全文获取类型
收费全文 | 28525篇 |
免费 | 261篇 |
国内免费 | 241篇 |
专业分类
安全科学 | 697篇 |
废物处理 | 1134篇 |
环保管理 | 3076篇 |
综合类 | 7608篇 |
基础理论 | 6462篇 |
环境理论 | 9篇 |
污染及防治 | 7005篇 |
评价与监测 | 1614篇 |
社会与环境 | 1301篇 |
灾害及防治 | 121篇 |
出版年
2022年 | 247篇 |
2018年 | 377篇 |
2017年 | 362篇 |
2016年 | 553篇 |
2015年 | 410篇 |
2014年 | 613篇 |
2013年 | 1941篇 |
2012年 | 730篇 |
2011年 | 975篇 |
2010年 | 867篇 |
2009年 | 974篇 |
2008年 | 1069篇 |
2007年 | 1097篇 |
2006年 | 969篇 |
2005年 | 834篇 |
2004年 | 837篇 |
2003年 | 868篇 |
2002年 | 766篇 |
2001年 | 1064篇 |
2000年 | 739篇 |
1999年 | 492篇 |
1998年 | 355篇 |
1997年 | 351篇 |
1996年 | 340篇 |
1995年 | 406篇 |
1994年 | 386篇 |
1993年 | 313篇 |
1992年 | 330篇 |
1991年 | 351篇 |
1990年 | 383篇 |
1989年 | 355篇 |
1988年 | 277篇 |
1987年 | 256篇 |
1986年 | 240篇 |
1985年 | 282篇 |
1984年 | 291篇 |
1983年 | 273篇 |
1982年 | 274篇 |
1981年 | 269篇 |
1980年 | 233篇 |
1979年 | 265篇 |
1978年 | 199篇 |
1977年 | 207篇 |
1974年 | 200篇 |
1973年 | 208篇 |
1968年 | 197篇 |
1967年 | 240篇 |
1966年 | 205篇 |
1964年 | 201篇 |
1963年 | 196篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
S. Savas S. Eraslan S. Kantarci B. Karaman D. Acarsoz T. Tükel O. Cogulu F. Ozkinay S. Basaran K. Aydınlı M. Yuksel-Apak B. Kirdar 《黑龙江环境通报》2002,22(8):703-709
Childhood-onset spinal muscular atrophy (SMA) is one of the most common neurodegenerative genetic disorders. SMN1 is the SMA-determining gene deleted or mutated in the majority of SMA cases. There is no effective cure or treatment for this disease yet. Thus, the availability of prenatal testing is important. Here we report prenatal prediction for 68 fetuses in 63 Turkish SMA families using direct deletion analysis of the SMN1 gene by restriction digestion. The genotype of the index case was known in 40 families (Group A) but unknown in the remaining 23 families (Group B). A total of ten fetuses were predicted to be affected. Eight of these fetuses were derived from Group A and two of these fetuses were from Group B families. Two fetuses from the same family in Group A had the SMNhyb1 gene in addition to homozygous deletion of the NAIP gene. One fetus from Group A was homozygously deleted for only exon 8 of the SMN2 gene, and further analysis showed the presence of both the SMN1 and SMNhyb1 genes but not the SMN2 gene. In addition, one carrier with a homozygous deletion of only exon 8 of the SMN1 gene was detected to have a SMNhyb2 gene, which was also found in the fetus. To our knowledge, these are the first prenatal cases with SMNhyb genes. Follow-up studies demonstrated that the prenatal predictions and the phenotype of the fetuses correlated well in 33 type I pregnancies demonstrating that a careful molecular analysis of the SMN genes is very useful in predicting the phenotype of the fetus in families at risk for SMA. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
13.
T. Stoichev L. Makedonski T. Trifonova M. Stancheva F. Ribarova 《Chemistry and Ecology》2007,23(3):191-200
In spite of a worldwide reduction in the utilization of organochlorine pesticides (OCPs), they are still a problem for the aquatic environment and human health. The Black Sea is still being polluted with persistent chemicals, including OCPs. Aquatic organisms (sprat, scad, bluefish, shad, belted bonito, goby, and black mussel) with different feeding behaviours were sampled on a seasonal basis from the Bulgarian region of the Black Sea, and the concentrations of 13 OCP residues were determined. Although many of the OCPs were not detected in the samples, in all samples 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) was present mainly in the form of its metabolites 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE). Only about 12% of the total DDT was present as the parent compound pp-DDT, which suggests that it was not being used recently in the region. The total DDT concentrations were generally below 150 μg kg-1 fresh weight, but higher levels—up to 354 μg kg-1 fresh weight—were also measured for fish species with a high fat content. Between-species differences were observed, even when the concentrations were presented on a fat-level basis. DDT concentrations did not show any significant changes over the 2-yr sampling period. Fish sampled in the northern areas of the Bulgarian Black Sea coast seemed to contain higher DDT levels than those from the southern areas, suggesting a major (historical) influence of the Danube River. For permanent monitoring purposes, the utility of Black Sea gobies and scad should be considered. 相似文献
14.
15.
16.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily. 相似文献
17.
Global change, i.e. the mega-process radically transforming the relationship between nature and human civilization since
the end of World War II, is investigated from the point of view of systems analysis. It is argued that this unbridled process
should rather be domesticated by planetary control strategies transpiring from a new science called “geocybernetics”. The
formal aspects of geocybernetic theory are sketched and illustrated in a tutorial theatre world reflecting the overall environment
and development problematic. Within this setting a straightforward operationalization of the sweeping “sustainable development”
ideal through a set of concise paradigms can be achieved. Evidence is provided that geocybernetics is actually feasible on
the basis of earth system modelling and fuzzy-control techniques. 相似文献
18.
19.
20.
Abstract: Broadly conceived and considered in its many usages, sustainability has grave defects as a planning goal, particularly when used by conservationists: it confuses means and ends; it is vague about what is being sustained and who or what is doing the sustaining; it is uninspiring; it is little more than Pinchot-era conservation (and thus ignores the many lessons learned since then); it need not be linked to land, to the land's functioning, or to any ecological science; it need not include a moral component; it is consistent with the view of humans as all-powerful manipulators of the planet; and, in general, it is such a malleable term that its popularity provides only a facade of consensus. When sustainability is defined broadly to include the full range of economic and social aspirations, it poses the particular risk that ecological and biodiversity concerns will be cast aside in favor of more pressing human wants. Given these many defects, the conservation movement should discard the term in favor of a more alluring goal, attentive to nature and its ecological functioning. A sound goal would incorporate and distill the considerable ecological and moral wisdom accumulated since Pinchot's day while giving conservationists the rhetorical tools needed to defend the land against competing pressures. In our view, conservation would be well served by an updated variant of "land health," Aldo Leopold's ecologically grounded goal from the 1940s. Land health as an independent understanding should set the essential terms of how we live and enjoy the earth, providing the framework within which we pursue our many social and economic aims. 相似文献