全文获取类型
收费全文 | 5103篇 |
免费 | 377篇 |
国内免费 | 41篇 |
专业分类
5521篇 |
出版年
2024年 | 13篇 |
2023年 | 27篇 |
2022年 | 91篇 |
2021年 | 133篇 |
2020年 | 82篇 |
2019年 | 118篇 |
2018年 | 148篇 |
2017年 | 128篇 |
2016年 | 190篇 |
2015年 | 280篇 |
2014年 | 325篇 |
2013年 | 354篇 |
2012年 | 450篇 |
2011年 | 431篇 |
2010年 | 232篇 |
2009年 | 200篇 |
2008年 | 307篇 |
2007年 | 278篇 |
2006年 | 215篇 |
2005年 | 211篇 |
2004年 | 235篇 |
2003年 | 174篇 |
2002年 | 156篇 |
2001年 | 116篇 |
2000年 | 106篇 |
1999年 | 71篇 |
1998年 | 37篇 |
1997年 | 25篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 23篇 |
1993年 | 18篇 |
1992年 | 39篇 |
1991年 | 31篇 |
1990年 | 30篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1981年 | 8篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有5521条查询结果,搜索用时 0 毫秒
951.
952.
An YS Lee E Kang MH Hong HS Kim MR Jang WS Son Y Yi JY 《Journal of cellular physiology》2011,226(5):1204-1213
The therapeutic use of ionizing radiation (e.g., X-rays and γ-rays) needs to inflict minimal damage on non-target tissue. Recent studies have shown that substance P (SP) mediates multiple activities in various cell types, including cell proliferation, anti-apoptotic responses, and inflammatory processes. The present study investigated the effects of SP on γ-irradiated bone marrow stem cells (BMSCs). In mouse bone marrow extracts, SP prolonged activation of Erk1/2 and enhanced Bcl-2 expression, but attenuated the activation of apoptotic molecules (e.g., p38 and cleaved caspase-3) and down-regulated Bax. We also observed that SP-decreased apoptotic cell death and stimulated cell proliferation in γ-irradiated mouse bone marrow tissues through TUNEL assay and PCNA analysis. To determine how SP affects bone marrow stem cell populations, mouse bone marrow cells were isolated and colony-forming unit (CFU) of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) was estimated. SP-pretreated ones showed higher CFUs of MSC and HSC than untreated ones. Furthermore, when SP was pretreated in cultured human MSC, it significantly decreased apoptotic cells at 48 and 72 h after γ-irradiation. Compared with untreated cells, SP-treated human MSCs showed reduced cleavage of apoptotic molecules such as caspase-8, -9, -3, and poly ADP-ribose polymerase (PARP). Thus, our results suggest that SP alleviates γ-radiation-induced damage to mouse BMSCs and human MSCs via regulation of the apoptotic pathway. 相似文献
953.
954.
Temperature sensation initiates from the activation of cellular receptors when the cell is exposed to a decrease in temperature. Here, we applied a phosphoproteome profiling approach to the human lung epithelial cell line BEAS‐2B to elucidate cellular cold‐responsive processes. The primary aim of this study was to determine which intracellular changes of phosphorylation are accompanied by cold sensation. Eighteen protein spots that exhibited differentially phosphorylated changes in cells were identified. Most of the proteins that were phosphorylated after 5 or 10 min were returned to control levels after 30 or 60 min. Identified proteins were mainly RNA‐related (i.e., they were involved in RNA binding and splicing). Temperature (18 and 10°C) stimuli showed homologies that were detected for time course changes in phosphoproteome. The data indicated a time‐shift between two temperatures. The phosphorylation of putative cold responsive markers, such as ribosomal protein large P0 and heterochromatin‐associated proteins 1, were verified by Western blotting in cells transfected with TRPM8 or TRPA1. J. Cell. Biochem. 112: 633–642, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
955.
Many indicators of protein evolutionary rate have been proposed, but some of them are interrelated. The purpose of this study is to disentangle their correlations. We assess the strength of each indicator by controlling for the other indicators under study. We find that the number of microRNA (miRNA) types that regulate a gene is the strongest rate indicator (a negative correlation), followed by disorder content (the percentage of disordered regions in a protein, a positive correlation); the strength of disorder content as a rate indicator is substantially increased after controlling for the number of miRNA types. By dividing proteins into lowly and highly intrinsically disordered proteins (L-IDPs and H-IDPs), we find that proteins interacting with more H-IDPs tend to evolve more slowly, which largely explains the previous observation of a negative correlation between the number of protein-protein interactions and evolutionary rate. Moreover, all of the indicators examined here, except for the number of miRNA types, have different strengths in L-IDPs and in H-IDPs. Finally, the number of phosphorylation sites is weakly correlated with the number of miRNA types, and its strength as a rate indicator is substantially reduced when other indicators are considered. Our study reveals the relative strength of each rate indicator and increases our understanding of protein evolution. 相似文献
956.
