全文获取类型
收费全文 | 83919篇 |
免费 | 4184篇 |
国内免费 | 649篇 |
专业分类
林业 | 4250篇 |
农学 | 2737篇 |
基础科学 | 679篇 |
8569篇 | |
综合类 | 19138篇 |
农作物 | 3479篇 |
水产渔业 | 3750篇 |
畜牧兽医 | 39850篇 |
园艺 | 1407篇 |
植物保护 | 4893篇 |
出版年
2020年 | 709篇 |
2019年 | 784篇 |
2018年 | 1062篇 |
2017年 | 1297篇 |
2016年 | 1090篇 |
2015年 | 1130篇 |
2014年 | 1314篇 |
2013年 | 3014篇 |
2012年 | 2328篇 |
2011年 | 2687篇 |
2010年 | 1941篇 |
2009年 | 1836篇 |
2008年 | 2599篇 |
2007年 | 2569篇 |
2006年 | 2310篇 |
2005年 | 2194篇 |
2004年 | 1955篇 |
2003年 | 1916篇 |
2002年 | 1826篇 |
2001年 | 2322篇 |
2000年 | 2317篇 |
1999年 | 1878篇 |
1997年 | 705篇 |
1995年 | 816篇 |
1992年 | 1491篇 |
1991年 | 1555篇 |
1990年 | 1666篇 |
1989年 | 1645篇 |
1988年 | 1527篇 |
1987年 | 1477篇 |
1986年 | 1528篇 |
1985年 | 1518篇 |
1984年 | 1247篇 |
1983年 | 1145篇 |
1982年 | 771篇 |
1981年 | 717篇 |
1979年 | 1248篇 |
1978年 | 979篇 |
1977年 | 848篇 |
1976年 | 803篇 |
1975年 | 913篇 |
1974年 | 1201篇 |
1973年 | 1240篇 |
1972年 | 1255篇 |
1971年 | 1182篇 |
1970年 | 1102篇 |
1969年 | 1003篇 |
1968年 | 863篇 |
1967年 | 906篇 |
1966年 | 837篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Weiss CH 《American journal of veterinary research》2010,71(11):1257; author reply 1257-1257; author reply 1258
992.
1. The present study was conducted to investigate the effects of inulin on laying hens. A total of 360 Brown Nick laying hens were divided randomly into 6 groups of 60 with 6 replicates of 10 hens and fed on diets containing 0 (control), 0·1, 0·5, 1·0, 1·5 or 2·0% inulin during the 4-week trial. 2. Dietary supplementation of inulin reduced cholesterol concentration (mg/g yolk) and content (mg/egg) in eggs. Cholesterol content in eggs decreased linearly with increasing levels of dietary inulin level. 3. Supplementation of inulin in diets decreased coliform bacteria counts and pH in the caecum. The lowest coliform bacteria counts (6·30 ± 0·03 log10 cfu/g) and pH (6·47 ± 0·01) were obtained in the 2·0% inulin group, the two indices decreasing by 21·6% and 3·0% respectively, compared with the control group. Coliform bacteria count and pH were changed linearly in accordance with increasing levels of dietary inulin level. Caecal Bifidobacteria counts were increased in the 2·0%-inulin group. 4. Inulin supplementation of layer diets did not appear to have any adverse effects on laying rate, egg weight, feed intake, feed conversion efficiency, cracked-egg rate, eggshell thickness or Haugh unit compared with the control laying hens. 5. Therefore, dietary supplementation with inulin may lead to the development of low-cholesterol chicken eggs as demanded by health-conscious consumers. 相似文献
993.
The present study evaluates the organization and complexity of the temporal pattern of locomotion after an acute administration of propofol in Japanese quail by using traditional and fractal analysis. Birds were administered with propofol 0, 10, 20, 40 or 80 mg/kg. Ten min after administration, they were placed in an open-field apparatus and their locomotor activity was recorded during 45 min at a resolution of 0.5 s. A significant dose dependant increase in the latency to initiate ambulation was observed for doses of 20, 40 and 80 mg/kg when compared to the control group. A rapid recuperation of normal locomotor activity was observed after sedation with 20 mg/kg. Birds administered with propofol 40 mg/kg showed signs of recuperation of normal locomotion after 30 and 40 min (males and females, respectively) of propofol administration, that was not observed in quail treated with propofol 80 mg/kg. Our results suggest that depending on the dose, propofol administration in quail may allow full locomotor recovery of a sedative/anesthetic dose as early as 30 min post-administration. 相似文献
994.
Reasons for performing the study: Dynamic laryngeal collapse (DLC) associated with poll flexion is a performance limiting dynamic upper airway disorder commonly diagnosed in Coldblooded trotters. An inspiratory obstruction occurs when affected horses are driven with tension on the reins, inducing poll flexion. To date, surgical treatment and conservative management have failed to improve racing performance in affected horses. Objectives: To test the efficacy of an external device, the modified checkrein, in limiting poll flexion, diminishing laryngeal collapse and improving airway mechanics when horses are driven on a treadmill with tension on the reins and test the hypothesis that the modified checkrein will limit poll flexion thereby improving endoscopic appearance of the larynx and reduce airway obstruction in harness racehorses affected with DLC. Methods: Fourteen Norwegian Coldblooded trotter (NCT) racehorses previously diagnosed with DLC associated with poll flexion exercised on a high‐speed treadmill at speeds that resulted in heart rate >200 beats/min. Upper airway videoendoscopy recordings, tracheal pressures and video recordings of the head and neck position were collected while horses exercised with the conventional checkrein on Day 1 and the modified checkrein on Day 2. Results: The modified checkrein successfully limited poll flexion as measured by no change in head position parameters between phases of no rein tension and phases of rein tension. Endoscopic scores were significantly improved (arytenoids cartilage collapse P<0.0001; vocal fold collapse P<0.0001) and tracheal peak inspiratory pressures were significantly less negative (P = 0.0162) when horses were fitted with the modified checkrein compared to the conventional checkrein. Conclusions and potential relevance: The modified checkrein successfully limited poll flexion and also prevented upper airway obstruction in NCT horses affected with DLC associated with poll flexion. The modified checkrein seems promising in offering a method of conservative management in harness racehorses affected with this disorder. 相似文献
995.
