全文获取类型
收费全文 | 562篇 |
免费 | 113篇 |
专业分类
675篇 |
出版年
2022年 | 5篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 20篇 |
2014年 | 31篇 |
2013年 | 17篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 21篇 |
2007年 | 22篇 |
2006年 | 19篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 19篇 |
2001年 | 20篇 |
2000年 | 25篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1961年 | 4篇 |
排序方式: 共有675条查询结果,搜索用时 15 毫秒
121.
Prehensile tails appear to have evolved at least twice in platyrrhine evolution. In the atelines, the tail is relatively long and possesses a bare area on the distal part of its ventral surface that is covered with der-matoglyphs and richly innervated with Meissner's corpuscles. In contrast, the prehensile tail of Cebus is relatively short, fully haired, and lacks specialized tactile receptors. Little is currently known regarding tail function in capuchins, and whether their prehensile tail serves a greater role in feeding or traveling. In this paper we examine patterns of positional behavior, substrate preference, and tail use in wild white-faced capuchins (Cebus capucinus) inhabiting a wet tropical forest in northeastern Costa Rica. Observational data were collected over the course of 3 months on adult capuchins using an instantaneous focal animal time sampling technique. Differences in the frequency and context of tail use, and the estimated amount of weight support provided by the tail relative to other appendages during feeding/foraging and traveling were used as measures of the ecological role of this specialized organ in capuchin positional behavior. During travel, quadrupedal walking, leaping, and climbing dominated the capuchin positional repertoire. The capuchin tail provided support in only 13.3% of travel and was principally employed during below branch locomotor activities. In contrast, tail-assisted postures accounted for 40.6% of all feeding and foraging records and occurred primarily in two contexts. The tail was used to suspend the individual below a branch while feeding, as well as to provide leverage and weight support in above-branch postures associated with the extraction of prey from difficult to search substrates. A comparison of tail use in Cebus, with published data on the atelines indicates that both taxa possess a grasping tail that is capable of supporting the animal's full body weight. In capuchins and howling monkeys, the tail appears to be used more frequently and serves a greater weight-bearing role during feeding than during traveling. In Ateles, and possibly Brachyteles, and Lagothrix, however, the prehensile tail serves a dual role in both feeding and forelimb suspensory locomotion. Additional relationships between white-faced capuchin feeding, positional behavior, extractive foraging techniques, and prehensile tail use are discussed. 相似文献
122.
Integrating feeding behavior,ecological data,and DNA barcoding to identify developmental differences in invertebrate foraging strategies in wild white‐faced capuchins (Cebus capucinus)
下载免费PDF全文
![点击此处可从《American journal of physical anthropology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
123.
Fallback foods have been defined as resources for which a species has evolved specific masticatory and digestive adaptations, and are consumed principally when preferred foods are scarce. In the present field investigation, we examine fungi, fruit, and exudate consumption in one group of Callimico goeldii in order to determine the importance of exudates as a fallback food for this species. Based on a total of 1,198 hr of quantitative behavioral data collected between mid-November 2002-August 2003, we found that pod exudates of Parkia velutina accounted for 19% of callimico feeding time in the dry season. This resource was not consumed in the wet season when fruits and fungi were the most common items in the diet. In the dry season of 2005 (July), the same callimico study group did not consume Parkia pod exudates. Instead, the group ate exudates obtained from holes gouged in tree trunks by pygmy marmosets and exudates resulting from natural weathering and insect damage on trunks, roots, and lianas. Pod exudates are reported to contain greater amounts of readily available energy than do trunk and root exudates, and were consumed throughout all periods of the day, particularly in the late afternoon. Trunk and root exudates were consumed principally in the morning. We propose that digestive adaptations of the hindgut, which enable callimicos to exploit fungi (a resource high in structural carbohydrates) year-round, predispose them to efficiently exploit and process exudates as fallback foods when other resources, such as ripe fruits, are scarce. 相似文献
124.
Jennifer S Michaelson Stephen J Demarest Brian Miller Aldo Amatucci William B Snyder Xiufeng Wu Flora Huang Samantha Phan Sharon Gao Adam Doern Graham K Farrington Alexey Lugovskoy Ingrid Joseph Veronique Bailly Xin Wang Ellen Garber Jeff Browning Scott M Glaser 《MABS-AUSTIN》2009,1(2):128-141
Bispecific antibodies (BsAbs) represent an emerging class of biologics that achieve dual targeting with a single agent. Recombinant DNA technologies have facilitated a variety of creative bispecific designs with many promising therapeutic applications; however, practical methods for producing high quality BsAbs that have good product stability, long serum half-life, straightforward purification, and scalable production have largely been limiting. Here we describe a protein-engineering approach for producing stable, scalable tetravalent IgG-like BsAbs. The stability-engineered IgG-like BsAb was envisioned to target and crosslink two TNF family member receptors, TRAIL-R2 (TNF-Related Apoptosis Inducing Ligand Receptor-2) and LTβR (Lymphotoxin-beta Receptor), expressed on the surface of epithelial tumor cells with the goal of triggering an enhanced anti-tumor effect. Our IgG-like BsAbs consists of a stability-engineered anti-LTβR single chain Fv (scFv) genetically fused to either the N- or C-terminus of the heavy chain of a full-length anti-TRAIL-R2 IgG1 monoclonal antibody. Both N- or C-terminal BsAbs were active in inhibiting tumor cell growth in vitro, and with some cell lines demonstrated enhanced activity relative to the combination of parental Abs. Pharmacokinetic studies in mice revealed long serum half-lives for the BsAbs. In murine tumor xenograft models, therapeutic treatment with the BsAbs resulted in reduction in tumor volume either comparable to or greater than the combination of parental antibodies, indicating that simultaneously targeting and cross-linking receptor pairs is an effective strategy for treating tumor cells. These studies support that stability-engineering is an enabling step for producing scalable IgG-like BsAbs with properties desirable for biopharmaceutical development.Key words: bispecific antibodies, single-chain Fv, immunoglobulins, antibody therapeutics, protein stability, pharmacokinetics, protein engineering, tumor inhibition, cancer treatment 相似文献
125.
126.
Kathryn B. Garber 《American journal of human genetics》2009,84(3):305-306
127.
Manuel Garber Michael C Zody Harindra M Arachchi Aaron Berlin Sante Gnerre Lisa M Green Niall Lennon Chad Nusbaum 《Genome biology》2009,10(6):R60-6
The most recent release of the finished human genome contains 260 euchromatic gaps (excluding chromosome Y). Recent work has
helped explain a large number of these unresolved regions as 'structural' in nature. Another class of gaps is likely to be
refractory to clone-based approaches, and cannot be approached in ways previously described. We present an approach for closing
these gaps using 454 sequencing. As a proof of principle, we closed all three remaining non-structural gaps in chromosome
15. 相似文献
128.
129.
130.