全文获取类型
收费全文 | 1651篇 |
免费 | 96篇 |
国内免费 | 2篇 |
专业分类
1749篇 |
出版年
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 26篇 |
2016年 | 38篇 |
2015年 | 56篇 |
2014年 | 53篇 |
2013年 | 120篇 |
2012年 | 113篇 |
2011年 | 124篇 |
2010年 | 59篇 |
2009年 | 67篇 |
2008年 | 110篇 |
2007年 | 104篇 |
2006年 | 102篇 |
2005年 | 114篇 |
2004年 | 118篇 |
2003年 | 97篇 |
2002年 | 108篇 |
2001年 | 25篇 |
2000年 | 12篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有1749条查询结果,搜索用时 15 毫秒
991.
Characterization of prion susceptibility in Neuro2a mouse neuroblastoma cell subclones 总被引:3,自引:0,他引:3
In this study, we established Neuro2a (N2a) neuroblastoma subclones and characterized their susceptibility to prion infection. The N2a cells were treated with brain homogenates from mice infected with mouse prion strain Chandler. Of 31 N2a subclones, 19 were susceptible to prion as those cells became positive for abnormal isoform of prion protein (PrP(Sc)) for up to 9 serial passages, and the remaining 12 subclones were classified as unsusceptible. The susceptible N2a subclones expressed cellular prion protein (PrP(C)) at levels similar to the parental N2a cells. In contrast, there was a variation in PrP(C) expression in unsusceptible N2a subclones. For example, subclone N2a-1 expressed PrP(C) at the same level as the parental N2a cells and prion-susceptible subclones, whereas subclone N2a-24 expressed much lower levels of PrP mRNA and PrP(C) than the parental N2a cells. There was no difference in the binding of PrP(Sc) to prion-susceptible and unsusceptible N2a subclones regardless of their PrP(C) expression level, suggesting that the binding of PrP(Sc) to cells is not a major determinant for prion susceptibility. Stable expression of PrP(C) did not confer susceptibility to prion in unsusceptible subclones. Furthermore, the existence of prion-unsusceptible N2a subclones that expressed PrP(C) at levels similar to prion-susceptible subclones, indicated that a host factor(s) other than PrP(C) and/or specific cellular microenvironments are required for the propagation of prion in N2a cells. The prion-susceptible and -unsusceptible N2a subclones established in this study should be useful for identifying the host factor(s) involved in the prion propagation. 相似文献
992.
993.
Periostin regulates collagen fibrillogenesis and the biomechanical properties of connective tissues 总被引:8,自引:0,他引:8
Norris RA Damon B Mironov V Kasyanov V Ramamurthi A Moreno-Rodriguez R Trusk T Potts JD Goodwin RL Davis J Hoffman S Wen X Sugi Y Kern CB Mjaatvedt CH Turner DK Oka T Conway SJ Molkentin JD Forgacs G Markwald RR 《Journal of cellular biochemistry》2007,101(3):695-711
Periostin is predominantly expressed in collagen-rich fibrous connective tissues that are subjected to constant mechanical stresses including: heart valves, tendons, perichondrium, cornea, and the periodontal ligament (PDL). Based on these data we hypothesize that periostin can regulate collagen I fibrillogenesis and thereby affect the biomechanical properties of connective tissues. Immunoprecipitation and immunogold transmission electron microscopy experiments demonstrate that periostin is capable of directly interacting with collagen I. To analyze the potential role of periostin in collagen I fibrillogenesis, gene targeted mice were generated. Transmission electron microscopy and morphometric analyses demonstrated reduced collagen fibril diameters in skin dermis of periostin knockout mice, an indication of aberrant collagen I fibrillogenesis. In addition, differential scanning calorimetry (DSC) demonstrated a lower collagen denaturing temperature in periostin knockout mice, reflecting a reduced level of collagen cross-linking. Functional biomechanical properties of periostin null skin specimens and atrioventricular (AV) valve explant experiments provided direct evidence of the role that periostin plays in regulating the viscoelastic properties of connective tissues. Collectively, these data demonstrate for the first time that periostin can regulate collagen I fibrillogenesis and thereby serves as an important mediator of the biomechanical properties of fibrous connective tissues. 相似文献
994.
