全文获取类型
收费全文 | 177573篇 |
免费 | 9194篇 |
国内免费 | 133篇 |
专业分类
林业 | 7413篇 |
农学 | 5462篇 |
基础科学 | 1140篇 |
21564篇 | |
综合类 | 32993篇 |
农作物 | 7144篇 |
水产渔业 | 8379篇 |
畜牧兽医 | 89108篇 |
园艺 | 2298篇 |
植物保护 | 11399篇 |
出版年
2018年 | 2384篇 |
2017年 | 2713篇 |
2016年 | 2435篇 |
2015年 | 2041篇 |
2014年 | 2588篇 |
2013年 | 6589篇 |
2012年 | 4856篇 |
2011年 | 6044篇 |
2010年 | 3868篇 |
2009年 | 3964篇 |
2008年 | 5873篇 |
2007年 | 5545篇 |
2006年 | 5234篇 |
2005年 | 4931篇 |
2004年 | 4696篇 |
2003年 | 4869篇 |
2002年 | 4452篇 |
2001年 | 5080篇 |
2000年 | 5118篇 |
1999年 | 4112篇 |
1998年 | 1832篇 |
1997年 | 1759篇 |
1996年 | 1656篇 |
1995年 | 1948篇 |
1994年 | 1779篇 |
1993年 | 1624篇 |
1992年 | 3449篇 |
1991年 | 3613篇 |
1990年 | 3621篇 |
1989年 | 3629篇 |
1988年 | 3328篇 |
1987年 | 3321篇 |
1986年 | 3391篇 |
1985年 | 3292篇 |
1984年 | 2743篇 |
1983年 | 2384篇 |
1982年 | 1691篇 |
1979年 | 2576篇 |
1978年 | 2103篇 |
1977年 | 1792篇 |
1976年 | 1795篇 |
1975年 | 1954篇 |
1974年 | 2359篇 |
1973年 | 2348篇 |
1972年 | 2268篇 |
1971年 | 2131篇 |
1970年 | 2054篇 |
1969年 | 1987篇 |
1968年 | 1628篇 |
1967年 | 1805篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
H. Petznek M. Kleiter A. Tichy A. Fuchs-Baumgartinger C. Hohenadl 《Research in veterinary science》2014
Therapy of cats suffering from feline injection site sarcomas (FISS) is still a challenging problem, as the recurrence rate after surgery is up to 70%. Four FISS-derived primary tumour cell lines and corresponding xenograft tumour mouse models were established to evaluate the efficacy of a concomitant chemo-/radiation therapy with doxorubicin. In vitro, strongly depending upon the timing of administration, pre-treatment with 0.25 µmol doxorubicin resulted in a significant enhancement of radiation-induced (3.5 Gy) tumour cell death. This result was confirmed in vivo, where only the combined chemo-/radiation therapy resulted in a significant reduction in tumour growth compared to the respective mono-therapies with either doxorubicin or radiation. These results support the use of the concomitant chemo-/radiation therapy for adjuvant treatment of FISS, particularly in advanced or recurrent disease where surgery alone is no longer feasible. 相似文献
992.
A.M.B. Veldhuis I.M.G.A. Santman-Berends J.M. Gethmann M.H. Mars L. van Wuyckhuise P. Vellema M. Holsteg D. Höreth-Böntgen F.J. Conraths G. van Schaik 《Preventive veterinary medicine》2014
Schmallenberg virus (SBV), a novel orthobunyavirus that rapidly spread throughout north-western Europe in 2011, caused congenital malformations in lambs and goat kids (Van den Brom et al., 2012) and newborn calves (Hoffmann et al., 2012). The impact of the SBV epidemic seemed limited however, in terms of the number of affected herds with malformed offspring (European Food Safety Authority, 2012b). Nevertheless, little is known with regard to the overall within-herd impact of SBV infection. The objective of the current study was to quantify the impact of the 2011 SBV epidemic on the productivity of dairy cattle in the Netherlands and the district of Kleve, Germany. 相似文献
993.
994.
Recent epidemiological features of the zoonotic dermatophyte Trichophyton verrucosum were investigated in 294 calves from 20 farms located in Central Italy. By the combination of microscopic examinations and fungal cultures, the total prevalence rate of T. verrucosum infection was found to be high, with 87.7% of samples yielding positive results and 100% of farms being infected. Farm to farm prevalence of infection varied from 25% to 100% of the examined calves. Prevalence rates were higher in females than males (91.6% versus 84%), in >3-< or =6 than >6-< or =9 month old calves (89.8% versus 85.7%), in purebred than in crossbred (88.5% versus 81.8%), and in symptomatic than asymptomatic ones (95.7% versus 80.4%). T. verrucosum was as prevalent in semi-intensive as in intensive breeding system (88.2% versus 87.6%) but more prevalent in calves raised for meat rather than milk production (91.1% versus 84.9%), and reared under conventional than organic production management system (89.3% versus 82.6%). Prevalence rates were also higher when the cattle present in the farm were of mixed origin, rather than when the whole stock was purchased or was born in the farm (92% versus 88.2% and 85.7%), when other cattle in the farm were showing skin signs (90% versus 84.2%), and at least one case of human ringworm was recorded in the farm (90.9% versus 86.1%). No statistically significant association was found. Therefore, T. verrucosum infection may be more widespread in calves from Central Italy than it was previously thought to be. Calves of any sex, breed, age, and of any of the farm condition considered, are highly exposed to the risk of infection. As calves may play a considerable role as reservoirs of the infection, our results highlight the need to determine the incidence and the importance of T. verrucosum ringworm in personnel involved with cattle care in Italy and elsewhere. 相似文献
995.
