全文获取类型
收费全文 | 171885篇 |
免费 | 8594篇 |
国内免费 | 373篇 |
专业分类
林业 | 9811篇 |
农学 | 6356篇 |
基础科学 | 1186篇 |
22862篇 | |
综合类 | 26059篇 |
农作物 | 8337篇 |
水产渔业 | 9595篇 |
畜牧兽医 | 81188篇 |
园艺 | 3032篇 |
植物保护 | 12426篇 |
出版年
2020年 | 1425篇 |
2019年 | 1668篇 |
2018年 | 4898篇 |
2017年 | 5229篇 |
2016年 | 3604篇 |
2015年 | 2178篇 |
2014年 | 2696篇 |
2013年 | 6460篇 |
2012年 | 5568篇 |
2011年 | 7875篇 |
2010年 | 5745篇 |
2009年 | 5126篇 |
2008年 | 7004篇 |
2007年 | 6864篇 |
2006年 | 5124篇 |
2005年 | 4816篇 |
2004年 | 4576篇 |
2003年 | 4753篇 |
2002年 | 4161篇 |
2001年 | 4917篇 |
2000年 | 5018篇 |
1999年 | 3934篇 |
1998年 | 1727篇 |
1997年 | 1674篇 |
1996年 | 1505篇 |
1995年 | 1781篇 |
1994年 | 1586篇 |
1993年 | 1444篇 |
1992年 | 3013篇 |
1991年 | 3239篇 |
1990年 | 3044篇 |
1989年 | 3127篇 |
1988年 | 2828篇 |
1987年 | 2769篇 |
1986年 | 2885篇 |
1985年 | 2734篇 |
1984年 | 2203篇 |
1983年 | 1969篇 |
1979年 | 2138篇 |
1978年 | 1730篇 |
1977年 | 1416篇 |
1976年 | 1465篇 |
1975年 | 1556篇 |
1974年 | 1832篇 |
1973年 | 1855篇 |
1972年 | 1752篇 |
1971年 | 1552篇 |
1970年 | 1523篇 |
1969年 | 1575篇 |
1967年 | 1394篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The eosinophilic granuloma complex is a group of skin disorders common in cats. This paper describes the clinical, haematological and histopathological features of 17 related Norwegian forest cats, six of which had a linear granuloma on the caudal thigh, three of which also had a granuloma on the lower lip, and one of which had a granuloma in combination with an indolent ulcer. The high prevalence of the disease in this population is suggestive of a genetic background. 相似文献
972.
Dryden MW Payne PA Ridley R Smith V 《Veterinary therapeutics : research in applied veterinary medicine》2005,6(1):15-28
A variety of procedures are available to detect parasite eggs or oocysts in feces. This study compared the efficacy of simple flotation, a commercial assay, and various centrifugation techniques and three common flotation solutions. Results indicate that centrifugation consistently recovered more eggs than other methods. Proper technique is critical, including ensuring that the specific gravity of the flotation solution is correct and allowing the sample to stand for a sufficient amount of time before examining the coverslip. Because of the zoonotic health risks of many companion animal parasites, veterinarian and their staff should better utilize fecal examinations in their routine diagnostic plan. 相似文献
973.