Narumi Ogonuki Yukiko Abe Yoko K. Kurotaki Kazuki Nakao Atsu Aiba Erika Sasaki Atsuo Ogura 《Molecular reproduction and development》2019,86(8):928-930
The common marmoset is a small nonhuman primate in which the application of transgenesis and genetic knockout techniques allows the generation of gene‐modified models of human diseases. However, its longer generation time than that of rodents is a major obstacle to the widespread use of gene‐modified marmosets for biomedical research. In this study, we examined the feasibility of shortening the generation time by using prepubertal marmoset males as gamete donors. We collected late round stage spermatids (Steps 5–7), elongated spermatids, and testicular spermatozoa from the testis of a prepubertal 11‐month‐old male marmoset and injected them into in vitro‐matured oocytes. After 7 days in culture, two embryos from elongated spermatid injection and two embryos from sperm injection were transferred into two separate recipient females. The recipient female that received elongated spermatid injection‐derived embryos became pregnant and gave birth to one female infant. This is the first demonstration that a spermatid from a prepubertal male primate can support full‐term development. Using this method, we can expect to obtain offspring of gene‐modified males 6 months to a year earlier than with natural mating 相似文献
995.
Chemical analysis of constitutive pigmentation of human epidermis reveals constant eumelanin to pheomelanin ratio 下载免费PDF全文
Sandra Del Bino Shosuke Ito Juliette Sok Yukiko Nakanishi Philippe Bastien Kazumasa Wakamatsu Françoise Bernerd 《Pigment cell & melanoma research》2015,28(6):707-717
The skin constitutive pigmentation is given by the amount of melanin pigment, its relative composition (eu/pheomelanin) and distribution within the epidermis, and is largely responsible for the sensitivity to UV exposure. Nevertheless, a precise knowledge of melanins in human skin is lacking. We characterized the melanin content of human breast skin samples with variable pigmentations rigorously classified through the Individual Typology Angle (ITA) by image analysis, spectrophotometry after solubilization with Soluene‐350 and high‐performance liquid chromatography (HPLC) after chemical degradation. ITA and total melanin content were found correlated, ITA and PTCA (degradation product of DHICA melanin), and TTCA (degradation product of benzothiazole‐type pheomelanin) as well but not 4‐AHP (degradation product of benzothiazine‐type pheomelanin). Results revealed that human epidermis comprises approximately 74% of eumelanin and 26% pheomelanin, regardless of the degree of pigmentation. They also confirm the low content of photoprotective eumelanin among lighter skins thereby explaining the higher sensitivity toward UV exposure. 相似文献
996.
Tyrosinase‐catalyzed metabolism of rhododendrol (RD) in B16 melanoma cells: production of RD‐pheomelanin and covalent binding with thiol proteins 下载免费PDF全文
Shosuke Ito Masae Okura Yukiko Nakanishi Makoto Ojika Kazumasa Wakamatsu Toshiharu Yamashita 《Pigment cell & melanoma research》2015,28(3):295-306
RS‐4‐(4‐Hydroxyphenyl)‐2‐butanol (rhododendrol, RD) was reported to induce leukoderma of the skin. To explore the mechanism underlying that effect, we previously showed that oxidation of RD with mushroom tyrosinase produces RD‐quinone, which is converted to secondary quinone products, and we suggested that those quinones are cytotoxic because they bind to cellular proteins and produce reactive oxygen species. We then confirmed that human tyrosinase can oxidize both enantiomers of RD. In this study, we examined the metabolism of RD in B16F1 melanoma cells in vitro. Using 4‐amino‐3‐hydroxy‐n‐butylbenzene as a specific indicator, we detected moderate levels of RD‐pheomelanin in B16F1 cells exposed to 0.3 to 0.5 mM RD for 72 h. We also confirmed the covalent binding of RD‐quinone to non‐protein thiols and proteins through cysteinyl residues. The covalent binding of RD‐quinone to proteins was 20‐ to 30‐fold greater than dopaquinone. These results suggest that the tyrosinase‐induced metabolism of RD causes melanocyte toxicity. 相似文献
997.
Rania Hassan Mohamed Yoichi Sutoh Yasushi Itoh Noriyuki Otsuka Yukiko Miyatake Kazumasa Ogasawara Masanori Kasahara 《PloS one》2015,10(4)
Dendritic epidermal T cells, which express an invariant Vγ5Vδ1 T-cell receptor and account for 95% of all resident T cells in the mouse epidermis, play a critical role in skin immune surveillance. These γδ T cells are generated by positive selection in the fetal thymus, after which they migrate to the skin. The development of dendritic epidermal T cells is critically dependent on the Skint1 gene expressed specifically in keratinocytes and thymic epithelial cells, suggesting an indispensable role for Skint1 in the selection machinery for specific intraepithelial lymphocytes. Phylogenetically, rodents have functional SKINT1 molecules, but humans and chimpanzees have a SKINT1-like (SKINT1L) gene with multiple inactivating mutations. In the present study, we analyzed SKINT1L sequences in representative primate species and found that all hominoid species have a common inactivating mutation, but that Old World monkeys such as olive baboons, green monkeys, cynomolgus macaques and rhesus macaques have apparently functional SKINT1L sequences, indicating that SKINT1L was inactivated in a common ancestor of hominoids. Interestingly, the epidermis of cynomolgus macaques contained a population of dendritic-shaped γδ T cells expressing a semi-invariant Vγ10/Vδ1 T-cell receptor. However, this population of macaque T cells differed from rodent dendritic epidermal T cells in that their Vγ10/Vδ1 T-cell receptors displayed junctional diversity and expression of Vγ10 was not epidermis-specific. Therefore, macaques do not appear to have rodent-type dendritic epidermal T cells despite having apparently functional SKINT1L. Comprehensive bioinformatics analysis indicates that SKINT1L emerged in an ancestor of placental mammals but was inactivated or lost multiple times in mammalian evolution and that Skint1 arose by gene duplication in a rodent lineage, suggesting that authentic dendritic epidermal T cells are presumably unique to rodents. 相似文献
998.
