全文获取类型
收费全文 | 24628篇 |
免费 | 316篇 |
国内免费 | 185篇 |
专业分类
安全科学 | 698篇 |
废物处理 | 1094篇 |
环保管理 | 3859篇 |
综合类 | 3728篇 |
基础理论 | 6715篇 |
环境理论 | 13篇 |
污染及防治 | 6273篇 |
评价与监测 | 1558篇 |
社会与环境 | 1013篇 |
灾害及防治 | 178篇 |
出版年
2021年 | 176篇 |
2019年 | 180篇 |
2018年 | 296篇 |
2017年 | 329篇 |
2016年 | 496篇 |
2015年 | 399篇 |
2014年 | 558篇 |
2013年 | 2070篇 |
2012年 | 725篇 |
2011年 | 1032篇 |
2010年 | 819篇 |
2009年 | 824篇 |
2008年 | 1035篇 |
2007年 | 1072篇 |
2006年 | 959篇 |
2005年 | 795篇 |
2004年 | 805篇 |
2003年 | 798篇 |
2002年 | 761篇 |
2001年 | 828篇 |
2000年 | 663篇 |
1999年 | 414篇 |
1998年 | 324篇 |
1997年 | 335篇 |
1996年 | 342篇 |
1995年 | 391篇 |
1994年 | 356篇 |
1993年 | 339篇 |
1992年 | 338篇 |
1991年 | 317篇 |
1990年 | 338篇 |
1989年 | 316篇 |
1988年 | 276篇 |
1987年 | 270篇 |
1986年 | 257篇 |
1985年 | 234篇 |
1984年 | 295篇 |
1983年 | 252篇 |
1982年 | 305篇 |
1981年 | 267篇 |
1980年 | 224篇 |
1979年 | 219篇 |
1978年 | 204篇 |
1977年 | 167篇 |
1976年 | 148篇 |
1975年 | 156篇 |
1974年 | 164篇 |
1973年 | 167篇 |
1972年 | 154篇 |
1971年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
691.
692.
693.
B. Sikkema-Raddatz R. H. Sijmons M. B. Tan-Sindhunata A. Y. Van Der Veen R. Brunsting B. De Vries J. R. Beekhuis D. J. Bekedam B. Van Aken B. De Jong 《黑龙江环境通报》1995,15(5):467-473
We report two cases of apparently balanced complex de novo chromosomal rearrangements (BCCR) detected prenatally at 17 weeks and 10 weeks of gestation, respectively. Chromosomes were studied using GTG-banding and fluorescent in situ hybridization (FISH). In one case four chromosomes and in the other case three chromosomes were involved in the rearrangements. One of the pregnancies was terminated and no external or internal abnormalities were detected at autopsy. The other pregnancy continued to term. Level III ultrasound examination showed no abnormalities. The child is now 3 years old and has neither congenital anomalies nor evidence of delayed psychomotor development. 相似文献
694.
Prenatal diagnosis in a pregnancy at risk for a juvenile B1 variant of GM2-gangliosidosis was carried out. The biochemical study of the cultured amniocytes and the affected fetal brain is reported. The results obtained show that the sulphated artificial substrate can be used in the diagnosis of B1 variant, but not the neutral one. The accumulation of GM2-ganglioside in the fetal brain of the B1 juvenile form and an infantile form of GM2-gangliosidosis (0 variant) was compared. 相似文献
695.
Vanessa M. Barnabei MD PhD David A. Krantz James N. Macri John W. Larsen Jr 《黑龙江环境通报》1995,15(12):1131-1134
We have applied our multimarker approach of maternal serum alpha-fetoprotein (AFP) and free-beta human chorionic gonadotropin (hCG) for Down syndrome screening to multiple gestations to assess its efficacy for improved detection of twin and triplet pregnancies. This study matched 225 cases of twin pregnancy and 39 cases of triplet pregnancy each with ten singleton pregnancies based on gestational week, race, time to receive sample, time of year of sample, and geographical area. The ratios of the MOM for each group at the tenth, 50th, and 90th percentiles were compared by the Wilcoxon test. Risks for twins were calculated using Bayes' rule, the age-related incidence of twins, and the levels of AFP and free-beta hCG. The tenth, 50th, and 90th percentiles of free-beta hCG MOMs in twin and triplet cases were 0.85, 1.99, and 4.51, and 1.38, 2.78, and 4.07, respectively. For AFP, the MOMs at these percentiles were 1.26, 1.91, and 2.99, and 2.02, 2.68, and 5.30, respectively. The twin and triplet distributions for each marker were statistically significantly different from the singleton distributions (P<0.0001) and from each other (P=0.0012). At a twin risk cut-off of 1 in 50, 77.4 per cent of all twin gestations can be detected in a second-trimester AFP and free-beta hCG screening protocol with 5.1 per cent of singleton pregnancies falsely identified as at risk for twins. Our dual marker protocol for mid-trimester pregnancy screening combining AFP and free-beta hCG can identify over 77 per cent of twin pregnancies in women less than 35 years of age. This benefit may contribute to an improved outcome of pregnancy by early detection of multiple gestation. 相似文献
696.
Miscanthus for Renewable Energy Generation: European Union Experience and Projections for Illinois 总被引:1,自引:0,他引:1
Heaton Emily A. Long Stephen P. Voigt Thomas B. Jones Michael B. Clifton-Brown John 《Mitigation and Adaptation Strategies for Global Change》2004,9(4):433-451
Mitigation and Adaptation Strategies for Global Change - 相似文献
697.
Industrial ecology: a new field or only a metaphor? 总被引:1,自引:0,他引:1
In the 10 years since industrial ecology first became a topic of academic interest, it has grown as a field of inquiry and has produced a community of practice in several sectors including academia, business, and government. Even as the shape of industrial ecology becomes clearer, questions remain as to its lasting power beyond the metaphor that gave it its distinctiveness. This paper examines the development of industrial ecology and assesses its progress towards becoming a field of academic inquiry. And, in a related analysis, I look at the progress industrial ecology has made in establishing itself as an institutional (cultural) basis for action in the above sectors. Ideas like industrial ecology must become institutionalized if they are to have much effect on the reality of everyday activities. 相似文献
698.
F. Khodabakhshi M. Abbaszadeh H. Eskandari S.R. Mohebpour 《Journal of Manufacturing Processes》2013,15(4):533-541
A modified method of severe plastic deformation (SPD) entitled constrained groove pressing-cross route (CGP-CR) was introduced for imposing a high magnitude of equivalent strain of about 2.32 per pass on the sheet form samples. The major benefit of this improved route compared to previous common route was the more homogeneity of strain in the rolling (RD) and transverse (TD) directions of sheets. In this study, low carbon steel samples were used for examination of evolutions in microstructure and mechanical properties during SPD via CGP-CR process. Mechanical properties improvement were measured by tensile and macro hardness tests. The results indicate that CGP-CR process can effectively improve tensile strength; and also, yield stress and hardness of as-received low carbon steel samples were improved up to about 100% after two deformation passes. Also, high magnitude of inhomogeneity can be observed in hardness distribution through first pass of the process which diminishes in the subsequent passes. Microstructural evolutions during process were monitored by optical microscopy observations and X-ray diffraction analysis. The results demonstrate that initial ferritic microstructure with grain size of about 30 μm was refined to a 225 nm cell structure after two passes of CGP-CR process. 相似文献
699.
700.