全文获取类型
收费全文 | 336篇 |
免费 | 8篇 |
国内免费 | 2篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 21篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 23篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有346条查询结果,搜索用时 31 毫秒
141.
142.
Induction of acid tolerance response (ATR) of exponential-phase Escherichia coli K-12 cells grown and adapted at different conditions was examined. The highest level of protection against pH 2.5 challenges was obtained after adaptation at pH 4.5-4.9 for 60 min. To study the genetic systems, which could be involved in the development of log-phase ATR, we investigated the acid response of E. coli acid resistance (AR) mutants. The activity of the glutamate-dependent system was observed in exponential cells grown at pH 7.0 and acid adapted at pH 4.5 in minimal medium. Importantly, log-phase cells exhibited significant AR when grown in minimal medium pH 7.0 and challenged at pH 2.5 for 2 h without adaptation. This AR required the glutamate-dependent AR system. Acid protection was largely dependent on RpoS in unadapted and adapted cells grown in minimal medium. RpoS-dependent oxidative, glutamate and arginine-dependent decarboxylase AR systems were not involved in triggering log-phase ATR in cells grown in rich medium. Cells adapted at pH 4.5 in rich medium showed a higher proton accumulation rate than unadapted cells as determined by proton flux assay. It is clear from our study that highly efficient mechanisms of protection are induced, operate and play the main role during log-phase ATR. 相似文献
143.
Recently, the development of selective androgen receptor modulators (SARMs) has been suggested as a means of combating the deleterious catabolic effects of hypogonadism, especially in skeletal muscle and bone, without inducing the undesirable androgenic effects (e.g., prostate enlargement and polycythemia) associated with testosterone administration. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone; 17β-TBOH), a synthetic analog of testosterone, may be capable of inducing SARM-like effects as it binds to androgen receptors (ARs) with approximately three times the affinity of testosterone and has been shown to augment skeletal muscle mass and bone growth and reduce adiposity in a variety of mammalian species. In addition to its direct actions through ARs, 17β-TBOH may also exert anabolic effects by altering the action of endogenous growth factors or inhibiting the action of glucocorticoids. Compared to testosterone, 17β-TBOH appears to induce less growth in androgen-sensitive organs which highly express the 5α reductase enzyme (e.g., prostate tissue and accessory sex organs). The reduced androgenic effects result from the fact that 17β-TBOH is metabolized to less potent androgens in vivo; while testosterone undergoes tissue-specific biotransformation to more potent steroids, dihydrotestosterone and 17β-estradiol, via the 5α-reductase and aromatase enzymes, respectively. Thus the metabolism of 17β-TBOH provides a basis for future research evaluating its safety and efficacy as a means of combating muscle and bone wasting conditions, obesity, and/or androgen insensitivity syndromes in humans, similar to that of other SARMs which are currently in development. 相似文献
144.
Mitra Ghasemi-Chaleshtari Seyed Hossein Kiaie Mahzad Irandoust Hadis Karami Mohsen Nabi Afjadi Sepideh Ghani Nasimeh Aghaei Vanda Mohammad Javad Ghaderi Sede Armin Ahmadi Ali Masjedi Hadi Hassannia Fatemeh Atyabi Mohammad Hojjat-Farsangi Afshin Namdar Ghasem Ghalamfarsa Farhad Jadidi-Niaragh 《Journal of cellular physiology》2020,235(12):10068-10080
Inhibitory immune checkpoint (ICP) molecules are important immunosuppressive factors in a tumor microenvironment (TME). They can robustly suppress T-cell-mediated antitumor immune responses leading to cancer progression. Among the checkpoint molecules, cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) is one of the critical inhibitors of anticancer T-cell responses. Besides, the expression of adenosine receptor (A2AR) on tumor-infiltrating T cells potently reduces their function. We hypothesized that concomitant silencing of these molecules in T cells might lead to enhanced antitumor responses. To examine this assumption, we purified T cells from the tumor, spleen, and local lymph nodes of CT26 colon cancer-bearing mice and suppressed the expression of A2AR and CTLA-4 using the small interfering RNA (siRNA)-loaded polyethylene glycol-chitosan-alginate (PCA) nanoparticles. The appropriate physicochemical properties of the produced nanoparticles (NPs; size of 72 nm, polydispersive index [PDI] < 0.2, and zeta potential of 11 mV) resulted in their high efficiency in transfection and suppression of target gene expression. Following the silencing of checkpoint molecules, various T-cell functions, including proliferation, apoptosis, cytokine secretion, differentiation, and cytotoxicity were analyzed, ex vivo. The results showed that the generated nanoparticles had optimal physicochemical characteristics and significantly suppressed the expression of target molecules in T cells. Moreover, a concomitant blockade of A2AR and CTLA-4 in T cells could synergistically enhance antitumor responses through the downregulation of PKA, SHP2, and PP2Aα signaling pathways. Therefore, this combination therapy can be considered as a novel promising anticancer therapeutic strategy, which should be further investigated in subsequent studies. 相似文献
145.
