全文获取类型
收费全文 | 2039篇 |
免费 | 84篇 |
国内免费 | 2篇 |
专业分类
2125篇 |
出版年
2022年 | 9篇 |
2021年 | 26篇 |
2020年 | 15篇 |
2019年 | 23篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 36篇 |
2015年 | 57篇 |
2014年 | 70篇 |
2013年 | 114篇 |
2012年 | 105篇 |
2011年 | 138篇 |
2010年 | 94篇 |
2009年 | 73篇 |
2008年 | 144篇 |
2007年 | 134篇 |
2006年 | 136篇 |
2005年 | 121篇 |
2004年 | 129篇 |
2003年 | 121篇 |
2002年 | 113篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 27篇 |
1998年 | 31篇 |
1997年 | 36篇 |
1996年 | 22篇 |
1995年 | 33篇 |
1994年 | 15篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1980年 | 7篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有2125条查询结果,搜索用时 15 毫秒
951.
Miyakoshi Junji Tsukada Toshihiko Tachiiri Seiji Bandoh Shuji Yamaguchi Ken Takebe Hiraku 《Molecular and cellular biochemistry》1998,181(1-2):191-195
Enhanced expression of neuron derived orphan receptor (NOR-1) gene was observed by exposure of Chinese hamster ovary K1 (CHO-K1) cells to an extremely low frequency magnetic field (ELFMF) of 50 Hz at 400 mT, but not at 5 mT. The enhanced expression, reaching the maximum at 6 h, was transient and reduced to the control level after exposure to 400 mT ELFMF for 24 h. The NOR-1 expression induced by treatment with forskolin and TPA was further enhanced by the simultaneous treatment with 400 mT ELFMF, in which the maximum response was at 3 h. The NOR-1 expression by these treatments was induced more earlier than that by 400 mT ELFMF alone. When cells were treated with an inhibitor of the protein kinase C (calphostin C or crocetin) and Ca2+ entry blockers (nifedipin and dantrolen) during the 400 mT ELFMF exposure, the enhanced NOR-1 expression was not observed. Exposure of CHO-K1 cells to the high-density 400 mT ELFMF may affect the signal transduction in the cells, resulting in the enhanced NOR-1 gene expression. 相似文献
952.
Kappei Kobayashi Seiji Tsuge Hitoshi Nakayashiki Kazuyuki Mise Iwao Furusawa 《Microbiology and immunology》1998,42(4):329-334
Studies have indicated that cauliflower mosaic virus (CaMV) gene expression is mediated by the translation of polycistronic 35S pregenomic RNA, but the involvement of some minor subgenomic RNA species is also suspected. We examined the involvement of the 35S promoter in the expression of CaMV open reading frames (ORFs) I and IV using both 35S RNA-driven and promoter-less ORF I- and ORF IV-β-glucuronidase (GUS) fusion constructs. In addition to the 35S promoter-dependent expression of both ORF I- and IV-GUS fusions, we detected the 35S promoter-independent expression of both fusion genes via subgenomic mRNAs, which were detected by Northern blotting in the protoplasts transfected with the 35S promoter-driven constructs as well as in those transfected with the promoter-less constructs. These results suggest the involvement of subgenomic RNAs in the expression of CaMV ORFs I and IV, and the operation of a dual strategy in the expression of two viral genes. 相似文献
953.
954.
Amer Ali Abd El-Hafeez Takashi Fujimura Rikiya Kamei Noriko Hirakawa Kenji Baba Kazuhisa Ono Seiji Kawamoto 《Cytotechnology》2018,70(3):899-912
Perilla frutescens is an Asian dietary herb consumed as an essential seasoning in Japanese cuisine as well as used for a Chinese medicine. Here, we report that a newly found methoxyflavanone derivative from P. frutescens (Perilla-derived methoxyflavanone, PDMF; 8-hydroxy-5,7-dimethoxyflavanone) shows carcinostatic activity on human lung adenocarcinoma, A549. We found that treatment with PDMF significantly inhibited cell proliferation and decreased viability through induction of G2/M cell cycle arrest and apoptosis. The PDMF stimulation induces phosphorylation of tumor suppressor p53 on Ser15, and increases its protein amount in conjunction with up-regulation of downstream cyclin-dependent kinase inhibitor p21Cip1/Waf1 and proapoptotic caspases, caspase-9 and caspase-3. We also found that small interfering RNA knockdown of p53 completely abolished the PDMF-induced G2/M cell cycle arrest, and substantially abrogated its proapoptotic potency. These results suggest that PDMF represents a useful tumor-preventive phytochemical that triggers p53-driven G2/M cell cycle arrest and apoptosis. 相似文献
955.
