全文获取类型
收费全文 | 2003篇 |
免费 | 153篇 |
国内免费 | 3篇 |
专业分类
2159篇 |
出版年
2024年 | 2篇 |
2023年 | 26篇 |
2022年 | 28篇 |
2021年 | 61篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 66篇 |
2017年 | 51篇 |
2016年 | 81篇 |
2015年 | 87篇 |
2014年 | 113篇 |
2013年 | 163篇 |
2012年 | 175篇 |
2011年 | 155篇 |
2010年 | 102篇 |
2009年 | 91篇 |
2008年 | 125篇 |
2007年 | 122篇 |
2006年 | 105篇 |
2005年 | 72篇 |
2004年 | 69篇 |
2003年 | 70篇 |
2002年 | 64篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1965年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有2159条查询结果,搜索用时 15 毫秒
921.
922.
Rhee YJ Han CR Kim WC Jun DY Rhee IK Kim YH 《Journal of microbiology and biotechnology》2010,20(10):1378-1385
A novel agarolytic bacterium KY-YJ-3, producing extracellular agarase, was isolated from the freshwater sediment of the Sincheon River in Daegu, Korea. On the basis of gram-staining data, morphology, and phylogenetic analysis of the 16S rDNA sequence, the isolate was identified as Cellvibrio sp. By ammonium sulfate precipitation followed by Toyopearl QAE-550C, Toyopearl HW-55F, and Mono-Q column chromatography, the extracellular agarase in the culture fluid could be purified 120.2-fold with yield of 8.1%. The specific activity of the purified agarase was 84.2 U/mg. The molecular mass of the purified agarase was 70 kDa as determined by dodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimal temperature and pH of the purified agarase were 35 degrees C and pH 7.0, respectively. The purified agarase failed to hydrolyze the other polysaccharide substrates, including carboxymethyl (CM)-cellulose, dextran, soluble starch, pectin, and polygalacturonic acid. Kinetic analysis of the agarose-hydrolysis catalyzed by the purified agarase using thin layer chromatography (TLC) exhibited that the main products were neoagarobiose, neoagarotetraose, and neoagarohexaose. These results demonstrated that the newly isolated freshwater agarolytic bacterium KY-YJ-3 was a Cellvibrio sp., and could produce an extracellular beta-agarase, which hydrolyzed agarose to yield neoagarobiose, neoagarotetraose, and neoagarohexaose as the main products. 相似文献
923.
Richland Tester Xuefei Tan Gregory R. Luedtke Imad Nashashibi Kurt Schinzel Weiling Liang Joon Jung Sundeep Dugar Albert Liclican Jocelyn Tabora Daniel E. Levy Steven Do 《Bioorganic & medicinal chemistry letters》2010,20(8):2560-2563
Optimization of a tri-substituted N-pyridyl amide led to the discovery of a new class of potent N-pyrimidyl amide based p38α MAP kinase inhibitors. Initial SAR studies led to the identification of 5-dihydrofuran as an optimal hydrophobic group. Additional side chain modifications resulted in the introduction of hydrogen bond interactions. Through extensive SAR studies, analogs bearing free amino groups and alternatives to the parent (S)-α-methyl benzyl moiety were identified. These compounds exhibited improved cellular activities and maintained balance between p38α and CYP3A4 inhibition. 相似文献
924.
925.
NamHui Yim Do Thi Ha Trinh Nam Trung Jin Pyo Kim SangMyung Lee MinKyeun Na HyunJu Jung Hyun Su Kim Young Ho Kim KiHwan Bae 《Bioorganic & medicinal chemistry letters》2010,20(3):1165-1168
Nine compounds isolated from the leaf and stem of Vitis amurensis Rupr. (Vitaceae) were evaluated for their antimicrobial activity against two oral pathogens, Streptococcus mutans and Streptococcus sanguis, which are associated with caries and periodontal disease, respectively. The results of several antimicrobial tests, including MIC, MBC, and TBAI, showed that three compounds inhibited the growth of the test bacteria at concentrations ranging from 12.5 to 50 μg/mL. Among these compounds, compound 5, trans-ε-viniferin, displayed the strongest activity against S. mutans and S. sanguis with MIC values of 25 and 12.5 μg/mL, respectively. This is the first report on the antimicrobial activity of stilbenes and oligostilbenes isolated from the leaf and stem of V. amurensis. Thus, this result suggests that natural antimicrobial compounds derived from V. amurensis may benefit oral health as plaque-control agents for the prevention of dental caries and periodontal disease. 相似文献
926.
927.
