全文获取类型
收费全文 | 19020篇 |
免费 | 1389篇 |
国内免费 | 1245篇 |
专业分类
21654篇 |
出版年
2024年 | 41篇 |
2023年 | 256篇 |
2022年 | 540篇 |
2021年 | 929篇 |
2020年 | 568篇 |
2019年 | 807篇 |
2018年 | 800篇 |
2017年 | 566篇 |
2016年 | 832篇 |
2015年 | 1106篇 |
2014年 | 1352篇 |
2013年 | 1448篇 |
2012年 | 1682篇 |
2011年 | 1526篇 |
2010年 | 972篇 |
2009年 | 937篇 |
2008年 | 1049篇 |
2007年 | 977篇 |
2006年 | 802篇 |
2005年 | 689篇 |
2004年 | 529篇 |
2003年 | 520篇 |
2002年 | 437篇 |
2001年 | 344篇 |
2000年 | 299篇 |
1999年 | 289篇 |
1998年 | 166篇 |
1997年 | 159篇 |
1996年 | 156篇 |
1995年 | 117篇 |
1994年 | 85篇 |
1993年 | 70篇 |
1992年 | 110篇 |
1991年 | 82篇 |
1990年 | 68篇 |
1989年 | 53篇 |
1988年 | 43篇 |
1987年 | 43篇 |
1986年 | 38篇 |
1985年 | 51篇 |
1984年 | 8篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1974年 | 5篇 |
1969年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Chiakang Ho Ya Gao Danning Zheng Yanjun Liu Shengzhou Shan Bin Fang Yixuan Zhao Dingzhong Song Yifan Zhang Qingfeng Li 《Journal of cellular and molecular medicine》2019,23(8):5108-5118
Obesity and its associated metabolic disorders such as diabetes, hepatic steatosis and chronic heart diseases are affecting billions of individuals. However there is no satisfactory drug to treat such diseases. In this study, we found that alisol A, a major active triterpene isolated from the Chinese traditional medicine Rhizoma Alismatis, could significantly attenuate high‐fat‐diet‐induced obesity. Our biochemical detection demonstrated that alisol A remarkably decreased lipid levels, alleviated glucose metabolism disorders and insulin resistance in high‐fat‐diet‐induced obese mice. We also found that alisol A reduced hepatic steatosis and improved liver function in the obese mice model.In addition, protein expression investigation revealed that alisol A had an active effect on AMPK/ACC/SREBP‐1c pathway. As suggested by the molecular docking study, such bioactivity of alisol A may result from its selective binding to the catalytic region of AMPK.Therefore, we believe that Alisol A could serve as a promising agent for treatment of obesity and its related metabolic diseases. 相似文献
102.
【目的】通过综合分析苏云金芽胞杆菌(Bacillus thuringiensis)HD73菌株Sigma54缺失突变体的转录组数据和蜡样芽胞杆菌(Bacillus cereus)ATCC 14579菌株CcpA缺失突变体的转录组数据,并进行启动子与CcpA蛋白的体外结合验证,明确Bt HD73菌株中Sigma54和CcpA共同调控的基因,丰富了对微生物的代谢调控网络的认识。【方法】以转录组测序结果为基础,通过基因同源性的比对在Bt HD73菌株中寻找受Sigma54和CcpA共同调控的基因,在这些基因中找到具有cre序列的启动子,通过凝胶阻滞验证这些启动子与CcpA蛋白的结合。【结果】Bt HD73菌株中有31个基因受Sigma54和CcpA共同调控,其中14个基因的启动子序列包含cre序列,这些启动子都可以与CcpA蛋白发生体外结合。【结论】Bt HD73菌株中有14个基因直接受CcpA的调控,同时其转录受Sigma54的控制。 相似文献
103.
Chen Z Zheng Z Huang H Song Y Zhang X Ma J Wang B Zhang C Ju J 《Bioorganic & medicinal chemistry letters》2012,22(9):3332-3335
Three new mycophenolic acid derivatives, penicacids A-C (1-3), together with two known analogues, mycophenolic acid (MPA, 4) and 4'-hydroxy-MPA (5), were isolated from a fungus Penicillium sp. SOF07 derived from a South China Sea marine sediment. The structures of compounds 1-3 were elucidated on the basis of MS and NMR ((1)H, (13)C, HSQC and HMBC) data analyses and comparisons with the known compounds. Structure-activity relationship studies of compounds 1-5 focused on inosine-monophosphate dehydrogenase inhibition revealed that hydroxylation at C-4', methylation at C-7-OH, dual hydroxylation at C-2'/C-3' double bond of MPA diminished bioactivity whereas glucosyl hydroxylation at C-4' correlated to bioactivity comparable to that observed for MPA. 相似文献
104.
105.
