全文获取类型
收费全文 | 29955篇 |
免费 | 260篇 |
国内免费 | 292篇 |
专业分类
安全科学 | 821篇 |
废物处理 | 1231篇 |
环保管理 | 3798篇 |
综合类 | 5288篇 |
基础理论 | 7598篇 |
环境理论 | 9篇 |
污染及防治 | 8058篇 |
评价与监测 | 2041篇 |
社会与环境 | 1470篇 |
灾害及防治 | 193篇 |
出版年
2022年 | 238篇 |
2021年 | 246篇 |
2020年 | 164篇 |
2019年 | 230篇 |
2018年 | 419篇 |
2017年 | 421篇 |
2016年 | 655篇 |
2015年 | 515篇 |
2014年 | 830篇 |
2013年 | 2381篇 |
2012年 | 963篇 |
2011年 | 1249篇 |
2010年 | 984篇 |
2009年 | 1126篇 |
2008年 | 1289篇 |
2007年 | 1330篇 |
2006年 | 1183篇 |
2005年 | 1024篇 |
2004年 | 995篇 |
2003年 | 976篇 |
2002年 | 954篇 |
2001年 | 1222篇 |
2000年 | 857篇 |
1999年 | 511篇 |
1998年 | 355篇 |
1997年 | 358篇 |
1996年 | 402篇 |
1995年 | 419篇 |
1994年 | 411篇 |
1993年 | 331篇 |
1992年 | 341篇 |
1991年 | 335篇 |
1990年 | 355篇 |
1989年 | 315篇 |
1988年 | 315篇 |
1987年 | 249篇 |
1986年 | 261篇 |
1985年 | 259篇 |
1984年 | 266篇 |
1983年 | 265篇 |
1982年 | 273篇 |
1981年 | 275篇 |
1980年 | 213篇 |
1979年 | 243篇 |
1978年 | 188篇 |
1977年 | 174篇 |
1976年 | 164篇 |
1975年 | 165篇 |
1973年 | 163篇 |
1972年 | 175篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
231.
Sulphate leaching losses may reduce the long-term possibility of maintaining the S supply of crops in low input farming systems. The ability of catch crops (Italian ryegrass (Lolium multiflorum Lam), winter rape (Brassica napus L.) and fodder radish (Raphanus sativus L.)) to reduce soil sulphate concentrations in autumn and make it available to a succeeding crop was investigated in 1996–1998 on sandy loam soil in Denmark. All catch crops reduced soil sulphate concentrations in the autumn compared to bare soil. Especially, the cruciferous catch crops had the ability to deplete efficiently soil sulphate levels and thus, reduce the sulphate leaching potential. The S uptake in aboveground catch crop was 8, 22 and 36 kg S per ha for ryegrass, winter rape and fodder radish, respectively. In the following spring, sulphate levels of the autumn bare soil were low in the top 0.5 m and a peak of sulphate was found at 0.75–1 m depth. In contrast, where a fodder radish catch crop had been grown, high sulphate levels were present in the top 0.5 m, but only small amounts of sulphate were found at 0.5–1.5 m depth. In spring barley (Hordeum vulgare L.), that followed catch crops, S concentrations at heading and maturity revealed that the availability of soil S increased following winter rape and fodder radish, whereas there were indications that following ryegrass, the S availability was reduced compared to bare soil. This initial study showed that catch crops have a high potential for reducing sulphate leaching and may be used to synchronise S availability with plant demand in a crop rotation. 相似文献
232.
Becker E. W. Bier W. Ehrfeld W. Schubert K. Schütte R. Seidel D. 《Die Naturwissenschaften》1976,63(9):407-411
The Science of Nature - The development of reliable manufacturing methods for commercial separation elements, the successful operation of separative stages, and extensive tests performed on plant... 相似文献
233.
