全文获取类型
收费全文 | 460篇 |
免费 | 34篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 19篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 27篇 |
2014年 | 26篇 |
2013年 | 19篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 28篇 |
2007年 | 23篇 |
2006年 | 26篇 |
2005年 | 24篇 |
2004年 | 23篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1968年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有494条查询结果,搜索用时 15 毫秒
1.
Natan Medeiros Maciel Carlos Alberto Schwartz Guarino Rinaldi Colli Mariana Souza Castro Wagner Fontes Elisabeth N. Ferroni Schwartz 《Biochemical Systematics and Ecology》2006
This research tested the utility of two classes of skin secretion compounds to the phylogeny of the Bufo crucifer group. Skin secretions from specimens of nine populations of B. crucifer group were obtained and submitted to qualitative analysis. We observed a clear difference in the composition of the skin secretion molecules obtained from the species of Bufo studied. Fifty-nine molecules, 16 indolealkylamines and 43 proteins, were used as characters, and 39 of these were parsimonious informative. The tree topology of the skin secretion combined data showed areas of congruence and conflict when compared to an mtDNA phylogeny of the B. crucifer group. We used the Templeton test to evaluate the heterogeneity between the skin secretion and mtDNA data. Although not recommended, we performed a combined analysis with the two partitions. The skin secretion characters from the species of Bufo studied have phylogenetic signal. These data are indicative, at least as a preliminary study, of the phylogenetic relationships among the B. crucifer group taxa. 相似文献
2.
3.
4.
5.
Nitrogen-starved sunflower plants (Helianthus annuus L. cv. Peredovic) cannot absorb NO
3
–
or NO
2
–
upon initial exposure to these anions. Ability of the plants to take up NO
3
–
and NO
2
–
at high rates from the beginning was induced by a pretreatment with NO
3
–
. Nitrite also acted as inducer of the NO
2
–
-uptake system. The presence of cycloheximide during NO
3
–
-pretreatment prevented the subsequent uptake of NO
3
–
and NO
2
–
, indicating that both uptake systems are synthesized de novo when plants are exposed to NO
3
–
. Cycloheximide also suppressed nitrate-reductase (EC 1.6.6.1) and nitrite-reductase (EC 1.7.7.1) activities in the roots. The sulfhydryl-group reagent N-ethylmaleimide greatly inhibited the uptake of NO
3
–
and NO
2
–
. Likewise, N-ethylmaleimide promoted in vivo the inactivation of nitrate reductase without affecting nitrite-reductase activity. Rates of NO
3
–
and NO
2
–
uptake as a function of external anion concentration exhibited saturation kinetics. The calculated Km values for NO
3
–
and NO
2
–
uptake were 45 and 23 M, respectively. Rates of NO
3
–
uptake were four to six times higher than NO
3
–
-reduction rates in roots. In contrast, NO
2
–
-uptake rates, found to be very similar to NO
3
–
-uptake rates, were much lower (about 30 times) than NO
2
–
-reduction rates. Removal of oxygen from the external solution drastically suppressed NO
3
–
and NO
2
–
uptake without affecting their reduction. Uptake and reduction were also differentially affected by pH. The results demonstrate that uptake of NO
3
–
and NO
2
–
into sunflower plants is mediated by energy-dependent inducible-transport systems distinguishable from the respective enzymatic reducing systems.Abbreviations CHI
cycloheximide
- NEM
N-ethylmaleimide
- NiR
nitrite reductase
- NR
nitrate reductase
-
pHME
p-hydroxymercuribenzoate
This research was supported by grant PB86-0232 from the Dirección General de Investigatión Científica y Técnica (Spain). One of us (E.A.) thanks the Consejeria de Educación y Ciencia de la Junta de Andalucia for the tenure of a fellowship. We thank Miss G. Alcalá and Miss C. Santos for their valuable technical and secretarial assistance. 相似文献
6.
Marcelo V. Sousa Michael Richardson Wagner Fontes Lauro Morhy 《Journal of Protein Chemistry》1994,13(8):659-667
Enterolobin, a 55-kDa cytolytic, inflammatory, and insecticidal protein isolated from seeds of the Brazilian treeEnterolobium contortisiliquum (Leguminosae-Mimosoideae) has been further purified and partially sequenced by using both manual and automated methods. A computational search of enterolobin partial amino acid sequence against the PIR database revealed possible sequence similarities with aerolysins, cytolytic proteins fromAeromonas species. An alignment of enterolobin partial sequence to the amino acid sequences ofA. hydrophila andA. sobria aerolysins showed several similar regions with many residue identites. The seed protein enterolobin and the bacterial aerolysins may be homologous proteins despite the distant phylogenetic relationship. 相似文献
7.
8.
T. Macedo C. A. Fontes Ribeiro D. Cotrim P. Tavares M. T. Morgadinho M. Caramona M. T. Nunes Vicente L. Rodrigues M. G. Cardoso M. L. Keating 《Molecular neurobiology》1995,11(1-3):21-29
This work evaluated in a population of heroin and heroin plus cocaine human addicts:
- Norepinephrine (NE), epinephrine (Epi), and 3-methoxy-4-hydroxyphenylglycol (MHPG) (the principal metabolite of brain NE) plasma levels;
- Monoamine oxidase (MAO) activity; and
- 3H-imipramine specific binding to the amine carrier in platelets.
9.
Urea-Elicited Changes in Relative Electrophoretic Mobility of Certain Glycinin and beta-Conglycinin Subunits 下载免费PDF全文
Six molar urea in sodium dodecyl sulfate-polyacrylamide gels altered the relative electrophoretic mobility of several soybean protein subunits. Glycinin acidic polypeptide components A3 and A4 could be resolved from the other acidic polypeptides. A variant of the δ′ subunit of β-conglycinin was identified. 相似文献
10.
Characterization of an immunoglobulin binding protein homolog in the maize floury-2 endosperm mutant. 总被引:21,自引:8,他引:13
E B Fontes B B Shank R L Wrobel S P Moose G R OBrian E T Wurtzel R S Boston 《The Plant cell》1991,3(5):483-496
The maize b-70 protein is an endoplasmic reticulum protein overproduced in the floury-2 (fl2) endosperm mutant. The increase in b-70 levels in fl2 plants occurs during seed maturation and is endosperm specific. We have used amino acid sequence homology to identify b-70 as a homolog of mammalian immunoglobulin binding protein (BiP). Purified b-70 fractions contain two 75-kilodalton polypeptides with pl values of 5.3 and 5.4. Both 75-kilodalton polypeptides share several properties with BiP, including the ability to bind ATP and localization within the lumen of the endoplasmic reticulum. In addition, both b-70 polypeptides can be induced in maize cell cultures with tunicamycin treatment. Like BiP, the pl 5.3 form of b-70 is post-translationally modified by phosphorylation and ADP-ribosylation. However, modification of the pl 5.4 species was not detected in vitro or in vivo. Although the b-70 gene is unlinked to fl2, b-70 overproduction is positively correlated with the fl2 gene and is regulated at the mRNA level. In contrast, the fl2 allele negatively affects the accumulation of the major endosperm storage proteins. The physical similarity of b-70 to BiP and its association with abnormal protein accumulation in fl2 endoplasmic reticulum may reflect a biological function to mediate protein folding and assembly in maize endosperm. 相似文献