全文获取类型
收费全文 | 251篇 |
免费 | 17篇 |
出版年
2022年 | 2篇 |
2021年 | 13篇 |
2020年 | 1篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 21篇 |
2013年 | 10篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 24篇 |
2007年 | 25篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1988年 | 1篇 |
1979年 | 1篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 31 毫秒
91.
Role of auxin in regulating Arabidopsis flower development 总被引:2,自引:0,他引:2
To elucidate the role of auxin in flower morphogenesis, its distribution patterns were studied during flower development in
Arabidopsis thaliana (L.) Heynh. Expression of DR5::GUS was regarded to reflect sites of free auxin, while immunolocalization with auxin polyclonal antibodies visualized conjugated
auxin distribution. The youngest flower bud was loaded with conjugated auxin. During development, the apparent concentration
of free auxin increased in gradual patterns starting at the floral-organ tip. Anthers are major sites of high concentrations
of free auxin that retard the development of neighboring floral organs in both the acropetal and basipetal directions. The
IAA-producing anthers synchronize flower development by retarding petal development and nectary gland activity almost up to
anthesis. Tapetum cells of young anthers contain free IAA which accumulates in pollen grains, suggesting that auxin promotes
pollen-tube growth towards the ovules. High amounts of free auxin in the stigma induce a wide xylem fan immediately beneath
it. After fertilization, the developing embryos and seeds show elevated concentrations of auxin, which establish their axial
polarity. This developmental pattern of auxin production during floral-bud development suggests that young organs which produce
high concentrations of free IAA inhibit or retard organ-primordium initiation and development at the shoot tip.
Electronic Supplementary Material Supplementary material is available for this article at
This paper is dedicated to Orna Aloni for continuous support and management over many years. 相似文献
92.
Markus J Strasser Natalia C Mackenzie Karin Dumstrei La-Iad Nakkrasae Jürg Stebler Erez Raz 《BMC developmental biology》2008,8(1):1-16
Background
The founding member of the EMAP-like protein family is the Echinoderm Microtubule-Associated Protein (EMAP), so-named for its abundance in sea urchin, starfish, and sand dollar eggs. The EMAP-like protein family has five members in mammals (EML1 through EML5) and only one in both Drosophila (ELP-1) and C. elegans (ELP-1). Biochemical studies of sea urchin EMAP and vertebrate EMLs implicate these proteins in the regulation of microtubule stability. So far, however, the physiological function of this protein family remains unknown.Results
We examined the expression pattern of C. elegans ELP-1 by means of transgenic gene expression in living embryos and adults, and by immunolocalization with an ELP-1-specific antibody in fixed tissues. In embryos, ELP-1 is expressed in the hypodermis. In larvae and adults, ELP-1 is expressed in the body wall, spermatheca and vulval muscles, intestine, and hypodermal seam cells. In muscle, ELP-1 is associated with adhesion complexes near the cell surface and is bound to a criss-crossing network of microtubules in the cytoplasm. ELP-1 is also expressed in a subset of mechanoreceptor neurons, including the ray neurons in the male tail, microtubule-rich touch receptor neurons, and the six ciliated IL1 neurons. This restricted localization in the nervous system implies that ELP-1 plays a role in mechanotransmission. Consistent with this idea, decreasing ELP-1 expression decreases sensitivity to gentle touch applied to the body wall.Conclusion
These data imply that ELP-1 may play an important role during the transmission of forces and signals between the body surface and both muscle cells and touch receptor neurons. 相似文献93.
94.
95.
