全文获取类型
收费全文 | 254篇 |
免费 | 27篇 |
专业分类
281篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 16篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 19篇 |
2009年 | 11篇 |
2008年 | 22篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 6篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1968年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有281条查询结果,搜索用时 15 毫秒
1.
... We can therefore conclude that either we should go for equality; and in that case QALYs are unfair because they haven't got enough of an ageist bias. Or we should accept consequentialism; and in that case QALYs have just the right sort of ageist bias. No plausible case can, however, be made for the claim that QALYs have an unfair bias against old people. Other things being equal we ought when distributing resources essential for survival favour the young. This ethical claim can be supported both by reference to equality (the life-time-view) and by reference to consequentialism (and the premises that resources generally will be more useful when given to young people). 相似文献
2.
Hartmut Köttig Gerhard Rottner Karl-Friedrich Beck Michael Schweizer Eckhart Schweizer 《Molecular & general genetics : MGG》1991,226(1-2):310-314
Summary The fatty acid synthetase (FAS) gene FAS1 of the alkane-utilizing yeast Yarrowia lipolytica was cloned and sequenced. The gene is represented by an intron-free reading frame of 6228 by encoding a protein of 2076 amino acids and 229980 Da molecular weight. This protein exhibits a 58% sequence similarity to the corresponding Saccharomyces cerevisiae FAS -subunit. The sequential order of the five FAS1-encoded enzyme domains, acetyl transferase, enoyl reductase, dehydratase and malonyl/palmityl-transferase, is co-linear in both organisms. This finding agrees with available evidence that the functional organization of FAS genes is similar in related organisms but differs considerably between unrelated species. In addition, previously reported conflicting data concerning the 3 end of S. cerevisiae FAS1 were re-examined by genomic and cDNA sequencing of the relevant portion of the gene. Thereby, the translational stop codon was shown to lie considerably downstream of both published termination sites. The S. cerevisiae FAS1 gene thus has a corrected length of 6153 by and encodes a protein of 2051 amino acids and 228667 Da molecular weight. 相似文献
3.
Frank K. Klemens John C. Severns Ramasamy Tamilarasan David R. McMillin 《Inorganica chimica acta》1996,250(1-2):75-79
This study dealt with the demetalation and remetalation chemistry of the copper-containing protein ceruloplasmin. For the enzyme from human plasma, dialysis against cyanide at 4°C readily removed copper. Although the apoprotein took up copper(I) at the same temperature, the characteristic blue color of the native protein did not return to any significant extent. However, excellent reconstitution occurred when we added copper(I) at room temperature. With porcine ceruloplasmin, it was more practical to carry out the copper removal step at room temperature, but the reconstitution went smoothly at 4°C. With either source of ceruloplasmin, the binding of the six essential copper ions was generally a highly cooperative process, but the results were different when we combined the apoprotein with Hg(II). After the protein took up 2 mercury ions, it would take up only 1–2 more metal ions even after exposure to a large excess of copper(I). In order to accomodate the various experimental results, we have proposed that a reversible conformational change must occur during the demetalation and remetalation processes. During the remetalation process, it is therefore important that metal uptake occurs in the proper sequence. 相似文献
4.