Chau VM Phan VK Nguyen X Nguyen XC Nguyen PT Nguyen HN Hoang le TA Do CT Thuy DT Kang HK Jang HD Kim YH 《Bioorganic & medicinal chemistry letters》2011,21(7):2155-2159
Two new diterpenes, lobocompactols A (1) and B (2), and five known compounds (3-7) were isolated from the methanol extract of the soft coral Lobophytum compactum using combined chromatographic methods and identified based on NMR and MS data. Each compound was evaluated for cytotoxic activity against A549 (lung) and HL-60 (acute promyelocytic leukemia) human cancer cell lines. Among them, compound 5 exhibited strong cytotoxic activity against the A549 cell line with an IC50 of 4.97 ± 0.06 μM. Compounds 3, 4, and 7 showed moderate activity with IC50 values of 23.03 ± 0.76, 31.13 ± 0.08, and 36.45 ± 0.01 μM, respectively. The cytotoxicity of 5 on the A549 cells was comparable to that of the positive control, mitoxantrone (MX). All compounds exhibited moderate cytotoxicity against the HL-60 cell line, with IC50 values ranging from 17.80 ± 1.43 to 59.06 ± 2.31 μM. Their antioxidant activity was also measured using oxygen radical absorbance capacity method, compounds 1 and 2 exhibiting moderate peroxyl radical scavenging activity of 1.4 and 1.3 μM Trolox equivalents, respectively, at a concentration of 5 μM. 相似文献
928.
Hee Jeong Kong Gyeong-Eun Hong Bo-Hye Nam Young-Ok Kim Woo-Jin Kim Sang-Jun Lee Nam-Sil Lee Jeong Wan Do Hyun Kook Cho JaeHun Cheong Chang Hoon Lee Kyung-Kil Kim 《Fish & shellfish immunology》2009,27(3):486-492
The cDNA encoding of a complement factor D/adipsin and kallikrein-like serine protease, designated PoDAK, was isolated from the olive flounder Paralichthys olivaceus. PoDAK cDNA encodes a polypeptide with 277 amino acids containing conserved catalytic triad residues of serine proteases. The amino acid sequence of PoDAK showed high similarity to the kallikrein-like protein of medaka, mammalian adipsin/complement factor D and tissue kallikrein homolog, KT-14 of trout, complement factor D of zebrafish, and shared 31.6–36.8% homology with complement factor D/adipsin known from other species, including mammals. Phylogenetic analysis revealed that PoDAK clustered with the kallikrein-like protein of medaka and mammalian adipsin/complement factor D and tissue kallikrein homolog KT-14 of trout. The expression of PoDAK mRNA was high in the gills and heart, moderate in muscle, liver, intestine, stomach, kidney, and spleen of healthy flounder, and increased in the kidney, liver, and spleen of flounder challenged by the viral hemorrhagic septicemia virus (VHSV) or Streptococcus iniae. In situ hybridization confirmed that PoDAK mRNA is localized in the kidney and heart of individuals infected with VHSV. Further investigations are needed to clarify the function of PoDAK in vivo and in vitro. 相似文献
929.
Zhang J Khvorostov I Hong JS Oktay Y Vergnes L Nuebel E Wahjudi PN Setoguchi K Wang G Do A Jung HJ McCaffery JM Kurland IJ Reue K Lee WN Koehler CM Teitell MA 《The EMBO journal》2011,30(24):4860-4873
It has been assumed, based largely on morphologic evidence, that human pluripotent stem cells (hPSCs) contain underdeveloped, bioenergetically inactive mitochondria. In contrast, differentiated cells harbour a branched mitochondrial network with oxidative phosphorylation as the main energy source. A role for mitochondria in hPSC bioenergetics and in cell differentiation therefore remains uncertain. Here, we show that hPSCs have functional respiratory complexes that are able to consume O(2) at maximal capacity. Despite this, ATP generation in hPSCs is mainly by glycolysis and ATP is consumed by the F(1)F(0) ATP synthase to partially maintain hPSC mitochondrial membrane potential and cell viability. Uncoupling protein 2 (UCP2) plays a regulating role in hPSC energy metabolism by preventing mitochondrial glucose oxidation and facilitating glycolysis via a substrate shunting mechanism. With early differentiation, hPSC proliferation slows, energy metabolism decreases, and UCP2 is repressed, resulting in decreased glycolysis and maintained or increased mitochondrial glucose oxidation. Ectopic UCP2 expression perturbs this metabolic transition and impairs hPSC differentiation. Overall, hPSCs contain active mitochondria and require UCP2 repression for full differentiation potential. 相似文献
930.
Hayoung Song Hankuil Yi Changhee Do Ching-Tack Han Ill-Sup Nou Yoonkang Hur 《Genes & genomics.》2017,39(2):207-223
Photoperiod is the most important environmental cue for the regulation of flowering time, a highly important agronomic trait for crop productivity. To help elucidate the photoperiodic control of flowering in Brassicaceae, we performed microarray experiments using species-specific oligo-arrays with the long day (LD) plant Arabidopsis thaliana and the photoperiod-independent plant rapid cycling Brassica rapa (RCBr). Enrichment analysis of the gene ontologies of differentially expressed genes (DEGs) did not uncover clear differences in gene expression between photoperiod-dependent and -independent plants. Most genes that were up-regulated under LD conditions in Arabidopsis were also up-regulated in RCBr. In addition, most genes associated with light signaling and the circadian clock showed similar expression patterns between Arabidopsis and RCBr, implying that most components known to be key regulators in the photoperiodic flowering pathway are not responsible for the photoperiod independence of RCBr. Nonetheless, we identified one clock-associated gene, PSEUDO-RESPONSE REGULATOR9 (PRR9), as a candidate gene explaining the photoperiod independence of RCBr. The mechanism underlying the role of PRR9 in photoperiodic control and genomic polymorphisms should be further explored using different B. rapa species. 相似文献