全文获取类型
收费全文 | 967篇 |
免费 | 58篇 |
专业分类
1025篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 29篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 45篇 |
2014年 | 46篇 |
2013年 | 54篇 |
2012年 | 83篇 |
2011年 | 82篇 |
2010年 | 38篇 |
2009年 | 40篇 |
2008年 | 70篇 |
2007年 | 79篇 |
2006年 | 50篇 |
2005年 | 44篇 |
2004年 | 51篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1971年 | 4篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有1025条查询结果,搜索用时 15 毫秒
91.
92.
Yasunaga M Tada S Torikai-Nishikawa S Nakano Y Okada M Jakt LM Nishikawa S Chiba T Era T Nishikawa S 《Nature biotechnology》2005,23(12):1542-1550
Preparation of specific lineages at high purities from embryonic stem (ES) cells requires both selective culture conditions and markers to guide and monitor the differentiation. In this study, we distinguished definitive and visceral endoderm by using a mouse ES cell line that bears the gfp and human IL2R alpha (also known as CD25) marker genes in the goosecoid (Gsc) and Sox17 loci, respectively. This cell line allowed us to monitor the generation of Gsc+ Sox17+ definitive endoderm and Gsc- Sox17+ visceral endoderm and to define culture conditions that differentially induce definitive and visceral endoderm. By comparing the gene expression profiles of definitive and visceral endoderm, we identified seven surface molecules that are expressed differentially in the two populations. One of the seven markers, Cxcr4, to which a monoclonal antibody is available allowed us to monitor and purify the Gsc+ population from genetically unmanipulated ES cells under the condition that selects definitive endoderm. 相似文献
93.
The RNA binding protein TLS is translocated to dendritic spines by mGluR5 activation and regulates spine morphology 总被引:1,自引:0,他引:1
Fujii R Okabe S Urushido T Inoue K Yoshimura A Tachibana T Nishikawa T Hicks GG Takumi T 《Current biology : CB》2005,15(6):587-593
Neuronal dendrites, together with dendritic spines, exhibit enormously diverse structure. Selective targeting and local translation of mRNAs in dendritic spines have been implicated in synapse remodeling or synaptic plasticity. The mechanism of mRNA transport to the postsynaptic site is a fundamental question in local dendritic translation. TLS (translocated in liposarcoma), previously identified as a component of hnRNP complexes, unexpectedly showed somatodendritic localization in mature hippocampal pyramidal neurons. In the present study, TLS was translocated to dendrites and was recruited to dendrites not only via microtubules but also via actin filaments. In mature hippocampal pyramidal neurons, TLS accumulated in the spines at excitatory postsynapses upon mGluR5 activation, which was accompanied by an increased RNA content in dendrites. Consistent with the in vitro studies, TLS-null hippocampal pyramidal neurons exhibited abnormal spine morphology and lower spine density. Our results indicate that TLS participates in mRNA sorting to the dendritic spines induced by mGluR5 activation and regulates spine morphology to stabilize the synaptic structure. 相似文献
94.
Hegab AE Sakamoto T Saitoh W Nomura A Ishii Y Morishima Y Iizuka T Kiwamoto T Matsuno Y Massoud HH Massoud HM Hassanein KM Sekizawa K 《Biochemical and biophysical research communications》2005,329(4):1246-1252
It is recognized that genetic factors play a role in the susceptibility to COPD. COPD is characterized by airflow limitation. Chronic inflammation causes small airway disease and parenchymal destruction, leading to the airflow limitation. Polymorphisms in pro-inflammatory cytokine genes may confer a risk for the development of COPD. A case-control association study was performed in Japanese population (88 COPD patients and 61 controls) and Egyptian population (106 patients and 72 controls). Genotype and allele frequencies of the TNFalpha -308 G/A and +489 G/A polymorphisms, the IL1beta -511 C/T, -31 T/C, and +3954 C/T polymorphisms, and a VNTR polymorphism in intron 2 of the IL1RN gene were investigated. In addition, pairwise haplotype frequencies were analyzed. When studied independently, none of the polymorphisms were associated with the development of COPD in both populations. However, in the Egyptian population, the distributions of the haplotype (IL1beta -31 T/C : IL1beta +3954 C/T) were significantly different between the COPD patients and the controls (p(corr)=0.0037). Our findings suggest that this haplotype within the IL1beta gene may be involved in the pathogenesis of COPD and that the genetic factors of COPD susceptibility might be different between different populations. 相似文献
95.
