首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   202篇
  免费   16篇
  国内免费   1篇
  2016年   3篇
  2015年   4篇
  2014年   9篇
  2013年   8篇
  2012年   4篇
  2011年   4篇
  2009年   4篇
  2008年   8篇
  2007年   11篇
  2006年   6篇
  2005年   13篇
  2004年   7篇
  2003年   6篇
  2002年   4篇
  2001年   3篇
  2000年   6篇
  1999年   6篇
  1997年   2篇
  1996年   2篇
  1995年   3篇
  1993年   4篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   5篇
  1985年   5篇
  1984年   3篇
  1983年   4篇
  1980年   6篇
  1979年   4篇
  1978年   6篇
  1977年   2篇
  1976年   4篇
  1975年   2篇
  1969年   2篇
  1964年   2篇
  1961年   2篇
  1960年   4篇
  1958年   3篇
  1957年   3篇
  1955年   2篇
  1954年   3篇
  1935年   1篇
  1932年   1篇
  1928年   1篇
  1926年   1篇
  1911年   1篇
排序方式: 共有219条查询结果,搜索用时 46 毫秒
51.
McLeod RL  Mingo GG  Kreutner W  Hey JA 《Life sciences》2005,76(16):1787-1794
The pharmacological consequences of combining a histamine H1 receptor antagonist with a H3 antagonist on cutaneous microvascular permeability due to intradermal (i.d.) injections of compound 48/80, a mast cell liberator of histamine, was studied in the anesthetized guinea pig. Compound 48/80 (0.0003, 0.001, 0.003 and 0.01%) induced permeability responses were attenuated, as determined by Evans blue extravasation, in animals pretreated with the H1 antagonist, chlorpheniramine (CTM; 1.0 mg/kg, i.v.) by 17 +/- 4, 31 +/- 4, 32 +/- 4 and 37 +/- 4%, respectively. Combination treatment with an H1 and H3 antagonist displayed greater inhibitory efficacy against the effects elicited by compound 48/80. Specifically, combined treatment with CTM (1.0 mg/kg, i.v.) and the H3 antagonist, thioperamide (THIO 1.0 mg/kg,i.v.) inhibited the skin responses of i.d. compound 48/80 (0.0003, 0.001, 0.003 and 0.01%) by 36 +/- 4, 45 +/- 4, 49 +/- 4 and 54 +/- 4%. A second H3 antagonist, clobenpropit (CLOB; 0.3 mg/kg, i.v.) plus CTM (1.0 mg/kg, i.v.) also inhibited Evans blue extravasation. Treatment with THIO (1.0 mg/kg, i.v.) and CLOB (0.3 mg/kg, i.v.) administered alone had no effect on compound 48/80-induced skin responses. We conclude that combination administration of a H1 and a H3 histamine receptor antagonist produces greater inhibitory effect on cutaneous microvascular permeability produced by released mast cell-derived histamine than either a H1 or H3 antagonist administered separately. In addition, the antiallergy activity of combining a H3 antihistamine with a H3 antagonist activity might provide a novel approach for the treatment of allergic skin diseases such as urticaria.  相似文献   
52.
The role of the protein kinase C (PKC) family of serine/threonine kinases in cellular differentiation, proliferation, apoptosis, and other responses makes them attractive therapeutic targets. The activation of PKCs by ligands in vivo varies depending upon cell type; therefore, methods are needed to screen the potency of PKCs in this context. Here we describe a genetically encoded chimera of native PKCdelta fused to yellow- and cyan-shifted green fluorescent protein, which can be expressed in mammalian cells. This chimeric protein kinase, CY-PKCdelta, retains native or near-native activity in the several biological and biochemical parameters that we tested. Binding assays showed that CY-PKCdelta and native human PKCdelta have similar binding affinity for phorbol 12,13-dibutyrate. Analysis of translocation by Western blotting and confocal microscopy showed that CY-PKCdelta translocates from the cytosol to the membrane upon treatment with ligand, that the translocation has similar dose dependence as that of endogenous PKCdelta, and that the pattern of translocation is indistinguishable from that of the green fluorescent protein-PKCdelta fusion well characterized from earlier studies. Treatment with phorbol ester of cells expressing CY-PKCdelta resulted in a dose-dependent increase in FRET that could be visualized in situ by confocal microscopy or measured fluorometrically. By using this construct, we were able to measure the kinetics and potencies of 12 known PKC ligands, with respect to CY-PKCdelta, in the intact cell. The CY-PKCdelta chimera and the in vivo assays described here therefore show potential for high throughput screening of prospective PKCdelta ligands within the context of cell type.  相似文献   
53.
54.
55.
In order to obtain a systems‐level understanding of a complex biological system, detailed proteome information is essential. Despite great progress in proteomics technologies, thorough interrogation of the proteome from quantity‐limited biological samples is hampered by inefficiencies during processing. To address these challenges, here we introduce a novel protocol using paramagnetic beads, termed Single‐Pot Solid‐Phase‐enhanced Sample Preparation (SP3). SP3 provides a rapid and unbiased means of proteomic sample preparation in a single tube that facilitates ultrasensitive analysis by outperforming existing protocols in terms of efficiency, scalability, speed, throughput, and flexibility. To illustrate these benefits, characterization of 1,000 HeLa cells and single Drosophila embryos is used to establish that SP3 provides an enhanced platform for profiling proteomes derived from sub‐microgram amounts of material. These data present a first view of developmental stage‐specific proteome dynamics in Drosophila at a single‐embryo resolution, permitting characterization of inter‐individual expression variation. Together, the findings of this work position SP3 as a superior protocol that facilitates exciting new directions in multiple areas of proteomics ranging from developmental biology to clinical applications.  相似文献   
56.
Serotonin (5-HT) and leptin play important roles in the modulation of energy balance. Here we investigated mechanisms by which leptin might interact with CNS 5-HT pathways to influence appetite. Although some leptin receptor (LepRb) neurons lie close to 5-HT neurons in the dorsal raphe (DR), 5-HT neurons do not express LepRb. Indeed, while leptin hyperpolarizes some non-5-HT DR neurons, leptin does not alter the activity of DR 5-HT neurons. Furthermore, 5-HT depletion does not impair the anorectic effects of leptin. The serotonin transporter-cre allele (Sert(cre)) is expressed in 5-HT (and developmentally in some non-5-HT) neurons. While Sert(cre) promotes LepRb excision in a few LepRb neurons in the hypothalamus, it is not active in DR LepRb neurons, and neuron-specific Sert(cre)-mediated LepRb inactivation in mice does not alter body weight or adiposity. Thus, leptin does not directly influence 5-HT neurons and does not meaningfully modulate important appetite-related determinants via 5-HT neuron function.  相似文献   
57.

