全文获取类型
收费全文 | 21061篇 |
免费 | 253篇 |
国内免费 | 129篇 |
专业分类
安全科学 | 545篇 |
废物处理 | 902篇 |
环保管理 | 2874篇 |
综合类 | 3429篇 |
基础理论 | 5937篇 |
环境理论 | 10篇 |
污染及防治 | 5421篇 |
评价与监测 | 1319篇 |
社会与环境 | 873篇 |
灾害及防治 | 133篇 |
出版年
2021年 | 143篇 |
2019年 | 141篇 |
2018年 | 253篇 |
2017年 | 260篇 |
2016年 | 415篇 |
2015年 | 317篇 |
2014年 | 477篇 |
2013年 | 1656篇 |
2012年 | 597篇 |
2011年 | 833篇 |
2010年 | 681篇 |
2009年 | 675篇 |
2008年 | 849篇 |
2007年 | 884篇 |
2006年 | 796篇 |
2005年 | 677篇 |
2004年 | 660篇 |
2003年 | 653篇 |
2002年 | 622篇 |
2001年 | 776篇 |
2000年 | 580篇 |
1999年 | 331篇 |
1998年 | 265篇 |
1997年 | 282篇 |
1996年 | 287篇 |
1995年 | 337篇 |
1994年 | 308篇 |
1993年 | 291篇 |
1992年 | 285篇 |
1991年 | 284篇 |
1990年 | 299篇 |
1989年 | 279篇 |
1988年 | 252篇 |
1987年 | 247篇 |
1986年 | 225篇 |
1985年 | 203篇 |
1984年 | 262篇 |
1983年 | 212篇 |
1982年 | 274篇 |
1981年 | 220篇 |
1980年 | 187篇 |
1979年 | 206篇 |
1978年 | 186篇 |
1977年 | 155篇 |
1976年 | 138篇 |
1975年 | 146篇 |
1974年 | 159篇 |
1973年 | 164篇 |
1972年 | 149篇 |
1971年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
67.
68.
Guest Editorial
A view from the countryside 相似文献69.
Interactions between the red algaPlocamium hamatum J. Agardh (Rhodophyta) and other benthic organisms including the alcyonacean soft coralSinularia cruciata (Tixier-Durivault) were investigated on an inshore fringing reef environment in whichP. hamatum was the dominant large fleshy alga. Field observations of sessile reef organisms including octocorals and sponges living in close proximity toP. hamatum revealed that varying degrees of tissue necrosis were suffered by the invertebrates when in physical contact with the alga. In order to establish whether the chemical constituents of the alga, especially chloromertensene, played a role in this necrosis, manipulative field experiments were carried out in the Pelorus Channel, Palm Island group (18°34S; 146°29E), North Queensland, Australia, in November and December 1988. The first experiment involved the relocation of healthy plants and soft corals into contact and non-contact situations on a mesh grid. In all cases of contact betweenP. hamatum andS. cruciata, the soft coral suffered tissue necrosis (n=6,p=0.0022). The second experiment had the same design, but involved the use of artificial plants both uncoated and coated with natural levels of chloromertensene, in contact withS. cruciata. In all cases of contact with coated treatments, necrosis was observed inS. cruciata (n=4,p=0.025). In cases where uncoated artificial fronds were placed in contact with soft corals,S. cruciata showed minor abrasion effects, but no appreciable necrosis. Coated treatments were not fouled by epiphytes during the experiment and were not consumed by predators. Uncoated treatments were rapidly reduced in size by predation and any remaining material was biofouled. These experiments thus demonstrated that the deleterious effects observed in soft corals in the field were caused by contact with the algaP. hamatum, that these effects were indeed chemically mediated by chloromertensene, and that physical contact without chemical intervention caused no such deleterious effects. This is the first experimental evidence which conclusively demonstrates allelopathy between an alga and other marine organisms and identifies the compound responsible for the observed allelopathic effects. 相似文献
70.
Sporophytes of the brown algaLaminaria saccharina (L.) Lamour grown at 15°C contained significantly more chlorophylla (chla) than did similar plants grown at 5°C. The increase in chla in 15°C plants was due to increased numbers of photosystem II reaction centes, and possibly to increased photosynthetic unit size, compared with 5°C plants. These changes were associated with increased values (photosynthetic efficiencies) in 15°C-grownL. saccharina relative to 5°C-grown plants. The changes in together with reduced respiration rates allowed 15°C-grownL. saccharina to achieve net photosynthesis and light-saturated photosynthesis at a lower photon fluence rate (PFR) than 5°C plants when both groups were assayed at the same temperature (15°C). The photon fluence rates necessary to reach the compensation point and achieve light-saturated photosynthesis (I
c
andI
k
, respectively) increased with increasing incubation temperature inL. saccharina grown at both 5 and 15°C. However, acclimation responses to growth temperature compensated for the short-term effect of temperature onI
c
andI
k
. Consequently, plants grown at 5 and 15°C were able to achieve similar rates of light-limited photosynthesis, and similarI
c
andI
k
values at their respective growth temperatures. These responses are undoubtedly important for perennial seaweeds such asL. saccharina, which frequently grow in light-limited habitats and experience pronounced seasonal changes in water temperature.Please address all correspondence and requests for reprints to I.R. Davison 相似文献