全文获取类型
收费全文 | 2032篇 |
免费 | 102篇 |
专业分类
林业 | 52篇 |
农学 | 59篇 |
基础科学 | 3篇 |
345篇 | |
综合类 | 282篇 |
农作物 | 276篇 |
水产渔业 | 145篇 |
畜牧兽医 | 836篇 |
园艺 | 28篇 |
植物保护 | 108篇 |
出版年
2022年 | 24篇 |
2021年 | 40篇 |
2020年 | 26篇 |
2019年 | 28篇 |
2018年 | 48篇 |
2017年 | 48篇 |
2016年 | 45篇 |
2015年 | 46篇 |
2014年 | 59篇 |
2013年 | 91篇 |
2012年 | 106篇 |
2011年 | 141篇 |
2010年 | 63篇 |
2009年 | 52篇 |
2008年 | 103篇 |
2007年 | 112篇 |
2006年 | 68篇 |
2005年 | 83篇 |
2004年 | 75篇 |
2003年 | 72篇 |
2002年 | 55篇 |
2001年 | 33篇 |
2000年 | 44篇 |
1999年 | 37篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1994年 | 14篇 |
1992年 | 23篇 |
1991年 | 34篇 |
1990年 | 31篇 |
1989年 | 27篇 |
1988年 | 20篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 27篇 |
1984年 | 20篇 |
1983年 | 19篇 |
1979年 | 20篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 17篇 |
1973年 | 23篇 |
1972年 | 18篇 |
1971年 | 14篇 |
1970年 | 18篇 |
1969年 | 19篇 |
1968年 | 12篇 |
1966年 | 11篇 |
排序方式: 共有2134条查询结果,搜索用时 15 毫秒
141.
Chang Seok Lee Kyu Song Lee Jun Kwon Hwangbo Young Han You Joon Ho Kim 《Water, air, and soil pollution》2004,156(1):251-273
Plants tolerant to polluted environments were selected, based on several criteria, to restore a coastal forest ecosystem severely damaged by air pollutants discharged from an industrial complex. In addition, a restoration plan was prepared synthesizing these results and the diagnostic ecological indicators in the area for which restoration is required. Pollution-tolerant plants of 11 tree and subtree species, 10 herb species and one shrub species were selected from field surveys in the vicinity of two representative industrial complexes in Korea, Ulsan and Yeocheon. Nine species were selected for tolerance to SO2 fumigation and six species were selected for tolerance to Al3+. Growth and photosynthetic responses of sample plants transplanted into polluted and unpolluted sites showed that 15 species out of the 26 sample plants showed a disposition for tolerance. Most of these are endemic plants and they are composed of diverse species in structure and function. This result implies that these tolerant species could play important roles in the restoration of the study area, which has several specific features. On the other hand, results from transplant tests indicate that a field survey is the most reasonable method for selection of tolerant plants to restore a pollution-damaged ecosystem, as was shown in another restoration program. Results of ecological analysis on vegetation map indicate that the spatial range within the first ridge is the sector for which restoration is required. This sector was classified into four zones on the basis of topographic conditions: lower and upper slopes of both slopes facing and opposite the pollution source. Guidelines for soil amelioration and arrangement of tolerant plants were prepared considering the degree of vegetation degradation, leaf damage of major plant species and soil pollution in each zone under the restoration plan. 相似文献
142.
Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a multitude of habitats). Plants were grown individually and in combination until L. latifolium flowered, then roots and aboveground mass were harvested. Soil in individual pots was homogenized, subsamples collected for nutrient analyses, and the soil was re-planted to the same species, grown, and harvested twice more for a total of three growth cycles. As nutrient supplying capacity of the soil declined through growth cycles, aboveground mass of L. latifolium decreased significantly (PА.05) and growth potential of B. tectorum surpassed that of L. latifolium. Only bicarbonate-extractable soil ortho-P positively correlated with plant mass of L. latifolium. A separate experiment demonstrated that L. latifolium has a narrow window of soil water potentials for optimal growth; greatest growth at -20 kPa with significantly declining growth at saturation and -400 kPa. Our data suggest that L. latifolium primarily invades wetlands because the high soil water content reduces tortuosity and allows efficient transport of nutrients to this sparsely rooted species. When soil moisture and/or the nutrient supplying capacity of the soil declines, plants with greater root density can out-compete L. latifolium. Monocultural stands of L. latifolium may be self-limiting in time as available nutrients, particularly P, are biocycled to drier upper soil layers. 相似文献
143.
