全文获取类型
收费全文 | 21587篇 |
免费 | 364篇 |
国内免费 | 390篇 |
专业分类
安全科学 | 803篇 |
废物处理 | 952篇 |
环保管理 | 3715篇 |
综合类 | 3315篇 |
基础理论 | 5412篇 |
环境理论 | 11篇 |
污染及防治 | 5519篇 |
评价与监测 | 1276篇 |
社会与环境 | 1166篇 |
灾害及防治 | 172篇 |
出版年
2023年 | 105篇 |
2022年 | 178篇 |
2021年 | 209篇 |
2020年 | 205篇 |
2019年 | 194篇 |
2018年 | 344篇 |
2017年 | 336篇 |
2016年 | 503篇 |
2015年 | 414篇 |
2014年 | 538篇 |
2013年 | 1883篇 |
2012年 | 751篇 |
2011年 | 1091篇 |
2010年 | 830篇 |
2009年 | 932篇 |
2008年 | 1037篇 |
2007年 | 1094篇 |
2006年 | 915篇 |
2005年 | 742篇 |
2004年 | 781篇 |
2003年 | 726篇 |
2002年 | 680篇 |
2001年 | 714篇 |
2000年 | 604篇 |
1999年 | 401篇 |
1998年 | 276篇 |
1997年 | 288篇 |
1996年 | 281篇 |
1995年 | 333篇 |
1994年 | 263篇 |
1993年 | 268篇 |
1992年 | 244篇 |
1991年 | 225篇 |
1990年 | 225篇 |
1989年 | 219篇 |
1988年 | 180篇 |
1987年 | 168篇 |
1986年 | 193篇 |
1985年 | 183篇 |
1984年 | 229篇 |
1983年 | 193篇 |
1982年 | 206篇 |
1981年 | 203篇 |
1980年 | 166篇 |
1979年 | 166篇 |
1978年 | 116篇 |
1977年 | 108篇 |
1975年 | 102篇 |
1974年 | 97篇 |
1972年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 81 毫秒
551.
Christine Susan Fagnant Alexandra Lynn Kossik Nicolette Angela Zhou Liliana Sánchez-Gonzalez Jill Christin Falman Erika Karen Keim Yarrow Linden Alana Scheibe Kilala Sayisha Barnes Nicola Koren Beck David S. Boyle John Scott Meschke 《Food and environmental virology》2017,9(4):383-394
Environmental surveillance of poliovirus (PV) and other non-enveloped viruses can help identify silent circulation and is necessary to certify eradication. The bag-mediated filtration system is an efficient method to filter large volumes of environmental waters at field sites for monitoring the presence of viruses. As filters may require long transit times to off-site laboratories for processing, viral inactivation or overgrowth of bacteria and fungi can interfere with virus detection and quantification (Miki and Jacquet in Aquatic Microb Ecol 51(2):195–208, 2008). To evaluate virus survival over time on ViroCap? filters, the filters were seeded with PV type 1 (PV1) and/or MS2 and then dosed with preservatives or antibiotics prior to storage and elution. These filters were stored at various temperatures and time periods, and then eluted for PV1 and MS2 recovery quantification. Filters dosed with the preservative combination of 2% sodium benzoate and 0.2% calcium propionate had increased virus survival over time when stored at 25 °C, compared to samples stored at 25 °C with no preservatives. While elution within 24 h of filtration is recommended, if storage or shipping is required then this preservative mixture can help preserve sample integrity. Addition of an antibiotic cocktail containing cephapirin, gentamicin, and Proclin? 300 increased recovery after storage at 4 and 25 °C, when compared to storage with no antibiotics. The antibiotic cocktail can aid sample preservation if access to appropriate antibiotics storage is available and sample cold chain is unreliable. This study demonstrated that the use of preservatives or antibiotics is a simple, cost-effective method to improve virus detection from ViroCap cartridge filters over time. 相似文献
552.
553.
How do distinct visual stimuli help bumblebees discover flowers before they have experienced any reward outside of their nest? Two visual floral properties, type of a pattern (concentric vs radial) and its position on unrewarding artificial flowers (central vs peripheral on corolla), were manipulated in two experiments. Both visual properties showed significant effects on floral choice. When pitted against each other, pattern was more important than position. Experiment 1 shows a significant effect of concentric pattern position, and experiment 2 shows a significant preference towards radial patterns regardless of their position. These results show that the presence of markings at the center of a flower are not so important as the presence of markings that will direct bees there. 相似文献
554.
