全文获取类型
收费全文 | 149篇 |
免费 | 1篇 |
国内免费 | 4篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 15 毫秒
91.
Ayano Harata Mika Hirakawa Tetsushi Sakuma Takashi Yamamoto Chikara Hashimoto 《Development, growth & differentiation》2019,61(2):186-197
Vertebrates have unique head structures that are mainly composed of the central nervous system, the neural crest, and placode cells. These head structures are brought about initially by the neural induction between the organizer and the prospective neuroectoderm at early gastrula stage. Purinergic receptors are activated by nucleotides released from cells and influence intracellular signaling pathways, such as phospholipase C and adenylate cyclase signaling pathways. As P2Y receptor is vertebrate-specific and involved in head formation, we expect that its emergence may be related to the acquisition of vertebrate head during evolution. Here, we focused on the role of p2ry4 in early development in Xenopus laevis and found that p2ry4 was required for the establishment of the head organizer during neural induction and contributed to head formation. We showed that p2ry4 was expressed in the head organizer region and the prospective neuroectoderm at early gastrula stage, and was enriched in the head components. Disruption of p2ry4 function resulted in the small head phenotype and the reduced expression of marker genes specific for neuroectoderm and neural border at an early neurula stage. Furthermore, we examined the effect of p2ry4 disruption on the establishment of the head organizer and found that a reduction in the expression of head organizer genes, such as dkk1 and cerberus, and p2ry4 could also induce the ectopic expression of these marker genes. These results suggested that p2ry4 plays a key role in head organizer formation. Our study demonstrated a novel role of p2ry4 in early head development. 相似文献
92.
The dorsal marginal zone (DMZ) of the amphibian embryo is a key embryonic region involved in body axis organization and neural induction. Using time-lapse microscopic magnetic resonance imaging (MRI), we follow the pregastrula movements that lead to the formation of the DMZ of the stage 10 Xenopus embryo. 2D and 3D MRI time-lapse series reveal that pregastrular movements change the tissue architecture of the DMZ at earlier stages and in a different fashion than previously appreciated. Beginning at stage 9, epiboly of the animal cap moves tissue into the dorsal but not into the ventral marginal zone, resulting in an asymmetry between the dorsal and the ventral sides. Time-lapse imaging of labeled blastomeres shows that the animal cap tissue moves into the superficial DMZ overlying the deeper mesendoderm of the DMZ. The shearing of superficial tissue over the deeper mesendoderm creates the radial/vertical arrangement of ectoderm outside of mesendoderm within the DMZ, which is independent of involution and prior to the formation of the dorsal blastoporal lip. This tilting of the DMZ is distinct from, but occurs synchronously with, the vegetal rotation of the vegetal cell mass [R., Winklbauer, M., Schürfeld (1999). "Vegetal rotation, a new gastrulation movement involved in the internalization of the mesoderm and endoderm in Xenopus." Development. 126, 3703-3713.]. We present a revised model of gastrulation movements in Xenopus laevis. 相似文献
93.
94.
Lakshmi Subramanian Ryan Remedios Ashwin Shetty Shubha Tole 《Seminars in cell & developmental biology》2009,20(6):712-718
The early cortical primordium develops from a sheet of neuroepithelium that is flanked by distinct signaling centers. Of these, the hem and the antihem are positioned as longitudinal stripes, running rostro-caudally along the medial and lateral faces, respectively, of each telencepahlic hemisphere. In this review we examine the similarities and differences in how these two signaling centers arise, their roles in patterning adjacent tissues, and the cells and structures they contribute to. Since both the hem and the antihem have been identified across many vertebrate phyla, they appear to be part of an evolutionary conserved set of mechanisms that play fundamental roles in forebrain development. 相似文献
95.
JELENA MLINAREC DRAEN A. PAPE VINJA BESENDORFER 《Botanical journal of the Linnean Society. Linnean Society of London》2006,150(2):177-186
The karyotype of the Mediterranean species Anemone hortensis L. (Ranunculaceae) was characterized with emphasis on heterochromatin distribution and localization of ribosomal (18S−5.8S−26S and 5S rDNA) and telomeric repeats (TTTAGGG). Diploid chromosome complement, 2 n = 2 x = 16, common to all investigated populations, consisted of three acrocentric, one meta-submetacentric and four metacentric chromosomes ranging in size from 6.34 to 10.47 µm. Fluorescence in situ hybridization (FISH) with 18S and 5S rDNA probes revealed two 18S−5.8S−26S rDNA loci on a satellite and secondary constriction of acrocentric chromosome pair 2 and terminally on acrocentric chromosome pair 3, and two 5S rDNA loci in the pericentromeric region of meta-submetacentric chromosome pair 4 and in the proximity of the 18S−5.8S−26S rDNA locus on chromosome pair 2. The only GC-rich heterochromatin, as revealed by fluorochrome Chromomycin A3 staining, was that associated with nucleolar organizer regions, whereas AT-rich heterochromatin, stained with 4,6-diamino-2-phenylindole (DAPI), was distributed intercalarly and terminally on the long arm of all three acrocentric chromosomes, and terminally on chromosomes 4 and 5. FISH with Arabidopsis -type telomeric repeats (TTTAGGG) as a probe revealed two classes of signals, small dot-like and large bands, at chromosome termini exclusively, where they corresponded to terminal DAPI-stained heterochromatin. Heteromorphism of chromosome pair 4, which refers to terminal DAPI bands and FISH signals, was observed in populations of Anemone hortensis . Chromosome pairing during meiosis was regular with formation of localized chiasmata proximal to the centromere. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 177–186. 相似文献
96.
