首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   147篇
  免费   15篇
  国内免费   3篇
  2023年   1篇
  2022年   5篇
  2021年   4篇
  2020年   4篇
  2019年   4篇
  2018年   7篇
  2017年   8篇
  2016年   3篇
  2015年   1篇
  2014年   2篇
  2013年   6篇
  2012年   3篇
  2011年   7篇
  2010年   2篇
  2009年   13篇
  2008年   12篇
  2007年   4篇
  2006年   11篇
  2005年   9篇
  2004年   5篇
  2003年   4篇
  2002年   4篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   5篇
  1995年   2篇
  1994年   3篇
  1993年   5篇
  1992年   1篇
  1991年   1篇
  1989年   3篇
  1988年   1篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有165条查询结果,搜索用时 15 毫秒
1.
Chemical and physical methods for dating skeletal remains were examined. Benzidine reaction, ultra-violet fluorescence, specific gravity and supersonic conductivity were carried out on 71 dated skeletal findings distributed over the span of the last 3,500 years. Results given by benzidine reaction and ultra-violet fluorescence basically coincide, and positive readings were obtained up to about 200–350 years. Values measured in specific gravity and supersonic conductivity testing show a parallel trend, pointing out a clear difference between samples of the three first centuries and the ones belonging to more ancient periods examined.  相似文献   
2.
C. Amoros  C. Jacquet 《Hydrobiologia》1987,145(1):333-341
Methodological investigations, using remains of Bosminidae and Chydoridae, were undertaken to study the development of ecosystems in former river channels. Four biotopes from two former channels of different ages were used in this work. The Copepoda and Cladocera populations characterized each of the 11 sampling stations in relation to ecological factors, which are linked to the development stage in each ecosystem. Analysis of only the Bosminidae and Chydoridae populations presented practically the same information as an analysis of the total populations of Copepoda and Cladocera. The distribution of Bosminidae and Chydoridae remains taken from the surficial sediments at the deepest point of each former channel strongly resembled the distribution of the living populations sampled at several stations during one full year. Therefore, Bosminidae and Chydoridae remains could provide us with pertinent information concerning each phase of ecological succession that occurs in abandoned river channels.  相似文献   
3.
Cladoceran populations, as revealed by sedimentary remains, were studied in six lakes which by diatom evidence have become strongly acidified during the past 30 years. The accumulation rates of cladoceran remains and in two of the most strongly acidified lakes both relative and absolute numbers ofBosmina greatly increased during this period. Species numbers were not reduced, but there were shifts in relative abundances of cladoceran species.Bosmina longispina dominated all the lakes. Low pH (4.7) seemed not to be straight-forwardly harmful toDaphnia longispina, but the relative abundances of this taxon were reduced because ofBosmina.  相似文献   
4.
Stratigraphy of cladoceran remains in the upper 18 cm of a sediment core from the Lake Černé was studied. The successive disappearance of Bosmina longispina, Daphnia longispina and Ceriodaphnia quadrangula from the upper layers of the sediment corresponds with our knowledge concerning the disappearance of these species from the open water.  相似文献   
5.
The key argument for the identification of prehistoric cannibalism is provided by analysis of close similarities in the treatment of human and animal remains. Such analysis requires precise data on depositional context, meticulous excavation records, detailed bone modification studies, a relatively large sample of human and animal postcranial bones, and data on local mortuary practices. With the exception of Fontbrégoua Cave, these necessary conditions are lacking at all Stone Age European sites where it has been hypothesized that cannibalism occurred. The alternative hypothesis of secondary burial practices has been proposed informally for some sites and, in a more formal and detailed way, for Krapina and Fontbrégoua. However, this hypothesis does not have a higher probability, is not justified by current data, and uses ethnographic analogies to prop up interpretations of materials for which contextual data are missing or have been neglected. At Fontbrégoua, cannibalism remains the simplest and most plausible explanation of the evidence; at Krapina and other sites the available evidence is insufficient to prove either secondary burial or cannibalism.  相似文献   
6.
