全文获取类型
收费全文 | 1775篇 |
免费 | 82篇 |
国内免费 | 283篇 |
专业分类
2140篇 |
出版年
2023年 | 28篇 |
2022年 | 33篇 |
2021年 | 48篇 |
2020年 | 54篇 |
2019年 | 56篇 |
2018年 | 47篇 |
2017年 | 57篇 |
2016年 | 53篇 |
2015年 | 55篇 |
2014年 | 71篇 |
2013年 | 124篇 |
2012年 | 48篇 |
2011年 | 83篇 |
2010年 | 58篇 |
2009年 | 65篇 |
2008年 | 86篇 |
2007年 | 97篇 |
2006年 | 81篇 |
2005年 | 71篇 |
2004年 | 76篇 |
2003年 | 74篇 |
2002年 | 65篇 |
2001年 | 62篇 |
2000年 | 63篇 |
1999年 | 55篇 |
1998年 | 56篇 |
1997年 | 51篇 |
1996年 | 35篇 |
1995年 | 48篇 |
1994年 | 45篇 |
1993年 | 46篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 18篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 8篇 |
排序方式: 共有2140条查询结果,搜索用时 15 毫秒
51.
52.
在温室盆栽条件下,研究丛枝菌根(AM)真菌地表球囊霉(Glomus versiforme)对连作土壤中西瓜自根苗和嫁接苗生长、根系膜透性、丙二醛(MDA)含量和防御性酶活性的影响.结果表明: 接种AM真菌能显著增加西瓜自根苗和嫁接苗的生物量,提高根系活力,降低根系膜透性和MDA含量.接种AM真菌的自根苗地上部鲜质量、地上部干质量和根系活力分别增加了57.6%、60.0%和142.1%,而接种AM真菌的嫁接苗分别增加了26.7%、28.0%和11.0%;自根苗(C)、嫁接苗(G)、接种AM真菌自根苗(C+M)和接种AM真菌嫁接苗(G+M)的根系细胞膜透性为C>G>C+M>G+M,根系MDA含量为C>G>G+M>C+M.接种AM真菌能提高西瓜自根苗和嫁接苗根系的苯丙氨酸解氨酶(PAL)、过氧化氢酶(CAT)、过氧化物酶(POD)、几丁质酶和β 1,3 葡聚糖酶活性,而且接种AM真菌的西瓜自根苗和嫁接苗根系POD、PAL和β-1,3-葡聚糖酶活性的峰值比不接种的提前2周出现.接种AM真菌能激活西瓜自根苗和嫁接苗与抗逆性有关的防御性酶反应,使根系对逆境产生快速反应,从而提高其抗连作障碍的能力. 相似文献
53.
William G. Meikle Marie-Claude Bon Steve C. Cook Carlos Gracia Stefan T. Jaronski 《Biocontrol Science and Technology》2013,23(2):220-233
Two strains of Pseudomonas fluorescens were found contaminating a biopesticide used in a previous study against Varroa destructor infestations in honey bee hives. In that study, the biopesticide, a formulation of a fungal pathogen of arthropods, Beauveria bassiana, failed to have any negative impact on the mite infestation despite successful results in previous studies using uncontaminated batches of the same biopesticide. The objective of the present research was to determine whether the bacteria may have interfered with the infectivity and/or virulence of B. bassiana in a simplified system; positive results in that system would then provide a rationale for further work under more complex conditions. Galleria mellonella late instar larvae treated topically with both a bacterial suspension of 6.8 to 7.0×107 cfu/ml and a fungal suspension of 2.5×107 or 2.5×108 B. bassiana conidia/ml showed, in the case of one of the bacterial strains, significantly increased survivorship compared to larvae treated with just the B. bassiana suspension. When larvae were immersed in a bacterial suspension prior to application of B. bassiana suspension using a spray tower, a significant positive effect of the same P. fluorescens strain on larval survivorship was observed at 2.5×108 conidia/ml. Neither the bacterial suspensions alone nor blank control solutions had any effect on larval survivorship. These results show that an interaction between the bacteria and the pathogen may explain some of the results from the prior field trial. 相似文献
54.
