全文获取类型
收费全文 | 255275篇 |
免费 | 16178篇 |
国内免费 | 40011篇 |
专业分类
安全科学 | 23846篇 |
废物处理 | 11679篇 |
环保管理 | 29293篇 |
综合类 | 105161篇 |
基础理论 | 47856篇 |
环境理论 | 211篇 |
污染及防治 | 54445篇 |
评价与监测 | 16735篇 |
社会与环境 | 15159篇 |
灾害及防治 | 7079篇 |
出版年
2024年 | 855篇 |
2023年 | 3954篇 |
2022年 | 9445篇 |
2021年 | 9493篇 |
2020年 | 8959篇 |
2019年 | 7162篇 |
2018年 | 8353篇 |
2017年 | 10124篇 |
2016年 | 10309篇 |
2015年 | 9853篇 |
2014年 | 11517篇 |
2013年 | 21148篇 |
2012年 | 16291篇 |
2011年 | 18191篇 |
2010年 | 15912篇 |
2009年 | 15703篇 |
2008年 | 16071篇 |
2007年 | 15782篇 |
2006年 | 14712篇 |
2005年 | 11346篇 |
2004年 | 8832篇 |
2003年 | 7779篇 |
2002年 | 6885篇 |
2001年 | 6248篇 |
2000年 | 5314篇 |
1999年 | 3636篇 |
1998年 | 2423篇 |
1997年 | 2203篇 |
1996年 | 2236篇 |
1995年 | 2312篇 |
1994年 | 2041篇 |
1993年 | 1502篇 |
1992年 | 1508篇 |
1991年 | 1369篇 |
1990年 | 1256篇 |
1989年 | 1149篇 |
1988年 | 1014篇 |
1987年 | 907篇 |
1986年 | 859篇 |
1985年 | 870篇 |
1984年 | 896篇 |
1983年 | 824篇 |
1982年 | 918篇 |
1981年 | 817篇 |
1980年 | 627篇 |
1979年 | 686篇 |
1978年 | 585篇 |
1977年 | 513篇 |
1975年 | 467篇 |
1974年 | 461篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Fragile X syndrome is the most common cause of familial mental retardation. The most common mutation is expansion of a triplet (CGG)n repeat in the 5′ untranslated region of the FMR1 gene on Xq27.3. The expansion is refractory to PCR due to preferential amplification of the smaller allele in heterozygous cells and the high GC content of the repeat and surrounding sequences. Direct detection of the normal parental alleles in preimplantation embryos has been used for preimplantation genetic diagnosis (PGD) of this disorder. However, this approach is only suitable for approximately 63% of couples due to the heterozygosity of the repeat in the normal population. As an alternative we investigated the use of polymorphic markers flanking the mutation to track the normal and premutation carrying maternal chromosomes in preimplantation embryos. Using a panel of 11 polymorphisms, six (CA)n repeats and five single nucleotide polymorphisms, diagnosis was developed for 90% of referred couples. Multiplex amplification of informative markers was tested in 300 single buccal cells from interested couples with efficiency and allele drop out (ADO) rates ranging from 69% to 96% and 6% to 18%, respectively. Use of this approach is accurate and applicable to a larger number of patients at risk of transmitting fragile X to their offspring. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
202.
D Heinevetter H J Lewerenz R Plass R Macholz 《Journal of environmental science and health. Part. B》1985,20(5):539-558
In vitro investigations of the influence of lindane and its metabolites were performed on microsomal and mitochondrial ATPases from liver, kidney and brain of rat and mouse. The microsomal Na+-K+-ATPases in rat liver were inhibited by the tested substances. An increase of activity was observed only with 2.5 X 10(-5) M gamma-HCH. Effects on the microsomal Na+-K+-ATPase from kidney and brain of rat were also indicated. The mitochondrial enzyme in rat liver was stimulated by all the compounds tested at concentrations of 10(-4) M - 10(-2) M. The effects on mitochondrial enzymes from kidney and brain varied in dependence on the tested substances. In the microsomes and mitochondria of mouse an influence on the Na+-K+-ATPases similar to the effects on the preparations from organs of rat was evident. 相似文献
203.
A new, simple method for directly measuring activated sludge density was developed and applied, and the effects of biomass density on activated sludge settling in full-scale systems were evaluated. The driving force of sedimentation is the physical weight of the biological solids, but the role of biomass density in sedimentation has been largely ignored. Biomass density varied amongst treatment systems and this variability was correlated with settleability. Floc densities were approximately normally distributed within individual samples. Nonsoluble phosphorus content was a major contributor to density, and plants with enhanced biological phosphorus removal (EBPR) configurations generally had higher densities and better settleability than non-EBPR plants with similar filament contents. These results suggest that future work may benefit from consideration of density as a factor affecting activated sludge settling. 相似文献
204.
205.
Xiang Laisheng Guo Yajun Li Zhanfang . School of Management Northeastern University Shenyang Liaoning China . Development Research Center of Liaoning People’s Government Shenyang Liaoning China 《中国人口.资源与环境(英文版)》2007,5(2):49-52
In the high technology industry, small and medium sized technology enterprises (SMSTEs) play a pivotal role in advancing the whole industry. To achieve sustainable development, they need to extend their scope of business activities beyond a national view and exploit international market actively to meet international competitions that increase quickly in the form of allocating resources within the scope of the world. However, the SMSTEs are also facing risks associated with themselves during the process of exploiting international market owing to their own restrictions, so what they should do is to consider risk evaluations in exploiting the international market. 相似文献
206.
207.
208.
PAOLO GUIDETTI SIMONETTA FRASCHETTI ANTONIO TERLIZZI FERDINANDO BOERO 《Conservation biology》2004,18(5):1417-1423
Abstract: We surveyed shallow, rocky reefs in southwestern Apulia (Mediterranean Sea) to assess the effects on coastal fish assemblages of the date mussel ( Lithophaga lithophaga ) fishery, an illegal practice that strips the rocky reef bare. We visually sampled fish four times over 15 months at three locations, one affected by date-mussel fishery and two controls. The fish assemblage at the affected location differed significantly from those at the control locations over all sampling times. Herbivorous fishes, sparids, and labrids (genus Symphodus ) contributed most to the differences between the affected location and controls. Lower densities of Symphodus spp. were observed at the affected location, whereas detritivorous fishes were recorded exclusively at control sites. Small serranids and sparids showed temporal trends that differed between the affected location and the control locations. Our results suggest that the date-mussel fishery affects fish assemblages chiefly through reduction of arborescent macroalgae (contributing to habitat complexity and primary production) and emphasize the need for more effective policing against this destructive practice. 相似文献
209.