全文获取类型
收费全文 | 512篇 |
免费 | 27篇 |
专业分类
539篇 |
出版年
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 36篇 |
2013年 | 41篇 |
2012年 | 52篇 |
2011年 | 38篇 |
2010年 | 23篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 18篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1950年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有539条查询结果,搜索用时 0 毫秒
81.
Hoyeun Kim Masami Yokota Hirai Hiroaki Hayashi Mitsuo Chino Satoshi Naito Toru Fujiwara 《Planta》1999,209(3):282-289
The composition of seed storage proteins is regulated by sulfur and nitrogen supplies. Under conditions of a low sulfur-to-nitrogen
ratio, accumulation of the β-subunit of β-conglycinin, a sulfur-poor seed storage protein of soybean (Glycine max [L.] Merr.), is elevated, whereas that of glycinin, a sulfur-rich storage protein, is reduced. Using transgenic Arabidopsis thaliana [L.] Heynh., it was found that the promoter from the gene encoding the β-subunit of β-conglycinin up-regulates gene expression
under sulfur deficiency and down-regulates gene expression under nitrogen deficiency. To obtain an insight into the metabolic
control of this regulation, the concentrations of metabolites related to the sulfur assimilation pathway were determined.
Among the metabolites, O-acetyl-l-serine (OAS), one of the precursors of cysteine biosynthesis, accumulated to higher levels under low-sulfur and high-nitrogen
conditions in siliques of transgenic A. thaliana. The pattern of OAS accumulation in response to various levels of sulfur and nitrogen was similar to that of gene expression
driven by the β-subunit promoter. Elevated levels of OAS accumulation were also observed in soybean cotyledons cultured under
sulfur deficiency. Moreover, OAS applied to in-vitro cultures of immature soybean cotyledons under normal sulfate conditions
resulted in a high accumulation of the β-subunit mRNA and protein, whereas the accumulation of glycinin was reduced. These
changes were very similar to the responses observed under conditions of sulfur deficiency. Our results suggest that the level
of free OAS mediates sulfur- and nitrogen-regulation of soybean seed storage-protein composition.
Received: 6 February 1999 / Accepted: 16 March 1999 相似文献
82.
Youhei Takagi Kouhei Matsui Haruaki Nobori Haruka Maeda Akihiko Sato Takeshi Kurosu Yasuko Orba Hirofumi Sawa Kazunari Hattori Kenichi Higashino Yoshito Numata Yutaka Yoshida 《Bioorganic & medicinal chemistry letters》2017,27(15):3586-3590
NS2B-NS3 protease is an essential enzyme for the replication of dengue virus (DENV), which continues to be a serious threat to worldwide public health. We designed and synthesized a series of cyclic peptides mimicking the substrates of this enzyme, and assayed their activity against the DENV-2 NS2B-NS3 protease. The introduction of aromatic residues at the appropriate positions and conformational restriction generated the most promising cyclic peptide with an IC50 of 0.95 μM against NS2B-NS3 protease. Cyclic peptides with proper positioning of additional arginines and aromatic residues exhibited antiviral activity against DENV. Furthermore, replacing the C-terminal amide bond of the polybasic amino acid sequence with an amino methylene moiety stabilized the cyclic peptides against hydrolysis by NS2B-NS3 protease, while maintaining their enzyme inhibitory activity and antiviral activity. 相似文献
83.
Kentaro Chino Toshiaki Oda Toshiyuki Kurihara Toshihiko Nagayoshi Kohki Yoshikawa Hiroaki Kanehisa Tetsuo Fukunaga Senshi Fukashiro Yasuo Kawakami 《Journal of electromyography and kinesiology》2008,18(1):79-88
Ultrasonography was used to directly measure in vivo fascicle behavior of the medial gastrocnemius (MG) and soleus (SOL) muscles while the subjects (n=6 men) performed maximal voluntary concentric and eccentric plantar flexions at 60, 120, 180 and 240 deg/s. Fascicle shortening and lengthening velocities of MG, obtained from fascicle length changes over time, were significantly higher than those of SOL at +/-120, +/-180 and +240 deg/s, possibly reflecting physiological and mechanical differences between these muscles. On the other hand, the effective fascicle shortening and lengthening velocities, defined as the velocities in the longitudinal direction of muscle belly, were not significantly different between MG and SOL. This could be due to difference in fascicle architecture and/or the existence of mechanical linkages between these muscles. Moreover, when the contribution of tendinous tissues to muscle-tendon complex length change was determined from fascicle length, pennation angle, moment arm and joint angle, it accounted for approximately 50% in both concentric and eccentric trials, but showed considerable intra-subject variations. This result quantifiably demonstrates the importance of tendinous tissues in isokinetically controlled joint movements. 相似文献
84.
