全文获取类型
收费全文 | 2411篇 |
免费 | 139篇 |
出版年
2022年 | 7篇 |
2021年 | 23篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 28篇 |
2016年 | 32篇 |
2015年 | 63篇 |
2014年 | 71篇 |
2013年 | 146篇 |
2012年 | 134篇 |
2011年 | 158篇 |
2010年 | 104篇 |
2009年 | 88篇 |
2008年 | 150篇 |
2007年 | 138篇 |
2006年 | 134篇 |
2005年 | 120篇 |
2004年 | 159篇 |
2003年 | 145篇 |
2002年 | 134篇 |
2001年 | 49篇 |
2000年 | 39篇 |
1999年 | 50篇 |
1998年 | 29篇 |
1997年 | 34篇 |
1996年 | 36篇 |
1995年 | 42篇 |
1994年 | 19篇 |
1993年 | 24篇 |
1992年 | 36篇 |
1991年 | 37篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 28篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 21篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有2550条查询结果,搜索用时 109 毫秒
991.
Zhang M Deng Y Luo Y Zhang S Zou H Cai F Wada K Song W 《Journal of neurochemistry》2012,120(6):1129-1138
Deposition of amyloid β protein (Aβ) in the brain is the hallmark of Alzheimer's disease (AD) pathogenesis. Beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is the β-secretase in vivo essential for generation of Aβ. Previously we demonstrated that BACE1 is ubiquitinated and the degradation of BACE1 is mediated by the ubiquitin-proteasome pathway (UPP). However the mechanism underlying regulation of BACE1 degradation by UPP remains elusive. Ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme highly specific to neuron, catalyzing the hydrolysis of ubiquitin conjugates from ubiquitinated substrates. UCHL1 regulates ubiquitin-dependent protein degradation. However, whether UCHL1 is particularly involved in the proteasomal degradation of BACE1 and what is the role of UCHL1 in AD pathogenesis remain elusive. To investigate the effect of UCHL1 on BACE1 degradation, HUCH cells, a UCHL1 stably over-expressed HEK293 cell line, was established. We found that inhibition of UCHL1 significantly increased BACE1 protein level in a time-dependent manner. Half life of BACE1 was reduced in HUCH cells compared with HEK. Over-expression of UCHL1 decreased APP C-terminal fragment C99 and Aβ levels in HUCH cells. Moreover, disruption of Uchl1 gene significantly elevated levels of endogenous BACE1, C99 and Aβ in the Uchl1-null gad mice. These results demonstrated that UCHL1 accelerates BACE1 degradation and affects APP processing and Aβ production. This study suggests that potentiation of UCHL1 might be able to reduce the level of BACE1 and Aβ in brain, which makes it a novel target for AD drug development. 相似文献
992.
993.
Mitsubayashi K Matsunaga H Nishio G Toda S Nakanishi Y 《Biosensors & bioelectronics》2005,20(8):1573-1579
Two kinds of bioelectronic gas sensors (bio-sniffer) incorporating alcohol oxidase (AOD) and aldehyde dehydrogenase (ALDH) were developed for the convenient analysis of ethanol and acetaldehyde in expired gas, respectively. The sniffer devices for gaseous ethanol and acetaldehyde were constructed by immobilizing enzyme on electrodes covered with filter paper and hydrophilic PTFE membrane, respectively. The AOD and ALDH sniffers were used in the gas phase to measure ethanol vapor from 1.0 to 500 ppm, and acetaldehyde from 0.11 to 10 ppm covering the concentration range encountered in breath after alcohol consumption. Both bio-sniffers displayed good gas selectivity which was attributed to the substrate specificity of the relevant enzymes (AOD and ALDH) as gas recognition material. From the results of physiological application, the bio-sniffers could monitor the concentration changes in breath ethanol and acetaldehyde after drinking. The ethanol and acetaldehyde concentrations in expired air from ALDH2 [-] (aldehyde dehydrogenase type 2 negative) subjects were higher than that of the ALDH2 [+] (positive) subjects. The results indicated that the lower activity of ALDH2 induced an adverse effect on ethanol metabolism, leading to ethanol and acetaldehyde remaining in the human body, even human expired air. 相似文献
994.
