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   6519篇
  免费   448篇
  国内免费   2篇
  2023年   21篇
  2022年   75篇
  2021年   161篇
  2020年   77篇
  2019年   99篇
  2018年   142篇
  2017年   123篇
  2016年   209篇
  2015年   294篇
  2014年   330篇
  2013年   431篇
  2012年   538篇
  2011年   621篇
  2010年   329篇
  2009年   287篇
  2008年   381篇
  2007年   454篇
  2006年   376篇
  2005年   332篇
  2004年   316篇
  2003年   328篇
  2002年   319篇
  2001年   65篇
  2000年   42篇
  1999年   44篇
  1998年   47篇
  1997年   43篇
  1996年   33篇
  1995年   31篇
  1994年   18篇
  1993年   21篇
  1992年   18篇
  1991年   20篇
  1989年   16篇
  1988年   13篇
  1985年   11篇
  1984年   16篇
  1983年   10篇
  1982年   11篇
  1981年   10篇
  1980年   15篇
  1977年   22篇
  1976年   20篇
  1975年   13篇
  1974年   11篇
  1973年   14篇
  1972年   16篇
  1969年   14篇
  1968年   14篇
  1966年   13篇
排序方式: 共有6969条查询结果,搜索用时 15 毫秒
81.
In view of a rapid development and increase in efficiency of organic solar cells, reaching their long‐term operational stability represents now one of the main challenges to be addressed on the way toward commercialization of this photovoltaic technology. However, intrinsic degradation pathways occurring in organic solar cells under realistic operational conditions remain poorly understood. The light‐induced dimerization of the fullerene‐based acceptor materials discovered recently is considered to be one of the main causes for burn‐in degradation of organic solar cells. In this work, it is shown that not only the fullerene derivatives but also different types of conjugated polymers and small molecules undergo similar light‐induced crosslinking regardless of their chemical composition and structure. In the case of conjugated polymers, crosslinking of macromolecules leads to a rapid increase in their molecular weight and consequent loss of solubility, which can be revealed in a straightforward way by gel permeation chromatography analysis via a reduction/loss of signal and/or smaller retention times. Results of this work, thus, shift the paradigm of research in the field toward designing a new generation of organic absorbers with enhanced intrinsic photochemical stability in order to reach practically useful operation lifetimes required for successful commercialization of organic photovoltaics.  相似文献   
82.
Limnology - In 2003–2016, the composition and structure of macrozoobenthic communities of 49 lakes in three natural zones (taiga, forest-steppe, and steppe) of Western Siberia were...  相似文献   
83.
From 50 to 90% of wild plant species worldwide produce seeds that are dormant upon maturity, with specific dormancy traits driven by species' occurrence geography, growth form, and genetic factors. While dormancy is a beneficial adaptation for intact natural systems, it can limit plant recruitment in restoration scenarios because seeds may take several seasons to lose dormancy and consequently show low or erratic germination. During this time, seed predation, weed competition, soil erosion, and seed viability loss can lead to plant re‐establishment failure. Understanding and considering seed dormancy and germination traits in restoration planning are thus critical to ensuring effective seed management and seed use efficiency. There are five known dormancy classes (physiological, physical, combinational, morphological, and morphophysiological), each requiring specific cues to alleviate dormancy and enable germination. The dormancy status of a seed can be determined through a series of simple steps that account for initial seed quality and assess germination across a range of environmental conditions. In this article, we outline the steps of the dormancy classification process and the various corresponding methodologies for ex situ dormancy alleviation. We also highlight the importance of record‐keeping and reporting of seed accession information (e.g. geographic coordinates of the seed collection location, cleaning and quality information, storage conditions, and dormancy testing data) to ensure that these factors are adequately considered in restoration planning.  相似文献   
84.
85.
Probiotics and Antimicrobial Proteins - Lactose intolerance is a common condition caused by lactase deficiency and may result in symptoms of lactose malabsorption (bloating, flatulence, abdominal...  相似文献   
86.
Plant diversity has a strong impact on a plethora of ecosystem functions and services, especially ecosystem carbon (C) storage. However, the potential context-dependency of biodiversity effects across ecosystem types, environmental conditions and carbon pools remains largely unknown. In this study, we performed a meta-analysis by collecting data from 95 biodiversity-ecosystem functioning (BEF) studies across 60 sites to explore the effects of plant diversity on different C pools, including aboveground and belowground plant biomass, soil microbial biomass C and soil C content across different ecosystem types. The results showed that ecosystem C storage was significantly enhanced by plant diversity, with stronger effects on aboveground biomass than on soil C content. Moreover, the response magnitudes of ecosystem C storage increased with the level of species richness and experimental duration across all ecosystems. The effects of plant diversity were more pronounced in grasslands than in forests. Furthermore, the effects of plant diversity on belowground plant biomass increased with aridity index in grasslands and forests, suggesting that climate change might modulate biodiversity effects, which are stronger under wetter conditions but weaker under more arid conditions. Taken together, these results provide novel insights into the important role of plant diversity in ecosystem C storage across critical C pools, ecosystem types and environmental contexts.  相似文献   
87.
Plant and Soil - Clear-cut logging currently is a key factor transforming forest communities in many boreal regions. The dynamics of biogeochemical processes taking place in clear-cuts makes them a...  相似文献   
88.
Objective

Chromovert® Technology is presented as a new cell engineering technology to detect and purify living cells based on gene expression.

Methods

The technology utilizes fluorogenic oligonucleotide signaling probes and flow cytometry to detect and isolate individual living cells expressing one or more transfected or endogenously-expressed genes.

Results

Results for production of cell lines expressing a diversity of ion channel and membrane proteins are presented, including heteromultimeric epithelial sodium channel (αβγ-ENaC), sodium voltage-gated ion channel 1.7 (NaV1.7-αβ1β2), four unique γ-aminobutyric acid A (GABAA) receptor ion channel subunit combinations α1β3γ2s, α2β3γ2s, α3β3γ2s and α5β3γ2s, cystic fibrosis conductance regulator (CFTR), CFTR-Δ508 and two G-protein coupled receptors (GPCRs) without reliance on leader sequences and/or chaperones. In addition, three novel plasmid-encoded sequences used to introduce 3′ untranslated RNA sequence tags in mRNA expression products and differentially-detectable fluorogenic probes directed to each are described. The tags and corresponding fluorogenic signaling probes streamline the process by enabling the multiplexed detection and isolation of cells expressing one or more genes without the need for gene-specific probes.

Conclusions

Chromovert technology is provided as a research tool for use to enrich and isolate cells engineered to express one or more desired genes.

  相似文献   
89.
90.
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