全文获取类型
收费全文 | 1045篇 |
免费 | 134篇 |
出版年
2021年 | 13篇 |
2020年 | 8篇 |
2018年 | 7篇 |
2016年 | 13篇 |
2015年 | 18篇 |
2014年 | 36篇 |
2013年 | 35篇 |
2012年 | 58篇 |
2011年 | 47篇 |
2010年 | 38篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 25篇 |
2006年 | 33篇 |
2005年 | 41篇 |
2004年 | 32篇 |
2003年 | 27篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 11篇 |
1993年 | 17篇 |
1992年 | 26篇 |
1991年 | 24篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 15篇 |
1973年 | 11篇 |
1972年 | 13篇 |
1971年 | 7篇 |
1970年 | 8篇 |
1969年 | 11篇 |
1888年 | 7篇 |
排序方式: 共有1179条查询结果,搜索用时 270 毫秒
71.
Hutchinson TM Bakulin AV Rakhmanov AS Martin RB Steele CR Arnaud SB 《Journal of medical primatology》2001,30(6):313-321
To determine the effects of the relative inactivity and unloading on the strength of the tibias of monkeys, Macaca mulatta, we used a non-invasive test to measure bending stiffness, or EI (Nm2), a mechanical property. The technique was validated by comparisons of in vivo measurements with standard measures of EI in the same bones post-mortem (r2 = 0.95, P < 0.0001). Inter-test precision was 4.28+/-1.4%. Normative data in 24 monkeys, 3.0+/-0.7 years and 3.6+/-0.6 kg, revealed EI to be 16% higher in the right than left tibia (4.4+/-1.6 vs. 3.7+/-1.6 Nm2, P < 0.05). Five monkeys, restrained in chairs for 14 days, showed decreases in EI. There were no changes in EI in two chaired monkeys that lost weight during a 2-week space flight. The factors that account for both the decreases in bone mechanical properties after chair restraint at 1 g and lack of change after microgravity remain to be identified. Metabolic factors associated with body weight changes are suggested by our results. 相似文献
72.
Nair SV Burandt M Hutchinson A Raison RL Raftos DA 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2001,129(1):11-24
Previous studies have identified proteins from tunicates (invertebrate members of the Phylum Chordata) that have physicochemical and functional properties similar to those of the inflammatory cytokine, interleukin 1 (IL-1). Here we characterize one of those proteins from the tunicate, Styela plicata, that can stimulate tunicate and mammalian cell proliferation, activate phagocytosis, increase interleukin 2 (IL-2) secretion by mammalian peripheral blood mononuclear cells and enhance IL-2 receptor (IL-2R) expression by mammalian EL-4.IL-2 cells. Partial amino acid sequence data showed that the S. plicata protein resembles three C-type lectins (TC14, TC14-1 and TC14-2) from a closely related tunicate species, Polyandrocarpa misakiensis. Its similarity to carbohydrate recognition domains (CRDs) from P. misakiensis lectins suggests that the S. plicata protein modulates the activities of mammalian immunocompetent cells by interacting with carbohydrate moieties of glycosylated cell surface receptors. 相似文献
73.
In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds. 相似文献
74.
Brashear KM Hunt CA Kucer BT Duggan ME Hartman GD Rodan GA Rodan SB Leu CT Prueksaritanont T Fernandez-Metzler C Barrish A Homnick CF Hutchinson JH Coleman PJ 《Bioorganic & medicinal chemistry letters》2002,12(23):3483-3486
A series of novel, highly potent alpha(v)beta(3) receptor antagonists with favorable pharmacokinetic profiles has been identified. In this series of antagonists, 2-aryl beta-amino acids function as potent aspartic acid replacements. 相似文献
75.
