全文获取类型
收费全文 | 1582篇 |
免费 | 78篇 |
国内免费 | 2篇 |
专业分类
1662篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 24篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 18篇 |
2017年 | 25篇 |
2016年 | 24篇 |
2015年 | 50篇 |
2014年 | 52篇 |
2013年 | 109篇 |
2012年 | 93篇 |
2011年 | 102篇 |
2010年 | 58篇 |
2009年 | 48篇 |
2008年 | 89篇 |
2007年 | 74篇 |
2006年 | 96篇 |
2005年 | 75篇 |
2004年 | 97篇 |
2003年 | 105篇 |
2002年 | 94篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 19篇 |
1998年 | 23篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 16篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1969年 | 2篇 |
排序方式: 共有1662条查询结果,搜索用时 15 毫秒
51.
Lamontagne B Ghazal G Lebars I Yoshizawa S Fourmy D Elela SA 《Journal of molecular biology》2003,327(5):985-1000
Yeast Rnt1p is a member of the double-stranded RNA (dsRNA) specific RNase III family of endoribonucleases involved in RNA processing and RNA interference (RNAi). Unlike other RNase III enzymes, which recognize a variety of RNA duplexes, Rnt1p cleaves specifically RNA stems capped with the conserved AGNN tetraloop. This unusual substrate specificity challenges the established dogma for substrate selection by RNase III and questions the dsRNA contribution to recognition by Rnt1p. Here we show that the dsRNA sequence adjacent to the tetraloop regulates Rnt1p cleavage by interfering with RNA binding. In context, sequences surrounding the cleavage site directly influence the cleavage efficiency. Introduction of sequences that stabilize the RNA helix enhanced binding while reducing the turnover rate indicating that, unlike the tetraloop, Rnt1p binding to the dsRNA helix may become rate-limiting. These results suggest that Rnt1p activity is strictly regulated by a combination of primary and tertiary structural elements allowing a substrate-specific binding and cleavage efficiency. 相似文献
52.
Yuri Hasegawa Hirotaka Uosaki Shuji Adachi Ryuichi Matsuno 《Biotechnology letters》1996,18(4):367-372
Summary Stereoselective oxidation of (S)-isomer of rac-1-phenylethanol (1-PA) by the yeast Pachysolen tannophilus IFO 1007 immobilized into calcium-alginate gels was investigated to produce (R)-isomer. Continuous production of (R)-isomer was accomplished for more than 80 h with an enantiomeric excess of > 90% using a bioreactor of a fluidized-bed type. 相似文献
53.
Emoto M Miyamoto M Emoto Y Yoshizawa I Brinkmann V van Rooijen N Kaufmann SH 《Journal of immunology (Baltimore, Md. : 1950)》2003,171(8):3970-3976
LFA-1 (CD11a/CD18) plays a key role in various inflammatory responses. Here we show that the acquired immune response to Listeria monocytogenes is highly biased toward type 1 in the absence of LFA-1. At the early stage of listeriosis, numbers of IFN-gamma producers in the liver and spleen of LFA-1(-/-) mice were markedly increased compared with heterozygous littermates and Valpha14(+)NKT cell-deficient mice, and NK cells were major IFN-gamma producers. Numbers of IL-12 producers were also markedly elevated in LFA-1(-/-) mice compared with heterozygous littermates, and endogenous IL-12 neutralization impaired IFN-gamma production by NK cells. Granulocyte depletion diminished numbers of IL-12 producers and IFN-gamma-secreting NK cells in the liver of LFA-1(-/-) mice. Granulocytes from the liver of L. monocytogenes-infected LFA-1(-/-) mice were potent IL-12 producers. Thus, in the absence of LFA-1, granulocytes are a major source of IL-12 at the early stage of listeriosis. We assume that highly biased type 1 immune responses in LFA-1(-/-) mice are caused by increased levels of IL-12 from granulocytes and that granulocytes play a major role in IFN-gamma secretion by NK cells. In conclusion, LFA-1 regulates type 1 immune responses by controlling prompt infiltration of IL-12-producing granulocytes into sites of inflammation. 相似文献
54.
