全文获取类型
收费全文 | 465篇 |
免费 | 39篇 |
国内免费 | 3篇 |
出版年
2021年 | 11篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 27篇 |
2012年 | 34篇 |
2011年 | 19篇 |
2010年 | 19篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1969年 | 5篇 |
1966年 | 3篇 |
1922年 | 2篇 |
1917年 | 2篇 |
排序方式: 共有507条查询结果,搜索用时 125 毫秒
1.
2.
Diamine oxide and serum amine oxidase, which catalyse the oxidation of diamines and polyamines, respectively, were trapped within reconstituted Sendai virus envelopes. These loaded envelopes were incubated with cultured normal chick fibroblasts or with fibroblasts transformed by Rous sarcoma viruses. The binding of the reconstituted envelopes to the cultured cells was confirmed by scanning electron microscopy. It has been shown that the reconstituted envelopes (1-3 microns diameter) were attached to the eukaryotic cells. No significant changes in the morphology of the normal chick embryo fibroblasts were noted upon treatment with enzyme-loaded envelopes. On the other hand, chick embryo fibroblasts transformed by Rous sarcoma virus were affected by the microinjected amine oxidases. Scanning electron microscopy demonstrated the formation of holes in the microinjected cells. Similar morphological changes were also observed when diamine oxidase was microinjected into cultured glioma cells. These holes may be the result of the ejection of the nucleus. These findings are in line with the observed effect of the injected amine oxidases on macromolecular synthesis in normal and transformed chick embryo fibroblasts. 相似文献
3.
4.
Amplification of sodium- and potassium-activated adenosinetriphosphatase in HeLa cells by ouabain step selection 总被引:8,自引:0,他引:8
A multistep selection for ouabain resistance was used to isolate a clone of HeLa S3 cells that overproduces the plasma membrane sodium, potassium activated adenosinetriphosphatase (Na+,K+-ATPase). Measurements of specific [3H]ouabain-binding to the resistant clone, C+, and parental HeLa cells indicated that C+ cells contain 8-10 X 10(6) ouabain binding sites per cell compared with 8 X 10(5) per HeLa cell. Plasma membranes isolated from C+ cells by a vesiculation procedure and analyzed for ouabain-dependent incorporation of [32P]phosphate into a 100,000-mol-wt peptide demonstrated a ten- to twelvefold increase in Na+,K+-ATPase catalytic subunit. The affinity of the enzyme for ouabain on the C+ cells was reduced and the time for half maximal ouabain binding was increased compared with the values for the parental cells. The population doubling time for cultures of C+ cells grown in dishes was increased and C+ cells were unable to grow in suspension. Growth of C+ cells in ouabain-free medium resulted in revertant cells, C-, with biochemical and growth properties identical with HeLa. Karyotype analysis revealed that the ouabain-resistant phenotype of the C+ cells was associated with the presence of minute chromosomes which are absent in HeLa and C- cells. This suggests that a gene amplification event is responsible for the Na+,K+-ATPase increase in C+ cells. 相似文献
5.
K O Ash J B Smith J W Kemp M B Lynch F G Moody J L Raymond M R McKnight R R Williams 《Clinical physiology and biochemistry》1983,1(6):293-299
Ouabain binding to erythrocyte membranes is increased in obese subjects. Three study groups are compared: 14 reference subjects, 102 +/- 16% of ideal weight; 9 obese on unrestricted diets, 207 +/- 16% of ideal weight; 11 obese on restricted diets, 202 +/- 35% of ideal weight. A reproducible (CV = 11.3%) ouabain-binding assay is used to measure Na+-K+ ATPase sites in erythrocyte membranes. The number of binding sites per red blood cell for obese subjects on unrestricted diets, 431 +/- 30, is greater than for the reference group, 346 +/- 66 (p less than 0.01), or for obese subjects on restricted diets, 371 +/- 68 (p less than 0.05). These data suggest that caloric intake influences the number of Na+-K+ ATPase sites. Scatchard plots indicate only one type of binding site for ouabain with an affinity constant of about 3 X 10(8) M-1. 相似文献
6.
Mutations in the uncE gene affecting assembly of the c-subunit of the adenosine triphosphatase of Escherichia coli. 总被引:11,自引:2,他引:9 下载免费PDF全文
D A Jans A L Fimmel L Langman L B James J A Downie A E Senior G R Ash F Gibson G B Cox 《The Biochemical journal》1983,211(3):717-726
The amino acid substitutions in the mutant c-subunits of Escherichia coli F1F0-ATPase coded for by the uncE429, uncE408 and uncE463 alleles affect the incorporation of these proteins into the cell membrane. The DNA sequence of the uncE429 allele differed from normal in that a G leads to A base change occurred at nucleotide 68 of the uncE gene, resulting in glycine being replaced by aspartic acid at position 23 in the c-subunit. The uncE408 and uncE463 mutant DNA sequences were identical and differed from normal in that a C leads to T base change occurred at nucleotide 91 of the uncE gene, resulting in leucine being replaced by phenylalanine at position 31 in the c-subunit. An increased gene dosage of the uncE408 or uncE463 alleles resulted in the incorporation into the membranes of the mutant c-subunits. The results are discussed in terms of the 'Helical Hairpin Hypothesis' of Engelman & Steitz [(1981) Cell 23,411-422]. 相似文献
7.
Six species of the genus Eumonhystera, one of which is new to science, are described from bottom samples of Lake Tana and two associated rivers, River Abbay and R. Gelda, Ethiopia. E. geraerti n.sp. can be identified by being the only species in the genus that combines very posteriorly positioned vulva [V% = 68.2 ± 0.7 (67.3–69.3)] with very anteriorly positioned amphids (Amph-ABE/LRW = 0.8). The other five species encountered, E. dispar (Bastian, 1865) Andrássy, 1981, E. filiformis (Bastian, 1865) Andrássy, 1981, E. pseudobulbosa (von Daday, 1896) Andrássy, 1981, E. mwerazii (Meyl, 1957) Andrássy, 1981, and E. vulgaris (de Man, 1880), Andrássy, 1981, are described in detail. The identities of some of the already described populations of E. dispar, E. filiformis and E. vulgaris are questioned and clearer and better ways of defining each of these three species are suggested. A peritrophic-like membrane on the outer side of the brush-border of the intestine of E. mwerazii, a species reported here for the first time out of its type locality, is reported. Also, scanning electronmicrographs of sectioned and entire specimens of E. mwerazii are presented. All species are reported from Ethiopia for the first time. 相似文献
8.
9.
10.
After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the
earth moderated. As a result, a considerable number and variety were present and widely distributed during the Jurassic and
Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became
reduced in variety and greatly restricted in distribution. Some of the Mesozoic ferns are rather primitive and obviously are
closely related descendants of Paleozoic taxa. Such ferns are assigned mostly to the Marattiaceae, Guaireaceae, Osmundaceae,
and Gleicheniaceae. The majority of the Mesozoic ferns, however, are distinctive and appear to have originated during that
era. These fossil ferns generally fit into modern orders and families such as the Matoniaceae or the Dipteridaceae. In some
cases, it is difficult to clearly distinguish some of the Mesozoic ferns from living genera.
A portion was presented as an invited paper to the symposium: Evolution of pteridophytes and gymnosperms at the XV International
Botanical Congress, Yokohama, Japan (1993). 相似文献