全文获取类型
收费全文 | 765篇 |
免费 | 71篇 |
出版年
2021年 | 9篇 |
2020年 | 4篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 45篇 |
2012年 | 28篇 |
2011年 | 43篇 |
2010年 | 28篇 |
2009年 | 31篇 |
2008年 | 39篇 |
2007年 | 40篇 |
2006年 | 33篇 |
2005年 | 31篇 |
2004年 | 34篇 |
2003年 | 42篇 |
2002年 | 22篇 |
2001年 | 21篇 |
2000年 | 46篇 |
1999年 | 35篇 |
1998年 | 18篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1970年 | 4篇 |
1969年 | 6篇 |
1968年 | 6篇 |
1966年 | 2篇 |
排序方式: 共有836条查询结果,搜索用时 625 毫秒
31.
The fluorescence properties of chlorophyll a and b monomolecular films at the air-water interface were measured by a high sensitivity fluorophotometer using the photon-counting method. The fluorescence intensity of chlorophyll molecules in monomolecular films in the absence of any diluents did not decrease simply with the mean distance of chlorphyll molecules. Over the range of the mean distances from 27 to 21 A, three fluorescence components (peaks at 685, 695 and 715 nm) of chlorophyll a were observed. In the case of chlorophyll beta, two fluorescence components (peaks at 667 and 685 nm) were observed over the range of the mean distances from 34 to 24 A. When the mean distance was 18 A, the short wavelength component of chlorophyll beta disappeared, and only the long avelength component was observed. 相似文献
32.
Effects of sodium, potassium and chloride ions on the membrane potential of Valonia aegagropila 总被引:1,自引:0,他引:1
Changes of the resting potential of Valonia cell in sea wateragainst a 10-fold increase of the external concentrations ofK$, Na$ and Cl were 1±1, 6.2±0.1 and 38.9±4mV, respectively. The potassium conductance was smaller than7 µ/cm2, while the Na and Cl conductances were 45 and281 µ/cm2, respectively, in normal sea water. The positivevacuolar potential could be explained by these ionic conductances.On the other hand, the membrane became more sensitive to K$,if the cell was incubated for about 30 min in K-rich (100 mM)sea water. It is worth noting, however, that the membrane conductancewas lower in the K-rich sea water than in the normal sea water. (Received October 7, 1974; ) 相似文献
33.
34.
35.
Natsuki Osaka Yu kanesaki Megumi Watanabe Satoru Watanabe Taku Chibazakura Hiraku Takada Hirofumi Yoshikawa Kei Asai 《Molecular microbiology》2020,113(6):1155-1169
In bacteria, guanosine (penta)tetra-phosphate ([p]ppGpp) is essential for controlling intracellular metabolism that is needed to adapt to environmental changes, such as amino acid starvation. The (p)ppGpp0 strain of Bacillus subtilis, which lacks (p)ppGpp synthetase, is unable to form colonies on minimal medium. Here, we found suppressor mutations in the (p)ppGpp0 strain, in the purine nucleotide biosynthesis genes, prs, purF and rpoB/C, which encode RNA polymerase core enzymes. In comparing our work with prior studies of ppGpp0 suppressors, we discovered that methionine addition masks the suppression on minimal medium, especially of rpoB/C mutations. Furthermore, methionine addition increases intracellular GTP in rpoB suppressor and this effect is decreased by inhibiting GTP biosynthesis, indicating that methionine addition activated GTP biosynthesis and inhibited growth under amino acid starvation conditions in (p)ppGpp0 backgrounds. Furthermore, we propose that the increase in intracellular GTP levels induced by methionine is due to methionine derivatives that increase the activity of the de novo GTP biosynthesis enzyme, GuaB. Our study sheds light on the potential relationship between GTP homeostasis and methionine metabolism, which may be the key to adapting to environmental changes. 相似文献
36.
Xiao Wang Heng-Fu Bu Wei Zhong Akihiro Asai Zhanxiang Zhou Xiao-Di Tan 《Molecular medicine (Cambridge, Mass.)》2013,19(1):170-182
Efferocytosis is a unique phagocytic process for macrophages to remove apoptotic cells in inflammatory loci. This event is maintained by milk fat globule-EGF factor 8 (MFG-E8), but attenuated by high mobility group box 1 (HMGB1). Alcohol abuse causes injury and inflammation in multiple tissues. It alters efferocytosis, but precise molecular mechanisms for this effect remain largely unknown. Here, we showed that acute exposure of macrophages to alcohol (25 mmol/L) inhibited MFG-E8 gene expression and impaired efferocytosis. The effect was mimicked by hydrogen peroxide. Moreover, N-acetylcysteine (NAC), a potent antioxidant, blocked acute alcohol effect on inhibition of macrophage MFG-E8 gene expression and efferocytosis. In addition, recombinant MFG-E8 rescued the activity of alcohol-treated macrophages in efferocytosis. Together, the data suggest that acute alcohol exposure impairs macrophage efferocytosis via inhibition of MFG-E8 gene expression through a reactive oxygen species dependent mechanism. Alcohol has been found to suppress or exacerbate immune cell activities depending on the length of alcohol exposure. Thus, we further examined the role of chronic alcohol exposure on macrophage efferocytosis. Interestingly, treatment of macrophages with alcohol for seven days in vitro enhanced MFG-E8 gene expression and efferocytosis. However, chronic feeding of mice with alcohol caused increase in HMGB1 levels in serum. Furthermore, HMGB1 diminished efferocytosis by macrophages that were treated chronically with alcohol, suggesting that HMGB1 might attenuate the direct effect of chronic alcohol on macrophage efferocytosis in vivo. Therefore, we speculated that the balance between MFG-E8 and HMGB1 levels determines pathophysiological effects of chronic alcohol exposure on macrophage efferocytosis in vivo. 相似文献
37.
