全文获取类型
收费全文 | 483篇 |
免费 | 21篇 |
专业分类
林业 | 11篇 |
农学 | 4篇 |
基础科学 | 4篇 |
93篇 | |
综合类 | 140篇 |
农作物 | 6篇 |
水产渔业 | 4篇 |
畜牧兽医 | 226篇 |
园艺 | 11篇 |
植物保护 | 5篇 |
出版年
2021年 | 10篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2014年 | 7篇 |
2013年 | 28篇 |
2012年 | 16篇 |
2011年 | 31篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 13篇 |
2007年 | 18篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 25篇 |
2001年 | 9篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 9篇 |
1968年 | 6篇 |
1966年 | 5篇 |
排序方式: 共有504条查询结果,搜索用时 15 毫秒
1.
Esdras M. Carbajal M. Carolina Zuleta Luellen Swayzer Brian M. Schwartz Maria Carolina Chavarro A. Carolina Ballen‐Taborda Susana R. Milla‐Lewis 《Plant Breeding》2019,138(6):958-966
St. Augustinegrass is well suited for lawns and commercial landscapes. While many genotypes are cross‐fertile, all cultivars are propagated vegetatively in sod production. To ensure varietal purity, development of sterile triploid hybrids by crossing tetraploid and diploid genotypes has been successfully used in other warm‐season turfgrasses. Applying this model in St. Augustinegrass would be beneficial to sod producers and turf managers who require purity for certification and uniformity for performance, respectively. This study was conducted to develop colchicine‐induced tetraploid lines of St. Augustinegrass. Seeds of cultivar ‘Raleigh’ were treated with four colchicine concentrations at four exposure times. A non‐treated control was included among the treatments. Seedlings that germinated were screened for genome size changes using flow cytometry. Line DSA 13005 and two progeny lines derived through selfing, DSA 16001 and DSA 16016, were corroborated as tetraploids (2n = 4x = 36) through chromosome counts. These lines will be used in future breeding efforts to attempt development of sterile triploid cultivars of St. Augustinegrass. 相似文献
2.
The veterinary profession is experiencing a shortage of veterinarians, with attrition recognised as a substantial contributor. Research has also indicated increased levels of mental ill health and alarming suicide rates in practitioners. The primary aim of this study was to investigate the impact of eleven modifiable workplace factors on mental health outcomes, job appreciation and intention to leave the veterinary profession. The second aim was to ascertain whether workplace factors influence mental health outcomes after controlling for individual resilience. An online survey was completed by 73 practising Australian veterinarians. Unfavourable workplace factors correlated with adverse outcomes including depression, stress, reduced job appreciation and increased likelihood of leaving both the role and the profession. Workplace factors remained linked with the outcomes of job appreciation, depression and stress whilst controlling for practitioner resilience. Job appreciation was a significant predictor of intention to leave both the current role and the profession. Via multiple linear regression, two categories were identified as associated with improved psychological outcomes and job appreciation. These were workplace factors that represent breaks from workload and control or decision latitude in the workplace. Whilst resilience represents a key area for intervention, workplace factors potentially represent an easier-to-modify area for intervention. 相似文献
3.
4.
Li SQ Zhang HQ Balasubramaniam VM Lee YZ Bomser JA Schwartz SJ Dunne CP 《Journal of agricultural and food chemistry》2006,54(3):739-746
Immunoglobulin-rich foods may provide health benefits to consumers. To extend the refrigerated shelf life of functional foods enriched with bovine immunoglobulin G (IgG), nonthermal alternatives such as high-pressure processing (HPP) may offer advantages to thermal processing for microbial reduction. To evaluate the effects of HPP on the immunoactivity of bovine IgG, a soymilk product enriched with milk protein concentrates, derived from dairy cows that were hyperimmunized with 26 human pathogens, was subjected to HPP or heat treatment. To achieve a 5 log reduction in inoculated Escherichia coli 8739, the HPP or heat treatment requirements were 345 MPa for 4 min at 30 degrees C or for 20 s at 70 degrees C, respectively. To achieve a 5 log reduction in natural flora in the enriched soymilk, the HPP or heat treatments needed were 552 MPa for 4 min at 30 degrees C or for 120 s at 78.2 degrees C, respectively. At equivalent levels for a 5 log reduction in E. coli, HPP and heat treatment caused 25% and no detectable loss in bovine IgG activity, respectively. However, at equivalent levels for a 5 log reduction in natural flora, HPP and heat resulted in 65 and 85% loss of bovine IgG activity, respectively. Results of combined pressure-thermal kinetic studies of bovine milk IgG activity were provided to determine the optimal process conditions to preserve product function. 相似文献
5.
