全文获取类型
收费全文 | 2548篇 |
免费 | 150篇 |
国内免费 | 1篇 |
出版年
2023年 | 3篇 |
2021年 | 21篇 |
2020年 | 11篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 39篇 |
2016年 | 47篇 |
2015年 | 78篇 |
2014年 | 93篇 |
2013年 | 249篇 |
2012年 | 144篇 |
2011年 | 131篇 |
2010年 | 109篇 |
2009年 | 96篇 |
2008年 | 163篇 |
2007年 | 176篇 |
2006年 | 202篇 |
2005年 | 176篇 |
2004年 | 186篇 |
2003年 | 156篇 |
2002年 | 127篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 26篇 |
1998年 | 26篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 23篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有2699条查询结果,搜索用时 15 毫秒
1.
Koya Yamashiro Daisuke Sato Hideaki Onishi Kazuhiro Sugawara Sho Nakazawa Hirofumi Shimojo Kosuke Akatsuka Hiroki Nakata Atsuo Maruyama 《PloS one》2015,10(11)
Athletic training is known to induce neuroplastic alterations in specific somatosensory circuits, which are reflected by changes in somatosensory evoked potentials and event-related potentials. The aim of this study was to clarify whether specific athletic training also affects somatosensory Nogo potentials related to the inhibition of movements. The Nogo potentials were recorded at nine cortical electrode positions (Fz, Cz, Pz, F3, F4, C3, C4, P3 and P4) in 12 baseball players (baseball group) and in 12 athletes in sports, such as track and field events and swimming, that do not require response inhibition, such as batting for training or performance (sports group). The Nogo potentials and Go/Nogo reaction times (Go/Nogo RTs) were measured under a somatosensory Go/Nogo paradigm in which subjects were instructed to rapidly push a button in response to stimulus presentation. The Nogo potentials were obtained by subtracting the Go trial from the Nogo trial. The peak Nogo-N2 was significantly shorter in the baseball group than that in the sports group. In addition, the amplitude of Nogo-N2 in the frontal area was significantly larger in the baseball group than that in the sports group. There was a significant positive correlation between the latency of Nogo-N2 and Go/Nogo RT. Moreover, there were significant correlations between the Go/Nogo RT and both the amplitude of Nogo-N2 and Nogo-P3 (i.e., amplitude of the Nogo-potentials increases with shorter RT). Specific athletic training regimens may induce neuroplastic alterations in sensorimotor inhibitory processes. 相似文献
2.
Seasonal changes in several forms of nitrogen were investigatedin Coptis japonica, an evergreen rosette hemicryptophyte intemperate deciduous forest. The concentration of total nitrogenin rhizomes and roots decreased during the period of new shootgrowth from winter to spring. In the rhizomes, total solubleprotein stored by early summer decreased gradually until winter,coupled with an increase in free amino acids. Nitrogen was largelystored in free amino acids in the roots, especially during summer.The total soluble protein in current-year leaves decreased fromspring to summer and then increased during winter. The seasonalchanges in nitrogen components were coincident with the changein light-saturated photosynthetic rates recorded in a previousstudy. The ratio of total soluble protein to total nitrogendecreased from spring to summer and then increased from latesummer to winter in the current-year leaves. In contrast, chlorophyllcontent and the ratio of chlorophyll to total nitrogen werehigher in summer than in other seasons. The results indicatethat nitrogen was used in a manner that better utilizes thevery weak light in summer and the higher light intensities inother seasons. The major component of the free amino acid poolwas asparagine, in every organ throughout the season, exceptfor the senescent leaves. Since asparagine has a high N:C ratio,we suppose that the asparagine-dominated amino acid pool isadvantageous in the carbon-limited environment of the forestfloor.Copyright 1994, 1999 Academic Press Free amino acid composition, total nitrogen, total soluble protein, photosynthesis, evergreen hemicryptophyte 相似文献
3.
Sakayu Shimizu Keiko Inoue Yoshiki Tani Hideaki Yamada 《Biochemical and biophysical research communications》1981,103(4):1231-1237
The preparation of highly purified medium chain acyl-CoA synthetase (Acid: CoA ligase, AMP-forming (EC 6.2.1.2)) from the cell extracts of is described. The enzyme is inducibly formed in the cells of the microorganism, when it is grown with butyrate as a major carbon source. The purified enzyme is homogeneous on disc gel electrophoresis. Its molecular weight is approximately 142,000, and it is possibly composed of 4 identical subunits of approximately 37,000 molecular weight and has isoelectric point of 4.3. The enzyme catalyzes the stoichiometric conversion of butyrate and CoA to butyryl-CoA in the presence of ATP and Mg2+. It also activates fatty acids with carbon chain lengths of 3 to 5 well, but is inactive toward fatty acids with carbon chain lengths of more than 6. The enzyme is sulfhydryl dependent and inactivated by silver and mercury compounds. 相似文献
4.
Chromatin was prepared from the buds and cotyledons of Alaskapea seedlings. The dissociated chromosomal components in thepresence of 2 M NaCl and 5 M urea were completely fractionatedinto DNA and proteins with a Bio-Gel A50 column. The proteinswere recovered by (NH4)2SO4 and further fractionated into histonesand non-histone proteins using a Bio-Rex 70(Na+) column. Thedifference in the ratios of histones to non-histone proteinsbefore and after chromatography with the Bio-Rex 70 was lessthan 10%. The histones and non-histone proteins thus preparedshowed typical protein absorption spectra. Polyacrylamide gelelectrophoresis of histones showed that the histone compositionsin buds and cotyledon were similar, but the amount of HI histoneswas a little less in cotyledons than in buds. Unlike histones,non-histone proteins fractionated by SDS-polyacrylamide gelelectrophoresis indicated distinct differences between the twotissues. Buds had more heterogeneous non-histone proteins, atleast 13 polypeptides, than cotyledons did. On the other hand,non-histone proteins of cotyledons showed less heterogeneityand lacked proteins of high molecular weight which were foundin buds. (Received May 6, 1976; ) 相似文献
5.