目的:探究藏药二十味沉香丸对卒中后PTSD模型大鼠行为和5-HT1AR的调节作用。方法:将48只大鼠随机分为假手术组、模型组、二十味沉香丸组、帕罗西汀组。每组各12只。造模后未达到观察时点死亡的大鼠排除本研究,筛选出符合条件的大鼠并通过随机抽样原则补齐动物。造模后每天分别给予相应的药物或生理盐水进行灌胃,灌胃2周后采用旷场实验检测各组剩余大鼠行为学变化。每组各取6只,采用实时荧光定量PCR和Western blot法分别检测海马组织中5-HT1AR基因和蛋白水平的变化。结果:与假手术组相比较,模型组运动总距离(P0.01)、单次最大运动距离(P0.05)、穿格次数(P0.01)、直立次数(P0.01)、直立时间(P0.01)、修饰时间(P0.01)、修饰次数(P0.05)减少差异有统计学意义,5-HT1AR基因(P0.05)及蛋白表达水平下降;与模型组相比较,二十味沉香丸组运动总距离(P0.05)、穿格次数(P0.05)、直立时间(P0.05)、直立次数(P0.01)增加差异具有统计学意义,且5-HT1AR的基因(P0.05)及蛋白水平表达升高;与模型组相比较,帕罗西汀组穿格次数(P0.05)、运动总距离(P0.05)、直立时间(P0.05)增加差异具有统计学意义,5-HT1AR的基因(P0.01)及蛋白表达水平升高。结论:本实验成功复制了卒中后PTSD模型,所选取的中药二十味沉香丸能在一定程度上改善卒中后PTSD模型大鼠的焦虑样行为,其效用与西药帕罗西汀类似,且作用机制可能与调节5-HT1AR有关。 相似文献
146.
Yoji Kyotani Hiroyo Ota Asako Itaya-Hironaka Akiyo Yamauchi Sumiyo Sakuramoto-Tsuchida Jing Zhao Kentaro Ozawa Kosuke Nagayama Satoyasu Ito Shin Takasawa Hiroshi Kimura Masayuki Uno Masanori Yoshizumi 《Experimental cell research》2013
Obstructive sleep apnea is characterized by intermittent hypoxia (IH), and associated with cardiovascular diseases, such as stroke and heart failure. These cardiovascular diseases have a relation to atherosclerosis marked by the proliferation of vascular smooth muscle cells (VSMCs). In this study, we investigated the influence of IH on cultured rat aortic smooth muscle cell (RASMC). The proliferation of RASMC was significantly increased by IH without changing the level of apoptosis. In order to see what induces RASMC proliferation, we investigated the influence of normoxia (N)-, IH- and sustained hypoxia (SH)-treated cell conditioned media on RASMC proliferation. IH-treated cell conditioned medium significantly increased RASMC proliferation compared with N-treated cell conditioned medium, but SH-treated cell conditioned medium did not. We next investigated the epidermal growth factor (EGF) family as autocrine growth factors. Among the EGF family, we found significant increases in mRNAs for epiregulin (ER), amphiregulin (AR) and neuregulin-1 (NRG1) in IH-treated cells and mature ER in IH-treated cell conditioned medium. We next investigated the changes in erbB family receptors that are receptors for ER, AR and NRG1, and found that erbB2 receptor mRNA and protein expressions were increased by IH, but not by SH. Phosphorylation of erbB2 receptor at Tyr-1248 that mediates intracellular signaling for several physiological effects including cell proliferation was increased by IH, but not by SH. In addition, inhibitor for erbB2 receptor suppressed IH-induced cell proliferation. These results provide the first demonstration that IH induces VSMC proliferation, and suggest that EGF family, such as ER, AR and NRG1, and erbB2 receptor could be involved in the IH-induced VSMC proliferation. 相似文献
147.
