全文获取类型
收费全文 | 547篇 |
免费 | 22篇 |
专业分类
林业 | 26篇 |
农学 | 48篇 |
基础科学 | 2篇 |
65篇 | |
综合类 | 43篇 |
农作物 | 107篇 |
水产渔业 | 24篇 |
畜牧兽医 | 216篇 |
园艺 | 8篇 |
植物保护 | 30篇 |
出版年
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 20篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 34篇 |
2012年 | 21篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 34篇 |
2007年 | 24篇 |
2006年 | 22篇 |
2005年 | 26篇 |
2004年 | 25篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 19篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1961年 | 2篇 |
1958年 | 3篇 |
1933年 | 1篇 |
1926年 | 1篇 |
1925年 | 1篇 |
1923年 | 2篇 |
排序方式: 共有569条查询结果,搜索用时 15 毫秒
61.
62.
Budong Qian Reinder De Jong Richard Warren Aston Chipanshi Harvey Hill 《Agricultural and Forest Meteorology》2009,149(6-7):1022-1031
A study to forecast regional spring wheat (Triticum aestivum L.) yields on the Canadian Prairies was conducted, based on simulated daily water use and soil water contents derived from the National Drought Model. Empirical linear regression models were calibrated from 1976 to 2006 spring wheat yield data for this purpose. Potential predictors assessed were mainly those indicators related to water stress conditions at different crop growth stages. Stepwise regression and cross-validation were employed for the selection of the predictors in multivariate linear regression models used for forecasting spring wheat yields from seeding to harvest. The cross-validated “forecasts” for 1976–2006, using data up to harvest, explained 77%, 64%, 63% and 70% of yield variances, respectively, for Alberta, Saskatchewan, Manitoba and the entire Prairie region. Root mean squared error of the “forecasts” ranged from 8% to 11% of the average yields. The prediction accuracy earlier in the season was often lower than later in the season. Usable prediction accuracy was found by the middle of the growing season (around heading or anthesis), but only marginally effective at seeding time, especially so for Saskatchewan. 相似文献
63.
Hak Jin Kim Yong Woo Kim In Sook Lee Jong Woon Song Yeon Joo Jeong Seon Hee Choi Kyung Un Choi Kuen Tak Suh Byung Mann Cho 《Acta veterinaria Scandinavica》2009,51(1):30
Background
To test the hypothesis that triolein emulsion will increase vascular permeability of skeletal muscle.Methods
Triolein emulsion was infused into the superficial femoral artery in rabbits (triolein group, n = 12). As a control, saline was infused (saline group, n = 18). Pre- and post-contrast T1-weighted MR images were obtained two hours after infusion. The MR images were qualitatively and quantitatively evaluated by assessing the contrast enhancement of the ipsilateral muscles. Histologic examination was performed in all rabbits.Results
The ipsilateral muscles of the rabbits in the triolein group showed contrast enhancement, as opposed to in the ipsilateral muscles of the rabbits in the saline group. The contrast enhancement of the lesions was statistically significant (p < 0.001). Histologic findings showed that most examination areas of the triolein and saline groups had a normal appearance.Conclusion
Rabbit thigh muscle revealed significantly increased vascular permeability with triolein emulsion; this was clearly demonstrated on the postcontrast MR images. 相似文献64.
Marian E.H. Bos Mirjam Nielen Guus Koch Annemarie Bouma Mart C.M. De Jong Arjan Stegeman 《Preventive veterinary medicine》2009,88(4):278-285
To optimize control of an avian influenza outbreak knowledge of within-flock transmission is needed. This study used field data to estimate the transmission rate parameter (β) and the influence of risk factors on within-flock transmission of highly pathogenic avian influenza (HPAI) H7N7 virus in the 2003 epidemic in The Netherlands. The estimation is based on back-calculation of daily mortality data to fit a susceptible-infectious-dead format, and these data were analysed with a generalized linear model. This back-calculation method took into account the uncertainty of the length of the latent period, the survival of an infection by some birds and the influence of farm characteristics. After analysing the fit of the different databases created by back-calculation, it could be concluded that an absence of the latency period provided the best fit. The transmission rate parameter (β) from these field data was estimated at 4.50 per infectious chicken per day (95% CI: 2.68–7.57), which was lower than what was reported from experimental data. In contrast to general belief, none of the studied risk factors (housing system, flock size, species, age of the birds in weeks and date of depopulation) had significant influence on the estimated β. 相似文献
65.