The aberrant features of the genus Daubentonia, such as the superficially rodent-like dentition, the globose and foreshortened brain case, and the filiform third manual digit have long been known. But the current assessment of the genus as lemuriform, and within that group as closest to the indriids, depends upon greater weight being placed upon other characteristics such as the cranial arterial pattern, the molariform teeth, and the developmental characteristics of the dentition. Prior multivariate morphometric studies have shown that though the shoulder structure of Daubentonia is uniquely different from that of all other primates, the structure of its pelvis may not be especially different from that of many relatively non-specialized primates. A large series of studies have been summated here in which many different anatomical regions (shoulder, arm, forearm, forelimb as a whole, pelvis, femur, hindlimb as a whole, forelimb and hindlimb combined, and total bodily proportions including limbs, trunk, and head) have been characterized osteometrically in a wide range of primate genera. The resulting data sets have been studied by discriminant function analyses. The differences that have been found are large enough that it can be confidently asserted that in its postcranial skeleton, Daubentonia is more different from the primates as a whole than is any other primate genus. These differences are big enough that their statistical and biological significance is not at all in doubt, notwithstanding the very small numbers of available specimens of this rare genus. They are so great that functional implications exist though they cannot, in our present state of knowledge of the habits of the genus, be ascribed with any certainty. They are so great indeed, paralleling the enormous differences of Daubentonia from other primates in its dentition, skull and cheiridia, that we may prefer to keep open minds about its taxonomic placement.  相似文献   
7.
A simple discriminant function using midshaft femoral circumference for the determination of sex has been tested with 114 skeletons from the Libben Site, Ontario County, Ohio. The results have been shown to be 85% consistent with other, accepted means of determining sex. Femur circumference an be an aid to the sexual identification of poorly preserved and fragmentary skeletal remains.  相似文献   
8.
Cortical bone samples were removed from individual burials from Tomb Dk31 in the Dakhleh Oasis, Egypt. The tissue was disaggregated, stained with the DNA specific fluorescent dye DAPI and analyzed using the flow cytom-eter. DNA flow cytometry measures the cellular DNA content and this is correlated with modal chromosome content. When DNA is present in skeletal remains further investigations such as extracting, amplifying and sequencing may then be carried out. The method offers a relatively rapid and inexpensive means of pinpointing samples of skeletal DNA that can be further analyzed.  相似文献   
9.
The life cycle of the zygopteran odonate Lestes viridis in two seasonal streams in the Sierra Morena Mountains is inferred from size-frequency analyses of handnet samples of larvae and records of presence and reproductive activity of adults during three consecutive years. The egg stage (duration 5–6 months) overwinters, larval development is brief (6–8 weeks) and adults undergo a protracted, prereproductive, summer diapause (up to 3 months) before mating and ovipositing in late September, about one week after the first appreciable fall of rain, but before surface water reappears in the streams after having been absent for about four months during the hot, dry summer. Comparison between this life cycle and those of more northerly populations reveals a latitude-correlated cline in phenology resembling that found in some other northern hemisphere odonates that, like L. viridis, maintain an obligatorily univoltine life cycle at different latitudes.  相似文献   
10.
Macroscopic plant remains found in pisé material (clay or mud used in building), used as lining in pits at the Upper Egyptian Predynastic site of Adaïma were investigated. Comparison with assemblages from the sediment fills of these pits and with assemblages from other contexts in the same site demonstrated the taphonomical importance of pisé as a building material for the formation of the sites archaeological sediment. In particular, the influence of the pisé plant temper on the composition of plant assemblages in the sediment fills of the pits was brought to the fore. The choice of specific plant materials for their use as temper in pisé or mud bricks is shown, in particular that of barley (Hordeum vulgare) threshing remains. The importance of cereal processing by-products as construction material is also assessed in a wider economic context and compared with later Egyptian mud brick plant contents.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号