Nitrogenase catalyzes not only the reduction of N2 to NH3 but also the reduction of C2H2 to C2H4 and H+ ion to H2 gas, etc. The detailed mechanism of the nitrogenase reaction is not clear. We have prepared monoclonal antibodies against Component I nitrogenase of A. vinelandii and examined the effects of antibodies on the nitrogenase reactions. A monoclonal antibody designated MA-1 inhibited C2H2 reduction activity strongly but did not inhibit H2 evolution activity. MA-2, on the contrary, inhibited only H2 evolution activity. MA-8 inhibited both C2H2 reduction and H2 evolution activity to the same extent. 相似文献
55.
《Bioscience, biotechnology, and biochemistry》2013,77(2):362-363
Chitinase treatment of a commercial laminarioligosaccharide preparation from a mushroom resulted in a loss of previously reported elicitor activity in rice cells, indicating that the activity was attributable not to the laminarioligosaccharide but rather to the contaminating chitin fragments. This suggests that the elicitor activity of laminarioligosacchraides from such sources containing chitinaceous substances should be carefully interpreted. 相似文献
56.
Toshiya Kamikado Ching-Fun Chang Shigeo Murakoshi Akira Sakurai Saburo Tamura 《Bioscience, biotechnology, and biochemistry》2013,77(4):833-836
Two lignans were isolated from leaves of Magnolia kobus DC. as growth inhibitors on silkworm larvae and structurally elucidated as sesamin (I) and kobusin (II) which has been hitherto unknown. 相似文献
57.
《Bioscience, biotechnology, and biochemistry》2013,77(2):414-416
We have already shown that major rice diterpene phytoalexin, momilactone A, was detoxified by Magnaporthe oryzae. We report here the identification by NMR, MS, and chemical synthesis of 3,6-dioxo-19-nor-9β-pimara-7,15-diene (1) as the degradation intermediate. Compound 1 exhibited similar antifungal activity to that of momilactone A, indicating 1 to be a precursor of possible detoxified compounds. 相似文献
58.
Katsunori Teranishi 《Luminescence》2016,31(2):594-599
Mycena chlorophos, which is primarily distributed in Southeast Asia, is a luminous fungus that emits a bright green light from its pileus for about 2 days at approximately 20°C and high relative humidity. The distribution of bioluminescent tissues in the whole pileus and its sections was heterogeneous. The light intensity in the cap and the upper region of the gill was greater than that in the lower region of the gill. At the microscopic level, the light was predominantly emitted from the membranes of hymenium and basidia cells on the gill. The emission was both cell and region specific. The luminescence system was localized in the cell membrane, and a part of the system was on the cell membrane surface. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
59.
60.
Jeremy M. Cohen David J. Civitello Matthew D. Venesky Taegan A. McMahon Jason R. Rohr 《Global Change Biology》2019,25(3):927-937
Climate change might drive species declines by altering species interactions, such as host–parasite interactions. However, few studies have combined experiments, field data, and historical climate records to provide evidence that an interaction between climate change and disease caused any host declines. A recently proposed hypothesis, the thermal mismatch hypothesis, could identify host species that are vulnerable to disease under climate change because it predicts that cool‐ and warm‐adapted hosts should be vulnerable to disease at unusually warm and cool temperatures, respectively. Here, we conduct experiments on Atelopus zeteki, a critically endangered, captively bred frog that prefers relatively cool temperatures, and show that frogs have high pathogen loads and high mortality rates only when exposed to a combination of the pathogenic chytrid fungus (Batrachochytrium dendrobatidis) and high temperatures, as predicted by the thermal mismatch hypothesis. Further, we tested various hypotheses to explain recent declines experienced by species in the amphibian genus Atelopus that are thought to be associated with B. dendrobatidis and reveal that these declines are best explained by the thermal mismatch hypothesis. As in our experiments, only the combination of rapid increases in temperature and infectious disease could account for the patterns of declines, especially in species adapted to relatively cool environments. After combining experiments on declining hosts with spatiotemporal patterns in the field, our findings are consistent with the hypothesis that widespread species declines, including possible extinctions, have been driven by an interaction between increasing temperatures and infectious disease. Moreover, our findings suggest that hosts adapted to relatively cool conditions will be most vulnerable to the combination of increases in mean temperature and emerging infectious diseases. 相似文献