全文获取类型
收费全文 | 31075篇 |
免费 | 352篇 |
国内免费 | 285篇 |
专业分类
安全科学 | 920篇 |
废物处理 | 1221篇 |
环保管理 | 4368篇 |
综合类 | 5067篇 |
基础理论 | 8075篇 |
环境理论 | 14篇 |
污染及防治 | 8207篇 |
评价与监测 | 1958篇 |
社会与环境 | 1652篇 |
灾害及防治 | 230篇 |
出版年
2022年 | 211篇 |
2021年 | 260篇 |
2020年 | 194篇 |
2019年 | 250篇 |
2018年 | 409篇 |
2017年 | 447篇 |
2016年 | 678篇 |
2015年 | 555篇 |
2014年 | 790篇 |
2013年 | 2608篇 |
2012年 | 966篇 |
2011年 | 1287篇 |
2010年 | 1031篇 |
2009年 | 1160篇 |
2008年 | 1326篇 |
2007年 | 1412篇 |
2006年 | 1266篇 |
2005年 | 1034篇 |
2004年 | 1048篇 |
2003年 | 1022篇 |
2002年 | 940篇 |
2001年 | 1182篇 |
2000年 | 888篇 |
1999年 | 508篇 |
1998年 | 398篇 |
1997年 | 377篇 |
1996年 | 430篇 |
1995年 | 441篇 |
1994年 | 418篇 |
1993年 | 400篇 |
1992年 | 373篇 |
1991年 | 358篇 |
1990年 | 375篇 |
1989年 | 332篇 |
1988年 | 311篇 |
1987年 | 281篇 |
1986年 | 273篇 |
1985年 | 288篇 |
1984年 | 310篇 |
1983年 | 310篇 |
1982年 | 300篇 |
1981年 | 312篇 |
1980年 | 270篇 |
1979年 | 277篇 |
1978年 | 200篇 |
1977年 | 201篇 |
1975年 | 159篇 |
1974年 | 165篇 |
1973年 | 167篇 |
1972年 | 190篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
91.
We report three siblings from consecutive pregnancies affected with restrictive dermopathy (RD). During the second pregnancy, fetal behavioural development and growth were studied extensively using ultrasound at 1–4 week intervals. Dramatic and sudden changes occurred in fetal body movements and growth but not until the end of the second trimester of pregnancy. Prominent at that time were prolonged periods of fetal quiescence and very low heart rate variability, together with abnormally executed body movements of short duration. Retarded femoral development and jerky abrupt fetal body movements (abnormal movement quality) were already present in the early second trimester of pregnancy. Facial anomalies emerged despite the presence of fetal mouth movements. The clinical features of RD were only partly explained by present knowledge of skin development and the fetal akinesia deformation sequence hypothesis. Quantitative assessment of fetal movements proved to be a poor early marker for antenatal diagnosis of this disorder. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
92.
93.
We examined the impact of stressful job demands on employee attitudes and attendance. Using Karasek's (1979) theory of job decision latitude as the conceptual foundation, we hypothesized that mental and physical work demands would interact with employee beliefs of personal control. Survey data from 90 male manufacturing employees regarding their control beliefs were combined with objective job analysis data concerning mental and physical demands and one year's worth of archival data regarding unexcused absences, sick days, and days tardy. There were significant interactions between control and objective psychological demands that indicated that these demands were associated with higher levels of tardiness and sick days only under conditions of low perceived control. In contrast, subjective workload ratings showed no relationship with tardiness and sick days, but, in interaction with control, predicted work satisfaction and voluntary absence. We discussed these results in terms of a stress process that affects health-related attendance independent of employee attitudes. 相似文献
94.
95.
Paul C. James 《Conservation biology》1994,8(4):1161-1162
96.
97.
98.
99.
Ramos MC 《Journal of environmental management》2006,78(3):209-215
The application of organic wastes to improve soil physical characteristics in mechanized vineyards planted after land levelling is becoming a common practice in Mediterranean areas. It may be useful as an additional source of organic matter and nutrients, but these wastes could also have negative effects due to their metal content. The aim of the study was to evaluate the influence of compost application on soil metal contents in mechanized vineyard soils of the Spanish Mediterranean area, where this practice is repeated every three years. The study was carried out in a ten-year-old vineyard where the main soil type is Typic Calcixerept. Composted cattle manure was applied in alternate rows, at a rate of 40 Mgha(-1) dry-weight. Nine sampling points were located along the slopes of two plots: a levelled plot prepared for mechanization with large soil disturbance movements within the plot, and a plot of undisturbed soil. At each location, soil samples were taken in both treated and untreated soils. Total concentrations (digestion with aqua regia) and the extractable DTPA (Diethylene-triaminepentacetic)-CaCl2-TEA (Triethanolamine) fractions of Cu, Zn and Mn were analyzed in each sample. For Cu and Zn, the initial concentration was higher in the undisturbed plot. In both cases, total Cu and total Zn were positively affected by manure input and the concentration in treated soils was significantly higher than in untreated soil. For Mn, the initial concentration was higher in disturbed soils than in undisturbed ones, and although in both scenarios the concentrations increased with manure, no significant differences were found between treated and untreated soils. The extractable fraction also increased in treated versus untreated soils, although for Cu and Mn the extractable/total metal ratio was similar in treated and untreated soils. After one compost application, total metal contents increased significantly, particularly for Zn. Most of those metals are accumulated in the soil, due to the soil characteristics. 相似文献
100.
Schuller P Iroumé A Walling DE Mancilla HB Castillo A Trumper RE 《Journal of environmental quality》2006,35(5):1756-1763
Rapid and reliable methods for documenting soil erosion associated with forest harvest operations are needed to support the development of best management practices for soil and water conservation. To address this need, the potential for using 7Be measurements to estimate patterns and amounts of soil redistribution associated with individual post-harvest events was explored. The 7Be technique, which was originally developed for use on agricultural land, was employed to estimate soil redistribution associated with a period of heavy rainfall within a harvested forest area located in the Lake Region of Chile (39 degrees 44'7' S, 73 degrees 10'39' W; 22% slope; and mean annual rainfall 2300 mm yr(-1)). The results provided by the 7Be technique were validated against direct measurements of soil gain or loss during the same period obtained using erosion pins. The information produced by the two approaches was similar. The results of this study demonstrate the potential for using 7Be measurements to document event-based erosion in recently harvested forest areas. 相似文献