全文获取类型
收费全文 | 19236篇 |
免费 | 164篇 |
国内免费 | 165篇 |
专业分类
安全科学 | 451篇 |
废物处理 | 831篇 |
环保管理 | 2245篇 |
综合类 | 2971篇 |
基础理论 | 5863篇 |
环境理论 | 5篇 |
污染及防治 | 4656篇 |
评价与监测 | 1286篇 |
社会与环境 | 1160篇 |
灾害及防治 | 97篇 |
出版年
2022年 | 130篇 |
2021年 | 116篇 |
2020年 | 103篇 |
2019年 | 113篇 |
2018年 | 316篇 |
2017年 | 356篇 |
2016年 | 532篇 |
2015年 | 326篇 |
2014年 | 476篇 |
2013年 | 1264篇 |
2012年 | 914篇 |
2011年 | 914篇 |
2010年 | 655篇 |
2009年 | 629篇 |
2008年 | 740篇 |
2007年 | 799篇 |
2006年 | 663篇 |
2005年 | 1058篇 |
2004年 | 1214篇 |
2003年 | 1060篇 |
2002年 | 545篇 |
2001年 | 691篇 |
2000年 | 495篇 |
1999年 | 287篇 |
1998年 | 192篇 |
1997年 | 223篇 |
1996年 | 213篇 |
1995年 | 250篇 |
1994年 | 239篇 |
1993年 | 186篇 |
1992年 | 203篇 |
1991年 | 197篇 |
1990年 | 212篇 |
1989年 | 196篇 |
1988年 | 157篇 |
1987年 | 167篇 |
1986年 | 156篇 |
1985年 | 160篇 |
1984年 | 157篇 |
1983年 | 148篇 |
1982年 | 131篇 |
1981年 | 126篇 |
1980年 | 121篇 |
1979年 | 129篇 |
1978年 | 105篇 |
1977年 | 118篇 |
1975年 | 92篇 |
1974年 | 93篇 |
1973年 | 105篇 |
1972年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
171.
172.
Research in molecular neurobiology has recently entered a new phase of rapid development as a result of the application of the techniques of molecular genetics. This is illustrated by recent work on the electric ray (Torpedo marmorata and T. californica), whose electric organ is a rich source of cholinergic synapses. Other examples from recent literature of the application of the recombinant DNA technique to the mammalian central nervous system are given and possible future developments are discussed. 相似文献
173.
174.
Overestimates of black carbon in soils and sediments 总被引:2,自引:0,他引:2
Several recent reports suggest that black carbon (BC), which broadly encompasses charcoal, soot, and other forms of pyrogenic carbon, may constitute a significant proportion of the refractory carbon in soil and sedimentary organic matter. BC is a sink for biospheric and atmospheric carbon dioxide, and is intimately tied to the biogeochemical cycling of both carbon and oxygen through its role in organic matter cycling. Additionally, BC may represent a large fraction of the missing carbon sink in global carbon accounting. Here, we demonstrate that documented measurements of BC may be the result of methodological artifacts, which inadvertently overestimate the amount of BC. We found that a widely used thermal oxidative method can create a residue that falls under the operational definition of BC in samples that are relatively BC-free. Moreover, during this procedure, labile organic matter constituents are condensed into pyrogenic carbon, implying that the labile components are present in lesser quantities. These methodological deficiencies are promoting overestimates in the amount of refractory carbon in soil and sedimentary organic matter and may endorse inaccuracies in the rates of carbon fluxes, the mean residence times of terrestrial carbon, and organic matter burial rates in oceanic environments. 相似文献
175.
The prenatal diagnosis of The Turner Syndrome is described at a menstrual age of 12 weeks. Detection of cystic hygroma was followed by vaginal chorionic villous sampling (CVS) which revealed a 45,X karyotype. Early documentation of fetal karyotype in the presence of a cystic hygroma is essential for accurate diagnosis and genetic counselling. 相似文献
176.
Plasticity of honeybee castes 总被引:1,自引:0,他引:1
177.
Fibroblasts from a fetus with the prenatal diagnosis of mosaic trisomy 20 were cloned by dilution plating. Adenosine deaminase (ADA), a biochemical marker for chromosome 20, was assayed in trisomic clones and normal clones as control. The cytogenetic diagnosis was substantiated by demonstration of a triplex gene dosage effect for ADA in the trisomic cells. 相似文献
178.
J. H. A. M. Tuerlings MD A. S. P. M. Breed R. Vosters G. J. P. A. Anders 《黑龙江环境通报》1993,13(4):301-306
A 70,XXX, +18 karyotype was found by chorionic villus sampling, while the fetal fibroblast culture of the affected fetus revealed a 47,XX,+ 18 karyotype. From several possible mechanisms, we assume that a second gamete fusion occurred after the first cell division of the zygote. According to this interpretation, the mosaicism arose in very early pregnancy (at the two-cell stage). This discrepancy can therefore be explained by selection pressure, due to the differentiation processes in the embryonic tissues. 相似文献
179.
180.
The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee. 相似文献