全文获取类型
收费全文 | 446篇 |
免费 | 79篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 22篇 |
2014年 | 17篇 |
2013年 | 12篇 |
2012年 | 20篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 9篇 |
1972年 | 5篇 |
1970年 | 6篇 |
1946年 | 2篇 |
排序方式: 共有525条查询结果,搜索用时 15 毫秒
51.
Jinxi Li Kevin Shefcheck John Callahan Catherine Fenselau 《Protein science : a publication of the Protein Society》2010,19(1):174-182
The Ara h 2 proteins are major determinants of peanut allergens. These proteins have not been fully studied at the molecular level. It has been previously proposed that there are two isoforms of Ara h 2, based on primary structures that were deduced from two reported cDNA sequences. In this report, four isoforms have been purified and characterized individually. Mass spectrometric methods have been used to determine the protein sequences and to define post‐translational modifications for all four isoforms. Two pairs of isoforms have been identified, corresponding to a long‐chain form and a form that is shorter by 12 amino acids. Each pair is further differentiated by the presence or absence of a two amino acid sequence at the carboxyl terminus of the protein. Modifications that were characterized include site‐specific hydroxylation of proline residues, but no glycosylation was found, in contrast to previous reports. 相似文献
52.
SSR markers closely associated with genes for resistance to root-knot nematode on chromosomes 11 and 14 of Upland cotton 总被引:2,自引:0,他引:2
Osman A. Gutiérrez Johnie N. Jenkins Jack C. McCarty Martin J. Wubben Russell W. Hayes Franklin E. Callahan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,121(7):1323-1337
Molecular markers closely linked to genes that confer a high level of resistance to root-knot nematode (RKN) [Meloidogyne incognita (Kofoid & White) Chitwood] in cotton (Gossypium
hirsutum L.) germplasm derived from Auburn 623 RNR would greatly facilitate cotton breeding programs. Our objectives were to identify
simple sequence repeat (SSR) markers linked to RKN resistance quantitative trait loci (QTL) and map these markers to specific
chromosomes. We developed three recombinant inbred line (RIL) populations by single seed descent from the crosses of RKN-resistant
parents M-240 RNR (M240), developed from the Auburn 623 RNR source, moderately resistant Clevewilt 6 (CLW6), one of the parents
of Auburn 623 RNR, and susceptible parent Stoneville 213 (ST213). These crosses were CLW6 × ST213, M240 × CLW6, and M240 × ST213.
RILs from these populations were grown under greenhouse conditions, inoculated with RKN eggs, scored for root gall index,
eggs plant−1, and eggs g−1 root. Plants were also genotyped with SSR markers. Results indicated that a minimum of two major genes were involved in the
RKN resistance of M240. One gene was localized to chromosome 11 and linked to the marker CIR 316-201. This CIR 316-201 allele
was also present in CLW6 but not in Mexico Wild (MW) (PI593649), both of which are parents of Auburn 623 RNR. A second RKN
resistance gene was localized to the short arm of chromosome 14 and was linked to the SSR markers BNL3545-118 and BNL3661-185.
These two marker alleles were not present in CLW6 but were present in MW. Our data also suggest that the chromosome 11 resistance
QTL primarily affects root galling while the QTL on chromosome 14 mediates reduced RKN egg production. The SSRs identified
in this study should be useful to select plants with high levels of RKN resistance in segregating populations derived from
Auburn 623 RNR. 相似文献
53.
Relationships of nicotianamine and other amino acids with nickel, zinc and iron in Thlaspi hyperaccumulators 总被引:1,自引:1,他引:0
Experimental evidence suggests that nicotianamine (NA) is involved in the complexation of metal ions in some metal-hyperaccumulating plants. Closely-related nickel (Ni)- and zinc (Zn)-hyperaccumulating species were studied to determine whether a correlation exists between the Ni and Zn concentrations and NA in foliar tissues. A liquid chromatography-mass spectrometry (LC-MS) procedure was developed to quantify the NA and amino acid contents using the derivatizing agent 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. A strong correlation emerged between Ni and NA, but not between Zn and NA. Concentrations of NA and L-histidine (His) also increased in response to higher Ni concentrations in the hydroponic solution supplied to a serpentine population of Thlaspi caerulescens. An inversely proportional correlation was found between the iron (Fe) and Ni concentrations in the leaves. Correlations were also found between Zn and asparagine. The results obtained in this study suggest that NA is involved in hyperaccumulation of Ni but not Zn. The inverse proportionality between the Ni and Fe concentrations in the leaf may suggest that Ni and Fe compete for complexation to NA. 相似文献
54.
