全文获取类型
收费全文 | 2670篇 |
免费 | 200篇 |
专业分类
林业 | 554篇 |
农学 | 34篇 |
基础科学 | 5篇 |
544篇 | |
综合类 | 209篇 |
农作物 | 86篇 |
水产渔业 | 77篇 |
畜牧兽医 | 1220篇 |
园艺 | 40篇 |
植物保护 | 101篇 |
出版年
2023年 | 17篇 |
2022年 | 12篇 |
2021年 | 28篇 |
2020年 | 37篇 |
2019年 | 15篇 |
2018年 | 104篇 |
2017年 | 99篇 |
2016年 | 89篇 |
2015年 | 62篇 |
2014年 | 79篇 |
2013年 | 183篇 |
2012年 | 167篇 |
2011年 | 152篇 |
2010年 | 82篇 |
2009年 | 70篇 |
2008年 | 144篇 |
2007年 | 147篇 |
2006年 | 141篇 |
2005年 | 139篇 |
2004年 | 140篇 |
2003年 | 136篇 |
2002年 | 123篇 |
2001年 | 82篇 |
2000年 | 87篇 |
1999年 | 47篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 49篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1980年 | 16篇 |
1978年 | 13篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1970年 | 7篇 |
1961年 | 7篇 |
1958年 | 8篇 |
1957年 | 7篇 |
1955年 | 8篇 |
排序方式: 共有2870条查询结果,搜索用时 15 毫秒
61.
OBJECTIVE: To evaluate the possible association between facet joint geometry and intervertebral disk degeneration in German Shepherd Dogs. ANIMALS: 25 German Shepherd Dogs and 11 control dogs of similar body weight and condition. PROCEDURE: Facet joint angles in the caudal portion of the lumbar region of the vertebral column (L5-S1) were measured by use of computed tomography, and the intervertebral discs were evaluated microscopically. The relationship between facet joint geometry and disk degeneration was evaluated by use of statistical methods. RESULTS: German Shepherd Dogs had significantly more facet joint tropism than control dogs, but an association with disk degeneration was not found. However, German Shepherd Dogs had a different facet joint conformation, with more sagittally oriented facet joints at L5-L6 and L6-L7 and a larger angle difference between the lumbar and lumbosacral facet joints, compared with control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: A large difference between facet joint angles at L6-L7 and L7-S1 in German Shepherd Dogs may be associated with the frequent occurrence of lumbosacral disk degeneration in this breed. 相似文献
62.
Immune mediated hemolytic anemia (IMHA) in dogs is a severe disease with a high mortality rate. As human immunoglobulin (HIG) was reported to be beneficial for the treatment of IMHA in dogs we examined the influence of HIG on the course of the disease in our dogs with IMHA. Of 22 dogs with primary IMHA 9 dogs received in addition to routine immunosuppressive therapy HIG at a dose of 0.19 to 0.68 g/kg (median 0.35 g/kg), 13 dogs did not receive HIG (-HIG group). Both groups were similar in terms of age, weight, the presence of autoagglutination, spherocytosis, positive Coombs' test, icterus and pigmenturia. The lowest hematocrit measured during the disease was significantly lower in the +HIG group compared to the -HIG group and dogs in the +HIG group received significantly more transfusions than those of the -HIG group. This is an indication for more severe disease signs of the +HIG group dogs. Although mortality during hospitalization and the time from hospital admission to release or death was not significantly different between the two groups, we interpret this similar course of the IMHA despite more severe signs of the +HIG group dogs as a potential positive effect of the HIG therapy. 相似文献
63.
A health problem of an animal or a group of animals represents a potential stress situation for the animal keeper. In this article, the transactional stress model, which was developed in social psychology was applied on the animal keeper and shows, how he perceives the influence of animal care. If veterinary help is considered relevant, it may lead to an improved coping, which affects the health of the animal keeper and the animal as well. This viewpoint leads to a cycle, in which cause, success, coping and utility are closely linked together. 相似文献
64.
Mischke R Meurer D Hoppen HO Ueberschär S Hewicker-Trautwein M 《Research in veterinary science》2002,73(3):267-272
Oestradiol-17beta and testosterone blood plasma concentrations were measured in dogs with Leydig-cell tumours (n=20), Sertoli-cell tumours (n=6), seminomas (n=9), unilateral inguinal cryptorchidism (n=7), abdominal cryptorchidism (n=9, one bilateral), degenerate scrotal testicles (n=6, two bilateral), and animals with normal scrotal testicles (n=20). The testosterone/oestradiol ratio (testosterone concentration [ng/mL]x100/oestradiol concentration [pg/mL]) was calculated.A considerably higher oestradiol concentration was found in dogs with Sertoli-cell tumours (29.0, 14.4-48.3 pg/mL; median, minimum-maximum; P=0.0256, Mann-Whitney test) and lower oestradiol levels were found in animals with seminomas (12.0, 3.4-17.6 pg/mL; P=0.0025) compared to the healthy control group (18.0, 8.6-31.5 pg/mL). Testosterone concentration was decreased in dogs with Sertoli-cell tumours (0.08, 0.03-0.77 ng/mL) when compared to the control group (1.95, 0.05-3.70 ng/mL; P=0.0012). Testosterone/oestradiol ratios differed from the control (9.6, 0.58-35.8) only in dogs with Sertoli-cell tumours (0.32, 0.06-2.80; P=0.0005). Clinical signs of feminization were observed in five dogs with Sertoli-cell tumour and one dog with a Leydig-cell tumour, and were more often associated with decreased testosterone/oestradiol ratios than with an increased oestradiol-17beta concentration. 相似文献
65.
