全文获取类型
收费全文 | 2379篇 |
免费 | 136篇 |
专业分类
2515篇 |
出版年
2023年 | 7篇 |
2022年 | 22篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 27篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 49篇 |
2015年 | 65篇 |
2014年 | 77篇 |
2013年 | 154篇 |
2012年 | 139篇 |
2011年 | 125篇 |
2010年 | 85篇 |
2009年 | 84篇 |
2008年 | 154篇 |
2007年 | 145篇 |
2006年 | 147篇 |
2005年 | 163篇 |
2004年 | 143篇 |
2003年 | 147篇 |
2002年 | 141篇 |
2001年 | 61篇 |
2000年 | 42篇 |
1999年 | 45篇 |
1998年 | 24篇 |
1997年 | 34篇 |
1996年 | 25篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 28篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有2515条查询结果,搜索用时 0 毫秒
1.
Masatoshi Kataoka Keizoh Kawamura Tamotsu Kondoh Yoichi Wakano Hiroshi Ishida 《FEMS microbiology letters》1993,107(1):111-114
Abstract A factor showing inhibitory activity against human gingival fibrolasts was extracted from the cytosol fraction of Actinobacillus actinomycetemcomitans Y4. The activity markedly inhibited the proliferation of human gingival fibrolasts, but had no effect on cell viability or gross morphology. No such activity was found in cytosol fractions from either Porphyromonas gingivalis 381 or Escherichia coli HB101. The extract from A. actinomycetemcomitans Y4 was then purified by anion-exchange chromatography, hydroxyapatite chromatography and gel-filtration chromatography to give a single band on SDS-PAGE with an apparent molecular mass of 65 kDa. The purification ratio was 183-fold with a recovery rate of 5% compared with the crude extract (starting material) when the activity was assessed by direct cell counts. 相似文献
2.
Masafumi Abe Naoya Nakamura Shirou Fukuhara Takamasa Hayashi Keiki Kawakami Kenkichi Kita Toshifumi Kinoshita Toyoro Ohsato Haruki Wakasa 《Virchows Archiv. B, Cell pathology including molecular pathology》1990,59(1):107-113
A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient
with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin
(SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and
antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both
the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common
ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line κ light chain genes and germ-line
T-cell receptorβ- and γ-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings
indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage. 相似文献
3.
E Kita N Katsui K Nishi M Emoto Y Yanagase S Kashiba 《Journal of general microbiology》1986,132(11):3095-3103
Mice orally infected with Campylobacter jejuni developed focal infiltrative necrotic lesions in the liver, as determined by both histology and liver function tests. The initial histopathological feature was a focal infiltrative lesion in the parenchyma and portal triads. Foci of infiltrative lesions became necrotic between days 30 and 60 post-inoculation (p.i.). During this period, portal infiltrates increased in severity. From month 4 p.i., focal areas of infiltrative necrosis in the liver parenchyma became extensive. Study of liver function demonstrated mild elevations of transaminases, alkaline phosphatase and lactic dehydrogenase, and also the presence of hypoalbuminaemia. Although histopathological changes of the liver became gradually more marked after day 30 p.i., liver functions of infected mice were most affected at 2 months p.i. The capacity of C. jejuni to induce hepatic lesions seemed to be related to that of organisms to persist in the gall bladder; there was no correlation between biliary carriage in infected mice and positive faecal culture. 相似文献
4.
Resonance Raman study of cytochrome b562-o complex, a terminal oxidase of Escherichia coli in its ferric, ferrous, and CO-ligated states 总被引:1,自引:0,他引:1
T Uno Y Nishimura M Tsuboi K Kita Y Anraku 《The Journal of biological chemistry》1985,260(11):6755-6760
Cytochrome b562-o complex, a terminal oxidase in the respiratory chain of aerobically grown Escherichia coli, has been studied by resonance Raman spectroscopy in its air-oxidized, dithionite-reduced, and reduced and CO-ligated states. In the reduced state, with a 406.7-nm excitation, there appeared 1494 and 1473 cm-1 lines, indicating that low spin and high spin components are included in the cytochrome b562-o complex. For the air-oxidized protein, resonance Raman lines were observed at 1372, 1503, and 1580 cm-1 with a 413.1-nm excitation, indicating that there is a ferric low spin heme. In addition, a weak but appreciable Raman line was observed at 1480 cm-1 assignable to a ferric high spin heme. Accordingly, it was concluded that low spin and high spin components are included in the cytochrome b562-o complex in the reduced and the air-oxidized states. In the CO-ligated state, with a defocused laser beam of 413.1 nm, two Raman bands assignable to the Fe-CO stretching mode have been observed at 489 and 523 cm-1, as a major and a minor component, respectively. When the laser beam was focused upon the sample to cause a photodissociation of CO from the heme moiety, the intensity of the major band at 489 cm-1 was reduced as expected. On the other hand, the minor band at 523 cm-1 remained still obvious. It was suggested that the cytochrome b562-o complex may have an additional anomalous site for CO that is resistant to photodissociation. 相似文献
5.
