全文获取类型
收费全文 | 417篇 |
免费 | 23篇 |
专业分类
440篇 |
出版年
2022年 | 4篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 16篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1998年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 17篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1971年 | 7篇 |
1970年 | 8篇 |
1969年 | 9篇 |
1968年 | 5篇 |
1967年 | 4篇 |
1966年 | 3篇 |
排序方式: 共有440条查询结果,搜索用时 15 毫秒
61.
M.-L. Ahrens 《Biochimica et Biophysica Acta (BBA)/General Subjects》1973,320(1):86-96
The kinetics of the isomerizaton between the zwitterion and the unpolar form of 5′-deoxypyridoxal in its monoprotonated state have been studied by means of the T-jump technque; and the equilibrium constant of the isomerization process has been determined.Several parallel reactions contribute to the kinetics of interconvention: a direct intramolecular proton transfer and proton exchange with H3O+, OH?, the totally protonated and the totally depronated 5′-deoxypyridoxal molecule.The Rate constants for these parallel reactions are evaluated from the measured relaxation times. They are discussed in the light of general aspects of proton transfer reactions. 相似文献
62.
A novel multiplex quantitative real-time polymerase chain reaction (qPCR) for simultaneous detection of U. urealyticum and U. parvum was developed and compared with quantitative culture in Shepard''s 10 C medium for ureaplasmas in urethral swabs from 129 men and 66 women, and cervical swabs from 61 women. Using culture as the gold standard, the sensitivity of the qPCR was 96% and 95% for female urethral and cervical swabs, respectively. In male urethral swabs the sensitivity was 89%. The corresponding specificities were 100%, 87% and 99%. The qPCR showed a linear increasing DNA copy number with increasing colour-changing units. Although slightly less sensitive than culture, this multiplex qPCR assay detecting U. urealyticum and U. parvum constitutes a simple and fast alternative to the traditional methods for identification of ureaplasmas and allows simultaneous species differentiation and quantitation in clinical samples. Furthermore, specimens overgrown by other bacteria using the culture method can be evaluated in the qPCR. 相似文献
63.
64.
The echinoderm microtubule-associated protein (EMAP) is a 75-kDa, WD-repeat protein associated with the mitotic spindle apparatus. To understand EMAP's biological role, it is important to determine its affinity for microtubules (MTs) and other cytoskeletal components. To accomplish this goal, we utilized a low-cost, bubble-column bioreactor to express EMAP as a hexahistidine fusion (6his) protein in baculovirus-infected insect cells. After optimizing cell growth conditions, up to 30 mg of EMAP was obtained in the soluble cell lysate from a 1-liter culture. EMAP was purified to homogeneity in a two-step process that included immobilized metal-affinity chromatography (IMAC) and anion-exchange chromatography. In vitro binding studies on cytoskeletal components were performed with the 6his-EMAP. EMAP bound to MTs, but not actin or vimentin filaments, with an intrinsic dissociation constant of 0.18 microM and binding stoichiometry of 0.7 mol EMAP per mol tubulin heterodimer. In addition, we show that a strong MT binding domain resides in the 137 amino acid, NH(2)-terminus of EMAP and a weaker binding site in the WD-domain. Previous work has shown that the EMAP concentration in the sea urchin egg is over 4 microM. Together, these results show that there is sufficient EMAP in the egg to regulate the assembly of a large pool of maternally stored tubulin. 相似文献
65.
Tritiated bile acids: problems and recommendations 总被引:3,自引:0,他引:3
Kinetic studies of cholic and chenodeoxycholic acids were carried out in three patients by simultaneous intravenous administration of appropriate pairs of (3)H- and (14)C-labeled compounds. The results obtained indicated two sources of error: chemical impurity and loss of tritium by biological exchange. Precautions are listed for use of tritiated bile acids in studies of pool sizes and turnover rates. 相似文献
66.
