全文获取类型
收费全文 | 31028篇 |
免费 | 323篇 |
国内免费 | 284篇 |
专业分类
安全科学 | 905篇 |
废物处理 | 1216篇 |
环保管理 | 4349篇 |
综合类 | 4550篇 |
基础理论 | 8370篇 |
环境理论 | 8篇 |
污染及防治 | 8541篇 |
评价与监测 | 1936篇 |
社会与环境 | 1548篇 |
灾害及防治 | 212篇 |
出版年
2022年 | 221篇 |
2021年 | 263篇 |
2020年 | 187篇 |
2019年 | 271篇 |
2018年 | 420篇 |
2017年 | 426篇 |
2016年 | 685篇 |
2015年 | 521篇 |
2014年 | 789篇 |
2013年 | 2585篇 |
2012年 | 942篇 |
2011年 | 1278篇 |
2010年 | 1027篇 |
2009年 | 1114篇 |
2008年 | 1353篇 |
2007年 | 1417篇 |
2006年 | 1281篇 |
2005年 | 1023篇 |
2004年 | 1095篇 |
2003年 | 1006篇 |
2002年 | 976篇 |
2001年 | 1268篇 |
2000年 | 901篇 |
1999年 | 529篇 |
1998年 | 434篇 |
1997年 | 386篇 |
1996年 | 439篇 |
1995年 | 469篇 |
1994年 | 462篇 |
1993年 | 408篇 |
1992年 | 405篇 |
1991年 | 363篇 |
1990年 | 411篇 |
1989年 | 397篇 |
1988年 | 340篇 |
1987年 | 305篇 |
1986年 | 279篇 |
1985年 | 281篇 |
1984年 | 329篇 |
1983年 | 326篇 |
1982年 | 322篇 |
1981年 | 308篇 |
1980年 | 248篇 |
1979年 | 275篇 |
1978年 | 221篇 |
1977年 | 200篇 |
1975年 | 189篇 |
1974年 | 166篇 |
1973年 | 187篇 |
1972年 | 217篇 |
排序方式: 共有10000条查询结果,搜索用时 843 毫秒
601.
Foci of calcification were observed at autopsy in the liver of a fetus with complete trisomy 9 on which two cordocenteses had been performed. It is suggested that liver calcifications are a possible complication of the procedure. As several other cases of calcifications in the liver and other organs of fetuses with autosomal trisomies have been described without a history of cordocentesis, further studies should be carried out to determine whether fetuses with chromosomal anomalies are more prone to thrombus formation and embolization. 相似文献
602.
Mosaic trisomy 9 was detected in an amniotic fluid cell culture from a 40-year-old woman evaluated because of advanced maternal age. After counselling, parents elected to terminate the pregnancy. On autopsy the fetus was found to have hydrocephalus and a single kidney. The diagnosis of trisomy 9 mosaicism was confirmed in cultured skin fibroblasts. This is the third reported case of trisomy 9 mosaicism diagnosed prenatally. 相似文献
603.
604.
605.
A case of spontaneous abortion after transcervical CVS is presented. Despite no evidence of bacteria in the vagina and cervix prior to sampling and the prophylactic use of Metronidazole, pathological evidence of chorioamnionitis was found. The implications of this are discussed. 相似文献
606.
607.
M. Schwartz M. Super J. Schmidtke C. Buys M. Farrall D. Halley M. Krawczak J. E. Poncin D. Loukopoulos M. Devoto 《黑龙江环境通报》1988,8(8):619-624
This paper presents data collected in Europe on 107 prenatal diagnoses of cystic fibrosis (CF) using linked DNA markers. To date, 38 children have been born without CF, as predicted, demonstrating the present rapid move from research to clinical genetic service. 相似文献
608.
At 10 weeks' gestation, chorionic villus biopsy was obtained from a woman at risk for Sanfilippo type C disease. Acetyl-CoA: α-glucosaminide N-acetyltransferase activity was markedly deficient. The pregnancy was terminated at 12 weeks' gestation and follow-up study on fetal fibroblasts confirmed the diagnosis. 相似文献
609.
A field study was conducted to evaluate the protozoan colonization patterns on artificial substrates in relation to organic pollution within a tropical harbour. The composition of protozoans and their succession rates on artificial substrates(polyurethane foam units) were compared between two field stations(A and B), and their presence were considered with regards to the prevailing water quality conditions at the study sites. Altogether 44 genera of flagellates and ciliates were documented. The common genera of flagellates encountered included Monas, Polytoma, and Chromalina. Among the ciliates, the predominant genera were Tetrahymena, Vorticella, Lagymophyra, and Heloiphyra. These groups exhibited characteristic successional patterns in relation to ambient water quality. At Station A, located close to the sewage outfall, the water quality parameters included poor Secchi-disc transparency(0.48 m), dissolved oxygen of 1.93 mg/ml, salinity of 18 psu, and temperature 31.3 degrees C. Here, the nanoflagellates (spumella) colonized first, followed by microcilliate(Tetrahymena) and sessile form(Vorticella). Station B, located on the seaward side, was characterized by relatively less-stressed environmental conditions with transparency 1.85 m and dissolved oxygen value of 6.04 mg/ml. Salinity of 27.27 psu, and mean temperature of 30 degrees C were recorded at "B". At this station, the nanoflagellate Polytoma was first documented to colonize on the substrates, followed by microcilliate(Lagynophrya) and suctorid(Heliophyra). These findings support the use of protozoans as indicator species for evaluating the hazards posed by organic pollution to natural estuarine communities. 相似文献
610.
High-performance permanent magnets 总被引:2,自引:0,他引:2
High-performance permanent magnets (pms) are based on compounds with outstanding intrinsic magnetic properties as well as
on optimized microstructures and alloy compositions. The most powerful pm materials at present are RE–TM intermetallic alloys
which derive their exceptional magnetic properties from the favourable combination of rare earth metals (RE=Nd, Pr, Sm) with
transition metals (TM=Fe, Co), in particular magnets based on (Nd,Pr)2Fe14B and Sm2(Co,Cu,Fe,Zr)17. Their development during the last 20 years has involved a dramatic improvement in their performance by a factor of >15 compared
with conventional ferrite pms therefore contributing positively to the ever-increasing demand for pms in many (including new)
application fields, to the extent that RE–TM pms now account for nearly half of the worldwide market. This review article
first gives a brief introduction to the basics of ferromagnetism to confer an insight into the variety of (permanent) magnets,
their manufacture and application fields. We then examine the rather complex relationship between the microstructure and the
magnetic properties for the two highest-performance and most promising pm materials mentioned. By using numerical micromagnetic
simulations on the basis of the Finite Element technique the correlation can be quantitatively predicted, thus providing a
powerful tool for the further development of optimized high-performance pms. 相似文献