首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1232篇
  免费   101篇
  2022年   9篇
  2021年   14篇
  2020年   9篇
  2019年   14篇
  2018年   14篇
  2017年   10篇
  2016年   22篇
  2015年   48篇
  2014年   40篇
  2013年   57篇
  2012年   81篇
  2011年   83篇
  2010年   53篇
  2009年   42篇
  2008年   72篇
  2007年   69篇
  2006年   65篇
  2005年   61篇
  2004年   64篇
  2003年   60篇
  2002年   52篇
  2001年   22篇
  2000年   15篇
  1999年   12篇
  1998年   20篇
  1997年   10篇
  1996年   14篇
  1995年   16篇
  1994年   9篇
  1993年   11篇
  1992年   10篇
  1991年   16篇
  1990年   18篇
  1989年   20篇
  1988年   10篇
  1987年   12篇
  1986年   12篇
  1985年   15篇
  1984年   14篇
  1983年   12篇
  1982年   10篇
  1981年   9篇
  1980年   11篇
  1979年   9篇
  1978年   8篇
  1976年   10篇
  1975年   9篇
  1973年   5篇
  1972年   5篇
  1965年   6篇
排序方式: 共有1333条查询结果,搜索用时 46 毫秒
11.
Conclusion John Greene has dismissed the evolutionary ethics of Simpson as a case in which science was only a tool, a weapon, in defense of positions that were essentially religious and philosophical.57 This position adopts an amorphous view of science, in which a scientific theory can be construed to support practically any rhetorical position. The relationship between theory and rhetoric, however, is more complex; it is interactive, with the theory and the rhetoric influencing and supporting one another. It is no coincidence that Allee, Emerson, and Simpson all arrived at a biological basis of democracy and a naturalistic ethics during a period when the future of world politics and man's own morality were in question. Allee's commitment to world peace certainly antedated his theory of sociality, just as Simpson's commitment to democracy undoubtedly preceded his evolutionary views.By adopting a particular theory, however, the biologist necessarily imposes constraints on the corresponding rhetoric. Allee and Emerson could not, for example, have stressed the importance of the individual in democracy, given the orientation and framework of their biological research. There were differences among the social philosophies of Allee, Emerson, and Simpson; these differences depended, in part, on the specific evolutionary metaphors to which they subscribed. Allee's ideas with respect to cooperation were distinct from Emerson's, and both men differed strongly from Simpson on the role of the individual in evolution. The Chicago school was united by a conceptual framework that emphasized the population as the unit of selection, and the importance of cooperation in nature. But cooperation could play many roles: as a unifying principle for a theory of sociality, as an integrating mechanism in physiological functionalism, and as a biological source of hope for a society in the grips of a world war.  相似文献   
12.
The response of an established line of rat liver cells to thyroid hormone   总被引:1,自引:0,他引:1  
The response of an established line of non-transformed adult rat liver epithelial cells (ARL 15) to thyroid hormone (T3) (3,5,3'-triiodothyronine) was characterized. Exposure of confluent monolayers to 1.10(-8) M T3 for 3 days increased O2 consumption (QO2) between 14-58%, ouabain-sensitive Rb+ uptake 26%, (Na+ + K+)-ATPase activity 32%, alpha-glycerophosphate dehydrogenase activity 103% and cytochrome oxidase activity 208%. The ARL 15 cells, maintained in continuous culture, therefore, exhibit the hallmarks of an authentic physiological response to thyroid hormone.  相似文献   
13.
Abnormal low density lipoprotein metabolism in apolipoprotein E deficiency   总被引:2,自引:0,他引:2  
Apolipoprotein(apo) E deficiency is an inherited disease characterized by type III hyperlipoproteinemia and less than 1% normal plasma apoE concentration. The role of apoE in LDL metabolism was investigated by quantitating the metabolism of radiolabeled normal and apoE-deficient LDL in both normal and apoE-deficient subjects. ApoE deficiency resulted in an accumulation of plasma IDL, and a decreased synthesis of LDL consistent with a block in the conversion of IDL to LDL. The LDL isolated from the apoE-deficient patient was similar to normal LDL in hydrated density, size, and composition. However, the apoE-deficient LDL was kinetically abnormal with delayed catabolism in both normal subjects and the apoE-deficient patient. In addition, the catabolism of normal LDL in the apoE-deficient subject was increased. These results were interpreted as indicating that apoE is necessary for the conversion of IDL to LDL and the formation of kinetically normal LDL. The rapid catabolism of normal LDL in the apoE-deficient patient suggests an up-regulation of the hepatic LDL receptor pathway. Based on these results, apoE is proposed to play an important role in the conversion of IDL to LDL, the formation of kinetically normal LDL, and the regulation of LDL receptor function.  相似文献   
14.
Proapolipoprotein (apo-) A-II and several isoforms of apo-A-II including sialylated isoforms were identified in human plasma and thoracic duct lymph. Proapo-A-II secreted by HepG2 cells was identified by a combination of immunoblots and [14C]arginine incorporation. Proapo-A-II which contains 2 arginine residues could be readily differentiated from mature apo-A-II which contains no arginine. The pI of proapo-A-II is 6.79, whereas the pI of the major apo-A-II isoform in plasma and lymph is 4.90. Minor apo-A-II isoforms have pI values of 5.17, 4.68, 4.42, and 4.20, respectively. Sialoisoforms of apo-A-II were identified, which had a higher apparent molecular weight on sodium dodecyl sulfate-gel electrophoresis than the major isoform and disappeared following neuraminidase treatment. The relative quantity of proapo-A-II was relatively constant in lymph very low density lipoproteins, lymph high density lipoproteins, and plasma high density lipoproteins, whereas the sialoforms and the other minor isoforms of apo-A-II were greater in lymph very low density lipoproteins and the lowest in plasma high density lipoproteins.  相似文献   
15.
Biology and economics of growing seaweeds on land in a film culture   总被引:1,自引:1,他引:0  
  相似文献   
16.
Granular and liquid commercial humates, with micronutrients, and a microbial fermentation product were compared in several combinations with nematicides for their effects on cotton lint yield and root-knot nematode suppression. Fumigant nematicides effectively reduced cotton root galling caused by root-knot nematodes, and cotton lint yields increased. Organophosphates and carbamates were not effective. Occasionally, cotton lint yields were increased or maintained with combination treatments o f humates, micronutrients, and a microbial fermentation product, but galling o f cotton roots by root-knot nematodes was usually not reduced by these treatments.  相似文献   
17.
The reversible phosphorylation of microsomal 3-hydroxy-3-methylglutaryl CoA reductase in host liver and hepatoma 5123C has been investigated. The percentage of the total enzyme activity in vivo was similar in the normal liver, host liver and hepatoma 5123C. The inclusion of 30 mM EDTA and 10 mM mevalonic acid in assays of 3-hydroxy-3-methylglutaryl CoA reductase inactivation in vitro eliminated artifacts generated by the presence of mevalonate kinase. Inactivation of 3-hydroxy-3-methylglutaryl CoA reductase from normal liver, host liver and hepatoma occurred at a similar rate with similar half-times. We conclude that phosphorylation/dephosphorylation of 3-hydroxy-3-methylglutaryl CoA reductase occurs in hepatomas and that the lack of dietary cholesterol feedback inhibition in the hepatomas is not a result of a defect in this particular aspect of the reversible phosphorylation system.  相似文献   
18.
19.
20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号