全文获取类型
收费全文 | 836篇 |
免费 | 42篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 7篇 |
2016年 | 26篇 |
2015年 | 40篇 |
2014年 | 44篇 |
2013年 | 39篇 |
2012年 | 66篇 |
2011年 | 71篇 |
2010年 | 33篇 |
2009年 | 29篇 |
2008年 | 44篇 |
2007年 | 48篇 |
2006年 | 42篇 |
2005年 | 57篇 |
2004年 | 45篇 |
2003年 | 50篇 |
2002年 | 47篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有878条查询结果,搜索用时 140 毫秒
61.
When α-d-GlcNAc-OC6H4NO2
-p and β-d-(6-sulfo)-GlcNAc-OC6H4NO2-p (2) were used as substrates, β-N-acetylhexosaminidase from Aspergillus oryzae transferred the β-d-(6-sulfo)-GlcNAc(unit from 2 to α-d-GlcNAc-OC6H4NO2
-p to afford β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-GlcNAc-OC6H4NO2-p (3) in a yield of 94% based on the amount of donor, 2, added. β-d-(6-sulfo)-GlcNAc-(1→4)-α-d-Glc-OC6H4NO2-p (4) was obtained with α-d-Glc-OC6H4NO2
-p as acceptor in a similar manner. With a reaction mixture of 2 and β-d-GlcNAc-OC6H4NO2-p (1) in a molar ratio of 6:1, the enzyme mediated the transfer of β-d-GlcNAc from 1 to 2, affording disaccharide β-d-GlcNAc-(1→4)-β-(6-sulfo)-d-GlcNAc-OC6H4NO2-p (5) in a yield of 13% based on the amount of 1 added. 相似文献
62.
Long-distance signals generated in shoots are thought to be associated with the regulation of iron uptake from roots; however,
the signaling mechanism is still unknown. To elucidate whether the signal regulates iron uptake genes in roots positively
or negatively, we analyzed the expressions of two representative iron uptake genes: NtIRT1 and NtFRO1 in tobacco (Nicotiana tabacum L.) roots, after shoots were manipulated in vitro. When iron-deficient leaves were treated with Fe(II)-EDTA, the expressions
of both genes were significantly reduced; nevertheless iron concentration in the roots maintained a similar level to that
in roots grown under iron-deficient conditions. Next, all leaves from tobacco plants grown under the iron-deficient condition
were excised. The expression of two genes were quickly reduced below half within 2 h after the leaf excision and gradually
disappeared by the end of a 24-h period. The NtIRT1 expression was compared among the plants whose leaves were cut off in various patterns. The expression increased in proportion
to the dry weight of iron-deficient leaves, although no relation was observed between the gene expression and the position
of excised leaves. Interestingly, the NtIRT1 expression in hairy roots increased under the iron-deficient condition, suggesting that roots also have the signaling mechanism
of iron status as well as shoots. Taken together, these results indicate that the long-distance signal generated in iron-deficient
tissues including roots is a major factor in positive regulation of the expression of NtIRT1 and NtFRO1 in roots, and that the strength of the signal depends on the size of plants. 相似文献
63.
Ode H Matsuyama S Hata M Neya S Kakizawa J Sugiura W Hoshino T 《Journal of molecular biology》2007,370(3):598-607
A prominent characteristic of human immunodeficiency virus type 1 (HIV-1) is its high genetic variability, which generates diversity of the virus and often causes a serious problem of the emergence of drug-resistant mutants. Subtype B HIV-1 is dominant in advanced countries, and the mortality rate due to subtype B HIV-1 has been decreased during the past decade. In contrast, the number of patients with non-subtype B viruses is still increasing in developing countries. One of the reasons for the prevalence of non-subtype B viruses is lack of information about the biological and therapeutic differences between subtype B and non-subtype B viruses. M36I is the most frequently observed polymorphism in non-subtype B HIV-1 proteases. However, since the 36th residue is located at a non-active site of the protease and has no direct interaction with any ligands, the structural role of M36I remains unclear. Here, we performed molecular dynamics (MD) simulations of M36I protease in complex with nelfinavir and revealed the influence of the M36I mutation. The results show that M36I regulates the size of the binding cavity of the protease. The reason for the rare emergence of D30N variants in non-subtype B HIV-1 proteases was also clarified from our computational analysis. 相似文献
64.
Uchida T Iwashita N Ohara-Imaizumi M Ogihara T Nagai S Choi JB Tamura Y Tada N Kawamori R Nakayama KI Nagamatsu S Watada H 《The Journal of biological chemistry》2007,282(4):2707-2716
Protein kinase C (PKC) is considered to modulate glucose-stimulated insulin secretion. Pancreatic beta cells express multiple isoforms of PKCs; however, the role of each isoform in glucose-stimulated insulin secretion remains controversial. In this study we investigated the role of PKCdelta, a major isoform expressed in pancreatic beta cells on beta cell function. Here, we showed that PKCdelta null mice manifested glucose intolerance with impaired insulin secretion. Insulin tolerance test showed no decrease in insulin sensitivity in PKCdelta null mice. Studies using islets isolated from these mice demonstrated decreased glucose- and KCl-stimulated insulin secretion. Perifusion studies indicated that mainly the second phase of insulin secretion was decreased. On the other hand, glucose-induced influx of Ca2+ into beta cells was not altered. Immunohistochemistry using total internal reflection fluorescence microscopy and electron microscopic analysis showed an increased number of insulin granules close to the plasma membrane in beta cells of PKCdelta null mice. Although PKC is thought to phosphorylate Munc18-1 and facilitate soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors complex formation, the phosphorylation of Munc18-1 by glucose stimulation was decreased in islets of PKCdelta null mice. We conclude that PKCdelta plays a non-redundant role in glucose-stimulated insulin secretion. The impaired insulin secretion in PKCdelta null mice is associated with reduced phosphorylation of Munc18-1. 相似文献
65.
66.
This study proved a possibility of a peptide probe for evaluating affinity properties of proteins. We have designed and synthesized three different peptide probes, H-Ala3-(Gly-Pro5)3-Gly-OH (peptide A), H-Ala3-(Gly-Pro5)-Gly-OH (peptide B) and H-Ala3-Gly-OH (peptide C) for testing their affinities to profilin. Each peptide probe was immobilized on a quartz crystal microbalance (QCM) sensor. The QCM sensor with the peptide A showed a 93 Hz decrease of resonant frequency which indicated profilin bound to the QCM sensor in a single layer. In a successive reaction with actin, the QCM analysis resulted in a 123 Hz decrease of resonant frequency which showed actin bound to the QCM sensor. A fluorescence microscope image of the sensor surface exhibited clear fluorescence after binding a rhodamine labeled actin on the sensor surface. These results supported stepwise reactions of profilin binding to the peptide A and actin binding to profilin. In the three peptide probes, the peptide A showed the highest affinity to profilin, i.e., sequence dependent affinity was confirmed. 相似文献
67.
68.
69.
70.