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   347篇
  免费   25篇
  国内免费   1篇
  2021年   3篇
  2019年   2篇
  2017年   4篇
  2016年   10篇
  2015年   11篇
  2014年   8篇
  2013年   17篇
  2012年   9篇
  2011年   22篇
  2010年   8篇
  2009年   7篇
  2008年   12篇
  2007年   17篇
  2006年   18篇
  2005年   7篇
  2004年   18篇
  2003年   12篇
  2002年   21篇
  2001年   13篇
  2000年   20篇
  1999年   12篇
  1998年   4篇
  1997年   3篇
  1996年   4篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1986年   7篇
  1985年   4篇
  1984年   4篇
  1983年   9篇
  1981年   7篇
  1979年   7篇
  1978年   6篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1974年   3篇
  1973年   3篇
  1972年   2篇
  1971年   3篇
  1970年   4篇
  1969年   6篇
  1967年   3篇
  1966年   2篇
  1963年   1篇
排序方式: 共有373条查询结果,搜索用时 62 毫秒
181.
Method for detection of pathogenic microorganisms in different microbiological assays (water, faeces, punctate etc.) has been developed. Device for preparation of samples and filtration of studied material through transparent tracking membranes with fixed size of pores and subsequent microscopy of filtrate was developed also as well as device for filtration of different liquids in closed cylinder under pressure. Method significantly increases informativeness and reliability of analyses, and decreases of their labor and financial costs.  相似文献   
182.
183.
Understanding the relationship between geographic range limits and physiological traits of vector species is under increasing demand to predict the potential effects of global warming, not only in terms of geographic distribution of vector species but also in terms of the risk of disease transmission. Like in many other insect species, the geographical distribution of Chagas’ disease vectors is affected by temperature. This study examines, for the first time, the relationship between the limits of geographic distribution and thermo‐tolerance of the most important vectors of Chagas disease, Triatoma infestans in southern South America and Rhodnius prolixus in northern South America and Central America, to test the climatic variability hypothesis (CVH). We applied species distribution modeling (SDM) using bioclimatic variables and identified the most important limiting factors of the habitat suitability. Then, we measured and compared: the critical thermal maximum (CTmax) and the upper lethal temperature (ULT) (measured by thermo‐limit respirometry), chilled coma recovery (i.e. the time to recovery from 4 h at 0°C) and the critical thermal minimum (CTmin). For both species the minimum temperature of the coldest month was the most important abiotic factor restricting their geographic distribution. By taking a correlative approach and testing predictions with thermal tolerance traits, it was possible to explain the southern limit distribution for both species in terms of physiological constraints. The greater temperature tolerance of T. infestans compared to R. prolixus supports the CVH.  相似文献   
184.
Functions of cell surface galectin-glycoprotein lattices   总被引:2,自引:0,他引:2  
Programmed remodeling of cell surface glycans by the sequential action of specific glycosyltransferases can control biological processes by generating or masking ligands for endogenous lectins. Galectins, a family of animal lectins with affinity for beta-galactosides, can form multivalent complexes with cell surface glycoconjugates and deliver a variety of intracellular signals to modulate cell activation, differentiation, and survival. Recent efforts involving genetic or biochemical manipulation of O-glycosylation and N-glycosylation pathways, as well as blockade of the synthesis of endogenous galectins, have illuminated essential roles for galectin-glycoprotein lattices in the control of biological processes including receptor turnover and endocytosis, host-pathogen interactions, and immune cell activation and homeostasis.  相似文献   
185.
The equilibria and kinetics of the interactions of proflavine (PR) and its platinum-containing derivative [PtCl(tmen)(2)HNC(13)H(7)(NHCH(2)CH(2))(2)](+) (PRPt) with double-stranded poly(A) have been investigated by spectrophotometry and Joule temperature-jump relaxation at ionic strength 0.1 M, 25 degrees C, and pH 5.2. Spectrophotometric measurements indicate that base-dye interactions are prevailing. T-jump experiments with polarized light showed that effects due to field-induced alignment could be neglected. Both of the investigated systems display two relaxation effects. The kinetic features of the reaction are discussed in terms of a two-step series mechanism in which a precursor complex DS(I) is formed in the fast step, which is then converted to a final complex in the slow step. The rate constants of the fast step are k(1) = (2.5 +/- 0.4) x 10(6) M(-1) s(-1), k(-1) = (2.4 +/- 0.1) x 10(3) s(-1) for poly(A)-PR and k(1) = (2.3 +/- 0.1) x 10(6) M(-1) s(-1), k(-1) = (1.6 +/- 0.2) x 10(3) s(-1) for poly(A)-PRPt. The rate constants for the slow step are k(2) = (4.5 +/- 0.5) x 10(2) s(-1), k(-2) = (1.7 +/- 0.1) x 10(2) s(-1) for poly(A)-PR and k(2) = 9.7 +/- 1.2 s(-1), k(-2) = 10.6 +/- 0.2 s(-1) for poly(A)-PRPt. Spectrophotometric measurements yield for the equilibrium constants and site size the values K = (4.5 +/- 0.1) x 10(3) M(-1), n = 1.3 +/- 0.5 for poly(A)-PR and K = (2.9 +/- 0.1) x 10(3) M(-1), n = 2.3 +/- 0.6 for poly(A)-PRPt. The values of k(1) are similar and lower than expected for diffusion-limited reactions. The values of k(-1) are similar as well. It is suggested that the formation of DS(I) involves only the proflavine residues in both systems. In contrast, the values of k(2) and k(-2) in poly(A)-PRPt are much lower than in poly(A)-PR. The results suggest that in the complex DS(II) of poly(A)-PRPt both proflavine and platinum residues are intercalated. In addition, a very slow process was detected and ascribed to the covalent binding of Pt(II) to the adenine.  相似文献   
186.
