全文获取类型
收费全文 | 1204篇 |
免费 | 98篇 |
国内免费 | 1篇 |
专业分类
1303篇 |
出版年
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 39篇 |
2014年 | 41篇 |
2013年 | 56篇 |
2012年 | 75篇 |
2011年 | 52篇 |
2010年 | 57篇 |
2009年 | 33篇 |
2008年 | 50篇 |
2007年 | 41篇 |
2006年 | 52篇 |
2005年 | 42篇 |
2004年 | 43篇 |
2003年 | 36篇 |
2002年 | 37篇 |
2001年 | 38篇 |
2000年 | 44篇 |
1999年 | 31篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 25篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1970年 | 8篇 |
排序方式: 共有1303条查询结果,搜索用时 0 毫秒
11.
M Dodeur S Coumoul D Durand G Durand J Feger J Agneray 《Biochemical and biophysical research communications》1983,115(1):82-86
The total capacity of hepatocytes to bind asialoorosomucoid was measured on normal and streptozotocin diabetic rats. 4 days after the streptozotocin injection, a slight decrease of total receptor concentration was observed while a more marked reduction of cell surface receptor occurred. In animals sacrificed 11 days after the streptozotocin injection, the total capacity of hepatocytes to bind asialoorosomucoid was about 70% of the normal level. 相似文献
12.
13.
T S Elton C C Stephan G R Taylor M G Kimball M M Martin J N Durand S Oparil 《Biochemical and biophysical research communications》1992,184(2):1067-1073
A rat genomic Southern blot, probed with a type I angiotensin II receptor probe, demonstrated that two highly homologous type I angiotensin II receptors were present. A rat genomic library was subsequently screened and four clones were isolated. From restriction mapping, differential hybridization, polymerase chain reaction amplification and sequence analyses we have determined that there are two unique type I angiotensin II receptor genes. The first of these genes corresponds to the published rat vascular complementary DNA sequence; the second, corresponds to a novel receptor not previously described. 相似文献
14.
Bacterial host specificity of Lucinacea endosymbionts: Interspecific variation in 16S rRNA sequences 总被引:2,自引:0,他引:2
Abstract Three tropical lucinid clams ( Codakia orbiculata, Codakia pectinella and Lucina nassula ) from a shallow coastal environment have been studied regarding to their thioautotrophic bacterial endosymbionts. The 16S rRNA genes (rDNA) from these three endosymbionts were amplified using PCR. Phylogenetic analysis by distance matrix and parsimony methods always placed the newly examined symbionts within the monophyletic group composed of symbionts of the bivalve superfamily Lucinacea. A same single 16S rRNA sequence was found in C. orbiculata and C. pectinella and was identical to that found in C. orbicularis and Linga pensylvanica , two other lucinids living in the same type of environment. These data indicate that a same symbiont species may be associated with different host species. Lucina nassula hosts a symbiont with a distinct 16S rDNA sequence, but very closely related to the former. 相似文献
15.
Na+-K+ Exchange at the Xylem/Symplast Boundary (Its Significance in the Salt Sensitivity of Soybean) 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigated the mechanism of Na+ reabsorption in exchange for K+ at the xylem/symplast boundary of soybean roots (Glycine max var Hodgson). The xylem vessels of excised roots were perfused with solutions of defined composition to discriminate between entry of ions into or reabsorption from the xylem vessels. In the presence of NaCl, the transport systems released K+ into the xylem sap and reabsorbed Na+. The Na+-K+ exchange was energized by proton-translocating ATPases, enhanced by external K+ concentration, and dependent on the anion permeability. Evidence was presented for the operation of H+/Na+ and H+/K+ antiporters at the xylem/symplast interface. 相似文献
16.
The fungal solubilization of cell wall components of sugar-beet pulp, during solid-state fermentation of Thermoascus aurantiacus, is reported here. The extracellular fungal enzyme activities related to the substrate degradation were also studied. In
120 h, more than 60% of the main sugar-beet pulp polysaccharides, i.e. pectins, arabinose- and glucose-containing polysaccharides,
were rapidly brought into solution by the fungus. The slow accumulation of monosaccharides compared to the fast degradation
of the polysaccharides suggested that most of the released sugars were consumed by the fungus. The analysis of the enzymes
present in the water extracts of the solid-state cultures proved that the fungus was able to synthesize a complete enzymatic
system required for the hydrolysis of the main sugar-beet pulp polysaccharides. The highest enzyme activities measured were
β-glucosidase and α-L-arabinofuranosidase.
Received: 22 September 1995/Received revision: 15 January 1996/Accepted: 22 January 1996 相似文献
17.
18.
19.
Laurent Beuf Sylvie Bédu Marie-Claire Durand Françoise Joset 《Plant molecular biology》1994,25(5):855-864
The involvement of a gene ofSynechocystis PCC6803,icfG, in the co-ordinated regulation of inorganic carbon and glucose metabolism, was established. TheicfG gene codes for a 72 kDa protein, which shows no homology with those registered in data libraries. Expression oficfG required glucose, the actual inducer probably being glucose-6-phosphate, and was independent of light and of the external inorganic carbon concentration. Mutants carrying an inactivated copy oficfG were constructed. Their growth characteristics were identical to those of the wild type under all regimes except in limiting inorganic carbon with glucose being present either before or after the transfer to the limiting conditions. These conditions completely prevented growth, both in the light and in the dark. The inhibition could be relieved by several intermediates of the tricarboxylic acid cycle. Assays of various enzymic activities related to inorganic carbon uptake and to its assimilationvia either the Calvin cycle or phosphoenolpyruvate carboxylase did not reveal the level of action of IcfG. Possible models include a blockage of the assimilation of both carbon sources in the absence of IcfG, or the inhibition of Ci incorporation route(s) essential under limiting inorganic carbon conditions, even when glucose is present, and even in the dark. 相似文献
20.
Effect of an n-3 Fatty Acid-Deficient Diet on the Adenosine-Dependent Melatonin Release in Cultured Rat Pineal 总被引:1,自引:1,他引:0
N. Gazzah A. Gharib I. Delton P. Molière G. Durand R. Christen M. Lagarde N. Sarda 《Journal of neurochemistry》1993,61(3):1057-1063
Abstract: We studied the effect of a diet deficient in n-3 fatty acids on the adenosine-dependent melatonin release from cultured rat pineal gland after stimulation by 5'- N -ethylcarboxamidoadenosine (NECA), an A2 adenosine agonist. Experiments were conducted with 2-month-old rats raised on semipurified diets containing either peanut oil (n-3 deficients) or peanut plus rapeseed oil (controls). The proportion of docosahexaenoic acid (22:6 n-3) in the pineal total lipid fraction and in phosphatidylcholine and phosphatidylethanolamine was significantly decreased in n-3-deficient rats. This was compensated for partially by an increase in 22:4 n-6 and 22:5 n-6 levels. The activity of the cultured rat pineal, in terms of cyclic AMP content and N -acetylserotonin and melatonin release in the medium, was lower after stimulation by 10-5 mol/L NECA in the group fed peanut oil than in the group fed peanut plus rapeseed oil. The increased ratio of n-6/n-3 fatty acids in pineal total lipids and the major glycerophospholipids (phosphatidylcholine and phosphatidylethanolamine) may have an important influence on the rat pineal responses. The results are discussed in the context of changes in membrane-bound proteins, including enzymes and/or receptors involved in the rat pineal gland function. 相似文献