全文获取类型
收费全文 | 26949篇 |
免费 | 159篇 |
国内免费 | 129篇 |
专业分类
安全科学 | 360篇 |
废物处理 | 1490篇 |
环保管理 | 3262篇 |
综合类 | 4654篇 |
基础理论 | 7103篇 |
环境理论 | 9篇 |
污染及防治 | 5830篇 |
评价与监测 | 2091篇 |
社会与环境 | 2382篇 |
灾害及防治 | 56篇 |
出版年
2022年 | 113篇 |
2021年 | 130篇 |
2019年 | 112篇 |
2018年 | 1741篇 |
2017年 | 1638篇 |
2016年 | 1534篇 |
2015年 | 370篇 |
2014年 | 393篇 |
2013年 | 1179篇 |
2012年 | 893篇 |
2011年 | 2033篇 |
2010年 | 1281篇 |
2009年 | 1224篇 |
2008年 | 1641篇 |
2007年 | 2051篇 |
2006年 | 627篇 |
2005年 | 599篇 |
2004年 | 587篇 |
2003年 | 680篇 |
2002年 | 676篇 |
2001年 | 642篇 |
2000年 | 421篇 |
1999年 | 306篇 |
1998年 | 212篇 |
1997年 | 207篇 |
1996年 | 230篇 |
1995年 | 238篇 |
1994年 | 245篇 |
1993年 | 220篇 |
1992年 | 203篇 |
1991年 | 210篇 |
1990年 | 200篇 |
1989年 | 172篇 |
1988年 | 173篇 |
1987年 | 158篇 |
1986年 | 158篇 |
1985年 | 155篇 |
1984年 | 198篇 |
1983年 | 181篇 |
1982年 | 177篇 |
1981年 | 154篇 |
1980年 | 139篇 |
1979年 | 128篇 |
1978年 | 139篇 |
1977年 | 119篇 |
1976年 | 106篇 |
1975年 | 109篇 |
1974年 | 121篇 |
1971年 | 99篇 |
1967年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 863 毫秒
481.
482.
Andreas Züttel 《Mitigation and Adaptation Strategies for Global Change》2007,12(3):343-365
Hydrogen storage and transportation or distribution is closely linked together. Hydrogen can be distributed continuously in
pipelines or batch wise by ships, trucks, railway or airplanes. All batch transportation requires a storage system but also
pipelines can be used as pressure storage system. Hydrogen exhibits the highest heating value per weight of all chemical fuels.
Furthermore, hydrogen is regenerative and environment friendly. There are two reasons why hydrogen is not the major fuel of
toady’s energy consumption: First of all, hydrogen is just an energy carrier. And, although it is the most abundant element
in the universe, it has to be produced, since on earth it only occurs in the form of water. This implies that we have to pay
for this energy, which results in a difficult economic task, because since the industrialization we are used to consuming
energy for free. The second difficulty with hydrogen as an energy carrier is the low critical temperature of 33 K, i.e. hydrogen
is a gas at room temperature. For mobile and in many cases also for stationary applications the volumetric and gravimetric
density of hydrogen in a storage system is crucial. Hydrogen can be stored by six different methods and phenomena: high pressure
gas cylinders (up to 800 bar), liquid hydrogen in cryogenic tanks (at 21 K), adsorbed hydrogen on materials with a large specific
surface area (at T < 100 K), absorbed on interstitial sites in a host metal (at ambient pressure and temperature), chemically bond in covalent
and ionic compounds (at ambient pressure), oxidation of reactive metals e.g. Li, Na, Mg, Al, Zn with water. These metals easily
react with water to the corresponding hydroxide and liberate the hydrogen from the water. Finally, the metal hydroxides can
be thermally reduced to the metals in a solar furnace. 相似文献
483.
L. Bovicelli M.D. F. M. Picchio G. Pilu G. Baccarani L. F. Orsini N. Rizzo G. Alampi P. M. Benenati J. C. Hobbins 《黑龙江环境通报》1984,4(1):67-72
In a case of fetal heart failure caused by endocardial fibroelastosis, prenatal echocardiography clearly demonstrated; a thickened endocardium. We therefore suggest that an abnormal endocardium may be detected in utero by ultrasound, thus representing an important clue in the differential diagnosis of fetal nonimmune hydrops and in the evaluation of pregnancies at risk for endocardial fibroelastosis. 相似文献
484.
M. S. Ristaldi M. Pirastu C. Rosatelli G. Monni H. Erlich R. Saiki Professor A. Cao 《黑龙江环境通报》1989,9(9):629-638
In this study, we describe a simple strategy to detect β-thalassaemia mutations in prospective parents and to make prenatal diagnosis in pregnancies at risk in the Mediterranean population. Screening of prospective parents is carried out by dot blot analysis on enzymatically amplified DNA with a set of oligonucleotide probes complementary to the most common mutations in this population. Prenatal diagnosis is accomplished by the same procedure on enzymatically amplified amniocyte or trophoblast DNA. The main advantages of this procedure are the simplicity, sensitivity (0.05 μg of DNA), and rapidity (12–24 h). Further simplification is obtained by amplification of the DNA from crude amniotic cell lysate. The very low amount of fetal material necessary for this analysis eliminates the need to culture amniotic fluid cells and may decrease the fetal loss rate associated with trophoblast sampling. The number of specific DNA sequences obtained by the amplification procedure allowed us to use non-radioactive labelled oligonucleotide probes, which have several advantages compared to radioactive probes. 相似文献
485.
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
486.
Prenatal diagnosis on chorionic villous tissue was performed for a woman with the karyotype 46,XX,t(2;18)(q32;q12)—a subtle ‘difficult’ translocation. The case illustrates the necessity of good quality cytogenetics for accurate prenatal diagnosis. For chorionic villi this can be obtained only with long-term culture. 相似文献
487.
488.
489.
490.
P. A. Hurley Mr R. H. T. Ward B. Teisner R. K. Iles M. Lucas J. G. Grudzinskas 《黑龙江环境通报》1993,13(10):903-908
Serum PAPP-A measurements taken from 254 women in the first trimester are reported. Eleven chromosomal abnormalities were detected. The mean serum PAPP-A levels in cases of Down syndrome were 0.44 MOM at 9 weeks gestation, 0.15 MOM at 10 weeks, and 0.29 MOM at 11 weeks. The PAPP-A level at 10 weeks was below those of pregnancies which aborted spontaneously. At 11 weeks, the pregnancies with Down syndrome recorded the lowest PAPP-A levels at that gestation. On this small sample, offering chorionic villus sampling to women with singleton pregnancies and a PAPP-A level below 0.3 MOM (approximately 6.5 per cent of this at-risk group) would have detected all the Down syndrome fetuses at 10 weeks and 50 per cent at 11 weeks without selecting those cases destined to abort. This suggests that serum PAPP-A should continue to be investigated as a potential first-trimester screening test for Down syndrome. 相似文献