全文获取类型
收费全文 | 8623篇 |
免费 | 595篇 |
国内免费 | 3篇 |
出版年
2024年 | 4篇 |
2023年 | 34篇 |
2022年 | 96篇 |
2021年 | 181篇 |
2020年 | 152篇 |
2019年 | 172篇 |
2018年 | 260篇 |
2017年 | 222篇 |
2016年 | 368篇 |
2015年 | 556篇 |
2014年 | 577篇 |
2013年 | 678篇 |
2012年 | 802篇 |
2011年 | 781篇 |
2010年 | 533篇 |
2009年 | 435篇 |
2008年 | 586篇 |
2007年 | 507篇 |
2006年 | 470篇 |
2005年 | 400篇 |
2004年 | 395篇 |
2003年 | 299篇 |
2002年 | 267篇 |
2001年 | 82篇 |
2000年 | 59篇 |
1999年 | 47篇 |
1998年 | 60篇 |
1997年 | 35篇 |
1996年 | 35篇 |
1995年 | 21篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1966年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有9221条查询结果,搜索用时 15 毫秒
11.
Anna L. Trifillis Myong Won Kahng 《In vitro cellular & developmental biology. Plant》1990,26(5):441-446
Summary We have developed an in vitro model of human papillary collecting duct cells isolated from cadaver kidneys using methods similar
to those we previously reported for the isolation of human proximal tubule cells. To date we have isolated papillary collecting
duct cells from 100 normal human kidneys. Papillae were dissected and digested in Cellgro containing 400 U/ml collagenase.
Cells were plated on fibronectin-coated culture flasks at a density of 104 live cells/ml in Cellgro supplemented with insulin and 10% fetal bovine serum. Confluent monolayers, which were able to withstand
600 mOsm for 8 h, were obtained within 10 to 15 d. Cells of primary isolates and first passages exhibited epithelial cell ultrastructure
including cell junctions, microvilli, and cilia. A dark-brown reaction product was observed in these cells when stained by
the immunoperoxidase method with peroxidase-labeled peanut lectin (Arachis hypogaea), which binds specifically to human distal tubule and collecting duct cells. These cells were negative for Factor-VIII (a
marker for endothelial cells) and γ-glutamyltransferase (a marker for proximal tubule cells). High activities of the glycolytic
enzyme pyruvate kinase and arginine vasopressin-stimulated cAMP production in these cells are consistent with a distal nephron
origin. The results indicate that human collecting duct cells can be isolated and cultured to provide an in vitro system to
probe pathogenetic mechanisms of potential nephrotoxins.
Part of this work was presented at a Symposium of the Center for Alternatives to Animal Testing, April 4–5, 1989, Johns Hopkins
Medical Institutions, Baltimore, MD 21205.
This work was supported in part by grants R01-AI24179, PO1-A804393 for the Public Health Service, U.S. Department of Health
and Human Services, and by a grant from the National Kidney Foundation, Baltimore, MD affiliate. 相似文献
12.
The frequencies of chromosome aberrations in 135 workers from nuclear-power plants were compared with those in 135 age-matched controls. A total of 135,000 cells was scored. The frequencies of dicentric chromosome were 1.67 × 10−3 in the exposed group and 0.49 × 10−3 in the control group and those of chromosome-type deletion were 3.33 × 10−3 and 1.10 × 10−3, respectively. The frequencies of all types of chromosome aberrations in the exposed subjects were higher than those in the control group, but no significant trend of dose-dependent increase was observed when only the exposed group were considered. Poisson regression analysis, with both exposed and control included, showed that there was a significant association of chromosome aberration with radiation dose and the duration of work, but not with age, smoking habit and alcohol intake. It was also found that recent exposure to radiation, within the last 5 years, had contributed more to the observed chromosome aberration than earlier exposure. 相似文献
13.
Dong-Woog Choi Jai Young Song Man-Ho Oh Jong Seob Lee Jinho Moon Se Won Suh Sang-Gu Kim 《Plant molecular biology》1996,30(5):1059-1066
A root-specific cDNA clone, PVR3, was isolated from a bean (Phaseolus vulgaris L.) root cDNA library by a differential screening procedure. The nucleotide sequence of PVR3 contains an open reading frame coding for an 11.14 kDa polypeptide of 102 amino acid residues; the first 25 amino acids correspond to the sequence characteristic of a signal peptide. Comparison of the deduced PVR3 polypeptide sequence with the polypeptide sequences of previously cloned genes indicates that PVR3 may encode a ns-LTP-like protein. Molecular modelling of the PVR3 protein predicts that it has a three-dimensional structure that is similar to the three-dimensional model determined from the maize ns-LTP. The PVR3 mRNA accumulated mainly in the roots of young seedlings. It can be detected at low levels in flowers, but it is not detected in other organs. Genomic Southern blot analysis indicates that the genomic DNA corresponding to PVR3 cDNA is encoded by a single gene or small gene family in the bean genome. 相似文献
14.