Clarke JD Riedl K Bella D Schwartz SJ Stevens JF Ho E 《Journal of agricultural and food chemistry》2011,59(20):10955-10963
Increased consumption of cruciferous vegetables such as broccoli may reduce the risk of various cancers. Myrosinase is required to convert dietary glucosinolates from broccoli into bioactive isothiocyanates. We evaluated isothiocyanate excretion profiles in healthy subjects who consumed broccoli sprouts or broccoli supplement (no myrosinase) with equivalent glucosinolate content. Urinary metabolites of two major isothiocyanates, sulforaphane and erucin, were measured by liquid chromatography coupled with tandem mass spectrometry. Peak excretion of sulforaphane and erucin was higher and occurred sooner in subjects who consumed broccoli sprouts as compared to subjects who consumed the supplement. A subject-dependent shift in the ratio of urinary sulforaphane to erucin metabolites was observed in both groups, indicating conversion of sulforaphane to erucin. Lower histone deacetylase activity was observed in the peripheral blood mononuclear cells only in subjects consuming sprouts. Fresh broccoli sprouts differ from broccoli supplements in regards to excretion of isothiocyanates and bioactivity in human subjects. 相似文献
6.
A previous study indicated that regenerated spent fluid catalytic cracking catalyst, added to a test activated sludge system, increased the sludge settling rate, decreased the settled sludge volume (compaction), decreased the supernatant (effluent) TOC and increased the supernatant optical clarity. In addition, phosphate levels were markedly reduced in a municipal sewerage a ctivated sludge system. As an extension of this study, fresh, spent, and regenerated cracking catalysts have been examined to determine if the observed activity could be attributed to the carbon and metals deposited on the catalyst during the cracking operation. To do this the earlier studies have been repeated and adsorption isotherm tests have been conducted with fresh, spent and regenerated catalysts. The results indicate that: (1) the carbon and metals on the catalyst surface do not affect the improved settling and compaction of activated sludge observed when the catalyst is present, nor do they affect TOC removals; (2) none of the catalysts tested adsorb soluble TOC to an appreciable extent; and (3) the presence of catalyst, by enhancing compaction, may stabilize the activated sludge system during wet weather conditions. 相似文献
7.
Steve Cherry Gary C. White Kim A. Keating Mark A. Haroldson Charles C. Schwartz 《Journal of Agricultural, Biological & Environmental Statistics》2007,12(2):195-215
Current management of the grizzly bear (Ursus arctos) population in Yellowstone National Park and surrounding areas requires annual estimation of the number of adult female bears
with cubs-of-the-year. We examined the performance of nine estimators of population size via simulation. Data were simulated
using two methods for different combinations of population size, sample size, and coefficient of variation of individual sighting
probabilities. We show that the coefficient of variation does not, by itself, adequately describe the effects of capture heterogeneity,
because two different distributions of capture probabilities can have the same coefficient of variation. All estimators produced
biased estimates of population size with bias decreasing as effort in creased. Based on the simulation results we recommend
the Chao estimator for model M
h
be used to estimate the number of the female bears with cubs of the year; however, the estimator of Chao and Shen may also
be useful depending on the goals of the research. 相似文献
8.
Paul Dijkstra Ayaka Ishizu Stephen C. Hart Egbert Schwartz Bruce A. Hungate 《Soil biology & biochemistry》2006,38(11):3257-3266
Stable isotope analysis is a powerful tool in the study of soil organic matter formation. It is often observed that more decomposed soil organic matter is 13C, and especially 15N-enriched relative to fresh litter and recent organic matter. We investigated whether this shift in isotope composition relates to the isotope composition of the microbial biomass, an important source for soil organic matter. We developed a new approach to determine the natural abundance C and N isotope composition of the microbial biomass across a broad range of soil types, vegetation, and climates. We found consistently that the soil microbial biomass was 15N-enriched relative to the total (3.2 ‰) and extractable N pools (3.7 ‰), and 13C-enriched relative to the extractable C pool (2.5 ‰). The microbial biomass was also 13C-enriched relative to total C for soils that exhibited a C3-plant signature (1.6 ‰), but 13C-depleted for soils with a C4 signature (−1.1 ‰). The latter was probably associated with an increase of annual C3 forbs in C4 grasslands after an extreme drought. These findings are in agreement with the proposed contribution of microbial products to the stabilized soil organic matter and may help explain the shift in isotope composition during soil organic matter formation. 相似文献
9.
10.
Yanchong Huangfu Michael E. Essington Shawn A. Hawkins Forbes R. Walker John S. Schwartz Alice C. Layton 《Communications in Soil Science and Plant Analysis》2019,50(11):1358-1369
Determining the total elemental concentrations of soils requires a total dissolution method, in which hydrofluoric acid (HF) is commonly used. However, this method is tedious and risky due to the dangerous reagent HF. This study compared a single acid extraction technique using a nitric acid (HNO3) extraction method to total dissolution (HF + microwave assisted aqua regia) for evaluating the total elemental concentrations in soils and sediments. The two methods were used to analyze the elemental content of soils and sediments from the Oostanaula Creek and Pond Creek watersheds in East Tennessee. Twenty-one elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Nd, P, S, Si, Sr, Ti, V, Zn, and Zr) were subsequently measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The extraction efficiency for HNO3 relative to the total was compared and discussed. In general, HNO3 can extract the elements in absorbed phases and those residing in non-silicate minerals. Six elements (Ba, Co, Fe, Ca, Mn, and P) generated significant correlations between total and HNO3 in both OC and PC watersheds. Finally, the elements were grouped according to the interrelationships of their total elemental concentrations based on the dendrogram plots, suggesting their geochemical association in soils and sediment forming minerals. 相似文献