全文获取类型
收费全文 | 689656篇 |
免费 | 80715篇 |
国内免费 | 856篇 |
出版年
2016年 | 8068篇 |
2015年 | 11785篇 |
2014年 | 13781篇 |
2013年 | 18991篇 |
2012年 | 21954篇 |
2011年 | 22393篇 |
2010年 | 15045篇 |
2009年 | 13798篇 |
2008年 | 19847篇 |
2007年 | 20587篇 |
2006年 | 19298篇 |
2005年 | 18766篇 |
2004年 | 18626篇 |
2003年 | 17916篇 |
2002年 | 17261篇 |
2001年 | 27409篇 |
2000年 | 27479篇 |
1999年 | 22101篇 |
1998年 | 8305篇 |
1997年 | 8461篇 |
1996年 | 8089篇 |
1995年 | 8040篇 |
1994年 | 7710篇 |
1993年 | 7728篇 |
1992年 | 19046篇 |
1991年 | 18799篇 |
1990年 | 18471篇 |
1989年 | 17884篇 |
1988年 | 16748篇 |
1987年 | 16155篇 |
1986年 | 15190篇 |
1985年 | 15186篇 |
1984年 | 12603篇 |
1983年 | 11197篇 |
1982年 | 8665篇 |
1981年 | 8006篇 |
1980年 | 7423篇 |
1979年 | 12421篇 |
1978年 | 9928篇 |
1977年 | 9162篇 |
1976年 | 8618篇 |
1975年 | 9741篇 |
1974年 | 10655篇 |
1973年 | 10378篇 |
1972年 | 9432篇 |
1971年 | 8707篇 |
1970年 | 7478篇 |
1969年 | 7437篇 |
1968年 | 6702篇 |
1967年 | 5948篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Michael P. Gustafson Yi Lin Mary L. Maas Virginia P. Van Keulen Patrick B. Johnston Tobias Peikert Dennis A. Gastineau Allan B. Dietz 《PloS one》2015,10(3)
The development of flow cytometric biomarkers in human studies and clinical trials has been slowed by inconsistent sample processing, use of cell surface markers, and reporting of immunophenotypes. Additionally, the function(s) of distinct cell types as biomarkers cannot be accurately defined without the proper identification of homogeneous populations. As such, we developed a method for the identification and analysis of human leukocyte populations by the use of eight 10-color flow cytometric protocols in combination with novel software analyses. This method utilizes un-manipulated biological sample preparation that allows for the direct quantitation of leukocytes and non-overlapping immunophenotypes. We specifically designed myeloid protocols that enable us to define distinct phenotypes that include mature monocytes, granulocytes, circulating dendritic cells, immature myeloid cells, and myeloid derived suppressor cells (MDSCs). We also identified CD123 as an additional distinguishing marker for the phenotypic characterization of immature LIN-CD33+HLA-DR- MDSCs. Our approach permits the comprehensive analysis of all peripheral blood leukocytes and yields data that is highly amenable for standardization across inter-laboratory comparisons for human studies. 相似文献
4.
While supertrees have been built for many vertebrate groups (notably birds, mammals and dinosaurs), invertebrates have attracted relatively little attention. The paucity of supertrees of arthropods is particularly surprising given their economic and ecological importance, as well as their overwhelming contribution to biodiversity. The absence of comprehensive archives of machine-readable source trees, coupled with the need for software implementing repeatable protocols for managing them, has undoubtedly impeded progress. Here we present a supertree of Achelata (spiny, slipper and coral lobsters) as a proof of concept, constructed using new supertree specific software (the Supertree Toolkit; STK) and following a published protocol. We also introduce a new resource for archiving and managing published source trees. Our supertree of Achelata is synthesised from morphological and molecular source trees, and represents the most complete species-level tree of the group to date. Our findings are consistent with recent taxonomic treatments, confirming the validity of just two families: Palinuridae and Scyllaridae; Synaxidae were resolved within Palinuridae. Monophyletic Silentes and Stridentes lineages are recovered within Palinuridae, and all sub-families within Scyllaridae are found to be monophyletic with the exception of Ibacinae. We demonstrate the feasibility of building larger supertrees of arthropods, with the ultimate objective of building a complete species-level phylogeny for the entire phylum using a divide and conquer strategy. 相似文献
5.
Tom P. Moorhouse Cecilia A. L. Dahlsj? Sandra E. Baker Neil C. D'Cruze David W. Macdonald 《PloS one》2015,10(10)
Tourism accounts for 9% of global GDP and comprises 1.1 billion tourist arrivals per annum. Visits to wildlife tourist attractions (WTAs) may account for 20–40% of global tourism, but no studies have audited the diversity of WTAs and their impacts on the conservation status and welfare of subject animals. We scored these impacts for 24 types of WTA, visited by 3.6–6 million tourists per year, and compared our scores to tourists’ feedback on TripAdvisor. Six WTA types (impacting 1,500–13,000 individual animals) had net positive conservation/welfare impacts, but 14 (120,000–340,000 individuals) had negative conservation impacts and 18 (230,000–550,000 individuals) had negative welfare impacts. Despite these figures only 7.8% of all tourist feedback on these WTAs was negative due to conservation/welfare concerns. We demonstrate that WTAs have substantial negative effects that are unrecognised by the majority of tourists, suggesting an urgent need for tourist education and regulation of WTAs worldwide. 相似文献
6.
7.
8.
9.
10.