全文获取类型
收费全文 | 888篇 |
免费 | 113篇 |
出版年
2020年 | 10篇 |
2019年 | 11篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 25篇 |
2013年 | 29篇 |
2012年 | 23篇 |
2011年 | 29篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 26篇 |
2007年 | 33篇 |
2006年 | 26篇 |
2005年 | 34篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 20篇 |
2001年 | 23篇 |
2000年 | 18篇 |
1999年 | 23篇 |
1998年 | 11篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1992年 | 12篇 |
1991年 | 23篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1980年 | 10篇 |
1979年 | 21篇 |
1977年 | 8篇 |
1976年 | 17篇 |
1975年 | 17篇 |
1974年 | 17篇 |
1973年 | 15篇 |
1972年 | 14篇 |
1971年 | 17篇 |
1970年 | 19篇 |
1969年 | 13篇 |
1968年 | 14篇 |
1967年 | 12篇 |
1966年 | 12篇 |
1965年 | 9篇 |
排序方式: 共有1001条查询结果,搜索用时 15 毫秒
51.
P C Harris R S Yamamoto J Crane G A Granger 《Journal of immunology (Baltimore, Md. : 1950)》1981,126(6):2165-2170
The present studies examine the various lymphotoxin (LT) forms released in vitro by phytohemagglutinin- (PHA) activated T-enriched (Te) human peripheral blood lymphocytes. It is clear that Te cells rapidly released (24 to 48 hr) these molecules in vitro. The 1st cell-lytic form detected in these supernatants is a 140-160,000 m.w. molecule(s) termed precursor alpha heavy (P alpha H). This form does not express alpha-LT antigenic determinants but is neutralized by antisera from animals injected with serum-free PHA-activated unseparated lymphocyte supernatants (anti-WS). The P alpha H is converted into alpha H, which expresses alpha determinants, by passage through molecular sieving columns or by treatment with low levels of Nonidet P-40 or urea. These treatments dissociate a small nontoxic 10-20,000 m.w. molecule(s), termed precursor factor (Pf), which masks the alpha-LT determinant on the P alpha H molecule. The dissociation of Pf is reversible, since alpha H from the molecular sieving columns will reassociate with the Pf. The alpha H LT class can further dissociate into the smaller alpha, beta, and gamma LT forms upon chromatography on a molecular sieving column, and a certain small percentage of the alpha H forms appear capable of associating to form the high m.w. complex (Cx) LT class. These findings suggest P alpha H may represent an intermediate that requires additional processing in order to proceed down 1 of 2 pathways: a) formation of complexes that are highly cell-lytic, or b) degradation by dissociation into the smaller weakly cell-lytic molecules identified as LT forms. 相似文献
52.
Eain M. Cornford Paul D. Crane Leon D. Braun William D. Bocash Anthony M. Nyerges William H. Oldendorf 《Journal of neurochemistry》1981,36(5):1758-1765
Abstract: 3-Indole ethanol has been recently identified as the hypnotic agent in trypanosomal sleeping sickness, and because it is formed in vivo after ethanol or disulfiram treatment, it is also associated with the study of alcoholism. When administered intraperitoneally to rats (250 mg/kg) tryptophol induced a sleep-like state that lasted less than an hour (no righting reflex was apparent 2 min after injection, but it returned at 11 min in bovine serum albumin solution, and 47 min in 40% ethanol solution). In ethanol solutions, tryptophol reduced brain cortical glucose utilization by 55% to the basal brain metabolic rate, and this effect lasted less than 1 h. Synergistic effects of tryptophol and ethanol were suggested by the observation that in albumin solution, tryptophol reduced brain glucose utilization by 35%, but a normal rate was not observed until 2 h postinjection. 相似文献
53.
The pattern of RNA synthesis of intracellular Trypanosoma cruzi amastigotes, immediately following infection of Lesch-Nyhan human fibroblasts, was studied by autoradiography. Amastigote RNA synthesis, determined by [3H]guanine incorporation, was not detected until 2 h after infection. At 8 h postinfection more than 90% of intracellular amastigotes were labeled. It was verified that extracellular trypomastigotes also synthesized RNA. Therefore it was concluded that, if RNA is required for trypomastigote-to-amastigote transformation, this nucleic acid is already present in the trypomastigotes before infection of the vertebrate cell. It is probable that the RNA synthesized by amastigotes during the prereplicative lag period (the period between initial infection and the onset of DNA synthesis) is required for intracellular growth and reproduction. 相似文献
54.
Isolation of brush border membranes in vesicular form from the intestinal spiral valve of the small dogfish (Scyliorhinus canicula). 总被引:2,自引:0,他引:2
A simple, rapid method for the preparation of purified brush border membranes in vesicular form from rabbit kidney proximal tubules has been applied with closely similar results to the intestinal spiral valve of the small dogfish (Scyliorhinus conicula). Since the dogfish belongs to one of the most ancient species of fish, it may be suggested that the method is generally applicable to all species later evolved which possess a brush border membrane at the mucosal surface of the cells of the intestine or kidney. 相似文献
55.
