全文获取类型
收费全文 | 3400篇 |
免费 | 203篇 |
国内免费 | 4篇 |
出版年
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 29篇 |
2018年 | 34篇 |
2017年 | 45篇 |
2016年 | 60篇 |
2015年 | 87篇 |
2014年 | 120篇 |
2013年 | 274篇 |
2012年 | 189篇 |
2011年 | 182篇 |
2010年 | 114篇 |
2009年 | 134篇 |
2008年 | 208篇 |
2007年 | 183篇 |
2006年 | 196篇 |
2005年 | 176篇 |
2004年 | 191篇 |
2003年 | 188篇 |
2002年 | 186篇 |
2001年 | 62篇 |
2000年 | 66篇 |
1999年 | 70篇 |
1998年 | 53篇 |
1997年 | 37篇 |
1996年 | 34篇 |
1995年 | 47篇 |
1994年 | 36篇 |
1993年 | 47篇 |
1992年 | 41篇 |
1991年 | 48篇 |
1990年 | 34篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 24篇 |
1986年 | 28篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 15篇 |
1973年 | 10篇 |
1970年 | 15篇 |
排序方式: 共有3607条查询结果,搜索用时 15 毫秒
1.
Takemi Yoshida Akio Uchida Toshinori Yamamoto Yukio Kuroiwa 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,677(2):280-286
The activities of mitochondrial type A and B monoamine oxidase were determined in the liver of rats fed a diet containing 2-acetylaminofluorene (AAF). Three days after the initiation of AAF-feeding, there was a significant decrease of type B monoamine oxidase activity without affect on type A enzyme. The decreased activity of type B monoamine oxidase, which reached a minimum after three weeks, was sustained for as long as AAF-feeding was continued. Sex-related difference in response to AAF was seen in the rat with respect to the onset and the intensity of the decreased type B monoamine oxidase activity, male rats being more sensitive to the carcinogen than female rats. In contrast to the in vivo effect, AAF showed a potent inhibitory effect on type A monoamine oxidase, rather than on type B enzyme, when added in vitro. The pI50 values were estimated to be 7.5 against type A monoamine oxidase and 4.1 against type B enzyme, respectively. The in vitro inhibition of both types of monoamine oxidase by AAF was competitive. The Ki values for AAF were calculated to be 9.51 · 10?9 M for type A monoamine oxidase and 1.30 · 10?5 M for type B enzyme, respectively. In accordance with the potent inhibitory effect of AAF on type A monoamine oxidase in vitro, a single administration of the carcinogen, at a dose of 50 mg/kg, resulted in a marked and temporal decrease of the enzyme activity in the mitochondria of male rat liver. Recovery of the decreased type B monoamine oxidase activity was slow, and the enzyme activity did not return to control levels, even if rats were fed the basal diet for 2 or 4 weeks after the cessation of AAF-feeding. 相似文献
2.
3.
Shigeo Koyasu Makoto Asada Akio Fukuda Yoshimi Okada 《Journal of molecular biology》1981,153(2):471-475
The mode of polymerization of two species of flagellins, flagellin A and flagellin B, in polar flagella of Caulobacter crescentus was examined. By immunological staining we found that 1 to 1.2 μm of the portion of the flagellar filament proximal to the cell was composed of flagellin B, whereas about 5 μm of the distal portion was composed of flagellin A. This result, together with the previous observation that a flagellin B-less mutant cannot form normal flagella but instead forms stubs in spite of their high level of flagellin A synthesis, indicates that flagellin B is very important for the formation of complete flagella and/or for the initiation of filament formation from the hook. 相似文献
4.
Satoko Iwahori Daisuke Kohmon Junya Kobayashi Yuhei Tani Takashi Yugawa Kenshi Komatsu 《Cell cycle (Georgetown, Tex.)》2014,13(3):471-481
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability. 相似文献
5.
