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   677篇
  免费   29篇
  国内免费   4篇
  2024年   1篇
  2023年   2篇
  2022年   1篇
  2021年   18篇
  2020年   8篇
  2019年   10篇
  2018年   13篇
  2017年   14篇
  2016年   24篇
  2015年   45篇
  2014年   40篇
  2013年   40篇
  2012年   62篇
  2011年   50篇
  2010年   34篇
  2009年   35篇
  2008年   45篇
  2007年   46篇
  2006年   33篇
  2005年   42篇
  2004年   31篇
  2003年   27篇
  2002年   26篇
  2001年   11篇
  2000年   16篇
  1999年   11篇
  1998年   2篇
  1997年   5篇
  1996年   1篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   2篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1986年   2篇
  1984年   1篇
  1961年   1篇
排序方式: 共有710条查询结果,搜索用时 15 毫秒
701.
702.
703.
GHK (Gly‐His‐Lys), a natural peptide found in human skin and plasma, has been widely used in the cosmeceutical and pharmaceutical fields. The hydrophilic GHK and GHK‐Cu are limited in their abilities to penetrate deeply into skin; because of this, various strategies for their skin delivery have been developed. In this investigation, Arg4 was conjugated with GHK to get heptapeptide, GHK‐R4, and then in vitro antiwrinkle activity and transdermal delivery were compared between GHK and GHK‐R4. Notably, Arg4 conjugation accelerated the cellular penetration of GHK both in vitro and in vivo. Furthermore, higher in vitro antiwrinkle activity and collagen biosynthesis was obtained with GHK‐R4 at much lower doses than with control R4‐free GHK. The enhanced activity and delivery of GHK‐R4 might be due to the cell penetrating ability and matrix metalloproteinase (MMP) inhibitory activity of R4 itself.  相似文献   
704.
705.
706.
This study developed an artificial neural network (ANN) to estimate the growth of microorganisms during a fermentation process. The ANN relies solely on the cumulative consumption of alkali and the buffer capacity, which were measured on-line from the on/off control signal and pH values through automatic pH control. The two input variables were monitored on-line from a series of different batch cultivations and used to train the ANN to estimate biomass. The ANN was refined by optimizing the network structure and by adopting various algorithms for its training. The software estimator successfully generated growth profiles that showed good agreement with the measured biomass of separate batch cultures carried out between at 25 and 35_C.  相似文献   
707.
Integration of working environment into life cycle assessment framework   总被引:1,自引:0,他引:1  
Background, aim, and scope  Life cycle assessment (LCA) has been considered one of the tools for supporting decision-making related to the environmental aspects of a product system. It has mainly been used to evaluate the potential impacts associated with relevant inputs and outputs to/from a given product system throughout its life cycle. In most cases, LCA has not considered the impacts on the internal environment, i.e. working environment, but only the external environment. Recently, it has been recognized that the consideration of the impacts on the working environment as well as on the external environment, is needed in order to assess all aspects of the effects on human well-being. To this end, this study has developed a total environmental assessment methodology which enables one to integrate both the working environment and the external environment into the conventional LCA framework. Materials and methods  In general, the characteristics of the impacts on the external environment are different from those on the working environment. In order to properly integrate the two types into total environmental impacts, it is necessary to define identical system boundaries and select impact category indicators at the same level. In order to define the identical system boundary and reduce the uncertainties of LCI results, the hybrid IOA (input–output analysis) method, which integrates the advantages between conventional LCI method and IOA method, is introduced to collect input and output data throughout the entire life cycle of a given product. For the impact category indicators at the endpoint level, LWD (Lost Work Days) is employed to evaluate the damage to human health and safety in the working environment, while DALY (disability-adjusted life years) and PAF (Potentially Affected Fraction) are selected to evaluate the damage to human health and eco-system quality in the external environment, respectively. Results and discussion  The environmental intervention factors (EIFs) are developed not only for the data categories of resource use, air emissions, and water emissions, but also for occupational health and safety to complete a life cycle inventory table. For the development of the EIFs on occupational health and safety, in particular, the number of workers affected by i hazardous items and the number of workers affected at the i magnitude of disability are