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排序方式: 共有482条查询结果,搜索用时 15 毫秒
471.
472.
Soil microhabitats and their heterogeneity are often considered to be among the most important factors affecting soil biotic
communities. The microbial community has become one of the most important links in soil nutrient cycles and trophic components
due to its role in biological processes, spatial and temporal dynamics, and physiological adaptation. Sandy-soil desert systems
are characterized by fast water infiltration during the rainy season, high salinity, and low moisture availability in the
upper soil layers. Plants have developed different ecophysiological adaptations in order to cope with this harsh environment.
The Tamarix aphylla is known to be one of the most commonly adapted plants, exhibiting a mechanism for secretion of excess salts as aggregates
through its leaves. These leaves aggregate beneath the plant, creating ‘islands of salinity’. Soil biotic components are,
therefore, exposed to extreme abiotic stress conditions in this niche. The goal of this study was to examine the effect of
T. aphylla on the live/dead bacterial population ratio on a spatial and temporal scale. The results emphasize the effect of abiotic
factors, which changed on temporal as well as spatial scales, and also on the size of the active soil bacterial community,
which fluctuated between 1.44% and 25.4% in summer and winter, respectively. The results of this study elucidate the importance
of moisture availability and the ‘island-of-salinity’ effect on the active microbial community in a sandy desert system. 相似文献
473.
Yu-Pei Chen Jian-Hua Yin Wen-Fei Li Han-Jie Li Dong-Ping Chen Cui-Juan Zhang Jia-Wei Lv Ya-Qin Wang Xiao-Min Li Jun-Yan Li Pan-Pan Zhang Ying-Qin Li Qing-Mei He Xiao-Jing Yang Yuan Lei Ling-Long Tang Guan-Qun Zhou Yan-Ping Mao Chen Wei Ke-Xu Xiong Hong-Bo Zhang Shi-Da Zhu Yong Hou Ying Sun Michael Dean Ido Amit Kui Wu Dong-Ming Kuang Gui-Bo Li Na Liu Jun Ma 《Cell research》2020,30(11):1024
474.
Should attractive males have more sons? 总被引:5,自引:0,他引:5
It is often argued that females with attractive partners shouldproduce more sons because these sons will inherit their father'sattractiveness. Numerous field and laboratory studies have addressedthis hypothesis, with inconsistent results, but there is surprisinglylittle theoretical work on the topic. Here, we present an extensiveinvestigation of the link between male attractiveness and offspringsex ratios, using evolutionary, individual-based computer simulations.In situations where sexual selection leads to the stable exaggerationof a costly male trait and a costly female preference, we findthat females with attractive partners produce more sons thanfemales with unattractive partners. This same qualitative patternis seen for a wide range of different models, with discreteor continuous variation in the male trait, under Fisherian orgood-genes sexual selection and for abrupt or gradual sex ratioadjustment. However, in all simulations, it takes a huge numberof generations to evolve, suggesting that selection acting onsex ratio adjustment is weak. Our models ignore many potentialcosts and constraints associated with manipulation, which impliesthat selection may be weaker still in natural populations. Theseresults may explain why published evidence for sex ratio biasin relation to male attractiveness is mixed. 相似文献
475.
S.J. May A. Rahat C.C. Blackwell C.J. MacCallum R.P. Brettle D.M. Weir 《FEMS microbiology letters》1989,47(6-7):377-382
Abstract Strains of Escherichia coli isolated from urine of secretors (242) and non-secretors (121) were compared for their serotype and their ability to express mannose-sensitive (MS) haemagglutinins and mannose-resistant (MR) haemagglutinins and to produce haemolysin. The results of the survey refuted our hypothesis that strains with characteristics associated with virulence, those with MR haemagglutinins and/or haemolysins, would be isolated more frequently from non-secretors. MR haemagglutinins were detected among 36.4% of isolates from secretors and 27.3% of isolates from non-secretors. Haemolysin production was detected among 19.8% of isolates from secretors and 12.5% of isolates from non-secretors. Both MR haemagglutinins and haemolysin were detected only on 12.4% of strains from secretors and 6.7% of strains from non-secretors. 相似文献
476.
Health professions are perceived by the Arab minority in Israel as a desired path of education and employment. Arabs in Israel are thus highly represented in these professions, especially pharmacy. This study analyses the unique ethnic and gender composition of pharmacists in Israel and explores their career experiences and perceptions. Both quantitative and qualitative methodologies are employed. The findings reflect dual marginality in the pharmacy profession in Israel, that is currently both female and ethnic-dominated. This situation is described in the Arab pharmacists’ stories, that delineate the disparity between their aspirations when starting their careers and their hardships after working for several years as pharmacists. Arabs in Israel face unique difficulties in the labour market. Many choose the health professions, including pharmacy, as a path of mobility. Pharmacy, however, is perceived as a niche (ethnic and female-dominated) profession in Israel. Hence, its practitioners suffer from devaluation in wage and prestige. 相似文献
477.
Species of the epiphytic fungus Pseudozyma are not pathogenic to plants and can be used as biocontrol agents against plant pathogens. Deciphering how they induce plant defense might contribute to their use for plant protection and expand our understanding of molecular plant–pathogen interactions. Here we show that Pseudozyma aphidis isolate L12, which is known to induce jasmonic acid- and salicylic acid-independent systemic resistance, can also activate local and systemic resistance in an ethylene-independent manner. We also show that P. aphidis localizes exclusively to the surface of the plant leaf and does not penetrate the mesophyll cells of treated leaves. We thus propose that P. aphidis acts via several mechanisms, and is an excellent candidate biocontrol agent. 相似文献
478.
S J May A Rahat C C Blackwell C J MacCallum R P Brettle D M Weir 《FEMS microbiology immunology》1989,1(6-7):377-381
Strains of Escherichia coli isolated from urine of secretors (242) and non-secretors (121) were compared for their serotype and their ability to express mannose-sensitive (MS) haemagglutinins and mannose-resistant (MR) haemagglutinins and to produce haemolysin. The results of the survey refuted our hypothesis that strains with characteristics associated with virulence, those with MR haemagglutinins and/or haemolysins, would be isolated more frequently from non-secretors. MR haemagglutinins were detected among 36.4% of isolates from secretors and 27.3% of isolates from non-secretors. Haemolysin production was detected among 19.8% of isolates from secretors and 12.5% of isolates from non-secretors. Both MR haemagglutinins and haemolysin were detected only on 12.4% of strains from secretors and 6.7% of strains from non-secretors. 相似文献
479.
Erich Kessler Volker A. R. Huss Menachem Rahat 《Plant Systematics and Evolution》1988,160(3-4):241-246
46 strains ofChlorella, identified by physiological and biochemical characters, were examined for their ability to form stable symbioses with aposymbioticHydra viridis. It was found to be a species-specific characteristic. Among the 15 taxa studied, onlyC. saccharophila var.ellipsoidea, C. saccharophila var.saccharophila, C. fusca var.vacuolata, C. kessleri, C. luteoviridis, andC. protothecoides formed stable symbioses withHydra viridis. Among the 11 known physiological and biochemical characters of theseChlorella species, only acid tolerance seems to be correlated with symbiosis: All symbiotic species are capable of growing at or below pH 4.0. 相似文献
480.