We investigated the effects of erythritol on rats with streptozotocin- (STZ-) induced diabetes mellitus. Oral administration of erythritol [100, 200, or 400 mg (kg body weight)(-1) day(-1) for 10 days] to rats with STZ-induced diabetes resulted in significant decreases in the glucose levels of serum, liver, and kidney. Erythritol also reduced the elevated serum 5-hydroxymethylfurfural level that is glycosylated with protein as an indicator of oxidative stress. In addition, thiobarbituric acid-reactive substance levels of serum and liver and kidney mitochondria were dose-dependently lower in the erythritol-treated groups than in the control diabetic group. Furthermore, the serum creatinine level was reduced by oral administration of erythritol in a dose-dependent manner. These results suggest that erythritol affects glucose metabolism and reduces lipid peroxidation, thereby improving the damage caused by oxidative stress involved in the pathogenesis of diabetes. 相似文献
144.
Photocatalytic decomposition of gaseous acetone was studied with a fixed-bed annular reactor using TiO2 as the photocatalyst. The relation of UV light intensity to the reaction rate was found to be roughly first-ordered. The decomposition of acetone was obviously enhanced with increasing retention time. Removal of acetone was slightly increased with the relative humidity for experiments conducted with relative humidity below 20%. However, the removal of acetone was decreased drastically with relative humidity for experiments conducted with relative humidity greater than 20%. Decomposition of acetone was promoted considerably with increasing oxygen concentration for experiments conducted with oxygen less than 200,000 ppmv, yet the decomposition of acetone was kept relatively constant for experiments conducted with oxygen above 200,000 ppmv. Based on the mass balance for carbon species, the amount of organic intermediates formed for experiments conducted under various conditions were found to be minimal. Experimental results for the decomposition of gaseous acetone by UV/TiO2 process can be adequately described by the developed two-site Langmuir–Hinshelwood (L–H) kinetic model. 相似文献
145.
C.C. Young 《Soil biology & biochemistry》1984,16(4):377-380
A technique has been developed to extract soil phenolics by their adsorption onto resin, the separation of resin from soil, and desorption from the resin followed by high performance liquid chromatography (HPLC) analysis. Four representative phenolic acids, p-hydroxybenzoic, p-hydroxycinnamic, p-methoxybenzoic and 2,4-dimethoxybenzoic acids, were added to a subtropical soil (66 nmol g?1 soil) and recovered by extraction with Amberlite XAD-4 resin. The recovery efficiency of the added phenolics was greater using a flotation method to separate resin from soil than by a filtration method. The recoveries of p-hydroxybenzoic acid and p-hydroxycinnamic acid decreased with increasing extractant pH. Recoveries of p-methoxybenzoic acid and 2,4-dimethoxybenzoic acid increased slightly with increasing pH. The addition of NaCl to the XAD-4 resin extractant generally increased the recovery of phenolics by filtration but not by flotation. The recoveries of phenolics from the soil by extraction with XAD-4 resin were much greater than by alkaline extraction at pH 11. 相似文献
146.
Young JF Rosenvold K Stagsted J Nielsen JH Andersen HJ 《Journal of agricultural and food chemistry》2005,53(3):745-749
The present study investigates the combined effects of feed-induced increase in polyunsaturated fatty acids (PUFA) content and/or alpha-tocopherol content in pig muscles and preslaughter stress on cell integrity. Cell integrity was determined by plasma lactate dehydrogenase (LDH) activity, and antioxidative status of muscle was measured by activities of the antioxidative enzymes catalase, superoxide dismutase, and glutathione peroxidase. Preslaughter stress increased LDH activity, reflecting loss in cell membrane integrity independent of increased content of PUFA and/or alpha-tocopherol. However, feed-induced increase of PUFA decreased the LDH activity in plasma immediately after slaughter. Catalase activity in the muscle tissue increased as a consequence of the high-PUFA diet, which may indicate an increased demand caused by introduction of oxidative labile PUFA. 相似文献
147.