Coleman PJ Askew BC Hutchinson JH Whitman DB Perkins JJ Hartman GD Rodan GA Leu CT Prueksaritanont T Fernandez-Metzler C Merkle KM Lynch R Lynch JJ Rodan SB Duggan ME 《Bioorganic & medicinal chemistry letters》2002,12(17):2463-2465
Potent non-peptidic alpha(v)beta(3) antagonists have been prepared where deletion of an amide bond from an earlier series of linear RGD-mimetics provides a novel series of chain-shortened alpha(v)beta(3) antagonists with significantly improved oral pharmacokinetics. These chain-shortened alpha(v)beta(3) antagonists represent structurally novel integrin inhibitors. 相似文献
76.
77.
Alexander RP Warrellow GJ Eaton MA Boyd EC Head JC Porter JR Brown JA Reuberson JT Hutchinson B Turner P Boyce B Barnes D Mason B Cannell A Taylor RJ Zomaya A Millican A Leonard J Morphy R Wales M Perry M Allen RA Gozzard N Hughes B Higgs G 《Bioorganic & medicinal chemistry letters》2002,12(11):1451-1456
The discovery, synthesis and biological activity of a series of triarylethane phosphodiesterase 4 inhibitors is described. Structure-activity relationship studies are presented for CDP840 (29), a potent, chiral, selective inhibitor of PDE 4 (IC(50) 4nM). CDP840 is non-emetic in the ferret at 30mgkg(-1) (po), active in models of inflammation and reverses ozone-induced bronchial hyperreactivity in the guinea pig. 相似文献
78.
Hutchinson TP Gudlaugsdottir S 《Analytical and quantitative cytology and histology / the International Academy of Cytology [and] American Society of Cytology》2002,24(2):121-124
OBJECTIVE: To construct a statistical model for the agreements and disagreements between two observers on darkness of staining. STUDY DESIGN: Data from an earlier observer-agreement study by van Diest et al were reanalyzed. RESULTS: A model in which the random variation in error is permitted to depend upon the true darkness of staining wasfound tofit the data much better than does one in which the random variation is constant. CONCLUSION: For the dataset analyzed, error tends to be greater (that is, correlation between observers tends to be less) when staining is darker. 相似文献
79.
Aojula HS Offerman S Aojula RR Hutchinson AP Nicklin S Clarke DJ 《Biochimica et biophysica acta》2002,1564(1):73-81
Potent cytolytic peptides with specific tethering and cloaking sites have been synthesised and used to release payload from liposomes in a quantitative manner. A functionally located cloaking site has been modified specifically by simple conjugation without adversely affecting the cytolytic properties of the peptide. The cytolytic activity of modified peptides was then efficiently (>98%) cloaked and uncloaked by ligand-protein or hapten-antibody interactions. The principle of a dual response peptide has been demonstrated using an avidin-cloaked pH-sensitive peptide. Biospecific cloaking/uncloaking provided a new sensitive (approximately 12 pmol) homogeneous diagnostic and also appears potentially suited to bioresponsively targeted release of antimicrobial, anticancer and other drugs now delivered using liposomes. 相似文献
80.
Approaches to stabilization of inter-domain recombination in polyketide synthase gene expression plasmids 总被引:1,自引:0,他引:1
Hu Z Desai RP Volchegursky Y Leaf T Woo E Licari P Santi DV Hutchinson CR McDaniel R 《Journal of industrial microbiology & biotechnology》2003,30(3):161-167
Regions of extremely high sequence identity are recurrent in modular polyketide synthase (PKS) genes. Such sequences are
potentially detrimental to the stability of PKS expression plasmids used in the combinatorial biosynthesis of polyketide metabolites.
We present two different solutions for circumventing intra-plasmid recombination within the megalomicin PKS genes in Streptomyces coelicolor. In one example, a synthetic gene was used in which the codon usage was reengineered without affecting the primary amino
acid sequence. The other approach utilized a heterologous subunit complementation strategy to replace one of the problematic
regions. Both methods resulted in PKS complexes capable of 6-deoxyerythronolide B analogue biosynthesis in S. coelicolor CH999, permitting reproducible scale-up to at least 5-l stirred-tank fermentation and a comparison of diketide precursor
incorporation efficiencies between the erythromycin and megalomicin PKSs.
Electronic Publication 相似文献