Bo Song Jürg Stcklin Deli Peng Yongqian Gao Hang Sun 《Botanical journal of the Linnean Society. Linnean Society of London》2015,179(2):349-359
Environmental conditions are known to affect the reproductive fitness of insects, as do host plants. Although the highly specialized bracts of Himalayan ‘glasshouse’ plants are thought to be an adaptive morphology that allows the plant to reproduce in harsh alpine environments, little information appears to exist concerning the benefit of these bracts for the pollinating insects. In this study, we examine whether the semi‐translucent bracts of Rheum alexandrae, a giant herb endemic to the alpine zone of the Hengduan Mountains in south‐western China, enhance the reproductive fitness of its pollinator. Rheum alexandrae depends mainly on mutualistic seed‐consuming Bradysia flies for pollination. Bracts increased interior temperature on sunny days, acted as a buffer against fluctuating air humidity, greatly decreased the intensities of ultraviolet B/C radiation and provided shelter from strong winds. Bract removal significantly decreased adult oviposition and offspring performance of pollinators during flowering and fruiting, respectively. Our results indicate that the bracts of R. alexandrae enhance the reproductive fitness of its pollinating seed‐consuming mutualist in alpine environments, which may be attributed to the positive effects of the bracts on the interior microenvironment. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 349–359. 相似文献
106.
Yuan Xu Chen Shao Xinpeng Fan Alan Warren Khaled A. S. Al-Rasheid Weibo Song Norbert Wilbert 《Polar Biology》2016,39(8):1439-1453
Antarctica is a remote and isolated biotope which makes it an ideal location for studying new and endemic species. Since there is little literature available on the diversity of ciliates in this area, a taxonomic survey of ciliates from melt-water of Collins glacier, King George Island, was carried out from January to March 2006. As a result, the morphology and infraciliature of five ciliates, including one new species, are described using live observations and silver staining: Gastronauta multistriata nov. spec., Neokeronopsis asiatica Foissner et al., 2010, Paraholosticha muscicola Kahl, 1932, Oxytricha sp., and Cyclidium glaucoma Müller, 1786. Gastronauta multistriata nov. spec. is distinguished from its congeners by the following combination of characters: cell size in vivo on average 80 × 40 μm; 5–9 kineties in left ciliary field; 18–23 kineties in right ciliary field, including 10–12 postoral kineties; 7–10 preoral kineties; dorsal brush along anterior dorsal margin, consisting of 5–8 groups of basal bodies. The only minor differences between the current population of N. asiatica and a previously described Antarctic population are the numbers of caudal cirri (6–10 vs. 8–15) and dorsal kineties (11–13 vs. 12–18). Paraholosticha sterkii is synonymised with P. muscicola. The Antarctic population of C. glaucoma corresponds well with a former population from China, the only difference being the number of kinetids in SK n (11–17 vs. 9–11). This work will contribute to the understanding of ciliate diversity in this little studied area. 相似文献
107.
Rui Cheng Xiaoman Zheng Yingmei Wang Xing Ma Xin Liu Wenjun Xu Mengyun Wang Yuanpeng Gao Xupeng Xing Chuan Zhou Hongzheng Sun Zekun Guo Fusheng Quan Jun Liu Song Hua Yongsheng Wang Yong Zhang Xu Liu 《中国科学:生命科学英文版》2022,65(11):2257-2268
Animal cloning can be achieved by somatic cell nuclear transfer(SCNT), but the resulting live birth rate is relatively low. We previously improved the efficiency of bovine SCNT by exogenous melatonin treatment or by overexpression of lysine-specific demethylase 4D(KDM4D) and 4E(KDM4E). In this study, we revealed abundant alternative splicing(AS) transitions during fertilization and embryonic genome activation, and demonstrated abnormal AS in bovine SCNT embryos compared with in vitro fertilized ... 相似文献
108.
Li YP Song W Shi SL Liu YQ Pan MH Dai FY Lu C Xiang ZH 《Genetics and molecular biology》2010,33(1):186-189
Bombyx mori and Bombyx mandarina are morphologically and physiologically similar. In this study, we compared the nucleotide variations in the complete mitochondrial (mt) genomes between the domesticated silkmoth, B. mori, and its wild ancestors, Chinese B. mandarina (ChBm) and Japanese B. mandarina (JaBm). The sequence divergence and transition mutation ratio between B. mori and ChBm are significantly smaller than those observed between B. mori and JaBm. The preference of transition by DNA strands between B. mori and ChBm is consistent with that between B. mori and JaBm, however, the regional variation in nucleotide substitution rate shows a different feature. These results suggest that the ChBm mt genome is not undergoing the same evolutionary process as JaBm, providing evidence for selection on mtDNA. Moreover, investigation of the nucleotide sequence divergence in the A+T-rich region of Bombyx mt genomes also provides evidence for the assumption that the A+T-rich region might not be the fastest evolving region of the mtDNA of insects. 相似文献
109.
110.
The objective of the experiment was to use starch processing waste as an alternative growth medium for cultivation of mycelia of the mushroom Phellinus linteus and to find an optimum condition under solid-state cultivation. Response surface analysis along with a central composite design was successfully applied to approximate the simultaneous effects of the substrate concentration (16-36 g l(-1)), pH (4.5-6.5), and temperature (25-35 degrees C) on the mycelial growth rate. In the model, pH and temperature significantly affected the mycelial growth but substrate concentration did not. The optimal substrate concentration, pH, and temperature for maximizing growth rate of P. linteus mycelia were found to be 16.5 g l(-1), pH 6.0, and 29.7 degrees C, respectively. Subsequent verification of these levels agreed with model predictions and the maximum mycelial growth rate at these conditions was 6.1 +/- 0.8 mm day(-1). Therefore, the results of the experiments suggest that starch processing waste could be utilized as a growth substrate for the cultivation of the mushroom mycelia of P. linteus, enhancing the usefulness of this byproduct of the starch manufacturing industry. This approach is likely to be useful for establishing similar parameters for the cultivation of other fungi. 相似文献