全文获取类型
收费全文 | 17705篇 |
免费 | 138篇 |
国内免费 | 129篇 |
专业分类
安全科学 | 465篇 |
废物处理 | 829篇 |
环保管理 | 1938篇 |
综合类 | 3459篇 |
基础理论 | 4015篇 |
环境理论 | 10篇 |
污染及防治 | 5032篇 |
评价与监测 | 1216篇 |
社会与环境 | 928篇 |
灾害及防治 | 80篇 |
出版年
2023年 | 103篇 |
2022年 | 267篇 |
2021年 | 282篇 |
2020年 | 151篇 |
2019年 | 175篇 |
2018年 | 385篇 |
2017年 | 382篇 |
2016年 | 554篇 |
2015年 | 397篇 |
2014年 | 576篇 |
2013年 | 1363篇 |
2012年 | 695篇 |
2011年 | 866篇 |
2010年 | 623篇 |
2009年 | 651篇 |
2008年 | 821篇 |
2007年 | 827篇 |
2006年 | 740篇 |
2005年 | 602篇 |
2004年 | 581篇 |
2003年 | 535篇 |
2002年 | 468篇 |
2001年 | 504篇 |
2000年 | 351篇 |
1999年 | 251篇 |
1998年 | 144篇 |
1997年 | 144篇 |
1996年 | 131篇 |
1995年 | 185篇 |
1994年 | 181篇 |
1993年 | 132篇 |
1992年 | 149篇 |
1991年 | 168篇 |
1990年 | 141篇 |
1989年 | 141篇 |
1988年 | 148篇 |
1987年 | 126篇 |
1986年 | 107篇 |
1985年 | 112篇 |
1984年 | 137篇 |
1983年 | 139篇 |
1982年 | 141篇 |
1981年 | 107篇 |
1980年 | 106篇 |
1979年 | 114篇 |
1978年 | 97篇 |
1977年 | 91篇 |
1976年 | 87篇 |
1975年 | 99篇 |
1974年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily. 相似文献
52.
53.
54.
5p deletion syndrome commonly known as cri du chat is well described in affected neonates with catlike cry and hypotonia. Karyotyping will usually show a deletion of the short arm of one chromosome 5 with variable breakpoints. Only a few cases have been reported prenatally, and the fetal form of the syndrome has not been clearly individualised. We report a new case of 5p deletion syndrome diagnosed prenatally in association with Dandy–Walker syndrome and agenesis of the corpus callosum. Other brain anomalies have been reported previously, but this unusual association suggests the use of a specific probe in the investigation of these malformations. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
55.
A. Coulomb L'Herminé A. Aboura S. Brisset L. Cuisset V. Castaigne P. Labrune R. Frydman Dr G. Tachdjian 《黑龙江环境通报》2003,23(11):938-943
Prader–Willi syndrome (PWS) results from either paternal deletion of 15q11–q13, or maternal uniparental disomy (UPD) of chromosome 15 or imprinting center mutation. Prenatal diagnosis of PWS is currently indicated for chromosomal parental translocation involving chromosome 15 and for decreased fetal movements during the third trimester of gestation. Here we present the prenatal diagnosis of PWS during the first trimester of gestation and autopsy findings. Chorionic villus sampling (CVS) was performed for advanced maternal age at 13 weeks' gestation. CVS showed mosaicism including cells with a normal karyotype and cells with trisomy 15. Amniocentesis showed cells with a normal karyotype. Molecular analysis demonstrated that the fetus had a typical PWS abnormal methylation profile and maternal disomy for chromosome 15. Fetal ultrasound examination showed slightly enlarged lateral ventricles and hypoplasic male external genitalia without intra-uterine growth retardation. The autopsy showed a eutrophic male fetus with facial dysmorphy, hypoplasic genitalia, abnormal position of both feet and posterior hypoplasia of the corpus callosum. This report points out that in a karyotypically normal fetus with ambiguous male external genitalia and cerebral anomalies, extensive cytogenetic and molecular biology studies are strongly recommended because of risk of PWS. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
56.
Linden F Vincent 《Natural resources forum》2003,27(2):108-116
Situations of water scarcity challenge sustainability and threaten small users' access to water. In response to this problem, there has been a search for a method of hydrological analysis that can better represent the needs of small water users. While this search is rooted in the debate favouring a more participatory and inclusive allocation of the resource, it also requires a new focus on smallholder hydrology that can confront the gaps and biases found in current hydrological practices in many countries. This article looks at past hydrological practices and also at results of recent studies, highlighting the perspective of smallholder irrigators in surface water planning in Zimbabwe, and groundwater planning in India. These case studies show that wider social forces, not always best science, drive hydrological practices. However, new frameworks focusing on the water user can emerge for more equitable and sustainable water management. 相似文献
57.
58.
Stéphanie Couvreur-Lionnais Thierry Rousseau Nicole Laurent Christel Thauvin-Robinet Eve Senet-Lacombe Anne Lise Delezoïde Francine Mugneret Christine Durand Laurence Faivre Paul Sagot 《黑龙江环境通报》2005,25(2):172-175
Juberg–Hayward syndrome is a rare autosomal recessive syndrome characterised by the association of growth retardation, microcephaly, cleft lip and palate, and thumb and radial ray abnormalities. To date, no prenatal cases have been reported. Here, we report on the first prenatal case of Juberg–Hayward syndrome. The diagnosis was established following fetopathological study. Besides the cardinal features of the syndrome, this prenatal case was remarkable for the severity of the short arm malformation and by the finding of big toe agenesis and cerebral abnormalities including hydrocephalus, agenesis of corpus callosum, and cerebellar hypoplasia. We conclude that the diagnosis of Juberg–Hayward syndrome can be discussed prenatally following ultrasound diagnosis of the association of intrauterine growth restriction, microcephaly, thumb/radial anomalies, and cleft lip/palate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
59.
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices. 相似文献
60.
The possible involvement of calmodulin-dependent processes in the control of Na+ and Cl- transport pathways has been investigated on isolated, perfused preparations of salt-transporting posterior gills of the euryhaline Chinese crab Eriocheir sinensis (collected near Emden, Germany in autumn 1990). The anti-calmodulin phenothiazine drugs Chlorpromazine and Trifluoperazine induced depolarization of the transepithelial potential only when added to the serosal bathing saline (socalled in). This effect is best interpreted by assuming a disturbance of the conductive Cl- pathways located at the baso-lateral side of the epithelium. In agreement with that conclusion is the fact that Trifluoperazine inhibits the Cl- transepithelial influx. Trifluoperazine also induces inhibition of the Na+ influx when added either to the incubation (out) or to the perfusion (in) medium. These results indicate inhibitory effects of the anticalmodulin drug on both the Na+/K+ pump and leak system located at the serosal side and on the Na+/H+ exchange located at the apical side of the epithelium. 相似文献