全文获取类型
收费全文 | 89543篇 |
免费 | 1223篇 |
国内免费 | 1084篇 |
专业分类
安全科学 | 3712篇 |
废物处理 | 3269篇 |
环保管理 | 13761篇 |
综合类 | 21054篇 |
基础理论 | 26177篇 |
环境理论 | 71篇 |
污染及防治 | 14232篇 |
评价与监测 | 5378篇 |
社会与环境 | 3668篇 |
灾害及防治 | 528篇 |
出版年
2022年 | 797篇 |
2021年 | 797篇 |
2020年 | 645篇 |
2019年 | 857篇 |
2018年 | 1119篇 |
2017年 | 1166篇 |
2016年 | 2163篇 |
2015年 | 1828篇 |
2014年 | 2575篇 |
2013年 | 9247篇 |
2012年 | 2159篇 |
2011年 | 2387篇 |
2010年 | 3287篇 |
2009年 | 3372篇 |
2008年 | 1906篇 |
2007年 | 1752篇 |
2006年 | 2176篇 |
2005年 | 2184篇 |
2004年 | 2512篇 |
2003年 | 2336篇 |
2002年 | 1897篇 |
2001年 | 2224篇 |
2000年 | 1972篇 |
1999年 | 1488篇 |
1998年 | 1361篇 |
1997年 | 1351篇 |
1996年 | 1477篇 |
1995年 | 1567篇 |
1994年 | 1473篇 |
1993年 | 1330篇 |
1992年 | 1315篇 |
1991年 | 1289篇 |
1990年 | 1221篇 |
1989年 | 1214篇 |
1988年 | 1042篇 |
1987年 | 980篇 |
1986年 | 985篇 |
1985年 | 1057篇 |
1984年 | 1154篇 |
1983年 | 1164篇 |
1982年 | 1170篇 |
1981年 | 1091篇 |
1980年 | 942篇 |
1979年 | 917篇 |
1978年 | 820篇 |
1977年 | 714篇 |
1976年 | 637篇 |
1975年 | 601篇 |
1973年 | 629篇 |
1972年 | 634篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
31.
Chad L. Hewitt Marnie L. Campbell Ronald E. Thresher Richard B. Martin Sue Boyd Brian F. Cohen David R. Currie Martin F. Gomon Michael J. Keough John A. Lewis Matthew M. Lockett Nicole Mays Matthew A. McArthur Tim D. O'Hara Gary C. B. Poore D. Jeff Ross Melissa J. Storey Jeanette E. Watson Robin S. Wilson 《Marine Biology》2004,144(1):183-202
Port Phillip Bay (PPB) is a large (1,930 km2), temperate embayment in southern Victoria, Australia. Extensive bay-wide surveys of PPB have occurred since 1840. In 1995/1996 the Commonwealth Scientific and Industrial Research Organization (CSIRO) Centre for Research on Introduced Marine Pests (CRIMP) undertook an intensive evaluation of the region with the aims of developing a comprehensive species list of native and introduced biota and contrasting previous bay-wide assessments with a current field survey in order to detect new incursions and discern alterations to native communities. Two methods were used to meet these aims: a re-evaluation of regional museum collections and published research in PPB to identify and determine the timing of introductions; and field surveys for benthic (infauna, epifauna and encrusting) organisms between September 1995 to March 1996. One hundred and sixty introduced (99) and cryptogenic (61) species were identified representing over 13% of the recorded species of PPB. As expected, the majority of these are concentrated around the shipping ports of Geelong and Melbourne. Invasions within PPB appear to be increasing, possibly due to an increase in modern shipping traffic and an increase in aquaculture (historically associated with incidental introductions); however the records of extensive biological surveys suggest that this may, in part, be an artefact of sampling effort. In contrast to Northern Hemisphere studies, PPB (and Southern Hemisphere introductions in general) have significantly different suites of successfully invading taxa. PPB is presented as one of the most invaded marine ecosystems in the Southern Hemisphere.Communicated by M.S. Johnson, Crawley 相似文献
32.
F. Pricope Ştefănescu G. Tiţescu I. Cărăuş D. Ureche 《Environmental Chemistry Letters》2003,1(2):149-151
During the artificial reproduction of salmonides, the fecundity can be increased either by improving the viability of spermatozoa,
or by extending the time period during which a roe micropile remains open, thus allowing its fecundation. Practically, this
can be achieved by the use of some fertilising techniques suitable for fish species. Here, we show that the reproduction of
rainbow trout in a 1:1 solution of deuterium-depleted water and distilled water led to a significant increase in survival
of roes during their embryonic development. Moreover, the addition of glucose and fructose into the deuterium-depleted fertilising
solutions led to a further increase in roe survival during embryonic development. The increase in survival is mainly explained
by an increase in the motility of spermatozoa. 相似文献
33.
Large Estimates of Minimum Viable Population Sizes 总被引:2,自引:0,他引:2
34.
35.
36.
37.
A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage
and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity,
if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning
area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable
because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether
a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length
(31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases
associated with the usual ogive method of estimation.
Received: 27 June 1997 / Accepted: 1 July 1997 相似文献
38.
Jürgen Tomiuk Lutz Bachmann Michael Leipoldt Jörg U. Ganzhorn Reiner Ries Michaela Weis & Volker Loeschcke 《Conservation biology》1997,11(2):491-497
The genetic polymorphism of natural populations of Lepilemur mustelinus ruficaudatus was studied by protein electrophoresis. We sampled blood from 72 individuals from four populations separated by geographic or anthropogenic barriers from southwestern Madagascar. Six out of 22 enzyme loci showed genetic variation with a degree of polymorphism of 0.273. The expected and observed degree of genetic heterozygosity over all loci is similar to that of other primates (He = 0.058, Ho = 0.036). The F-statistics revealed that the four subpopulations were similar with respect to gene structure (FST = 0.065, p = 0.016), but the genotypic structures within subpopulations were inconsistent with random mating. For the total of the four subpopulations the proportion of heterozygous individuals was significantly smaller than expected under random mating (FIS = 0.373, FIT = 0.414, p < 0.01). These results correspond closely to what is expected considering the low migration ability of individuals of L. m ruficaudatus leading to small and rather isolated inbred populations. 相似文献
39.
40.
Pocillopora damicornis (Linnaeus) is a ubiquitous branching coral found throughout the Indo-Pacific region. Like many other species of coral, P. damicornis displays a large range of morphologies. At One Tree Island, it occurs as two distinct morphs that are easily distinguished by the presence or absence of pink pigmentation. The two colour morphs of P. damicornis were found to differ in their distribution and abundance in the One Tree Island Lagoon. The brown morph was more abudant than the pink morph in the shallows (<1 m),whereas the pink morph was more abundant at deeper sites (>3 m). The two morphs also differed physiologically. The brown morph tended to have a greater calcification rate than the pink morph, regardless of environmental conditions. However, the difference in the calcification rate between the two morphs became non-significant under shaded conditions (5% full sunlight), indicating some degree of physiological plasticity of the morphs. The pink colour in P. damicornis was due to a hydrophilic pigment with a major peak absorbance at 560 nm. The expression of pink pigment had both genetic and phenotypic components. The brown morph has a reduced genetic capacity to express the pigment relative to the pink morph. On the other hand, pigment expression could be induced by light in the pink morph. Although genetic differences ultimately determine the differences between the two morphs of P. damicornis, the extent of pigment expression is under some degree of environmental influence. 相似文献