum) fodders were offered ad libitum to all the animals. In addition, animals in groups II and III received concentrate mixture at the rate of 0.5 and 1% of BW, whereas animals in group I received no concentrates. As the level of concentrates increased, consumption of fodder decreased resulting in decreased consumption of neutral detergent fibre (NDFom), acid detergent fibre (ADFom), hemicellulose and cellulose. However, overall total dry matter (DM) and organic matter (OM) intake was not significantly different between the groups. Digestibility of DM, OM and gross energy (GE) increased while that of NDFom and ADFom decreased with increased level of concentrates in the diet. Intake of P, Zn, Cu and Mn increased with increased level of concentrate supplementation; however, consumption of Ca and Fe followed the reverse trend. Absorption of P and Zn increased with increased level of concentrate supplementation. Serum concentration of Zn increased when concentrate was supplemented at the rate of 0.5% BW beyond which there was no further improvement. Increasing the level of concentrates in the diet was resulted in increased serum glucose and cholesterol levels. Forage‐only diet was inadequate in supply of energy, P and zinc. Supplementation of concentrates at the rate of 0.5% BW was able to meet the requirement of these nutrients. Supplementation at the rate of 1% BW supplied energy and P in excess of requirement. It was concluded that the feeding of concentrates to the captive blackbuck fed forage‐based diets should be restricted to 0.5% of BW. 相似文献
993.
994.
Lipomatosis is an uncommon cause of colic. This case report details the pre‐ and intraoperative findings of a 9‐year‐old gelding, presented with acute abdominal pain. Exploratory laparotomy revealed a massive fatty infiltrate involving an extensive portion of the base and mid‐body of the caecum. To the authors' knowledge, this is the first report of an infiltrative lipomatous lesion of the equine caecum. 相似文献
995.
A. Tvarijonaviciute J.J. Ceron S.L. Holden V. Biourge P.J. Morris A.J. German 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2013,27(1):31-38
Background
Obesity is a common medical disorder in dogs, and can predispose to a number of diseases. Human obesity is a risk factor for the development and progression of chronic kidney disease.Objectives
To investigate the possible association of weight loss on plasma and renal biomarkers of kidney health.Animals
Thirty‐seven obese dogs that lost weight were included in the study.Methods
Prospective observational study. Three novel biomarkers of renal functional impairment, disease, or both (homocysteine, cystatin C, and clusterin), in addition to traditional markers of chronic renal failure (serum urea and creatinine, urine specific gravity [USG], urine protein‐creatinine ratio [UPCR], and urine albumin corrected by creatinine [UAC]) before and after weight loss in dogs with naturally occurring obesity were investigated.Results
Urea (P = .043) and USG (P = .012) were both greater after weight loss than before loss, whilst UPCR, UAC, and creatinine were less after weight loss (P = .032, P = .006, and P = .026, respectively). Homocysteine (P < .001), cystatin C (P < .001) and clusterin (P < .001) all decreased upon weight loss. Multiple linear regression analysis revealed associations between percentage weight loss (greater weight loss, more lean tissue loss; r = ?0.67, r2 = 0.45, P < .001) and before‐loss plasma clusterin concentration (greater clusterin, more lean tissue loss; r = 0.48, r2 = 0.23, P = .003).Conclusion and Clinical Importance
These results suggest possible subclinical alterations in renal function in canine obesity, which improve with weight loss. Further work is required to determine the nature of these alterations and, most notably, the reason for the association between before loss plasma clusterin and subsequent lean tissue loss during weight management.996.
997.
998.
