全文获取类型
收费全文 | 10275篇 |
免费 | 160篇 |
国内免费 | 86篇 |
专业分类
安全科学 | 399篇 |
废物处理 | 463篇 |
环保管理 | 1665篇 |
综合类 | 1348篇 |
基础理论 | 2646篇 |
环境理论 | 9篇 |
污染及防治 | 2327篇 |
评价与监测 | 704篇 |
社会与环境 | 879篇 |
灾害及防治 | 81篇 |
出版年
2023年 | 77篇 |
2022年 | 120篇 |
2021年 | 111篇 |
2020年 | 90篇 |
2019年 | 107篇 |
2018年 | 193篇 |
2017年 | 219篇 |
2016年 | 288篇 |
2015年 | 187篇 |
2014年 | 303篇 |
2013年 | 817篇 |
2012年 | 393篇 |
2011年 | 540篇 |
2010年 | 413篇 |
2009年 | 450篇 |
2008年 | 505篇 |
2007年 | 503篇 |
2006年 | 465篇 |
2005年 | 396篇 |
2004年 | 367篇 |
2003年 | 360篇 |
2002年 | 315篇 |
2001年 | 337篇 |
2000年 | 253篇 |
1999年 | 168篇 |
1998年 | 114篇 |
1997年 | 116篇 |
1996年 | 115篇 |
1995年 | 139篇 |
1994年 | 137篇 |
1993年 | 122篇 |
1992年 | 115篇 |
1991年 | 100篇 |
1990年 | 101篇 |
1989年 | 88篇 |
1988年 | 88篇 |
1987年 | 93篇 |
1986年 | 96篇 |
1985年 | 80篇 |
1984年 | 90篇 |
1983年 | 90篇 |
1982年 | 100篇 |
1981年 | 68篇 |
1980年 | 61篇 |
1979年 | 47篇 |
1978年 | 58篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1974年 | 36篇 |
1972年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
41.
42.
43.
44.
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
45.
A study was undertaken to establish the role of free amino acids (FAA) in aerobic energy dissipation in embryos of turbot (Scophthalmus maximus) which contain an oil globule in the egg. Laboratory-reared developing eggs and larvae (15°C, 34 salinity) were measured for oxygen uptake, ammonia excretion, contents of FAA, protein, and ammonium, and volumes of yolksac and oil globule. Newly spawned eggs from different batches contained 55 to 90 nmol egg–1 of FAA. Resorption of FAA occurred in parallel with the consumption of yolk. Resorption of the oil globule, however, occurred predominantly after hatching and mainly after yolk resorption. The combined data suggest that approximately 70% of the FAA are utilized as an energy substrate, while the rest are polymerized into body proteins. FAA become a significant energy substrate in the early egg stage and account for 100% of the aerobic energy dissipation 2 d after Fertilization then decrease to ca. 60% at the time of hatching. Lipids derived from the oil globule seem to be the main fuel after hatching and account for ca. 90% of the energy dissipation at the onset of first-feeding. Thus, the energetics of fish embryos which contain an oil globule seems to be different from those that depend exclusively on the nutritional reserves of the yolk. 相似文献
46.
Stabilimenta characteristics of the spider Argiope argentata on small islands: support of the predator-defense hypothesis 总被引:2,自引:0,他引:2
Summary A variety of orb-weaving spider species construct stabilimenta, patterned areas of dense silk, typically near the hub of the orb. The adaptive significance of this construction, along with associated behaviors such as shuttling and vibrating, is much debated. Arigiope argentata on small islands of the Bahamas frequently possess stabilimenta; we studied 397 individuals of this species to investigate possible functions of their stabilimenta, paying particular attention to predator-defense hypotheses. Cruciform stabilimenta were commoner in all size classes of spiders than discoid stabilimenta or no stabilimentum at all; discoid stabilimenta occurred mostly among intermediate size classes. Within the cruciform type, two-segmented stabilimenta were especially common among the very smallest spiders. Size of cruciform stabilimenta showed a curvilinear relation to spider body length; the fitted curve for total segment length had a maximum at an intermediate spider length. We argue that this relationship (among other phenomena) supports an apparently-larger-size hypothesis, whereby intermediate-sized spiders in particular appear much larger than they actually are. This could discourage predators, including those that are gape-limited such as lizards. We argue that stabilimenta in the smallest spiders, in which typically two segments are opposed, so that they more or less line up, serve as camouflage. When disturbed experimentally, spiders with discoid stabilimenta shuttle to the opposite side of the centrally located stabilimentum. This seems an obvious defensive behavior and occurs less frequently among spiders with cruciform stabilimenta. Large spiders vibrate more frequently than small ones, but no relation exists between vibration frequency and stabilimentum type. We argue (see also Tolbert 1975) that vibrating behavior, in which the spider can become a blur, renders its location more difficult to discern and the spider more difficult to grasp, rather than increasing apparent size.
Correspondence to: T.W. Schoener 相似文献
47.
Cape JN Sheppard LJ Fowler D Harrison AF Parkinson JA Dao P Paterson IS 《Environmental pollution (Barking, Essex : 1987)》1992,75(2):229-236
Radioactive sulphate (35SO4) was applied to the soil below a Scots pine forest on 23 June 1989, and its movement into the canopy and into throughfall and stemflow was measured over 4 months. The specific activity, Bq (mg S)(-1), of the canopy increased monotonically; uptake by current-year (1989) expanding needles was initially twice as fast as by older needles or live twigs. By 10 October the canopy average specific activity was 62 Bq (mg S)(-1). The specific activity of net throughfall (throughfall + stemflow - rain), deduced from measurements from six throughfall collectors, six stemflow collectors and two rain collectors, fell rapidly from 12.6 Bq (mg S)(-1) in late July to <1 Bq (mg S)(-1) in mid-August. The results suggest (assuming rapid equilibration of 35S with sulphate in soil) that root-derived sulphate contributed c. 3% of sulphate in net throughfall and that dry deposition of SO2 and sulphate particles contributed c. 97% of the 0.56 g S m(-2) measured in net throughfall over the period. Simultaneous measurements of SO2 at canopy height and of NH3 above and within the canopy gave mean concentrations of 5.9 and 0.86 microg m(-3), respectively, sufficient to account for the sulphate measured in net throughfall only if codeposition of NH3 and SO2 occurred to canopy surfaces. The large values of specific activity observed in July, however, indicate that throughfall composition may be closely related to recent soil input of sulphate, and that equilibrium cannot be safely assumed. The possibility of a significant contribution of soil-derived sulphate to sulphate deposition in net throughfall cannot be ruled out on the basis of this experiment. 相似文献
48.
Summary The leaf gland volatile oils of ten sweet gale plants from a Scottish population were extracted in early summer. The results differed notably from reports of other populations in respect of the sesquiterpenes, -elemenone and germacrone, which were major components of the volatile oil. Three dihydrochalcones were also detected in the volatile oil. Variation within the population existed, particularly with respect to the relative importance of germacrone. Five plants were resampled in late summer and exhibited a marked reduction in -elemenone, a lesser reduction in germacrone and changes in the proportions of some monoterpenes. 相似文献
49.
Russian Journal of Ecology - Populations at the border of ranges are considered more vulnerable than those in the center. However, some recent reviews contradict this hypothesis. We have studied... 相似文献
50.
Shahpari Ghazal Sadeghi Hossein Ashena Malihe García-León David 《Environment, Development and Sustainability》2022,24(3):4110-4127
Environment, Development and Sustainability - In the last two decades, recurring drought becomes a challenge for Iran’s economy, which is located in a drought-prone area, and it has been... 相似文献