全文获取类型
收费全文 | 410篇 |
免费 | 24篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2016年 | 5篇 |
2015年 | 16篇 |
2014年 | 12篇 |
2013年 | 29篇 |
2012年 | 30篇 |
2011年 | 20篇 |
2010年 | 18篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 26篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1931年 | 8篇 |
排序方式: 共有434条查询结果,搜索用时 15 毫秒
1.
2.
A Guha 《Journal of molecular biology》1971,56(1):53-62
3.
B Mukherji A Guha R Loomis M T Ergin 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(6):1987-1991
The cytotoxic host immune response toward autologous human cancer may be regulated by the immunoregulatory network. Here we show that helper T cells, cloned from peripheral blood lymphocytes that were sensitized in vitro against an autologous human malignant paraganglioma, proliferated against and made interleukin 2 when cocultured with the tumor-associated antigen in the presence of autologous accessory cells. Furthermore, the helper cell clones amplified cytotoxic immune response by peripheral blood lymphocytes against the paraganglioma cells in coculture with the blood lymphocytes and the paraganglioma cells. An autologous T cell line bearing suppressor phenotype, established from a lymph node that had been infiltrated with the paraganglioma tumor cells, in contrast to the helper cells, selectively suppressed the cytotoxic immune response by the blood lymphocytes against the paraganglioma cells in identical coculture. These results, therefore, demonstrate the existence of cell-mediated immunologic regulations of the cytotoxic immune response (concurrent amplification and suppression in the same host) against an autologous human tumor. 相似文献
4.
B Mukherji S A Wilhelm A Guha M T Ergin 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(5):1888-1892
The potential existence of down-regulation of cytotoxic immune response against an autologous human melanoma line was investigated as a possible explanation for cytotoxic unresponsiveness against the autologous melanoma cells. The melanoma cell line, PJ-M, was established and lymph node resident lymphocytes (LNL) were isolated from a lymph node which was partially infiltrated with the melanoma cells. Autologous peripheral blood lymphocytes (PBL) were sensitized in in vitro co-culture (IVC) against radiated PJ-M cells in the presence or absence of PJ-M-sensitized LNL and enriched suppressor (OKT8+) or inducer (OKT4+) LNL populations, and were assayed for cytotoxicity in a 4-hr 51Cr-release microcytotoxicity assay. Significant cytotoxic response against PJ-M could be generated in the PBL, but not in the LNL. The addition of sensitized, unfractionated LNL, OKT8+, or OKT4+ LNL populations abrogated cytotoxic response in the PBL against PJ-M. The suppression of cytotoxic response was induced selectively against the PJ-M targets, because IVC of PBL in the presence of the sensitized LNL did not affect the generation of polyclonal cytotoxic alloreactivities, nor did they abrogate the generation of cytotoxic response against allogeneic targets in IVC against the corresponding allogeneic targets. These results suggest the possibility that cytotoxic immune response against the autologous melanoma cells might have been suppressed by the individual's own immunoregulatory circuit. 相似文献
5.
The effects of mispair and nonpair correction in hybrid DNA on base ratios (G + C content) and total amounts of DNA 总被引:1,自引:0,他引:1
Base ratios and total DNA amounts can vary substantially between and within
higher taxa and genera, and even within species. Gene conversion is one of
several mechanisms that could cause such changes. For base substitutions,
disparity in conversion direction is accompanied by an equivalent disparity
in base ratio at the heterozygous site. Disparity in the direction of gene
conversion at meiosis is common and can be extreme. For transitions (which
give purine [R]/pyrimidine [Y] mispairs) and for transversions giving
unlike R/R and Y/Y mispairs in hybrid DNA, this disparity could give slow
but systematic changes in G + C percentage. For transversions giving like
R/R and Y/Y mispairs, it could change AT/TA and CG/GC ratios. From the
extent of correction direction disparity, one can deduce properties of
repair enzymes, such as the ability (1) to excise preferentially the purine
from one mispair and the pyrimidine from the other for two different R/Y
mispairs from a single heterozygous site and (2) to excise one base
preferentially from unlike R/R or Y/Y mispairs. Frame-shifts usually show
strong disparity in conversion direction, with preferential cutting of the
nonlooped or the looped-out strand of the nonpair in heterozygous h-DNA.
The opposite directions of disparity for frame-shifts and their intragenic
suppressors as Ascobolus suggest that repair enzymes have a strong,
systematic bias as to which strand is cut. The conversion spectra of
mutations induced with different mutagens suggest that the nonlooped strand
is preferentially cut, so that base additions generally convert to mutant
and deletions generally convert to wild-type forms. Especially in
nonfunctional or noncoding DNA, this could cause a general increase in DNA
amounts. Conversion disparity, selection, mutation, and other processes
interact, affecting rates of change in base ratios and total DNA.
相似文献
6.
Summary Irradiated styrene-grafted cellulose acetate membrane was used for the separation of ethanol by reverse osmosis. Ethanol separation from molasses based fermentation broth resulted in separation efficiency of 90% at an operating pressure of 1400 psig. Lower permeate flux was observed with fermented broth compared to aqueous ethanol. 相似文献
7.
A Guha W Szybalski W Salser E P Geiduschek J F Pulitzer A Bolle 《Journal of molecular biology》1971,59(2):329-349
8.
9.
10.
The use of C14-labelled substrate in histochemical demonstration of different forms of phosphorylase
Active and total phosphorylase activity, using labelled C14-glucose-1-phosphate as the substrate, is demonstrated by histoautoradiographic method. This method can demonstrate the polysaccharide
synthesizedin vitro by phosphorylase without intervention from the unlabelled pre-existing glycogen.
C14-glucose can not replace C14-glucose-1-phosphate as substrate.
The distribution of phosphorylase in tissue sections, except in cases of very low activity, is similar to that obtained by
customary dilute Lugol's iodine staining method. The relative difference of intensity between active and total phosphorylase,
as revealed by iodine staining, is also reflected by histoautoradiographic method.
Histoautoradiographic method has several advantages over the iodine staining method. This method is more sensitive for demonstration
of very low phosphorylase activity which may escape detection by iodine staining. Branching enzyme activity, especially when
it favors synthesis of glycogen type of polysaccharide instead of amylopectin type, can be better detected by this method.
Active phosphorylase substrate medium can be used to demonstrate this activity in plant tissues, where the presence of pre-existing
starch often prohibits the use of iodine staining method.
Stripping film method for autoradiography is recommended for the study of this enzyme activity. 相似文献