全文获取类型
收费全文 | 13173篇 |
免费 | 948篇 |
国内免费 | 1147篇 |
专业分类
林业 | 80篇 |
农学 | 476篇 |
基础科学 | 8篇 |
164篇 | |
综合类 | 3378篇 |
农作物 | 330篇 |
水产渔业 | 650篇 |
畜牧兽医 | 8466篇 |
园艺 | 374篇 |
植物保护 | 1342篇 |
出版年
2024年 | 41篇 |
2023年 | 234篇 |
2022年 | 370篇 |
2021年 | 541篇 |
2020年 | 584篇 |
2019年 | 633篇 |
2018年 | 382篇 |
2017年 | 500篇 |
2016年 | 618篇 |
2015年 | 641篇 |
2014年 | 718篇 |
2013年 | 673篇 |
2012年 | 918篇 |
2011年 | 914篇 |
2010年 | 752篇 |
2009年 | 696篇 |
2008年 | 651篇 |
2007年 | 803篇 |
2006年 | 647篇 |
2005年 | 514篇 |
2004年 | 392篇 |
2003年 | 387篇 |
2002年 | 293篇 |
2001年 | 345篇 |
2000年 | 315篇 |
1999年 | 259篇 |
1998年 | 203篇 |
1997年 | 152篇 |
1996年 | 127篇 |
1995年 | 138篇 |
1994年 | 117篇 |
1993年 | 89篇 |
1992年 | 93篇 |
1991年 | 83篇 |
1990年 | 78篇 |
1989年 | 66篇 |
1988年 | 50篇 |
1987年 | 54篇 |
1986年 | 30篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1956年 | 15篇 |
1955年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
I. J. Uhaa H. P. Riemann M. C. Thurmond C. E. Franti 《Veterinary research communications》1990,14(2):99-112
A seroepidemiological study on bluetongue virus (BTV) infection in California dairy cattle was conducted to estimate the prevalence and distribution by age and season of BTV group-reactive antibodies and to look for possible associations between the presence of antibodies and cattle age or breed and farm. Between December 1985 and March 1987, a sample of cattle was tested at approximately two-month intervals for BTV group-reactive antibodies using an enzyme-linked immunosorbent assay (ELISA). Data taken during the month of December 1986 were used to evaluate possible associations between a positive antibody test and certain intrinsic (age, breed) and extrinsic (farm) factors.Univariate and multivariate statistical analyses using the -square test for associations and multiple logistic regression, respectively, were carried out for possible associations between positive antibody tests to BTV and each factor of interest. The strengths of the associations were determined using estimates of the odds ratio.Of the 3774 serum samples tested, 238 (6.3%) were from calves, 1045 (27.6%) were from heifers and 2492 (66.0%) were from cows. Seroprevalence varied from nil in calves on two occasions to over 90% on several occasions in cows. Cows consistently had higher prevalence rates than heifers or calves across all test dates (p<0.05). The seroprevalence of BTV group-reactive antibodies also showed a seasonal fluctuation, with the highest rates occurring during the warmer months of the year. These highest prevalence rates coincided with heavy activity of the known vector of BTV, Culicoides spp. Breed and farm effects were not statistically significant (p>0.05). With the exception of one farm, all cattle were of the Holstein breed, which reduced confidence in assessing any breed effect in this study. Relative estimates of the sensitivity and specificity of BTV ELISA were 87% and 100% respectively, compared to the standard agar gel immunodiffusion (AGID) test.The observations support previous findings of seasonal distribution of BTV antibodies and suggest an age relationship, whereby older cattle are more likely to be positive to BTV group-reactive antibodies than younger cattle. 相似文献
72.
