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   210篇
  免费   9篇
  219篇
  2023年   1篇
  2022年   6篇
  2021年   3篇
  2020年   4篇
  2019年   6篇
  2018年   1篇
  2017年   4篇
  2016年   8篇
  2015年   11篇
  2014年   8篇
  2013年   17篇
  2012年   13篇
  2011年   18篇
  2010年   13篇
  2009年   7篇
  2008年   9篇
  2007年   15篇
  2006年   12篇
  2005年   15篇
  2004年   5篇
  2003年   6篇
  2002年   7篇
  2001年   4篇
  2000年   1篇
  1999年   3篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1987年   3篇
  1986年   2篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
  1976年   2篇
  1973年   1篇
  1970年   1篇
  1966年   1篇
排序方式: 共有219条查询结果,搜索用时 46 毫秒
31.
A series of new 1,8-naphthyridine and quinoline derivatives were synthesized and evaluated for their cannabinoid receptor affinity. In particular, compounds 2, 5, 11, and 13 showed a high CB(2) affinity and CB(2) versus CB(1) selectivity, in agreement with molecular modeling studies. Furthermore, compound 2 also exhibited in vivo antinociceptive effects.  相似文献   
32.
33.
Despite interest in neurohormonal activation as a determinant of prognosis in chronic heart failure (CHF) and as a target for pharmacological treatments, data are lacking on the time-related effects of electrical cardiac resynchronization therapy (CRT) on a broad spectrum of neurohormones and cytokines. The aim of this study was to assess time-courses and extents of changes within the neurohormonal profile of CHF patients treated with CRT. We performed a prospective follow-up study in 32 patients with NYHA class III-IV CHF to investigate the effects of CRT on a broad panel of neurohormones proposed for characterization of CHF patients. Levels of atrial and brain natriuretic peptides (ANP, BNP), epinephrine, norepinephrine, aldosterone, plasma renin activity, IL-6, TNF, soluble receptors sTNFR1 and 2, and chromogranin A were assessed before implantation and after 3 months of CRT; when feasible, measurements were also performed at 1 week, 1 month and 12 months (clinical evaluation, echocardiography and ECG were also performed at each time-point). The results showed that at 3 months improvement in NYHA class and echographically assessed left ventricular (LV) reverse structural remodeling were accompanied by significant reductions versus baseline in ANP and BNP, but not in other neurohormones. Moreover a baseline ANP concentration < or = 150 pg/ml was a good predictor of response to CRT in terms of NYHA class reduction and reverse LV remodeling. In conclusion 3 months of CRT significantly reduce natriuretic peptides concentrations, while values of other neurohormones and inflammatory cytokines are relatively unvaried. A baseline ANP concentration < or = 150 pg/ml might be a clinically useful predictor of medium-term response to CRT.  相似文献   
34.
Single-cell experiments represent the next frontier for biochemical and gene expression research. Although bulk-scale methods averaging populations of cells have been traditionally used to investigate cellular behavior, they mask individual cell features and can lead to misleading or insufficient biological results. We report on a single-cell electroporation microarray enabling the transfection of pre-selected individual cells at different sites within the same culture (space-resolved), at arbitrarily chosen time points and even sequentially to the same cells (time-resolved). Delivery of impermeant molecules by single-cell electroporation was first proven to be finely tunable by acting on the electroporation protocol and then optimized for transfection of nucleic acids into Chinese Hamster Ovary (CHO-K1) cells. We focused on DNA oligonucleotides (ODNs), short interfering RNAs (siRNAs), and DNA plasmid vectors, thus providing a versatile and easy-to-use platform for time-resolved gene expression experiments in single mammalian cells.  相似文献   
35.
Autophagy is a regulated process for the degradation of cellular components that has been well conserved in eukaryotic cells. The discovery of autophagy-regulating proteins in yeast has been important in understanding this process. Although many parallels exist between fungi and mammals in the regulation and execution of autophagy, there are some important differences. The preautophagosomal structure found in yeast has not been identified in mammals, and it seems that there may be multiple origins for autophagosomes, including endoplasmic reticulum, plasma membrane and mitochondrial outer membrane. The maturation of the phagophore is largely dependent on 5’-AMP activated protein kinase and other factors that lead to the dephosphorylation of mammalian target of rapamycin. Once the process is initiated, the mammalian phagophore elongates and matures into an autophagosome by processes that are similar to those in yeast. Cargo selection is dependent on the ubiquitin conjugation of protein aggregates and organelles and recognition of these conjugates by autophagosomal receptors. Lysosomal degradation of cargo produces metabolites that can be recycled during stress. Autophagy is an impor-tant cellular safeguard during starvation in all eukaryotes; however, it may have more complicated, tissue specific roles in mammals. With certain exceptions, autophagy seems to be cytoprotective, and defects in the process have been associated with human disease.  相似文献   
36.
