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   321篇
  免费   26篇
  2023年   6篇
  2022年   2篇
  2021年   29篇
  2020年   11篇
  2019年   8篇
  2018年   5篇
  2017年   6篇
  2016年   6篇
  2015年   9篇
  2014年   6篇
  2013年   11篇
  2012年   18篇
  2011年   15篇
  2010年   7篇
  2009年   7篇
  2008年   10篇
  2007年   8篇
  2006年   6篇
  2005年   13篇
  2004年   9篇
  2003年   10篇
  2002年   11篇
  2001年   11篇
  2000年   4篇
  1999年   10篇
  1998年   3篇
  1997年   3篇
  1995年   3篇
  1992年   9篇
  1991年   11篇
  1990年   7篇
  1989年   6篇
  1988年   5篇
  1987年   4篇
  1986年   4篇
  1985年   9篇
  1984年   7篇
  1983年   6篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   4篇
  1976年   2篇
  1974年   3篇
  1970年   3篇
  1967年   2篇
  1956年   1篇
  1931年   1篇
  1930年   1篇
  1926年   1篇
排序方式: 共有347条查询结果,搜索用时 15 毫秒
101.
The cardinalia of strophomenids Lynnica fragilis gen. et sp. nov. and Sowerbyella (Sowerbyella) liliifera Öpik, 1930 from the Ordovician of the Leningrad Region are described in detail for different developmental stages. The study has revealed that the cardinal process of S. liliifera is bilobed unifid and the cardinal process of L. fragilis is bilobed trifid. L. fragilis gen. et sp. nov. is described.  相似文献   
102.
103.
104.
105.
106.
To study essential maternal gene requirements in the early C. elegans embryo, we have screened for temperature-sensitive, embryonic lethal mutations in an effort to bypass essential zygotic requirements for such genes during larval and adult germline development. With conditional alleles, multiple essential requirements can be examined by shifting at different times from the permissive temperature of 15°C to the restrictive temperature of 26°C. Here we describe 24 conditional mutations that affect 13 different loci and report the identity of the gene mutations responsible for the conditional lethality in 22 of the mutants. All but four are mis-sense mutations, with two mutations affecting splice sites, another creating an in-frame deletion, and one creating a premature stop codon. Almost all of the mis-sense mutations affect residues conserved in orthologs, and thus may be useful for engineering conditional mutations in other organisms. We find that 62% of the mutants display additional phenotypes when shifted to the restrictive temperature as L1 larvae, in addition to causing embryonic lethality after L4 upshifts. Remarkably, we also found that 13 out of the 24 mutations appear to be fast-acting, making them particularly useful for careful dissection of multiple essential requirements. Our findings highlight the value of C. elegans for identifying useful temperature-sensitive mutations in essential genes, and provide new insights into the requirements for some of the affected loci.  相似文献   
107.
Pharmacodynamic responses to drug treatment are often used to confirm drug-on-target biological responses. Methods ranging from mass spectrometry to immunohistochemistry exist for such analyses. By far, the most extensively used methodologies employ antigen-specific antibodies for detection (at a minimum) and, in some cases, target quantitation as well. Using a novel frequency-modulating technology from BioScale called acoustic micro magnetic particle (AMMP) detection, two pathway biomarkers were chosen for pharmacodynamic analysis and compared with either AlphaScreen or LI-COR Western blot assays. For these studies, pharmacodynamic biomarkers for both proteasome and phosphoinositol 3-kinase inhibition were used. Our results show clearly that the BioScale technology is a robust and rapid method for measuring recombinant standards or endogenously derived proteins from both tissue culture and mouse xenograft tumor lysates. Moreover, the sensitivity obtained with the BioScale platform compares favorably with LI-COR Western blot and AlphaScreen technologies. Furthermore, the use of the ViBE Bioanalyzer eliminates the labor-intensive effort of Western blot analysis and is devoid of the optical and other endogenous interfering substances derived from lysates of xenograft tumors typically observed with AlphaScreen.  相似文献   
108.
Uncarboxylated osteocalcin (uOC) is a circulating bone matrix protein, which has previously been shown to regulate glucose uptake and systemic metabolism. However, the cellular mechanism by which uOC acts has yet to be elucidated. C2C12 mouse myotubes were treated for 72 h with uOC (1–100 ng/mL). Cellular metabolism was analyzed using oxygen consumption and extracellular acidification rate. Metabolic gene and protein expression were measured via quantitative real-time polymerase chain reaction and Western blot, respectively. Additionally, C2C12 myotubes were treated with 10 ng/mL uOC to examine glucose uptake and activation of insulin signaling with or without insulin resistance. Finally, cellular lipid content was measured via Oil Red O and Nile Red staining. uOC treatment resulted in dose-dependent alterations of oxygen consumption with little effect on regulators of mitochondrial metabolism. Basal expression of regulators of glucose uptake were unaffected by uOC treatment. However, insulin-stimulated glucose uptake was blunted by uOC treatment with no concurrent alterations in insulin signaling. While chronic insulin treatment resulted in suppressed activation of Akt, concurrent uOC treatment was unable to prevent these detrimental effects on insulin signaling. uOC treatment had no effect on markers of lipogenesis and cellular lipid content. These findings suggest that 72-h uOC treatment may alter oxygen consumption without effect on regulators of mitochondrial biogenesis. Additionally, uOC treatment suppressed insulin-stimulated glucose uptake in cultured myotubes but had little effect on insulin signaling or regulators of cellular metabolism and was unable to mitigate insulin resistance.  相似文献   
109.
Artificial breeding programmes commonly lead to domestication, which is associated with many behavioural differences that can reduce the success of animals released into natural environments. To better understand the factors contributing to domestication, we used a captive population of Chinook salmon (Oncorhynchus tshawytscha) to partition hormonal and behavioural differences to effects of the breeding method and rearing environment. We compared 9‐mo‐old juveniles from three lines that shared a common genetic background: (1) the Channel line produced by natural spawning and reared in a low‐density environment with a natural substrate for approx. 6 mo before being transferred to the hatchery; (2) the Hatchery line produced by artificial spawning; and (3) the Transfer line produced by natural spawning but reared in the hatchery from the eyed‐egg stage. Plasma concentrations of 11‐ketotestosterone (11‐KT) and cortisol were measured in groups of 150 fish and again after 4 d of social interactions in groups of six fish. There was no difference in 11‐KT among lines in large groups, but in small groups, Transfer fish had lower 11‐KT concentrations and were significantly less aggressive than both Channel and Hatchery fish. Regardless of group size, concentrations of the stress hormone cortisol were nearly twofold higher in Channel fish than in Hatchery and Transfer fish. Furthermore, the elevated cortisol concentrations in Channel fish were associated with 35% lower feeding rates than in the other two lines. Our study details complex behavioural and hormonal responses to breeding method and rearing environment in juvenile salmon.  相似文献   
110.
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