96.
Sugiura M Rappaport F Brettel K Noguchi T Rutherford AW Boussac A 《Biochemistry》2004,43(42):13549-13563
Site-directed mutagenesis in the photosystem II (PSII) oxygen-evolving enzyme was achieved in the thermophilic cyanobacterium Thermosynechococcus elongatus. PSII from this species is the focus of attention because its robustness makes it suitable for enzymological and biophysical studies. PSII, which lacks the redox-active tyrosine Tyr(D), was engineered by substituting a phenylalanine for tyrosine 160 of the D2 protein. An aim of this work was to engineer a mutant for spectroscopy, in particular, for EPR, on the active enzyme. The Tyr(D)(*) EPR signal was monitored in whole cells (i) to control the expression level of the two genes (psbD(1) and psbD(2)) encoding D2 and (ii) to assess the success of the mutagenesis. Both psbD(1) and psbD(2) could be expressed, and recombination occurred between them. The D2-Y160F mutation was introduced into psbD(1) after psbD(2) was deleted and a His-tag was attached to the CP43 protein. The effects of the Y160F mutation were characterized in cells, thylakoids, and isolated PSII. The efficiency of enzyme function under the conditions tested was unaffected. The distribution and lifetime of the redox states (S(n)() states) of the enzyme cycle were modified, with more S(0) in the dark and no rapid decay phase of S(3). Although not previously reported, these effects were expected because Tyr(D)(*) is able to oxidize S(0) and Tyr(D) is able to reduce S(2) and S(3). Slight changes in the difference spectra in the visible and infrared recorded upon the formation and reduction of the chlorophyll cation P(680)(+) and kinetic measurements of P(680)(+) reduction indicated minor structural perturbations, perhaps in the hydrogen-bonding network linking Tyr(D) and P(680), rather than electrostatic changes associated with the loss of a charge from Tyr(D)(*)(H(+)). We show here that this fully active preparation can provide spectra from the Mn(4)CaO(4) complex and associated radical species uncontaminated by Tyr(D)(*). 相似文献
97.
Shibuya Y Hirasawa N Sakai T Togashi Y Muramatsu R Ishii K Yamashita M Takayanagi M Ohuchi K 《Life sciences》2004,75(4):435-446
The role of p44/42 mitogen-activated protein kinase (MAPK) in the expression of intercellular adhesion molecule-1 (ICAM-1) in NCI-H292 cells, a human bronchial epithelial cell line, was analyzed. Treatment with the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA) (16.2 nM) or interferon-gamma (IFN-gamma) (100 U/ml) induced phosphorylation of p44/42 MAPK. The MEK inhibitor U0126 (0.1 to 10 microM) enhanced the TPA-induced ICAM-1 expression but not the IFN-gamma-induced one. U0126 also enhanced the ICAM-1 expression induced by two other PKC activators teleocidin (22.5 nM) and aplysiatoxin (14.9 nM). Furthermore, PD98059 (0.5 to 50 microM), another MEK inhibitor, enhanced the TPA-induced ICAM-1 expression as well. The inhibitor of p38 MAPK SB203580 did not affect the TPA-induced ICAM-1 expression. BAY11-7082, an inhibitor of nuclear factor kappaB (NF-kappaB) activation, and MG132, a 26S proteasome inhibitor, reduced the TPA-induced ICAM-1 expression but not the IFN-gamma-induced one. TPA partially decreased the level of IkappaB-alpha and the reduction was further augmented by U0126 in a concentration-dependent manner. These findings suggested that, in NCI-H292 cells, p44/42 MAPK suppresses PKC activator-induced NF-kappaB activation, thus negatively regulating the PKC activator-induced ICAM-1 expression but not the IFN-gamma-induced one. 相似文献
98.