Erez?ShohamEmail authorView authors OrcID profile Yehuda?Benayahu 《Coral reefs (Online)》2017,36(1):71-81
Mesophotic coral-reef ecosystems (MCEs), which comprise the light-dependent communities of corals and other organisms found at depths between 30 and ~ 150 m, have received very little study to date. However, current technological advances, such as remotely operated vehicles and closed-circuit rebreather diving, now enable their thorough investigation. Following the reef-building stony corals, octocorals are the second most common benthic component on many shallow reefs and a major component on deep reefs, the Red Sea included. This study is the first to examine octocoral community features on upper MCEs based on species-level identification and to compare them with the shallower reef zones. The study was carried out at Eilat (Gulf of Aqaba, northern Red Sea), comparing octocoral communities at two mesophotic reefs (30–45 m) and two shallow reef zones (reef flat and upper fore-reef) by belt transects. A total of 30 octocoral species were identified, with higher species richness on the upper MCEs compared to the shallower reefs. Although the MCEs were found to host a higher number of species than the shallower reefs, both featured a similar diversity. Each reef zone revealed a unique octocoral species composition and distinct community structure, with only 16% of the species shared by both the MCEs and the shallower reefs. This study has revealed an almost exclusive dominance of zooxanthellate species at the studied upper MCE reefs, thus indicating an adequate light regime for photosynthesis there. The findings should encourage similar studies on other reefs, aimed at understanding the spatiotemporal features and ecological role of octocorals in reef ecosystems down to the deepest limit of the MCEs. 相似文献
96.
Regulation of zebrafish primordial germ cell migration by attraction towards an intermediate target. 总被引:1,自引:0,他引:1
Gilbert Weidinger Uta Wolke Marion K?prunner Christine Thisse Bernard Thisse Erez Raz 《Development (Cambridge, England)》2002,129(1):25-36
Migration of primordial germ cells (PGCs) from their site of specification towards the developing gonad is controlled by directional cues from somatic tissues. Although in several animals the PGCs are attracted by signals emanating from their final target, the gonadal mesoderm, little is known about the mechanisms that control earlier steps of migration. We provide evidence that a key step of zebrafish PGC migration, in which the PGCs become organized into bilateral clusters in the anterior trunk, is regulated by attraction of PGCs towards an intermediate target. Time-lapse observations of wild-type and mutant embryos reveal that bilateral clusters are formed at early somitogenesis, owing to migration of PGCs towards the clustering position from medial, posterior and anterior regions. Furthermore, PGCs migrate actively relative to their somatic neighbors and they do so as individual cells. Using mutants that exhibit defects in mesoderm development, we show that the ability to form PGC clusters depends on proper differentiation of the somatic cells present at the clustering position. Based on these findings, we propose that these somatic cells produce signals that attract PGCs. Interestingly, fate-mapping shows that these cells do not give rise to the somatic tissues of the gonad, but rather contribute to the formation of the pronephros. Thus, the putative PGC attraction center serves as an intermediate target for PGCs, which later actively migrate towards a more posterior position. This final step of PGC migration is defective in hands off mutants, where the intermediate mesoderm of the presumptive gonadal region is mispatterned. Our results indicate that zebrafish PGCs are guided by attraction towards two signaling centers, one of which may represent the somatic tissues of the gonad. 相似文献
97.
Habitat selection in evolving mole rats 总被引:1,自引:0,他引:1
Summary The actively speciating four chromosomal species of fossorial mole rats of the Spalax ehrenbergi complex in Israel (2n=52, 58, 54 and 60) which inhabit an increasingly arid environment in this order were tested to determine their habitat preference. The testing apparatus simulated four climatic regimes based on temperature and humidity combinations corresponding to the climatic origins of the four chromosomal species: coolhumid, cool-dry, warm-humid and warm-dry, respectively. The tests involved 175 adults comprising all four chromosome species and representing 10 populations. Out of the 139 analyzed animals 88% selected the warm cages and only 12% selected the cool cages. The four karyotype progressively preferred the warm-dry cage in the following order: 53, 59, 60 and 72% for 2n=58, 52, 54 and 60 respectively, largely in accord with their increasingly arid climatic origins. Even larger differences were found in populations within karyotypes in accord with the local climatic variation within a karyotype range.The results of our analysis indicate that the chromosomal species and populations select their climatic habitat in accord with the climatic conditions of their geographic localities. The humidity index appears to be the prime differentiator of habitat selection and may have been a substantial ecological factor in species differentiation and distribution of the Spalax ehrenbergi complex in Israel. 相似文献
98.
