全文获取类型
收费全文 | 14315篇 |
免费 | 99篇 |
国内免费 | 156篇 |
专业分类
安全科学 | 346篇 |
废物处理 | 591篇 |
环保管理 | 1556篇 |
综合类 | 3240篇 |
基础理论 | 3336篇 |
环境理论 | 6篇 |
污染及防治 | 3567篇 |
评价与监测 | 1100篇 |
社会与环境 | 758篇 |
灾害及防治 | 70篇 |
出版年
2022年 | 127篇 |
2021年 | 106篇 |
2019年 | 100篇 |
2018年 | 193篇 |
2017年 | 203篇 |
2016年 | 299篇 |
2015年 | 226篇 |
2014年 | 399篇 |
2013年 | 1021篇 |
2012年 | 447篇 |
2011年 | 583篇 |
2010年 | 467篇 |
2009年 | 522篇 |
2008年 | 562篇 |
2007年 | 576篇 |
2006年 | 536篇 |
2005年 | 492篇 |
2004年 | 450篇 |
2003年 | 454篇 |
2002年 | 430篇 |
2001年 | 595篇 |
2000年 | 372篇 |
1999年 | 260篇 |
1998年 | 147篇 |
1997年 | 164篇 |
1996年 | 171篇 |
1995年 | 188篇 |
1994年 | 179篇 |
1993年 | 131篇 |
1992年 | 164篇 |
1991年 | 172篇 |
1990年 | 168篇 |
1989年 | 141篇 |
1988年 | 156篇 |
1987年 | 96篇 |
1986年 | 128篇 |
1985年 | 127篇 |
1984年 | 122篇 |
1983年 | 114篇 |
1982年 | 120篇 |
1981年 | 120篇 |
1980年 | 87篇 |
1979年 | 99篇 |
1978年 | 101篇 |
1976年 | 92篇 |
1974年 | 104篇 |
1972年 | 87篇 |
1971年 | 85篇 |
1967年 | 100篇 |
1964年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Mitigation and Adaptation Strategies for Global Change - 相似文献
133.
134.
135.
Fetal aspartylglucosaminuria (AGU) was studied during the first trimester of pregnancy in six at-risk pregnancies using chorionic villus samples. The activity of aspartylglucosaminidase (AGA) was high in five cases, indicating an unaffected fetus. This was confirmed through delivery of healthy newborns with a normal pattern of urinary oligosaccharides. Low enzyme activity in an uncultured biopsy specimen and in cultured amniotic fluid cells in one case demonstrated that the fetus was affected. The pregnancy was terminated and the prenatal diagnosis was confirmed by showing reduced AGA activity in cultured fibroblasts of the fetus. 相似文献
136.
Dr. Linda A. Cannizzaro Barbara K. Hecht Helen A. Bixenman Stephen Pazdziorko Robert Tamis Frederick Hecht 《黑龙江环境通报》1988,8(4):297-301
We report herein a de novo unbalanced chromosome translocation in a fetus resulting from in vitro fertilization technology. Prenatal diagnostic analysis of an amniotic fluid revealed a 46,XX,4p+ karyotype. The origin of the extra material on the short arm of chromosome 4 could not be identified by a variety of banding techniques. However, examination of fetal parts did reveal some dysmorphic features. 相似文献
137.
K. Schmetzer 《Die Naturwissenschaften》1987,74(3):136-137
138.
139.
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
140.
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