全文获取类型
收费全文 | 10066篇 |
免费 | 2篇 |
国内免费 | 18篇 |
专业分类
安全科学 | 8篇 |
废物处理 | 770篇 |
环保管理 | 1235篇 |
综合类 | 1089篇 |
基础理论 | 3236篇 |
污染及防治 | 1827篇 |
评价与监测 | 1015篇 |
社会与环境 | 906篇 |
出版年
2019年 | 3篇 |
2018年 | 1474篇 |
2017年 | 1373篇 |
2016年 | 1201篇 |
2015年 | 132篇 |
2014年 | 18篇 |
2013年 | 28篇 |
2012年 | 470篇 |
2011年 | 1356篇 |
2010年 | 700篇 |
2009年 | 611篇 |
2008年 | 891篇 |
2007年 | 1243篇 |
2006年 | 33篇 |
2005年 | 39篇 |
2004年 | 40篇 |
2003年 | 77篇 |
2002年 | 110篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1969年 | 3篇 |
1966年 | 7篇 |
1965年 | 4篇 |
1964年 | 8篇 |
1963年 | 7篇 |
1961年 | 5篇 |
1960年 | 6篇 |
1959年 | 3篇 |
1958年 | 3篇 |
1957年 | 6篇 |
1956年 | 3篇 |
1955年 | 5篇 |
1954年 | 4篇 |
1953年 | 7篇 |
1938年 | 2篇 |
1935年 | 3篇 |
1934年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
Klaus Urich 《Die Naturwissenschaften》1954,41(19):457-457
44.
45.
Andreas Züttel 《Mitigation and Adaptation Strategies for Global Change》2007,12(3):343-365
Hydrogen storage and transportation or distribution is closely linked together. Hydrogen can be distributed continuously in
pipelines or batch wise by ships, trucks, railway or airplanes. All batch transportation requires a storage system but also
pipelines can be used as pressure storage system. Hydrogen exhibits the highest heating value per weight of all chemical fuels.
Furthermore, hydrogen is regenerative and environment friendly. There are two reasons why hydrogen is not the major fuel of
toady’s energy consumption: First of all, hydrogen is just an energy carrier. And, although it is the most abundant element
in the universe, it has to be produced, since on earth it only occurs in the form of water. This implies that we have to pay
for this energy, which results in a difficult economic task, because since the industrialization we are used to consuming
energy for free. The second difficulty with hydrogen as an energy carrier is the low critical temperature of 33 K, i.e. hydrogen
is a gas at room temperature. For mobile and in many cases also for stationary applications the volumetric and gravimetric
density of hydrogen in a storage system is crucial. Hydrogen can be stored by six different methods and phenomena: high pressure
gas cylinders (up to 800 bar), liquid hydrogen in cryogenic tanks (at 21 K), adsorbed hydrogen on materials with a large specific
surface area (at T < 100 K), absorbed on interstitial sites in a host metal (at ambient pressure and temperature), chemically bond in covalent
and ionic compounds (at ambient pressure), oxidation of reactive metals e.g. Li, Na, Mg, Al, Zn with water. These metals easily
react with water to the corresponding hydroxide and liberate the hydrogen from the water. Finally, the metal hydroxides can
be thermally reduced to the metals in a solar furnace. 相似文献
46.
Klaus Peter Sauer Thomas Lubjuhn Jörn Sindern Harald Kullmann Joachim Kurtz Conny Epplen Jörg Thomas Epplen 《Die Naturwissenschaften》1998,85(5):219-228
Panorpa vulgaris has become a model insect for testing theories of sexual selection. This contribution summarizes that which has been learned
in recent years and presents new data that clearly show that the mating system of P. vulgaris is not simply a resource-defense polygyny, as has previously been thought. In P. vulgaris neither the pattern in food exploitation nor the ratio of variance in the lifetime reproductive success of the two sexes
is in accordance with that expected in resource defense polygynous mating systems. Lifetime mating duration is the most important
proximate determinant of male fitness. Males employing alternative mating tactics obtain copulations of varying duration in
relation to the following sequence: saliva secretion 1 food offering 1 no gift. The number of salivary masses which males
provide to females during their lifetime is significantly correlated with the lifetime condition index. The condition index
depends on the fighting prowess of males and their ability to find food items. Thus saliva secretion of Panorpa is considered a Zahavian handicap, which can serve as an honest quality indicator used by mating females. Our results confirm
four main predictions of the indicator model of the theory of sexual selection: (a) the indicator signals high ecological
quality of its bearer, (b) the indicator value increases with phenotypic quality, (c) the indicator value is positively correlated
with the genetic quality affecting offspring fitness in a natural selection context, and (d) the quality indicator is more
costly for low- than for high-quality individuals. The evolutionary consequences of the mating pattern and the sperm competition
mechanism in P. vulgaris are discussed in the context the way in which sexual selection creates and maintains sperm mixing and the evolution of a
promiscuous mating system. 相似文献
47.
FUENSANTA CARAVACA DINO FIGUEROA ANTONIO ROLDÁn CONCEPCIÓN AZCÓN-AGUILAR 《Environmental management》2003,31(3):0412-0420
The reestablisment of autochthonous plant species is an essential strategy for recovering degraded areas under semiarid conditions.
A field experiment was carried out to assess the short-term effect of two reafforestation methods involving mycorrhizal inoculation
and compost addition on soil quality parameters and Rhamnus lycioides seedling growth. The nutrient content (NPK) and enzymatic activities (dehydrogenase, urease, protease-BAA, acid phosphatase
and β-glucosidase) increased and bulk density decreased in the rhizosphere soil with the organic amendment. Biomass C of rhizosphere
soil increased by at least 240% with respect to the control soil after mycorrhizal inoculation and the combination of compost
addition + mycorrhizal inoculation. Both mycorrhizal inoculation and composted organic residue addition increased R. lycioides seedling growth in the same proportion. In the short term, we conclude that the application of both reafforestation methods
not only enhances the establishment of R. lycioides seedlings, but also improves soil quality. 相似文献
48.
The concept of substituting bio‐diesel produced from plantations on eroded soils for conventional diesel fuel has gained wide‐spread attention in India. In recent months, the Indian central Government as well as some state governments have expressed their support for bringing marginal lands, which cannot be used for food production, under cultivation for this purpose. Jatropha curcas is a well established plant in India. It produces oil‐rich seeds, is known to thrive on eroded lands, and to require only limited amounts of water, nutrients and capital inputs. This plant offers the option both to cultivate wastelands and to produce vegetable oil suitable for conversion to bio‐diesel. More versatile than hydrogen and new propulsion systems such as fuel cell technology, bio‐diesel can be used in today's vehicle fleets worldwide and may also offer a viable path to sustainable transportation, i.e., lower greenhouse gas emissions and enhanced mobility, even in remote areas. Mitigation of global warming and the creation of new regional employment opportunities can be important cornerstones of any forward looking transportation system for emerging economies. 相似文献
49.
50.
Biochar physicochemical parameters as a result of feedstock material and pyrolysis temperature: predictable for the fate of biochar in soil? 总被引:1,自引:0,他引:1