Primordial germ cell migration in the chick and mouse embryo: the role of the chemokine SDF-1/CXCL12
Stebler J Spieler D Slanchev K Molyneaux KA Richter U Cojocaru V Tarabykin V Wylie C Kessel M Raz E 《Developmental biology》2004,272(2):351-361
As in many other animals, the primordial germ cells (PGCs) in avian and reptile embryos are specified in positions distinct from the positions where they differentiate into sperm and egg. Unlike in other organism however, in these embryos, the PGCs use the vascular system as a vehicle to transport them to the region of the gonad where they exit the blood vessels and reach their target. To determine the molecular mechanisms governing PGC migration in these species, we have investigated the role of the chemokine stromal cell-derived factor-1 (SDF-1/CXCL12) in guiding the cells towards their target in the chick embryo. We show that sdf-1 mRNA is expressed in locations where PGCs are found and towards which they migrate at the time they leave the blood vessels. Ectopically expressed chicken SDF-1alpha led to accumulation of PGCs at those positions. This analysis, as well as analysis of gene expression and PGC behavior in the mouse embryo, suggest that in both organisms, SDF-1 functions during the second phase of PGC migration, and not at earlier phases. These findings suggest that SDF-1 is required for the PGCs to execute the final migration steps as they transmigrate through the blood vessel endothelium of the chick or the gut epithelium of the mouse. 相似文献
99.
Khen Khermesh Anna Maria D'Erchia Michal Barak Anita Annese Chaim Wachtel Erez Y. Levanon Ernesto Picardi Eli Eisenberg 《RNA (New York, N.Y.)》2016,22(2):290-302
Adenosine to inosine (A-to-I) RNA editing, catalyzed by the ADAR enzyme family, acts on dsRNA structures within pre-mRNA molecules. Editing of the coding part of the mRNA may lead to recoding, amino acid substitution in the resulting protein, possibly modifying its biochemical and biophysical properties. Altered RNA editing patterns have been observed in various neurological pathologies. Here, we present a comprehensive study of recoding by RNA editing in Alzheimer''s disease (AD), the most common cause of irreversible dementia. We have used a targeted resequencing approach supplemented by a microfluidic-based high-throughput PCR coupled with next-generation sequencing to accurately quantify A-to-I RNA editing levels in a preselected set of target sites, mostly located within the coding sequence of synaptic genes. Overall, editing levels decreased in AD patients’ brain tissues, mainly in the hippocampus and to a lesser degree in the temporal and frontal lobes. Differential RNA editing levels were observed in 35 target sites within 22 genes. These results may shed light on a possible association between the neurodegenerative processes typical for AD and deficient RNA editing. 相似文献
100.
Tomer Israely Sharon Melamed Hagit Achdout Noam Erez Boaz Politi Trevor Waner Shlomo Lustig Nir Paran 《PloS one》2014,9(10)
Eradication of smallpox and discontinuation of the vaccination campaign resulted in an increase in the percentage of unvaccinated individuals, highlighting the need for postexposure efficient countermeasures in case of accidental or deliberate viral release. Intranasal infection of mice with ectromelia virus (ECTV), a model for human smallpox, is curable by vaccination with a high vaccine dose given up to 3 days postexposure. To further extend this protective window and to reduce morbidity, mice were vaccinated postexposure with Vaccinia-Lister, the conventional smallpox vaccine or Modified Vaccinia Ankara, a highly attenuated vaccine in conjunction with TLR3 or TLR9 agonists. We show that co-administration of the TLR3 agonist poly(I:C) even 5 days postexposure conferred protection, avoiding the need to increase the vaccination dose. Efficacious treatments prevented death, ameliorated disease symptoms, reduced viral load and maintained tissue integrity of target organs. Protection was associated with significant elevation of serum IFNα and anti-vaccinia IgM antibodies, modulation of IFNγ response, and balanced activation of NK and T cells. TLR9 agonists (CpG ODNs) were less protective than the TLR3 agonist poly(I:C). We show that activation of type 1 IFN by poly(I:C) and protection is achievable even without co-vaccination, requiring sufficient amount of the viral antigens of the infective agent or the vaccine. This study demonstrated the therapeutic potential of postexposure immune modulation by TLR activation, allowing to alleviate the disease symptoms and to further extend the protective window of postexposure vaccination. 相似文献