McCarl CA Khalil S Ma J Oh-hora M Yamashita M Roether J Kawasaki T Jairaman A Sasaki Y Prakriya M Feske S 《Journal of immunology (Baltimore, Md. : 1950)》2010,185(10):5845-5858
ORAI1 is the pore-forming subunit of the Ca(2+) release-activated Ca(2+) (CRAC) channel, which is responsible for store-operated Ca(2+) entry in lymphocytes. A role for ORAI1 in T cell function in vivo has been inferred from in vitro studies of T cells from human immunodeficient patients with mutations in ORAI1 and Orai1(-/-) mice, but a detailed analysis of T cell-mediated immune responses in vivo in mice lacking functional ORAI1 has been missing. We therefore generated Orai1 knock-in mice (Orai1(KI/KI)) expressing a nonfunctional ORAI1-R93W protein. Homozygosity for the equivalent ORAI1-R91W mutation abolishes CRAC channel function in human T cells resulting in severe immunodeficiency. Homozygous Orai1(KI/KI) mice die neonatally, but Orai1(KI/KI) fetal liver chimeric mice are viable and show normal lymphocyte development. T and B cells from Orai1(KI/KI) mice display severely impaired store-operated Ca(2+) entry and CRAC channel function resulting in a strongly reduced expression of several key cytokines including IL-2, IL-4, IL-17, IFN-γ, and TNF-α in CD4(+) and CD8(+) T cells. Cell-mediated immune responses in vivo that depend on Th1, Th2, and Th17 cell function were severely attenuated in ORAI1-deficient mice. Orai1(KI/KI) mice lacked detectable contact hypersensitivity responses and tolerated skin allografts significantly longer than wild-type mice. In addition, T cells from Orai1(KI/KI) mice failed to induce colitis in an adoptive transfer model of inflammatory bowel disease. These findings reaffirm the critical role of ORAI1 for T cell function and provide important insights into the in vivo functions of CRAC channels for T cell-mediated immunity. 相似文献
99.
Takumi Suzuki 《Journal of insect physiology》2010,56(6):673-677
Successful insect development is achieved via appropriate fluctuation of ecdysteroid levels. When an insect's ecdysteroid level is disrupted, physiological and developmental defects occur. In the pupa of the silkworm, Bombyx mori, the rectal sac is an essential organ that operates as a repository for degraded ecdysteroids, and it can be distended by administration of 20-hydroxyecdysone (20E). Our previous study showed that rectal sac distention appears 4 days after 20E administration. Hemolymph ecdysteroid levels, however, decrease to lower level during this period. Thus, the timing of the rectal sac distention does not match with that of ecdysteroid elevation. Here, we examine how 20E induces rectal sac distention. A ligature experiment and ecdysteroid quantification showed that continuous 20E stimulation induces rectal sac distention. Thorax tissue contributed to the continuous 20E stimulation needed to induce distention. Ecdysteroid released from the thorax tissue may be converted to 20E by ecdysone 20-hydroxylase to produce continuous 20E stimulation. Thus, the ecdysone metabolic pathway plays a critical role in rectal sac distention. 相似文献
100.
Miura Y Nishimura Y Katsuyama H Maeda M Hayashi H Dong M Hyodoh F Tomita M Matsuo Y Uesaka A Kuribayashi K Nakano T Kishimoto T Otsuki T 《Apoptosis : an international journal on programmed cell death》2006,11(10):1825-1835
To analyze the possibility that immunological alteration in asbestos-related diseases (ARDs) such as asbestosis (ASB) and
malignant mesothelioma (MM) may affect the progression of cancers, a human adult T cell leukemia virus-immortalized T cell
line (MT-2Org) was continuously exposed to 10 μg/ml of chrysotile-B (CB), an asbestos. After at least 8 months of exposure,
the rate of apoptosis in the cells became very low and the resultant subline was designated MT-2Rst. The MT-2Rst cells were
characterized by (i) enhanced expression of bcl-2, with regain of apoptosis-sensitivity by reduction of bcl-2 by siRNA, (ii) excess IL-10 secretion and expression, and (iii) activation of STAT3 that was inhibited by PP2, a specific
inhibitor of Src family kinases. These results suggested that the contact between cells and asbestos may affect the human
immune system and trigger a cascade of biological events such as activation of Src family kinases, enhancement of IL-10 expression,
STAT3 activation and Bcl-2 overexpression. This speculation was partially confirmed by the detection of elevated bcl-2 expression levels in CD4 + peripheral blood T cells from patients with MM compared with those from patients with ASB or healthy
donors. Further studies will be required to verify the role of T cells with enhanced bcl-2 expression in tumor progression induced by asbestos exposure. 相似文献