Summary Calli were induced from the crown of seedlings or lateral bud of young spears of Asparagus officinalis L. on Linsmaier and Skoog's (LS) solid-medium supplemented with 5 M 2,4-dichlorophenoxyacetic acid (2,4-D). Embryogenic callus was selected from induced calli and proliferated in LS liquid medium supplemented with 5 M 2,4-D. Non-vitrified somatic embryos were formed and efficiently developed into club-shaped embryos in LS hormone-free medium with 1 % gelrite in a culture vessel capped with an aseptic ventilative filter. Non-vitrified club-shaped embryos developed into normal plants when transferred to half-strength LS medium without hormones, and 0.8 % agar. Carbon dioxide concentration and moisture content inside the culture vessels were measured, and their effect on embryo development is discussed. 相似文献
55.
Application of heat-induced antigen retrieval to aldehyde-fixed fresh frozen sections. 总被引:1,自引:0,他引:1
Shuji Yamashita Yasunori Okada 《The journal of histochemistry and cytochemistry》2005,53(11):1421-1432
We applied the heat-induced antigen retrieval (HIAR) to aldehyde-fixed fresh frozen sections based on a new approach (i.e., a rapid and complete immobilization of antigen followed by heating). Frozen sections were fixed with 10% formalin in 0.1 M cacodylate buffer (pH 7.4) containing 25 mM CaCl(2) for 30 min, or with 0.5% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) for 1 min at room temperature, and then autoclaved in 20 mM Tris-HCl buffer (pH 9.0) for 10 min at 120 C. Both fixatives yielded good tissue structure after autoclaving. In the sections fixed with formalin containing CaCl(2), 20 of 22 antigens located in the nucleus, cytoplasm, membranes, and extracellular matrix greatly recovered their antigenicity after autoclaving; only two antigens exhibited stronger immunoreaction in acetone-fixed fresh frozen sections than these sections. Heating also retrieved the immunoreactivity of at least 14 antigens in the sections fixed with glutaraldehyde. We used the similar procedures to localize ligand-free estrogen receptor alpha (ERalpha) and glucocorticoid receptors (GR). Mouse uterine cells exhibited almost the same nuclear ERalpha immunostaining regardless of the hormonal status in glutaraldehyde-fixed fresh frozen sections and unliganded GR was localized mainly in the nucleus of mouse hepatocytes in fresh frozen sections fixed with 20% formalin containing 50 or 75 mM CaCl(2) at 40 C, after autoclaving. These results demonstrate that HIAR is useful for the immunohistochemistry of many antigens in aldehyde-fixed fresh frozen sections. 相似文献
56.
Hidehito Urata Shuji Ogawa Shun-ichi Wada 《Bioorganic & medicinal chemistry letters》2013,23(10):2909-2911
The effects of substituting l-deoxynucleotide for d-deoxynucleotide at duplex termini were evaluated and the terminal substitutions were found to show much less effects on duplex destabilization and to show a similar tendency in base pairing selectivity, compared with internal chiral substitutions. 相似文献
57.