The bvg‐repressed gene brtA,encoding biofilm‐associated surface adhesin,is expressed during host infection by Bordetella bronchiseptica
下载免费PDF全文
![点击此处可从《Microbiology and immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sayaka Nishikawa Naoaki Shinzawa Keiji Nakamura Keisuke Ishigaki Hiroyuki Abe Yasuhiko Horiguchi 《Microbiology and immunology》2016,60(2):93-105
995.
Tomoko Yoshino Taisei Nishimura Tetsushi Mori Shigeya Suzuki Hideki Kambara Haruko Takeyama Tadashi Matsunaga 《Biotechnology and bioengineering》2009,103(1):130-137
There is a high demand for inexpensive and high‐throughput DNA sequencing technologies in molecular biology and applied biosciences. In this study, novel nano‐sized magnetic particles displaying enzymes for pyrosequencing, a rather novel bioluminometric DNA sequencing method based on the sequencing‐by‐synthesis principle by employing a cascade of several enzymatic reactions, was developed. A highly thermostable enzyme, pyruvate phosphate dikinase (PPDK) which converts PPi to ATP was successfully expressed onto bacterial magnetic particles (BacMPs) using a novel protein display system of Magnetospirillum magneticum AMB‐1. The enzymatic stability of BacMPs displaying PPDK (PPDK‐BacMPs) to pH and temperature was evaluated and its broad range of properties was shown. Subsequently, PPDK‐BacMPs were applied in pyrosequencing and a target oligonucleotide was successfully sequenced. The PPDK enzyme displayed on BacMPs was shown to be recyclable in each sequence reaction as they can be manipulated by magnetic force. It was concluded that nano‐sized PPDK‐BacMPs are useful for the scale down of pyrosequencing reaction volumes, thus, permitting high‐throughput. The recycling of enzymes was also shown to be promising and applicable for the development of an inexpensive DNA sequencing at a low running cost. Biotechnol. Bioeng. 2009;103: 130–137. © 2008 Wiley Periodicals, Inc. 相似文献
996.
Yasuhiro Sugamata Tsuyoshi TanakaTadashi Matsunaga Tomoko Yoshino 《Biochemical and biophysical research communications》2014
A Gram-negative, magnetotactic bacterium, Magnetospirillum magneticum AMB-1 produces nano-sized magnetic particles (BacMPs) in the cytoplasm. Although various applications of genetically engineered BacMPs have been demonstrated, such as immunoassay, ligand–receptor interaction or cell separation, by expressing a target protein on BacMPs, it has been difficult to express disulfide-bonded proteins on BacMPs due to lack of disulfide-bond formation in the cytoplasm. Here, we propose a novel dual expression system, called in vitro docking, of a disulfide-bonded protein on BacMPs by directing an immunoglobulin Fc-fused target protein to the periplasm and its docking protein ZZ on BacMPs. By in vitro docking, an scFv–Fc fusion protein was functionally expressed on BacMPs in the dimeric or trimeric form. Our novel disulfide-bonded protein expression system on BacMPs will be useful for efficient screening of potential ligands or drugs, analyzing ligand–receptor interactions or as a magnetic carrier for affinity purification. 相似文献
997.