Background

Population movements following disasters can cause important increases in morbidity and mortality. Without knowledge of the locations of affected people, relief assistance is compromised. No rapid and accurate method exists to track population movements after disasters. We used position data of subscriber identity module (SIM) cards from the largest mobile phone company in Haiti (Digicel) to estimate the magnitude and trends of population movements following the Haiti 2010 earthquake and cholera outbreak.

Methods and Findings

Geographic positions of SIM cards were determined by the location of the mobile phone tower through which each SIM card connects when calling. We followed daily positions of SIM cards 42 days before the earthquake and 158 days after. To exclude inactivated SIM cards, we included only the 1.9 million SIM cards that made at least one call both pre-earthquake and during the last month of study. In Port-au-Prince there were 3.2 persons per included SIM card. We used this ratio to extrapolate from the number of moving SIM cards to the number of moving persons. Cholera outbreak analyses covered 8 days and tracked 138,560 SIM cards.An estimated 630,000 persons (197,484 Digicel SIM cards), present in Port-au-Prince on the day of the earthquake, had left 19 days post-earthquake. Estimated net outflow of people (outflow minus inflow) corresponded to 20% of the Port-au-Prince pre-earthquake population. Geographic distribution of population movements from Port-au-Prince corresponded well with results from a large retrospective, population-based UN survey. To demonstrate feasibility of rapid estimates and to identify areas at potentially increased risk of outbreaks, we produced reports on SIM card movements from a cholera outbreak area at its immediate onset and within 12 hours of receiving data.

Conclusions

Results suggest that estimates of population movements during disasters and outbreaks can be delivered rapidly and with potentially high validity in areas with high mobile phone use. Please see later in the article for the Editors'' Summary  相似文献   
58.
ADAMTS13 is a secreted zinc metalloprotease expressed by various cell types. Here, we investigate its cellular pathway in endogenously expressing liver cell lines and after transient transfection with ADAMTS13. Besides compartmentalizations of the cellular secretory system, we detected an appreciable level of endogenous ADAMTS13 within the nucleus. A positively charged amino acid cluster (R-Q-R-Q-R-Q-R-R) present in the ADAMTS13 propeptide may act as a nuclear localization signal (NLS). Fusing this NLS-containing region to eGFP greatly potentiated its nuclear localization. Bioinformatics analysis suggests that the ADAMTS13 CUB-2 domain has a double-stranded beta helix (DSBH) structural architecture characteristic of various protein-protein interaction modules like nucleoplasmins, class I collagenase, tumor necrosis factor ligand superfamily, supernatant protein factor (SPF) and the B1 domain of neuropilin-2. Based on this contextual evidence and that largely conserved polar residues could be mapped on to a template CUB domain homolog, we hypothesize that a region in the ADAMTS13 CUB-2 domain with conserved polar residues might be involved in protein-protein interaction within the nucleus.  相似文献   
59.
A series of antiprogestins have been synthesized by partially fluorinating the steroid molecule in positions relevant for receptor binding. By introducing fluorine at the exo-methylene of the 17 spirofuran ring, we obtained partial agonists (mesoprogestins) with significant applications for antiproliferative and antiovulatory treatment strategies in gynecological therapy such as uterine fibroids, endometriosis and heavy menstrual bleeding. Compared to the standard drug RU486, our synthesized compounds exhibited considerable dissociation between antiprogestational and antiglucocorticoid PR receptors. Furthermore, our studies have shown that pure antiprogestins can be generated by partially fluorinating the 17 propenyl and propynl group or by substituting the 4′ acetyl phenyl group in the 11 position using trifluromethyl group.  相似文献   
60.
In order to investigate heritability and gene action for yellow rust resistance in wheat, a resistance yellow rust cultivar Aflak was crossed to susceptible cultivar Avocet‘s’. Parents, F1, F2 and F3 generations were cultured according to randomised complete block design with two replications in the research station of Gharakhil, Iran. Parents and other generations were inoculated with 70E0A+ race. Traits including severity and infection type were recorded and then coefficient of infection was calculated. For this trait, generations mean and variance analysis were performed and results showed that there were significant differences among generations for coefficient of infection. Results showed that in addition to additive and dominance effects, at least one kind of epistasis interaction (additive × additive) control this trait. Although additive and dominance effects control this trait, but with attention to generations variance analysis, the results showed that additive variance had important role to control this trait.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号