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   6169篇
  免费   452篇
  国内免费   1610篇
  8231篇
  2024年   29篇
  2023年   196篇
  2022年   249篇
  2021年   295篇
  2020年   312篇
  2019年   316篇
  2018年   258篇
  2017年   237篇
  2016年   270篇
  2015年   247篇
  2014年   295篇
  2013年   489篇
  2012年   287篇
  2011年   274篇
  2010年   243篇
  2009年   397篇
  2008年   413篇
  2007年   388篇
  2006年   335篇
  2005年   291篇
  2004年   234篇
  2003年   214篇
  2002年   191篇
  2001年   221篇
  2000年   184篇
  1999年   176篇
  1998年   124篇
  1997年   123篇
  1996年   102篇
  1995年   116篇
  1994年   93篇
  1993年   75篇
  1992年   82篇
  1991年   64篇
  1990年   50篇
  1989年   48篇
  1988年   30篇
  1987年   27篇
  1986年   29篇
  1985年   43篇
  1984年   31篇
  1983年   15篇
  1982年   20篇
  1981年   17篇
  1980年   12篇
  1979年   11篇
  1977年   15篇
  1976年   16篇
  1975年   18篇
  1974年   12篇
排序方式: 共有8231条查询结果,搜索用时 0 毫秒
161.
对致病性暗色霉中的着色霉(Fonsecaea Negroni)外瓶霉(Exophiala Charmichael)瓶霉(Phialophoro Medlar)中的五种真菌浆膜超微结构进行了冰冻蚀刻研究,发现裴氏着色霉(Fonsecaea pedrosoi)和紧密着色霉(F.compacta)的内折长而宽,较深,略有弯曲,数量少,多呈平行或垂直排列。皮炎外瓶霉(Exophiala dermatitidis)的内折数量多,密集而分布均匀,呈圆点状或圆棒状。棘状外瓶霉(Exophiala spinifera)的内折少而表浅,多为圆形。疣状瓶霉(Phialophora verrucosa)的内折数量,排列,形状无一定规律。据上述特征,着色霉可以与外瓶霉,疣状瓶霉区别开来,皮炎外瓶霉也可与棘状外瓶霉区分。浆膜超微结构的性状有一定的分类学意义。  相似文献   
162.
庄剑云  魏淑霞 《菌物学报》1992,11(Z1):131-133
裸堆串孢锈菌属以冬孢子单孢串生为主要特征,孢子堆裸露缺包被,外观酷似柄锈属的孢子堆。此属已知7种。寄生于菊科,大戟科和荨麻科植物,6种分布美洲,1种分布东亚.本文报告亚洲仅知的一种,即寄生于宽叶孢麻Urtica laetevirens Maxim.的川息尔堆串孢锈菌Baeodromus tranzschelii Azbukina,标本采自四川九寨沟(岷山).  相似文献   
163.
本文是26篇关于丝状真菌基因表达系统的研究论文的综述,包括两部份内容。前一部分叙述1979年开始建立并迅速发展起来的丝状真菌转化系统,着重介绍丝状真菌中转化系统的构建及转化的一般特点。后一部分叙述在转化系统发展基础上产生的丝状真菌基因工程,文中列出了截至1991年9月为止报道的一些成功的实例,说明它在丝状真菌工业育种和作为外源基因产物的生产和分泌系统中的应用。  相似文献   
164.
The occurrence and distribution of lignicolous marine fungi in the Straits of Messina has been studied. Using submerged panels of pine, beech and poplar, twenty fungal species were identified. The lignicolous mycoflora of the Messina Straits was not significantly different from that reported in the literature for other temperate marine coastal environments, Ascomycotina being frequent, while Basidiomycotina were rare.  相似文献   
165.
