全文获取类型
收费全文 | 5584篇 |
免费 | 46篇 |
国内免费 | 28篇 |
专业分类
安全科学 | 116篇 |
废物处理 | 257篇 |
环保管理 | 385篇 |
综合类 | 1072篇 |
基础理论 | 1327篇 |
环境理论 | 5篇 |
污染及防治 | 1759篇 |
评价与监测 | 419篇 |
社会与环境 | 296篇 |
灾害及防治 | 22篇 |
出版年
2023年 | 57篇 |
2022年 | 136篇 |
2021年 | 155篇 |
2020年 | 80篇 |
2019年 | 89篇 |
2018年 | 188篇 |
2017年 | 209篇 |
2016年 | 272篇 |
2015年 | 184篇 |
2014年 | 282篇 |
2013年 | 426篇 |
2012年 | 307篇 |
2011年 | 356篇 |
2010年 | 236篇 |
2009年 | 198篇 |
2008年 | 331篇 |
2007年 | 293篇 |
2006年 | 245篇 |
2005年 | 200篇 |
2004年 | 175篇 |
2003年 | 153篇 |
2002年 | 122篇 |
2001年 | 80篇 |
2000年 | 41篇 |
1999年 | 49篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 25篇 |
1995年 | 81篇 |
1994年 | 58篇 |
1993年 | 49篇 |
1992年 | 61篇 |
1991年 | 48篇 |
1990年 | 37篇 |
1989年 | 24篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 26篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1972年 | 9篇 |
1966年 | 16篇 |
1965年 | 10篇 |
1957年 | 9篇 |
1956年 | 11篇 |
1954年 | 9篇 |
排序方式: 共有5658条查询结果,搜索用时 15 毫秒
1.
Cornus stolonifera, Salix petiolaris, and Spiraea alba
clones already located within the corridor of an electrical power line. To
establish the efficiency of treatments, we examined the statistical
differences of growth traits between species and treatments.
An analysis of the effects of layering shows, after the first growth season,
differences for all growth traits in only one species, Spiraea alba.
After the second growth season, we observed the development of new aerial
stems. Layering favors horizontal expansion of shrubs over height
development. The third year after treatment, the effect of layering is
reduced except for Cornus stolonifera, which continuously increases,
as shown by the significant progression of the clone issued from the layer
even five years after treatments. With the cutting back technique, we
expected a distinct vertical growth of the shrubs at the expense of
increasing the crown diameter. This technique would be best associated with
the rejuvenation of clones, followed by a layering of new shoots to allow a
horizontal expansion of the shrubs. Therefore, the formation of a dense shrub
community by layering should be considered a valuable approach for the
biological control of undesirable trees in powerline rights-of-way. 相似文献
2.
3.
Cynthia J. Sims MD Don T. Fujito Dennis R. Burholt Josef Dadok Harlan R. Giles D. Allan Wilkinson 《黑龙江环境通报》1993,13(6):473-480
We have investigated the ability of high-resolution proton NMR spectroscopy to provide a biochemical constituent screening of human amniotic fluid (AF). Proton NMR spectra were obtained at 300 MHz on AF from patients undergoing amniocentesis in the mid-trimester. Only AF from normal pregnancies (normal fetal karyotype, normal a-fetoprotein levels, normal birth outcome) was used in this study. The AF supernatant was lyophilized and resuspended in deuterated water containing 0.1 mm phosphate buffer and 6.02 mm disodium maleate. Identification of low molecular weight compounds was confirmed by two-dimensional NMR spectra (primarily correlated spectroscopy, or COSY) and standard addition techniques. A broad profile of compounds were ‘NMR visible’ in a single proton spectrum, including creatinine, glucose, organic acids (acetate, citrate, and lactate) and several amino acids (alanine, histidine, leucine, phenylalanine, tyrosine and valine). The proton spectrum was unaffected by prior freezing/thawing of AF samples. We were able to quantify compounds by comparison with an added concentration standard (maleate) at concentrations as low as 30 μm. Good agreement with literature values based on other analytical techniques was obtained. 相似文献
4.
5.
P. Robbins-Furman J. T. Hecht M. Rocklin N. Maklad G. Greenhaw I. Wilkins MD 《黑龙江环境通报》1995,15(2):179-182
The diagnosis of Freeman–Sheldon syndrome was made by ultrasonographic evaluation of a 20-week fetus with a positive family history. The ultrasonographic features were abnormalities of the extremities and mouth. 相似文献
6.
Finn Stener Jørgensen MD 《黑龙江环境通报》1995,15(5):419-429
The aim of the study was to describe the opinion of pregnant women who had accepted or declined an alpha-fetoprotein (AFP) test, not only on AFP screening in general, but also on whether every pregnant woman should be offered amniocentesis (AC)/chorionic villus sampling (CVS) and an ultrasound scan for fetal malformations. An additional aim was to describe pregnant women's attitudes concerning continued research in the prenatal field. The study was performed as a questionnaire study in two regions over a 1-year period from 1 October 1988 to 30 September 1989. Results are based on answers from 3331 women who had taken an AFP test and 336 women who had declined the offer of a test. A total of 79 per cent of the women thought that an AFP test, 70 per cent that an ultrasound scan for fetal malformations, and 26 per cent that AC or CVS should be offered to all pregnant women. Fifty-nine per cent of the women were positive towards continued research in the prenatal field. Women who had had an AFP test were generally much more positive towards screening and research than women who had declined, who were generally against. Women who had left school without a high school degree were on average more positive towards the screening issues than women who had this degree. In conclusion, the results obtained in this study strongly suggest that women's attitudes are very dependent on how the prenatal screening programme is already organized in their local area. 相似文献
7.
Uterine lavage affords the potential for non-invasive human blastocyst recovery, with obvious potential for preimplantation genetic diagnosis. In an effort to duplicate in women the multiple blastocyst recovery per cycle that can be achieved in several other species, we initiated a programme in which fertile women underwent superovulation, followed by lavage and embryo collection. We superovulated 15 fertile women, aged 21–40, in 29 cycles using one of four regimens. Insemination was by either intercourse or artificial intracervical donor insemination with cryopreserved sperm from men of proven fertility. In 28 of 29 cycles, the uterus was lavaged daily for 1, 2, or 3 days between 5 and 10 days after human chorionic gonadotropin (hCG) administration or luteinizing hormone (LH) surge. Almost total fluid volume was recovered in every lavage. There were no retained pregnancies and no complications. Surprisingly, only two morulae, one blastocyst, and four unfertilized ova were recovered. Thus, alterations in ovulation induction, insemination timing, or lavage techniques must be contemplated in order to increase the blastocyst yield and thus fulfil the potential of uterine lavage for preimplantation diagnosis. 相似文献
8.
We report relatively high citrulline concentration in amniotic fluid of a citrullinemic fetus suggesting that prenatal detection of this condition could be done on this basis in conjunction with a direct or an indirect determination of argininosuccinate synthetase activity in amniotic fluid cells. 相似文献
9.
10.