Md Romij Uddin Leonard John Wade Jong Yeong Pyon Md Abdul Mazid 《Journal of Crop Science and Biotechnology》2009,12(1):17-23
An experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh in Old
Brahmaputra Alluvial Flood Plain (AEZ-9) during December 2005 to May 2006 to examine the root growth of different rice cultivars
under various establishment methods. This experiment comprised two sets of treatment (i) three methods of planting viz., dry
direct seeding, wet direct seeding and transplanting, and (ii) six rice cultivars, two inbreds viz., BRRI Dhan 28 and BRRI
Dhan 29, two hybrids, viz., Aalok 6201 and Sonarbangla 1 and two local improved cultivar viz., Habigonj IV and Habigonj VIII.
Cultivars had more remarkable effect on different root parameters i.e. number of roots, root length, root length density,
root biomass, root weight ratio and root shoot ratio of hybrid, inbred and local improved rice cultivars than method of planting.
BRRI Dhan 28 performed the best for most of the parameters. At harvest, BRRI Dhan 29 showed the best rooting behavior among
the cultivars. For both stages hybrid rice cultivars showed intermediate and local improved cultivars performed lower in rooting
behavior. Direct seeding method performed better than transplanting method for most of the root parameters but wet direct
seeding and dry direct seeding methods were identical. Interaction effect between method of planting and cultivar in most
of the root parameters were insignificant. But, BRRI Dhan 28 and BRRI Dhan 29 under wet direct seeding method and Sonarbanngla
1 under transplanting method showed the best rooting performance among the other combinations. 相似文献
66.
The dynamics of the friction yarn formation process is described in terms of the dynamic behavior of the process state variables.
Production efficiency and product quality of friction spinning are influenced by these process state variables. This study
was performed with the intention of setting up a dynamic model based on mass balance in order to delineate the dynamic behavior
of the cross-sectional area of the in-process bundle on the friction drum surface and to attain the distribution profiles
of the cross-sectional area in transient state and in steady state as well. Then, simulation results were compared with those
of the experiment, while the input variation was used as a test signal. Theoretical model shows that the bundle thickness
on the friction drum has the dynamic characteristics of an integrating system with interval due to the finite length of the
input fleece zone, and is in good correspondence with the results of the experiment. A periodic change in the fleece feeding
rate led to the fact that there was a specific range of the fluctuation wavelength in the fleece feeding rate, whereas a change
in the in-process bundle thickness completely disappeared or became locally maximized in certain wavelength areas. This could
lead to a magnification or inaction of the perturbations with the corresponding wavelength in the bundle thickness; a bundle
thickness irregularity. Experiments also identified that the theoretical model accurately described the fiber accumulation
dynamics in a friction spinning process. 相似文献
67.
