全文获取类型
收费全文 | 20361篇 |
免费 | 1568篇 |
国内免费 | 180篇 |
专业分类
林业 | 1305篇 |
农学 | 1122篇 |
基础科学 | 194篇 |
3634篇 | |
综合类 | 2045篇 |
农作物 | 869篇 |
水产渔业 | 1778篇 |
畜牧兽医 | 9005篇 |
园艺 | 372篇 |
植物保护 | 1785篇 |
出版年
2023年 | 143篇 |
2022年 | 157篇 |
2021年 | 252篇 |
2020年 | 326篇 |
2019年 | 419篇 |
2018年 | 670篇 |
2017年 | 647篇 |
2016年 | 633篇 |
2015年 | 530篇 |
2014年 | 591篇 |
2013年 | 992篇 |
2012年 | 1031篇 |
2011年 | 1099篇 |
2010年 | 807篇 |
2009年 | 723篇 |
2008年 | 921篇 |
2007年 | 947篇 |
2006年 | 781篇 |
2005年 | 826篇 |
2004年 | 663篇 |
2003年 | 698篇 |
2002年 | 555篇 |
2001年 | 867篇 |
2000年 | 814篇 |
1999年 | 666篇 |
1998年 | 209篇 |
1997年 | 198篇 |
1996年 | 150篇 |
1995年 | 180篇 |
1994年 | 173篇 |
1993年 | 128篇 |
1992年 | 334篇 |
1991年 | 358篇 |
1990年 | 304篇 |
1989年 | 278篇 |
1988年 | 279篇 |
1987年 | 326篇 |
1986年 | 249篇 |
1985年 | 200篇 |
1984年 | 176篇 |
1983年 | 150篇 |
1982年 | 98篇 |
1981年 | 85篇 |
1980年 | 82篇 |
1979年 | 145篇 |
1978年 | 96篇 |
1977年 | 75篇 |
1975年 | 79篇 |
1974年 | 79篇 |
1969年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Journal of Plant Diseases and Protection - The effects of infections of Barley yellow dwarf virus (BYDV), Fusarium culmorum and F. graminearum alone as well as double infections of BYDV and... 相似文献
122.
The effect of true milk use in the diet of Spanish Brown Swiss male calves on animal performance, carcass and meat quality, and fatty acids composition was studied. In experiment 1, the effect of milk intake [ad libitum continuous (ADLIB) feed vs. restricted 0.7 during 75 days followed by ad libitum feed (RESTR)] and slaughter endpoint (225 kg vs. 5 month) were studied. In experiment 2, ad libitum concentrate feeding [grain-fed (GF)] was compared with milk supplementation until slaughter [milk-fed (MF)] in calves slaughtered at 345 kg. As regards to milk intake, carcass weight and degree of fatness were higher in the ADLIB group (P<0.05). The RESTR group revealed a higher percentage of saturated fatty acids (P<0.05). In experiment 2, the MF group exhibited a higher fat percentage (P<0.05), lower press and cooking losses (P<0.05), and higher scores for tenderness and juiciness (P<0.05) than the GF group. The percentage of saturated fatty acids was higher in the MF group (P<0.05). The results suggest that true milk use in veal production could be an advantageous alternative in terms on production costs, animal performance, and carcass and meat quality. 相似文献
123.
Effects of sub-minimum inhibitory concentration antibiotic levels and temperature on growth kinetics and outer membrane protein expression in Mannheimia haemolytica and Haemophilus somnus
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Brenda Y. Reeks Franklin R. Champlin Daniel B. Paulsen Daniel W. Scruggs Mark L. Lawrence 《Canadian journal of veterinary research》2005,69(1):1-10
The objective of this study was to determine the effects of sub-minimum inhibitory concentrations (sub-MICs) of 2 veterinary antibiotic preparations, chlortetracycline (CTC) and chlortetracycline-sulfamethazine (CTC + SMZ), on growth kinetics and outer membrane protein expression in Mannheimia haemolytica and Haemophilus somnus at normal and febrile body temperatures. Sub-minimum inhibitory concentrations of both antibiotics reduced the growth rates of M. haemolytica and H. somnus. Growth of both species was not inhibited when grown at 41 degrees C compared to 37 degrees C. There was no detectable consistent effect of antibiotic or temperature on outer membrane protein expression for either species. Our study indicates that sub-MIC levels of CTC and CTC + SMZ markedly impair growth of clinical M. haemolytica and H. somnus isolates, potentially allowing more effective host clearance during infection. 相似文献
124.
