全文获取类型
收费全文 | 4101篇 |
免费 | 384篇 |
国内免费 | 1篇 |
专业分类
4486篇 |
出版年
2022年 | 28篇 |
2021年 | 43篇 |
2020年 | 43篇 |
2019年 | 34篇 |
2018年 | 41篇 |
2017年 | 47篇 |
2016年 | 77篇 |
2015年 | 116篇 |
2014年 | 145篇 |
2013年 | 187篇 |
2012年 | 273篇 |
2011年 | 248篇 |
2010年 | 169篇 |
2009年 | 143篇 |
2008年 | 218篇 |
2007年 | 300篇 |
2006年 | 217篇 |
2005年 | 242篇 |
2004年 | 236篇 |
2003年 | 194篇 |
2002年 | 214篇 |
2001年 | 53篇 |
2000年 | 39篇 |
1999年 | 57篇 |
1998年 | 67篇 |
1997年 | 43篇 |
1996年 | 39篇 |
1995年 | 41篇 |
1994年 | 50篇 |
1993年 | 37篇 |
1992年 | 44篇 |
1991年 | 29篇 |
1990年 | 46篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 36篇 |
1986年 | 26篇 |
1985年 | 44篇 |
1984年 | 34篇 |
1983年 | 49篇 |
1982年 | 42篇 |
1981年 | 40篇 |
1980年 | 42篇 |
1979年 | 38篇 |
1978年 | 33篇 |
1977年 | 30篇 |
1975年 | 21篇 |
1974年 | 29篇 |
1973年 | 28篇 |
1972年 | 29篇 |
排序方式: 共有4486条查询结果,搜索用时 15 毫秒
71.
72.
73.
Carl D. Mitchell Vernon C. Bleich R. Terry Bowyer James R. Heffelfinger Kelley M. Stewart Paula A. White 《The Journal of wildlife management》2021,85(3):418-422
Reported effects of trophy harvest often are controversial. The subject is nuanced and many studies lack details necessary to place their results in context. Consequently, many studies are misunderstood or their conclusions misapplied. We propose that all dialogues about trophy hunting include a definition of how they use the term trophy, details of variables measured and why they were selected, and explanations of temporal and spatial scales employed. Only with these details can potential effects of trophy hunting be understood in context and used for management and policy decisions. © 2021 The Wildlife Society. 相似文献
74.
Lindsey Seldin Nicholas D. Poulson Henry P. Foote Terry Lechler 《Molecular biology of the cell》2013,24(23):3651-3662
The epidermis is a multilayered epithelium that requires asymmetric divisions for stratification. A conserved cortical protein complex, including LGN, nuclear mitotic apparatus (NuMA), and dynein/dynactin, plays a key role in establishing proper spindle orientation during asymmetric divisions. The requirements for the cortical recruitment of these proteins, however, remain unclear. In this work, we show that NuMA is required to recruit dynactin to the cell cortex of keratinocytes. NuMA''s cortical recruitment requires LGN; however, LGN interactions are not sufficient for this localization. Using fluorescence recovery after photobleaching, we find that the 4.1-binding domain of NuMA is important for stabilizing its interaction with the cell cortex. This is functionally important, as loss of 4.1/NuMA interaction results in spindle orientation defects, using two distinct assays. Furthermore, we observe an increase in cortical NuMA localization as cells enter anaphase. Inhibition of Cdk1 or mutation of a single residue in NuMA mimics this effect. NuMA''s anaphase localization is independent of LGN and 4.1 interactions, revealing two distinct mechanisms responsible for NuMA cortical recruitment at different stages of mitosis. This work highlights the complexity of NuMA localization and reveals the importance of NuMA cortical stability for productive force generation during spindle orientation. 相似文献
75.
Clayton L. Camic Terry J. Housh Jorge M. Zuniga C. Russell Hendrix Haley C. Bergstrom Daniel A. Traylor Richard J. Schmidt Glen O. Johnson 《Journal of electromyography and kinesiology》2013,23(2):342-348
The purpose of the present study was to examine the patterns of responses for torque, electromyographic (EMG) amplitude, EMG mean power frequency (MPF), mechanomyographic (MMG) amplitude, and MMG MPF across 30 repeated maximal isometric (ISO) and concentric (CON) muscle actions of the leg extensors. Twelve female subjects (21.1 ± 1.4 yrs; 63.3 ± 7.4 kg) performed ISO and CON fatigue protocols with EMG and MMG signals recorded from the vastus lateralis. The relationships for torque, EMG amplitude, EMG MPF, MMG amplitude, and MMG MPF versus repetition number were examined using polynomial regression. The results indicated there were decreases (p < 0.05) across the ISO muscle actions for torque (r2 = 0.95), EMG amplitude (R2 = 0.44), EMG MPF (r2 = 0.62), and MMG MPF (r2 = 0.48), but no change in MMG amplitude (r2 = 0.07). In addition, there were decreases across the CON muscle actions for torque (R2 = 0.97), EMG amplitude (R2 = 0.46), EMG MPF (R2 = 0.86), MMG amplitude (R2 = 0.44), and MMG MPF (R2 = 0.80). Thus, the current findings suggested that the mechanisms of fatigue and motor control strategies used to modulate torque production were similar between maximal ISO and CON muscle actions. 相似文献
76.