Chronic obstructive pulmonary disease (COPD) is a debilitating disease affecting patients in daily life, both physically and emotionally. Symptoms such as dyspnea and muscle fatigue, lead to exercise intolerance, which, together with behavioral issues, trigger physical inactivity, a key feature of COPD. Physical inactivity is associated with adverse clinical outcomes, including hospitalization and all-cause mortality. Increasing activity levels is crucial for effective management strategies and could lead to improved long-term outcomes. In this review we summarize objective and subjective instruments for evaluating physical activity and focus on interventions such as pulmonary rehabilitation or bronchodilators aimed at increasing activity levels. To date, only limited evidence exists to support the effectiveness of these interventions. We suggest that a multimodal approach comprising pulmonary rehabilitation, pharmacotherapy, and counselling programs aimed at addressing emotional and behavioural aspects of COPD may be an effective way to increase physical activity and improve health status in the long term.  相似文献   
187.
Platelets contribute to vessel formation through the release of angiogenesis-modulating factors stored in their α-granules. Galectins, a family of lectins that bind β-galactoside residues, are up-regulated in inflammatory and cancerous tissues, trigger platelet activation and mediate vascularization processes. Here we aimed to elucidate whether the release of platelet-derived proangiogenic molecules could represent an alternative mechanism through which galectins promote neovascularization. We show that different members of the galectin family can selectively regulate the release of angiogenic molecules by human platelets. Whereas Galectin (Gal)-1, -3, and -8 triggered vascular endothelial growth factor (VEGF) release, only Gal-8 induced endostatin secretion. Release of VEGF induced by Gal-8 was partially prevented by COX-1, PKC, p38 and Src kinases inhibitors, whereas Gal-1-induced VEGF secretion was inhibited by PKC and ERK blockade, and Gal-3 triggered VEGF release selectively through a PKC-dependent pathway. Regarding endostatin, Gal-8 failed to stimulate its release in the presence of PKC, Src and ERK inhibitors, whereas aspirin or p38 inhibitor had no effect on endostatin release. Despite VEGF or endostatin secretion, platelet releasates generated by stimulation with each galectin stimulated angiogenic responses in vitro including endothelial cell proliferation and tubulogenesis. The platelet angiogenic activity was independent of VEGF and was attributed to the concerted action of other proangiogenic molecules distinctly released by each galectin. Thus, secretion of platelet-derived angiogenic molecules may represent an alternative mechanism by which galectins promote angiogenic responses and its selective blockade may lead to the development of therapeutic strategies for angiogenesis-related diseases.  相似文献   
188.
Transferring Saccharomyces cerevisiae cells to water is known to extend their lifespan. However, it is unclear whether this lifespan extension is due to slowing the aging process or merely keeping old yeast alive. Here we show that in water-transferred yeast, the toxicity of polyQ proteins is decreased and the aging biomarker 47Q aggregates at a reduced rate and to a lesser extent. These beneficial effects of water-transfer could not be reproduced by diluting the growth medium and depended on de novo protein synthesis and proteasomes levels. Interestingly, we found that upon water-transfer 27 proteins are downregulated, 4 proteins are upregulated and 81 proteins change their intracellular localization, hinting at an active genetic program enabling the lifespan extension. Furthermore, the aging-related deterioration of the heat shock response (HSR), the unfolded protein response (UPR) and the endoplasmic reticulum-associated protein degradation (ERAD), was largely prevented in water-transferred yeast, as the activities of these proteostatic network pathways remained nearly as robust as in young yeast. The characteristics of young yeast that are actively maintained upon water-transfer indicate that the extended lifespan is the outcome of slowing the rate of the aging process.  相似文献   
189.
190.
The infusion of animal-derived antibodies has been known for some time to trigger the generation of antibodies directed at the foreign protein as well as adverse events including cytokine release syndrome. These immunological phenomena drove the development of humanized and fully human monoclonal antibodies. The ability to generate human(ized) antibodies has been both a blessing and a curse. While incremental gains in the clinical efficacy and safety for some agents have been realized, a positive effect has not been observed for all human(ized) antibodies. Many human(ized) antibodies trigger the development of anti-drug antibody responses and infusion reactions. The current belief that antibodies need to be human(ized) to have enhanced therapeutic utility may slow the development of novel animal-derived monoclonal antibody therapeutics for use in clinical indications. In the case of murine antibodies, greater than 20% induce tolerable/negligible immunogenicity, suggesting that in these cases humanization may not offer significant gains in therapeutic utility. Furthermore, humanization of some murine antibodies may reduce their clinical effectiveness. The available data suggest that the utility of human(ized) antibodies needs to be evaluated on a case-by-case basis, taking a cost-benefit approach, taking both biochemical characteristics and the targeted therapeutic indication into account.Key words: immunogenicity, human anti-mouse antibody, cytokine release syndrome  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