148.
Chulkyu Lee Young Joon Kim Sang-Bum Hong Hanlim Lee Jinsang Jung Yeo-Jin Choi Jungeun Park Ki-Hyun Kim Jai-Hoon Lee Ki-Joon Chun Hyun-Ho Kim 《Water, air, and soil pollution》2005,160(1-4):181-195
Ozone effects on Mediterranean forests were studied for 10 years in southern France. The aim of these studies was to understand the impact of the pollutant on foliar damage among Aleppo pine (Pinus halepensis Mill) and Arolla pine (Pinus cembra L) populations. During the summers of 2001 and 2002, ozone concentrations were measured using UV absorption analysers (4) and passive samplers (29) at two forest monitoring sites: Site 1 in the Nice coastal area for Aleppo pine and Site 2 in the Mercantour mountains for Arolla pine, in the vicinity of tree observation sites. AOT 40 values were quite high (25–33 ppm.h), especially in the Mercantour mountains, for the 5 months of measurement. Foliar damage (defoliation and discoloration) and specific symptoms (chlorotic mottle) were observed on 8 Aleppo pine and 13 Arolla pine plots. For Arolla pines, there was a significant correlation between defoliation and chlorotic mottles. There was also a correlation between mean ozone concentrations measured by passive samplers and chlorotic mottles. These correlations were less significant for Aleppo pine. 相似文献
149.
Taylor MK Young TM Butzke CE Ebeler SE 《Journal of agricultural and food chemistry》2000,48(6):2208-2211
2,4,6-Trichloroanisole (TCA) is the compound most often associated with cork taint in wines and has been shown to have a very low sensory threshold ( approximately 5 ng/L in wine). A supercritical fluid extraction (SFE) method for TCA in bark cork stoppers was developed with quantification via gas chromatography-mass spectrometry with selected ion monitoring. Supercritical carbon dioxide functioned as the extracting solvent, and temperature and pressure were optimized for the extraction. The method was validated using the stable isotope (2)H(5)-TCA as the internal standard. Recovery of TCA from spiked corks was found to be within 1-4% of the theoretical concentration with a coefficient of variation ranging from 2.6 to 9.7%. TCA levels in corks pulled from wines described as tainted by experienced judges ranged from 0.13 to 2.11 microg/g of cork. The SFE procedure offers a rapid, quantitative, nearly solvent-free, and automated method for the extraction of TCA from complex solid matrices such as cork. 相似文献
150.
Lee KW Kim YJ Kim DO Lee HJ Lee CY 《Journal of agricultural and food chemistry》2003,51(22):6516-6520
The contribution of each phytochemical to the total antioxidant capacity of apples was determined. Major phenolic phytochemicals of six apple cultivars were identified and quantified, and their contributions to total antioxidant activity of apples were determined using a 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assay and expressed as vitamin C equivalent antioxidant capacity (VCEAC). Average concentrations of major phenolics and vitamin C in six apple cultivars were as follows (mg/100 g of fresh weight of apples): quercetin glycosides, 13.20; procyanidin B(2), 9.35; chlorogenic acid, 9.02; epicatechin, 8.65; phloretin glycosides, 5.59; vitamin C, 12.80. A highly linear relationship (r (2) > 0.97) was attained between concentrations and total antioxidant capacity of phenolics and vitamin C. Relative VCEAC values of these compounds were in the order quercetin (3.06) > epicatechin (2.67) > procyanidin B(2) (2.36) > phloretin (1.63) > vitamin C (1.00) > chlorogenic acid (0.97). Therefore, the estimated contribution of major phenolics and vitamin C to the total antioxidant capacity of 100 g of fresh apples is as follows: quercetin (40.39 VCEAC) > epicatechin (23.10) > procyanidin B(2) (22.07) > vitamin C (12.80) > phloretin (9.11) > chlorogenic acid (8.75). These results indicate that flavonoids such as quercetin, epicatechin, and procyanidin B(2) rather than vitamin C contribute significantly to the total antioxidant activity of apples. 相似文献