首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   73篇
  免费   1篇
  国内免费   3篇
  2022年   1篇
  2015年   1篇
  2014年   1篇
  2013年   3篇
  2011年   2篇
  2010年   1篇
  2009年   5篇
  2008年   2篇
  2007年   3篇
  2006年   3篇
  2005年   1篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  2001年   1篇
  1997年   3篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1992年   1篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1975年   2篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1967年   1篇
  1959年   2篇
  1958年   3篇
  1957年   4篇
  1956年   1篇
  1955年   1篇
  1952年   3篇
  1951年   1篇
  1950年   1篇
排序方式: 共有77条查询结果,搜索用时 15 毫秒
31.
32.
The occurrence and distribution of neuropeptide-containing fibres in the human parotid gland were examined by the peroxidase--antiperoxidase method with attention to the quality of fixation and the condition of patients. Many fibres immunoreactive for neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) and a moderate number of galanin- positive (GAL) fibres were distributed around the acini. A moderate number of NPY and VIP fibres were distributed around the intercalated ducts. The semiquantitative mean densities (_SD) of periacinar NPY, VIP and GAL fibres expressed as a percentage of the total protein gene product (PGP) 9.5 immunoreactive fibres were 75.62 _ 7.25%, 70.52 _ 9.33% and 41.76 _ 5.45%, respectively, whereas those of substance P (SP), calcitonin gene-related peptide (CGRP) and FMRF amide (FMRF) fibres were below 10%. The mean densities of NPY and VIP fibres around the intercalated ducts expressed as the percentage of PGP 9.5 fibres associated with these ducts were 52.37 _ 6.19% and 59.62 _ 7.02% respectively. Those of SP, CGRP, GAL, and FMRF fibres were below 10%. The densities of NPY, VIP, SP, CGRP, GAL and FMRF fibres around the striated and excretory ducts were also below 10%. In the vasculature, NPY fibres were the most prominent. Similarly, the mean density of perivascular NPY fibres was 93.76 _ 2.03%. No somatostatin or leucine or methionine enkephalin immunoreactivity was detected around the acini, duct system or blood vessels. These findings suggest that, in this gland, the periacinar NPY, VIP and GAL fibres may participate in regulating the synthesis of saliva and its secretion and that perivascular peptidergic fibres, especially NPY fibres, may be involved in controlling local blood flow This revised version was published online in November 2006 with corrections to the Cover Date.  相似文献   
33.
In the blastula of the sea urchin, Anthocidaris crassispina , a small number of primary mesenchyme cells (PMCs) ingressed from the blastocoel wall taking a bottle shape. The majority of the PMCs followed the first group of PMCs. These ingressed without taking the bottle shape, and became round within the blastocoel wall. After ingression, the PMCs migrated as single cells retaining their round cell contour. The average velocity of their migration was 13.3 μm/hr.
The blastocoel contained Alcian blue (pH 1.0)-positive material which changed its light microscopic configuration from being amorphous in the hatched and mesenchyme blastulae to being fibrous in the early gastrulae. Ultrastructurally, the blastocoelic material in the hatched blastulae was composed of 27 nm diameter granules. In the mesenchyme blastulae and the early gastrulae relatively long 15 nm diameter fibers were seen in addition to the 27 nm diameter granules. The 27 nm diameter granules bound the ruthenium red while the 15 nm diameter fibers did not. The 27 nm diameter granules formed aggregates in the hatched blastulae, and were bound to the 15 nm diameter fibers in the mesenchyme blastulae and early gastrulae to form a fibrous network which was observed by a light microscope.  相似文献   
34.
Summary

In the present study, an attempt was made to clarify the timing of the transition from proliferation stage to pupal preparation stage of Bombyx wing discs and the correlation of its timing and ecdysteroid release. An histological study was carried out during the period of ecdysteroid increase in hemolymph in the last larval instar. The number of mitoses in wing discs from the feeding stage to the spinning stage was counted. During the feeding stage, the number of mitoses was about 200/disc, with the number increasing up to about 850/disc on the day of the beginning of spinning (S0); it then decreased to about 250/disc at the S1 stage, and finally mitotic figures were absent at S2. Comparing the mitotic number with hemolymph ecdysteroid titer, ecdysteroid during the high mitotic period is close to 100ng/ml, while ecdysteroid during the low mitotic period is about 10ng/ml at day 5 and 500ng/ml at S1, respectively. Two-dimensional gel electrophoresis was carried out to identify the ecdysone-induced polypeptides or the polypeptides synthesized during the spinning stage. Five ecdysteroid-inducible polypeptides were observed during the spinning stage or after 20-hydroxyecdysone (20E) treatment. From these findings, low concentrations of ecdysteroid induce cell proliferation, whereas high concentrations inhibit cell proliferation and induce new protein synthesis.  相似文献   
35.
