全文获取类型
收费全文 | 18635篇 |
免费 | 1610篇 |
国内免费 | 2125篇 |
出版年
2024年 | 13篇 |
2023年 | 286篇 |
2022年 | 335篇 |
2021年 | 1046篇 |
2020年 | 814篇 |
2019年 | 945篇 |
2018年 | 895篇 |
2017年 | 647篇 |
2016年 | 866篇 |
2015年 | 1264篇 |
2014年 | 1482篇 |
2013年 | 1562篇 |
2012年 | 1885篇 |
2011年 | 1704篇 |
2010年 | 1053篇 |
2009年 | 906篇 |
2008年 | 1025篇 |
2007年 | 928篇 |
2006年 | 752篇 |
2005年 | 645篇 |
2004年 | 500篇 |
2003年 | 402篇 |
2002年 | 363篇 |
2001年 | 257篇 |
2000年 | 240篇 |
1999年 | 232篇 |
1998年 | 151篇 |
1997年 | 153篇 |
1996年 | 133篇 |
1995年 | 121篇 |
1994年 | 106篇 |
1993年 | 84篇 |
1992年 | 104篇 |
1991年 | 64篇 |
1990年 | 75篇 |
1989年 | 58篇 |
1988年 | 50篇 |
1987年 | 34篇 |
1986年 | 36篇 |
1985年 | 36篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Summary The synergistic effect of using mitomycin C-induced bacteriocin release protein (BRP) and glycine on cell growth, protein expression and release in a recombinant strain RR1 ofE. coli was investigated. An optimal combination of 50 ng/ml mitomycin C and 0.5% glycine concentration enhanced the release of periplasmic proteins from the cell into the fermentation broth without significantly affecting protein productivity. Under this optimal condition, the percentage of -amylase released into the broth increased from 7–13% to as much as 78%. The cell growth curve and low extracellular activity of the cytoplasmic protein -galactosidase show that there is no appreciable cell lysis. 相似文献
42.
Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines 总被引:11,自引:0,他引:11
Significant genetic variation in leaf photosynthetic rate has been reported in grain sorghum [Sorghum biocolor (L.) Moench]. The relationships between leaf photosynthetic rates and total biomass production and grain yield remain to be established and formed the purpose of this experiment. Twenty two grain sorghum parent lines were tested in the field during the 1988 growing season under well-watered and water-limited conditions. Net carbon assimilation rates were measured at mid-day during the 30 day period from panicle initiation to head exertion on upper-most fully expanded leaves using a portable photosynthesis system (LI-6200). Total biomass and grain production were determined at physiological maturity. The lines exhibited significant genetic variation in leaf photosynthetic rate, total biomass production and grain yield. Significant positive correlations existed between leaf photosynthesis and total biomass and grain production under both well-watered and water-limited conditions. The results suggest that leaf photosynthetic rate measured prior to flowering is a good indicator of productivity in grain sorghum. 相似文献
43.
44.
王国亮;南蓬;龚复俊;朱信强;袁晓;袁萍 《武汉植物学研究》1992,10(4):355-358
利用2DNMR结合其他波谱方法从苦皮藤种子油中鉴定了2个新倍半萜多元酯,它们分别是1α-苯甲酰氧-8β-烟酰氧-9α、11β-2乙酰氧-β-二氢沉香呋喃,1β-苯甲酰氧-2α、8β、9α、11β-4乙酰氧-β-二氢沉香呋喃,命名为苦皮藤酯2和3。 相似文献
45.
46.
The antifungal agent 15-azasterol A25822B was examined for effects on the growth and development of Ascosphaera apis. The minimum inhibition concentration (MIC) of azasterol against A. apis was 1 m. Growth and development of A. apis was completely controlled at this concentration. At a concentration of 0.01 m growth of A. apis was retarded and although sporocysts were formed developing spores were not be able to reach maturation. A major effect of azasterol at this low concentration was the accumulation of lipid in the hyphae, sporocysts and immature spores. In addition it caused a conformational change in mitochondria and damage to the spore membrane structure. On the basis of these results, further investigations of azasterol for the treatment of chalkbrood disease in the honey bee are warranted.Work was performed during sabbatical leave at the University of California, Davis. 相似文献
47.
48.
Alpha-ketoglutarate together with an amino group donor (alanine) was shown to be able to serve as a precursor for the glutamate pool which is released by potassium-induced depolarization (i.e., transmitter glutamate) in cerebellar granule cells. However, these compounds could not be utilized as precursors for intracellular glutamate or for release of transmitter aspartate. The formation of transmitter glutamate was inhibited by the transamination inhibitor aminooxyacetic acid but not by phenylsuccinate, an inhibitor of the dicarboxylate carrier in the mitochondrial membrane. Both of these inhibitors have previously been found to inhibit synthesis of transmitter glutamate from glutamine. The results support the hypothesis that alpha-ketoglutarate and alanine undergo transamination in the cytosol to form pyruvate and glutamate, and that this glutamate pool is available for transmitter release of glutamate but does not constitute the major intracellular pool of glutamate. 相似文献
49.
We have used hydroelastic waves to treat the closed trauma of the soft tissue. The Shu Huo Jiu (S. H. J.) which is the Chinese traditional medicine alcohol, was used as the fluid medium for generating the pressure waves. The biomechanical model was established and analysed. Both animal and human tests have been made. A practical system was designed, constructed and clinically tested to treat the closed trauma, such as the bruise, contusion, sprain etc.. This system was found to be effective. 相似文献
50.
Report of a family with dominant hereditary multicentric osteolysis. The review of the literature proves the clinical and genetic heterogeneity of the disease. 相似文献