Jennifer L. Kelley Samuel C. Phillips Jonathan P. Evans 《Die Naturwissenschaften》2013,100(10):965-974
While behavioural plasticity is considered an adaptation to fluctuating social and environmental conditions, many animals also display a high level of individual consistency in their behaviour over time or across contexts (generally termed ‘personality’). However, studies of animal personalities that include sexual behaviour, or functionally distinct but correlated traits, are relatively scarce. In this study, we tested for individual behavioural consistency in courtship and exploratory behaviour in male guppies (Poecilia reticulata) in two light environments (high vs. low light intensity). Based on previous work on guppies, we predicted that males would modify their behaviour from sneak mating tactics to courtship displays under low light conditions, but also that the rank orders of courtship effort would remain unchanged (i.e. highly sexually active individuals would display relatively high levels of courtship under both light regimes). We also tested for correlations between courtship and exploratory behaviour, predicting that males that had high display rates would also be more likely to approach a novel object. Although males showed significant consistency in their exploratory and mating behaviour over time (1 week), we found no evidence that these traits constituted a behavioural syndrome. Furthermore, in contrast to previous work, we found no overall effect of the light environment on any of the behaviours measured, although males responded to the treatment on an individual-level basis, as reflected by a significant individual-by-environment interaction. The future challenge is to investigate how individual consistency across different environmental contexts relates to male reproductive success. 相似文献
555.
The automotive industry is developing designs and manufacturing processes for a new generation of electric motors intended for use in hybrid and electric vehicles. This paper is focused on using solid-state welding to join rectangular wires in the fabrication of motor stators. Resistance welding has not typically been applied to copper due to its very high electrical conductivity; however through optimization of the current and pressure profiles, excellent quality copper-to-copper joints have been demonstrated with a technique known as resistance mash welding. A better understanding of resistance mash welding characteristics will help advancements in its application for stators. The limitations of this application will be discussed. 相似文献
556.
Joseph F. Wilson Brad L. Kinsey Yannis P. Korkolis 《Journal of Manufacturing Processes》2013,15(4):580-585
Characterization of the evolving yield loci and forming limit diagrams for sheet materials under biaxial loading is necessary for the development of accurate sheet metal forming process simulations. Biaxial tension testing has been shown to have significant advantages over the current computational and experimental methods for such material characterization; however, the few commercially available loading frames are far too large and expensive to be practical for most metal forming research laboratories. In this paper, the design of a practical servohydraulic biaxial loading frame is presented. The design, control, and operation of the loading frame are discussed in detail, and experimental data is provided to validate the effectiveness of the control system with respect to specimen center shifting. 相似文献
557.
558.
J. S. Rice R. H. Moss P. J. Runci K. L. Anderson E. L. Malone 《Mitigation and Adaptation Strategies for Global Change》2012,17(7):805-819
A new modeling effort exploring the opportunities, constraints, and interactions between mitigation and adaptation at regional scale is utilizing stakeholder engagement in an innovative approach to guide model development and demonstration, including uncertainty characterization, to effectively inform regional decision making. This project, the integrated Regional Earth System Model (iRESM), employs structured stakeholder interactions and literature reviews to identify the most relevant adaptation and mitigation alternatives and decision criteria for each regional application of the framework. The information is used to identify important model capabilities and to provide a focus for numerical experiments. This paper presents the stakeholder research results from the first iRESM pilot region. The pilot region includes the Great Lakes Basin in the Midwest portion of the United States as well as other contiguous states. This geographic area (14 states in total) permits cohesive modeling of hydrologic systems while also providing strong gradients in climate, demography, land cover/land use, and energy supply and demand. The results from the stakeholder research indicate that, for this region, iRESM should prioritize addressing adaptation alternatives in the water resources, urban infrastructure, and agriculture sectors, including water conservation, expanded water quality monitoring, altered reservoir releases, lowered water intakes, urban infrastructure upgrades, increased electric power reserves in urban areas, and land use management/crop selection changes. For mitigation in this region, the stakeholder research implies that iRESM should focus on policies affecting the penetration of renewable energy technologies, and the costs and effectiveness of energy efficiency, bioenergy production, wind energy, and carbon capture and sequestration. 相似文献
559.
Numair Ahmed Andrew Carlson John A. Rogers Placid M. Ferreira 《Journal of Manufacturing Processes》2012,14(2):90-97
This paper demonstrates the use of a flexible instrumented stamp to enable automated micro transfer printing as a route to large-area, deterministic assembly of microstructured device components or ‘inks’. The ability to instrument the stamp, a critical component for retrieval and placement of a micro device, to detect contact and monitor localized forces during critical events in the printing process not only allows for the development of a robust manufacturing process, but also for a unique vantage point from which to study fundamental issues and phenomena associated with adhesion and delamination of thin films from a variety of substrate materials. This paper presents basic design analysis on the requirements of the cantilevers for compatibility with a typical transfer printing environment. Off-the-shelf thin film strain gages are integrated with a thin elastomeric post as a preliminary prototype and the feasibility of transfer printing with it is demonstrated. Further, the set-up is calibrated to produce force signals for event detection and in situ diagnosis of the process. 相似文献
560.