The pattern and intensity of pigmentation have direct impact on individual fitness through various ecological factors. In a Drosophila melanogaster population from southern Japan, thoracic trident pigmentation intensity of most of the strains could be classified into Dark or Light‐type. The expression level variation of the ebony gene correlated well with this phenotype and the allelic differences in expression indicated that the variation is partly due to cis‐regulatory changes. In the ~13 kb gene region, we identified 17 nucleotide sites and 2 indels that were in complete association with the thoracic trident pigmentation intensity. Interestingly, 11 out of 19 sites located within ~0.5 kb of the core epidermis enhancer. These sites had no obvious association with the abdominal pigmentation intensity in the previously analysed African populations from Uganda and Kenya, which suggested that multiple potential mutational pathways in the cis‐regulatory control region of a single gene could lead to similar phenotypic variation within this species. We also found that the Light‐type enhancer haplotype is strongly linked to a cosmopolitan inversion, In(3R)Payne, which is predominant in warmer climatic regions in both hemispheres. The sequence pattern suggested that the strong linkage may be due to selective forces related to thermal adaptation. The inferred selection for lighter pigmentation in the Japanese population is in the opposite direction of the previously reported case of selection for darker individuals in African populations. Nevertheless, both adaptive changes involved cis‐regulatory changes of ebony, which shows that this gene is likely to be a common target of natural selection.  相似文献   
36.
Structure and Role of the Five Glycopeptides of Human IgM Immunoglobulins   总被引:5,自引:0,他引:5  
Carbohydrate is attached at five sites in the constant sequence region of the µ heavy chain of human IgM. The oligosaccharides are of two kinds, simple and complex and affect the conformation and properties of macroglobulins.  相似文献   
37.
38.
39.
ABSTRACT. To locate the photoreceptor involved in the photoperiodic induction of diapause in Bombyx mori L., covering of larval head with black paint or local illumination using chemiluminescent paint was carried out. A silkworm race showing a response of long-day type during the larval stage was employed. The results demonstrated that the photoreceptor is located in the head but is extraocular. The optical properties of the larval body suggest that during the first and second stadia light is admitted through the translucent clypeus of the head, but during later stadia enters over the entire larval body including the head, and that it reaches the cerebral lobe where a photoreceptor is possibly located.  相似文献   
40.
By applying the double diffusion technique of Ouchterlony and the immunoelectrophoresis, sequence in the appearance of antigens reactive with antisera against HbCOs from 5-day embryos and adult chickens, and the major component of adult HbCO in the course of chicken development has been studied.
Antigenic components reacting to antiserum against HbCO from 5-day embryos have been detected throughout development. Three globin-like components specific to early embryos are detectable in embryos to 2 days of incubation. Two Hb components are detectable in embryos from 3 to 5 days of incubation; one is apparently specific to embryos, while the other seems to be somewhat different from adult Hb. After 6 days of incubation only one adult Hb component is detectable.
Antigenic components reacting to antiserum against HbCO from adults have also been detectable throughout embryonic life. One globin-like component specific to early embryos can be found in embryos to 2 days of incubation. One or two Hb components which are probably specific to embryos can be detected in embryos from 3 to 5 days of incubation. After 6 days of incubation one adult Hb component is detectable, while one globin-like component specific to adults can be found after 15 days of incubation. Further, the other globin-like component is detectable after 3 days of incubation.
Antigenic components reacting to antiserum against the major component of adult HbCO have been detected throughout development; one which seems to be somewhat different from either adult Hb components can be found in embryos from 2 to 5 days of incubation, while the other which is identical with the major component of adult Hb is detectable after 6 days of incubation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号