Wu Lian Mingyi Wu Ning Huang Na Gao Chuang Xiao Zi Li Zhigang Zhang Yongtang Zheng Wenlie Peng Jinhua Zhao 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Fucosylated glycosaminoglycan (FG) is a novel glycosaminoglycan with a chondroitin sulfate-like backbone and fucose sulfate branches. The aim of this study is to investigate the mechanism and structure–activity relationships (SAR) of FG for combating HIV-1 infection.Methods
Anti-HIV activities of FGs were assessed by a cytopathic effect assay and an HIV-1 p24 detection assay. The biomolecule interactions were explored via biolayer interferometry technology. The SAR was established by comparing its anti-HIV-1 activities, conserved CD4 induced (CD4i) epitope-dependent interactions and anticoagulant activities.Results
FG efficiently and selectively inhibited the X4- and R5X4-tropic HIV-1 infections in C8166 cells with little cytotoxicity against C8166 cells and PBMCs. Our data indicated that FG bound to gp120 with nanomolar affinity and may interact with CD4i of gp120. Additionally, the CD4i binding affinity of FG was higher than that of dextran sulfate. SAR studies suggested that the unique sulfated fucose branches account for the anti-HIV-1 activity. The molecular size and present carboxyl groups of FG may also play important roles in various activities. Notably, several FG derivatives showed higher anti-HIV-1 activities and much lower anticoagulant activities than those of heparin.Conclusions
FG exhibits strong activity against X4- and R5X4-tropic HIV-1 infections. The mechanism may be related to targeting CD4i of gp120, which results in inhibition of HIV-1 entry. The carboxyl group substituted derivatives of FG (8.5–12.8 kDa), might display high anti-HIV-1 activity and low anticoagulant activity.General significance
Our data supports further the investigation of FG derivatives as novel HIV-1 entry inhibitors targeting CD4i. 相似文献148.
Prostate cancer (PCa) is the most common cancer in men in developed countries. Epidemiological studies have associated high blood-cholesterol levels with an increased risk of PCa, whilst cholesterol-lowering drugs (statins) reduce the risk of advanced PCa. Furthermore, normal prostate epithelial cells have an abnormally high cholesterol content, with cholesterol levels increasing further during progression to PCa. In this review, we explore why and how this occurs. 相似文献
149.
Mammalian fertilization is a complex process that involves gamete recognition, penetration, and fusion. Biochemical studies that identified the role of acrosome components during sperm–ova interaction especially the zona pellucida (ZP) provided major advances in sperm cell biology. Acrosin (a typical serine protease) functions during fertilization in several significant ways which include: a) activation of acrosome components, b) secondary binding with the ZP, and c) hydrolysis of the ZP. However, studies using knockout (KO) acrosin-deficient mice cast doubt on the traditional role of acrosin in fertilization. The KO acrosin-deficient mice exhibit normal fecundity except for delayed fertilization. Despite the doubt cast on the traditional role of acrosin by the KO acrosin-deficient mouse studies, acrosin still remains a major protease involved in multiple processes of fertilization. In this review, we assess the functional profile of acrosin and briefly summarize recent findings on proteases involved in fertilization. We propose a refined scheme for the functional role of acrosin in fertilization. We particularly emphasize the role of acrosin in acrosome exocytosis and activation of other acrosome components based on advanced technology like structural X-ray analysis. 相似文献
150.
Chiara Di Marco Anna Lavinia Bulotta Concetta Varetti Laura Dosa Angela Michelucci Fulvia Baldinotti Daniela Meucci Cinzia Castagnini Caterina Lo Rizzo Giovanni Di Maggio Paolo Simi Francesca Mari Silvano Bertelloni Alessandra Renieri Mario Messina 《Gene》2013
We report on seven Iraqi patients with 46,XY karyotype and ambiguous genitalia characterized by perineo-scrotal hypospadias, bifid scrotum, clitoris like phallus, palpable testes in inguinal canal and pseudovagina. Patients were raised five as females and two as males. They are all unrelated with the exception of two couples of brothers. The diagnosis of 5-α-reductase-2 deficiency syndrome was first hypothesized on clinical grounds and then confirmed by molecular analysis. Direct sequencing analysis of the SRD5A2 gene revealed in five patients a novel homozygous frame-shift mutation (c.453delC) and in two related patients a previous reported missense mutation. The presence of the same mutation in unrelated patients of the same population suggests a possible founder effect. This report brings the 5-α-reductase-2 deficiency syndrome to the attention of clinical geneticists and child surgeons and discusses the appropriate clinical and surgical strategies for treating these patients. 相似文献