S. Murphy A. M. Hayes L. Blackwood G. Maglennon H. Pattinson A. H. Sparkes 《Veterinary and comparative oncology》2005,3(4):222-229
A retrospective study was undertaken of dogs presented to the Animal Health Trust for treatment of oral malignant melanoma, without radiographic evidence of pulmonary metastases. Group 1 (n = 13) received radiotherapy of the primary and any lymph node metastases (4 weekly fractions of 9 Gy); and group 2 (n = 15) were treated the same but additionally received between two and six doses carboplatin at 300 mg m?2 every 3 weeks. Median survival times for the two groups were 307 and 286 days, respectively (P > 0.05). In addition, carboplatin therapy did not significantly reduce the proportion of dogs dying due to metastases (three from group 1 and four from group 2). We found no evidence of a beneficial effect of carboplatin therapy over radiotherapy alone. 相似文献
73.
74.
柑橘抗CTV转基因与分子标记研究进展 总被引:1,自引:0,他引:1
综述了柑橘抗衰退病基因工程中两方面的研究进展。介绍多种来源于柑橘衰退病毒(Citrustriztezavirus,CTV)核酸序列的转基因柑橘和抗性种质资源中抗性基因的分子标记,以及所涉及的方法和遇到的问题。目前研究表明,虽然已成功实现对病毒衣壳蛋白(CP)等基因的转化和Ctv等抗性基因的标记,但尚未获得对CTV有高度抗性的转基因柑橘,而抗性基因亦不能实现定点克隆和转化。因此上述两方面研究还有待深入。 相似文献
75.
76.
Sandy I. Wang DVM Kyle G. Mathews DVM MS Ian D. Robertson BVSc Marty Stebbins DVM PhD Brian J. Trumpatori BS 《Veterinary radiology & ultrasound》2005,46(1):39-43
Acetabular angles (AAs) and dorsal acetabular rim angles acquired by computed tomographic (CT) imaging have been used to assess patient response to juvenile pubic symphysiodesis surgery. The purpose of this study was to evaluate the effects of patient positioning and slice selection on these angles, and an attempt was made to devise a repeatable method of measuring these angles that would eliminate positioning effects. We found significant variation in AAs with small differences in pelvic tilt and slice selection. Dorsal acetabular rim angles were not affected. As a result of positioning differences from one CT study to the next, every attempt should be made to standardize pelvic tilt, or eliminate its effect on AAs by standardizing gantry angle in relation to an anatomic landmark that will not change over time. The floor of the sacral vertebral canal may be a reasonable landmark for this purpose and deserves further study. 相似文献
77.
Tsutomu MATSUMOTO Yuichiro NARA Hiromitsu FURUYA Harumi TAKAHASHI Kiichi TAIRAKO Hideki YAMAMOTO 《Journal of General Plant Pathology》2002,68(4):382-384
L11A-Fukushima (L11A-F) derived from attenuated isolate LuA of Tomato mosaic virus (ToMV) has the highest ability to cross protect against virulent ToMV among LuA and its derivatives and is stably inherited.
Growth, yield, fruit quality and symptom attenuation of inoculated tomato plants did not differ significantly between L11A-F and L11A. The infectivity of progeny viruses in tomato infected with LuA-F was less than 4% of that with virulent ToMV. From these
results, L11A-F appears to possess the properties necessary for practical use. To manage L11A-F strictly, a PCR-based assay to detect trace contamination of virulent ToMV in L11A-F preparations was established.
Received 10 June 2002/ Accepted in revised form 30 October 2002 相似文献
78.
Shohei MATSUURA Shigeru HOSHINO Hideaki HAYASHI Tetsuyuki KOHGUCHI Kyoji HAGIWARA Toshihiro OMURA 《Journal of General Plant Pathology》2002,68(1):99-102
DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum
production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently
infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV
originating from latently infected stock plants in chrysanthemum production fields.
Received 27 July 2001/ Accepted in revised form 27 November 2001 相似文献
79.
Kentaro OKUNO Mitsuro KAMEYA-IWAKI Minoru TAKESHITA Naruto FURUYA Yoichi TAKANAMI 《Journal of General Plant Pathology》2002,68(1):108-109
A Cucumber mosaic virus was newly isolated from Silene armeria and was characterized by biological, serological and molecular biological methods.
Received 4 July 2001/ Accepted in revised form 28 August 2001 相似文献