全文获取类型
收费全文 | 936篇 |
免费 | 96篇 |
出版年
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 40篇 |
2014年 | 43篇 |
2013年 | 45篇 |
2012年 | 64篇 |
2011年 | 74篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 42篇 |
2007年 | 34篇 |
2006年 | 36篇 |
2005年 | 39篇 |
2004年 | 49篇 |
2003年 | 44篇 |
2002年 | 50篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 25篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1968年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有1032条查询结果,搜索用时 15 毫秒
1.
2.
3.
2',5'-Dideoxy,3'-p-fluorosulfonylbenzoyl Adenosine (2',5'-dd3'-FSBA) was synthesized and found to be an agonist and affinity label for the "P"-site of adenylyl cyclase. This compound irreversibly inactivated both a crude detergent-dispersed adenylyl cyclase from rat brain and the partially purified enzyme from bovine brain. The irreversible inactivation by 100 to 200 microM 2',5'-dd3'-FSBA was blocked in a concentration-dependent manner by several established P-site inhibitors of adenylyl cyclase, 2',5'-dideoxyadenosine, 2'-d3'-AMP, adenosine, and 2'-deoxyadenosine, but not by inosine, N6-(phenylisopropyl)adenosine, adenine, 2'-d3':5'-cAMP, or 5'-AMP, agents known not to act at the P-site. Moreover, irreversible inactivation by 2',5'-dd3'-FSBA occurred in the presence of ATP at concentrations up to 3 mM, making it unlikely that inactivation was due to an effect on the enzyme's catalytic site. Adenylyl cyclase was also irreversibly inactivated by 5'-FSBA, although modestly (less than 20%) and apparently nonspecifically. Dithiothreitol protected the enzyme from irreversible inactivation by 2',5'-dd3'-FSBA, but reversible inhibition of the enzyme was still observed, although with reduced potency. When 2 mM dithiothreitol was added after a 30-min preincubation with 2',5'-dd3'-FSBA, the rat brain enzyme was partially (approximately 80%) reactivated. The data suggest that 2',5'-dd3'-FSBA may irreversibly inactivate adenylyl cyclase by reacting with a cysteinyl moiety in proximity to the P-site domain of the enzyme. These data together with results of studies of P-site inhibition kinetics published elsewhere (Johnson, R. A., and Shoshani, I. (1990) J. Biol. Chem. 265, 11595-11600) strongly suggest that the P-site and catalytic site are distinct domains on the enzyme. 2',5'-dd3'-FSBA, and especially its radiolabeled analog, should prove to be a useful probe for structural studies of adenylyl cyclase, particularly with regard to the P-site. 相似文献
5.
Claudio P. Albuquerque Eyan Yeung Shawn Ma Ting Fu Kevin D. Corbett Huilin Zhou 《PloS one》2015,10(12)
A variety of cellular pathways are regulated by protein modifications with ubiquitin-family proteins. SUMO, the Small Ubiquitin-like MOdifier, is covalently attached to lysine on target proteins via a cascade reaction catalyzed by E1, E2, and E3 enzymes. A major barrier to understanding the diverse regulatory roles of SUMO has been a lack of suitable methods to identify protein sumoylation sites. Here we developed a mass-spectrometry (MS) based approach combining chemical and enzymatic modifications to identify sumoylation sites. We applied this method to analyze the auto-sumoylation of the E1 enzyme in vitro and compared it to the GG-remnant method using Smt3-I96R as a substrate. We further examined the effect of smt3-I96R mutation in vivo and performed a proteome-wide analysis of protein sumoylation sites in Saccharomyces cerevisiae. To validate these findings, we confirmed several sumoylation sites of Aos1 and Uba2 in vivo. Together, these results demonstrate that our chemical and enzymatic method for identifying protein sumoylation sites provides a useful tool and that a combination of methods allows a detailed analysis of protein sumoylation sites. 相似文献
6.
DNA base composition determines the specificity of UvrABC endonuclease incision of a psoralen cross-link 总被引:8,自引:0,他引:8
The sequences flanking a psoralen interstrand cross-link may determine how it is repaired. Our comparison of the Escherichia coli UvrABC endonuclease incision of a variety of specific cross-link sequences in a single natural DNA fragment showed that DNA base composition determines which of two cross-linked DNA strands will be incised. G/C enrichment of the region 6-12 bases 5' of the modified T on the furan-side strand results in preferential incision of the furan-side strand. When the G/C-rich region is on the 3' side, or on neither side, incisions occur on either strand. These effects of DNA base composition suggest that UvrAB can bind in two ways to a psoralen cross-link. 相似文献
7.
Yeung Jade Jugé Lauriane Hatt Alice Bilston Lynne E. 《Biomechanics and modeling in mechanobiology》2019,18(5):1497-1505
Biomechanics and Modeling in Mechanobiology - The aim of this study is to characterise the stiffness of white and grey matter in paediatric subjects using magnetic resonance elastography (MRE) and... 相似文献
8.
