全文获取类型
收费全文 | 4118篇 |
免费 | 21篇 |
国内免费 | 52篇 |
专业分类
安全科学 | 82篇 |
废物处理 | 142篇 |
环保管理 | 458篇 |
综合类 | 1016篇 |
基础理论 | 915篇 |
环境理论 | 4篇 |
污染及防治 | 916篇 |
评价与监测 | 289篇 |
社会与环境 | 360篇 |
灾害及防治 | 9篇 |
出版年
2022年 | 36篇 |
2021年 | 67篇 |
2020年 | 33篇 |
2019年 | 37篇 |
2018年 | 64篇 |
2017年 | 61篇 |
2016年 | 93篇 |
2015年 | 56篇 |
2014年 | 120篇 |
2013年 | 325篇 |
2012年 | 123篇 |
2011年 | 182篇 |
2010年 | 122篇 |
2009年 | 167篇 |
2008年 | 162篇 |
2007年 | 178篇 |
2006年 | 142篇 |
2005年 | 118篇 |
2004年 | 111篇 |
2003年 | 130篇 |
2002年 | 120篇 |
2001年 | 138篇 |
2000年 | 97篇 |
1999年 | 65篇 |
1998年 | 33篇 |
1997年 | 41篇 |
1996年 | 25篇 |
1995年 | 55篇 |
1994年 | 35篇 |
1993年 | 37篇 |
1992年 | 38篇 |
1991年 | 40篇 |
1990年 | 49篇 |
1989年 | 40篇 |
1988年 | 29篇 |
1987年 | 32篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 38篇 |
1982年 | 26篇 |
1981年 | 41篇 |
1980年 | 30篇 |
1979年 | 30篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1975年 | 26篇 |
1972年 | 23篇 |
1970年 | 24篇 |
1966年 | 23篇 |
1965年 | 23篇 |
排序方式: 共有4191条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
75.
76.
I. Shagina H. L. Dadali V. P. Sitnikov V. V. Pugachev N. A. Malygina O. V. Evgrafov 《黑龙江环境通报》1995,15(1):27-34
Ninety-two families with spinal muscular atrophy (SMA) applied for genetic counselling and further prenatal diagnosis. To minimize expenses, only one tightly linked informative marker was determined in the course of preliminary examination, and non-radioactive allele detection was preferably used. Four prenatal diagnoses of SMA type I, four of SMA type II, and one of SMA type III were made. This trial programme shows the considerable requirements, importance, and potential effectiveness of prenatal prediction of SMA in Russia. 相似文献
77.
A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features. 相似文献
78.
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
79.
80.
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