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   300篇
  免费   43篇
  国内免费   1篇
  2023年   2篇
  2021年   2篇
  2020年   3篇
  2018年   4篇
  2017年   8篇
  2016年   8篇
  2015年   6篇
  2014年   11篇
  2013年   13篇
  2012年   16篇
  2011年   9篇
  2010年   9篇
  2009年   8篇
  2008年   11篇
  2007年   16篇
  2006年   12篇
  2005年   12篇
  2004年   12篇
  2003年   10篇
  2002年   21篇
  2001年   5篇
  2000年   8篇
  1999年   5篇
  1998年   3篇
  1997年   10篇
  1996年   5篇
  1995年   5篇
  1994年   2篇
  1993年   4篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1988年   2篇
  1987年   6篇
  1986年   7篇
  1985年   7篇
  1984年   3篇
  1982年   4篇
  1981年   4篇
  1980年   2篇
  1977年   3篇
  1976年   3篇
  1954年   2篇
  1952年   10篇
  1951年   11篇
  1950年   8篇
  1943年   2篇
  1908年   3篇
  1903年   1篇
  1892年   1篇
排序方式: 共有344条查询结果,搜索用时 31 毫秒
91.
92.
Parkin KL  Kuo SJ 《Plant physiology》1989,90(3):1049-1056
Chilling at 4°C in the dark induced lipid degradation in cucumber (Cucumis sativa L.) fruit upon rewarming at 14°C. Rates of ethane evolution by fruits rewarmed after 3 days of chilling were up to four-fold higher than those evolved by unchilled (14°C) fruits (0.02-0.05 picomoles gram fresh weight−1 hour−1). This potentiation of lipid peroxidation occurred prior to irreversible injury (requiring 3 to 7 days of chilling) as indicated by increases in ethylene evolution and visual observations. Decreases in unsaturation of peel tissue glycolipids were observed in fruits rewarmed after 3 days of chilling, indicating the plastids to be the site of the early phases of chilling-induced peroxidation. Losses in unsaturation of tissue phospholipids were first observed only after chilling for 7 days. Phospholipase D activity appeared to be potentiated in fruits rewarmed after 7 days of chilling as indicated by a decrease in phosphatidylcholine (and secondarily phosphatidylethanolamine) with a corresponding increase in phosphatidic acid. These results indicate that lipid peroxidation may have a role in conferring chilling injury.  相似文献   
93.
94.
As part of continuing studies of Lyme disease, deer were surveyed during three hunting seasons in 1981 to obtain information on geographic distribution and density of I. dammini in New Jersey. I. dammini occurred throughout central and southern New Jersey. Four deer management zones (DMZs) were shown to have high tick densities. Geographical distribution and density data were independently regressed against 25 environmental and physical factors. Elevation was shown to be the most important factor in explaining the variability in both I. dammini distribution and density. Lyme disease cases were closely associated with the distribution of I. dammini and 57.3 percent of 117 Lyme disease cases occurred in the four DMZs previously identified as having the highest tick density.  相似文献   
95.
Six patients with the acquired immune deficiency syndrome (AIDS) had exacerbations or recurrences of previously quiescent atopic disease when they developed immunodeficiency. Four developed a different atopic illness from that suffered previously. Atopic symptoms developed within three months after the patients developed AIDS or during prodromal illness. Two of the patients were treated with recombinant interferon gamma: both showed a striking improvement in symptoms and cellular immunity. These results indicate that cellular immunity, through interferon gamma, may have a role in regulating atopic disease.  相似文献   
96.
97.
The parrot family consists of approximately 330 species, many of which are endangered due to habitat destruction and illegal trade. Microsatellite markers can provide important tools for examining both conservation and forensic issues in this family, and the availability of additional markers will prove useful for studies of other species in the parrot family. Parrots have proved a difficult family from which to develop microsatellites and cross-species amplification is generally lower than expected. This paper details 13 microsatellite loci isolated from the Moluccan Cockatoo and Cuban Amazon and their conservation in other species of parrots.  相似文献   
98.
Morrison LF  Parkin G  Codd GA 《Peptides》2006,27(1):10-17
Anabaenopeptins are commonly occurring bioactive peptides of cyanobacterial origin. Cyanobacteria (blue-green algae) are known to be capable of producing a large number of biologically active peptides, but the widespread occurrence of anabaenopeptins in particular, makes them ideal candidates for investigating the reasons that cyanobacteria produce such a complex spectrum of peptides and the wider implications of their natural function(s). Despite the identification of these peptides in cyanobacterial samples, little is known about the concentrations produced. For this reason, methods for the quantitative extraction of anabaenopeptins from lyophilized cyanobacterial cells were optimized. Higher yields of anabaenopeptins were obtained using aqueous methanol extraction than using water alone. However, repeat extractions using 50, 70 or 90% aqueous methanol did not result in significantly different total yields of the anabaenopeptin variants, ABPN-A and -B. Similarly, little difference was found in the quantification of purified ABPN-A and -B by high performance liquid chromatography with photodiode array detection (HPLC-PDA) when analyzed in methanol solutions of different concentrations. The effects of solvent concentration on the laboratory handling of ABPN-A and -B in glass and plastic containers were also investigated. Significantly lower concentrations of dissolved ABPN-A and -B were found when aqueous solutions came into contact with plastics, but not 50 or 100% methanol.  相似文献   
99.
Development of generic differentiation protocols that function in a range of independently-derived human embryonic stem cell (hESC) lines remains challenging due to considerable diversity in culture methods practiced between lines. Maintenance of BG01 and HUES-7 has routinely been on mouse embryonic fibroblast (MEF) feeder layers using manual- and trypsin-passaging, respectively. We adapted both lines to trypsin-passaging on feeders or on Matrigel in feeder-free conditions and assessed proliferation and cardiac differentiation. On feeders, undifferentiated proliferation of BG01 and HUES-7 was supported by all three media tested (BG-SK, HUES-C and HUES-nL), although incidence of karyotypic instability increased in both lines in BG-SK. On Matrigel, KSR-containing conditioned medium (CM) promoted undifferentiated cell proliferation, while differentiation occurred in CM containing Plasmanate or ES-screened Fetal Bovine Serum (FBS) and in unconditioned medium containing 100 ng/ml bFGF. Matrigel cultures were advantageous for transfection but detrimental to embryoid body (EB) formation. However, transfer of hESCs from Matrigel back to feeders and culturing to confluence was found to rescue EB formation. EBs formed efficiently when hESCs on feeders were treated with collagenase, harvested by scraping and then cultured in suspension in CM. Subsequent culture in FBS-containing medium produced spontaneously contracting EBs, for which the mean beat rate was 37.2 +/- 2.3 and 41.1 +/- 3.1 beats/min for BG01-EBs and HUES-7-EBs, respectively. Derived cardiomyocytes expressed cardiac genes and responded to pharmacological stimulation. Therefore the same culture and differentiation conditions functioned in two independently-derived hESC lines. Similar studies in other lines may facilitate development of universal protocols.  相似文献   
100.
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