全文获取类型
收费全文 | 274篇 |
免费 | 21篇 |
出版年
2020年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 4篇 |
2015年 | 13篇 |
2014年 | 14篇 |
2013年 | 20篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1966年 | 6篇 |
1952年 | 1篇 |
排序方式: 共有295条查询结果,搜索用时 234 毫秒
1.
2.
B Nowicki M Rhen V V?is?nen-Rhen A Pere T K Korhonen 《Journal of general microbiology》1985,131(5):1263-1266
Immunofluorescence staining with fimbria-specific antibodies was used to study the organization of fimbriate cells in colonies of Escherichia coli strain 3040. The strain has both type-1 and S fimbriae and shows fast phase variation between the fimbrial types. Colonies stained in sectors whose length and number per colony were dependent on the fimbrial phase of progeny cells. It is proposed that such sectors result from fimbrial phase variation. 相似文献
3.
Stephen Nowicki Peter Marler Alicia Maynard Susan Peters 《Ethology : formerly Zeitschrift fur Tierpsychologie》1992,90(3):225-235
Song sparrow (Melospiza melodia) songs are composed largely of pure-tonal sounds. This paper investigates the role that learning plays in the development of the tonal structure of song sparrow songs, as well as the role that tonal quality plays in determining the suitability of songs as models for learning. 20 birds were trained with both normal pure-tonal songs and modified songs that included harmonic overtones. The harmonic-modified songs were obtained from birds singing in a helium atmosphere, the result of which is to perturb vocal tract resonances and thus alter a song's tonal quality. Subjects learned equally well from normal and harmonic models. Birds that learned material from harmonic models reproduced some of this material with harmonic overtones, but the majority of notes learned from harmonic models were subsequently reproduced as pure-tonal copies. Thus, the tonal structure of songs does not influence young song sparrows in their selection of song models, but there is a strong tendency to reproduce songs in a pure-tonal fashion, even if learned from harmonic models. 相似文献
4.
An assessment of the annual mass balance of carbon,nitrogen, and phosphorus in Narragansett Bay 总被引:11,自引:3,他引:8
Narragansett Bay is a relatively well-mixed, high salinity coastal embayment and estuary complex in southern New England (USA). Much of the shoreline is urban and the watershed is densely developed. We have combined our data on C, N, and P inputs to this system, on C, N, and P accumulation in the sediments, and on denitrification with extensive work by others to develop approximate annual mass balances for these elements. The results show that primary production within the bay is the major source of organic carbon (4 times greater than other sources), that land drainage and upstream sewage and fertilizer are the major sources of N, and that landward flowing bottom water from offshore may be a major source of dissolved inorganic phosphorus. Most of the nutrients entering the bay arrive in dissolved inorganic form, though DON is a significant component of the N carried by the rivers. About 40% of the DIN in the rivers is in the form of ammonia. Sedimentation rates are low in most of Narragansett Bay, and it appears that less than 20% of the total annual input of each of these elements is retained within the system. A very small amount of C, N, and P is removed in fisheries landings, denitrification in the sediments removes perhaps 10–25% of the N input, and most of the carbon fixed in the system is respired within it. Stoichiometric calculations suggest that some 10–20% of the organic matter formed in the bay is exported to offshore and that Narragansett Bay is an autotrophic system. Most of the N and P that enters the bay is, however, exported to offshore waters in dissolved inorganic form. This assessment of the overall biogeochemical behavior of C, N, and P in the bay is consistent with more rigorously constrained mass balances obtained using large living models or mesocosms of the bay at the Marine Ecosystem Research Laboratory (MERL). 相似文献
5.
Differential effects of protein synthesis inhibition on CTL and targets in cell-mediated cytotoxicity 总被引:2,自引:0,他引:2
The reactions that lead to target cell lysis by cytotoxic T cells (CTL) are despite intensive investigations poorly understood. To examine the relative roles effectors and targets play in the lytic reaction, protein synthesis in either CTL or targets was inhibited before assay of lysis. We show, in agreement with previous results, that de novo protein synthesis is not necessary in either effectors or targets during the cytolytic reaction. However, activation of CTL requires protein synthesis. Activated CTL respond to protein synthesis inhibitors with a cycling of activity, a result that is interpreted to be consistent with a stimulus secretion mechanism. Treatment of targets with protein synthesis inhibitors prior to incubation with CTL leads to a very rapid and irreversible loss of lytic susceptibility. It is shown that the decrease in lysability is not due to lack of proper CTL target interaction: MHC class I antigens are expressed on drug-treated targets and these cells serve as cold targets in competitive inhibition experiments. Moreover, drug-treated targets trigger transient Ca2+ mobilization and generation of inositol phosphates in CTL. It is therefore concluded that drug-treated targets are able to trigger CTL function but lack a component that is required for their successful lysis. 相似文献
6.