J. Altenburger Th. Dielacher P. Eder H. Ferner M. Fegerl J. Fresner O. Gelinek A. Kogler J. Jantschgi M. Nussbaumer B. Russegger H. Schnitzer K. Schauer B. Sebesta J. Seiler F. Sprenger H. Widenmeyer 《Journal of Cleaner Production》1994,2(3-4)
The paper focuses upon the organization of a federal state-funded pollution prevention project in the Styrian industry. The project includes 13 companies from the textile, pulp and paper, machine building, wood working and printed circuit board manufacturing industries, covering most of the sectors and sizes in the Styrian industry. It started in January 1994 and will last for one year. It will demonstrate the possibilities of pollution prevention and the need for further research work. This project will make use of the methods and tools that were refined in the Austrian Prepare project. As a first step, a systematic balance of all the inputs and outputs of a company is made, after which the weak points and inefficiencies of material and energy use are identified and the options for improvements, both economical and ecological, are defined. Consequently, modifications in products and production lead to a situation with less waste and emissions. The preliminary lessons from these projects are presented: as a rule, the utilities (consumption of process materials and water, cleaning, energy, preparatory and finishing steps) are treated as black boxes and usually represent a considerable optimization potential. In these areas especially there is usually a lack of information and coordination as well as a need for a systematic and comprehensive approach. Leadership in the company and creative consultants are needed for starting lasting successful pollution prevention projects. 相似文献
234.
C. K. Jørgensen 《Die Naturwissenschaften》1980,67(4):188-189
235.
Mendel Z Dunkelblum E Branco M Franco JC Kurosawa S Mori K 《Die Naturwissenschaften》2003,90(7):313-317
The biological activity of the Matsucoccus spp. sex pheromones and diene modified analogs has been tested in forests of Israel and Portugal in order to explore the structure-activity relationship of the pine bast scale pheromone/kairomone system. The response of the adult predatory bugs, Elatophilus hebraicus and E. crassicornis and of the brown lacewing, Hemerobius stigma is more selective than that of the conspecific Matsucoccus males. The removal of the terminal methyl group from the diene terminus of both pheromones 1 and 2 eliminates all kairomonal activity but retains moderate pheromonal activity. Addition of a methyl group to the diene terminus of pheromones 1 and 2 sustains full pheromonal and kairomonal activities of the Elatophilus spp. but eliminates entirely the kairomonal activity of H. stigma. Subtle designed alterations in the structure of the diene group, typical of all Matsucoccus pheromones, change the mode of the kairomonal activity markedly. 相似文献
236.
The importance of selenium as an essential trace element has progressively emerged during the last years due to the analysis of selenium deficiency diseases and to the identification and characterization of a number of selenoenzymes. Selenium is incorporated in the catalytic site of the enzymes as an integral selenocysteine residue. The pathway of selenocysteine biosynthesis and incorporation has been elucidated recently for Escherichia coli. This article presents an overview on these subjects and describes the mechanisms which confer selenocysteine specificity in the framework of protein biosynthesis. In addition, some considerations concerning the phylogeny of selenocysteine incorporation are presented and a model for the evolution of the selenocysteine pathway is proposed. 相似文献
237.
E. Lamla F. Boschke G. Traving G. Pfotzer H. Wolter W. Walcher H. D. Dahmen H. J. Queisser W. W. Klingbeil K. Beyermann O. Müller R. R. Ernst D. Reinen H. Muth W. Becker G. Wunsch G. I. Distler L. Jaenicke H. G. v. Schnering H. Werner F. Reiff H. Schimassek W. Höll H. K. Vasil W. F. Angermeier W. Ruppel J. C. Eccles G. Spiteller H. Oettel W. Vogell P. Brosche K. J. Hsü H. -U. Schmincke 《Die Naturwissenschaften》1975,62(3):143-143
238.
239.
240.
Two patients referred for evaluation of very high maternal serum alpha-fetoprotein (10–20 multiples of the median) were carrying triploid fetuses with placentas showing features of partial hydatidiform mole. The diagnosis of fetal triploidy should be considered when there is a very high maternal serum alpha-fetoprotein and no ultrasound evidence of open neural tube defect, ventral wall defect, or any other explanation. Therefore, chromosomal analysis of amniotic fluid cells in such cases is essential. 相似文献