The concentration of immunoglobulins in faecal extracts was investigated as a method of assessing the production of immunoglobulins by the gut mucosa of 137 dogs. There were significant correlations between the concentrations in faecal extracts and the concentrations produced in duodenal organ cultures. Seventy-six German shepherd dogs had significantly lower median immunoglobulin A (IgA) concentrations in their faecal extracts than 63 controls of various breeds. Sixteen of the German shepherd dogs had IgA concentrations below the 95 per cent confidence limit of the control population and six had no demonstrable faecal IgA. The faecal concentrations of immunoglobulin G and albumin were significantly higher in the German shepherd dogs than in the controls, but their immunoglobulin M concentrations were similar. 相似文献
996.
根据高原地区"春乏"期间,牛、羊因胃肠道线虫病引起死亡严重的突出情况,自列项目,在全州范围划为三大区域,以项目区为中心,在牛、羊发病率和死亡率相对高的乡(镇)、村设点,将93330头(只)牛、羊分为三个组,作为高原地区牛、羊胃肠道线虫病防治技术模块,结果3个试验组用药前胃肠道寄生虫感染率均为100%,早晨在放牧前投喂赛爱吉夏结、克虫特和丙硫苯咪唑等药物后,7 d粪检EPG,虫卵转阴率和虫卵减少数均为100%。间隔7 d重复驱虫1次,防治效果显著。有计划的用驱虫药丙硫咪唑,克虫特、伊维菌素。在每年春季2~3月,秋季8~9月份进行两次驱虫。可提高牛、羊有机体的免疫力,降低牛、羊胃肠道线虫病的发病率和死亡率,减轻对养殖业的危害。 相似文献
997.
本研究旨在阐明去泛素酶USP7对雏鸡抵抗鼠伤寒沙门菌感染的影响。选用3日龄的白来航鸡40只,随机分为2组,每组20只,隔天腹腔注射USP7抑制剂P5091或对照溶剂,连续注射5次,待最后一次注射结束后第4天,对雏鸡人工口服感染鼠伤寒沙门菌,感染24 h后,采集样品,RT-qPCR检测IL-1β、IL-8、TNFα以及NF-κB的mRNA表达,平板涂布法检测雏鸡肝载菌量,H&E染色观察肝和肺的炎症状况。结果表明,P5091抑制USP7活性后,转录因子NF-κB mRNA水平显著降低,并且下游细胞因子IL-1β、IL-8以及TNF-α的表达均下调,雏鸡载菌量下降,H&E染色显示肝与肺炎症反应加剧。综上表明,USP7可能在机体抗沙门菌感染方面起重要作用。 相似文献
998.
Studies on the efficiency of absorbed bovine PPD in tuberculin and serological tests 总被引:1,自引:0,他引:1
H Hammam M Refai W Bisping G Kirpal 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1989,36(3):175-179
The passive haemagglutination, enzyme-linked immunosorbent assay and indirect fluorescent antibody tests were applied to study the non-specific reactions in experimentally infected guinea pigs and tuberculin positive bovines. These cross-reactions were greatly decreased after absorption of either sera with avian PPD or bovine PPD antigen with anti-avian PPD serum. The use of both absorbed sera and antigen raised the specificity of PHA and ELISA to 100%. The use of absorbed sera rendered the IFA specific in 95%. The absorption has reduced the sensitivity of ELISA, IFA and PHA by 14, 27 and 29%, respectively. 相似文献
999.
Gareth H. Spurlock DVM MS Shauna L. Spurlock DVM MS George A. Parker DVM 《Veterinary radiology & ultrasound》1989,30(4):184-188
Collagenase-induced lesions of the superficial digital flexor tendon were monitored using diagnostic ultrasound and subsequently compared with gross and microscopic findings. The postinjury sonograms demonstrated hypoechoic or anechoic areas corresponding to areas of hemorrhage and necrosis. The size of the lesion increased and the echogenicity decreased with increasing units of collagenase injected into the tendon. As postinjury time increased, echogenicity increased, which corresponded to fibrous-tissue invasion and collagen deposition. The extent of tendon injury produced correlated with the amount of collagenase injected into the tendon. Diagnostic ultrasound is useful in evaluating injury and healing in collagenase— induced tendinitis. 相似文献
1000.
The effect of a single intramammary infusion of a biological response modifier in cows at drying off
Bibiana Elisabet Dallard H. H. Ortega I. A. Iguzquiza N. R. Salvetti O. A. Quaino L. F. Calvinho 《Veterinary research communications》2010,34(6):519-532
Biological response modifiers (BRM) are compounds that interact with the immune system to regulate specific aspects of host
response. The objective of this study was to describe clinical and morphological changes during involution of bovine mammary
gland following a single-dose infusion of a BRM containing lipopolysaccharide and cellular fractions of Escherichia coli incorporated into liposomes. A massive leukocyte response and increased subepithelial stroma infiltration of mononuclear
cells, eosinophils and mast cells was observed in BRM-treated quarters compared with untreated controls; however, morphologic
parameters assessed at 11 days post infusion were indicative of only slightly accelerated involution compared with untreated
controls. In addition, BRM infusion at the end of lactation did not interfere with mammary epithelial cell proliferation and
caused only mild systemic effects. 相似文献