全文获取类型
收费全文 | 37638篇 |
免费 | 15524篇 |
国内免费 | 977篇 |
专业分类
安全科学 | 6474篇 |
废物处理 | 801篇 |
环保管理 | 2983篇 |
综合类 | 27364篇 |
基础理论 | 6053篇 |
污染及防治 | 4373篇 |
评价与监测 | 2226篇 |
社会与环境 | 2262篇 |
灾害及防治 | 1603篇 |
出版年
2025年 | 468篇 |
2024年 | 1264篇 |
2023年 | 1720篇 |
2022年 | 2712篇 |
2021年 | 2725篇 |
2020年 | 2916篇 |
2019年 | 2254篇 |
2018年 | 2203篇 |
2017年 | 2568篇 |
2016年 | 2117篇 |
2015年 | 2205篇 |
2014年 | 2092篇 |
2013年 | 2625篇 |
2012年 | 3030篇 |
2011年 | 2923篇 |
2010年 | 2750篇 |
2009年 | 2748篇 |
2008年 | 2530篇 |
2007年 | 2494篇 |
2006年 | 2410篇 |
2005年 | 1801篇 |
2004年 | 1287篇 |
2003年 | 896篇 |
2002年 | 814篇 |
2001年 | 699篇 |
2000年 | 622篇 |
1999年 | 351篇 |
1998年 | 187篇 |
1997年 | 122篇 |
1996年 | 130篇 |
1995年 | 107篇 |
1994年 | 78篇 |
1993年 | 59篇 |
1992年 | 87篇 |
1991年 | 30篇 |
1990年 | 29篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 4篇 |
1972年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Adam Felton Ross A. Alford Annika M. Felton Lin Schwarzkopf 《Behavioral ecology and sociobiology》2006,59(6):786-795
We examined multiple mate choice criteria in Cophixalus ornatus, a terrestrial breeding, microhylid frog. Mate choice consisted of three stages: mate attraction (male calling), courtship
(male behavior between the call site and the nest), and nest site selection by the female. For male C. ornatus, the possession of a call with low dominant frequency relative to calling neighbors increased the probability that they would
attract females. Dominant frequency was negatively correlated with age independent of male mass and snout vent length. When
escorting the female from the call site to their nest, males traveled along more convoluted paths than when returning to the
nest alone. The convolution of the path was, therefore, considered an aspect of courtship. Females released eggs into nests
with structural characteristics typical of nests constructed by older males. Thus, females increased their chances of locating
an acceptable nest by preferentially approaching males with lower dominant frequencies. This study is the first to demonstrate
that age, independent of mass or snout-vent length, can influence call characteristics in anurans, and it is also the first
to demonstrate the importance of male age to female mate choice in an amphibian. 相似文献
3.
4.
对碱激胶凝材料(碱-偏高岭土、碱-矿渣和碱-粉煤灰)与水-水泥体系固化Ph^2+进行了试验研究,其中水-水泥体系为对比样。结果表明:对于相同稠度的碱激发胶凝材料,即使Pb^2+含量达到2.4%,除了碱-粉煤灰的抗压强度略低外,其他都达到30MPa以上,满足填埋或做建筑基材的使用要求;与水泥相比,碱激发胶凝材料能显著降低重金属离子(Ph^2+)浸出浓度,其规律性与其NH4交换容量大小的规律性一致,与其固化体的抗压强度的大小没有相关性。 相似文献
5.
制备以β-环糊精(β- CD)为主体,2,2′,5,5′-四氯联苯胺(TCB)为客体的固态包合物,通过核磁共振氢谱(1H NMR)和红外光谱( FT -IR)分析了包合物的形成.利用紫外吸收光谱研究了β- CD及其衍生物羧甲基-β-环糊精(CMBCD)对TCB的包合行为,并用Job法和Benesi- Hildebrand双倒数法分别获得β- CD及CMBCD与TCB之间的包合比和包合常数.结果表明,β-CD和CMBCD均可与TCB形成包合比为1∶1的包合物,包合常数分别为727.9 L·mol -1和1 647L·mol -1,且经羧甲基修饰之后的β-环糊精对TCB的包合能力明显优于β-环糊精. 相似文献
6.