《Current biology : CB》2020,30(9):1626-1638.e3
- Download : Download high-res image (138KB)
- Download : Download full-size image
97.
Xenopus organizer specific gene noggin possesses nearly all the characterestic properties of the action of organizer to specify the embryonic body acis.To analyze how the maternal inherited factors control its expression pattern,we cloned the 5‘ regulatory region of noggin gene.The 1.5 kb upstream sequense could direct reporter gene to express in vivo and data from deletion analysis indicated that a 229 base pair fragmet is essential for activating noggin expression.We further demonstrated that the response elements within this regulatory region were indeed under the control of growth factor activin and Wnt signaling pathway components. 相似文献
98.
Stavale LM Schneider MC Araujo D Brescovit AD Cella DM 《Genetics and molecular biology》2010,33(4):663-668
Theridiidae is a derived family within the Araneoidea clade. In contrast to closely related groups, the 2n(male) = 20+X(1) X (2) with acro/telocentric chromosomes is the most widespread karyotype among the theridiid spiders. In this work, the cytogenetic analysis of Argyrodes elevatus revealed original chromosome features different from those previously registered for Theridiidae, including the presence of 2n(male) = 20+X with meta/submetacentric chromosomes. Most individuals of Nesticodes rufipes showed family conserved karyotype characteristics. However, one individual had a 2n(male) = 24 due to the presence of an extra chromosome pair, which exhibited regular behavior and reductional segregation during meiosis. After silver staining, mitotic cells exhibited NORs localized on the terminal regions of the short arms of pairs 2, 3, and 4 of A. elevatus and on the terminal regions of long arms of pair 4 of N. rufipes. The comparative analysis with data from phylogenetically related species allowed the clarification of the origin of the interspecific and intraspecific chromosome variability observed in Argyrodes and in N. rufipes, respectively. 相似文献
99.
Daisuke Kurokawa Tomomi Ohmura Hajime Ogino Ai Inoue Yoko Suda 《Developmental biology》2010,342(1):110-403
In the mouse, the Otx2 gene has been shown to play essential roles in the visceral endoderm during anterior-posterior axis formation and head induction. While these are primary processes in vertebrate embryogenesis, the visceral endoderm is a tissue unique to mammals. Two enhancers (VE and CM) have been previously found to direct Otx2 expression during early embryogenesis. This study demonstrates that in anterior visceral endoderm the CM enhancer does not have an activity by itself, but enhances the activity of the VE enhancer. These two enhancers also cooperate for the activities in anterior mesendoderm and cephalic mesenchyme. Comparative studies suggest that VE enhancer function was most likely established before the divergence of sarcopterygians into Actinistia, Dipnoi and tetrapods, while the nucleotide sequence corresponding to the VE enhancer was already present in the last common ancestor of bony fishes. The CM enhancer sequence and function would have been also established in ancestral sarcopterygians. The VE/CM enhancers and their gene cascades in the ancestral sarcopterygian head organizer would then have been co-opted by amphibian deep endoderm cells and mammalian visceral endoderm cells for the head development. 相似文献
100.
Formation of the dorsal organizer (Spemann organizer) is an important process in early vertebrate development. In zebrafish, two molecular cascades—Bozozok/Dharma (Boz) and Nodal signaling—act in parallel to induce the dorsal organizer. However, the complete molecular mechanism regulating this event remains unclear. Here we report that zebrafish cell lines derived from various developmental stages can induce a secondary axis when they are implanted into the mid-blastula but not the early gastrula. The implanted cellsthemselves did not differentiate, but instead induced ectopic expression of dorsal organizer markers incells around the implanted cells and induced notochord formation in the secondary axis. These results indicate that cultured cell lines have the ability to induce a secondary axis through the initiation of dorsal organizer activity. However, ectopic expression of boz and sqt were not observed in cultured cells. In addition, implanted cell lines could induce the dorsal organizer even in maternal-zygotic one-eyed pinhead mutants, which are not responsive to Nodal signaling. Finally, the Nodal signaling pathway was not activatedfollowing implantation of cultured cells. Collectively, these data suggest that zebrafish cell lines induce the dorsal organizer independent of the boz and Nodal signaling pathways. 相似文献