A fundamental question that applies to all organisms is how barrier epithelia efficiently manage continuous contact with microorganisms. Here, we show that in Drosophila an extracellular immune-regulated catalase (IRC) mediates a key host defense system that is needed during host-microbe interaction in the gastrointestinal tract. Strikingly, adult flies with severely reduced IRC expression show high mortality rates even after simple ingestion of microbe-contaminated foods. However, despite the central role that the NF-kappaB pathway plays in eliciting antimicrobial responses, NF-kappaB pathway mutant flies are totally resistant to such infections. These results imply that homeostasis of redox balance by IRC is one of the most critical factors affecting host survival during continuous host-microbe interaction in the gastrointestinal tract. 相似文献
957.
Schneeweiss GM Colwell A Park JM Jang CG Stuessy TF 《Molecular phylogenetics and evolution》2004,30(2):465-478
Orobanche is the largest genus among the holoparasitic members of Orobanchaceae. We present the first molecular phylogenetic analysis (using nuclear ITS sequences) that includes members of all sections of Orobanche, Gymnocaulis, Myzorrhiza, Trionychon, and Orobanche. Orobanche is not monophyletic, but falls into two lineages: (1) the Orobanche group comprises Orobanche sect. Orobanche and the small Near Asian genus Diphelypaea and is characterized by a chromosome base number of x=19 and (2) the Phelipanche group contains Orobanche sects. Gymnocaulis, Myzorrhiza, and Trionychon and possesses a chromosome base number of x=12. The relationships between these two groups and to other genera such as Boschniakia or Cistanche remain unresolved. Within the Orobanche group, Orobanche macrolepis and Orobanche anatolica (including Orobanche colorata) constitute two phylogenetically distinct lineages. Intrasectional structurings proposed by some authors for O. sect. Orobanche are not confirmed by the molecular data. In most cases, intraspecific sequence divergence between accessions, if present, is negligible and not correlated with morphological or ecological traits. In a few cases, however, there is evidence for the presence of cryptic taxa. 相似文献
958.
959.
In yeast, certain resident trans-Golgi network (TGN) proteins achieve steady-state localization by cycling through late endosomes. Here, we show that chitin synthase III (Chs3p), an enzyme involved in the assembly of the cell wall at the mother-bud junction, populates an intracellular reservoir that is maintained by a cycle of transport between the TGN and early endosomes. Traffic of Chs3p from the TGN/early endosome to the cell surface requires CHS5 and CHS6, mutant alleles of which trap Chs3p in the TGN/early endosome. Disruption of the clathrin adaptor protein complex 1 (AP-1) restores Chs3p transport to the plasma membrane. Similarly, in AP-1 deficient cells, the resident TGN/early endosome syntaxin, Tlg1p, is missorted. We propose that clathrin and AP-1 act to recycle Chs3p and Tlg1p from the early endosome to the TGN. 相似文献
960.
Chuang Xue Jing-Bo Zhao Li-Jie Chen Feng-Wu Bai Shang-Tian Yang Jian-Xin Sun 《Applied microbiology and biotechnology》2014,98(8):3463-3474
Butanol has recently gained increasing interest due to escalating prices in petroleum fuels and concerns on the energy crisis. However, the butanol production cost with conventional acetone–butanol–ethanol fermentation by Clostridium spp. was higher than that of petrochemical processes due to the low butanol titer, yield, and productivity in bioprocesses. In particular, a low butanol titer usually leads to an extremely high recovery cost. Conventional biobutanol recovery by distillation is an energy-intensive process, which has largely restricted the economic production of biobutanol. This article thus reviews the latest studies on butanol recovery techniques including gas stripping, liquid–liquid extraction, adsorption, and membrane-based techniques, which can be used for in situ recovery of inhibitory products to enhance butanol production. The productivity of the fermentation system is improved efficiently using the in situ recovery technology; however, the recovered butanol titer remains low due to the limitations from each one of these recovery technologies, especially when the feed butanol concentration is lower than 1 % (w/v). Therefore, several innovative multi-stage hybrid processes have been proposed and are discussed in this review. These hybrid processes including two-stage gas stripping and multi-stage pervaporation have high butanol selectivity, considerably higher energy and production efficiency, and should outperform the conventional processes using single separation step or method. The development of these new integrated processes will give a momentum for the sustainable production of industrial biobutanol. 相似文献