15.
A 4-chlorophenol (4-CP)-degrading bacterium, strain CPW301, was isolated from soil and identified as Comamonas testosteroni. This strain dechlorinated and degraded 4-CP via a meta-cleavage pathway. CPW301 could also utilize phenol as a carbon and energy source without the accumulation of any metabolites via the same meta-cleavage pathway. When phenol was added as a additional substrate, CPW301 could degrade 4-CP and phenol simultaneously. The addition of phenol greatly accelerated the degradation of 4-CP due to the increased cell mass. The simultaneous degradation of the 4-CP and phenol is useful not only for enhanced cell growth but also for the bioremediation of both compounds, which are normally present in hazardous waste sites as a mixture. 相似文献
16.
Panose, a major component of isomalto-oligosaccharides, was selectively produced from maltose using transglucosylation reaction catalyzed by intact cells of Aureobasidium pullulans. When 50 %(w/v) maltose was used as a substrate, the maximum concentration of panose accumulated in the final reaction mixture was about 50 %(w/w) after 120 hr reaction at 55 °C. 相似文献
17.
Journal of Physiology and Biochemistry - The browning of white adipose tissue (WAT) has attracted considerable attention in the scientific community as a popular strategy for enhancing energy... 相似文献
18.
Jong An Lee Jung Ho Ahn Gi Bae Kim Sol Choi Ji Yeon Kim Sang Yup Lee 《Biotechnology and bioengineering》2023,120(1):203-215
Microbial production of various TCA intermediates and related chemicals through the reductive TCA cycle has been of great interest. However, rumen bacteria that naturally possess strong reductive TCA cycle have been rarely studied to produce these chemicals, except for succinic acid, due to their dependence on fumarate reduction to transport electrons for ATP synthesis. In this study, malic acid (MA), a dicarboxylic acid of industrial importance, was selected as a target chemical for mass production using Mannheimia succiniciproducens, a rumen bacterium possessing a strong reductive branch of the TCA cycle. The metabolic pathway was reconstructed by eliminating fumarase to prevent MA conversion to fumarate. The respiration system of M. succiniciproducens was reconstructed by introducing the Actinobacillus succinogenes dimethylsulfoxide (DMSO) reductase to improve cell growth using DMSO as an electron acceptor. Also, the cell membrane was engineered by employing Pseudomonas aeruginosa cis-trans isomerase to enhance MA tolerance. High inoculum fed-batch fermentation of the final engineered strain produced 61 g/L of MA with an overall productivity of 2.27 g/L/h, which is the highest MA productivity reported to date. The systems metabolic engineering strategies reported in this study will be useful for developing anaerobic bioprocesses for the production of various industrially important chemicals. 相似文献
19.
Doan Minh Sang Ik Ho Na Dr. Duong Tien Anh Do Thi Mai Dung Nguyen Thi Thu Hang Nguyen T. Phuong-Anh Assoc. Prof. Dr. Pham-The Hai Assoc. Prof. Dr. Dao Thi Kim Oanh Dr. Truong Thanh Tung Soo Jung Lee Joo Hee Kwon Prof. Dr. Jong Soon Kang Prof. Dr. Sang-Bae Han Assoc. Prof. Dr. Dinh Thi Thanh Hai Prof. Dr. Nguyen-Hai Nam 《化学与生物多样性》2023,20(5):e202201030
Herein, we report the design, synthesis and evaluation of novel (E)-3-(3-oxo-4-substituted-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)-N-hydroxypropenamides ( 4 a – i , 7 a – g ) targeting histone deacetylases. Three human cancer cell lines were used to test the cytotoxicity of the synthesized compounds (SW620, colon; PC-3, prostate; NCI−H23, lung cancer); inhibitory activity towards HDAC; anticancer activity; as well as their impact on the cell cycle and apoptosis. As a result, compounds 4 a – i bearing the alkyl substituents seemed to be less potent than the benzyl-containing compounds 7 a – g in all biological assays. Compounds 7 e – f were found to be the most active HDAC inhibitors with IC50 of 1.498±0.020 μM and 1.794±0.159 μM, respectively. In terms of cytotoxicity and anticancer assay, 7 e and 7 f also showed good activity with IC50 values in the micromolar range. In addition, the cell cycle and apoptosis of SW620 were affected by compound 7 f in almost a similar manner to that of reference compound SAHA. Docking assays were carried out for analysis the binding mode and selectivity of this compound toward 8 HDAC isoforms. Overall, our data confirmed that the inhibition of HDAC plays a pivotal role in their anticancer activity. 相似文献