全文获取类型
收费全文 | 19851篇 |
免费 | 79篇 |
国内免费 | 49篇 |
专业分类
安全科学 | 226篇 |
废物处理 | 1348篇 |
环保管理 | 2024篇 |
综合类 | 2452篇 |
基础理论 | 5387篇 |
环境理论 | 6篇 |
污染及防治 | 4788篇 |
评价与监测 | 1820篇 |
社会与环境 | 1886篇 |
灾害及防治 | 42篇 |
出版年
2023年 | 97篇 |
2022年 | 243篇 |
2021年 | 211篇 |
2020年 | 97篇 |
2019年 | 118篇 |
2018年 | 1610篇 |
2017年 | 1534篇 |
2016年 | 1478篇 |
2015年 | 344篇 |
2014年 | 449篇 |
2013年 | 908篇 |
2012年 | 923篇 |
2011年 | 1843篇 |
2010年 | 1123篇 |
2009年 | 1006篇 |
2008年 | 1371篇 |
2007年 | 1723篇 |
2006年 | 508篇 |
2005年 | 401篇 |
2004年 | 385篇 |
2003年 | 412篇 |
2002年 | 400篇 |
2001年 | 370篇 |
2000年 | 235篇 |
1999年 | 154篇 |
1998年 | 76篇 |
1997年 | 81篇 |
1996年 | 65篇 |
1995年 | 98篇 |
1994年 | 94篇 |
1993年 | 75篇 |
1992年 | 75篇 |
1991年 | 74篇 |
1990年 | 76篇 |
1989年 | 63篇 |
1988年 | 65篇 |
1987年 | 61篇 |
1986年 | 57篇 |
1985年 | 49篇 |
1984年 | 59篇 |
1983年 | 62篇 |
1982年 | 53篇 |
1980年 | 32篇 |
1979年 | 37篇 |
1974年 | 32篇 |
1973年 | 30篇 |
1965年 | 32篇 |
1964年 | 54篇 |
1959年 | 35篇 |
1958年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 327 毫秒
151.
152.
IntroductionBecauseofthelowefficiencyoftheelectrostaticprecipitator (ESP)forcollectingthesubmicronparticles ,theelectricalagglomerationmethodhasledtoanincreasinginterestinreducingtheemissionofthefineparticles .Manyauthorshavestudiedelectricalagglomerati… 相似文献
153.
Iigo Loureiro M. Concepcin Escorial Jos María García-Baudin M. Cristina Chueca 《Agriculture, ecosystems & environment》2007,120(2-4):384-390
Hybridization between Aegilops geniculata, A. biuncialis and bread wheat Triticum aestivum has been evaluated during two seasons under simulated field conditions to estimate the field hybridization rate under Central Spain conditions. The mean frequencies of hybridization between A. biuncialis and A. geniculata with wheat were 0.34% and 0.31%, respectively. Data from 10 hybrid plants for each combination showed that hybrids can be partially fertile by backcrossing with wheat parent, with percent averages of 3.17 grains/spikelets for A. biuncialis × wheat hybrids and 2.87 grains/spikelets for A. geniculata × wheat hybrids. Self-pollination, although at very low rates, was also possible in hybrids. The potential risks associated with natural hybridization in the context of transgenic wheat cultivation are discussed. 相似文献
154.
155.
Jan Gustafsson Göran Annerén Ulla-Britt Ericsson Lars Svanberg Sten A. Ivarsson 《黑龙江环境通报》1995,15(5):451-454
The observation that thyroid disease is frequent in mothers of children with Down syndrome (DS) has suggested that maternal thyroid antibodies could be a factor predisposing to trisomy 21 in their offspring. In this study, the incidences of thyroglobulin (Tg) and thyroid peroxidase (TPO) antibodies were analysed with a sensitive solid-phase immunosorbent radioassay in sera from 29 mothers giving birth to children with trisomy 21 and 87 control mothers. The serum samples were collected at delivery. There was no statistical difference regarding the proportion of thyroid antibodies (against Tg and/or TPO) in the two groups. Thyroid antibodies were detected in 6/29 (20.7 per cent) of the DS mothers and in 23/87 (26.4 per cent) of the control mothers. Among the women with thyroid antibodies, 4/6 (66.7 per cent) of the DS mothers and 12/23 (52 per cent) of the control mothers had antibodies against both Tg and TPO. There was no increase in the relative risk of having a child with DS if the titre of either Tg or TPO antibodies or both were positive, i.e. ≥ 1/5. The results indicate that the presence of thyroid antibodies in the serum of a pregnant woman has no prognostic value for the birth of an infant with DS. 相似文献
156.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
157.
Masera Omar R. Cerón Alma Delia Ordóñez Antonio 《Mitigation and Adaptation Strategies for Global Change》2001,6(3-4):291-312
We examine carbon (C) reference and mitigation scenarios for the Mexicanforest sector between the year 2000 and 2030. Estimates are presentedseparately for the period 2008–2012.Future C emissions and capture are estimated using a simulation modelthat: a) allocates the country land use/land cover classes among differentfuture uses and categories using demand-based scenarios for forestryproducts; b) estimates the total C densities associated to each land usecategory, and c) determines the net carbon implications of the process ofland use/cover change according to the different scenarios.The options analyzed include both afforestation/reforestation, such ascommercial, bionenergy and restoration plantations, and agroforestrysystems, and forest conservation, through the sustainable management ofnative forests and forest protection.The total mitigation potential, estimated as the difference between the totallong-term carbon stock in the reference and the mitigation scenario reaches300 × 106 Mg C in the year 2012 and increases to 1,382 × 106 Mg C in 2030. The average net sequestration in the 30 year period is 46 × 106 Mg C yr-1, or 12.5 × 106 Mg C yr-1 within the period 2008 to 2012. The costs of selected mitigation options range from 0.7–3.5 Mg C-1 to 35 Mg C-1. Some options are cost effective. 相似文献
158.
159.
Bosch J 《Die Naturwissenschaften》2002,89(12):575-578
Female midwife toads (genus Alytes) emit highly variable reciprocal calls of unclear function prior to and during courtship. In some species, female-female competition, expressed as physical fighting, has been reported. Males of Majorcan midwife toads (Alytes muletensis) show phonotactic response to female calls, and females of Iberian midwife toads (Alytes cisternasii) respond differently according to the male call characteristics. In this study, I test the hypothesis of female-female acoustic competition as an additional function of female reciprocal calls. Playback tests indicate that female calls are not clearly involved in female acoustic competition in the Iberian midwife toad, therefore female calls could be directed at males rather than towards competitive females. 相似文献
160.
Circulating placental [human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), decidual (pregnancy protein) 12 (PP12), and fetal alphafetoprotein (AFP)] proteins were measured immediately before and within 1 h in 18 women undergoing diagnostic chorionic villus sampling (CVS) in the first trimester. An elevation of serum AFP levels was consistently seen, while fluctuations in excess of 10 per cent of the pre-CVS levels of SP1 and PP12 were seen in the majority of patients. Fluctuations in hCG and PAPP-A were consistently less than 10 per cent of pre-CVS values. Post-CVS changes in levels were not apparently associated with any feature of the technique, the pregnancy, or its outcome (one missed abortion). As feto-maternal haemorrhage is a common event, anti-D should be offered to rhesus-negative women undergoing CVS. In the prediction of subsequent miscarriage, only hCG and PAPP-A measurements should be considered. 相似文献