全文获取类型
收费全文 | 7876篇 |
免费 | 824篇 |
国内免费 | 3篇 |
专业分类
8703篇 |
出版年
2024年 | 4篇 |
2023年 | 55篇 |
2022年 | 142篇 |
2021年 | 271篇 |
2020年 | 134篇 |
2019年 | 177篇 |
2018年 | 206篇 |
2017年 | 193篇 |
2016年 | 338篇 |
2015年 | 525篇 |
2014年 | 523篇 |
2013年 | 538篇 |
2012年 | 696篇 |
2011年 | 716篇 |
2010年 | 460篇 |
2009年 | 359篇 |
2008年 | 502篇 |
2007年 | 505篇 |
2006年 | 384篇 |
2005年 | 375篇 |
2004年 | 387篇 |
2003年 | 328篇 |
2002年 | 300篇 |
2001年 | 59篇 |
2000年 | 41篇 |
1999年 | 51篇 |
1998年 | 72篇 |
1997年 | 31篇 |
1996年 | 44篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 20篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 22篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1968年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有8703条查询结果,搜索用时 0 毫秒
181.
Ben Mersey Rebecca S. Jabbour Kyle Brudvik Alban Defleur 《American journal of physical anthropology》2013,152(4):516-529
The hand and foot remains from Moula‐Guercy cave (Ardèche, France) comprise 24 specimens of Eemian age (ca. 120 ka). The specimens include primarily complete elements, which are rare among the Moula‐Guercy postcrania. The hand remains have several characteristic Neanderthal traits including a laterally facing (parasagittally oriented) second metacarpal‐capitate articulation, a short styloid process, a wide proximal articular surface on the third metacarpal, and absolutely expanded apical tuberosities on the distal hand phalanges relative to modern humans. The foot remains include several incomplete elements along with an antimeric pair of naviculars, a medial cuneiform and cuboid, and a single complete element from each of the distal segments (one each: metatarsal, proximal foot phalanx, intermediate foot phalanx, distal foot phalanx). Consistent among the specimens are relatively wide diaphyses for length in the metatarsals and phalanges and large and prominent muscle attachments, both consistent with previously published Neanderthal morphology. The hand and foot collection from Moula‐Guercy is an important dataset for future studies of Neanderthal functional morphology, dexterity, and behavior as it represents a previously undersampled time period for European Neanderthals. Am J Phys Anthropol 152:516–529, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
182.
Antimicrobial peptides are an important component of innate immunity and have generated considerable interest as a new potential class of natural antibiotics. The biological activity of antimicrobial peptides is strongly influenced by peptide–membrane interactions. Human Neutrophil Peptide 1 (HNP-1) is a 30 aminoacid peptide, belonging to the class of α-defensins. Many biophysical studies have been performed on this peptide to define its mechanism of action. Combining spectroscopic and thermodynamic analysis, insights on the interaction of the α-defensin with POPE:POPG:CL negative charged bilayers are given. The binding states of the peptide below and above the threshold concentration have been analyzed showing that the interaction with lipid bilayers is dependent by peptide concentration. These novel results that indicate how affinity and biological activities of natural antibiotics are depending by their concentration, might open new way of investigation of the antimicrobial mode of action. 相似文献
183.
Kerem Teralı Rebecca L. Beavil Richard W. Pickersgill Mark van der Giezen 《Biochemical and biophysical research communications》2013
Small inorganic assemblies of alternating ferrous/ferric iron and sulphide ions, so-called iron–sulphur (Fe–S) clusters, are possibly nature’s most ancient prosthetic groups. One of the early actors in Fe–S cluster biosynthesis is a protein complex composed of a cysteine desulphurase, Nfs1, and its functional binding partner, Isd11. Although the essential function of Nfs1·Isd11 in the liberation of elemental sulphur from free cysteine is well established, little is known about its structure. Here, we provide evidence that shows Isd11 has a profound effect on the oligomeric state of Nfs1. 相似文献
184.
Martha M. Muñoz Nicholas G. Crawford Thomas J. McGreevy Jr Nicholas J. Messana Rebecca D. Tarvin Liam J. Revell Rosanne M. Zandvliet Juanita M. Hopwood Elbert Mock André L. Schneider Christopher J. Schneider 《Molecular ecology》2013,22(10):2668-2682
Adaptive divergence in coloration is expected to produce reproductive isolation in species that use colourful signals in mate choice and species recognition. Indeed, many adaptive radiations are characterized by differentiation in colourful signals, suggesting that divergent selection acting on coloration may be an important component of speciation. Populations in the Anolis marmoratus species complex from the Caribbean island of Guadeloupe display striking divergence in the colour and pattern of adult males that occurs over small geographic distances, suggesting strong divergent selection. Here we test the hypothesis that divergence in coloration results in reduced gene flow among populations. We quantify variation in adult male coloration across a habitat gradient between mesic and xeric habitats, use a multilocus coalescent approach to infer historical demographic parameters of divergence, and examine gene flow and population structure using microsatellite variation. We find that colour variation evolved without geographic isolation and in the face of gene flow, consistent with strong divergent selection and that both ecological and sexual selection are implicated. However, we find no significant differentiation at microsatellite loci across populations, suggesting little reproductive isolation and high levels of contemporary gene exchange. Strong divergent selection on loci affecting coloration probably maintains clinal phenotypic variation despite high gene flow at neutral loci, supporting the notion of a porous genome in which adaptive portions of the genome remain fixed whereas neutral portions are homogenized by gene flow and recombination. We discuss the impact of these findings for studies of colour evolution and ecological speciation. 相似文献
185.