Taichi Kumanomidou Kazuya Nishio Kenji Takagi Tomomi Nakagawa Atsuo Suzuki Takashi Yamane Fuminori Tokunaga Kazuhiro Iwai Arisa Murakami Yukiko Yoshida Keiji Tanaka Tsunehiro Mizushima 《PloS one》2015,10(10)
The Skp1-Cul1-F-box protein (SCF) complex catalyzes protein ubiquitination in diverse cellular processes and is one of the best-characterized ubiquitin ligases. F-box proteins determine the substrate specificities of SCF ubiquitin ligases. Among these, Fbs1/FBG1/FBXO2, Fbs2/FBG2/FBXO6, and Fbs3/FBG5/FBXO27 recognize the N-glycans of glycoproteins, whereas FBG3/FBXO44 has no sugar-binding activity, despite the high sequence homology and conservation of the residues necessary for oligosaccharide binding between Fbs1–3 and FBG3. Here we determined the crystal structure of the Skp1–FBG3 complex at a resolution of 2.6 Å. The substrate-binding domain of FBG3 is composed of a 10-stranded antiparallel β-sandwich with three helices. Although the overall structure of FBG3 is similar to that of Fbs1, the residues that form the Fbs1 carbohydrate-binding pocket failed to be superposed with the corresponding residues of FBG3. Structure-based mutational analysis shows that distinct hydrogen bond networks of four FBG3 loops, i.e., β2-β3, β5-β6, β7-β8, and β9-β10, prevent the formation of the carbohydrate-binding pocket shown in Fbs1. 相似文献
999.
Immune Tolerance Induction Using Fetal Directed Placental Injection in Rodent Models: A Murine Model
Kei Takahashi Masayuki Endo Takekazu Miyoshi Mitsuhiro Tsuritani Yukiko Shimazu Hiroshi Hosoda Kotaro Saga Katsuto Tamai Alan W. Flake Jun Yoshimatsu Tadashi Kimura 《PloS one》2015,10(4)
Objectives
Induction of the immune response is a major problem in replacement therapies for inherited protein deficiencies. Tolerance created in utero can facilitate postnatal treatment. In this study, we aimed to induce immune tolerance towards a foreign protein with early gestational cell transplantation into the chorionic villi under ultrasound guidance in the murine model.Methods
Pregnant C57BL/6 (B6) mice on day 10 of gestation were anesthetized and imaged by high resolution ultrasound. Murine embryos and their placenta were positioned to get a clear view in B-mode with power mode of the labyrinth, which is the equivalent of chorionic villi in the human. Bone marrow cells (BMCs) from B6-Green Fluorescence Protein (B6GFP) transgenic mice were injected into the fetal side of the placenta which includes the labyrinth with glass microcapillary pipettes. Each fetal mouse received 2 x 105 viable GFP-BMCs. After birth, we evaluated the humoral and cell-mediated immune response against GFP.Results
Bone marrow transfer into fetal side of placenta efficiently distributed donor cells to the fetal mice. The survival rate of this procedure was 13.5%(5 out of 37). Successful engraftment of the B6-GFP donor skin grafts was observed in all recipient (5 out of 5) mice 6 weeks after birth. Induction of anti-GFP antibodies was completely inhibited. Cytotoxic immune reactivity of thymic cells against cells harboring GFP was suppressed by ELISPOT assay.Conclusions
In this study, we utilized early gestational placental injection targeting the murine fetus, to transfer donor cells carrying a foreign protein into the fetal circulation. This approach is sufficient to induce both humoral and cell-mediated immune tolerance against the foreign protein. 相似文献1000.
Ichiro Murakami Yukiko Oh Akira Morimoto Hitoshi Sano Susumu Kanzaki Michiko Matsushita Takeshi Iwasaki Satoshi Kuwamoto Masako Kato Keiko Nagata Kazuhiko Hayashi Shinsaku Imashuku Jean Gogusev Francis Jaubert Takashi Oka Tadashi Yoshino 《Clinical proteomics》2015,12(1)