Research interest in the study of cytochromes P450 has recently been shifting to the characterization of "constitutively" expressed isozymes from that of the inducible forms. Several "constitutive" cytochrome P450 isozymes have been purified from rat liver including five immunochemically related proteins designated cytochromes P450f, P450g, P450h, P450i, and P450k. These hemoproteins have been identified as distinct isozymes on the basis of spectral, electrophoretic, and catalytic properties and NH2-terminal sequence analysis. Purification and immunoquantitation studies have indicated that these isozymes are expressed in a developmental as well as sex-related manner, and are relatively refractory to induction by xenobiotics. Cytochromes P450h and P450g are male-specific proteins, cytochrome P450i is a female-specific isozyme, while cytochromes P450f and P450k are present in both male and female adult rats. In addition, the expression of cytochrome P450g was shown to segregate into two phenotypes in outbred rats. Genetic studies utilizing inbred strains have indicated that the gene responsible for inheritance of high levels of cytochrome P450g is autosomal. Although considerable progress has been made in understanding the role of gonadal hormones and growth hormone in the hepatic regulation of cytochromes P450g, P450h, and P450i in particular, the physiological significance of the "constitutive" isozymes in the liver remains largely unresolved.  相似文献   
37.
In the context of agent based modeling and network theory, we focus on the problem of recovering behavior-related choice information from origin-destination type data, a topic also known under the name of network tomography. As a basis for predicting agents'' choices we emphasize the connection between adaptive intelligent behavior, causal entropy maximization, and self-organized behavior in an open dynamic system. We cast this problem in the form of binary and weighted networks and suggest information theoretic entropy-driven methods to recover estimates of the unknown behavioral flow parameters. Our objective is to recover the unknown behavioral values across the ensemble analytically, without explicitly sampling the configuration space. In order to do so, we consider the Cressie-Read family of entropic functionals, enlarging the set of estimators commonly employed to make optimal use of the available information. More specifically, we explicitly work out two cases of particular interest: Shannon functional and the likelihood functional. We then employ them for the analysis of both univariate and bivariate data sets, comparing their accuracy in reproducing the observed trends.  相似文献   
38.
In this study proteins extracted from prepupae of Hermetia illucens, also known as black soldier fly, are investigated as promising base for a new type of bioplastics for agricultural purposes. Design of experiments techniques are employed to perform a rational study on the effects of different combination of glycerol as plasticizer, citric acid as cross-linking agent and distilled water as solvent on the capability of proteins to form a free-standing film through casting technique, keeping as fixed the quantity of proteins. Glycerol shows interesting properties as plasticizer contributing to the formation of homogenous and free-standing film. Moreover, mechanical and thermal characterizations are performed to estimate the effect of increasing amounts of proteins on the final properties and thickness of the specimens. Proteins derived from H. illucens can be successfully employed as base for bioplastics to be employed for agricultural purposes.  相似文献   
39.
Despite their wide distribution and ecological importance, almost no information is available about the role of freshwater crayfish as basibiont for epizoic algae. Moreover, studies on epizoic freshwater diatoms have been largely neglected. In this study, we examined the occurrence of diatoms on two sympatric species, the native white-clawed crayfish Austropotamobius pallipes and the non-indigenous signal crayfish Pacifastacus leniusculus, coexisting in the same stream in NW Italy. We detected that signal crayfish showed a far more productive epizoic algal community than white-clawed crayfish. Microscopical analysis confirmed that non-indigenous crayfish hosted rich and diversified diatom communities while virtually no diatom was found on the native. After analyzing different hypotheses, we suggested that this significant difference can be the result of diverse crayfish behavioral habits. Because of the lack of studies investigating epibiontic diatoms on freshwater crayfish, we performed a detailed characterization on the epizoic flora, including comparisons with natural epilithic communities. The exponential diffusion of non-indigenous freshwater crayfish is a subject of greatest interest. Increasing our knowledge on their role as basibionts is definitely necessary to better understand their ecological role, also considering their influence on primary producer community and their role as vectors of algal species of concern, such as Didymosphenia geminata.  相似文献   
40.
We describe the characterization of an interstitial duplication of 12p, dup(12)(p11.21p13.31), by array-CGH and FISH in a patient with mental retardation and dysmorphic features. The sequence analysis of the breakpoints revealed the presence of homologous low copy repeats (LCRs) flanking the duplication region, thus suggesting that they have mediated the rearrangement. Pip-maker analysis showed that a third cluster of homologous LCRs lie distally to the two mediating the 12p duplication. We hypothesize that this duplication might be a new recurrent rearrangement and that, thanks to the different orientations of the homologous regions lying within each cluster, the three clusters are responsible for at least some of the several 12p aneuploidies reported in the literature such as direct and inverted duplications, deletions and supernumerary analphoid chromosomes. Moreover, we excluded that polymorphic inversions between these three clusters are present in the normal population.Manuela De Gregori, Tiziano Pramparo contributed equally to this paper.  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