全文获取类型
收费全文 | 15316篇 |
免费 | 162篇 |
国内免费 | 126篇 |
专业分类
安全科学 | 525篇 |
废物处理 | 607篇 |
环保管理 | 2324篇 |
综合类 | 2529篇 |
基础理论 | 3952篇 |
环境理论 | 14篇 |
污染及防治 | 3804篇 |
评价与监测 | 1003篇 |
社会与环境 | 738篇 |
灾害及防治 | 108篇 |
出版年
2023年 | 82篇 |
2022年 | 139篇 |
2021年 | 131篇 |
2020年 | 104篇 |
2019年 | 128篇 |
2018年 | 236篇 |
2017年 | 213篇 |
2016年 | 326篇 |
2015年 | 261篇 |
2014年 | 359篇 |
2013年 | 1187篇 |
2012年 | 521篇 |
2011年 | 707篇 |
2010年 | 558篇 |
2009年 | 628篇 |
2008年 | 709篇 |
2007年 | 737篇 |
2006年 | 633篇 |
2005年 | 561篇 |
2004年 | 485篇 |
2003年 | 507篇 |
2002年 | 455篇 |
2001年 | 549篇 |
2000年 | 396篇 |
1999年 | 267篇 |
1998年 | 181篇 |
1997年 | 198篇 |
1996年 | 214篇 |
1995年 | 233篇 |
1994年 | 237篇 |
1993年 | 198篇 |
1992年 | 172篇 |
1991年 | 192篇 |
1990年 | 197篇 |
1989年 | 174篇 |
1988年 | 127篇 |
1987年 | 137篇 |
1986年 | 145篇 |
1985年 | 110篇 |
1984年 | 127篇 |
1983年 | 138篇 |
1982年 | 147篇 |
1981年 | 134篇 |
1980年 | 111篇 |
1979年 | 126篇 |
1978年 | 77篇 |
1977年 | 84篇 |
1975年 | 85篇 |
1974年 | 71篇 |
1973年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
191.
192.
193.
The main objective of this project was to evaluate the possibility of reducing the quantity of fibre wasted at one of many hydrocyclone (centrifugal) cleaning processes in a paper mill. It was found that the application of elutriation water to both the tertiary and quaternary cleaners was essential to minimise the fibre discharged to the sewer, and the pressure of this elutriation water had a dramatic effect of reducing the fibre wastage. Accordingly, it has been shown that 150–160 kPa as the optimum pressure range to apply elutriation water to minimise the product grade fibre wasted whilst sending undesired shive fibre to the sewer. Also, monitoring of the press uhle box wastewater revealed that the paper mill has the potential to make substantial cost savings by reducing the waste stream. Further investigation is necessary to determine the types of fibre that are being wasted, and the viability of a screen to recycle the wasted fibre to the process. However, these fibres may be unsuitable to reuse in the process and alternative uses must be found. 相似文献
194.
Maguelone G. Forest Hervé Bétuel Philippe Couillin André Boué Michel David Daniel Floret René Francois Pierre Guibaud Henri Plauchu Raphaël Rappaport 《黑龙江环境通报》1981,1(3):197-207
Amniotic fluid (AF) levels of 17-hydroxyprogesterone (17OHP) and testosterone (T) were determined at 16–17 weeks in 17 pregnancies at risk for CAH and results compared to 75 normal controls. The fetus was predicted to be unaffected in 12 cases on the findings of normal AF levels of both 17OHP and T and the latter allowed a correct prediction of fetal sex in all instances. HLA typing confirmed normality in 12 cases revealing 5 carriers, 5 homozygous normal and 2 indeterminate. Steroid levels of the 2 groups were similar. Three fetuses were predicted to be CAH affected on unambiguously high levels of 17OHP and T (in female only). HLA typing was in agreement, and the diagnosis was confirmed in 2 abortuses and a female newborn by physical and hormonal studies. In the last 2 cases AF levels of OHP and T were normal but HLA (A/B/C) genotypes were identical to the CAH affected siblings. Normal physical and hormonal findings in the 2 aborted fetuses would exclude the possibility of an in utero virilizing form of CAH. The discrepancy could be explained on the basis that the fetuses had an allelic form of 21-hydroxylase deficiency or on the basis of recombination (not fully tested). It is concluded that a fully informative prenatal diagnosis of CAH should not rely entirely on HLA typing but on hormonal studies. 相似文献
195.
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
196.
197.
198.
199.
200.