Wildblood LA Kerr K Clark DA Cameron A Turner DG Jones DG 《Veterinary immunology and immunopathology》2005,107(1-2):57-65
Eosinophilia is a well documented feature of helminth infections but the precise nature of the interaction between parasite and eosinophil remains an enigma. This paper describes experiments demonstrating that ruminant gastrointestinal trichostrongyles produce potent chemoattractant activity for ovine bone marrow-derived eosinophils in vitro. This activity was initially identified as a constituent of whole worm extracts of third and fourth larval (L3, L4), and adult stages of Teladorsagia circumcincta, and adult Haemonchus contortus. Similar activity was detected in excretory/secretory (E/S) material derived from live T. circumcincta L3. Subsequently, by adapting the assay technique to incorporate live worms directly into the system, it was shown that L3 of both T. circumcincta and H. contortus produced eosinophil chemoattractant activity. In contrast, neither whole worm extracts, or E/S preparations from mixed stages of the free-living nematode Caenorhabditis elegans contained eosinophil chemoattractant activity, and there was no evidence of chemoattractant production by live C. elegans. The results described are challenging to the traditional dogma that eosinophils are host-protective effector cells, and raise the intriguing possibility that ovine nematodes actively encourage recruitment of eosinophils. Local eosinophil-mediated mucosal damage, comparable to that seen in the asthmatic lung, may then provide a permissive local microenvironment for the parasite. Moreover, if they prove important for pathogenicity, nematode chemoattractants could offer future potential as novel therapeutic targets. 相似文献
974.
Torres SM Diaz SF Nogueira SA Jessen C Polzin DJ Gilbert SM Horne KL 《Journal of the American Veterinary Medical Association》2005,227(2):239-243
OBJECTIVE: To determine frequency of urinary tract infection (UTI) among dogs with pruritic disorders that were or were not receiving long-term glucocorticoid treatment. DESIGN: Observational study. ANIMALS: 127 dogs receiving glucocorticoids for > 6 months and 94 dogs not receiving glucocorticoids. PROCEDURE: Bacterial culture of urine samples was performed in dogs receiving long-term glucocorticoid treatment, and information was collected on drug administered, dosage, frequency of administration, duration of glucocorticoid treatment, and clinical signs of UTI. For dogs not receiving glucocorticoids, a single urine sample was submitted for bacterial culture. RESULTS: Multiple (2 to 6) urine samples were submitted for 70 of the 127 (55%) dogs receiving glucocorticoids; thus, 240 urine samples were analyzed. For 23 of the 127 (18.1%) dogs, results of bacterial culture were positive at least once, but none of the dogs had clinical signs of UTI. Pyuria and bacteriuria (present vs absent) were found to correctly predict results of bacterial culture for 89.9% and 95.8% of the samples, respectively. Type of glycocorticoid, dosage, frequency of administration, and duration of treatment were not associated with frequency of UTI. None of the urine samples from dogs not receiving glucocorticoids yielded bacterial growth. The frequency of UTI was significantly higher for dogs treated with glucocorticoids than for dogs that had not received glucocorticoids. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that dogs receiving long-term glucocorticoid treatment have an increased risk of developing a UTI. On this basis, we recommend that urine samples be submitted for bacterial culture at least yearly for such dogs. 相似文献
975.
One-day-old Taiwan native male chicks were fed with maize-soybean rearing diets without supplemental vitamin E to 23 weeks of age. From 23 to 52 weeks of age, the cockerels (n = 90) were assigned at random to 5 dietary treatments and fed with maize-soybean diets supplemented with 0, 20, 40, 80 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate). Pullets (225) of the same age were fed with standard diets throughout. They were artificially inseminated with one dose of 0.04 ml/bird intact and 5-fold diluted pooled semen at 31 to 43 weeks of age and at 49 weeks of age, respectively. The criteria evaluated included: semen quality, fertility and maximum and effective duration of fertility, blood characteristics, body and testes weight. Supplemental vitamin E did not affect cockerels' effective duration of fertility and percentage of fertility. However, when pullets were inseminated with diluted semen, supplementing 160 mg/kg vitamin E increased the maximum duration of fertility at 49 weeks of age. Cockerels receiving 40 to 160mg/kg supplements had higher sperm viability and motility after 39 weeks of age and those fed 80 mg/kg had higher sperm concentration at 39 weeks of age. Cockerels receiving supplements of more than 40 mg/kg vitamin E had higher body weight gain. Plasma cholesterol and testosterone were not affected by supplemental vitamin E. However, plasma luteinising hormone (LH) concentration was lower in cockerels fed 160 mg/kg. Lack of supplemental vitamin E over 39 weeks was associated with lower semen quality but did not reduce the proportion of fertile eggs laid by inseminated hens, perhaps because the insemination dose compensated for low sperm quality. We found that the maximum duration of fertility might be improved by supplementing 160 mg/kg vitamin E at 49 weeks of age. 相似文献
976.