Noboru Tomiya Juliette G. Jardim Jennifer Hou Rebecca Pastrana-Mena Rhoel R. Dinglasan Yuan C. Lee 《Bioorganic & medicinal chemistry》2013,21(17):5275-5281
We have synthesized poly-γ-glutamic acid (PGA) modified with a synthetic trivalent glyco-ligand (TriGalNAc) for the hepatocyte asialoglycoprotein receptor (ASGP-R). We investigated in vivo distribution of unmodified PGA and TriGalNAc-modified PGA (TriGalNAc-PGA) in mice after intravenous injection. Most of unmodified PGA administered was transported to the bladder over 20–80 min, suggesting a rapid excretion of unmodified PGA into urine. In contrast, TriGalNAc-PGA was found exclusively in the liver over the same period of time. We further synthesized TriGalNAc-PGA–primaquine conjugate (TriGalNAc-PGA–PQ), and investigated binding, uptake, and catabolism of the conjugate by rat hepatocytes. Our studies indicated that approximately 250 ng per million cells of the conjugate bound to one million rat hepatocytes at 0 °C, and approximately 2 μg per million cells of the conjugate was taken up over 7 h incubation at 37 °C. Furthermore, our results suggested that TriGalNAc-PGA–PQ was almost completely degraded over 24 h, and small degradation products were secreted into cell culture medium.The results described in this report suggest that the TriGalNAc ligand can serve as an excellent targeting device for delivery of PGA-conjugates to the liver hepatocytes, and rat hepatocytes possess sufficient capacity to digest PGA even modified with other substituents. 相似文献
186.
187.
Daniel J. Peart Richard J. Kirk Leigh A. Madden Jason C. Siegler Rebecca V. Vince 《Amino acids》2013,44(3):903-910
The aim of this study was to observe the intracellular heat shock protein 72 (HSP72) and heme oxygenase-1 (HSP32) response to prolonged interval cycling following the ingestion of carbohydrates (CHO) and sodium bicarbonate (NaHCO3). Six recreationally active males (mean ± SD; age 23.2 ± 2.9 years, height 179.5 ± 5.5 cm, body mass 76.5 ± 6.8 kg, and peak power output 315 ± 36 W) volunteered to complete a 90 min interval cycling exercise on four occasions. The trials were completed in a random and blinded manner following ingestion of either: placebo and an artificial sweetener (P–P), NaHCO3 and sweetener (B–P), placebo and CHO (P–CHO), and NaHCO3 and CHO (B–CHO). Both HSP72 and HSP32 were significantly increased in monocytes and lymphocytes from 45 min post-exercise (p ≤ 0.039), with strong relationships between both cell types (HSP72, r = 0.83; HSP32, r = 0.89). Exogenous CHO had no influence on either HSP72 or HSP32, but the ingestion of NaHCO3 significantly attenuated HSP32 in monocytes and lymphocytes (p ≤ 0.042). In conclusion, the intracellular stress protein response to 90 min interval exercise is closely related in monocytes and lymphocytes, and HSP32 appears to be attenuated with a pre-exercise alkalosis. 相似文献
188.
189.
Rebecca C. Jones Dorothy A. Steane Martyn Lavery René E. Vaillancourt Brad M. Potts 《Ecology and evolution》2013,3(1):1-17
Forest trees frequently form species complexes, complicating taxonomic classification and gene pool management. This is certainly the case in Eucalyptus, and well exemplified by the Eucalyptus globulus complex. This ecologically and economically significant complex comprises four taxa (sspp. bicostata, globulus, maidenii, pseudoglobulus) that are geographically and morphologically distinct, but linked by extensive “intergrade” populations. To resolve their genetic affinities, nine microsatellites were used to genotype 1200 trees from throughout the natural range of the complex in Australia, representing 33 morphological core and intergrade populations. There was significant spatial genetic structure (FST = 0.10), but variation was continuous. High genetic diversity in southern ssp. maidenii indicates that this region is the center of origin. Genetic diversity decreases and population differentiation increases with distance from this area, suggesting that drift is a major evolutionary process. Many of the intergrade populations, along with other populations morphologically classified as ssp. pseudoglobulus or ssp. globulus, belong to a “cryptic genetic entity” that is genetically and geographically intermediate between core ssp. bicostata, ssp. maidenii, and ssp. globulus. Geography, rather than morphology, therefore, is the best predictor of overall genetic affinities within the complex and should be used to classify germplasm into management units for conservation and breeding purposes. 相似文献
190.
Grace?S?Tan Rebecca?Lewandowski Michael?J?Mallory Randy?Strich Katrina?F?CooperEmail author 《Cell division》2013,8(1):9