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831.
通过对香港地区46个代表性土壤表层样品的8种有机氯农药(OCPs)和6种多氯联苯(PCBs)含量及其组成的分析,初步揭示了香港土壤中有机氯化合物的分布及残留情况。研究结果表明:香港土壤中有机氯农药主要是一些相对难降解的化合物如β-HCH和P,P’-DDE,两者在土壤中的平均含量分别为6.12μg kg^-1和0.41μg kg^-1,远低于荷兰的土壤修复目标值。PCBs在土壤中的检出率很低,且含量基本均小于0.1/μg kg^-1。此外。六六六(HCH)在目前的残留状态下,可能受到土壤pH(KCl)和总有机碳(TOC)的影响,而其他有机氯农药的含量并未呈现出与土壤的理化性质的相关性。 相似文献
832.
Genetic variability in Macadamia 总被引:1,自引:0,他引:1
Mallikarjuna K. Aradhya Liana K. Yee Francis T. Zee Richard M. Manshardt 《Genetic Resources and Crop Evolution》1998,45(1):19-32
A genetic variability analysis involving 45 accessions of Macadamia including four species, M. integrifolia, M. tetraphylla, M. ternifolia, and M. hildebrandii and a wild relative, Hicksbeachia pinnatifolia was performed using eight enzyme systems encoded by 16 loci (Gpi-1 and 2, Idh-1 and 2, Lap, Mdh-1, 2, and 3, 6Pgd-2, Pgm-2 and 3, Tpi-1 and 2, Ugpp-1, 2, and 3). Forty-three accessions possessed distinct isozyme fingerprints indicating a high level of genetic variation. Examination of multivariate relationships among accessions using a cluster analysis resulted in the identification of four clusters, two of which contained one accession each representing H. pinnatifolia and M. hildebrandii. All Hawaiian cultivars were included in two sub-clusters within the largest cluster, which encompassed all the M. integrifolia and three M. ternifolia accessions, suggesting that: (1) the Hawaiian cultivars must have originated from at least two genetically diverse ancestral populations and (2) M. ternifolia may be a conspecific variant of M. integrifolia. Macadamia tetraphylla has diverged marginally from the M. integrifolia and M. ternifolia complex suggesting that these taxa represent a species complex. The different measures of genetic variability such as mean number of alleles per locus, polymorphic index, and observed and expected levels of heterozygosity, indicated significant levels of genetic variation in the Macadamia collection. 相似文献
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834.
The formation of social groups has important impacts on fitness for many animal species, with differences in group compositions resulting in a range of fitness outcomes for individuals. Recent interest in mixed‐species grouping, which extends from a large body of literature invested in understanding single‐species grouping, highlights novel complexities of group formation which relate to phenotypic, behavioural and physiological differences that naturally exist between species. Among fishes, mixed‐species shoaling is a common form of social grouping behaviour displayed across a range of marine and freshwater ecosystems. Research explaining mixed‐species shoaling shows some overlap with explanations for single‐species shoaling; however, it also demonstrates that distinct differences between species give rise to unique cost‐benefit trade‐offs which need to be incorporated into conceptual models of mixed‐species shoaling behaviour. Unique predation related trade‐offs may arise from inefficiency of the confusion effect, variation in vigilance between species and unequal species‐preferences shown by predators, whilst unique foraging‐related trade‐offs may arise from diet partitioning, variations in foraging behaviour and differences in competitive abilities between species. We review the literature on fitness outcomes associated with mixed‐species shoaling and present a new theoretical framework to explain the cost‐benefit trade‐offs for individuals within mixed‐species shoals. The framework incorporates both trade‐offs arising from differences between species and those arising from group size, the former having been largely ignored due to a focus on single‐species shoaling. Our framework is designed to inform future research striving to explain mixed‐species shoaling behaviour. 相似文献
835.
Stefanie M. Colombo Zeyu Zhang David F. Wong Zhirun Yuan 《Aquaculture Nutrition》2020,26(4):1353-1368
The objective of this study was to evaluate hydrolysis lignin (H‐lignin), derived from wood biomass, as a multifunctional component of aquafeeds. Atlantic salmon (28.8 ± 1.1 g) were fed diets for 16 weeks, which included two H‐lignin types (HL1 and HL2) at 15, 30 or 50 g/kg (wt/wt) or a control diet (no added H‐lignin). HL1 was extracted with water such that no soluble sugar and oligosaccharides remain, while HL2 contains a higher fraction of water‐soluble sugars and oligosaccharides. Pellet durability and density were measured. After 16 weeks, salmon were measured for weight and length, and whole carcass, hindgut and digesta contents were sampled. Pellet durability increased from the control to 30 g/kg H‐lignin but decreased at 50 g/kg. Salmon fed diets with HL1 at 15 and 30 g/kg showed higher weight gain and lower feed conversion ratio compared with salmon fed the control diet and 50 g/kg HL1. There were no significant differences in whole‐body composition or intestinal morphology. Microbial characterization (16S) revealed lower abundance of Proteobacteria, higher abundance of Mycoplasmataceae and increasing Lactobacillaceae abundance with higher HL1 inclusion. This study demonstrates that HL1 (at 15 and 30 g/kg) shows potential as a functional feed additive for salmon. 相似文献
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837.
838.
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