S. P. Lesman J. F. Boucher G. S. Grover S. R. Cox T. L. Bidgood 《Journal of veterinary pharmacology and therapeutics》2013,36(5):462-470
The pharmacokinetics of maropitant were evaluated in beagle dogs dosed orally with Cerenia® tablets (Pfizer Animal Health) once daily for 14 consecutive days at either 2 mg/kg or 8 mg/kg bodyweight. Noncompartmental pharmacokinetic analysis was performed on the plasma concentration data to measure the AUC0–24 (after first and last doses), Ct (trough concentration—measured 24 h after each dose), Cmax (after first and last doses), tmax (after first and last doses), λz (terminal disposition rate constant; after last dose), t1/2 (after last dose), and CL/F (oral clearance; after last dose). Maropitant accumulation in plasma was substantially greater after fourteen daily 8 mg/kg doses than after fourteen daily 2 mg/kg doses as reflected in the AUC0–24 accumulation ratio of 4.81 at 8 mg/kg and 2.46 at 2 mg/kg. This is most likely due to previously identified nonlinear pharmacokinetics of maropitant in which high doses (8 mg/kg) saturate the metabolic clearance mechanisms and delay drug elimination. To determine the time to reach steady‐state maropitant plasma levels, a nonlinear model was fit to the least squares (LS) means maropitant Ct values for each treatment group. Based on this model, 90% of steady‐state was determined to occur at approximately four doses for daily 2 mg/kg oral dosing and eight doses for daily 8 mg/kg oral dosing. 相似文献
999.
Maizon DO Oltenacu PA Gröhn YT Strawderman RL Emanuelson U 《Preventive veterinary medicine》2004,66(1-4):113-126
The objectives of this study were to evaluate the effect of diseases on days open (DO), days to first breeding (DFB) and days from first breeding to conception (DFBC) using survival analysis models, and to assess the significance of the sire component and its possible confounding effect. The data consisted of a random sample of 20% of all herds enrolled in Swedish recording system and using 100% artificial insemination with at least 15 Swedish Red and White cows calving in 1991. The follow-up period was from 45 to 145 d after calving. After editing, the data sets had 23,927, 28,197, and 22,089 cows for days open, days to first breeding, and days from first breeding to conception, respectively. The Cox models included parity, calving season, cow milk production and age at first calving as fixed effects, and herd and sire as random effects. Ten disease groups were considered as possible risk factors for the reproductive traits. Disease groups were treated differently if they occurred before or after 45 d postpartum. Diseases occurring in the first 45 d after calving were treated as time-independent covariates and diseases occurring after day 45 were treated as time-dependent covariates for days open and days to first breeding. The percentages of censored cows were 35% for days open, 19% for days to first breeding, and 33% for days from first breeding to conception. Days open increased in cows with dystocia, stillbirth, retained placenta, metritis, or other diseases occurring in the first 45 d after calving, and in cows with metritis, mastitis, or other diseases occurring after 45 d. Days to first breeding increased in cows with stillbirth, retained placenta, milk fever, mastitis, foot and leg problems, or other diseases occurring before day 45, and in cows with metritis, mastitis, foot and leg problems, or other diseases occurring after 45 d. Days to first breeding decreased in cows treated for ovulatory dysfunctions either before or after 45 d. Days from first breeding to conception increased in cows with dystocia, stillbirth, retained placenta, metritis, or ovulatory dysfunctions occurring before first breeding, and in cows with mastitis occurring after first breeding. Although the additive genetic components were significant for all traits considered, the sires did not act as confounders because only a small amount of variability for the traits considered in this study was explained by the sires, with estimated heritabilities of 2% on the logarithmic scale and from 3 to 4% on the real scale. 相似文献
1000.
Chaudhari SP Malik SV Chatlod LR Barbuddhe SB 《Comparative immunology, microbiology and infectious diseases》2004,27(2):141-148
The isolation of pathogenic Listeria spp. in bacteriological samples, and anti-phosphatidylinositol-specific phospholipase C (anti-PIPLC) antibodies in sera of buffaloes were studied. Isolation of the pathogen was attempted from the samples by selective enrichment in University of Vermont Medium and plating onto Dominguez-Rodriguez isolation agar. Pathogenicity of the isolates was tested by Christie, Atkins, Munch Petersen test and mice incoulation test. Listeria spp. and L. monocytogenes were isolated from 8.8 and 2.4%, and 4.8 and 1.6% of 125 each meat and blood samples, respectively. Out of the 125 samples each of feacal, nasal and vaginal swabs from buffaloes 8 and 4%, 13.6 and 2.4%, and 6.4 and 2.4% were positive for Listeria spp. and L. monocytogenes, respectively. L. ivanovii was confirmed from 0.8% vaginal sample. A total of 125 serum samples were tested by phosphatidylinositol-specific phospholipase C (PIPLC) based indirect ELISA of which 4.0% turned out to be seropositive. 相似文献