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   6150篇
  免费   454篇
  国内免费   1598篇
  2024年   26篇
  2023年   193篇
  2022年   234篇
  2021年   295篇
  2020年   305篇
  2019年   316篇
  2018年   258篇
  2017年   236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8202条查询结果,搜索用时 15 毫秒
981.
Toledo  Gerardo  Rojas  Adriana  Bashan  Yoav 《Hydrobiologia》2001,444(1-3):101-109
Black mangrove (Avicennia germinans) seedlings (n=555) were grown from field-collected propagules for 3 months in a new type of terrestrial nursery. They were grown in clusters of five plants, and then they were transplanted to a clear-cut zone in a lagoon fringed by a mangrove forest at Laguna de Balandra, Baja California Sur, Mexico. Survival and plant development of transplants were monitored at 6-monthly intervals for 2 years. After 1 month, the survival of seedlings was 96%, later stabilizing at approximately 77%. After 24 months, 74% of the plants were still alive. The best cluster, showing maximum growth under mangrove swamp conditions in this arid zone, was a two-plant cluster. The lagoon has a low natural regeneration rate of 48 plants per 350 m2 per 6 years of monitoring. This study shows the feasibility of restoring destroyed arid-coast lagoons with black mangroves.  相似文献   
982.
Venkateswara Sarma  V.  Hyde  K. D.  Vittal  B. P. R. 《Hydrobiologia》2001,455(1-3):41-53
This paper describes the frequency of occurrence and biodiversity of fungi from mangroves of the Godavari and Krishna deltas, on the east coast of India. Seventy three species were identified from Godavari and 67 from the Krishna mangroves. Fifty five species were common to both sites, 18 were found only at Godavari and 12 at Krishna mangroves. Verruculina enaliawas found to be very frequent at both sites with a higher frequency of occurrence at Godavari. Eutypa bathurstensis was very frequent at Godavari but only frequent at Krishna. Cirrenalia pygmea and Cryptosphaeria mangrovei were frequent at the Godavari mangrove, but were recorded occasionally at Krishna. Decaying samples of Rhizophora and Avicennia were studied in detail. Forty three species were common to both hosts, while 22 species were recorded only from Avicennia and 20 only from Rhizophora. Verruculina enalia was the only very frequent fungus recorded on both hosts with a lower percentage occurrence (14.8%) on R. apiculata as compared to Avicennia spp. (24.3%). Eutypa bathurstensis was the next most frequent fungus on Avicennia, while Rhizophila marina was next most frequent on Rhizophora. Dactylospora haliotrepha which was recorded frequently on Rhizophorawas infrequent on Avicennia.  相似文献   
983.
984.
Okada  H.  Ferris  H. 《Plant and Soil》2001,234(2):253-262
Dish and column microcosms containing alfalfa-sand medium were established to determine effect of temperature on growth and N mineralization ability of two fungi (Rhizoctonia solaniand Botrytis cinerea) and two nematodes (Aphelenchus avenaeand Aphelenchoides composticola). The microcosms were incubated at 15, 20, 25 and 29 °C for 21 days. In the dish microcosms, hyphal growth rates of both fungal species increased with temperature in the range of 15–25 °C. Above that temperature range, the growth rate of R. solani remained almost constant while that of B. cinereadecrease considerably. The population growth rate of A. avenae increased with temperature between 15 and 29 °C on colonies of R. solani and B. cinerea in dish microcosms. The growth rate of A. composticola also increased in the range of 15–25 °C but decreased greatly beyond that temperature range independent of the fungal species as food source. Inorganic N (NH4 + + NO3 ) was collected from each column microcosm by leaching every 3 days. In the columns containing R. solani, there was a significant effect of temperature on the amount of N detected in the fungus+A avenaeor A. composticolabut not in the fungus alone columns. The total amount of N was greatest at 29 °C for A. avenaeand at 20 °C for A. composticola columns, concurrent with the population growth rates of the nematodes. In the columns containing B. cinerea, the effect of temperature on the amount of inorganic N was not significant in either the fungus alone or fungus+nematode columns, although the population growth rates of the both nematode species were highest at 20 °C. For B. cinerea, the N amount across temperatures was the same or larger for the fungus alone as for the fungus+nematode columns. In general, the contribution of fungal-feeding nematodes to N mineralization was small in any combinations of fungus and nematode species at any temperature. Similarity in C/N ratio of the fungal and nematode biomass, organic substrate C/N ratios too low for measurable increase in net mineralization by the nematodes and small reproduction of the nematodes in the column microcosms were probable contributory factors.  相似文献   
985.
Takatori  Kosuke  Saito  Akemi  Yasueda  Hiroshi  Akiyama  Kazuo 《Mycopathologia》2001,152(1):41-49
The effect of house building design and environment on the fungal movement in the houses of 41 bronchial asthma (BA) patients has been investigated by examining house dust. The presence and composition of fungi were determined and compared in relation to building structure, house age, size of living room, main flooring material, presence of a living-room rug or air purifier, and frequency of vacuum cleaning. Among these elements, fungal CFU apparently varied only between building structure: wooden-board houses had significantly higher numbers of fungi than reinforced concrete houses (p < 0.01), and wooden mortar or iron-framed prefabricated houses had significantly higher numbers of fungi than reinforced concrete houses (p < 0.05). Classification of the types of fungi present in the house dust of BA patients showed that, regardless of the building designs, there were high levels of osmophilic fungi (group A) and fungi that survive at relatively dry conditions (group B), whereas fungi that survive in very wet conditions (group D) were present at low frequency. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
986.
The study of the secondary metabolites of the relict strain Penicillium citrinum VKM FW-800 isolated from ancient Arctic permafrost sediments showed that this fungus produces agroclavine-1 and epoxyagroclavine-1, which are rare ergot alkaloids with the 5R,10S configuration of the tetracyclic ergoline ring system. The production of the alkaloids by the fungus showed a biphasic behavior, being intense in the phase of active growth and slowing down in the adaptive lag phase and in the stationary growth phase. The addition of zinc ions to the incubation medium led to a fivefold increase in the yield of the alkaloids. The alkaloid-producing Penicillium fungi isolated from different regions exhibited the same tendencies of growth and alkaloid production.  相似文献   
987.
988.
989.
990.
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