Akiharu Kubo Aiko Shiohama Takashi Sasaki Kazuhiko Nakabayashi Hiroshi Kawasaki Toru Atsugi Showbu Sato Atsushi Shimizu Shuji Mikami Hideaki Tanizaki Masaki Uchiyama Tatsuo Maeda Taisuke Ito Jun-ichi Sakabe Toshio Heike Torayuki Okuyama Rika Kosaki Kenjiro Kosaki Jun Kudoh Kenichiro Hata Akihiro Umezawa Yoshiki Tokura Akira Ishiko Hironori Niizeki Kenji Kabashima Yoshihiko Mitsuhashi Masayuki Amagai 《American journal of human genetics》2013,93(5):945-956
“Nagashima-type” palmoplantar keratosis (NPPK) is an autosomal recessive nonsyndromic diffuse palmoplantar keratosis characterized by well-demarcated diffuse hyperkeratosis with redness, expanding on to the dorsal surfaces of the palms and feet and the Achilles tendon area. Hyperkeratosis in NPPK is mild and nonprogressive, differentiating NPPK clinically from Mal de Meleda. We performed whole-exome and/or Sanger sequencing analyses of 13 unrelated NPPK individuals and identified biallelic putative loss-of-function mutations in SERPINB7, which encodes a cytoplasmic member of the serine protease inhibitor superfamily. We identified a major causative mutation of c.796C>T (p.Arg266∗) as a founder mutation in Japanese and Chinese populations. SERPINB7 was specifically present in the cytoplasm of the stratum granulosum and the stratum corneum (SC) of the epidermis. All of the identified mutants are predicted to cause premature termination upstream of the reactive site, which inhibits the proteases, suggesting a complete loss of the protease inhibitory activity of SERPINB7 in NPPK skin. On exposure of NPPK lesional skin to water, we observed a whitish spongy change in the SC, suggesting enhanced water permeation into the SC due to overactivation of proteases and a resultant loss of integrity of the SC structure. These findings provide an important framework for developing pathogenesis-based therapies for NPPK. 相似文献
58.
59.
Mori S Shinohata R Renbutsu M Takahashi HK Fang YI Yamaoka K Okamoto M Yamamoto I Nishibori M 《Cell and tissue research》2003,312(3):353-359
Vascular smooth muscle cell (SMC) hyperplasia is known to be an important component in the pathogenesis of arteriosclerosis and restenosis. Although heparin has been well recognized as the representative molecule suppressing SMC growth in vitro, attempts to use heparin as a therapeutic anti-restenosis drug have not favorably influenced the angiographic or clinical outcome after angioplasty in some clinical trials. In this study, we have examined the effect of histidine-rich glycoprotein (HRG), a relatively abundant serum glycoprotein (~100 micrograms/ml in human serum), on the growth inhibition of cultured vascular SMC by heparin. Vascular SMC growth was significantly inhibited by heparin, giving nearly 85% inhibition with 100 micrograms/ml heparin. HRG reversed heparin-induced SMC growth inhibition in a dose dependent manner; 75% restoration of cell growth was observed when 100 micrograms/ml of HRG was co-added with 100 micrograms/ml heparin. Interestingly, micromolar concentrations of the zinc ion (0-10 microM), compatible with concentrations released from activated platelets, were found to enhance the restorative action of HRG. Western blot experiment demonstrated no significant amounts of the HRG moiety in fetal bovine serum, eliminating the possible contribution of contaminant HRG from culture media. These findings indicate that HRG, in combination with the zinc ion, plays a role in modulating the SMC growth response in pathophysiological states and explain the lack of success of heparin as a therapeutic anti-restenosis drug in clinical trials. 相似文献
60.
Y Fukada K Kokame T Okano Y Shichida T Yoshizawa J H McDowell P A Hargrave K Palczewski 《Biochemistry》1990,29(43):10102-10106
The amino acid sequence has been determined for the carboxyl-terminal 41 amino acids of chicken red-sensitive cone pigment, iodopsin. This sequence is distinct from but structurally homologous to that of other visual pigments. It contains a region rich in the hydroxy amino acids serine and threonine. In the related rod cell visual pigment, rhodopsin, such serines and threonines have previously been identified as sites for phosphorylation by rhodopsin kinase. Phosphorylation of photolyzed rhodopsin serves to terminate its ability to function in visual transduction as an activator of G-protein. We have purified and reconstituted both chicken rhodopsin and chicken iodopsin and shown them to be phosphorylated by bovine rhodopsin kinase. Chicken iodopsin has a Km and Vmax similar to but distinguishably different from that for bovine rhodopsin. These results, in conjunction with other data, suggest that visual pigments in cone cells, upon absorption of light, undergo functional processes similar to those of the visual pigments in rod cells. 相似文献