全文获取类型
收费全文 | 33221篇 |
免费 | 359篇 |
国内免费 | 241篇 |
专业分类
安全科学 | 884篇 |
废物处理 | 1358篇 |
环保管理 | 4535篇 |
综合类 | 5446篇 |
基础理论 | 9238篇 |
环境理论 | 14篇 |
污染及防治 | 8521篇 |
评价与监测 | 2053篇 |
社会与环境 | 1547篇 |
灾害及防治 | 225篇 |
出版年
2022年 | 217篇 |
2021年 | 241篇 |
2019年 | 250篇 |
2018年 | 426篇 |
2017年 | 425篇 |
2016年 | 686篇 |
2015年 | 488篇 |
2014年 | 742篇 |
2013年 | 2580篇 |
2012年 | 926篇 |
2011年 | 1308篇 |
2010年 | 1084篇 |
2009年 | 1066篇 |
2008年 | 1366篇 |
2007年 | 1395篇 |
2006年 | 1285篇 |
2005年 | 1057篇 |
2004年 | 1087篇 |
2003年 | 1031篇 |
2002年 | 980篇 |
2001年 | 1280篇 |
2000年 | 911篇 |
1999年 | 549篇 |
1998年 | 439篇 |
1997年 | 437篇 |
1996年 | 452篇 |
1995年 | 519篇 |
1994年 | 512篇 |
1993年 | 447篇 |
1992年 | 464篇 |
1991年 | 443篇 |
1990年 | 482篇 |
1989年 | 461篇 |
1988年 | 403篇 |
1987年 | 375篇 |
1986年 | 338篇 |
1985年 | 329篇 |
1984年 | 400篇 |
1983年 | 355篇 |
1982年 | 403篇 |
1981年 | 361篇 |
1980年 | 294篇 |
1979年 | 323篇 |
1978年 | 281篇 |
1977年 | 233篇 |
1975年 | 229篇 |
1974年 | 250篇 |
1973年 | 239篇 |
1972年 | 247篇 |
1971年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
481.
Circulating placental [human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), decidual (pregnancy protein) 12 (PP12), and fetal alphafetoprotein (AFP)] proteins were measured immediately before and within 1 h in 18 women undergoing diagnostic chorionic villus sampling (CVS) in the first trimester. An elevation of serum AFP levels was consistently seen, while fluctuations in excess of 10 per cent of the pre-CVS levels of SP1 and PP12 were seen in the majority of patients. Fluctuations in hCG and PAPP-A were consistently less than 10 per cent of pre-CVS values. Post-CVS changes in levels were not apparently associated with any feature of the technique, the pregnancy, or its outcome (one missed abortion). As feto-maternal haemorrhage is a common event, anti-D should be offered to rhesus-negative women undergoing CVS. In the prediction of subsequent miscarriage, only hCG and PAPP-A measurements should be considered. 相似文献
482.
483.
484.
485.
486.
487.
488.
489.
A very dry climate which prevailed during the last glacial maximum of the Pleistocene from India to the Sahara, was replaced by variable weather conditions with alternating more or less humid phases, starting from the Pleistocene-Holocene transition period and lasting up to about 3000 years ago, when present arid conditions set in. A particularly wet phase is recognized throughout the region some 5000 years ago. Phase shifts within the region and in particular changes in rain distribution patterns, are interpreted as due to shifting spheres of influence of the monsoonal circulation, of Atlantic depressions and moisture originating from the Mediterranean Sea. The condition of the Mediterranean Sea itself, which is influenced by runoff and melt waters from the European Continent and by the Nile floods, as well as by the eustatic sea-level changes, is not a good indicator of local climate conditions. 相似文献
490.
Neither the “Green Revolution” in the developing countries nor “yield explosion” in the agricultural production of the industrialized nations have reached the genetic and physiologic limits of crop growth. Breeding of better varieties is still the most promising defense against hunger. The ambiguity of modern agroindustry throughout the world resides in its high dependence on the existence of functional technological, economical, and political systems.
相似文献