全文获取类型
收费全文 | 92238篇 |
免费 | 5662篇 |
国内免费 | 47篇 |
专业分类
林业 | 3843篇 |
农学 | 3505篇 |
基础科学 | 637篇 |
11481篇 | |
综合类 | 13952篇 |
农作物 | 3438篇 |
水产渔业 | 5007篇 |
畜牧兽医 | 49152篇 |
园艺 | 1205篇 |
植物保护 | 5727篇 |
出版年
2020年 | 767篇 |
2019年 | 990篇 |
2018年 | 1621篇 |
2017年 | 1876篇 |
2016年 | 1694篇 |
2015年 | 1440篇 |
2014年 | 1766篇 |
2013年 | 3816篇 |
2012年 | 3015篇 |
2011年 | 3692篇 |
2010年 | 2401篇 |
2009年 | 2373篇 |
2008年 | 3577篇 |
2007年 | 3297篇 |
2006年 | 3209篇 |
2005年 | 2755篇 |
2004年 | 2665篇 |
2003年 | 2674篇 |
2002年 | 2456篇 |
2001年 | 3440篇 |
2000年 | 3360篇 |
1999年 | 2614篇 |
1998年 | 1015篇 |
1997年 | 1060篇 |
1996年 | 899篇 |
1995年 | 1036篇 |
1994年 | 909篇 |
1993年 | 912篇 |
1992年 | 1891篇 |
1991年 | 1981篇 |
1990年 | 1909篇 |
1989年 | 1904篇 |
1988年 | 1655篇 |
1987年 | 1637篇 |
1986年 | 1675篇 |
1985年 | 1569篇 |
1984年 | 1261篇 |
1983年 | 1063篇 |
1982年 | 734篇 |
1979年 | 1090篇 |
1978年 | 844篇 |
1975年 | 833篇 |
1974年 | 932篇 |
1973年 | 895篇 |
1972年 | 840篇 |
1971年 | 828篇 |
1970年 | 833篇 |
1969年 | 825篇 |
1968年 | 716篇 |
1967年 | 756篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
971.
De Bosschere H Casaer J Neukermans A Baert K Ceulemans T Tavernier P Roels S 《Veterinary journal (London, England : 1997)》2007,174(3):665-668
Demodex mites are part of the normal fauna of hair follicles of many, if not all, healthy mammal species. Normally these parasites live in harmony with their host, however in states of putative immunosuppression the acarids undergo excessive proliferation and cause clinical disease, which may be localised or generalised. This paper describes four cases of demodicosis in roe deer (Capreolus capreolus) with localised to generalised alopecia. 相似文献
972.
Peripheral blood samples were collected randomly from 195 horses in various parts of Hungary, and the presence of microfilariae was evaluated by the Knott technique. On the basis of morphological identification 18 of the horses (9.2 per cent) were infected with Setaria equina, and the infection was confirmed in 10 animals by pcr and sequencing. The level of microfilaraemia was between 1 and 1138 larvae in 2 ml of blood. There was no correlation between the time of sampling or the sex of the animals (stallions versus mares) and the prevalence of infection, but the prevalence decreased with age. There was a significant association between the prevalence of microfilaraemia and the presence of still waters; positive samples were collected either in the region of Lake Balaton, the largest lake in the country, or at places with nearby ponds. 相似文献
973.
In vitro digestibility analyses of feedstuffs and diets are integrated in the new Danish feed evaluation system for pigs. This system is based on potential physiological energy and standardised digestible amino acids. For characterisation of the energy value of actual batches of feedstuffs and complete diets for pigs, two different in vitro methods have been developed and proved to analyse precisely the digestibility of organic matter at faecal, as well as at ileal, level in the pigs. For characterisation of the protein value in the diet, table values for standardised digestibility of amino acids from the individual feedstuffs are used for calculation of their contribution to the amino acid recommendations for the specific pig category. The results in the present paper indicate that in vitro analyses for digestibility of crude protein in feedstuffs are a reliable tool for calculation of standardised ileal digestibility of the individual amino acids. Thus, the results may question the need for future experiments with surgically modified pigs for analysing ileal digestibility of amino acids in protein sources. Alternatively, in vitro digestibility analyses appear to have a general potential for a precise evaluation of amino acid digestibility in actual batches of feedstuffs and pig diets. 相似文献
974.
Edwards DS Coyne K Dawson S Gaskell RM Henley WE Rogers K Wood JL 《Preventive veterinary medicine》2008,87(3-4):327-339
Feline upper respiratory tract disease (URTD), mainly caused by feline calicivirus (FCV) and feline herpesvirus, is a major cause of disease outbreaks in feline accommodation such as animal shelters, catteries and multi-cat households. We conducted a longitudinal, yearlong study in five UK feline animal shelters to identify risk factors for the time to diagnosis of URTD. We were especially interested in risk factors that could be identified at the time the cat entered the shelter. Shelter staff recorded data for 1434 cats during 2002–2003. Most of the cats were domestic shorthair cats and were from private households, or were stray or abandoned. Sixty cats without clinical signs of URTD at entry had URTD diagnosed (typically within the first month at the centre). We used two multivariable models: one was a Cox proportional-hazards model, and the other a regression analyses with complementary log–log model.The hazard varied substantially between shelters and was considerably lower for the shelter that had a purpose-built admissions unit with its own isolation facilities. The hazard was greater for purebred cats (HR 4.3–5.0) and for neutered cats (HR 2.0). The hazard was also typically greater if the centre had a greater proportion of cats present with URTD. The analyses suggested that the centre-level risk factors were more important in determining hazard than cat-level risk factors. 相似文献
975.
976.
