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排序方式: 共有620条查询结果,搜索用时 31 毫秒
611.
Chun-yue Wang Yan-rong Li Chen Pan Jian Chen Wei Jiang Wei-nan Li Xiao-lin Zhang Zhi Liao Xiao-jun Yan 《Biochemistry and Biophysics Reports》2021
Histidine-containing dipeptides (HCDs) are a family of non-protein, nitrogen-containing compounds with multiple physiological roles and are mainly present in excitable tissues of vertebrates. The distribution of HCDs in various animal species has been the subject of study for nearly 100 years. The aim of this research was to determine the content of the HCDs in the aquatic species collected from the Zhoushan fishing ground of the East China Sea. Using LC-MS/MS technology, the occurrence of carnosine, anserine, and homocarnosine in skeletal muscle of 38 aquatic species (26 teleosts, 6 molluscs, and 6 crustaceans) and chicken breast was investigated. Of the 38 aquatic species examined, 24 species (23 teleosts and 1 mollusc) contained considerable amounts (>5 ng/g wet tissue) of HCDs, and anserine was the major component of HCDs in their skeletal muscles. Only 5 teleosts contained homocarnosine. Most invertebrates, with the exception of the sepia Uroteuthis chinensis, did not contain HCDs. The present findings greatly expand the HCD distribution data and provide insight into understanding the roles of HCDs in different animals and a nutritional assessment for marine aquatic species. 相似文献
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盾叶薯蓣自然变异类型间的比较研究 总被引:7,自引:0,他引:7
对取自云南期纳的二倍体和三倍体盾叶薯蓣植株以及重庆城口的四倍体植株进行了形态学、染色体数目及同工酶的比较研究。结果表明,这3种类型植株在叶片形态上有明显的差异。二倍体的染色体数目是2n=2x=20,三倍体为2n=3x=30,四倍体为2n=4x=40;酯酶(EST)和超氧化物歧化酶(SOD)酶谱显示,3种类型植株之间具有明显的相关性,但多倍体较二倍体的酶带条数少且着色浅。这些差异除了有地理分布不同的因素外,倍性的不同也是很重要的因素。 相似文献
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Pollen longevity in seven Potamogeton species representing different pollination systems (anemophily, epihydrophily and hydroautogamy) was assessed both under
aerial condition and in contact with water to investigate how water impacts the sexual reproduction in these aquatic taxa.
Stainability of pollen with MTT was considered as an indicator of pollen viability. The half-life of pollen longevity was
calculated using exponential decay regression. Overall, pollen viability decreased relatively rapidly with time. Pollen grains
of obligate anemophilic species had lower initial viability and shorter half-lives than those of facultative anemophilic species.
Pollen in these latter species may take more time to reach the stigma. The pollen of Potamogeton may be categorized as partially hydrated pollen owing to its generally spherical shape and lack of furrows, rapid loss of
viability, and fast pollen tube initiation. The half-life is positively correlated with pollen size. Smaller-sized grains
are at greater risk of desiccation than larger grains. In contrast with the situation observed in most terrestrial angiosperms,
contact with water increases pollen longevity in Potamogeton species. In our present study the half-lives of pollen longevity of Potamogeton species in which the pollen had come into contact with water (mean of 10.65 h) were markedly higher than those under aerial
conditions (mean of 5.79 h, t = 2.622, P = 0.039). The results of our study contradict a widely held belief that water is detrimental to pollen viability in angiosperms
and furthermore indicate that close proximity to water results in selection for wettability. The transition to a hydrated
status together with its morphology, make Potamogeton pollen more adapted to the aquatic environment and thus serves to ensure reproductive process. Results of our present study
may have direct implications for understanding the evolution of the sexual reproductive system in aquatic angiosperms. 相似文献
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Shuai Lu Xi-xiu Xie Lei Zhao Bin Wang Jie Zhu Ting-rui Yang Guang-wen Yang Mei Ji Cui-ping Lv Jian Xue Er-hei Dai Xi-ming Fu Dong-qun Liu Lun Zhang Sheng-jie Hou Xiao-lin Yu Yu-ling Wang Hui-xia Gao Rui-tian Liu 《Cell reports》2021,34(4):108666
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619.
房室结多径路在临床中常见,其食道电生理有较典型特征,如多种频率心动过速。我们发现一例食道调搏存在两种频率心动过速患者,第一次在右延伸处成功慢径改良后较长时间不能发现另一条慢径存在,40分钟后另一条慢径才表现并于左延长处成功消融。提示如食道电生理发现存在多径路时心内电生理一定要多次重复检查,必要时延长观察时间,力争一次完整消融多条径路。 相似文献
620.
Feng Li Xiang-yun Zeng Chang-hua Wu Zhi-peng Duan Yan-mao Wen Guo-ru Huang Xiao-lin Long Min-Jian Li Man-Jie Li Jiang-Yu Xu 《Biological trace element research》2013,155(2):301-313
Sediments from 14 stations in the Foshan Waterway, a river crossing the industrial district of Guangdong Province, South China, were sampled and subsequently analyzed. The 14 stations were selected for the pollution discharging features of the river, such as the hydrology, the distribution of pollution sources, and the locations of wastewater outlets. The ecological risks were assessed, and the pollution sources were identified to provide valuable information for environmental impact assessment and pollution control. The spatial variability was high and the range were (in milligrams per kilogram dry weight): Pb, 46.0~382.8; Cu, 33.7~ 482.3; Zn, 62.2~1,568.7; Ni, 28.5~130.7; Cr, 34.7~1,656.1; Cd, 0.50~8.53; Hg, 0.02~8.27; and As, 5.77~66.09. The evaluation results of enrichment factor and potential ecological risk index indicate that the metal pollution in the surface and bottom sediments were severely polluted and could pose serious threat to the ecosystem in most stations. Although the hazard levels of the trace element differed among the stations, Hg was the most serious pollutant in all stations. The results of principal component analysis (PCA) show that the discharge of industrial wastewater is the most important polluting factor whereas domestic sewage, which contains a large amount of organic substances, accelerates metal deposition. And potential pollution sources were identified by the way of integrating the analysis results of PCA and data gained from the local government. Therefore, the conclusion is drawn that Foshan Waterway is seriously polluted with trace elements, both in the surface sediment (0 to 20 cm) and the bottom sediments (21 to 50 cm) are contaminated. 相似文献