全文获取类型
收费全文 | 1039篇 |
免费 | 112篇 |
专业分类
1151篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 14篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 47篇 |
2014年 | 47篇 |
2013年 | 59篇 |
2012年 | 81篇 |
2011年 | 95篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 52篇 |
2007年 | 49篇 |
2006年 | 48篇 |
2005年 | 48篇 |
2004年 | 49篇 |
2003年 | 43篇 |
2002年 | 28篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1985年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1972年 | 5篇 |
1971年 | 8篇 |
1970年 | 7篇 |
1969年 | 6篇 |
1967年 | 4篇 |
1964年 | 5篇 |
1963年 | 9篇 |
1962年 | 4篇 |
1961年 | 6篇 |
1958年 | 4篇 |
1943年 | 4篇 |
排序方式: 共有1151条查询结果,搜索用时 0 毫秒
1.
Benzene, an accepted leukemogen, has been suggested to cause other hemato- and lymphopoietic cancers. Here we review the published literature for non-Hodgkin lymphoma (NHL) and occupational exposure to benzene. Six cohorts, sixteen case–control studies and two studies of other designs were identified through keyword searches of bibliographic databases. Twenty-two of twenty-four studies found no association between NHL and ever exposed to benzene compared to never; a random-effects meta-analysis gave a pooled risk estimate of 1.11 (95% confidence interval 0.94–1.30). Our finding of no effect agrees with one of two previous meta-analyses. The other meta-analysis examined if high benzene exposure increased NHL risk but a lack of consistent exposure categories within the same metric should have precluded pooling risks by exposure level. Instead, we reviewed whether dose–response relationships existed. The best available data came from six studies where exposure was estimated from historical measurements and on the whole, no trends in risks of NHL with rising cumulative, average, peak, or duration of benzene exposure were found. NHL is a heterogeneous group of malignancies and although less well-studied, benzene was not associated with any NHL subtype. In conclusion, benzene at either low or high doses does not increase the risk of NHL. 相似文献
2.
Eleanor LeBourdais 《CMAJ》1988,139(10):1002-1003
3.
4.
Eleanor Leacock 《Dialectical Anthropology》1985,10(1-2):69-91
Conclusion Though relatively little direct attention has been given by Marxist anthropologists to a theory of individual behavior and thought in relation to societal processes, the above partial summary indicates the wealth of insight that is available for elaborating such a theory. In addition, there are of course significant developments in the field of psychology, notably the attention to activity as central to individual personality [], the renewed concern with levels of integration theory [], and the burgeoning interest in Vygotsky's writings on language, thought, and culture []. There are also the continuing attempts to locate Freud's positive contributions in a historical materialist frame [].Where, then, is psychological anthropology? As always, producing a richness of suggestive materials — such as those on varying conceptions of the self — but, as a glance at the pages of Ethos will show, unfortunately not engaged in fundamental theoretical innovation. By way of illustration, let me cite Spindler's The Making of Psychological Anthropology, a collection of articles by major figures, past and present. Spindler's introductory essay is thoughtful; always the teacher, he presents with consideration and modesty the history of the field, the disfavor into which it fell (in large part due to the methodlogical travesties of national character studies), and its stubborn persistence (following from the pervasive interest in the psychological dimension that has always characterized cultural anthropology). He summarizes ongoing problems as perceived from within the field, and as the major difficulty to be overcome pinpoints cultural overdeterminism and its inadequacy for explaining variations. The solution? Not the necessity of respecting history and focussing on how individuals variously understand and relate (according to their individual histories) to the established structures whereby particular societies produce, allocate, and consume basic goods, and how they variously respond to disjunctions in these structures even as they reproduce them. Instead Spindler writes, ... if we are to escape the double bind of our cultural overdeterminism, we are going to have to go beyond culture and even ecology, to biochemistry, to physiology and neurology, to genetics — to biology in the broadest sense of the term [].In closing, let me say to the reader, do not simply turn away in dismay. One must conclude that it is imperative to continue to build a solid alternative theory of relations among individual behaviors, individual understandings, cultural values, and societal processes, or, in other words, to replace a non-historical and essentially biological paradigm with a dialectical and materialist view of human action.Eleanor Leacock is Professor of Anthropology and Chair at the City College, City University of New York.
