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排序方式: 共有214条查询结果,搜索用时 484 毫秒
1.
J D Harper D W McCurdy M A Sanders J L Salisbury P C John 《Cell motility and the cytoskeleton》1992,22(2):117-126
We have used two monoclonal antibodies to demonstrate the presence and localization of actin in interphase and mitotic vegetative cells of the green alga Chlamydomonas reinhardtii. Commercially available monoclonal antibodies raised against smooth muscle actin (Lessard: Cell Motil. Cytoskeleton 10:349-362, 1988; Lin: Proc. Natl. Acad. Sci. USA 78:2335-2339, 1981) identify Chlamydomonas actin as a approximately 43,000-M(r) protein by Western immunoblot procedures. In an earlier study, Detmers and coworkers (Cell Motil. 5:415-430, 1985) first identified Chlamydomonas actin using NBD-phallacidin and an antibody raised against Dictyostelium actin; they demonstrated that F-actin is localized in the fertilization tubule of mating gametes. Here, we show by immunofluorescence that vegetative Chlamydomonas cells have an array of actin that surrounds the nucleus in interphase cells and undergoes dramatic reorganization during mitosis and cytokinesis. This includes the following: reorganization of actin to the anterior of the cell during preprophase; the formation of a cruciate actin band in prophase; reorganization to a single anterior actin band in metaphase; rearrangement forming a focus of actin anterior to the metaphase plate; reextension of the actin band in anaphase; presence of actin in the forming cleavage furrow during telophase and cytokinesis; and finally reestablishment of the interphase actin array. The studies presented here do not allow us to discriminate between G and F-actin. None the less, our observations, demonstrating dynamic reorganization of actin during the cell cycle, suggest a role for actin that may include the movement of basal bodies toward the spindle poles in mitosis and the formation of the cleavage furrow during cytokinesis. 相似文献
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Harriet M. McCurdy 《The Journal of cell biology》1969,43(2):220-228
The DOPA-reaction was used to identify tyrosinase in the nucleus and cytoplasm of the neural crest melanoblast of Taricha torosa, the California newt. In this urodele there is a nuclear DOPA-positive response during the normal embryonic development from the late blastula stage to the nucleus of the early melanocyte. During the gastrula stages, all nuclei of this newt are DOPA-positive. This positive nuclear response fades away after the formation of the neural crest, save in the melanoblasts. The only cells that give a positive DOPA marking in the cytoplasm are the melanoblasts. This cytoplasmic reaction appears while the melanoblast nucleus still gives a DOPA-positive reaction. Tyrosinase activity, as marked by unlabeled DOPA, has ceased in the fully mature melanocyte. The red nuclei, seen in some of the animals in the maturing melanocyte and adjacent tissues, may be in the hallachrome stage of melanin formation. There is a diffuse distribution of DOPA reactivity in the resting nucleus, and an adherence of the DOPA-marking in the region of the dividing chromosomes in the mitosis of DOPA-positive nuclei of the melanoblast. These observations suggest that tyrosinase may be among the chromosomally bound enzymes of the chromatin space. 相似文献
4.
S A McCurdy 《The Western journal of medicine》1994,160(4):338
I examined the pattern of mortality in the Donner Party, a group of emigrants who became trapped with inadequate food stores in the winter snows of the Sierra Nevada mountains in 1846-1847. The party consisted of 90 persons; the median age was 19.5 years (range, 1 to 70), 55 (61%) were male, and 72 (80%) were traveling with family members. Of the 90 persons, 42 (47%) died. Multivariate regression analysis indicated that age was the most important mortality risk factor. The lowest mortality (10%) was seen in the 6- to 14-year age group, and the highest was for persons younger than 6 years (relative risk = 6.6; 95% confidence interval [CI], 2.3 to 9.6) and persons 35 years or older (relative risk = 8.4; 95% CI, 3.4 to 10.2). Persons traveling without other family members had a relative risk of 2.0 (95% CI, 1.0 to 2.5). Men and boys were also at increased risk (relative risk = 2.0; 95% CI, 1.0 to 2.9). These factors can identify persons at increased risk for mortality in nutritionally stressed populations, and efforts to maintain intact family structures may improve survival. 相似文献
5.
Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex 总被引:14,自引:1,他引:13
Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1-
kbp portion of the yolk protein 2 locus, were sequenced in six individuals
from each of four species: Drosophila melanogaster, D. simulans, D.
mauritiana, and D. sechellia. The species and strains were the same as
those of a previous study of a 1.9-kbp region of the period locus. No
evidence was found for recent balancing or directional selection or for the
accumulation of selected differences between species. Yolk protein 2 has a
high level of amino acid replacement variation and a low level of
synonymous variation, while zeste has the opposite pattern. This contrast
is consistent with information on gene function and patterns of codon bias.
Polymorphism levels are consistent with a ranking of effective population
sizes, from low to high, in the following order: D. sechellia, D.
melanogaster, D.mauritiana, and D. simulans. The apparent species
relationships are very similar to those suggested by the period locus
study. In particular, D. simulans appears to be a large population that is
still segregating variation that arose before the separation of D.
mauritiana and D. sechellia. It is estimated that the separation of
ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The
separations of D. sechellia and D. mauritiana from ancestral D. simulans
appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged
from ancestral D. simulans 0.1 Myr more recently than D. sechellia.
相似文献
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A fibrous protein complex extracted fromEscherichia coli B/r by the method of Minkoff and Damadian [2] demonstrates arrowhead complexes when reacted with heavy meromyosin. 相似文献
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Leigh Perreault Carrie McCurdy Anna A. Kerege Julie Houck Kristine F?rch Bryan C. Bergman 《PloS one》2013,8(7)