全文获取类型
收费全文 | 601篇 |
免费 | 41篇 |
国内免费 | 3篇 |
专业分类
林业 | 28篇 |
农学 | 13篇 |
基础科学 | 2篇 |
159篇 | |
综合类 | 141篇 |
农作物 | 26篇 |
水产渔业 | 36篇 |
畜牧兽医 | 202篇 |
园艺 | 6篇 |
植物保护 | 32篇 |
出版年
2023年 | 5篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 16篇 |
2013年 | 21篇 |
2012年 | 30篇 |
2011年 | 32篇 |
2010年 | 25篇 |
2009年 | 11篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 22篇 |
2005年 | 34篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 19篇 |
2001年 | 22篇 |
2000年 | 23篇 |
1999年 | 21篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有645条查询结果,搜索用时 0 毫秒
641.
Yee-Shian Wong Soon-An Ong Tjoon-Tow Teng L. Nabilah Aminah Kasthuri Kumaran 《Water, air, and soil pollution》2012,223(7):3775-3781
Staphylococcus cohnii ssp. was found to produce a bioflocculant with high flocculating activity for kaolin suspension. Using optimized culture conditions, a flocculating activity of 70.3?% at a bioflocculation concentration of 0.3?mg/L at pH 7 with Ca2+ as the cation and 88.9?% in 1.2?mg/L of bioflocculant concentration for Al3+ as the cation was obtained for bacteria that were incubated at temperature of 40?°C for 2-day incubation period. It was found to be effective for flocculation of a kaolin suspension over weakly acidic pH (6?C8); divalent and trivalent (Ca2+ and Al3+) enhanced the flocculating activity. This bioflocculant possesses a good flocculating activity, which can be promoted by the addition of trivalent and bivalent cations in kaolin suspension. 相似文献
642.
毛白杨根系分布的研究 总被引:13,自引:1,他引:13
对沙地上不同年龄毛白杨人工林的根系,从形态、数量和分布密度3个方面进行了调查研究。结果表明,其根系为水平斜生复合根型,14a生林木根系的分布深度可达4.5m,水平根幅达8m左右。以重量划分7,9,14a生林分的根系,分别集中在0 ̄60cm、0 ̄100cm和0 ̄100cm土层内,占根系总重的86%以上,树木周围2.0m范围内根系的重量占总根量的80%以上。以根系长度衡量,整个林地内根系分布较均匀,0 相似文献
643.
Juvenile Epinephelus coioides were exposed to three nominal concentrations (8, 32, 128 mg wet sediments L?1) of suspended sediments (SS) from Port Shelter (PS), Mirs Bay (MB) and Victoria Harbour (VH) for 10 and 30 days using semi‐static system. Sediments from VH contained higher concentrations of Cu and polycyclic aromatic hydrocarbons (PAHs) than sediments from PS and MB. Gill damages including lamellar blood sinus dilation and vascular congestion were prevalent after just 10 days of exposure to SS. Fish exposed to SS at the highest concentration of 128 mg L?1 showed higher incidence of lamellar aneurism. Hyperplasia in the base of lamellae was recorded in fish that had been exposed to contaminated SS from VH. Significant increases in the density of chloride cells and mucous cells were found on the gills of fish that had been exposed to 128 mg L?1 of SS from PS. Clogging of gills by SS produced hypoxic‐like responses in fish. Polluted sediments from VH produced addictive or synergistic effects between SS and chemical contaminants on fish. 相似文献
644.
黄梓勇 《湖南农业大学学报(自然科学版)》2008,(2)
刘向之《诗经》学家法,前人每有论及。然其论据及研究方法,均仍有可改善之处。本文从家学、异文比较、《诗》说比较三方面,考论刘向之《诗》学家法,以图全面分析刘向《诗》学家法的问题,并希望由此而于两汉《诗》学研究有所裨益。 相似文献
645.
J. Jane Y. Y. Chen L. F. Lee A. E. McPherson K. S. Wong M. Radosavljevic T. Kasemsuwan 《Cereal Chemistry》1999,76(5):629-637
Structures and properties of starches isolated from different botanical sources were investigated. Apparent and absolute amylose contents of starches were determined by measuring the iodine affinity of defatted whole starch and of fractionated and purified amylopectin. Branch chain-length distributions of amylopectins were analyzed quantitatively using a high-performance anion-exchange chromatography system equipped with a postcolumn enzyme reactor and a pulsed amperometric detector. Thermal and pasting properties were measured using differential scanning calorimetry and a rapid viscoanalyzer, respectively. Absolute amylose contents of most of the starches studied were lower than their apparent amylose contents. This difference correlated with the number of very long branch chains of amylopectin. Studies of amylopectin structures showed that each starch had a distinct branch chain-length distribution profile. Average degrees of polymerization (dp) of amylopectin branch chain length ranged from 18.8 for waxy rice to 30.7 for high-amylose maize VII. Compared with X-ray A-type starches, B-type starches had longer chains. A shoulder of dp 18–21 (chain length of 6.3–7.4 nm) was found in many starches; the chain length of 6.3–7.4 nm was in the proximity of the length of the amylopectin crystalline region. Starches with short average amylopectin branch chain lengths (e.g., waxy rice and sweet rice starch), with large proportions of short branch chains (dp 11–16) relative to the shoulder of dp 18–21 (e.g., wheat and barley starch), and with high starch phosphate monoester content (e.g., potato starch) displayed low gelatinization temperatures. Amylose contents and amylopectin branch chain-length distributions predominantly affected the pasting properties of starch. 相似文献