全文获取类型
收费全文 | 413篇 |
免费 | 34篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 25篇 |
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 35篇 |
2012年 | 28篇 |
2011年 | 21篇 |
2010年 | 21篇 |
2009年 | 17篇 |
2008年 | 16篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 14篇 |
2002年 | 7篇 |
2001年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1965年 | 2篇 |
1963年 | 4篇 |
排序方式: 共有447条查询结果,搜索用时 0 毫秒
1.
Detailed methods are presented for measurement and study of in vivo mutations and in vitro mutagenesis in human lymphocytes. The methods described include preparation of conditioned medium containing interleukin-2, enumeration of mutant clones, in vitro mutagenesis, and expansion of mutant clones for further study. 相似文献
2.
Receptors for estradiol, progesterone and dihydrotestosterone have been demonstrated in normal growing breasts of young females below 25 years. 相似文献
3.
B. Seshadri Sekhar C. K. Ramakrishna Kurup T. Ramasarma 《Molecular and cellular biochemistry》1990,95(1):61-70
A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN
Squamous Carcinoma of the Head and Neck
- MTX
Methotrexate
- CDDP
Cis-Platinum
- DHFR
Dihydrofolate Reductase 相似文献
4.
2',3'-cyclic nucleotides are intermediates and substrates of Ribonuclease (RNase)-catalysed reactions. The characterization of the equilibrium conformation as well as the flexibility inherent in these molecules helps in understanding the enzymatic action of RNases. The present study explores parameters like phase angle, glycosydic torsion angle and hydrogen bond to find possible interrelationship between them through Molecular Dynamics (MD) simulations on 3'-GMP,3'-UMP, A greater than p, G greater than p, U greater than p, C greater than p, GpA greater than p and UpA greater than p. Interesting results of the effect of cyclisation and other constraints such as hydrogen bond between certain groups on the equilibrium ribose conformation have emerged from this study. 相似文献
5.
6.
7.
Acridine orange and proflavine form complexes with the dinucleoside monophosphate, 5-iodocytidylyl(3′–5′)guanosine. The acridine orange-iodoCpG2 crystals are monoclinic, space group P21, with unit cell dimensions , β = 102.5 °. The proflavine-iodoCpG crystals are monoclinic, space group C2, with unit cell dimensions , β = 123.3 °. Both structures have been solved to atomic resolution by Patterson and Fourier methods, and refined by full matrix least-squares.Acridine orange forms an intercalative structure with iodoCpG in much the same manner as ethidium, ellipticine and 3,5,6,8-tetramethyl-N-methyl phenanthrolinium (Jain et al., 1977, Jain et al., 1979), except that the acridine nucleus lies asymmetrically in the intercalation site. This asymmetric intercalation is accompanied by a sliding of base-pairs upon the acridine nucleus and is similar to that observed with the 9-aminoacridine-iodoCpG asymmetric intercalative binding mode described in the previous papers (Sakore et al., 1977, Sakore et al., 1979). Basepairs above and below the drug are separated by about 6.8 Å and are twisted about 10 °; this reflects the mixed sugar puckering pattern observed in the sugar-phospate chains: C3′ endo (3′–5′) C2′ endo (i.e. each cytidine residue has a C3′ endo sugar comformation, while each guanosine residue has a C2′ endo sugar conformation), alterations in glycosidic torsional angles and other small but significant conformational changes in the sugar-phosphate backbone.Proflavine, on the other hand, demonstrates symmetric intercalation with iodoCpG. Hydrogen bonds connect amino groups on proflavine with phosphate oxygen atoms on the dinucleotide. In contrast to the acridine orange structure, base-pairs above and below the intercalative proflavine molecule are twisted about 36 °. The altered magnitude of this angular twist reflects the sugar puckering pattern that is observed: C3′ endo (3′–5′) C3′ endo. Since proflavine is known to unwind DNA in much the same manner as ethidium and acridine orange (Waring, 1970), one cannot use the information from this model system to understand how proflavine binds to DNA (it is possible, for example, that hydrogen bonding observed between proflavine and iodoCpG alters the intercalative geometry in this model system).Instead, we propose a model for proflavine-DNA binding in which proflavine lies asymmetrically in the intercalation site (characterized by the C3′ endo (3′–5′) C2′ endo mixed sugar puckering pattern) and forms only one hydrogen bond to a neighboring phosphate oxygen atom. Our model for proflavine-DNA binding, therefore, is very similar to our acridine orange-DNA binding model. We will describe these models in detail in this paper. 相似文献
8.
9.
Ramya Krishnan Rahul Ravikumar Menon Naoto Tanaka Hans-Jürgen Busse Srinivasan Krishnamurthi Natarajan Rameshkumar 《PloS one》2016,11(3)
A novel yellow colony-forming bacterium, strain P3B162T was isolated from the pokkali rice rhizosphere from Kerala, India, as part of a project study aimed at isolating plant growth beneficial rhizobacteria from saline tolerant pokkali rice and functionally evaluate their abilities to promote plant growth under saline conditions. The novel strain P3B162T possesses plant growth beneficial traits such as positive growth on 1-aminocyclopropane-1-carboxylic acid (ACC), production of indole acetic acid (IAA) and siderophore. In addition, it also showed important phenotypic characters such as ability to form biofilm and utilization of various components of plant root exudates (sugars, amino acids and organic acids), clearly indicating its lifestyle as a plant rhizosphere associated bacterium. Taxonomically, the novel strain P3B162T was affiliated to the genus Arthrobacter based on the collective results of phenotypic, genotypic and chemotaxonomic analyses. Moreover, molecular analysis using 16S rRNA gene showed Arthrobacter globiformis NBRC 12137T, Arthrobacter pascens DSM 20545T and Arthrobacter liuii DSXY973T as the closely related phylogenetic neighbours, showing more than 98% 16S rRNA similarity values, whereas the recA gene analysis displayed Arthrobacter liuii JCM 19864T as the nearest neighbour with 94.7% sequence similarity and only 91.7% to Arthrobacter globiformis LMG 3813T and 88.7% to Arthrobacter pascens LMG 16255T. However, the DNA-DNA hybridization values between strain P3B162T, Arthrobacter globiformis LMG 3813T, Arthrobacter pascens LMG 16255T and Arthrobacter liuii JCM 19864T was below 50%. In addition, the novel strain P3B162T can be distinguished from its closely related type strains by several phenotypic characters such as colony pigment, tolerance to NaCl, motility, reduction of nitrate, hydrolysis of DNA, acid from sucrose, cell wall sugars and cell wall peptidoglycan structure. In conclusion, the combined results of this study support the classification of strain P3B162T as a novel Arthrobacter species and we propose Arthrobacter pokkalii sp.nov.as its name. The type strain is P3B162T (= KCTC 29498T = MTCC 12358T). 相似文献