全文获取类型
收费全文 | 1158篇 |
免费 | 77篇 |
出版年
2022年 | 3篇 |
2021年 | 20篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 26篇 |
2015年 | 38篇 |
2014年 | 45篇 |
2013年 | 66篇 |
2012年 | 88篇 |
2011年 | 82篇 |
2010年 | 57篇 |
2009年 | 46篇 |
2008年 | 78篇 |
2007年 | 85篇 |
2006年 | 81篇 |
2005年 | 77篇 |
2004年 | 73篇 |
2003年 | 69篇 |
2002年 | 72篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 7篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有1235条查询结果,搜索用时 31 毫秒
101.
Liao S Poonpairoj P Ko KC Takatuska Y Yamaguchi Y Abe N Kaneko J Kamio Y 《Bioscience, biotechnology, and biochemistry》2008,72(2):445-455
Selenomonas ruminantium synthesizes cadaverine and putrescine from L-lysine and L-ornithine as the essential constituents of its peptidoglycan by a constitutive lysine/ornithine decarboxylase (LDC/ODC). S. ruminantium grew normally in the presence of the specific inhibitor for LDC/ODC, DL-alpha-difluoromethylornithine, when arginine was supplied in the medium. In this study, we discovered the presence of arginine decarboxylase (ADC), the key enzyme in agmatine pathway for putrescine synthesis, in S. ruminantium. We purified and characterized ADC and cloned its gene (adc) from S. ruminantium chromosomal DNA. ADC showed more than 60% identity with those of LDC/ODC/ADCs from Gram-positive bacteria, but no similarity to that from Gram-negative bacteria. In this study, we also cloned the aguA and aguB genes, encoding agmatine deiminase (AguA) and N-carbamoyl-putrescine amidohydrolase (AguB), both of which are involved in conversion from agmatine into putrescine. AguA and AguB were expressed in S. ruminantium. Hence, we concluded that S. ruminantium has both ornithine and agmatine pathways for the synthesis of putrescine. 相似文献
102.
103.
Zui Fujimoto Hitomi Ichinose Tomoko Maehara Mariko Honda Motomitsu Kitaoka Satoshi Kaneko 《The Journal of biological chemistry》2010,285(44):34134-34143
Exo-1,5-α-l-arabinofuranosidases belonging to glycoside hydrolase family 43 have strict substrate specificity. These enzymes hydrolyze only the α-1,5-linkages of linear arabinan and arabino-oligosaccharides in an exo-acting manner. The enzyme from Streptomyces avermitilis contains a core catalytic domain belonging to glycoside hydrolase family 43 and a C-terminal arabinan binding module belonging to carbohydrate binding module family 42. We determined the crystal structure of intact exo-1,5-α-l-arabinofuranosidase. The catalytic module is composed of a 5-bladed β-propeller topologically identical to the other family 43 enzymes. The arabinan binding module had three similar subdomains assembled against one another around a pseudo-3-fold axis, forming a β-trefoil-fold. A sugar complex structure with α-1,5-l-arabinofuranotriose revealed three subsites in the catalytic domain, and a sugar complex structure with α-l-arabinofuranosyl azide revealed three arabinose-binding sites in the carbohydrate binding module. A mutagenesis study revealed that substrate specificity was regulated by residues Asn-159, Tyr-192, and Leu-289 located at the aglycon side of the substrate-binding pocket. The exo-acting manner of the enzyme was attributed to the strict pocket structure of subsite −1, formed by the flexible loop region Tyr-281–Arg-294 and the side chain of Tyr-40, which occupied the positions corresponding to the catalytic glycon cleft of GH43 endo-acting enzymes. 相似文献
104.
A novel selenium-containing compound having a selenium atom in the imidazole
ring,
2-selenyl-Nα,Nα,Nα-trimethyl-l-histidine,
3-(2-hydroseleno-1H-imidazol-5-yl)-2-(trimethylammonio)propanoate,
was identified from the blood and other tissues of the bluefin tuna,
Thunnus orientalis. The selenium-containing compound was
purified from the tuna blood in several chromatographic steps. High resolution
mass spectrometry and nuclear magnetic resonance spectroscopy showed that the
exact mass of the [M+H]+
ion of the compound was 533.0562 and the molecular formula was
C18H29N6O4Se2. Its
gross structure was assigned as the oxidized dimeric form of an ergothioneine
selenium analog in which the sulfur of ergothioneine is replaced by selenium.