Advanced glycation end products and sorbitol in blood from differently compensated diabetic dogs 总被引:1,自引:0,他引:1
Comazzi S Bertazzolo W Bonfanti U Spagnolo V Sartorelli P 《Research in veterinary science》2008,84(3):341-346
Canine diabetes mellitus (DM) is a common metabolic disorder with long term complications, most of which are caused by glycosylation of structural proteins, decreases in antioxidant concentrations, altered osmotic balance and hypoxia due to impaired oxygen transport. Previous studies have demonstrated that under hyperglycemic conditions canine erythrocytes undergo swelling, probably due to activation of the polyol pathway. The present work aimed to assess the plasma concentration of advanced glycation end (AGE) products, stable Amadori-products generated by non-enzymatic glycosylation of proteins and the intracellular concentration of sorbitol, produced by the activation of polyol pathway in 34 blood samples from diabetic dogs and in 14 controls. AGE products were significantly higher (p<0.01) in plasma from diabetic dogs compared with control animals. The sorbitol concentration in erythrocytes was also significantly higher in diabetic dogs and, in particular, in poorly compensated animals and in dogs with ketonuria. In five cases that were analysed before and after clinical improvement, sorbitol concentration was found to correlate with improvement. These results suggest that non-specific glycosylation is increased and that the polyol pathway is activated in diabetic dogs in a manner that is proportionate to the severity of disease. Moreover, the concentration of AGE products and sorbitol may be useful for monitoring the onset of diabetic complications and assessing the most appropriate therapeutic approaches for management of canine DM. 相似文献
977.
Bussières G Jacques C Lainay O Beauchamp G Leblond A Cadoré JL Desmaizières LM Cuvelliez SG Troncy E 《Research in veterinary science》2008,85(2):294-306
This study addresses development and validation of a composite multifactorial pain scale (CPS) in an experimental equine model of acute orthopaedic pain. Eighteen horses were allocated to control (sedation with/without epidural analgesia - mixture of morphine, ropivacaine, detomidine and ketamine) and experimental groups: amphotericin-B injection in the tarsocrural joint induced pain and analgesia was either i.v. phenylbutazone administered post-induction of synovitis, or pre-emptive epidural mixture, or a pre-emptive combination of the 2. Inter- and intra-observer reproducibility was good (0.8相似文献
978.
Neurologic abnormalities as the predominant signs of neoplasia of the nasal cavity in dogs and cats: seven cases (1973-1986) 总被引:1,自引:0,他引:1
M O Smith J M Turrel C S Bailey G R Cain 《Journal of the American Veterinary Medical Association》1989,195(2):242-245
Neurologic abnormalities were the predominant historic and physical findings in 5 dogs and 2 cats with primary nasal cavity tumors that had invaded the cranial vault. Seizures, behavior changes, and obtundation were the most common signs. Other neurologic signs included paresis, ataxia, circling, visual deficit, and proprioceptive deficit. Although 1 dog and 2 cats had historic findings of mild respiratory disease, no physical abnormalities related to the respiratory tract were found in any of the 7 animals. Nasal cavity neoplasia was suggested by radiographic and computed tomographic studies and was confirmed histopathologically in each case. The nasal tumor types in the 5 dogs were epidermoid carcinoma (n = 1), adenocarcinoma (n = 2), solid carcinoma (n = 1), and anaplastic chondrosarcoma (n = 1). An esthesioneuroblastoma was found in each cat. Radiation therapy was effective for 3 months in palliating the clinical signs in the 2 dogs in which it was used. Neoplasia of the nasal cavity should be considered in the differential diagnosis for animals with neurologic signs suggestive of cerebral disorders. 相似文献
979.
A L Bertone P J VanSoest D Johnson S L Ralston T S Stashak 《American journal of veterinary research》1989,50(9):1621-1627
Fecal excretion of a particulate marker, ytterbium (Yb), was evaluated in 9 horses before surgery and 3 weeks, 3 months, and 6 months (4 trials) after sham-operation (group 1; n = 3) or extensive large colon resection (group 2; n = 6). Fecal excretion curves of total Yb excretion, loge Yb excretion, % Yb excretion, loge % Yb excretion, and cumulative % Yb excretion were evaluated, and kinetic analysis was performed on the loge Yb excretion curves to detect mixing pools and to calculate the fractional rate of particulate passage, turnover rate, and pool size. Calculations were performed to determined transit time, mean overall retention time, adjusted mean retention time, peak time, and disappearance time. Values were statistically analyzed to determine differences between groups and among trials (P less than 0.05). Group-2 horses had significantly shorter transit, peak, and mean overall retention times, compared with preoperative values and with values for group-1 horses. Two mixing pools were identified: a slower emptying pool of 5.7% hour-1 (k1) and a faster emptying pool of 12.3% hour-1 (k2). The rate of passage from the first pool (k1) was not altered by colon resection, and was interpreted as being most influenced by the cecum. In further support of this interpretation, the capacity of the k1 pool approximated the capacity of the cecum (17 L). The capacity of the k1 pool significantly expanded by 6 months in the resected horses. the rate of passage from the second pool (k2) significantly increased initially after colon resection (3 weeks and 3 months), but returned to preoperative values by 6 months.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
980.
The effect of phenylbutazone (4.4 mg/kg of body weight, IV, q 24 h, for 5 days) on glucose tolerance and on secretion of insulin in 6 healthy geldings was determined. Phenylbutazone significantly lowered fasting concentrations of glucose in plasma but did not significantly change the concentration of insulin in serum. There was no significant effect of phenylbutazone on glucose tolerance, on secretion of insulin, or on the area under the insulin/glucose ratio vs time curve in healthy geldings, as determined by paired t test analysis. 相似文献