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991.
Denitrification and total N losses were quantified from an irrigated field cropped to maize and wheat, each receiving urea at 100 kg N ha-1. During the maize growing season (60 days), the denitrification loss measured directly by acetylene inhibition-soil cover method amounted 2.72 kg N ha-1 whereas total N loss measured by 15N balance was 39 kg ha-1. Most (87%) of the denitrification loss under maize occurred during the first two irrigation cycles. During the wheat growing season (150 days), the denitrification loss directly measured by acetylene inhibition-soil cover and acetylene inhibition-soil core methods was 1.14 and 3.39 kg N ha-1, respectively in contrast to 33 kg N ha-1 loss measured by 15N balance. Most (70-88%) of the denitrification loss under wheat occurred during the first three irrigation cycles. Soil moisture and NO
3
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-N were the major factors limiting denitrification under both crops. Higher N losses measured by 15N balance than C2H2 inhibition method were perhaps due to underestimation of denitrification by C2H2 inhibition method and losses other than denitrification, most probably NH3 volatilization. 相似文献
992.
Witcher Derrick R. Hood Elizabeth E. Peterson Dave Bailey Michele Bond Diane Kusnadi Ann Evangelista Roque Nikolov Zivko Wooge Cynthia Mehigh Richard Kappel William Register James Howard John A. 《Molecular breeding : new strategies in plant improvement》1998,4(4):301-312
We have generated transgenic maize seed containing -glucuronidase(GUS) for commercial production. While many other investigators have demonstrated the expression of GUS as a scoreable marker, this is one of the first cases where a detailed characterization of the transgenic plants and the protein were performed which are necessary to use this as a commercial source of GUS. The recombinant -glucuronidase was expressed at levels up to 0.7% of water-soluble protein from populations of dry seed, representing one of the highest levels of heterologous proteins reported for maize. Southern blot analysis revealed that one copy of the gene was present in the transformant with the highest level of expression. In seeds, the majority of recombinant protein was present in the embryo, and subcellular localization indicated that the protein was dispersed throughout the cytoplasm. The purified recombinant -glucuronidase (GUS) was compared to native -glucuronidase using SDS-PAGE and western blot analysis. The molecular mass of both the recombinant and native enzymes was 68 000 Da. N-terminal amino acid sequence of the recombinant protein was similar to the sequence predicted from the cloned Escherichia coli gene except that the initial methionine was cleaved from the recombinant GUS. The recombinant and native GUS proteins had isoelectric points (pI) from 4.8 to 5.0. The purified proteins were stable for 30 min at 25, 37, and 50 ° C. Kinetic analysis of the recombinant and native GUS enzymes using 4-methylumbelliferyl glucuronide (MUG) as the substrate was performed. Scatchard analysis of these data demonstrated that the recombinant enzyme had a Km of 0.20 mM and a Vmax of 0.29 mM MUG per hour, and the native enzyme had a Km and Vmax of 0.21 mM and 0.22 mM/h respectively. Using D-saccharic acid 1,4-lactone, which is an inhibitor of -glucuronidase, the Ki of the native and recombinant enzymes was determined to be 0.13 mM. Thus, these data demonstrate that recombinant GUS is functionally equivalent to native GUS. We have demonstrated the expression of high levels of GUS can be maintained in stable germlines and have used an efficient recovery system where the final protein product, GUS, has been successfully purified. We describe one of the first model systems for the commercial production of a foreign protein which relies on plants as the bioreactor. 相似文献
993.
干旱胁迫下大豆与玉米叶片光破坏的防御 总被引:7,自引:1,他引:6
随干旱强度的增加,大豆叶片光呼吸速率(Pr)降低的幅度小于Pn,使Pr/Pn比率升高。在轻度及中度干旱下,PSII光化学效率(Fv/Fm)能在暗置后较快地恢复。随干旱强度的增加,叶片光化学猝灭系数下降,非光化学猝死系数升高。干旱使叶片β-胡萝卜素及紫黄质含量下降,而玉米黄质含量(Z)与叶黄素库增加。与大豆相比,玉米在干旱条件下具有较高的Z含量和较大的叶黄素库。 相似文献
994.
Samples of wheat (n = 25) and maize (n = 30) for animal consumption, collected in 1997 after harvest from western Romania,
were analyzed by enzyme immunoassays for mycotoxin contamination. Toxins analyses included deoxynivalenol (DON), 3-acetylDON,
15- acetylDON, fusarenone X (FX), T-2 Toxin (T-2), diacetoxyscirpenol (DAS), zearalenone (ZEA), fumonisin B1 (FB1), aflatoxin
B1 (AFB1), ochratoxin A (OA), and citrinin (CT). DON and acetylDONs were the major contaminants in wheat (100%) and maize
(46%). Median values for DON, 3-acetylDON, and 15-acetylDON were 880 μg kg-1, 66 μg kg- 1, and 150 μg kg-1 in wheat, and 890
μg kg-1, 180 μg kg-1, and 620 μg kg- 1 in maize, respectively. Additionally, 3,15-diacetylDON was detected in some samples
by HPLC-EIA analysis. All samples were negative for FX (<150 μg kg-1). T-2 was found in wheat (n = 6) and maize (n = 1) at
levels between 13 and 63 μg kg- 1. DAS (2.6 μg kg-1) was found in one maize sample. ZEA occurred in all wheat and in four
maize samples, median values were 10 μg kg-1 and 250 μg kg-1, respectively. One maize sample contained FB1 (140 μg kg-1).
All samples were AFB1-negative (<4 μg kg-1). OA was found in one wheat sample (37 μg kg- 1), CT was found in one maize sample
(580 μg kg- 1). This first reported natural occurrence of a range of mycotoxins in Romanian feeding stuff shows that DON and
acetyl DONs may be present at levels which may affect animal production.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
995.
996.
玉米抗旱品种的形态解剖学研究 总被引:14,自引:1,他引:13
在严格控水的防雨棚内,比较 抗旱筛选和省区试后表现抗旱高产的玉米新品种鲁玉14号和对照掖单2号的殂态解剖结构,结果表明:玉米抗旱与不抗旱的差异并非品种的结构决定,而在抗旱性结构指标上存在差异。抗旱品种的叶片厚,气孔指数及气孔数/mm^2大,侧根发生早、发生能力强可作为玉米抗旱育种与栽培的形态结构指标。 相似文献
997.
998.
In greening maize leaves δ-aminolevulinic acid (ALA) was not formed from succinyl-CoA and glycine as shown by the incorporation of [14C]-labeled 相似文献
999.
Polysaccharides of root-cap slime from five maize varieties 总被引:1,自引:0,他引:1
Kenneth Wright 《Phytochemistry》1975,14(3):759-763
Radioactive root-cap slime from five maize varieties consisted of a mixture of neutral, weakly-acidic and acidic polymers. The distribution of radioactivity between monosaccharides of these components showed that the slimes were essentially the same but that preparations, even those made at different times from the same variety, contained variable proportions of glucose. Results obtained with different maize varieties can therefore be considered together. 相似文献
1000.
The main uronic acid product of acid hydrolysis of maize root-cap polysaccharide ran marginally behind galacturonic acid on paper electrophoresis at pH 3·5. Material from both radioactive and non-radioactive slime preparations was used to provide evidence that this was an oligomeric partial hydrolysis product containing both galacturonic acid and glucose. The consequences of this upon the structure of the slime are discussed. 相似文献