全文获取类型
收费全文 | 29331篇 |
免费 | 215篇 |
国内免费 | 221篇 |
专业分类
安全科学 | 644篇 |
废物处理 | 1376篇 |
环保管理 | 3485篇 |
综合类 | 3865篇 |
基础理论 | 7969篇 |
环境理论 | 7篇 |
污染及防治 | 7246篇 |
评价与监测 | 2331篇 |
社会与环境 | 2696篇 |
灾害及防治 | 148篇 |
出版年
2022年 | 254篇 |
2021年 | 269篇 |
2020年 | 168篇 |
2019年 | 216篇 |
2018年 | 831篇 |
2017年 | 808篇 |
2016年 | 982篇 |
2015年 | 482篇 |
2014年 | 720篇 |
2013年 | 2150篇 |
2012年 | 1012篇 |
2011年 | 1673篇 |
2010年 | 1270篇 |
2009年 | 1336篇 |
2008年 | 1618篇 |
2007年 | 1912篇 |
2006年 | 1055篇 |
2005年 | 946篇 |
2004年 | 926篇 |
2003年 | 952篇 |
2002年 | 936篇 |
2001年 | 1100篇 |
2000年 | 773篇 |
1999年 | 461篇 |
1998年 | 348篇 |
1997年 | 304篇 |
1996年 | 339篇 |
1995年 | 332篇 |
1994年 | 299篇 |
1993年 | 278篇 |
1992年 | 284篇 |
1991年 | 254篇 |
1990年 | 263篇 |
1989年 | 263篇 |
1988年 | 227篇 |
1987年 | 190篇 |
1986年 | 168篇 |
1985年 | 177篇 |
1984年 | 219篇 |
1983年 | 184篇 |
1982年 | 228篇 |
1981年 | 169篇 |
1980年 | 159篇 |
1979年 | 189篇 |
1978年 | 141篇 |
1977年 | 133篇 |
1976年 | 120篇 |
1975年 | 111篇 |
1974年 | 114篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Mitigation and adaptation synergy in forest sector 总被引:1,自引:1,他引:1
N. H. Ravindranath 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):843-853
Mitigation and adaptation are the two main strategies to address climate change. Mitigation and adaptation have been considered
separately in the global negotiations as well as literature. There is a realization on the need to explore and promote synergy
between mitigation and adaptation while addressing climate change. In this paper, an attempt is made to explore the synergy
between mitigation and adaptation by considering forest sector, which on the one hand is projected to be adversely impacted
under the projected climate change scenarios and on the other provide opportunities to mitigate climate change. Thus, the
potential and need for incorporating adaptation strategies and practices in mitigation projects is presented with a few examples.
Firstly, there is a need to ensure that mitigation programs or projects do not increase the vulnerability of forest ecosystems
and plantations. Secondly, several adaptation practices could be incorporated into mitigation projects to reduce vulnerability.
Further, many of the mitigation projects indeed reduce vulnerability and promote adaptation, for example; forest and biodiversity
conservation, protected area management and sustainable forestry. Also, many adaptation options such as urban forestry, soil
and water conservation and drought resistant varieties also contribute to mitigation of climate change. Thus, there is need
for research and field demonstration of synergy between mitigation and adaptation, so that the cost of addressing climate
change impacts can be reduced and co-benefits increased. 相似文献
45.
C. A. Dell'Agnola V. Tomaselli E. Teruzzi B. Tadini A. G. Coran Surgeon-in-Chief 《黑龙江环境通报》1993,13(7):629-632
The impact of prenatal sonographic diagnosis of oesophageal and gastrointestinal obstructions has been analysed over a 10-year period. Three groups of patients were evaluated. The first group consisted of 46 newborns with abnormal prenatal sonogratns, 41 of which were confirmed to have intestinal obstruction postnatally. The second group consisted of 17 neonates with normal prenatal sonograms who had intestinal obstruction postnatally. The third group included 56 newborns who did not undergo a prenatal sonogram but who had intestinal obstruction confirmed at surgery. Polyhydramnios without the appearance of a stomach on ultrasound was diagnostic of pure oesophageal atresia. Polyhydramnios with intestinal dilation was diagnostic of intestinal obstruction. Although surgery was performed earlier in the infants diagnosed prenatally with ultrasound, mortality was no less than in the group that did not undergo a prenatal sonogram, probably because of the high incidence of associated anomalies. 相似文献
46.
47.
48.
49.
The influence of source and timing of nitrogen fertilizers on yield and nitrogen use efficiency of four sweet potato cultivars 总被引:2,自引:0,他引:2
R. O. Ankumah V. Khan K. Mwamba K. Kpomblekou-A 《Agriculture, ecosystems & environment》2003,100(2-3):201
Nitrogen (N) availability is a very important determinant of crop yield. It is also one of the most expensive inputs in crop production. Thus, the efficient management of N by farmers with limited resource is a very important part of successful soil and crop management system. A field study was conducted on a Norfolk sandy loam soil at the George Washington Carver Agricultural Experiment Station, Tuskegee, AL, to evaluate the influence of fertilizer source and timing on the yield of four sweet potato [Ipomoea batatas (L.)] cultivars. Two N sources (urea, CO(NH2)2 and ammonium nitrate, NH4NO3), four sweet potato cultivars (‘Georgia Jet’, GA-Jet; ‘TU-82-155’, TU-155; ‘TU-1892’; and ‘Rojo Blanco’, Rojo-Bl) and three times (zero, single, and split applications) were used in a factorial designed experiment. Plants were harvested after 80 and 120 days and total and marketable yields determined. Nitrogen recovery efficiency, yield efficiency and physiological efficiency were also determined. Total and marketable yields of early maturing cultivars were significantly higher than of late maturing cultivars (P<0.05). The single application of N resulted in significantly higher yield in storage roots than split application (P<0.05). Physiological efficiency values were highly correlated with total marketable yields. Recovery rates increased with time. Late maturing cultivars tended to have higher N recovery and physiological efficiency than early maturing cultivars. These results suggest that cultivar maturity group should play an important part in N fertilization recommendations for sweet potato. 相似文献
50.
R.H. Field S. Benke K. Bdonyi R.B. Bradbury 《Agriculture, ecosystems & environment》2007,120(2-4):399-404
Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution. 相似文献