全文获取类型
收费全文 | 24624篇 |
免费 | 316篇 |
国内免费 | 184篇 |
专业分类
安全科学 | 698篇 |
废物处理 | 1094篇 |
环保管理 | 3859篇 |
综合类 | 3728篇 |
基础理论 | 6715篇 |
环境理论 | 13篇 |
污染及防治 | 6268篇 |
评价与监测 | 1558篇 |
社会与环境 | 1013篇 |
灾害及防治 | 178篇 |
出版年
2021年 | 176篇 |
2019年 | 180篇 |
2018年 | 296篇 |
2017年 | 328篇 |
2016年 | 496篇 |
2015年 | 399篇 |
2014年 | 558篇 |
2013年 | 2070篇 |
2012年 | 725篇 |
2011年 | 1032篇 |
2010年 | 819篇 |
2009年 | 824篇 |
2008年 | 1035篇 |
2007年 | 1072篇 |
2006年 | 959篇 |
2005年 | 795篇 |
2004年 | 805篇 |
2003年 | 798篇 |
2002年 | 761篇 |
2001年 | 828篇 |
2000年 | 663篇 |
1999年 | 414篇 |
1998年 | 324篇 |
1997年 | 335篇 |
1996年 | 342篇 |
1995年 | 391篇 |
1994年 | 356篇 |
1993年 | 339篇 |
1992年 | 338篇 |
1991年 | 317篇 |
1990年 | 338篇 |
1989年 | 316篇 |
1988年 | 276篇 |
1987年 | 270篇 |
1986年 | 257篇 |
1985年 | 234篇 |
1984年 | 295篇 |
1983年 | 252篇 |
1982年 | 305篇 |
1981年 | 267篇 |
1980年 | 224篇 |
1979年 | 219篇 |
1978年 | 204篇 |
1977年 | 167篇 |
1976年 | 148篇 |
1975年 | 156篇 |
1974年 | 164篇 |
1973年 | 167篇 |
1972年 | 154篇 |
1971年 | 158篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
381.
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
382.
A population of 1639 patients were seen for chorionic villus sampling (CVS). Embryonic death was identified at ultrasound in 5.3 per cent of patients. The number of patients undergoing CVS was 1551, with 1416 transcervical procedures and 135 transabdominal procedures. The most common indication for CVS was advanced maternal age. Spontaneous pregnancy losses identified by increased risk of pregnancy loss with increasing aspiration attempts. The total fetal loss for this population was 5.4 per cent with the pregnancy loss estimated due to procedure being 1.2 per cent. Analysis of placentae from patients having CVS and amniocen-tesis showed no differences. Microbiological assessment prior to CVS was similar to previous publications. 相似文献
383.
The de-O-sulphation of α-linked glucosamine-6-sulphate residues in heparan sulphate requires a specific sulphatase, glucosamine-6-sulphatase, which has been shown to be deficient in tissues of Sanfilippo D, or mucopolysaccharidosis type IIID (MPS IIID), patients. MPS IIID fibroblasts cultured in Basal Eagle's medium supplemented with either fetal calf serum or heat-inactivated fetal calf serum, MDCB or Ultraserg media had residual glucosarnine-6-sulphatase activities towards a heparin-derived trisaccharide substrate, O-(α-N-acetylglucosamine-6-sulphate)-(1→4)-L -O-(α-iduronic acid-2-sulphate)-(1→4)-D -O-2,5-anhydro [1-3H]mannitol-6-sulphate, GlcNAc6S-IdoA2S-anM6S, which were less than 1 per cent of the normal range for fibroblasts cultured in Basal Eagle's medium supplemented with fetal calf serum. However, the glucosamine-6-sulphatase activities of MPS IIID fibroblasts grown in Chang's medium were similar to the activities in normal control fibroblasts which were cultured in Basal Eagle's medium. These results indicate that caution is required for prenatal diagnosis of MPS IIID patients using chorionic villi or amniotic cells cultured in Chang's medium. 相似文献
384.
385.
Cysts of the choroid plexus of the lateral ventricle can be detected in the fetus during routine scanning at 16–18 weeks' gestation with an approximate incident of one in every 120 pregnancies. It is likely that in a high percentage of cases cysts are bilateral and that their recent discovery is mainly due to improvements in imaging technology. Although the great majority of cases resolve and do not result in any morbidity, five cases of trisomy 18 and one case of trisomy 21 associated with fetal choroid plexus cysts have been reported. In this prospective study, choroid plexus cysts were detected in 42 fetuses, resulting in 40 normal infants and 2 cases of trisomy 18. It is concluded that there may be a relationship between fetal choroid plexus cysts and trisomy 18. In order to obtain a more precise and accurate result, a multi-centre prospective study is being organized. 相似文献
386.
Dr. Mertin haben wir für seine Hilfe bei der Interpretation der elektronenmikroskopischen Aufnahmen, der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie für ihre finanzielle Unterstützung zu danken. 相似文献
387.
388.
A de novo paracentric inversion of chromosome 11 identified through antenatal diagnosis is described along with long-term follow-up information on the child and discussion of reported experiences with de novo inversions. 相似文献
389.
390.