全文获取类型
收费全文 | 2316篇 |
免费 | 124篇 |
国内免费 | 2篇 |
出版年
2022年 | 6篇 |
2021年 | 20篇 |
2020年 | 15篇 |
2019年 | 18篇 |
2018年 | 32篇 |
2017年 | 19篇 |
2016年 | 41篇 |
2015年 | 86篇 |
2014年 | 76篇 |
2013年 | 186篇 |
2012年 | 152篇 |
2011年 | 133篇 |
2010年 | 82篇 |
2009年 | 105篇 |
2008年 | 137篇 |
2007年 | 151篇 |
2006年 | 140篇 |
2005年 | 147篇 |
2004年 | 141篇 |
2003年 | 143篇 |
2002年 | 139篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 32篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 13篇 |
1993年 | 27篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 10篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有2442条查询结果,搜索用时 31 毫秒
1.
Tomohiro Hamasaki Takahiro Matsumoto Naoya Sakamoto Akiko Shimahara Shiori Kato Ayumi Yoshitake Ayumi Utsunomiya Hisayoshi Yurimoto Esteban C. Gabazza Tadaaki Ohgi 《Nucleic acids research》2013,41(12):e126
Radioisotopes and fluorescent compounds are frequently used for RNA labeling but are unsuitable for clinical studies of RNA drugs because of the risk from radiation exposure or the nonequivalence arising from covalently attached fluorophores. Here, we report a practical phosphoramidite solid-phase synthesis of 18O-labeled RNA that avoids these disadvantages, and we demonstrate its application to quantification and imaging. The synthesis involves the introduction of a nonbridging 18O atom into the phosphate group during the oxidation step of the synthetic cycle by using 18O water as the oxygen donor. The 18O label in the RNA was stable at pH 3–8.5, while the physicochemical and biological properties of labeled and unlabeled short interfering RNA were indistinguishable by circular dichroism, melting temperature and RNA-interference activity. The 18O/16O ratio as measured by isotope ratio mass spectrometry increased linearly with the concentration of 18O-labeled RNA, and this technique was used to determine the blood concentration of 18O-labeled RNA after administration to mice. 18O-labeled RNA transfected into human A549 cells was visualized by isotope microscopy. The RNA was observed in foci in the cytoplasm around the nucleus, presumably corresponding to endosomes. These methodologies may be useful for kinetic and cellular-localization studies of RNA in basic and pharmaceutical studies. 相似文献
2.
3.
Circulating tumor cells (CTCs), shed from primary tumors and disseminated into peripheral blood, are playing a major role in metastasis. Even after isolation of CTCs from blood, the target cells are mixed with a population of other cell types. Here, we propose a new method for analyses of cell mixture at the single-cell level using a microfluidic device that contains arrayed electroactive microwells. Dielectrophoretic (DEP) force, induced by the electrodes patterned on the bottom surface of the microwells, allows efficient trapping and stable positioning of single cells for high-throughput biochemical analyses. We demonstrated that various on-chip analyses including immunostaining, viability/apoptosis assay and fluorescent in situ hybridization (FISH) at the single-cell level could be conducted just by applying specific reagents for each assay. Our simple method should greatly help discrimination and analysis of rare cancer cells among a population of blood cells. 相似文献
4.
The concentration of 3-phosphoglyceroyl phosphate in erythrocytes was increased by more than 100-fold when red cells were incubated with extracellular phosphoenolpyruvate at 37 degrees C. Since these elevated levels were maintained for 60 min, the metabolism of 3-phosphoglyceroyl phosphate and related compounds could be investigated in phosphoenolpyruvate-treated erythrocytes. 2,3-Bisphosphoglycerate synthesis was not affected by intracellular pH when the 3-phosphoglyceroyl phosphate level was constant but did vary with 3-phosphoglyceroyl phosphate concentration. On the other hand, the relationship between the rate of 2,3-bisphosphoglycerate synthesis and 3-phosphoglyceroyl phosphate concentration was not straightforward. At relatively low concentrations of 3-phosphoglyceroyl phosphate, the observed rate of 2,3-bisphosphoglycerate synthesis agreed with a rate calculated from a formula incorporating kinetic parameters of purified 2,3-bisphosphoglycerate synthase (Rose, Z.B. (1973) Arch. Biochem. Biophys. 158, 903-910). However, at high concentrations of 3-phosphoglyceroyl phosphate, the observed rate of 2,3-bisphosphoglycerate synthesis was lower than the calculated value. The concentration of glucose 1,6-bisphosphate did not increase even when 3-phosphoglyceroyl phosphate was elevated to 200 microM. Elevated levels of intracellular 2,3-bisphosphoglycerate did not inhibit glycolytic activity in these erythrocytes. These results suggest that incubation of erythrocytes with phosphoenolpyruvate is a useful technique to investigate the effect of metabolic perturbations at the intermediate stages of glycolysis. 相似文献
5.