Until recently, pyothorax in the cat has been generally considered to have a poor prognosis. However, it has become clear that most cats that survive the first 48 h following presentation can be successfully treated with aggressive medical management. In this second part of a two-part review, logical guidelines for the management of the disease are discussed, with particular emphasis on antimicrobial selection. Patient stabilisation and supportive care, techniques for pleural space drainage and lavage and indications for surgery are reviewed. 相似文献
996.
Xiaokai Song Lixin XuRuofeng Yan Xinmei HuangMohammed Ali A. Shah Xiangrui Li 《Veterinary parasitology》2009
The immunization procedure of DNA vaccine pcDNA–TA4–IL-2 of Eimeria tenella, including route, dose, time of immunization and age of primary immunization of chicken, was optimized. The stability and the cross-species protection of the vaccine were also analyzed. Efficacy of immunization was evaluated on the basis of oocyst decrease ratio, lesion score, body-weight gain and the anti-coccidial index (ACI). Chinese Yellow chickens were randomly distributed into corresponding groups (30/group). The challenged, unchallenged and vector control groups were designed. The results illustrated that 25 μg was the optimal dose and intramuscular injection was the most effective route to induce protective immunity. There were no significant differences of ACIs between boosting and non-boosting groups. Storage time and temperature had little effect on the immunizing efficacy of the vaccine. The vaccine could provide partial cross-protection against the challenge with E. necatrix and E. acervulina, but not with E. maxima. 相似文献
997.
Reasons for performing study: Insight into the loading pattern of the articular cartilage surface during the complete stride is important as biomechanical factors play a pivotal role in the pathogenesis of joint trauma and osteoarthritis (OA). Objectives: To determine the loading pattern in the equine MCP articulation in vitro during simulated walk. Methods: Eight cadaveric limbs from mature Dutch Warmblood horses were loaded in a pneumatic loading device in 6 different positions (A1‐A6). The pressure distribution on the articular surface of the proximal phalanx (P1) was measured at 7 sites (S1‐7) using intra‐articularly placed pressure sensitive films, which were analysed by scanning and densitometry. Results: Pressures recorded after mid‐stance (A4, 5, 6) were significantly (P<0.05) higher than those before (A1, 2, 3) and showed the biphasic loading pattern of the walk at all sites, except for the site halfway along the sagittal groove (S7). At S7, there was a linear increase in pressure during the progress of the stance phase of the stride in most horses. Medially (S4, 5, 6) the pressure was significantly higher than laterally (S1, 2, 3) (P<0.05). Conclusions and potential relevance: The heavier medial loading coincides with the location where articular cartilage degeneration in the process of OA in the equine MCP joint is known to start. The discrepancy between the loading of the central groove and the other parts of the joint may result in large stress differences at the end of the stance phase, which might be related to the pathogenesis of stress fractures in the first phalanx and distal third metacarpal bone. 相似文献
998.
Reasons for performing study: Infundibular changes are frequently encountered computed tomographic studies of the equine maxillary cheek teeth but the possible importance of this finding is not known. Infundibular caries is a possible cause for pulpitis and apical infection in some horses. Objectives: To study the relationship between the 2 pathologies and the frequency of changes. Methods: The maxillary cheek teeth 108‐ 208 , 109–209 and 110–210 of 25 horses were evaluated using computed tomography and both the prevalence of infundibular and apical infection changes as the possible link with apical infection evaluated statistically. Results: The prevalence of infundibular changes was high in both normal and diseased teeth. Both apical infection and the occurrence of infundibular changes were more prevalent in 109–209 and 110–210. In spite of this, the 2 processes could not be linked to one another. No differences were noted between the left and right sides. Conclusions: A direct relationship between the 2 processes was not established statistically and other underlying causes for the high occurrence of both apical infection and infundibular changes in diseased and normal 108‐ 208 , 109–209 and 110210 are considered. 相似文献
999.
A. Pellegrini‐Masini I. Rodriguez Hurtado A. J. Stewart T. J. Divers 《Equine Veterinary Education》2009,21(2):79-84
Venous air embolism was suspected in 3 hospitalised horses on the basis of an inadvertently open jugular venous line. Subsequently the 3 horses developed clinical signs including cardiovascular collapse, cardiac dysrhythmia, pulmonary oedema, behavioural abnormalities and neurological signs consistent with central nervous system injury. Treatment included intranasal oxygen therapy, i.v. fluid administration and anti‐inflammatory therapy. Specific therapy aimed at treating air embolism in man is reviewed, with pertinent therapy potentially applicable to horses emphasised. 相似文献
1000.
The objectives of the present study were to quantify the amount of nucleic acids, to examine the nucleobase composition and to determine the digestibility of individual nucleobases in diets containing various products from bacterial biomass grown on natural gas, including autolytic and hydrolytic fractions, using mink (Mustela vison) as a model animal. The diets consisted of cod fillet (control), commercial basic BioProtein, and five experimentally produced autolytic and hydrolytic fractions of the bacterial protein meal as protein sources. Each diet was assigned to four adult male mink, housed individually in cages equipped for controlled feeding and quantitative collection of faeces. Faeces were collected for 4 days, and the individual nucleobases in diet and faeces were analysed by HPLC after hydrolysis using HClO(4). The content of nucleobases in the diets containing bacterial protein meal was 37% to 205% higher than in the control diet. The nucleobase-nitrogen in the control diet amounted to 4.3% of the total nitrogen content, whereas the experimental bacterial protein diets contained from 7.4% to 17.4% of the total N content in the form of nucleic acids. The various methods used to produce the bacterial protein fractions clearly affected both the amount of nucleic acids and the molar proportions of the individual nucleobases. The average digestibility of the nucleobases was 95%, and all the individual nucleobases were highly digestible. Uracil showed the highest digestibility (on average 96.8%), whereas thymine showed the lowest digestibility (on average 93.6%). 相似文献