In vivo studies of sterol and squalene secretion by human skin 总被引:3,自引:0,他引:3
This work was aimed at studying the quantity and composition of sterols and squalene secreted by the human skin. Lipids secreted by the entire skin were recovered by Soxhlet extraction of the clothing worn by a patient for 24 hr with a chloroform-methanol azeotrope and by extracting the water of a shower taken by the patient at the end of the 24-hr period. Squalene and sterols were quantified by gas-liquid chromatography. Plant sterols were separated from total sterols by thin-layer chromatography. Free and esterified cholesterol were separated by digitonin precipitation. In eight adults, seven of them with hyperlipoproteinemia, the total skin secretion of cholesterol ranged from 59 to 108 mg/day, with a mean of 88 +/- 17 (SD) mg/day. There was no difference in cholesterol secretion between the normocholesterolemic individual and the hypercholesterolemic ones, nor were there any differences according to type of hyperlipoproteinemia. Free cholesterol amounted to 54 +/- 5% of the total cholesterol. The secretion of squalene ranged from 125 to 475 mg/day in five patients. The secretion of both squalene and cholesterol was quite constant for any individual on a given diet. Cholesterol constituted 95.6 +/- 0.5% of the digitonin-precipitable total body surface sterols of eight patients, and lathosterol, the next largest fraction, 3.4 +/- 0.4%. Total plant sterols formed only 0.65 +/- 0.38% and beta-sitosterol 0.35 +/- 0.23% of the skin surface sterols in six patients whose dietary beta-sitosterol intake ranged from 230 to 3400 mg/day. 相似文献
67.
68.
Jonas Eberle Silvia Fabrizi Paul Lago Dirk Ahrens 《Cladistics : the international journal of the Willi Hennig Society》2017,33(2):183-197
Megadiverse insect groups present special difficulties for biogeographers because poor classification, incomplete knowledge of taxonomy, and many undescribed species can introduce a priori sampling bias to any analysis. The historical biogeography of Sericini, a tribe of melolonthine scarabs comprising about 4000 species, was investigated using the most comprehensive and time‐calibrated molecular phylogeny available today. Problems arising through nomenclatural confusion were overcome by extensive sampling (665 species) from all major lineages of the tribe. A West Gondwanan origin of Sericini (c. 112 Ma) was reconstructed using maximum parsimony, maximum‐likelihood and model‐based ancestral area estimation. Vicariance in the tribe's earliest history separated Neotropical and Old World Sericini, whereas subsequent lower Cretaceous biogeography of the tribe was characterized by repeated migrations out of Africa, resulting in the colonization of Eurasia and Madagascar. North America was colonized from Asia during the Cenozoic and a lineage of “Modern Sericini” reinvaded Africa. Diversification dynamics revealed three independent shifts to increased speciation rates: in African ant‐adapted Trochalus, Oriental Tetraserica, and Asian and African Sericina. Southern Africa is proposed as both cradle and refuge of Sericini. This area has retained many old lineages that portray the evolution of the African Sericini fauna as a series of taxon pulses. 相似文献
69.
Katharina Nöbauer Karin Hummel Corina Mayrhofer Maike Ahrens Francis M.C. Setyabudi Markus Schmidt‐Heydt Martin Eisenacher Ebrahim Razzazi‐Fazeli 《Proteomics》2017,17(9)
Mass spectrometric identification of proteins in species lacking validated sequence information is a major problem in veterinary science. In the present study, we used ochratoxin A producing Penicillium verrucosum to identify and quantitatively analyze proteins of an organism with yet no protein information available. The work presented here aimed to provide a comprehensive protein identification of P. verrucosum using shotgun proteomics. We were able to identify 3631 proteins in an “ab initio” translated database from DNA sequences of P. verrucosum. Additionally, a sequential window acquisition of all theoretical fragment‐ion spectra analysis was done to find differentially regulated proteins at two different time points of the growth curve. We compared the proteins at the beginning (day 3) and at the end of the log phase (day 12). 相似文献
70.
Pedro LC Pinheiro João CR Cardoso Ana S Gomes Juan Fuentes Deborah M Power Adelino VM Canário 《BMC evolutionary biology》2010,10(1):373