6.
Summary An activated carbon column was utilized for the synthesis of disaccharides by use of a reversed hydrolysis activity of an immobilized -galactosidase column in order to shift the equilibrium to the direction of condensation. The yields of lactulose and allo-lactulose from galactose and fructose, and N-acetyl lactosamine and N-acetyl allolactosamine from galactose and N-acetyl glucosamine, were 11.3% and 10.0%, respectively. 相似文献
7.
Abstract Biovar A strains of Fusobacterium necrophorum exhibited high hydrophobicity when examined by the method of Rosenberg et al. Biovar B strains showed a lower cell surface hydrophobicity than biovar A strains. Biovar B strains were divided into 2 groups according to their hydrophobic activity. The strains of biovar A and the first group of biovar B were increasingly removed from aqueous phase to octane phase by increasing the volume of octane, but the turbidity of the second group of biovar B was not significantly affected. The hydrophobicity of biovar A strains decreased on heating at 60 and 100°C for 30 min. 相似文献
8.
S Hamasaki H Hayashidani K Kaneko M Ogawa Y Shigeta 《Journal of wildlife diseases》1989,25(3):401-403
Yersinia pseudotuberculosis was isolated from three specimens of two species of birds, the black-faced bunting (Emberiza spodocephala) and pied wagtail (Motacilla alba), of 528 specimens of birds examined from coastal regions in Japan. The two isolated strains of Y. pseudotuberculosis were identified as serovar 4b and serovar 3. This is the first isolation of Y. pseudotuberculosis from birds in Japan. Yersinia enterocolitica was isolated from three specimens of the pied wagtail, one specimen of the reed bunting (Emberiza schoeniclus) and one specimen of the rustic bunting (Emberiza rustica). Yersinia frederiksenii was isolated from two specimens of the gray-rumped sandpiper (Heteroscelus brevipes). Yersinia intermedia was isolated from one specimen of the pied wagtail. 相似文献
9.
Two distinct O-methyltransferases in aflatoxin biosynthesis 总被引:3,自引:0,他引:3
The substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. When demethylsterigmatocystin (DMST) was fed to Aspergillus parasiticus NIAH-26, which endogenously produces neither aflatoxins nor precursors in YES medium, aflatoxins B1 and G1 were produced. When dihydrodemethylsterigmatocystin (DHDMST) was fed to this mutant, aflatoxins B2 and G2 were produced. Results of the cell-free experiment with S-adenosyl-[methyl-3H]methionine showed that first the C-6-OH groups of DMST and DHDMST are methylated to produce sterigmatocystin and dihydrosterigmatocystin (O-methyltransferase I) and then the C-7-OH groups are methylated to produce O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin (DHOMST) (O-methyltransferase II). However, no methyltransferase activity was observed when either OMST, DHOMST, 5,6-dimethoxysterigmatocystin, 5-methoxysterigmatocystin, or sterigmatin was incubated with the cell extract. Treatment of the cell extract with N-ethylmaleimide inhibited O-methyltransferase I activity but not that of O-methyltransferase II. Furthermore, these O-methyltransferases were different in their protein molecules and were involved in both the reactions from DMST to OMST and DHDMST to DHOMST. The reactions described in this paper were not observed when the same mold had been cultured in YEP medium. 相似文献
10.
The substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. When demethylsterigmatocystin (DMST) was fed to Aspergillus parasiticus NIAH-26, which endogenously produces neither aflatoxins nor precursors in YES medium, aflatoxins B1 and G1 were produced. When dihydrodemethylsterigmatocystin (DHDMST) was fed to this mutant, aflatoxins B2 and G2 were produced. Results of the cell-free experiment with S-adenosyl-[methyl-3H]methionine showed that first the C-6-OH groups of DMST and DHDMST are methylated to produce sterigmatocystin and dihydrosterigmatocystin (O-methyltransferase I) and then the C-7-OH groups are methylated to produce O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin (DHOMST) (O-methyltransferase II). However, no methyltransferase activity was observed when either OMST, DHOMST, 5,6-dimethoxysterigmatocystin, 5-methoxysterigmatocystin, or sterigmatin was incubated with the cell extract. Treatment of the cell extract with N-ethylmaleimide inhibited O-methyltransferase I activity but not that of O-methyltransferase II. Furthermore, these O-methyltransferases were different in their protein molecules and were involved in both the reactions from DMST to OMST and DHDMST to DHOMST. The reactions described in this paper were not observed when the same mold had been cultured in YEP medium. 相似文献