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   469篇
  免费   32篇
  2023年   5篇
  2022年   12篇
  2021年   17篇
  2020年   15篇
  2019年   17篇
  2018年   8篇
  2017年   22篇
  2016年   26篇
  2015年   30篇
  2014年   25篇
  2013年   35篇
  2012年   46篇
  2011年   32篇
  2010年   23篇
  2009年   20篇
  2008年   26篇
  2007年   15篇
  2006年   21篇
  2005年   21篇
  2004年   11篇
  2003年   12篇
  2002年   6篇
  2001年   12篇
  2000年   7篇
  1999年   5篇
  1998年   3篇
  1996年   3篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   1篇
  1986年   2篇
  1985年   1篇
  1981年   3篇
  1979年   3篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1973年   3篇
  1972年   1篇
排序方式: 共有501条查询结果,搜索用时 15 毫秒
481.
482.
The interaction between a synthesized dye with proteins, bovine, and human serum albumin (BSA, HSA, respectively) under physiological conditions has been characterized in detail, by means of steady-state and time-resolved fluorescence, UV–vis absorption, and circular dichroism (CD) techniques. An extensive time-resolved fluorescence spectroscopic characterization of the quenching process has been undertaken in conjugation with temperature-dependent fluorescence quenching studies to divulge the actual quenching mechanism. From the thermodynamic observations, it is clear that the binding process is a spontaneous molecular interaction, in which van der Waals and hydrogen bonding interactions play the major roles. The UV–vis absorption and CD results confirm that the dye can induce conformational and micro-environmental changes of both the proteins. In addition, the dye binding provokes the functionality of the native proteins in terms of esterase-like activity. The average binding distance (r) between proteins and dye has been calculated using FRET. Cytotoxicity and antiviral effects of the dye have been found using Vero cell and HSV-1F virus by performing MTT assay. The AutoDock-based docking simulation reveals the probable binding location of dye within the sub-domain IIA of HSA and IB of BSA.  相似文献   
483.
484.
We propose a constrained maximum partial likelihood estimator for dimension reduction in integrative (e.g., pan-cancer) survival analysis with high-dimensional predictors. We assume that for each population in the study, the hazard function follows a distinct Cox proportional hazards model. To borrow information across populations, we assume that each of the hazard functions depend only on a small number of linear combinations of the predictors (i.e., “factors”). We estimate these linear combinations using an algorithm based on “distance-to-set” penalties. This allows us to impose both low-rankness and sparsity on the regression coefficient matrix estimator. We derive asymptotic results that reveal that our estimator is more efficient than fitting a separate proportional hazards model for each population. Numerical experiments suggest that our method outperforms competitors under various data generating models. We use our method to perform a pan-cancer survival analysis relating protein expression to survival across 18 distinct cancer types. Our approach identifies six linear combinations, depending on only 20 proteins, which explain survival across the cancer types. Finally, to validate our fitted model, we show that our estimated factors can lead to better prediction than competitors on four external datasets.  相似文献   
485.
486.
During the last two decades, the DNA barcode development towards microbial community has increased dramatically. DNA barcode development is related to error-free and quick species identification which aid in understanding the microbial biodiversity, as well as the diseases related to microbial species. Here, we seek to evaluate the so-called barcoding initiatives for the microbial communities and the emerging trends in this field. In this paper, we describe the development of DNA marker-based DNA barcoding system, comparison between routine species identification and DNA barcode, and microbial biodiversity and DNA barcode for microbial communities. Two major topics, such as the molecular diversity of viruses and barcode for viruses have been discussed at the same time. We demonstrate the current status and the maker of DNA barcode for bacteria, algae, fungi, and protozoa. Furthermore, we argue about the promises, limitations, and present and future challenges of microbial barcode development.  相似文献   
487.
The present study demonstrates a process engineering strategy to achieve high butanol titer and productivity from wild type Clostridium acetobutylicum MTCC 11274. In the first step, two different media were optimized with the objectives of maximizing the biomass and butanol productivity, respectively. In the next step, attributes of these two media compositions were integrated to design a two-stage fed-batch process which resulted in maximal butanol productivity of 0.55 g L−1 h−1 with titer of 13.1 g L−1. Further, two-stage fed-batch process along with combinatorial use of magnesium limitation and calcium supplementation resulted in the highest butanol titer and productivity of 16.5 g L−1 and 0.59 g L−1 h−1, respectively. Finally, integration of the process with gas stripping and modulation of feeding duration resulted in a cumulative butanol titer of 54.3 g L−1 and productivity of 0.58 g L−1 h−1. The strategy opens up possibility of developing a viable butanol bioprocess. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2771, 2019.  相似文献   
488.
Four heavy metal salts, nickel sulphate, mercuric chloride, cadmium sulphate and zinc sulphate, were tested for induction of sister chromatid exchange (SCE) in root meristem cells ofAllium cepa. A simple modified Feulgen staining procedure was employed for SCE-analysis. Maleic hydrazide and paraquat were included for comparison. An evaluation of genotoxicity of the above test chemicals made on the basis of SCE-assay was found positive for all the test chemicals with exception of zinc sulphate which gave a weak positive result.  相似文献   
489.
490.
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