Effects of road transportation on metabolic and immunological responses in Holstein heifers 下载免费PDF全文
Hyeok‐Joong Kang In Kyu Lee Min‐Yu Piao Chae‐Won Kwak Min Jeong Gu Cheol Heui Yun Hyun‐Jin Kim Hyeon‐Ju Ahn Hee‐Bal Kim Gyeom‐Heon Kim Soo‐Ki Kim Jong‐Youl Ko Jong K. Ha Myunggi Baik 《Animal Science Journal》2017,88(1):140-148
This study examined the effects of road transportation on metabolic and immunological responses in dairy heifers. Twenty Holstein heifers in early pregnancy were divided into non‐transported (NT; n = 7) and transported (T; n = 13) groups. Blood was collected before transportation (BT), immediately after transportation for 100 km (T1) and 200 km (T2), and 24 h after transportation (AT). The T heifers had higher (P < 0.05) blood cortisol and non‐esterified fatty acid concentrations after T1 and T2 than did NT heifers. By contrast, the T heifers had lower (P < 0.05) serum triglyceride concentrations after T1 and T2 than had the NT heifers. The serum cortisol and triglyceride concentrations returned (P > 0.05) to the BT concentrations at 24 h AT in the T heifers. The granulocyte‐to‐lymphocyte ratio and the percentage of monocytes were higher (P < 0.05) after T2 in the T heifers than in the NT heifers, suggesting that transportation stress increased the numbers of innate immune cells. T heifers had higher (P < 0.01) plasma haptoglobin concentrations than NT heifers 24 h AT. In conclusion, transportation increased cortisol secretion and was correlated with increased metabolic responses and up‐regulation of peripheral innate immune cells in dairy heifers. 相似文献
68.
Yea Hwang MOON Ji Un OK Shin Ja LEE Jong Kyu HA Sung Sill LEE 《Animal Science Journal》2010,81(6):642-647
A comparative study among Korean native cow (Hanwoo), Holstein dairy cow, Korean native goat and crossbred sheep on the population and marker concentration of ruminal microbes, the activities of carboxymethylcellulase (CMCase), xylanase and amylase, and in situ dry matter (DM) degradability were conducted. Twelve ruminally cannulated animals, three of each species, were used. Animals were fed the same diet containing 40% formula feed and 60% rice straw at the level of 2.5% of body weight. Total viable microbial populations in the rumen fluid were significantly (P < 0.01) greater for bacteria and fungi in goat than those of Holstein. The protozoan population among ruminant species was the reverse from that of bacteria. The concentrations of 2,6‐diaminopimelic acid and chitin as markers for bacteria and fungi in the rumen fluid, respectively, were highest in goat, which is in accordance with the above population data. The concentration of aminoethylphosphonic acid as marker of protozoa was highest in Hanwoo and lowest in sheep (P < 0.01). Goat had the highest (P < 0.01) activities of all the enzymes investigated among ruminants. In situ effective degradation of the DM of rice straw was approximately 19% higher in the rumen of goat compared with other animals. 相似文献
69.
Ben de Jong Carlos Anaya Omar Masera Marcela Olguín Fernando Paz Jorge Etchevers René D. Martínez Gabriela Guerrero Claudio Balbontín 《Forest Ecology and Management》2010
In this paper we present the Mexican inventory of greenhouse gas (GHG) emissions from the land-use sector. It involved integration of forest inventory, land-use and soil data in a GIS to estimate the net flux of GHG between 1993 and 2002. 相似文献
70.
Soybean seed includes various bioactive substances. Also, they contain a variety of antinutritional factors including lipoxygenase, Kunitz trypsin inhibitor (KTI), lectin, and 7S α' subunit proteins. The genetic removal of these proteins will improve the nutritional value of soybean seed. The objective of this research was to breed new soybean with tetra recessive alleles (lox1lox2lox3/lox1lox2lox3‐ti/ti‐le/le‐cgy1/cgy1) for lipoxygenase, KTI, lectin, and 7S α' subunit proteins. Seven parents were used to breed tetra null strain. SDS‐PAGE and Western blot analysis were used to determine the presence or absence of lipoxygenase, 7S α' subunit, KTI, and lectin proteins in mature seed. Tetra null soybean line has a purple flower, determinate growth habit, tan pod, and yellow seed coat colour. Stem height of the breeding line was 62.3 cm. The 100‐seed weight of the breeding line was 27.1 g and yield (t/ha) was 2.84. This is the first soybean strain with lox1lox2lox3/lox1lox2lox3‐ti/ti‐le/le‐cgy1/cgy1 genotype (absence of lipoxygenase, KTI, lectin, and 7S α' subunit proteins). 相似文献