相似文献
相似文献
5.
Most carcinogens, including polycyclic aromatic hydrocarbons (PAH), require metabolic activation to produce the ultimate electrophilic species that bind covalently with cellular macromolecules to trigger the cancer process. Metabolic activation of PAH can be understood in terms of two main pathways: one-electron oxidation to yield reactive intermediate radical cations and monooxygenation to produce bay-region diol epoxides. The reason we have postulated that one-electron oxidation plays an important role in the activation of PAH derives from certain common characteristics of the radical cation chemistry of the most potent carcinogenic PAH. Two main features common to these PAH are: 1) a relatively low ionization potential, which allows easy metabolic removal of one electron, and 2) charge localization in the PAH radical cation that renders this intermediate specifically and efficiently reactive toward nucleophiles. Equally important, cytochrome P-450 and mammalian peroxidases catalyze one-electron oxidation. This mechanism plays a role in the binding of PAH to DNA. Chemical, biochemical and biological evidence will be presented supporting the important role of one-electron oxidation in the activation of PAH leading to initiation of cancer. 相似文献
6.
Kathleen D. Murray Eleanor Groden Francis A. Drummond A. Randall Alford Richard H. Storch Michael D. Bentley 《Entomologia Experimentalis et Applicata》1996,80(3):503-510
The effects of citrus limonoids, applied topically to potato (Solanum tuberosum L. var. Katahdin) foliage, on Colorado potato beetle (Leptinotarsa decemlineata) (Say) (Chrysomelidae) larval development, growth, and survival were quantified in laboratory assays and a small-plot field test. In laboratory assays, survival, development rate, and body weight decreased with increasing limonoid concentration, however these measures of larval response did not significantly differ among varying periods of limonoid exposure (three, six, or nine days). Significant limonoid application concentration and frequency effects on survival, development rate, and defoliation were observed in the field test. These results indicate the potential utility of lethal and non-lethal effects of citrus limonoids for management of the Colorado potato beetle. 相似文献
7.
8.
During mate choice, receivers often assess the magnitude (duration, size, etc.) of signals that vary along a continuum and reflect variation in signaller quality. It is generally assumed that receivers assess this variation linearly, meaning each difference in signalling trait between signallers results in a commensurate change in receiver response. However, increasing evidence shows receivers can respond to signals non-linearly, for example through Weber's Law of proportional processing, where discrimination between stimuli is based on proportional, rather than absolute, differences in magnitude. We quantified mate preferences of female green swordtail fish, Xiphophorus hellerii, for pairs of males differing in body size. Preferences for larger males were better predicted by the proportional difference between males (proportional processing) than the absolute difference (linear processing). This demonstration of proportional processing of a visual signal implies that receiver perception may be an important mechanism selecting against the evolution of ever-larger signalling traits. 相似文献
9.
10.
Arthur C. Mathieson Clayton A. Penniman Paula K. Busse Eleanor Tveter-Gallagher 《Journal of phycology》1982,18(3):331-336
The, effects of ice on Ascophyllum nodosum (L.) Le Jolis within the Great Bay Estuary System of New Hampshire-Maine, U.S.A. were assessed during the winter of 1980–81. Approximately 50% of the plants late fall standing crop, or an estimated 136 tonnes dry weight, was removed by ice-rafting. Pieces of Ascophyllum removed averaged 22 cm in length, 15 g in fresh weight and generally represented 2–3 years of growth. Although the winter of 1980–81 wax somewhat extreme, a similar pruning process probably occurs each year contributing to the characteristic bushy habit of attached inner estuarine plants. Ascophyllum fragments rafted in ice and deposited into salt marshes are suggested as a major source of the, ecad scorpioides (Hornemann) Hauck. 相似文献