全文获取类型
收费全文 | 1126篇 |
免费 | 110篇 |
国内免费 | 1篇 |
出版年
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2016年 | 22篇 |
2015年 | 23篇 |
2014年 | 39篇 |
2013年 | 46篇 |
2012年 | 49篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 40篇 |
2007年 | 35篇 |
2006年 | 51篇 |
2005年 | 51篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 37篇 |
2001年 | 37篇 |
2000年 | 32篇 |
1999年 | 24篇 |
1998年 | 13篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 20篇 |
1973年 | 11篇 |
1972年 | 9篇 |
1970年 | 12篇 |
1967年 | 10篇 |
排序方式: 共有1237条查询结果,搜索用时 62 毫秒
61.
Sandra Kittelmann Henning Seedorf William A. Walters Jose C. Clemente Rob Knight Jeffrey I. Gordon Peter H. Janssen 《PloS one》2013,8(2)
Ruminants rely on a complex rumen microbial community to convert dietary plant material to energy-yielding products. Here we developed a method to simultaneously analyze the community''s bacterial and archaeal 16S rRNA genes, ciliate 18S rRNA genes and anaerobic fungal internal transcribed spacer 1 genes using 12 DNA samples derived from 11 different rumen samples from three host species (Ovis aries, Bos taurus, Cervus elephas) and multiplex 454 Titanium pyrosequencing. We show that the mixing ratio of the group-specific DNA templates before emulsion PCR is crucial to compensate for differences in amplicon length. This method, in contrast to using a non-specific universal primer pair, avoids sequencing non-targeted DNA, such as plant- or endophyte-derived rRNA genes, and allows increased or decreased levels of community structure resolution for each microbial group as needed. Communities analyzed with different primers always grouped by sample origin rather than by the primers used. However, primer choice had a greater impact on apparent archaeal community structure than on bacterial community structure, and biases for certain methanogen groups were detected. Co-occurrence analysis of microbial taxa from all three domains of life suggested strong within- and between-domain correlations between different groups of microorganisms within the rumen. The approach used to simultaneously characterize bacterial, archaeal and eukaryotic components of a microbiota should be applicable to other communities occupying diverse habitats. 相似文献
62.
The potential of using the entomopathogenic nematode Steinernema feltiae to control the sweetpotato whitefly Bemisia tabaci (Gennadius) has been established in previous laboratory studies. However, laboratory studies can overestimate the level of control achieved by biocontrol agents in the glasshouse. Glasshouse trials are therefore required to confirm laboratory results before full-scale commercial development is considered. Under both controlled laboratory and glasshouse conditions high mortality of second instar B. tabaci (>90% and >80%, respectively) was recorded after application of S. feltiae. The efficacy of the biocontrol agent at various application rates was also investigated, where halving the rate of S. feltiae application caused no significant reduction in B. tabaci mortality on tomato foliage. Steinernema feltiae has shown much potential for incorporation into integrated pest management strategies for the control of B. tabaci. 相似文献
63.
Jada Benn Torres Victoria Martucci Melinda C. Aldrich Miguel G. Vilar Taryn MacKinney Muhammad Tariq Jill B. Gaieski Ricardo Bharath Hernandez Zoila E. Browne Marlon Stevenson Wendell Walters Theodore G. Schurr The Genographic Consortium 《American journal of physical anthropology》2019,169(3):482-497
64.
65.