Harparkash Kaur Elizabeth Louise Allan Ibrahim Mamadu Zoe Hall Ogochukwu Ibe Mohamed El Sherbiny Albert van Wyk Shunmay Yeung Isabel Swamidoss Michael D. Green Prabha Dwivedi Maria Julia Culzoni Sian Clarke David Schellenberg Facundo M. Fernández Obinna Onwujekwe 《PloS one》2015,10(5)
BackgroundArtemisinin-based combination therapies are recommended by the World Health Organisation (WHO) as first-line treatment for Plasmodium falciparum malaria, yet medication must be of good quality for efficacious treatment. A recent meta-analysis reported 35% (796/2,296) of antimalarial drug samples from 21 Sub-Saharan African countries, purchased from outlets predominantly using convenience sampling, failed chemical content analysis. We used three sampling strategies to purchase artemisinin-containing antimalarials (ACAs) in Enugu metropolis, Nigeria, and compared the resulting quality estimates.MethodsACAs were purchased using three sampling approaches - convenience, mystery clients and overt, within a defined area and sampling frame in Enugu metropolis. The active pharmaceutical ingredients were assessed using high-performance liquid chromatography and confirmed by mass spectrometry at three independent laboratories. Results were expressed as percentage of APIs stated on the packaging and used to categorise each sample as acceptable quality, substandard, degraded, or falsified.ResultsContent analysis of 3024 samples purchased from 421 outlets using convenience (n=200), mystery (n=1,919) and overt (n=905) approaches, showed overall 90.8% ACAs to be of acceptable quality, 6.8% substandard, 1.3% degraded and 1.2% falsified. Convenience sampling yielded a significantly higher prevalence of poor quality ACAs, but was not evident by the mystery and overt sampling strategies both of which yielded results that were comparable between each other. Artesunate (n=135; 4 falsified) and dihydroartemisinin (n=14) monotherapy tablets, not recommended by WHO, were also identified.ConclusionRandomised sampling identified fewer falsified ACAs than previously reported by convenience approaches. Our findings emphasise the need for specific consideration to be given to sampling frame and sampling approach if representative information on drug quality is to be obtained. 相似文献
9.
Riikka Jokinen Taina Lahtinen Paula Marttinen Maarit My?h?nen Pilvi Ruotsalainen Nicolas Yeung Antonina Shvetsova Alexander J. Kastaniotis J. Kalervo Hiltunen Tiina ?hman Tuula A. Nyman Hartmut Weiler Brendan J. Battersby 《Genetics》2015,200(1):221-235
Mammalian mitochondrial DNA (mtDNA) is a high-copy maternally inherited genome essential for aerobic energy metabolism. Mutations in mtDNA can lead to heteroplasmy, the co-occurence of two different mtDNA variants in the same cell, which can segregate in a tissue-specific manner affecting the onset and severity of mitochondrial dysfunction. To investigate mechanisms regulating mtDNA segregation we use a heteroplasmic mouse model with two polymorphic neutral mtDNA haplotypes (NZB and BALB) that displays tissue-specific and age-dependent selection for mtDNA haplotypes. In the hematopoietic compartment there is selection for the BALB mtDNA haplotype, a phenotype that can be modified by allelic variants of Gimap3. Gimap3 is a tail-anchored member of the GTPase of the immunity-associated protein (Gimap) family of protein scaffolds important for leukocyte development and survival. Here we show how the expression of two murine Gimap3 alleles from Mus musculus domesticus and M. m. castaneus differentially affect mtDNA segregation. The castaneus allele has incorporated a uORF (upstream open reading frame) in-frame with the Gimap3 mRNA that impairs translation and imparts a negative effect on the steady-state protein abundance. We found that quantitative changes in the expression of Gimap3 and the paralogue Gimap5, which encodes a lysosomal protein, affect mtDNA segregation in the mouse hematopoietic tissues. We also show that Gimap3 localizes to the endoplasmic reticulum and not mitochondria as previously reported. Collectively these data show that the abundance of protein scaffolds on the endoplasmic reticulum and lysosomes are important to the segregation of the mitochondrial genome in the mouse hematopoietic compartment. 相似文献
10.
Yat Ming Lau Tak Hong Cheung Winnie Yeo Frankie Mo Mei Yung Yu Kun Min Lee Wendy C. S. Ho Apple C. M. Yeung Priscilla T. Y. Law Paul K. S. Chan 《PloS one》2015,10(4)
High-risk human papillomavirus (HPV) types are associated with cervical cancer. It is well established that individual HPV types vary in oncogenicity, but current data on their prognostic implication remain controversial. We examined the association between HPV types/species and the survival of 236 Chinese women aged 26–87 (mean 54.4) years after receiving primary treatment for cervical cancer. Overall, 45.8% were of FIGO stage I, 41.9% stage II, and 12.3% stage III. The four most prevalent types found were HPV-16 (60.2%), HPV-18 (21.6%), HPV-52 (11.9%), and HPV-58 (9.3%). Overall, 19.5% of patients had multiple-type infections, 78.4% harboured one or more alpha-9 species, and 28.8% harboured one or more alpha-7 species. After a median follow-up of 8.0 years, 156 (66.1%) patients survived. The 3-year overall survival rate was 75.5%. Factors independently associated with a poorer 3-year overall survival were age >60 years, tumour size >4 cm, lymph node involvement and treatment with radiotherapy+/-chemotherapy. Univariate analysis showed HPV-16 single-type infection was associated with a marginally poorer disease-specific survival (71.6% vs. 87.0%, HR: 1.71, 95% CI = 1.01–2.90), whereas non-HPV-16 alpha-9 species was associated with a better disease-specific survival (90.0% vs. 76.2%, HR: 0.36, 95% CI = 0.16–0.79). However, on multivariate analysis, HPV infection status irrespective of different grouping methods, including individual types, species, single-type or co-infection, did not carry any significant prognostic significance. In conclusion, we did not observe any association between infection with a particular HPV type/species and survival. An HPV type-based stratification in treatment and follow-up plan could not be recommended. 相似文献