Sebastian Voigt Reinhart Gossrau Oliver Baum Klemens L?ster Werner Hofmann Werner Reutter 《The Histochemical journal》1995,27(2):123-132
Summary The 11-integrin is known to be a receptor for collagen and laminin mediating cell-matrix interactions. A monoclonal antibody, 33.4, which specifically inhibits the 1-integrin-mediated in vitro cell-collagen binding of rat hepatocytes and hepatoma-derived A-cells (Löster et al., 1994), was used to purify by immunoaffinity chromatography the 1-integrin subunit from rat liver in large quantities for inducing a polyclonal antiserum. In immunoblot analysis on membrane extracts of several rat organs this polyclonal antiserum recognized only a 190 kDa-band, suggesting that it is highly specific for the 1-integrin subunit. A sandwich-ELISA with monoclonal antibody 33.4 and the polyclonal antiserum against the 1-integrin subunit, respectively, enabled the quantitative expression pattern of the 1-integrin subunit to be studied in different rat organs. With the exceptions of brain (not detectable) and muscle (low concentration), the 1-integrin subunit was detectable in almost all organs of the digestive, respiratory and urogenital system as well as in lymphatic organs. The highest relative concentrations of 1-integrin subunit were found in uterus, lung and spleen, whereas in seminal vesicle, stomach, parotid gland, epididymis, kidney and liver only modest concentrations were evident. The organ distribution and localization of 1-integrin subunit were studied by immunohistochemistry with monoclonal and polyclonal antibodies. Immunoreactivity was present in the plasma membranes of all smooth muscle cells, vascular endothelial cells of many organs and fibrocyte-fibroblast sheaths in the heart and kidney. Since these cells are in close contact with collagen-containing basal membranes as well as reticular fibrils, strong evidence exists that in rat tissues the 1-integrin subunit is expressed at sites where collagen is present and might be involved in vivo in cell—ollagen binding.Dedicated to Professor Peter Sitte on the occasion of his 65th birthday 相似文献
5.
Most depth recorders used to study the diving behaviour of polar marine endotherms record depth data at specific time intervals. The length of recording interval can have potentially profound implications for the interpretation of the data. We used data acquired on the diving behaviour of king penguins, Aptenodytes patagonicus, to examine the validity of various analyses routinely conducted on depth data. In our experiments, increasing the sampling interval led to an underestimation of the number of dives performed, an overestimation in mean dive duration and substantial changes in the form of the dive profile. Our analysis indicates that depth data should be recorded at a minimum rate corresponding to 10% of the total dive duration and that conventional dive profile categorization may be inappropriate. Alternatives that are less subjective, and based on curve fits of dive depth versus time, are proposed. 相似文献
6.
7.
A MicroRNA Cluster miR‐23–24–27 Is Upregulated by Aldosterone in the Distal Kidney Nephron Where it Alters Sodium Transport 下载免费PDF全文
8.
Nicols A. Lois Leonardo Campagna Ulises Balza Michael J. Polito Klemens Pütz Juliana A. Vianna Annick Morgenthaler Esteban Frere Ricardo Senz‐Samaniego Andrea Raya Rey Bettina Mahler 《Ecology and evolution》2020,10(7):3346-3355
Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connectivity and foraging niche overlap among southern rockhopper penguin colonies of the coast of southern South America using genomic and stable isotope analyses. We found two distinct genetic clusters and detected low admixture between northern and southern colonies. Stable isotope analysis indicated niche variability between colonies, with Malvinas/Falklands colonies encompassing the species entire isotopic foraging niche, while the remaining colonies had smaller, nonoverlapping niches. A recently founded colony in continental Patagonia differed in isotopic niche width and position with Malvinas/Falklands colonies, its genetically identified founder population, suggesting the exploitation of novel foraging areas and/or prey items. Additionally, dispersing individuals found dead across the Patagonian shore in an unusual mortality event were also assigned to the northern cluster, suggesting northern individuals reach southern localities, but do not breed in these colonies. Facilitated by variability in foraging strategies, and especially during unfavorable conditions, the number of dispersing individuals may increase and enhance the probability of founding new colonies. Metapopulation demographic dynamics in seabirds should account for interannual variability in dispersal behavior and pay special attention to extreme climatic events, classically related to negative effects on population trends. 相似文献
9.
10.
Winter Susanne Zaplata Markus Klemens Rzanny Michael Schaaf Wolfgang Fischer Anton Ulrich Werner 《Plant Ecology》2019,220(4-5):499-509
Plant Ecology - Ecological multifunctionality quantifies the functional performance of various important plant traits and increases with growing structural habitat heterogeneity, number of plant... 相似文献