María Dolores Parra Fernando Tecles Silvia Martínez-Subiela José Joaquín Cerón 《Journal of veterinary diagnostic investigation》2005,17(2):139-144
An established time-resolved immunofluorometric assay designed for measurement of C-reactive protein (CRP) in canine blood was evaluated and validated for use in canine saliva. C-reactive protein was measured in saliva specimens from 5 healthy dogs before and after the injection of casein and in 37 dogs with different disease conditions. The analytical and functional limits of detection were 0.000053 microg/ml and 0.0091 microg/ml, respectively, and intra- and interassay coefficients of variation ranged between 6.7-9.9% and 8.5-16.5%, respectively. A recovery experiment showed no significant disagreement between detected values and expected ones, and saliva CRP concentration was measured in a linear and proportional manner. A positive correlation was found between CRP levels obtained in saliva and serum samples in the experimental (R2 = 0.76) and clinical studies (R2 = 0.70). The assay was able to detect significant differences between salivary CRP levels in healthy dogs and dogs with inflammatory processes. These results suggest that saliva can be used for CRP measurement in dogs. The use of saliva presents the advantage of an easier and less stressful sampling method for the animals, which might be performed outside of hospital environments. 相似文献
125.
126.
Fritz Hervé Saïd Sonia Renaud Pierre-Cyril Mutake Snoden Coid Craig Monicat François 《Landscape Ecology》2003,18(3):293-302
After the eradication of the Tse-Tse fly in the Mid-Zambezi valley, human settlements and fields extended mainly along the main rivers. In order to investigate the consequences of this human development on wildlife diversity we monitored three rivers of the Mid-Zambezi valley in Zimbabwe: Angwa, Manyame and Kadzi. The rivers were divided in segments of 200 m which were checked for spoors in order to assess the number of species and the number of individuals that used the segments. Human settlements were also recorded. We used a GIS to define the spatial characteristics of the fields present along the rivers, and related them to the distribution and abundance of wild species spoors in the river beds and banks. Our results show that the number of species in one segment of the river decreased with the increasing size of the field area bordering the segment. For all the major ungulate species, the numbers of individuals recorded per segment decreased with increasing field area. A similar trend was observed for small and medium-sized carnivores, though they were in lower numbers when present. Our analyses thus confirm that the extension of human agriculture in wildlife areas has an impact on most wild species, but we also define some threshold value of field size above which there seem to be an acceleration of the decrease in wildlife density and diversity: 3.2 ha for medium and small herbivores and carnivores; only the elephant seem to tolerate larger field area with a threshold value of 32 ha.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
127.
128.
Y. Burger N. Katzir G. Tzuri V. Portnoy U. Saar S. Shriber R. Perl-Treves R. Cohen † 《Plant pathology》2003,52(2):204-211
Screening of genotypes of melon ( Cucumis melo ) for resistance to wilt caused by Fusarium oxysporum f.sp. melonis is often characterized by wide variability in their responses to inoculation, even under carefully controlled conditions. The variability at the seedling stage of 17 genotypes susceptible to race 1 was examined in growth-chamber experiments. Disease incidence varied from 0 to 100% in a genotype-dependent manner. Using four combinations of light (60 and 90 µ E m−2 s−1 ) and temperatures of (27 and 31°C), only light intensity showed a statistically significant effect. Marker-assisted selection for fusarium resistance breeding using cleaved amplified polymorphic sequence (CAPS) and sequence-characterized amplified region (SCAR) markers were compared using a single set of genotypes that included 24 melon accessions and breeding lines whose genotype regarding the Fom-2 gene was well characterized. The practical value of the markers for discriminating a range of genotypes and clarifying the scoring of phenotypes was also tested using a segregating breeding population which showed codominant SCAR markers to be useful in marker-assisted selection. 相似文献
129.
130.
Y. J. Huang C. Toscano-Underwood B. D. L. Fitt † X. J. Hu A. M. Hall 《Plant pathology》2003,52(2):245-255
Ascospores of both A-group and B-group Leptosphaeria maculans germinated at temperatures from 5 to 20°C on leaves of oilseed rape. Germination of ascospores of both groups started 2 h after inoculation and percentage germination reached its maximum about 14 h after inoculation at all temperatures. Both the percentage of A-/B-group ascospores that had germinated after 24 h incubation and germ tube length increased with increasing temperature from 5 to 20°C. Germ tubes from B-group ascospores were longer than those from A-group ascospores at all temperatures, with the greatest difference at 20°C. Hyphae from ascospores of both groups penetrated the leaves predominantly through stomata, at temperatures from 5 to 20°C. A-group ascospores produced highly branched hyphae that grew tortuously, whereas B-group ascospores produced long, straight hyphae. The percentage of germinated ascospores that penetrated stomata increased with increasing temperature from 5 to 20°C and was greater for A-group than for B-group L. maculans after 40 h incubation. 相似文献