A. P. Nicolle V. Chetboul H. Namba F. Crespeau A. Tidholm C. Carlos V. Gouni J. L. Pouchelon 《Veterinary radiology & ultrasound》2005,46(3):230-233
A 6-year-old female cat developed pleural and abdominal effusion. Cardiac ultrasound and 2D color tissue Doppler imaging revealed restrictive cardiomyopathy with severe biatrial dilatation and hypertension. This cardiomyopathy was associated with atrial septal aneurysm and a patent foramen ovale. The atrial septal aneurysm involved the entire atrial septum. Necropsy and histological examination confirmed all these findings. ASA is a rare malformation and, as in this cat, it generally occurs concomitantly with congenital or acquired heart disease and may be explained by greater pressure in one atrium, leading to controlateral protrusion of the atrial septum. 相似文献
977.
978.
Elsinghorst TA 《The Veterinary quarterly》2005,27(3):127-137
In 2003, Veterinary Quarterly started with the publication of a series of articles reviewing reports on "first cases" of animal diseases. Till now six articles have been published. They were arranged in order of animal species. Each article concerned only one species. Starting at this seventh publication, each article discusses "first cases" on more than one animal species. In this article 15 cases published in 2005 are discussed: one in birds, two in cats, three in cattle, four in dogs, two in goats, one in hares, and two in horses. Of each case a short introduction, the bibliographical data of the publication, the abstract of the author(s) (except one case) and some additional information (mainly) derived from the article are given. 相似文献
979.
Eiler H Frank N Andrews FM Oliver JW Fecteau KA 《American journal of veterinary research》2005,66(9):1598-1604
OBJECTIVE: To characterize the physiologic response to i.v. bolus injection of glucose and insulin for development of a combined glucose-insulin test (CGIT) in horses. ANIMALS: 6 healthy mares and 1 mare each with pituitary adenoma and urolithiasis. PROCEDURE: Horses were given a CGIT (glucose, 150 mg/kg; insulin, 0.1 U/kg); results were compared with a singular i.v. glucose tolerance test (GTT; 150 mg/kg) and a singular i.v. insulin sensitivity test (IST; 0.1 U/kg). Healthy horses were also given a CGIT after receiving xylazine and undergoing stress. RESULTS: Physiologically, the CGIT resulted in a 2-phase curve with positive (hyperglycemic) and negative (hypoglycemic) portions; the positive phase came first (250% of baseline at 1 minute). The descending segment declined linearly to baseline by approximately 30 minutes and to a nadir at 58% of baseline by 75 minutes. After a 35-minute valley, a linear ascent to baseline began. Addition of insulin in the CGIT increased glucose utilization by approximately 4.5 times during the positive phase but not during the negative phase. The diseases' effects and experimental inhibition of insulin secretion with xylazine and stress were detectable by use of the 2 phases of the CGIT. Only a single positive phase resulted from the GTT and a single negative phase from the IST CONCLUSIONS AND CLINICAL RELEVANCE: The CGIT resulted in a consistent, well-defined glycemia profile, which can be disrupted experimentally or by a disease process. The CGIT has clinical potential because it provides integrated information and more information than either the singular GTT or IST. 相似文献
980.
Congenital or acquired feline femoral dysplasia have seldom been reported in the literature. This report describes two cases of femoral dysplasia involving the proximal epiphyses. Bilateral agenesis of the femoral head and neck (case 1) constituted an incidental finding during a post-traumatic radiographic examination, while right proximal femoral dysplasia (case 2) was observed during an orthopaedic examination for lameness. To the authors' knowledge, such imaging findings have not been reported before in cats. 相似文献