Zientara S Sailleau C Dauphin G Roquier C Rémond EM Lebreton F Hammoumi S Dubois E Agier C Merle G Bréard E 《The Veterinary record》2002,150(19):598-601
In October 2000, bluetongue virus was detected on the French island of Corsica. The disease was also reported in Sardinia, Calabria, Sicily and on the Spanish islands of Majorca and Minorca. This paper describes the use of molecular techniques for a rapid identification and serotype determination of serotype 2 of the virus. The nucleotide sequences of segments 2 and 7 of the genome of the Corsican strain were determined and its phylogenetic relationships are described. 相似文献
66.
Schnyder M Stärk KD Vanzetti T Salman MD Thor B Schleiss W Griot C 《The Veterinary record》2002,150(4):102-109
An outbreak of classical swine fever in wild boar in the southern part of Switzerland (Canton of Ticino) was investigated after the implementation of control measures in a defined infected area (the risk zone), and in a surrounding surveillance zone (the non-risk zone). After the disease had been detected, hunting was not allowed in the risk zone for over six months, during which the disease was left to run its course, but hunting was continued in the non-risk zone for one month. After seven months, a hunting strategy targeted at young animals was implemented in both zones. Between May 1998 and January 2000,1294 wild boar were shot or found dead, and diagnostic and biological data were collected and analysed. Only one animal from the non-risk zone was found to be seropositive for antibodies to the virus, whereas 179 of 528 wild boar from the risk zone were virus positive and 162 were seropositive. The proportion of virus-positive animals decreased from 62.7 per cent to zero over one year. During the first hunting season, seropositive animals were found in all age groups, but 12 months later only animals more than one year old had antibodies against the virus. 相似文献
67.
Siebert U Müller G Desportes G Weiss R Hansen K Baumgärtner W 《The Veterinary record》2002,150(9):273-277
Staphylococcus aureus septicaemia was diagnosed in a dead, stranded harbour porpoise from the German Baltic Sea and in a live harbour porpoise by-caught in inner Danish waters and taken into captivity. Lesions included pyogranulomatous myocarditis, necrotising suppurative bronchopneumonia, pyelonephritis, osteomyelitis and leptomeningitis, and abscesses in lymph nodes and skeletal muscles. The captive animal had fibrinous suppurative epicarditis and pyogranulomatous myocarditis with abscesses. In both animals the organism was suspected to have entered through skin lesions or via the respiratory tract. 相似文献
68.
69.
The objective of the study was to identify risk factors for reintroduction of Actinobacillus pleuopneumoniae and Mycoplasma hyopneumoniae (enzootic pneumonia) onto pig farms in areas in Switzerland that were involved in an eradication programme from 1996 to 1999 and to assess the role of dealers in relation to these reinfections. The study was based on the comparison of pig farms that were reinfected in the year 2000 (cases) and pig farms that remained uninfected in the same area (controls). Additionally, data were collected from Swiss pig dealers and transport companies. Out of a total of 3983 farms, 107 farms were reinfected in the year 2000. The incidences were 0.1% for Actinobacillus pleuopneumoniae and 2.6% for Mycoplasma hyopneumoniae (enzootic pneumonia). Compared to reinfection rates prior to the eradication programme, this is a considerable reduction. Statistically significant risk factors for the reinfection were 'finishing farm', 'large mixed breeding-finishing farm', 'reinfected neighbour' and 'parking site for pig transport vehicles close to the farm'. Pig farmers that purchased pigs from only one supplier per batch had a lower risk of reintroducing infection (protective factor). As long as infected and uninfected regions co-exist in Switzerland, direct and indirect contact between farms, pig herds and slaughter sites via transport vehicles are a major pathway of disease spread. Risk management measures linked to these contacts are therefore of key importance. The survey of dealers indicated various areas for improvement such as strategic planning of pick-up routes or cleaning and disinfecting of trucks. 相似文献
70.
Schwyzer M Fischer-Bracher C Fraefel C Bächi T Nuñez R Engels M Ackermann M 《Veterinary microbiology》2002,86(1-2):165-174
Herpes simplex virus-1 (HSV-1) based amplicon vectors are promising gene delivery vehicles because they have a large transgene capacity and can efficiently transduce many different cell types, including non-dividing cells, of various animal species. The Circ protein of bovine herpesvirus-1 (BHV-1) is a myristylated virion component of unknown function. Preliminary experiments with a circ gene deletion mutant indicated that Circ may influence the host's immune response by downregulating MHC-II expression in bovine monocytes. To get more insight into the function of Circ, amplicon vectors were constructed with various open reading frames (ORFs) under the control of the HSV-1 IE4/5 promoter: (i) the Circ ORF alone, (ii) a fusion ORF encoding an N-terminal Circ fused to the enhanced green fluorescent protein (eGFP), (iii) the eGFP ORF alone, and (iv) the Circ ORF in the inverted orientation. Upon helpervirus-free packaging into HSV-1 amplicon particles and transduction of Vero cells, both Circ alone and the Circ-eGFP fusion protein produced a punctate pattern within the cytoplasm, suggesting membrane association of the myristylated protein. In contrast, eGFP alone was evenly distributed over the cytoplasm of transduced cells. Upon infection of bovine buffy-coat cells, it was observed that cells of the monocyte lineage but not lymphocytes were transduced. Transgene expression reached a peak around 20h after transduction and lasted for at least 90h. Transduced monocytes underwent specific morphological changes, which may be attributed to Circ synthesis. 相似文献