38.
Montira Yossapol Kasumi Suzuki Justice Opare Odoi Michiyo Sugiyama Masaru Usui Tetsuo Asai 《Microbiology and immunology》2020,64(10):712-718
To clarify the persistence of extended-spectrum β-lactamase (ESBL) producers, 13 plasmids from two broiler farms were analyzed. On the farm not using antimicrobials, one plasmid from Klebsiella pneumoniae isolated from a day-old chick was similar to that from Escherichia coli isolated a year later, with the deletion of two transposons. On the farm using antimicrobials, most circulating plasmids (eight out of nine) in a flock of 40-days-old chicks were identical, although one from K. pneumoniae had a deletion of a transposon carrying a class 1 integron containing aadA2 and dfrA12. Thus, ESBL plasmids persisted in the farms with or without antimicrobial agent use. 相似文献
39.
Haruyoshi Murooka Yukashi Kobayashi Toshinobu Asai 《Bioscience, biotechnology, and biochemistry》2013,77(3):135-149
It has been found that Gluconobacter liquefaciens metabolized 5-ketogluconic acid. In order to clarify metabolic pathways of this compound, the oxidation products by resting cells of this organism were investigated. Rubiginol, rubiginic, comenic, 2,5-diketogluconic, glycolic and tartronic acids were detected or identified in the reaction fluid. On the basis of these results and the data obtained by means of manometric experiments, the oxidation pathways of 5–ketogluconic acid were discussed.Oxidation pathways of 5-ketogluconie acid by resting cells of Gluconobacter liquefaciens were further investigated. Arsenite inhibited the oxidation of this compound. The amount of carbonyl compounds in the oxidation products of 5–ketogluconic acid was increased by addition of 10-3 m arsenite. Pyruvic and α-ketoglutaric acids were identified among these carbonyl compounds. Members of the tricarboxylic acid cycle were oxidized actively by resting cells or cell-free extracts of this organism. These results suggested the presence of the tricarboxylic acid cycle in the terminal oxidatjon of 5-ketogluconic acid by this organism. 相似文献
40.
Ki-Sung Kim Yuichiro Arima Taro Kitazawa Koichi Nishiyama Rieko Asai Yasunobu Uchijima Takahiro Sato Giovanni Levi Sachiko Kitanaka Takashi Igarashi Yukiko Kurihara Hiroki Kurihara 《Mechanisms of development》2013,130(11-12):553-566
Endothelin-1 (Edn1), originally identified as a vasoconstrictor peptide, is involved in the development of cranial/cardiac neural crest-derived tissues and organs. In craniofacial development, Edn1 binds to Endothelin type-A receptor (Ednra) to induce homeobox genes Dlx5/Dlx6 and determines the mandibular identity in the first pharyngeal arch. However, it remains unsolved whether this pathway is also critical for pharyngeal arch artery development to form thoracic arteries. Here, we show that the Edn1/Ednra signaling is involved in pharyngeal artery development by controlling the fate of neural crest cells through a Dlx5/Dlx6-independent mechanism. Edn1 and Ednra knock-out mice demonstrate abnormalities in pharyngeal arch artery patterning, which include persistent first and second pharyngeal arteries, resulting in additional branches from common carotid arteries. Neural crest cell labeling with Wnt1-Cre transgene and immunostaining for smooth muscle cell markers revealed that neural crest cells abnormally differentiate into smooth muscle cells at the first and second pharyngeal arteries of Ednra knock-out embryos. By contrast, Dlx5/Dlx6 knockout little affect the development of pharyngeal arch arteries and coronary arteries, the latter of which is also contributed by neural crest cells through an Edn-dependent mechanism. These findings indicate that the Edn1/Ednra signaling regulates neural crest differentiation to ensure the proper patterning of pharyngeal arch arteries, which is independent of the regional identification of the pharyngeal arches along the dorsoventral axis mediated by Dlx5/Dlx6. 相似文献