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91.
Tin mining, based largely on alluvial tin deposited along the line of the ancestral Ringarooma, began in 1875 and reached a peak in the period 1905-9. Output declined thereafter and, following a brief recovery during the Second World War, had virtually ceased by 1981. Neither the methods, location nor level of production remained constant during the mining era. The widespread use of hydraulic sluicing and the proximity of many mines to the main river were major factors contributing to the high rate of sediment supply, with the Briseis mine at Derby being the dominant source. Based on data from published and unpublished papers, and mine records, the variable nature of that supply was estimated using a procedure which takes account of the effects of storage and changing practices. Many input points supplied material but the overall pattern is one in which downstream reaches made later starts and reached later peaks, suggesting that they will continue to experience the effects of an increased sediment load for some time.  相似文献   
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The p-median problem is a powerful tool in analyzing facility location options when the goal of the location scheme is to minimize the average distance that demand must traverse to reach its nearest facility. It may be used to determine the number of facilities to site, as well as the actual facility locations. Demand data are frequently aggregated in p-median location problems to reduce the computational complexity of the problem. Demand data aggregation, however, results in the loss of locational information. This loss may lead to suboptimal facility location configurations (optimality errors) and inaccurate measures of the resulting travel distances (cost errors). Hillsman and Rhoda (1978) have identified three error components: Source A, B, and C errors, which may result from demand data aggregation. In this article, a method to measure weighted travel distances in p-median problems which eliminates Source A and B errors is proposed. Test problem results indicate that the proposed measurement scheme yields solutions with lower optimality and cost errors than does the traditional distance measurement scheme.  相似文献   
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This paper is concerned with the reciprocal relationship between migration and development in Third World settings. Using individual-level data for Venezuela, migration behavior is related to a person's age, educational attainment, gender, and characteristics of his/her place(s) of residence as an out-migrant, in-migrant, or stayer. Place characteristics are in terms of four groups based on employment patterns: the core, regional centers, resource frontiers, and traditional rural areas. Four questions are of concern. First, does development influence migration? All analyses indicate this is so. Second, does migration influence development? Findings are ambiguous in that places experiencing improvement in their mix of human capital lagged in the net number of persons obtained through migration whereas a gain in numbers was accompanied by deterioriation in human capital profiles. Third, was incipient polarization reversal occurring in Venezuela in the late 1960s, early 1970s? This paper departs from the usual approach by addressing this question in terms of human capital attributes instead of population aggregates. On this basis, polarization reversal is in evidence, particularly in regional centers. Finally, this study answers in the affirmative that places with different development characteristics generate migration streams differing in type, magnitude, explanation, and impact.  相似文献   
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Biogeographers, ecologists, palaeontologists, and conservation managers often deal with checklists in which not all individuals have been identified to a species level, or the accuracy of species identification is questionable. Is it possible and credible to investigate species richness based on such checklists? Studies on macrofauna in the Far Eastern seas, eastern Arctic seas, and adjacent waters of the Pacific and Arctic Oceans suggest that in different habitats and for diverse taxa, species, and higher taxa richness strongly correlate with each other and increase with an expansion in the study area and sample size according to the species–area law. Such an increase is higher in the bottom zone than in the pelagic. Species and higher taxa richness also show a decrease from lower to higher latitudes, which is in line with the Humboldt–Wallace’s law. According to Willis’ law and self-similarity in the organisation of taxonomic levels, species richness can be assessed based on the genus, family, and order richness. In other words, supraspecies richness itself can tell us the same as species richness and therefore certain global patterns revealed at the species level may also be revealed at the supraspecies level. Such a concordance in general trends among richness parameters at different taxonomic levels in practice implies that species richness can be studied based on lists that lack species identifications or lists with doubtful species identification. We suggest bolder use of supraspecies richness in science and practice, discussing the disadvantages and advantages of this approach.  相似文献   
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This article examines the visual and material culture of sixteenth-century elite ceremonial armours and the paradoxes inherent in using images of women to decorate them between 1525 and 1550. It argues that foreign invading forces and their allies exploited or inverted traditional gender binaries associated with the classical and humanist iconography of the Italian Renaissance, particularly its female allegorical forms, to visually signify power relationships between combatants during the Italian Wars. Rather than simply embodying masculinity, elaborate ceremonial armours with images of women are revealing of both ideals of masculinity and femininity during times of war. These portrayals were part of wider conversations about gender and power, about the strength and weaknesses of women, and, ultimately, women's inferior status to men, which were utilised in allegorical forms to make claims to authority on these elite forms of male dress.  相似文献   
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In September 1968, one of the authors (P. Mayes), having been appointed Head of Mission by the British Ministry of Overseas Development to act as advisor to the Jamaica National Trust Commission, made recommendations which formed the basis for the establishment of the Port Royal Project. The Project is concerned with the excavation, conservation and presentation of 17th century Port Royal, which was founded in 1655 and destroyed by an earthquake in 1692 (see Fig. 1). For the purposes of archaeology the area was divided into three: the Archaeological-Historical Reserve, encompassing the protected underwater area and lands currently occupied by government facilities at the west end of Port Royal; the area in the centre of Port Royal which is protected archaeologically by modern housing and the area at the east end of Port Royal in which it was proposed that commercial expansion should be allowed on land held on lease from the Jamaican government. Work began early in 1969 in a section of this last area, which was threatened, at that time, by the construction of an hotel. This area was part of the shoal water section of sunken Port Royal (see below and Fig. 2). Since that date excavation headquarters and conservation laboratories have been established in the old naval hospital and the construction of a major museum, the first phase of the presentation programme, has begun.  相似文献   
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