A long-day duckweed, Lemna gibba G3, was found to be controlledby two lightperceiving systems; a system perceiving a prolonged,high-intensity white light and the phytochrome system, withrespect to the incorporation of radioactive uridine into RNA.When the duckweed was exposed to short or long days, the uridineincorporating activity into RNA changed diurnally reaching itshighest level at 18 hr and its lowest one at 6 hr after thebeginning of a light period. The level of maximum activity rosein proportion to an increase in the length of the light periodup to 12 hr or in light intensity up to 3000 ergs/cm2sec. Thefar-red light termination of the light period resulted in adecrease in uridine incorporation, the extent of which was constantirrespective of the length of the light period. The uridine incorporating activity changed diurnally when theduckweed was exposed to continuous light. The period lengthof the rhythm was circadian and was constant over a temperaturerange of 16° to 30°C. (Received September 1, 1975; ) 相似文献
6.
Changes of the Structure of Pea Chromatin by Aluminum 总被引:3,自引:0,他引:3
Structural changes of pea chromatin due to in vitro or in vivotreatment with Al were investigated. The absorption spectrumshowed that chromatin might be condensed and/or aggregated withAl treatment. Analysis of the melting profile showed that chromatinprepared from Al-treated roots was more stable to thermal treatment. Chromatin from Al-treated roots and chromatin treated with Alin vitro were less susceptible to DNase II digestion. When thepartially digested chromatin with DNase II was chromatographedwith Bio-Gel A5m, the digestibility of chromatin obtained fromAl-treated roots was less than that from control roots. Furthermore,most of the Al was associated with a chromatin fraction whichwas minimally digested with DNase II and of large size afterthe gel chromatography. The results suggested that Al absorbedby pea roots is somehow related to alteration of the chromatinstructure, i.e. its condensation and/or aggregation. The conclusionreached was that Al toxicity results from disturbance of thenuclear activity. (Received July 22, 1987; Accepted December 7, 1987) 相似文献
7.
Hideaki Naoe Tatsuyuki Chiyoda Jo Ishizawa Kenta Masuda Hideyuki Saya Shinji Kuninaka 《Biochemical and biophysical research communications》2013,430(2):757-762
Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation. 相似文献
8.
Hideaki Matsushita Masanori Hijioka Akinori Hisatsune Yoichiro Isohama Shigeto Iwamoto Hiroaki Terasawa Hiroshi Katsuki 《PloS one》2013,8(7)
Intracerebral hemorrhage (ICH) is featured by poor prognosis such as high mortality rate and severe neurological dysfunction. In humans, several valuables including hematoma volume and ventricular expansion of hemorrhage are known to correlate with the extent of mortality and neurological dysfunction. However, relationship between hematoma conditions and the severity of symptoms in animal ICH models has not been clarified. Here we addressed this issue by using 7-tesla magnetic resonance imaging (MRI) on collagenase-induced ICH model in mice. We found that the mortality rate and the performance in behavioral tests did not correlate well with the volume of hematoma. In contrast, when hemorrhage invaded the internal capsule, mice exhibited high mortality and showed poor sensorimotor performance. High mortality rate and poor performance in behavioral tests were also observed when hemorrhage invaded the lateral ventricle, although worsened symptoms associated with ventricular hemorrhage were apparent only during early phase of the disease. These results clearly indicate that invasion of the internal capsule or the lateral ventricle by hematoma is a critical determinant of poor prognosis in experimental ICH model in mice as well as in human ICH patients. MRI assessment may be a powerful tool to refine investigations of pathogenic mechanisms and evaluations of drug effects in animal models of ICH. 相似文献
9.
Katsura Kogure Noriyoshi Sueda Kunio Nakagawa Hideaki Fukawa 《Bioscience, biotechnology, and biochemistry》2013,77(2):435-436
The relationships between dietary levels of the essential amino acids and hepatic polysome profiles of rats were investigated with special attention to the amino acid requirement pattern for the maximum rat growth as determined by other investigators. The basal diet contained a 7% essential amino acid mixture and a 3% non-essential amino acid mixture, with appropriate amounts of other nutrients. Rats were fed test diet for 5 hours and then the polysome profile was determined. The amounts of essential amino acids needed for maximum aggregation of polysome were low for methionine-cystine, leucine and tryptophan as compared with requirements for maximum growth. But in other essential amino acids, the amounts were in almost the same range as those reported for maximum growth by others. The differences between the amino acid requirement patterns for maximum aggregation of hepatic ribosomes and for maximum growth of rats might be due to a difference in amino acid requirements of the liver and whole body. Therefore, the hepatic polysome profile might be used to measure the effect of amino acid supplementation on dietary proteins. The requirement pattern of essential amino acids in other organs may be studied by polysome profile determination. 相似文献
10.
Nobuya Katagiri Hideaki Kokufuda Masashi Makino Robert Vince Chikara Kaneko 《Nucleosides, nucleotides & nucleic acids》2013,32(1-3):81-89
Abstract The deamination of cyclaradine corresponding to a carbocyclic analogue of ara-A having anti-HSV activity by adenosine deaminase was examined under various pressure. The deamination of (+)- and (±)-cyclaradine was remarkably facilitated by high pressure, and the rate was increased with increasing of pressure. However, (-)-cyclaradine was not deaminated even under high pressure. 相似文献