The Escherichia coli cytochrome b556 gene, cybA, is assignable as sdhC in the succinate dehydrogenase gene cluster 总被引:2,自引:0,他引:2
Hiroshi Murakami Kiyoshi Kita Hiroshi Oya Yasuhiro Anraku 《FEMS microbiology letters》1985,30(3):307-311
Abstract The cytochrome b556 -deficient mutant Escherichia coli K12 strain TK3D11 [7] could not grow with succinate as the sole carbon source, but could grow well on dl -lactate. This finding suggested that cytochrome b556 is primarily responsible for oxidative metabolism and utilization of succinate. 24 Amino acid residues at the amino-terminal of purified cytochrome b556 were determined. This sequence coincided completely with amino acid residues 4 to 27, predicted from the DNA sequence of the sdhC gene, one of the unassigned open reading frames of the sdh gene cluster recently reported by Wood et al. [16]. Based on these and other results, we concluded that cybA , the gene for cytochrome b556 , is assignable as sdhC . 相似文献
6.
W Nakamura K Komatsu M Kita T Kishida 《Comptes rendus des séances de la Société de biologie et de ses filiales》1986,180(5):601-608
Effects of preheating and injection of cis-DDP (CDDP) or interferon on tumor-induced sensitization to systemic hyperthermia (SH) was investigated in mice. LD50 of SH at 42.0 +/- 0.2 degrees C (core body temperature) was 43 min in normal mice and 8 min in mice which were i.p. transplanted with FMA3 cells at a dose of 10(5) one day before. In mice which had received the SH for 10 min one hour before, one hour after or one day before the transplantation, LD50 of the SH one day after the transplantation was 41, 35 and 22 min, respectively. An injection of CDDP given i.p. at a dose of 4 mg/kg one day after the transplantation, which was effective to kill about 99% of the tumor cells, did not change the course of thermosensitization after the transplantation. An i.p. injection of mouse interferon did not change the thermosensitivity of normal mice, but greatly suppressed the thermosensitizing effect of tumor cells when it was given one day before the transplantation. 相似文献
7.
8.
M Kita Y Ohmoto Y Hirai N Yamaguchi J Imanishi 《Comptes rendus des séances de la Société de biologie et de ses filiales》1990,184(5-6):380-384
Mycoplasma shows a variety of effects on immune system, including the activation of macrophage, the increase in T cell cytotoxicity, and the enhancement of the proliferation and maturation of B cells, etc. As it is well known that many cytokines regulate the immune system, it is interesting to examine whether or not human peripheral blood mononuclear cells (PBMC) produce interleukin (IL) in response to mycoplasmas. In the present study, human PMBC were incubated with 7 species of mycoplasmas for 48 hours, and IL-1 beta, IL-2 and IL-6 activities in the supernatants were determined by ELISA. All the species of mycoplasmas were able to induce IL-1 beta and IL-6, although IL-2 was induced only by M. pneumoniae. These results suggest that the influence of mycoplasma infection on immune system may be partly due to the interleukins induced by mycoplasmas. 相似文献
9.
Severe combined immune deficiency (scid) mice are assumed to have two types of abnormalities: one is high radiosensitivity and the other is abnormal recombination
in immunoglobulin and T-cell receptor genes. The human chromosome 8 q1.1 region has an ability to complement the scid aberrations. Moreover, the localization of the subunit DNA-dependent protein kinase [DNA-PKcs] participating in DNA double-strand break repair in the same locus was clarified. In scid mouse cells, the number of DNA-PKcs products and extent of DNA-PK activity remarkably decrease. These observations gave rise to the assumption that DNA-PKcs is the scid factor itself. In order to determine whether the DNA-PK
cs
gene is the scid gene, we isolated the mouse DNA-PK
cs
gene and investigated its chromosomal locus by fluorescence in situ hybridization (FISH). Consequently, it became clear that
the mouse DNA-PK
cs
gene existed in the centromeric region of mouse chromosome 16, determined by cross-genetic study, as a scid locus. This finding strongly suggests that mouse DNA-PK
cs
is the scid gene.
Received: 22 March 1996 相似文献
10.
Preparation of biologically active Ascaris suum mitochondrial tRNAMet with a TV-replacement loop by ligation of chemically synthesized RNA fragments. 下载免费PDF全文
T Ohtsuki G Kawai Y Watanabe K Kita K Nishikawa K Watanabe 《Nucleic acids research》1996,24(4):662-667
Ascaris suum mitochondrial tRNA Met lacking the entire T stem was prepared by enzymatic ligation of two chemically synthesized RNA fragments. The synthetic tRNA could be charged with methionine by A.suum mitochondrial extract, although the charging activity was considerably low compared with that of the native tRNA, probably due to lack of modification. Enzymatic probing of the synthetic tRNA showed a very similar digestion pattern to that of the native tRNA Met, which has already been concluded to take an L-shape-like structure [Watanabe et al. (1994) J. Biol. Chem., 269, 22902-22906]. These results suggest that the synthetic tRNA possesses almost the same conformation as the native one, irrespective of the presence or absence of modified residues. The method of preparing the bizarre tRNA used here will provide a useful tool for elucidating the tertiary structure of such tRNAs, because they can be obtained without too much difficulty in the amounts necessary for physicochemical studies such as NMR spectroscopy. 相似文献