In 1995, Radzicka and Wolfenden reported that the rate enhancement produced by orotidine 5'-phosphate decarboxylase (ODCase) approaches 10(17), making this enzyme the most effective pure protein catalyst known in Nature [A. Radzicka, R. Wolfenden, Science 267 (1995) 90-93]. Over the last 12 years, there have been many hypotheses put forward to explain that impressive effect. In this perspective, we provide a summary of the reaction pathways under consideration for ODCase, highlight the supporting and refuting data, and suggest experiments designed to further test each of the candidate pathways. 相似文献
55.
Azeredo-Coutinho RB Mendonça SC Callahan H Portal AC Max G 《The Journal of parasitology》2007,93(3):688-693
The first line drugs for the treatment of leishmaniasis are antimonial derivatives. Poor clinical response may be credited to factors linked to the host, the drug, or the parasite. We determined the sensitivity of Leishmania sp. promastigotes and amastigotes by counting parasites exposed to increasing concentrations of meglumine antimoniate (Glucantime). Leishmania braziliensis promastigotes were significantly more sensitive than those belonging to other species. The sensitivity of L. braziliensis isolates from patients with unfavorable clinical outcome, such as therapeutic failure or relapse, was significantly lower than those from patients who had clinical cure. Poor clinical response to therapy (therapeutic failure or relapse) was also associated with inadequate antimonial therapy. We also found a significant and positive correlation between promastigotes and intracellular amastigotes with regard to their in vitro susceptibilities to meglumine antimoniate. Our data provide evidence for an association between the sensitivity of promastigotes to antimonials in vitro and clinical response to therapy in American tegumentary leishmaniasis. The high sensitivity of the local L. braziliensis to meglumine antimoniate in vitro provides an explanation for the good clinical response of cutaneous leishmaniasis in the municipality of Rio de Janeiro, Brazil, even when low-dose regimens are employed. 相似文献
56.
57.
58.
Jian Xie Timothy Owen Ke Xia Ajay Vikram Singh Emiley Tou Lingyun Li Brigitte Arduini Hongmin Li Leo Q. Wan Brian Callahan Chunyu Wang 《The Journal of biological chemistry》2015,290(18):11591-11600
Zinc is an essential trace element with wide-ranging biological functions, whereas the Hedgehog (Hh) signaling pathway plays crucial roles in both development and disease. Here we show that there is a mechanistic link between zinc and Hh signaling. The upstream activator of Hh signaling, the Hh ligand, originates from Hh autoprocessing, which converts the Hh precursor protein to the Hh ligand. In an in vitro Hh autoprocessing assay we show that zinc inhibits Hh autoprocessing with a Ki of 2 μm. We then demonstrate that zinc inhibits Hh autoprocessing in a cellular environment with experiments in primary rat astrocyte culture. Solution NMR reveals that zinc binds the active site residues of the Hh autoprocessing domain to inhibit autoprocessing, and isothermal titration calorimetry provided the thermodynamics of the binding. In normal physiology, zinc likely acts as a negative regulator of Hh autoprocessing and inhibits the generation of Hh ligand and Hh signaling. In many diseases, zinc deficiency and elevated level of Hh ligand co-exist, including prostate cancer, lung cancer, ovarian cancer, and autism. Our data suggest a causal relationship between zinc deficiency and the overproduction of Hh ligand. 相似文献
59.
Topczewski JJ Callahan MP Kodet JG Inbarasu JD Mente NR Beutler JA Wiemer DF 《Bioorganic & medicinal chemistry》2011,19(24):7570-7581
The schweinfurthins are an intriguing group of anti-proliferative agents that display low nanomolar activities against several cell types, including the human-derived glioblastoma cell line SF-295, but have little impact on other cell lines even at micromolar concentrations. This activity has inspired the synthesis of seven of the natural schweinfurthins, all with the correct absolute stereochemistry, and a variety of analogues designed to probe different facets of the pharmacophore. Reported herein is the synthesis of several new schweinfurthin analogues varied at the C-5 position along with data on their biological activity in the NCI 60 cell-line assay. 相似文献
60.
Johnson AA Kyriacou B Callahan DL Carruthers L Stangoulis J Lombi E Tester M 《PloS one》2011,6(9):e24476