Anne M. Bronikowski Richard P. Meisel Peggy R. Biga James
R. Walters Judith E. Mank Erica Larschan Gerald S. Wilkinson Nicole Valenzuela Ashley Mae Conard Joo Pedro de Magalhes Jingyue
Duan Amy E. Elias Tony Gamble Rita
M. Graze Kristin E. Gribble Jill A. Kreiling Nicole C. Riddle 《Aging cell》2022,21(2)
Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age‐associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer‐lived females, species where males live longer, and species lacking sex differences in lifespan. The underlying causes of sex differences in aging remain mostly unknown. Currently, we do not understand the molecular drivers of sex differences in aging, or whether they are related to the accepted hallmarks or pillars of aging or linked to other well‐characterized processes. In particular, understanding the role of sex‐determination mechanisms and sex differences in aging is relatively understudied. Here, we take a comparative, interdisciplinary approach to explore various hypotheses about how sex differences in aging arise. We discuss genomic, morphological, and environmental differences between the sexes and how these relate to sex differences in aging. Finally, we present some suggestions for future research in this area and provide recommendations for promising experimental designs. 相似文献
66.
67.
68.
The effect of external potassium (K) and cesium (Cs) on the inwardly rectifying K channel ROMK2 (K(ir)1.1b) was studied in Xenopus oocytes. Elevating external K from 1 to 10 mM increased whole-cell outward conductance by a factor of 3.4 +/- 0.4 in 15 min and by a factor of 5.7 +/- 0.9 in 30 min (n = 22). Replacing external Na by Cs blocked inward conductance but increased whole-cell conductance by a factor of 4.5 +/- 0.5 over a period of 40 min (n = 15). In addition to this slow increase in conductance, there was also a small, rapid increase in conductance that occurred as soon as ROMK was exposed to external cesium or 10 mM K. This rapid increase could be explained by the observed increase in ROMK single-channel conductance from 6.4 +/- 0.8 pS to 11.1 +/- 0.8 pS (10 mM K, n = 8) or 11.7 +/- 1.2 pS (Cs, n = 8). There was no effect of either 10 mM K or cesium on the high open probability (P(o) = 0.97 +/- 0.01; n = 12) of ROMK outward currents. In patch-clamp recordings, the number of active channels increased when the K concentration at the outside surface was raised from 1 to 50 mM K. In cell-attached patches, exposure to 50 mM external K produced one or more additional channels in 9/16 patches. No change in channel number was observed in patches continuously exposed to 50 mM external K. Hence, the slow increase in whole-cell conductance is interpreted as activation of pre-existing ROMK channels that had been inactivated by low external K. This type of time-dependent channel activation was not seen with IRK1 (K(ir)2.1) or in ROMK2 mutants in which any one of 6 residues, F129, Q133, E132, V121, L117, or K61, were replaced by their respective IRK1 homologs. These results are consistent with a model in which ROMK can exist in either an activated mode or an inactivated mode. Within the activated mode, individual channels undergo rapid transitions between open and closed states. High (10 mM) external K or Cs stabilizes the activated mode, and low external K stabilizes the inactivated mode. Mutation of a pH-sensing site (ROMK2-K61) prevents transitions from activated to inactivated modes. This is consistent with a direct effect of external K or Cs on the gating of ROMK by internal pH. 相似文献
69.
Walters RW Yi SM Keshavjee S Brown KE Welsh MJ Chiorini JA Zabner J 《The Journal of biological chemistry》2001,276(23):20610-20616
Recombinant adeno-associated viruses (AAV) are promising gene therapy vectors. Whereas AAV serotype 2-mediated gene transfer to muscle has partially replaced factor IX deficiency in hemophilia patients, its ability to mediate gene transfer to the lungs for cystic fibrosis is hindered by lack of apical receptors. However, AAV serotype 5 infects human airway epithelia from the lumenal surface. We found that in contrast to AAV2, the apical membrane of airway epithelia contains abundant high affinity receptors for AAV5. Binding and gene transfer with AAV5 was abolished by genetic or enzymatic removal of sialic acid from the cell surface. Furthermore, binding and gene transfer to airway epithelia was competed by lectins that specifically bind 2,3-linked sialic acid. These observations suggest that 2,3-linked sialic acid is either a receptor for AAV5 or it is a necessary component of a receptor complex. Further elucidation of the receptor for this virus should enhance understanding of parvovirus biology and expand the therapeutic targets for AAV vectors. 相似文献
70.