Therefore, we named this novel selenium-containing compound
“selenoneine.” By speciation analysis of organic selenium
compounds using liquid chromatography inductively coupled plasma mass
spectrometry, selenoneine was found widely distributed in various tissues of the
tuna, with the highest concentration in blood; mackerel blood contained similar
levels. Selenoneine was measurable at 2–4 orders of magnitude lower
concentration in a limited set of tissues from squid, tilapia, pig, and chicken.
Quantitatively, selenoneine is the predominant form of organic selenium in tuna
tissues. 相似文献
105.
Mukai T Maeda Y Tamura T Matsuoka M Tsukamoto Y Makino M 《Journal of immunology (Baltimore, Md. : 1950)》2010,185(10):6234-6243
To activate naive T cells convincingly using Mycobacterium bovis bacillus Calmette-Guérin (BCG), recombinant BCG (BCG-D70M) that was deficient in urease, expressed with gene encoding the fusion of BCG-derived heat shock protein (HSP) 70 and Mycobacterium leprae-derived major membrane protein (MMP)-II, one of the immunodominant Ags of M. leprae, was newly constructed. BCG-D70M was more potent in activation of both CD4(+) and CD8(+) subsets of naive T cells than recombinant BCGs including urease-deficient BCG and BCG-70M secreting HSP70-MMP-II fusion protein. BCG-D70M efficiently activated dendritic cells (DCs) to induce cytokine production and phenotypic changes and activated CD4(+) T cells even when macrophages were used as APCs. The activation of both subsets of T cells was MHC and CD86 dependent. Pretreatment of DCs with chloroquine inhibited both surface expression of MMP-II on DCs and the activation of T cells by BCG-D70M-infected APCs. The naive CD8(+) T cell activation was inhibited by treatment of DCs with brefeldin A and lactacystin so that the T cell was activated by TAP- and proteosome-dependent cytosolic cross-priming pathway. From naive CD8(+) T cells, effector T cells producing perforin and memory T cells having migration markers were produced by BCG-D70M stimulation. BCG-D70M primary infection in C57BL/6 mice produced T cells responsive to in vitro secondary stimulation with MMP-II and HSP70 and more efficiently inhibited the multiplication of subsequently challenged M. leprae than vector control BCG. These results indicate that the triple combination of HSP70, MMP-II, and urease depletion may provide a useful tool for inducing better activation of naive T cells. 相似文献
106.
107.
Kita A Sakurai Y Myers DR Rounsevell R Huang JN Seok TJ Yu K Wu MC Fletcher DA Lam WA 《PloS one》2011,6(10):e26437
To activate clot formation and maintain hemostasis, platelets adhere and spread onto sites of vascular injury. Although this process is well-characterized biochemically, how the physical and spatial cues in the microenvironment affect platelet adhesion and spreading remain unclear. In this study, we applied deep UV photolithography and protein micro/nanostamping to quantitatively investigate and characterize the spatial guidance of platelet spreading at the single cell level and with nanoscale resolution. Platelets adhered to and spread only onto micropatterned collagen or fibrinogen surfaces and followed the microenvironmental geometry with high fidelity and with single micron precision. Using micropatterned lines of different widths, we determined that platelets are able to conform to micropatterned stripes as thin as 0.6 μm and adopt a maximum aspect ratio of 19 on those protein patterns. Interestingly, platelets were also able to span and spread over non-patterned regions of up to 5 μm, a length consistent with that of maximally extended filopodia. This process appears to be mediated by platelet filopodia that are sensitive to spatial cues. Finally, we observed that microenvironmental geometry directly affects platelet biology, such as the spatial organization and distribution of the platelet actin cytoskeleton. Our data demonstrate that platelet spreading is a finely-tuned and spatially-guided process in which spatial cues directly influence the biological aspects of how clot formation is regulated. 相似文献
108.
109.
110.
Yumiko Ishikawa Kazuyuki Kobayashi Masatsugu Yamamoto Kyosuke Nakata Tetsuya Takagawa Yasuhiro Funada Yoshikazu Kotani Hajime Karasuyama Masaru Yoshida Yoshihiro Nishimura 《Respiratory research》2011,12(1):42