全文获取类型
收费全文 | 90529篇 |
免费 | 1272篇 |
国内免费 | 1351篇 |
专业分类
安全科学 | 3813篇 |
废物处理 | 3281篇 |
环保管理 | 13969篇 |
综合类 | 21524篇 |
基础理论 | 26290篇 |
环境理论 | 74篇 |
污染及防治 | 14598篇 |
评价与监测 | 5375篇 |
社会与环境 | 3662篇 |
灾害及防治 | 566篇 |
出版年
2022年 | 838篇 |
2021年 | 836篇 |
2020年 | 713篇 |
2019年 | 873篇 |
2018年 | 1132篇 |
2017年 | 1174篇 |
2016年 | 2190篇 |
2015年 | 1859篇 |
2014年 | 2607篇 |
2013年 | 9305篇 |
2012年 | 2258篇 |
2011年 | 2569篇 |
2010年 | 3321篇 |
2009年 | 3459篇 |
2008年 | 2044篇 |
2007年 | 1905篇 |
2006年 | 2271篇 |
2005年 | 2238篇 |
2004年 | 2560篇 |
2003年 | 2379篇 |
2002年 | 1922篇 |
2001年 | 2180篇 |
2000年 | 1968篇 |
1999年 | 1496篇 |
1998年 | 1366篇 |
1997年 | 1359篇 |
1996年 | 1476篇 |
1995年 | 1576篇 |
1994年 | 1461篇 |
1993年 | 1320篇 |
1992年 | 1302篇 |
1991年 | 1276篇 |
1990年 | 1232篇 |
1989年 | 1188篇 |
1988年 | 1037篇 |
1987年 | 971篇 |
1986年 | 985篇 |
1985年 | 1066篇 |
1984年 | 1161篇 |
1983年 | 1160篇 |
1982年 | 1173篇 |
1981年 | 1095篇 |
1980年 | 942篇 |
1979年 | 925篇 |
1978年 | 817篇 |
1977年 | 716篇 |
1976年 | 637篇 |
1975年 | 603篇 |
1973年 | 632篇 |
1972年 | 636篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
281.
Mamoru Morikawa Kazutoshi Cho Soromon Kataoka Emi H. Kato Takashi Yamada Hideto Yamada Hisanori Minakami 《黑龙江环境通报》2005,25(3):250-252
Two cases with a large cystic mass within the placenta are reported. By ultrasonography, it was found that both women had a subchorionic hypoechoic lesion (11.0 × 4.8 × 4.0 cm and 6.6 × 3.7 × 2.2 cm, respectively) at 24 and 35 weeks of gestation, respectively. In both cases, turbulent blood flow generated by a pulsatile jet flow (pulse rate; 40 to 60 beats per minute) into the cystic lesion seen on real-time imaging and lesions being low intensity on T1-weighted and isointensity on T2-weighted magnetic resonance image suggested that they contained fresh maternal blood. In both cases, the sonolucency of the lesions did not change until cesarean deliveries of females, both of whom were small-for-gestational-age infants (1940 g at 37 weeks and 2195 g at 37 weeks, respectively). Biochemical analysis of the fluid in the cystic lesion sampled during the cesarean section in the latter case confirmed that the fluid had originated from the maternal blood. These lesions histologically corresponded to large avillous areas surrounded by normal villi. Thus, a huge placental lake was diagnosed in both cases. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
282.
283.
M. Marcelli M. Caburazzi A. Perilli V. Piermattei E. Fresi 《Chemistry and Ecology》2005,21(5):351-367
The towed undulating vehicle (TUV), named SARAGO, was used for two fine-scale surveys between the Italian and the Sardinian coasts during the Astraea 2 cruise (6-7 and 26-27 September 1995), studying the deep chlorophyll maximum distribution. SARAGO sections identify a sub-surface doming with higher chlorophyll a and primary production concentrations in the upwelling area of a cyclonic gyre region, detected by sea-surface temperature images. In the first section, the cyclone presents a double doming, in density and salinity, with shallower and concentrated patches of chlorophyll a for about 2 miles. Twenty days later, the second section shows that the gyre changes shape and extension, showing a single doming with higher primary production and chlorophyll a concentrations, distributed over a large area of about 40 nautical miles. SARAGO allows analysis of this high-variability phenomenon (cyclonic gyre) and allows concentrated patches (2 nm) to be identified, thus proving the importance of TUVs in the study of mesoscale processes. 相似文献
284.
285.
286.
Spilt notochord syndrome is an extremely rare form of spinal dysraphism characterized by a complete cleft of the spine and a persistent communication between endoderm and ectoderm. A variant of split notochord syndrome was diagnosed in a 25-week-old fetus showing a prolapsed congenital colostomy and a spinal cystic lesion. The final diagnosis included protruding colon segment, imperforate anus with a rectourethral fistula and lipomyelomeningocele. The ultrasound features of the condition and the post-natal management are discussed. The neonate was successfully treated with a posterior sagittal anorectoplasty, while the lipomyelomeningocele was resected at a later stage. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
287.
288.
289.
290.
JOSEPH P. DUDLEY 《Conservation biology》1995,9(5):1332-1334