全文获取类型
收费全文 | 40916篇 |
免费 | 418篇 |
国内免费 | 539篇 |
专业分类
安全科学 | 1203篇 |
废物处理 | 1876篇 |
环保管理 | 4875篇 |
综合类 | 8098篇 |
基础理论 | 10192篇 |
环境理论 | 27篇 |
污染及防治 | 10503篇 |
评价与监测 | 2639篇 |
社会与环境 | 2223篇 |
灾害及防治 | 237篇 |
出版年
2022年 | 426篇 |
2021年 | 401篇 |
2020年 | 293篇 |
2019年 | 351篇 |
2018年 | 627篇 |
2017年 | 607篇 |
2016年 | 924篇 |
2015年 | 715篇 |
2014年 | 1093篇 |
2013年 | 3107篇 |
2012年 | 1345篇 |
2011年 | 1777篇 |
2010年 | 1455篇 |
2009年 | 1514篇 |
2008年 | 1781篇 |
2007年 | 1886篇 |
2006年 | 1611篇 |
2005年 | 1385篇 |
2004年 | 1296篇 |
2003年 | 1392篇 |
2002年 | 1232篇 |
2001年 | 1572篇 |
2000年 | 1115篇 |
1999年 | 714篇 |
1998年 | 461篇 |
1997年 | 489篇 |
1996年 | 454篇 |
1995年 | 568篇 |
1994年 | 573篇 |
1993年 | 459篇 |
1992年 | 469篇 |
1991年 | 472篇 |
1990年 | 488篇 |
1989年 | 448篇 |
1988年 | 410篇 |
1987年 | 368篇 |
1986年 | 290篇 |
1985年 | 344篇 |
1984年 | 376篇 |
1983年 | 354篇 |
1982年 | 354篇 |
1981年 | 304篇 |
1980年 | 267篇 |
1979年 | 282篇 |
1978年 | 266篇 |
1977年 | 202篇 |
1975年 | 218篇 |
1974年 | 207篇 |
1972年 | 194篇 |
1971年 | 188篇 |
排序方式: 共有10000条查询结果,搜索用时 930 毫秒
721.
Although amphibians are highly vocal, they generally emit only a limited number of acoustic communication signals. We report here the extraordinarily rich vocal repertoire of Amolops tormotus, a ranid species in China. These frogs produce countless vocalizations, some of which share features of birdsong or primate calls, e.g., ultrasonic frequency components, multiple upward and downward FM sweeps, and sudden onset and offset of selective harmonic components within a call note. Frame-by-frame video analysis of the frog's calling behavior suggests the presence of two pairs of vocal sacs that may contribute to the remarkable call-note complexity in this species. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-002-0335-x. 相似文献
722.
Cooperative prey retrieval in the monomorphic ant Formica schaufussi is carried out by workers that perform functionally distinct roles which persist only for the duration of a single retrieval event. A forager (scout) that locates prey too large to retrieve individually organizes cooperative prey transport by recruiting nestmates (recruits) to assist in retrieval. The scout and recruit roles appear to be determined by whether a worker activates recruitment or is recruited from the nest. Scouts organize recruitment and play a key role in maintaining the cohesion of the retrieval group. If a scout that has initiated group transport is experimentally removed, the recruited workers composing the retrieval group typically abandon the prey and cooperative foraging is terminated. In this context, recruits are unable to function as scouts and reorganize group transport. Individuals marked as recruits in one prey retrieval, however, can switch and act as scouts in subsequent retrievals. Because the roles of individuals persist within but not between retrieval events, the specialization involved in cooperative prey retrieval cannot easily be explained as a response associated with age-related or genetic predispositions. This transient division-of-labor, in which individual roles may persist only for the duration of a single group action, represents a novel type of short-term individual specialization. 相似文献
723.
Microorganisms are able to synthesize three different polyamides by enzymatic processes independently from ribosomal protein biosynthesis: poly(gamma-D-glutamic acid), poly(epsilon-L-lysine) and multi-L-arginyl-poly(L-aspartic acid) which is also referred to as cyanophycin. These polyamides, which occur mainly in Bacillus spp. (and only a few other eubacteria and the nematocysts of Cnidaria, in Streptomyces albulus or in cyanobacteria, respectively), have recently attracted considerable interest of the chemical industry and may be suitable for various applications. This review summarizes our current knowledge on the occurrence, biosynthesis, physiological functions, and biodegradation as well as on the properties and putative applications of these polyamides. Emphasis is placed on the enzymology of the polymerization and on the genes encoding the polymerizing enzymes, which have only recently become available for cyanophycin synthetases. Prospects for novel production processes. in particular for cyanophycin, are also presented. 相似文献
724.
Aysen Müezzinoğlu Tolga Elbir Abdurrahman Bayram 《Environmental Engineering and Policy》1998,1(2):109-116
In this study, an inventory of air pollutant emission estimates from major air polluting sources in Turkey for period between 1985 and 2005 with 5-year intervals were estimated. Inventory covers anthropogenic sources of five major air pollutants of particulate matter, sulfur dioxide, carbon monoxide, nitrogen oxides and non-methane volatile organic compounds. Their break-down with respect to main activity sectors were shown and their distribution by the largest industrial source categories were worked out as annual estimates. This inventory and its analysis point to serious environmental implications of air pollutants and a need to develop a policy plan for reducing these emissions. 相似文献
725.
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
726.
727.
728.
Robert M. Wolcott Marco Antonio González 《Mitigation and Adaptation Strategies for Global Change》1997,2(2-3):vii-viii
Mitigation and Adaptation Strategies for Global Change - 相似文献
729.
730.