collected. For the characterization of the impact categories in the working environment, such as occupational health and safety, the exposure factors, effect factors, and damage factors are developed to calculate the LWD of each category. For normalization, the normalization reference is defined as the total LWD divided by the total number of workers. A case study is presented to illustrate the applicability of the proposed method for the integration of the working environment into the conventional LCA framework. Conclusions  This study is intended to develop a methodology which enables one to integrate the working environmental module into the conventional LCA framework. The hybrid IOA method is utilized to extend the system boundary of both the working environment module and the external environment module to the entire life cycle of a product system. In this study, characterization models and category indicators for occupational health and safety are proposed, respectively, while the methodology of Eco-indicator 99 is used for the external environment. In addition to aid further understanding on the results of this method, this study introduced and developed the category indicators such as DALY, and LWD, which can be expressed as a function of time, and introduced PAF, which can be expressed as a probability. Recommendations and perspectives  The consideration of the impacts not only on the external environment, but also on the working environment, is very important, because the best solution for the external environment may not necessarily be the best solution for the working environment. It is expected that the integration of occupational health and safety matters into the conventional LCA framework can bring many benefits to individuals, as well as industrial companies, by avoiding duplicated measures and false optimization.  相似文献   
708.
709.
The complex interaction between obesity, Western-style diets, and cardiovascular disease is of increasing interest, with a growing number of children being born to obese parents with poor lifestyle choices. These offspring have themselves an increased susceptibility to obesity and subsequent cardiovascular disease in adult life, which may be ‘programmed’ by their intrauterine environment. Cardiac microRNAs (miRNAs) are affected by multiple disease states, and have also been shown to be capable of exerting a hormone-like control on whole body metabolism. Here we sought to determine the effect of prenatal exposure to maternal obesity and/or postnatal exposure to a Western diet on miRNA expression in the heart. Unbiased small RNA sequencing was carried out on cardiac tissue from young adult mice born to lean or obese mothers; offspring were weaned onto either a low-fat control diet or a high-fat Western-style diet. We found 8 cardiac miRNAs that were significantly altered in response to maternal obesity, but only when the offspring were challenged postnatally with the Western diet. In contrast, postnatal exposure to the diet alone induced significant changes to the expression of a much larger number of miRNAs (33 in offspring of lean and 46 in offspring of obese). Many of the affected miRNAs have previously been implicated in various cardiac pathologies. The pervasive cardiac miRNA changes induced by a Western diet suggest that an individual's lifestyle choices outweigh the impact of any programming effects by maternal obesity on miRNA-related cardiac health.  相似文献   
710.
The Lowry method was used in this study to measure protein inHaemophilus influenzae type b (Hib) conjugate vaccines (polyribosylibitol phosphate-tetanus toxoid; PRP-TT) using deoxycholic acid (DOC) to induce protein precipitation. Trichloroacetic acid (TCA) did not induce precipitation adequately from the Hib conjugate bulk and the freeze-dried Hib conjugate product. Its yield was approximately 50%. The matrix structure of Hib conjugate inhibits precipitation by TCA. Although the Lowry method can be carried out without precipitation in Hib conjugate bulk when no residual impurities (adipic acid dihydrazide [ADH], 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-HCI [EDAC], phenol and cyanogens bromide [CNBr],etc.) are present, it cannot be used for Hib conjugate products that contain sucrose 8.5%, because 8.5% concentration of sucrose enhanced the protein concentration. DOC- and HCI-induced precipitation is an alternative method for evaluating the protein content of the Hib conjugate bulk and the Hib conjugate product. The precipitation was optimal with a final concentrate of 0.1% for DOC at 4°C and pH 2. This Lowry method, using DOC/HCI precipitation to induce protein precipitation, was confirmed a consistent, reproducible, and valid test for proteins in Hib conjugate bulk and its freeze-dried product.  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