Angela S. Kelling Stephanie M. Allard Nicholas J. Kelling Estelle A. Sandhaus Terry L. Maple 《Journal of applied animal welfare science : JAAWS》2013,16(4):313-328
Felids in captivity are often inactive and elusive in zoos, leading to a frustrating visitor experience. Eight roars were recorded from an adult male lion and played back over speakers as auditory enrichment to benefit the lions while simultaneously enhancing the zoo visitor experience. In addition, ungulates in an adjacent exhibit were observed to ensure that the novel location and increased frequency of roars did not lead to a stress or fear response. The male lion in this study roared more in the playback phase than in the baseline phases while not increasing any behaviors that would indicate compromised welfare. In addition, zoo visitors remained at the lion exhibit longer during playback. The nearby ungulates never exhibited any reactions stronger than orienting to playbacks, identical to their reactions to live roars. Therefore, naturalistic playbacks of lion roars are a potential form of auditory enrichment that leads to more instances of live lion roars and enhances the visitor experience without increasing the stress levels of nearby ungulates or the lion themselves, who might interpret the roar as that of an intruder. 相似文献
77.
Terry Kenakin 《Journal of receptor and signal transduction research》2013,33(3-4):132-139
The key to detecting and classifying drug effect at seven transmembrane (7TM) receptors is the pharmacological assay. Drug discovery had been rooted in testing of molecules on intact animal tissue until technology provided high-throughput binding assays for screening. While this allowed for the testing of large numbers of molecules, it also limited detection to molecules that interfere with the interaction of the receptor with a defined probe (i.e., radioligand). The ability to monitor functional changes in cells (recombinant or natural) provided a huge leap forward. Earlier functional assays were tied to specific signaling pathways (i.e., cyclic AMP and calcium) but now label-free assays in live cells provide the opportunity to detect more ligands and more fully characterize their efficacy. These ideas will be discussed in terms of harnessing the phenomenon of “functional selectivity” for therapeutic advantage. 相似文献
78.
Lindsay?L?FarrellEmail author Terry?Burke Jon?Slate Susan?B?McRae David?B?Lank 《BMC genetics》2013,14(1):109
Background
Ruffs (Aves: Philomachus pugnax) possess a genetic polymorphism for male mating behaviour resulting in three permanent alternative male reproductive morphs: (i) territorial ‘Independents’, (ii) non-territorial ‘Satellites’, and (iii) female-mimicking ‘Faeders’. Development into independent or satellite morphs has previously been shown to be due to a single-locus, two-allele autosomal Mendelian mode of inheritance at the Satellite locus. Here, we use linkage analysis to map the chromosomal location of the Faeder locus, which controls development into the Faeder morph, and draw further conclusions about candidate genes, assuming shared synteny with other birds.Results
Segregation data on the Faeder locus were obtained from captive-bred pedigrees comprising 64 multi-generation families (N?=?381). There was no evidence that the Faeder locus was linked to the Satellite locus, but it was linked with microsatellite marker Ppu020. Comparative mapping of ruff microsatellite markers against the chicken (Gallus gallus) and zebra finch (Taeniopygia guttata) genomes places the Ppu020 and Faeder loci on a region of chromosome 11 that includes the Melanocortin-1 receptor (MC1R) gene, which regulates colour polymorphisms in numerous birds and other vertebrates. Melanin-based colouration varies with life-history strategies in ruffs and other species, thus the MC1R gene is a strong candidate to play a role in alternative male morph determination.Conclusion
Two unlinked loci appear to control behavioural development in ruffs. The Faeder locus is linked to Ppu020, which, assuming synteny, is located on avian chromosome 11. MC1R is a candidate gene involved in alternative male morph determination in ruffs.79.
80.
Meiotic recombination is sexually dimorphic in most mammalian species, including humans, but the basis for the male:female differences remains unclear. In the present study, we used cytological methodology to directly compare recombination levels between human males and females, and to examine possible sex-specific differences in upstream events of double-strand break (DSB) formation and synaptic initiation. Specifically, we utilized the DNA mismatch repair protein MLH1 as a marker of recombination events, the RecA homologue RAD51 as a surrogate for DSBs, and the synaptonemal complex proteins SYCP3 and/or SYCP1 to examine synapsis between homologs. Consistent with linkage studies, genome-wide recombination levels were higher in females than in males, and the placement of exchanges varied between the sexes. Subsequent analyses of DSBs and synaptic initiation sites indicated similar male:female differences, providing strong evidence that sex-specific differences in recombination rates are established at or before the formation of meiotic DSBs. We then asked whether these differences might be linked to variation in the organization of the meiotic axis and/or axis-associated DNA and, indeed, we observed striking male:female differences in synaptonemal complex (SC) length and DNA loop size. Taken together, our observations suggest that sex specific differences in recombination in humans may derive from chromatin differences established prior to the onset of the recombination pathway. 相似文献