We investigated the effects of near-infrared irradiation on the photoconversion of Chenopodium album water-soluble chlorophyll-binding protein (CaWSCP) in the presence of sodium hydrosulfite and found a further photoconversion from CP742 to CP763, a novel form of CaWSCP. Interestingly, one-third of the absorption peak at 668 nm was recovered in CP763, but re-irradiation under oxidative conditions eliminated the photo convertibility of CaWSCP. 相似文献
6.
7.
Akio Matsuura Takako Nagayama Takayasu Kitagawa 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1993,617(2)
An automated high-performance liquid chromatographic method for the determination of the diuretic drug furosemide has been established. Dog plasma was injected directly into a two-column system with a BSA—ODS (ODS column coated with bovine serum albumin) precolumn and a C18 analytical column for the separation of furosemide. The two columns were automatically switched. Furosemide remained trapped on the precolumn while proteins were eluted to waste. After column switching, furosemide was washed onto the analytical column and analysed without interference. The greatest advantage of the method is its easy performance without manual sample preparation; it requires no extraction or deproteinization. The method allows determination of 0.1–10 μg/ml of furosemide with accuracy and precision comparable with previously reported values. The coefficients of variation obtained from replicate measurements of 1 μg/ml and 5 μg/ml samples were 1.65% and 2.40%, respectively. This method was used to measure the plasma levels of furosemide in beagle dogs to whom the drugs was administered, as a reference, in a toxicological study. 相似文献
8.
Recombinant human serum albumin (rHSA) incorporating 2-[8-[N-(2-methylimidazolyl)]octanoyloxymethyl]-5,10,15,20-tetrakis(alpha,alpha,alpha,alpha-o-pivalamido)phenylporphinatoiron(II)s (Fe(II)Ps) [rHSA-Fe(II)P] is a synthetic hemoprotein which can bind and release O(2) reversibly under physiological conditions (saline solution [NaCl]: 150 mM, pH 7.3) as do hemoglobin and myoglobin. However, the central ferrous ions of Fe(II)Ps are slowly oxidized to O(2)-inactive ferric forms. Based on the UV-vis. absorption spectroscopy, the majority of the autooxidized Fe(III)Ps in albumin are determined to be six-coordinate high-spin complexes with a proximal imidazole and a chloride anion, which show ligand-to-metal charge transfer (LMCT) absorption at 330 nm. Interestingly, photoirradiation of this LMCT band under an argon atmosphere led to reduction of the central ferric iron of Fe(III)P, allowing the revival of the O(2)-binding ability. The ratio of the photoreduction reached a maximum of 83%, which is probably due to the partial dissociation of the axial imidazole. The same photoirradiation under a CO atmosphere provides the corresponding carbonyl rHSA-Fe(II)P. Laser flash photolysis experiments revealed that the reduction was completed within 100 ns. The quantum yields (Phi) of these photoreductions were approximately 0.01. 相似文献
9.
M Nakamura M Oda K Kaneko Y Yonei N Tsukada H Komatsu M Tsugu M Tsuchiya 《Peptides》1987,8(2):391-398
The location of 125I-iodotyrosyl gastrin I binding sites in rat gastric mucosa was studied. Peptide specificity was demonstrated by competitive binding studies through the addition of a large dose of cold human gastrin I or cholecystokinin-octapeptide. Autoradiography of the stomach tissue was carried out by freeze-drying, embedding in Epon, wet-sectioning with ethylene glycol, and dry-mounting the emulsion film by means of the wire-loop method to prevent loss of the labeled substance. Specific binding sites for gastrin were found on parietal and chief cells, whereas few binding sites were seen on the surface mucous or mucous neck cells. Binding sites on the parietal cells were dispersed in the cytoplasm, while those on the chief cells were found near the basal plasma membrane. 相似文献
10.
Hydrogen peroxide was formed in isolated cell walls from Marchantiapolymorpha L. in the presence of MnCl2 by either NADH or NADPHoxidation. This reaction was stimulated by phenols such as 2,4-dichlorophenolor p-coumarate, suggesting a reaction similar to that proposedfor the last step of lignification in higher plant cells, althoughbryophytes have been reported to be devoid of lignin. (Received June 16, 1987; Accepted March 3, 1987) 相似文献