56.
57.
Lucian J. Cuprak Carol J. Lammi Janet I. Crane 《In vitro cellular & developmental biology. Plant》1979,15(11):900-909
Summary An improved basal medium is presented that requires only minimal supplementation with dialyzed fetal bovine serum or bovine
serum albumin and fetuin to be comparable to Ham's F-10, which requires 15% horse serum (HS) and 2.5% fetal bovine serum (FBS)
for the growth and function of Y-1, mouse adrenal cortex tumor, cells. Cell monolayers maintained for up to 2 weeks without
any protein supplementation have retained their steroid response to ACTH. The medium differs from Ham's F-10 in its buffer
composition and higher calcium-ion concentration. This medium should be a useful adjunct to studies pertaining to steroid
and lipid intermediary metabolism, the retention of a specialized physiological function in a chemically defined medium, and
the mechanism of hormonal response.
Supported by the Medical Research Service of the Veterans Administration. 相似文献
58.
J.E. Sireci A. Plotner R. Barr F.L. Crane 《Biochemical and biophysical research communications》1978,85(3):976-982
Selective inhibition of ferricyanide reduction in photosystem II by lipophilic thiols indicates a unique pathway of electron transport, which is not involved in reduction of class III acceptors or transfer of electrons to photosystem I. Both aromatic and aliphatic thiols induce the inhibition, but thiol binding reagents such as p-hydroxymercuribenzoate or N-ethylmaleimide do not inhibit. The inhibition can be observed using either dibromothymoquinone or bathophenanthroline to direct electrons away from photosystem I. No pretreatment of chloroplasts with thiols in the light was necessary to inhibit ferricyanide reduction by photosystem II or the O2 evolution associated with ferricyanide reduction. 相似文献
59.
Janet Banaszak Rita Barr Frederick L. Crane 《Journal of bioenergetics and biomembranes》1976,8(2):83-92
Various sites of ferricyanide reduction were studied in spinach chloroplasts. It was found that in the presence of dibromothymoquinone a fraction of ferricyanide reduction was dibromothymoquinone sensitive, implying that ferricyanide can be reduced by photosystem I as well as photosystem II. To separate ferricyanide reduction sites in photosystem II, orthophenanthroline and dichlorophenyl dimethylurea inhibitions were compared at various pH's. It was noted that at low pH ferricyanide reduction was not completely inhibited by orthophenanthroline. At high pH's, however, inhibition of ferricyanide reduction by orthophenanthroline was complete. It was found that varying concentration of orthophenanthroline at a constant pH showed different degrees of inhibition. In the study of ferricyanide reduction by photosystem II various treatments affecting plastocyanin were performed. It was found that Tween-20 or KCN treatments which inactivated plastocyanin did not completely inactivate ferricyanide reduction. These data support the conclusion that ferricyanide accepts electrons both before and after plastoquinone in photosystem II.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethyurea
- MV
methyl viologen
- DBMIB
2,5-dibromothymoquinone
- DMBQ
2,6-dimethyl benzoquinone
- OP
1,10-orthophenanthroline
- TMPD
tetramethyl-p-phenylenediamine
- PS 1
photosystem I
- PS II
photosystem II
- SN
sucrose-sodium chloride chloroplasts
Supported by NSF Grant BMS 74-19689. 相似文献
60.
Phosphorylation and DNA binding of nuclear rat liver proteins soluble at low ionic strength. 总被引:1,自引:0,他引:1
Proteins were extracted from isolated rat liver nuclei with 0.15 M NaCl and 0.35 M NaCl at pH 8.0. The number of phosphoproteins in these extracts was determined by labeling with 32P and autoradiography after two-dimensional gel electrophoresis. Two proteins, B22p and B24p, contained small amounts of 32P and sedimented with the 30S nuclear informofer particle. With the exception of two phosphoproteins, CB and CN', all of the phosphoproteins found in the 0.35 M NaCl extract. Approximately 20% of the 0.15 M NaCl soluble proteins bound to rat liver DNA in 0.05 M KCl-0.05 M Tris-HCl (pH 8). Of these proteins, 1-2% bound to DNA in 0.15 M KCl and were eluted with 2 M KCl. This DNA bound fraction which contained both phosphorylated and nonphosphorylated proteins was similar in both the 0.15 and 0.35 M NaCl extracts. However, two major proteins (C13 and C14) and three minor proteins (C15, C25, Cg') were present only in the 0.15 M NaCl extract. The results of the present study show that there are marked similarities in the two-dimensional gel electrophoretic, phosphorylation, and DNA binding properties of rat liver nuclear proteins soluble in either 0.15 or 0.35 M NaCl. 相似文献