The alpha-amino group of bovine Growth Hormone was selectively modified with TNBS with no detectable changes in growth promoting activity. TNP was used as hapten for the production of antibodies against the end terminal region of bGH. The region near the alpha-amino group is not involved in the binding of bGH to rat liver cells, and it seems to be away from the part of the molecule that interacts with the cell binding sites. 相似文献
7.
8.
Marcin Nowicki Logan C. Houston Sarah L. Boggess Anthony S. Aiello Miriam Pay‐Milans Margaret E. Staton Mitsuhiro Hayashida Masahiro Yamanaka Shigetoshi Eda Robert N. Trigiano 《Ecology and evolution》2020,10(15):8299-8312
Cornus kousa (Asian dogwood), an East Asia native tree, is the most economically important species of the dogwood genus, owing to its desirable horticultural traits and ability to hybridize with North America‐native dogwoods. To assess the species genetic diversity and to better inform the ongoing and future breeding efforts, we assembled an herbarium and arboretum collection of 131 noncultivated C. kousa specimens. Genotyping and capillary electrophoresis analyses of our C. kousa collection with the newly developed genic and published nuclear genomic microsatellites permitted assessment of genetic diversity and evolutionary history of the species. Regardless of the microsatellite type used, the study yielded generally similar insights into the C. kousa diversity with subtle differences deriving from and underlining the marker used. The accrued evidence pointed to the species distinct genetic pools related to the plant country of origin. This can be helpful in the development of the commercial cultivars for this important ornamental crop with increased pyramided utility traits. Analyses of the C. kousa evolutionary history using the accrued genotyping datasets pointed to an unsampled ancestor population, possibly now extinct, as per the phylogeography of the region. To our knowledge, there are few studies utilizing the same gDNA collection to compare performance of genomic and genic microsatellites. This is the first detailed report on C. kousa species diversity and evolutionary history inference. 相似文献
9.
David F Ten Cate Jolanda J Luime Nanno Swen Andreas H Gerards Mike H De Jager Natalja M Basoski Johanna MW Hazes Cees J Haagsma Johannes WG Jacobs 《Arthritis research & therapy》2013,15(1):R4
Introduction
Ultrasonography (US) might have an added value to clinical examination in diagnosing early rheumatoid arthritis (RA) and assessing remission of RA. We aimed to clarify the added value of US in RA in these situations performing a systematic review.Methods
A systematic literature search was performed for RA, US, diagnosis and remission. Methodological quality was assessed; the wide variability in the design of studies prohibited pooling of results.Results
Six papers on the added value of US diagnosing early RA were found, in which at least bilateral metacarpophalangeal (MCP), wrists and metatarsophalangeal (MTP) joints were scanned. Compared to clinical examination, US was superior with regard to detecting synovitis and predicting progression to persistent arthritis or RA. Eleven papers on assessing remission were identified, in which at least the wrist and the MCP joints of the dominant hand were scanned. Often US detected inflammation in patients clinically in remission, irrespective of the remission criteria used. Power Doppler signs of synovitis predicted X-ray progression and future flare in patients clinically in remission.Conclusions
US appears to have added value to clinical examination for diagnosing of RA when scanning at least MCP, wrist and MTP joints, and, when evaluating remission of RA, scanning at least wrist and MCP joints of the dominant hand. For both purposes primarily power Doppler US might be used since its results are less equivocal than those of greyscale US. 相似文献10.
Bartlomiej Perek Agnieszka Malinska Sebastian Stefaniak Danuta Ostalska-Nowicka Marcin Misterski Maciej Zabel Anuj Suri Michal Nowicki 《PloS one》2013,8(8)