全文获取类型
收费全文 | 4699篇 |
免费 | 32篇 |
国内免费 | 60篇 |
专业分类
安全科学 | 52篇 |
废物处理 | 170篇 |
环保管理 | 163篇 |
综合类 | 2135篇 |
基础理论 | 876篇 |
环境理论 | 5篇 |
污染及防治 | 973篇 |
评价与监测 | 246篇 |
社会与环境 | 156篇 |
灾害及防治 | 15篇 |
出版年
2022年 | 52篇 |
2021年 | 40篇 |
2019年 | 38篇 |
2018年 | 70篇 |
2017年 | 65篇 |
2016年 | 89篇 |
2015年 | 71篇 |
2014年 | 101篇 |
2013年 | 210篇 |
2012年 | 133篇 |
2011年 | 115篇 |
2010年 | 124篇 |
2009年 | 146篇 |
2008年 | 153篇 |
2007年 | 186篇 |
2006年 | 138篇 |
2005年 | 126篇 |
2004年 | 100篇 |
2003年 | 127篇 |
2002年 | 95篇 |
2001年 | 90篇 |
2000年 | 90篇 |
1999年 | 100篇 |
1998年 | 68篇 |
1997年 | 58篇 |
1996年 | 43篇 |
1995年 | 56篇 |
1994年 | 60篇 |
1993年 | 35篇 |
1991年 | 40篇 |
1990年 | 41篇 |
1989年 | 36篇 |
1985年 | 35篇 |
1979年 | 40篇 |
1970年 | 34篇 |
1969年 | 38篇 |
1967年 | 55篇 |
1966年 | 53篇 |
1965年 | 59篇 |
1964年 | 66篇 |
1963年 | 70篇 |
1962年 | 59篇 |
1961年 | 68篇 |
1960年 | 61篇 |
1959年 | 67篇 |
1958年 | 65篇 |
1957年 | 74篇 |
1956年 | 56篇 |
1955年 | 56篇 |
1954年 | 49篇 |
排序方式: 共有4791条查询结果,搜索用时 15 毫秒
101.
J. Caspar Rüegg 《Die Naturwissenschaften》1998,85(12):575-582
2+ concentrations tropomyosin is located at the edge of the thin filament, thereby interfering with the formation of strong
actin-myosin linkages (blocked state). An increase in Ca2+ activity causes an azimuthal shift of tropomyosin around the filament (by about 30°), thereby increasing the probability
of low-force crossbridge interaction, a process which by cooperative effects induces further tropomyosin movement (by an additional
10°) which results in the open state of the filament characterized by forceful crossbridge interaction. (This mechanism may
be analogous to that in ligand-gated ion channels, where ligand binding increases the open probability of the pore.) The extent
of activation then depends on the free Ca2+ concentration and on the calcium sensitivity of the thin filament that may be affected by protein phosphorylation, crossbridge
attachment, the troponin isoform composition of the filament, and novel calcium-sensitizing drugs that act on the contractile
or regulatory proteins and thus increase the force of the heart. 相似文献
102.
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
103.
The effect of a green leaf volatile on host plant finding by larvae of a herbivorous insect 总被引:1,自引:0,他引:1
The role of a general green leaf volatile (glv) in host finding by larvae of the oligophagous chrysomelid Cassida denticollis was investigated using a new bioassay which takes into account the need for neonate larvae of this species to climb fresh
host plants from the ground. A "stem arena" was designed in which plant stems of the host, tansy (Tanacetum vulgare), and stem dummies (tooth picks), both wrapped in perforated filter paper, were offered to neonate larvae. The wrapping allowed
olfactory responses to be tested by preventing access to contact stimuli of stems and dummies. Larvae significantly preferred
to climb the wrapped tansy stems over dummies after a period of 15 min. The test glv, (Z)-3-hexen-1-ol, was not attractive when applied to dummies. However, when the glv was applied to the bottom of the arena,
the ability of larvae to discriminate between host stems and untreated dummies was significantly enhanced. More larvae climbed
wrapped host stems than dummies even within 5 min. While numerous other herbivorous insects are known to be directly attracted
by glv, this study shows that a singly offered glv on its own is unattractive to an herbivore but enhances the herbivore's
ability to differentiate between host and nonhost plants.
Received: 19 October 1999 / Accepted in revised form: 28 February 2000 相似文献
104.
105.
106.
107.
108.
109.
选取嘉兴市秀洲区和海宁市为研究对象,以乡镇区划为研究单元,采用综合源强估算法和GIS软件,对处理设施的氨氮(NH3-N)、总磷(TP)、化学需氧量(COD)排放强度进行定量估算和空间分析.结果表明,秀洲区处理设施的NH3-N和COD排放强度高于海宁市,而TP排放强度与海宁市差不多.秀洲区内,洪合镇各污染物的排放强度均最高;海宁市内,盐官镇NH3-N排放强度最高,许村镇TP和COD排放强度最高.采用因子分析法和加权指数法计算排污权重,再结合生态敏感性评价和环境功能区划,筛选出运维和监管优先控制区.秀洲区内,洪合镇、王江泾镇、油车港镇被划分为优先控制区,该优先控制区内处理设施数量占比27.87%,排污权重占比72.42%,通过重点监管17.66%的设施,可监管秀洲区59.98%的污染物排放.海宁市内,长安镇、许村镇、海洲街道、盐官镇、袁花镇被划分为优先控制区,该优先控制区内设施数量占比69.10%,排污权重占比71.23%,通过重点监管16.85%的设施,可监管海宁市43.54%的污染物排放.研究结果可为提高设施的运维监管效率提供技术支撑. 相似文献
110.