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   617篇
  免费   44篇
  661篇
  2021年   8篇
  2019年   6篇
  2017年   6篇
  2016年   13篇
  2015年   12篇
  2014年   14篇
  2013年   21篇
  2012年   28篇
  2011年   19篇
  2010年   12篇
  2009年   6篇
  2008年   20篇
  2007年   14篇
  2006年   14篇
  2005年   16篇
  2004年   17篇
  2003年   18篇
  2002年   18篇
  2001年   20篇
  2000年   21篇
  1999年   20篇
  1998年   11篇
  1996年   7篇
  1995年   6篇
  1994年   6篇
  1992年   8篇
  1991年   12篇
  1990年   18篇
  1989年   17篇
  1988年   9篇
  1987年   8篇
  1985年   5篇
  1984年   11篇
  1983年   9篇
  1982年   15篇
  1981年   9篇
  1979年   8篇
  1978年   10篇
  1977年   7篇
  1976年   6篇
  1975年   8篇
  1974年   10篇
  1973年   7篇
  1972年   11篇
  1971年   7篇
  1968年   4篇
  1967年   9篇
  1966年   7篇
  1964年   7篇
  1960年   4篇
排序方式: 共有661条查询结果,搜索用时 15 毫秒
621.
622.
M. McGregor 《CMAJ》1971,105(11):1139
  相似文献   
623.
624.
Larvae of the yellow mealworm, Tenebrio molitor L., Gembloux strain, race F, were reared on diets in which the protein component was supplied by defatted ground seed, defatted ground dehulled fraction, or defatted ground hulls of Brassica napus L. cv. Tower or Brassica campestris L. cv. Candle, obtained from autoclaved seed. They were also fed casein diets to which defatted ground hulls of Tower or Candle seed were added. Gain in weight was equally good for all diets containing Candle seed fractions and for diets containing Tower ground seed. However, it was lower for diets containing the ground dehulled fraction or the ground hulls of Tower. Addition of Candle hulls or of a mixture of equal proportions (w/w) of Candle and Tower hulls to diets containing dehulled Tower did not improve the gain in weight of larvae, compared with that of larvae fed diets containing the dehulled fraction, alone. Similar additions of Tower hulls or of the mixture to diets containing the dehulled fraction of Candle had no adverse effect on larval gain in weight, compared to that registered by larvae fed the dehulled fraction of Candle. Significant improvement in weight gain in comparison with that recorded for larvae fed the unsupplemented casein diet could not be demonstrated when ground hulls of Tower or Candle were added to this diet. Considered collectively, weight gains of larvae of T. molitor were consistently greater when Candle products were fed than when Tower products provided the protein fraction of the diet.  相似文献   
625.
626.
In a prospective study designed to assess the influence of bromocriptine on pituitary tumour size 12 patients with pituitary tumours, eight of whom had suprasellar extensions, were treated for three months with 20 mg of bromocriptine daily after a gradual increase to this dose. The group comprised eight women and four men, five with prolactin-secreting adenomas, four with acromegaly, two with functionless adenomas, and one with Nelson''s syndrome. All five patients with prolactin-secreting adenomas showed a reduction in pituitary tumour size as assessed by computerised tomography and metrizamide cisternography accompanied by a fall in prolactin concentrations and clinical and biochemical improvement in their hypopituitarism. One patient in this group had a visual-field defect before treatment, and this resolved. There was no radiological evidence of reduction in tumour size in the remaining seven patients, though this might refect the fairly short duration of treatment, particularly in view of the ancillary evidence of clinical, biochemical, and visual-field improvement in some of the patients. These results emphasise the potential value of bromocriptine in treating patients with large prolactinomas or recurrences of such tumours after previous chiasmal decompression and conventional external megavoltage irradiation on the pituitary.  相似文献   
627.
Summary The development of common scab on potato crops growing in slightly acid to neutral soils has been shown to be greatly reduced by application of manganese sulphate to the soil at planting time. A general improvement in health and appearance of tubers was noted and increased yields of marketable tubers were obtained. The possibility that environmental factors known to influence the development of scab are only important in so far as they affect the solubility of soil manganese is discussed.  相似文献   
628.
Cytotoxic thymus-derived lymphocytes (CTL) generated in vitro by restimulating rat cells with Listeria antigen- (LMA) pulsed syngeneic accessory cells were characterized in respect to their surface membrane markers. LM-dependent CTL were devoid of detectable surface immunoglobulin (Ig) and receptors for the Fc region of rabbit IgG. Experiments with monoclonal antibodies to rat T cell markers revealed that these cytotoxic cells have the phenotypic profile W3/13+, W3/25-, MRC OX 8+. LM-dependent CTL also bind the monoclonal antibody, MRC OX 3, which recognizes an Ia-antigen-like determinant on rat cells. Although LM-dependent CTL lack the W3/25 marker, their generation depends on the cooperative interplay of W3/25+ and W3/25- T cells.  相似文献   
629.
In man, manganese neurointoxication is characterised in the early phase by behavior reminiscent of that observed in schizophrenia. During chronic manganese intoxication the neuropsychiatric symptoms manifested earlier disappear and are followed by a permanent neurological phase typified by extrapyramidal symptoms similar to those of Parkinson's disease. Study of manganese intoxication in animals may provide important clues towards elucidation of the biochemical defect underlying neuropsychiatric as well as extrapyramidal disease. Investigations in our laboratory suggest that neurotoxicity of manganese is an exaggeration of function in normal neuronal homeostasis. Manganese neurointoxication in neonatal rats resulted in significant depression of lipid peroxidation in several rat brain regions examined. In the striatum, lipid peroxidative activity was abolished, an effect which may be related to alteration in neurotransmitters often observed in the striatum of manganese treated rats. The chronic, extrapyramidal stage of manganism, may ensue when excess Mn2+ is oxidised to higher valency forms where it can potentiate the autoxidation of catecholamines, like dopamine, resulting in concomitant formation of free radicals and cytotoxic quinones. This latter effect may arise preferentially in the substantia nigra, where neuromelanin is formed nonenzymatically by autoxidation of dopamine.  相似文献   
630.
Deakin (1967b) suggested that flow of blood might obey a law of minimal energy dissipation. The present paper presents a simpler derivation of Deakin’s equations pointing out several previously unrecognized features. It is shown that these equations are unlikely to be applicable. In particular, the solution obtained by Deakin and Jones (1968) does not yield a true minimum for energy dissipation. The solution for which energy dissipation is actually minimized is shown to possess features which render it unlikely to apply to a real flow.  相似文献   
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