全文获取类型
收费全文 | 3411篇 |
免费 | 266篇 |
国内免费 | 1230篇 |
专业分类
安全科学 | 301篇 |
废物处理 | 192篇 |
环保管理 | 286篇 |
综合类 | 2121篇 |
基础理论 | 523篇 |
环境理论 | 1篇 |
污染及防治 | 958篇 |
评价与监测 | 167篇 |
社会与环境 | 206篇 |
灾害及防治 | 152篇 |
出版年
2024年 | 11篇 |
2023年 | 66篇 |
2022年 | 214篇 |
2021年 | 192篇 |
2020年 | 170篇 |
2019年 | 138篇 |
2018年 | 159篇 |
2017年 | 194篇 |
2016年 | 163篇 |
2015年 | 186篇 |
2014年 | 263篇 |
2013年 | 350篇 |
2012年 | 296篇 |
2011年 | 332篇 |
2010年 | 255篇 |
2009年 | 243篇 |
2008年 | 230篇 |
2007年 | 176篇 |
2006年 | 237篇 |
2005年 | 151篇 |
2004年 | 103篇 |
2003年 | 85篇 |
2002年 | 102篇 |
2001年 | 87篇 |
2000年 | 97篇 |
1999年 | 76篇 |
1998年 | 55篇 |
1997年 | 50篇 |
1996年 | 37篇 |
1995年 | 48篇 |
1994年 | 24篇 |
1993年 | 32篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有4907条查询结果,搜索用时 828 毫秒
141.
142.
143.
土体固结度是真空预压法加固土体效果的一个重要评价指标,地基最大沉降量的计算是确定土体固结度的关键。本文结合工程实例,分析了GM(1,1)灰色模型在真空预压沉降预测中的可行性,根据部分实测数据计算了地基最大沉降量及土体固结度,并与常用的三点法和双曲线法计算结果进行对比,结果表明GM(1,1)灰色模型的预测结果更符合工程实际。该研究对真空预压施工具有一定的指导意义。 相似文献
144.
145.
In this study, landmark-based methods of geometric morphometrics are used for investigating the main aspects of cranial shape transformation in the evolution of the giant panda, Ailuropoda melanoleuca. Specifically, we explore if the highly derived cranial adaptations for bamboo feeding of the living panda were developed early in the panda's lineage. Results obtained show that the overall cranial morphologies of the oldest known panda, the "pygmy" Ailuropoda microta, and the late Pleistocene Ailuropoda baconi are both very similar to that of their closest living relative, A. melanoleuca, which agrees with a previous proposal based on qualitative criteria. However, we also describe several differences between the crania of A. microta, A. baconi, and A. melanoleuca, including the development of the postorbital process, the orientation of the occipital region, and the expansion of the braincase. As a result, the cranial morphology of A. microta shows a less specialized morphology toward a fibrous and durophagous diet compared to the giant panda. These results are confirmed by a comparative analysis of the dimensions of the upper teeth in bears, which has revealed differences in relative tooth size between A. microta and A. melanoleuca, most probably as a result of mosaic evolution. Therefore, we conclude that cranial shape did not remain essentially uniform in the Ailuropoda lineage, as previously thought, but underwent a number of changes during more than 2?Myr. 相似文献
146.
147.
148.
以COD作为主要参照指标,研究了焦化废水在符合GB 13456-92<钢铁工业水污染物排放标准>焦化一级、二级排放标准限值要求时,对蚕豆和大麦幼根生长、根尖细胞遗传毒性的影响.结果表明:在实验周期内,焦化废水对蚕豆幼根根长、根重和有丝分裂指数的影响不大;对大麦幼根根重无明显影响,而对大麦根长和有丝分裂指数有促进作用.焦... 相似文献
149.
150.
Tao Zhang Qiucheng Li Lili Ding Hongqiang Ren Ke Xu Yonggang Wu Dong Sheng 《环境科学学报(英文版)》2011,23(6):881-890
Chemical precipitation to form magnesium ammonium phosphate (MAP) is an effective technology for recovering ammonium
nitrogen (NH4
+-N). In the present research, we investigated the thermodynamic modeling of the PHREEQC program for NH4
+-N
recovery to evaluate the effect of reaction factors on MAP precipitation. The case study of NH4
+-N recovery from coking wastewater
was conducted to provide a comparison. Response surface methodology (RSM) was applied to assist in understanding the relative
significance of reaction factors and the interactive effects of solution conditions. Thermodynamic modeling indicated that the saturation
index (SI) of MAP followed a polynomial function of pH. The SI of MAP increased logarithmically with the Mg2+/NH4
+ molar ratio
(Mg/N) and the initial NH4
+-N concentration (CN), respectively, while it decreased with an increase in Ca2+/NH4
+ and CO3
2??/NH4
+
molar ratios (Ca/N and CO3
2??/N), respectively. The trends for NH4
+-N removal at different pH and Mg/N levels were similar to the
thermodynamic modeling predictions. The RSM analysis indicated that the factors including pH, Mg/N, CN, Ca/N, (Mg/N) (CO3
2??/N),
(pH)2, (Mg/N)2, and (CN)2 were significant. Response surface plots were useful for understanding the interaction effects on NH4
+-N
recovery. 相似文献