全文获取类型
收费全文 | 769篇 |
免费 | 72篇 |
出版年
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 36篇 |
2012年 | 34篇 |
2011年 | 54篇 |
2010年 | 18篇 |
2009年 | 21篇 |
2008年 | 27篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 33篇 |
2003年 | 35篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1974年 | 11篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1959年 | 5篇 |
1950年 | 4篇 |
排序方式: 共有841条查询结果,搜索用时 172 毫秒
111.
Z Guo J Wang L Meng Q Wu O Kim J Hart G He P Zhou J R Thistlethwaite M L Alegre Y X Fu K A Newell 《Journal of immunology (Baltimore, Md. : 1950)》2001,167(9):4796-4800
Blocking the CD28/B7 and/or CD154/CD40 costimulatory pathways promotes long-term allograft survival in many transplant models where CD4(+) T cells are necessary for rejection. When CD8(+) T cells are sufficient to mediate rejection, these approaches fail, resulting in costimulation blockade-resistant rejection. To address this problem we examined the role of lymphotoxin-related molecules in CD8(+) T cell-mediated rejection of murine intestinal allografts. Targeting membrane lymphotoxin by means of a fusion protein, mAb, or genetic mutation inhibited rejection of intestinal allografts by CD8(+) T cells. This effect was associated with decreased monokine induced by IFN-gamma (Mig) and secondary lymphoid chemokine (SLC) gene expression within allografts and spleens respectively. Blocking membrane lymphotoxin did not inhibit rejection mediated by CD4(+) T cells. Combining disruption of membrane lymphotoxin and treatment with CTLA4-Ig inhibited rejection in wild-type mice. These data demonstrate that membrane lymphotoxin is an important regulatory molecule for CD8(+) T cells mediating rejection and suggest a strategy to avoid costimulation blockade-resistant rejection. 相似文献
112.
Pyrosequencing as a Method for Grouping of Listeria monocytogenes Strains on the Basis of Single-Nucleotide Polymorphisms in the inlB Gene 总被引:1,自引:0,他引:1 下载免费PDF全文
Helle Unnerstad Henrik Ericsson Anders Alderborn Wilhelm Tham Marie-Louise Danielsson-Tham Jens G. Mattsson 《Applied microbiology》2001,67(11):5339-5342
By using pyrosequencing (i.e., sequencing by synthesis) 106 strains of different serovars of Listeria monocytogenes were rapidly grouped into four categories based on nucleotide variations at positions 1575 and 1578 of the inlB gene. Strains of serovars 1/2a and 1/2c constituted one group, and strains of serovars 1/2b and 3b constituted another group, whereas serovar 4b strains were separated into two groups. 相似文献
113.
Multilocus
Sequence Typing for Comparison of Veterinary and Human
Isolates of Campylobacter jejuni 总被引:1,自引:0,他引:1 下载免费PDF全文
Georgina Manning Christopher G. Dowson Mary C. Bagnall If H. Ahmed Malcolm West Diane G. Newell 《Applied microbiology》2003,69(11):6370-6379
Multilocus sequence typing (MLST) has been applied to 266 Campylobacter jejuni isolates, mainly from veterinary sources, including cattle, sheep, poultry, pigs, pets, and the environment, as well as isolates from human cases of campylobacteriosis. The populations of veterinary and human isolates overlap, suggesting that most veterinary sources should be considered reservoirs of pathogenic campylobacters. There were some associations between source and sequence type complex, indicating that host or source adaptation may exist. The pig isolates formed a distinct group by MLST and may well represent a potential pig-adapted clone of C. jejuni. A subset (n = 82) of isolates was reanalyzed with a second MLST scheme which provided a unique set of isolates that had been analyzed at a total of 12 loci. The distribution of isolates among the complexes in each of the two schemes was similar but not identical. In addition to isolates from human outbreaks, one group of isolates that were not epidemiologically linked was also identical at all 12 loci. This group of isolates is believed to represent another stable strain of C. jejuni. 相似文献
114.
115.
116.
Influence of plant development and environment on transgene expression in potato and consequences for insect resistance 总被引:8,自引:0,他引:8
Down Rachel E. Ford Louise Bedford Simon J. Gatehouse Laurence N. Newell Christine Gatehouse John A. Gatehouse Angharad M.R. 《Transgenic research》2001,10(3):223-236
Clonal replicates of different transformed potato plants expressing transgene constructs containing the constitutive Cauliflower Mosaic Virus (CaMV) 35S promoter, and sequences encoding the plant defensive proteins snowdrop lectin (Galanthus nivalis agglutinin; GNA), and bean chitinase (BCH) were propagated in tissue culture. Plants were grown to maturity, at first under controlled environmental conditions, and later in the glasshouse. For a given transgene product, protein accumulation was found to vary between the different lines of clonal replicates (where each line was derived from a single primary transformant plant), as expected. However, variability was also found to exist within each line of clonal replicates, comparable to the variation of mean expression levels observed between the different clonal lines. Levels of GNA, accumulated in different parts of a transgenic potato plant, also showed variation but to a lesser extent than plant–plant variation in expression. With the majority of the clonal lines investigated, accumulation of the transgene product was found to increase as the potato plant developed, with maximum levels found in mature plants. The variation in accumulation of GNA among transgenic plants within a line of clonal replicates was exploited to demonstrate that the enhanced resistance towards larvae of the tomato moth, Lacanobia oleracea L., caused by expression of this protein in potato, was directly correlated with the level of GNA present in the plants, and that conditions under which the plants were grown affect the levels of GNA expression and subsequent levels of insect resistance. 相似文献
117.
118.
L.J. Seiderer R.C. Newell K. Schultes F.T. Robb C.M. Turley 《Journal of experimental marine biology and ecology》1987,110(3):213-224
Previous studies have shown that bacterioplankton are retained by the mussel Mytilus edulis (L.), and that lysozyme-like enzymes are associated with the crystalline style of the mussels. This study has demonstrated the presence of a lytic agent which is produced by bacteria associated with the crystalline style. The production of the agent is inhibited by chloramphenicol, and anaerobic growth conditions. The agent is heat-sensitive and nonfilterable. Attempts at the isolation of the agent in a cell-free extract have been unsuccessful. The presence of bacteria-like cells in the outer laminae of the crystalline style, coupled with the nonfilterable nature of the lytic agent, make it seem possible that these bacteria are responsible for lysis of gram-negative bacteria which are taken in with the food supply. 相似文献
119.
Francisco Barja Marie-Louise Chappuis Gilbert Turian 《FEMS microbiology letters》1993,107(2-3):261-266
Abstract Anti-actin drugs, cytochalasins A and B, inhibited both normal single, and benomyl-induced multiple, germ tube outgrowth from conidia of Neurospora crassa . Actin was cytochemically found to be concentrated in each of the benomyl-induced germ tube tips. No significant quantitative changes either in total actin or its isoforms were measured in the inhibitor-treated germlings. While intact microtubules are required for normal, monopolar axiation of the germ tube, they appear not to be necessary for benomyl-induced multipolar outgrowth which, in contrast, still requires intact actin microfilaments. Microfilaments and microtubules thus play complementary roles in the normal germination of conidia. 相似文献
120.