Akira Kaieda Masashi Takahashi Takafumi Takai Masayuki Goto Takahiro Miyazaki Yuri Hori Satoko Unno Tomohiro Kawamoto Toshimasa Tanaka Sachiko Itono Terufumi Takagi Teruki Hamada Mikio Shirasaki Kengo Okada Gyorgy Snell Ken Bragstad Bi-Ching Sang Osamu Uchikawa Seiji Miwatashi 《Bioorganic & medicinal chemistry》2018,26(3):647-660
We identified novel potent inhibitors of p38 MAP kinase using structure-based design strategy. X-ray crystallography showed that when p38 MAP kinase is complexed with TAK-715 (1) in a co-crystal structure, Phe169 adopts two conformations, where one interacts with 1 and the other shows no interaction with 1. Our structure-based design strategy shows that these two conformations converge into one via enhanced protein-ligand hydrophobic interactions. According to the strategy, we focused on scaffold transformation to identify imidazo[1,2-b]pyridazine derivatives as potent inhibitors of p38 MAP kinase. Among the herein described and evaluated compounds, N-oxide 16 exhibited potent inhibition of p38 MAP kinase and LPS-induced TNF-α production in human monocytic THP-1 cells, and significant in vivo efficacy in rat collagen-induced arthritis models. In this article, we report the discovery of potent, selective and orally bioavailable imidazo[1,2-b]pyridazine-based p38 MAP kinase inhibitors with pyridine N-oxide group. 相似文献
956.
Takehara Ikki Fujii Tsubasa Tanimoto Yuuki Kato Dai-Ichiro Takeo Masahiro Negoro Seiji 《Applied microbiology and biotechnology》2018,102(2):815-815
Applied Microbiology and Biotechnology - The original publication of this paper contains mistakes for Tables 1 and 2 legends as well as the sublabels in Figs. 2, 4, 5, 6, and 7. 相似文献
957.
958.
A new indole-3-acetic acid (IAA) metabolite in the root of Viciafaba L. cv. Chukyo was identified as 3-hydroxy-2-indolone-3-acetylasparticacid, with the simpler name of dioxindole-3-acetylaspartic acid,by comparison with the authentic sample. Formation of dioxindole-3-aceticacid conjugates seems to be a major route of IAA metabolismin Vicia roots. (Received October 22, 1985; Accepted January 7, 1986) 相似文献
959.
Osamu Hiroshima Hideya Hayashi Seiji Ito Osamu Hayaishi 《Prostaglandins & other lipid mediators》1986,32(1)
A solid-phase enzyme immunoassay for prostaglandin D2 (PGD2) was developed in which PGD2 was labeled with horseradish peroxidase. After competitive binding to the immobilized antibody between enzyme-labelled and free PGD2, the activity of the enzyme bound to the antibody was assayed fluorometrically using 3-(p-hydroxyphenyl)- propionic acid and hydrogen peroxide as substrates. The procedure allowed determinations of 3 – 100 pg for PGD2. The IC50 value for PGD2 in the solid-phase enzyme immunoassay was about 25 pg and the sensitivity was improved about 10 times compared to those in radioimmunoassay and in solution-phase enzyme immunoassay. The solid-phase enyzme immunoassay was applied to the measurement of PGD2 content in rat brain and thereby an octadecylsilyl silica cartridge and a reversed-phase HPLC were sequentially used for sample preparations. Heads were immediately frozen in liquid nitrogen after decapitation to avoid a postmortem formation of PGD2. PGD2 contents measured by solid-phase enzyme immunoassay correlated well with the values obtained by radioimmunoassay (r = 0.966) after raising its contents by intravenous administration of PGD2. The
level of PGD2 in rat brain was extremely low but determined to be 0.11 ± 0.03 ng/g tissue (mean ± S.E.M.) with this enzyme immunoassay. The result was equal to the value extrapolated to zero time from the postmortem change. 相似文献
960.
Characteristic Amino Acid Sequences of Chloroplast and Cytosol Isozymes of CuZn-Superoxide Dismutase in Spinach, Rice and Horsetail 总被引:6,自引:0,他引:6
Two isozymes of CuZn-superoxide dismutase (SOD) were purifiedfrom spinach. One (CuZn-SOD II) was localized in chloroplastsand had the same properties as the enzyme previously reported[Asada et al. (1973) Eur. J. Biochem. 36: 257266]. Theother isozyme (CuZn-SOD I) was predominantly expressed in seedsand in etiolated seedlings of spinach, but was localized inthe cytosol of the leaves as a minor enzyme. The isozymes havesimilar molecular weights, subunit structures, and metal contents;but their amino acid compositions, absorption spectra, CD spectraand sensitivities to hydrogen peroxide are different. The amino acid sequences of 50 amino-terminal residues of thechloroplast and cytosol isozymes of CuZn-SOD from spinach, riceand horsetail were determined and compared with those of CuZn-SODsfrom other plants. The sequences can be divided into chloroplastand cytosol types, and characteristic sequences can be identifiedin accordance with the observations that the two types of CuZn-SODisozymes from green algae, ferns and angiosperms can be distinguishedimmunologically from each other. Differences in amino acid sequencesamong the cytosol enzymes are greater than those among the chloroplastenzymes, indicating that the rate of mutation of the cytosolCuZn-SOD is higher than that of the chloroplast CuZn-SOD. Theseresults provide further evidence that the divergence of thetwo types of isozyme of CuZn-SOD occurred at a very early stageof its acquisition, and that each type of CuZn-SOD has evolvedindependently. (Received September 1, 1989; Accepted November 6, 1989) 相似文献