Tojo M Takebe A Takahashi S Tanaka K Imamura T Miyazono K Chiba T 《Journal of biochemistry》2012,151(6):621-631
Smad7 is an inhibitory molecule induced by members of the transforming growth factor-β (TGF-β) family, including TGF-β, activin, nodal and bone morphogenetic proteins (BMPs). To elucidate the in vivo functions of Smad7, we generated conditional Smad7-knockout mice in which the Mad homology 2 (MH2) domain and the poly (A) signal sequence were flanked with loxP sites (floxed). The Smad7-floxed mice exhibited no obvious phenotype. Smad7 total-null mice on a C57BL/6 background died within a few days of birth, whereas mice with an ICR background developed to adulthood but were significantly smaller than wild-type mice. Unexpectedly, phospho-Smad2 and phospho-Smad3 were decreased in Smad7-deficient mouse embryonic fibroblast (MEF) cells, whereas phospho-Smad1/5/8 was similarly expressed in wild-type and Smad7-deficient MEF cells. Moreover, expression levels of TGF-β type I receptor (ALK5) were higher in Smad7-deficient MEF cells than in wild-type MEF cells. Plasminogen activator inhibitor-1 (PAI-1) and inhibitor of differentiation-1 (Id-1) mRNA were similarly expressed in wild-type and Smad7-deficient MEF cells. Some differences were observed in mitogen-activated protein kinase (MAPK)-signalling between wild-type and Smad7-deficient MEF cells. We demonstrated that Smad7 plays an important role in normal mouse growth and provide a useful tool for analysing Smad7 functions in vivo. 相似文献
998.
Noriyuki Iwabuchi Noritoshi Takahashi Jin-Zhong Xiao Sumiko Yonezawa Tomoko Yaeshima Keiji Iwatsuki & Satoshi Hachimura 《FEMS immunology and medical microbiology》2009,55(3):324-334
In human trials, Bifidobacterium longum BB536 alleviates subjective symptoms of Japanese cedar pollinosis, an IgE-mediated type I allergy caused by exposure to Japanese cedar, and significantly suppresses the increase of plasma thymus- and activation-regulated chemokine (TARC) associated with pollen dispersion. In the present study, we investigated the suppressive effects of BB536 on the production of T helper type 2 (Th2)-attracting chemokines, such as TARC and macrophage-derived chemokine (MDC), together with the mechanisms of their production. Murine splenocytes were cultured with heat-killed BB536, and the levels of Th2-attracting chemokines in the supernatants were measured. TARC and MDC were produced in cultures without stimulation, and the production was significantly suppressed by BB536. These chemokines were produced by antigen-presenting cells (APCs) of splenocytes stimulated with an anti-CD40 antibody. Furthermore, TARC production was induced with granulocyte macrophage colony-stimulating factor that was produced by T cells and dendritic cells. BB536 suppressed MDC production induced with the anti-CD40 antibody by APCs from the spleen, mesenteric lymph nodes (MLNs) and Peyer's patches, and it suppressed TARC production by APCs from the spleen and MLNs. These results indicate that BB536 suppresses the production of Th2-attracting chemokines induced by the T cell–APC interaction, suggesting a novel mechanism for alleviating symptoms of allergic disorders by probiotics. 相似文献
999.
Possible cause of unnatural mass death of wild birds in a pond in Nishinomiya, Japan: sudden appearance of toxic cyanobacteria. 总被引:5,自引:0,他引:5
During the summer of 1995, about 20 spot-billed ducks died unnaturally in a pond (Shin-ike) in Nishinomiya, Hyogo Prefecture, Japan. The suspected cause was the sudden appearance of toxic freshwater bloom of cyanobacteria. However, no birds died in a nearby pond (Oo-ike) in which the cyanobacteria was also present. Morphological observation of these cyanobacteria by microscope revealed that they were almost unialgal and were both Microcystis aeruginosa. The lyophilized algal cell powder from Shin-ike contained large amounts of microcystins which showed acute toxicity for mouse, while that from Oo-ike had only a very small amount of microcystin-RR which did not show acute toxicity. Autopsy of one of the birds revealed that the liver was necrotic and severely jaundiced with a dark green color, suggesting the toxicity of the microcystins. These results point to the cause of the unnatural death of spot-billed ducks in Shin-ike as being the sudden appearance of toxic Microcystis aeruginosa. This was due to eutrophication of the pond, following the influx of untreated sewage related to damage from the Great Hanshinn Earthquake of January 1995. This is the first experimental report of toxic cyanobacteria being implicated in the mass death of wild birds in Japan. 相似文献