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61.
62.
1,3-Butadiene (BD) is an indirect alkylating agent that has greater cancer
potency in the mouse than in the rat. The purpose of the present study was
to compare the mutagenic potency of BD at the hprt locus of T- lymphocytes
of exposed mice and rats and to determine whether mutations induced in this
marker gene can be used as a quantitative indicator for species differences
in susceptibility to cancer. To this end, experiments were conducted to
define the effects of exposure duration and the time elapsed after
exposures on the frequency of hprt mutations (Mf) in T-cells from female
B6C3F1 mice and F344 rats of similar age (4- 5 weeks) when exposed to BD by
inhalation. The accumulation of hprt mutations in T-cells from thymus was
assessed in animals necropsied 2 weeks after exposure to 0 or 1250 ppm BD
for 1 or 2 weeks, while the time course for the appearance of hprt mutant
T-cells (i.e., the phenotypic expression and cell migration) in thymus and
spleen was evaluated in animals necropsied at weekly/biweekly intervals up
to 10 weeks after exposure for 2 weeks. At necropsy, T-cells were isolated
from thymus and spleen and cultured in the presence of IL-2, concanavalin
A, and 6-thioguanine (Walker and Skopek, Mutat. Res., 288, 151-162, 1993).
BD exposures of 1 and 2 weeks led to mutagenic effects in mouse thymus,
with the average Mfs being 3- and 5-fold greater than background values,
respectively. In rat thymus, there was only a 1.7- fold increase in Mfs
after 2 weeks of BD exposure. In the mutant expression experiment, hprt Mfs
in thymus and spleen of both species increased for several weeks
post-exposure and then declined. Hprt Mfs in thymus reached maximum levels
at 2 weeks post-exposure in mice (Mfs = 11.3 +/- 2.4 x 10(-6)) and at 3
weeks post-exposure in rats (4.9 +/- 1.2 x 10(-6)), while hprt Mfs in
spleen reached peak levels at 5 weeks post-exposure in mice (19.7 +/- 1.9 x
10(-6)) and 4 weeks post-exposure in rats (10.1 +/- 1.8 x 10(-6)).
Background Mfs for mouse and rat thymus and spleen ranged from 1.6 +/- 0.3
x 10(-6) to 3.0 +/- 1.1 x 10(- 6). Statistical analyses of the hprt Mf data
for spleen demonstrated that, under these exposure conditions, the
mutagenic potency of BD (represented by the difference in the areas under
the phenotypic expression curves of treated versus control animals) was
5-fold greater in mice than in rats. The magnitude of the species
differences in mutagenic potency, observed after 2 weeks of BD exposure,
resembles the species differences in metabolism more closely than the
species differences in cancer potency.
相似文献
63.
64.
The G gamma and A gamma genes of an individual homozygous for the British form of A gamma nondeletion hereditary persistence of fetal hemoglobin have been cloned and partially sequenced. The G gamma gene was normal, but the A gamma gene was found to have a single base change (T----C) at -198 bp relative to the cap site. Supercoiled plasmids containing normal gamma-genes or the mutant A gamma-gene displayed an S1-hypersensitive site immediately 5' to the base change. 相似文献
65.
SYNNÖVE HEIDE 《European journal of oral sciences》1973,81(2):135-144
abstract – Molar pulp tissue of 42 rats was subjected to cardiac perfusion fixation or to immersion fixation with glutaraldehyde and formaldehyde. The importance of variations in pressure and duration of cardiac perfusion was studied. The results indicated that the perfusion method was superior to immersion fixation. Best preservation of the tissues was obtained when perfusion was performed with 1.7% glutaraldehyde for 10–12 min under a pressure of 130 cmH2 O, and leaving the animals for 4 h, without immersion fixation. Also perfusion with formaldehyde resulted in good preservation, provided the solutions were prepared from paraformaldehyde powder. In contrast, solutions made from commercial stock solutions of formaldehyde gave inferior results. For sections stained with hematoxylin-eosin, perfusion with glutaraldehyde was preferable, while perfusion with formaldehyde showed increased sensitivity in demonstration of dentinal tubules stained with alcian blue at pH 3.6. It is suggested that in future studies on rat pulp tissue, perfusion with glutaraldehyde and formaldehyde should replace immersion fixation. 相似文献
66.
MARGRETHE MØLLER J. WRENSEN F. LØVE JEPSEN A. C. THOMSEN 《BJOG : an international journal of obstetrics and gynaecology》1986,93(3):240-244
Summary. Immunofluorescence examination of amniotic fluid for the occurrence of antibody-coated bacteria was carried out in 72 consecutive women with premature rupture of the fetal membranes to assess this method in the diagnosis of intrauterine infection. Antibody-coated bacteria were demonstrated in 11 women with clinical signs of intrauterine infection, histological amnionitis and heavy growth of one bacterial species. The presence of intrauterine infection was considered possible in another 14 women. One patient had no clinical signs of infection, but positive histological and bacteriological evidence; anti-body-coated bacteria were demonstrated in this patient, but not in the remaining 13 women. In 47 women clinical, histological and bacteriological signs of intrauterine infection were absent, and examinations for antibody-coated bacteria were negative in all of them. It is concluded that the demonstration of antibody-coated bacteria in amniotic fluid indicates the presence of intrauterine infection, and the examination may in some cases be positive before the appearance of clinical signs of infection. 相似文献
67.
Murine yolk sac endoderm- and mesoderm-derived cell lines support in vitro growth and differentiation of hematopoietic cells 总被引:3,自引:4,他引:3
The mechanisms involved in the induction of yolk sac mesoderm into blood islands and the role of visceral endoderm and mesoderm cells in regulating the restricted differentiation and proliferation of hematopoietic cells in the yolk sac remain largely unexplored. To better define the role of murine yolk sac microenvironment cells in supporting hematopoiesis, we established cell lines from day-9.5 gestation murine yolk sac visceral endoderm and mesoderm layers using a recombinant retrovirus vector containing Simian virus 40 large T- antigen cDNA. Obtained immortalized cell lines expressed morphologic and biosynthetic features characteristic of endoderm and mesoderm cells from freshly isolated yolk sacs. Similar to the differentiation of blood island hematopoietic cells in situ, differentiation of hematopoietic progenitor cells in vitro into neutrophils was restricted and macrophage production increased when bone marrow (BM) progenitor cells were cultured in direct contact with immortalized yolk sac cell lines as compared with culture on adult BM stromal cell lines. Yolk sac- derived cell lines also significantly stimulated the proliferation of hematopoietic progenitor cells compared with the adult BM stromal cell lines. Thus, yolk sac endoderm- and mesoderm-derived cells, expressing many features of normal yolk sac cells, alter the growth and differentiation of hematopoietic progenitor cells. These cells will prove useful in examining the cellular interactions between yolk sac endoderm and mesoderm involved in early hematopoietic stem cell proliferation and differentiation. 相似文献