Both components of the polyamine oxidase (PAO)-polyamine system are known to be present in phagocytes and have thus been postulated to contribute to the antimicrobial activity of these cells. Therefore, the effects of the PAO-polyamine system on three medically important opportunistic fungi were examined. Yeasts of Cryptococcus neoformans, but not Candida albicans blastoconidia or Aspergillus fumigatus conidia, were efficiently killed by the system. Two putative end products of the system, hydrogen peroxide and acrolein, both killed C. neoformans at concentrations attainable with the whole system. However, catalase failed to inhibit activity of the whole system, making hydrogen peroxide an unlikely mediator of killing. Although C. albicans blastoconidia and A. fumigatus conidia were not killed by the PAO-polyamine system, germ tube formation by the former, and hyphal growth by the latter, were markedly inhibited. These data establish that the PAO-polyamine system possesses antifungal activity.  相似文献   
166.
Total patterns of water-soluble proteins of 35 strains (7 species) of Galactomyces and Dipodascus strains with their respective Geotrichum anamorphs are compared. Quantitative differences among a number of species are found with iso-electric focusing; bands that characterize species are selected. Qualitative differences are found between the teleomorph genera.  相似文献   
167.
Metabolism of vanillic acid, a product of lignin degradation, has been studied in selected representatives of soft-rot, brown-rot and white-rot fungi. All of the brown-and white-rot species examined decarboxylated vanillate to methoxyhydroquinone oxidatively. Mycelium extracts of all these fungi, except Pleurotus ostreatus contained high levels of an NAD(P)H-dependent vanillate hydroxylase. P. ostreatus also released 14CO2 from 14COOH-vanillate but by a different mechanism possibly involving phenoloxidases. Most of these fungi also contained a dioxygenase which catalysed the intra-diol cleavage of hydroxyquinol (1,2,4-trihydroxybenzene) to form maleylacetate. No 3-O-demethylase activity was detected, and data indicate that in some of the fungi examined cleavage of the aromatic ring occurs without prior removal of the methoxyl group. None of the soft-rot fungi tested contained vanillate hydroxylase or hydroxyquinol 1,2-dioxygenase, but very low levels of protocatechuate 3,4-dioxygenase were detected in mycelium extracts. Vanillate catabolism among members of this group occurs via a different route which may involve ring demethylation although no 3-O-demethylase activity was detected in this study. The enzyme NAD(P)H-quinone oxidoreductase was demonstrated to exist in all the studied groups of fungi.  相似文献   
168.
The activation of the carotene biosynthetic pathway in Blakeslea trispora was found to occur by trisporic acid and many other compounds such as abscisic acid, β-ionone, α-ionone and vitamin A which share significant structural similarity with trisporic acid. The magnitude of stimulatory activities of these effectors was in the order trisporic acid > abscisic acid > β-ionone > α-ionone > vitamin A. Comparison of structures and stimulatory activities of all the effectors indicated that the short length of the side chain and the presence of a keto group in the ring structure of the trisporic acid molecule contributed significantly to the biological activity towards carotenogenesis.  相似文献   
169.
The relationship between the respiration and the presence and utilization of endogenous and exogenous substrates was studied in the non-filamentous obligately marine fungus Thraustochytrium aureum. Using isotopic and manometric methods, it was shown that almost all exogenous glucose is assimilated, whilst almost all the oxygen consumption in the presence of exogenous glucose was due to oxidation of endogenous reserves. In contrast, exogenous glutamate, which cannot serve as the sole carbon source for growth, inhibits respiration of endogenous materials, and is itself rapidly oxidized. The uncoupler 2,4-dinitrophenol stimulates the oxidation of endogenous reserves without affecting the uptake and use of exogenous glucose. These data strongly support the idea of physiologic compartmentation in this organism.  相似文献   
170.
Numbers of fungi were determined in water and sediment samples from a virgin salt-fresh water transect at North Point, James Bay. Fungal densities in the water samples showed an approximately linear increase from 28–70 CFU/100 ml, at the salt water extremity of the transect, to 13–16,000 CFU/100 ml at the freshwater extremity. Sediment fungal densities were also higher in the inland samples. There was no apparent difference between the numbers of fungi estimated using enumeration media prepared with distilled or saline water. Data are discussed in relation to the physical, chemical and organic status of the water, the nature of the surrounding vegetation and possible sources of the enumerated fungi.  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