为了探究采动条件下采场上覆岩层的变形-开裂-运动过程,利用自主开发的适于准静力计算的拉格朗日元与离散元耦合的连续-非连续方法,针对常村煤矿S6-7工作面开展研究.结果表明,1)随工作面推进距离增加,首先,直接顶出现裂缝;然后,采场上覆岩层发生一定程度的弯曲变形、下沉和离层;之后,直接顶垮落,其上岩层破断,并发生明显的弯曲变形、下沉和离层,采空区局部闭合.此后,上述过程循环往复.2)将工作面煤壁前方和开切眼后方上覆岩层最大主应力大于0的最大范围定义为采动影响范围,通过分析悬露岩层长度和弯矩的变化解释了上述两部分采动影响范围的演化规律.3)通过分析工作面煤壁前方煤层支承压力峰值的变化解释了该部分煤层破碎区尺寸的演化规律. 相似文献
7.
Chih-Cheng Lin;Hsiao-Chien Lee;Tai-Wen Hsu;Wen-Hong Liu; 《Sustainable Development》2024,32(5):5224-5239
This study comprises two essential components: a scoping review and interviews with fishermen, both aimed at understanding the Sustainable Development Goals (SDGs) and their relevance to Offshore Wind Energy (OWE) enterprises, particularly in mitigating impacts on local fisheries. Key findings from the scoping review indicate a scarcity of research explicitly dedicated to OWE enterprises' practices concerning. The review's findings emphasize the need for further research to understand the rationale behind these decisions and to explore how OWE enterprises can optimize their practices to address SDG 2. The second part of the study involves interviews with fishermen near proposed offshore wind farm sites in Taiwan. These interviews revealed that fishermen's primary concerns revolve around SDGs 2, 8, 14, and 17. However, OWE enterprises do not prioritize SDG 2, even though fishermen express concerns related to food security, proposing the adoption of marine ranching to enhance seafood supply. Moreover, SDG 17 stands out as a priority for fishermen, while OWE enterprises overlook connections with fisheries associations and fishermen. In conclusion, this study highlights the complexity of the SDG-related issues surrounding OWE enterprises and their impact on local fisheries. 相似文献
8.
In order to clarify the historic academic problem of whether or not livestock poisoning in ancient Suzhou of Northwest China, recorded by Marco Polo in 1295, was selenosis, this study deals with the biogeochemistry of selenium in Sunan County in the Hexi Corridor, which is part of ancient Suzhou in China. It was found that quite a number of farm animals had suffered from intoxication and died as a result of grazing poisonous grasses, mostly Oxytropis DC, Stellera chamaejasme, and Achnatheru inebrians. Toxic symptoms of livestock grazing on Oxytropis DC are similar to those of selenium toxicity, for instance, hair loss and hoof lesions as described by Marco Polo. Therefore, we thought that toxic grass, probably Oxytropis DC, led to the intoxication of livestock recorded by Marco Polo. Average Se concentrations in two members of this species were 0.112 +/- 0.038 mg/kg for the root of Oxytropis glabra, 0.102 +/- 0.027 mg/kg for the stem and leaf of Oxytropis glabra, and 0.066 +/- 0.009 mg/kg for Oxytropis ochrocephala. The average soil selenium concentration was 0.205 +/- 0.127 mg/kg on grassland producing Oxytropis glabra and 0.152 +/- 0.024 mg/kg on grassland producing Oxytropis ochrocephala. The average Se concentration in other plants was 0.076 mg/kg in the root of Ephedra monosperma Mey, 0.029 mg/kg in the root of Rheum palmatum, 0.031 mg/kg in the root of Stellera chamaejasme, 0.037 mg/kg in Achnatherum inebrians, and 0.067 mg/kg in forage grass (Achnatherum splendens ohwi). Selenium concentrations in soils and plants in Sunan County are far less than the thresholds causing selenium toxicity in livestock. As a result, this study concludes that the livestock poisoning recorded by Marco Polo in 1295 might not have been selenosis. 相似文献
9.
王保士 《再生资源与循环经济》2010,3(6):43-44
##正##(接上期)4.5签定销售合同售方和购方之间应签定标的为制备批次电子废件的标准合同。合同中应指明双方义务,含贵金属废件与废料的准备与发货方法,验收、取样分析方法,结算方法和双方责任。4.6运输批次电子废件的运输必须遵守以下条件。4.6.1含金及铂族金属大于5%的废件与废料,其运输应按照俄罗斯联邦通信部关于贵重品运输的细则并经专用通道实施。 相似文献
10.