It is well known that chronic, excessive consumption of alcohol can cause brain damage/structural changes in the regions important for neurocognitive function. Some of the damages are permanent, while others are reversible. Molecular mechanisms underlying alcohol-induced and/or -related brain damage are largely unknown, although it is generally believed that three factors (ethanol, nutritious and hepatic factors) play important roles. Recently, we have been employing a high-throughput proteomics technology to investigate several alcohol-sensitive brain regions from uncomplicated and hepatic cirrhosis-complicated alcoholics to understand the mechanisms of alcohol effects on the CNS at the level of protein expression. The changes of protein expression profiles in the hippocampus of alcoholic subjects were firstly demonstrated using 2D gel electrophoresis-based proteomics. Protein expression profiles identified in the hippocampus of alcoholic subjects were significantly different from those previously identified by our group in other brain regions of the same alcoholic cases, possibly indicating that these different brain regions react differently to chronic alcohol ingestion at the level of protein expression. Identified changes of protein expression associated with astrocyte and oxidative stress may indicate the possibility that increased levels of CNS ammonia and reactive oxygen species induced by alcoholic mild hepatic damage/dysfunction could cause selective damage in astrocytes of the hippocampus. Although our data did not demonstrate any evidence of direct alcohol effects to induce the alteration of protein expression in association with brain damage, high-throughput neuroproteomics approaches have proved to have the potential to dissect the mechanisms of complex brain disorders. Proteomics studies on human hippocampus, an important region for neurocognitive function and psychiatric illnesses (e.g., Alzheimer's disease, alcoholism and schizophrenia) are still sparse, and further investigation is warranted to understand the underlying mechanisms. 相似文献
85.
Tamura H Saito Y Ashida H Inoue T Kai Y Yokota A Matsumura H 《Protein science : a publication of the Protein Society》2008,17(1):126-135
The methionine salvage pathway (MSP) plays a crucial role in recycling a sulphahydryl derivative of the nucleoside. Recently, the genes and reactions in MSP from Bacillus subtilis have been identified, where 5-methylthioribose 1-phosphate isomerase (M1Pi) catalyzes a conversion of 5-methylthioribose 1-phosphate (MTR-1-P) to 5-methylthioribulose 1-phosphate (MTRu-1-P). Herein, we report the crystal structures of B. subtilis M1Pi (Bs-M1Pi) in complex with its product MTRu-1-P, and a sulfate at 2.4 and 2.7 A resolution, respectively. The electron density clearly shows the presence of each compound in the active site. The structural comparison with other homologous proteins explains how the substrate uptake of Bs-M1Pi may be induced by an open/closed transition of the active site. The highly conserved residues at the active site, namely, Cys160 and Asp240 are most likely to be involved in catalysis. The structural analysis sheds light on its catalytic mechanism of M1Pi. 相似文献
86.
Haruka Imada Masahito Hoki Yuji Suehiro Teruhiro Okuyama Daisuke Kurabayashi Atsuko Shimada Kiyoshi Naruse Hiroyuki Takeda Takeo Kubo Hideaki Takeuchi 《PloS one》2010,5(6)
Background
In animal groups such as herds, schools, and flocks, a certain distance is maintained between adjacent individuals, allowing them to move as a cohesive unit. Proximate causations of the cohesive and coordinated movement under dynamic conditions, however, have been poorly understood.Methodology/Principal Findings
We established a novel and simple behavioral assay using pairs of small fish (medaka and dwarf pufferfish) by eliciting a simultaneous optomotor response (OMR). We demonstrated that two homospecific fish began to move cohesively and maintained a distance of 2 to 4 cm between them when an OMR was elicited simultaneously in the fish. The coordinated and cohesive movement was not exhibited under a static condition. During the cohesive movement, the relative position of the two fish was not stable. Furthermore, adult medaka exhibited the cohesive movement but larvae did not, despite the fact that an OMR could be elicited in larvae, indicating that this ability to coordinate movement develops during maturation. The cohesive movement was detected in homospecific pairs irrespective of body-color, sex, or albino mutation, but was not detected between heterospecific pairs, suggesting that coordinated movement is based on a conspecific interaction.Conclusions/Significance
Our findings demonstrate that coordinated behavior between a pair of animals was elicited by a simultaneous OMR in two small fish. This is the first report to demonstrate induction of a schooling-like movement in a pair of fish by an OMR and to investigate the effect of age, sex, body color, and species on coordination between animals under a dynamic condition. 相似文献87.
88.
Kentaro Honda Nobuyuki Takahashi Keiichi Yamamoto Haruka Kagiwada Yuichi Tsuda Yoko Mitani Kazushi Miyashita 《Ichthyological Research》2017,64(3):357-364
Behavior of adult Parahucho perryi was examined using bio-logging and acoustic telemetry concurrently in the Bekanbeushi River system, eastern Hokkaido, Japan, in 2009 and 2010. Based on 46.1–87.9 h data from five P. perryi (69.0–80.0 cm fork length) caught from Lake Akkeshi, they used upstream (n = 2), midstream (n = 3), and downstream (n = 4) habitats. Large variability in diel activity and depth occupation existed in each stream habitat; however, fish in the downstream habitat tended to be more active than those in the upper habitats and mainly occupied shallower depths than mean bottom depth in this habitat. 相似文献
89.
90.
The chloroplast atpB and atpE genes encode subunits β and ε of the ATP synthase, respectively. They are co-transcribed as dicistronic mRNAs in flowering plants. An unusual feature is an overlap (AUGA) of the atpB stop codon (UGA) with the atpE start codon (AUG). Hence, atpE translation has been believed to depend on atpB translation (i.e. translational coupling). Using an in vitro translation system from tobacco chloroplasts, we showed that both atpB and atpE cistrons are translated from the tobacco dicistronic mRNA, and that the efficiency of atpB translation is higher than that of atpE translation. When the atpB 5′-UTR was replaced with lower efficiency 5′-UTRs, atpE translation was higher than atpB translation. Removal of the entire atpB 5′-UTR arrested atpB translation but atpE translation still proceeded. Introduction of a premature stop codon in the atpB cistron did not abolish atpE translation. These results indicate that atpE translation is independent of atpB translation. Mutation analysis showed that the atpE cistron possesses its own cis-element(s) for translation, located ~25 nt upstream from the start codon. 相似文献