全文获取类型
收费全文 | 898篇 |
免费 | 50篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 25篇 |
2015年 | 52篇 |
2014年 | 48篇 |
2013年 | 58篇 |
2012年 | 99篇 |
2011年 | 75篇 |
2010年 | 51篇 |
2009年 | 36篇 |
2008年 | 70篇 |
2007年 | 59篇 |
2006年 | 37篇 |
2005年 | 43篇 |
2004年 | 48篇 |
2003年 | 35篇 |
2002年 | 29篇 |
2001年 | 5篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有948条查询结果,搜索用时 15 毫秒
91.
Mark A. Arbing Samuel K. Handelman Alexandre P. Kuzin Grégory Verdon Chi Wang Min Su Francesca P. Rothenbacher Mariam Abashidze Mohan Liu Jennifer M. Hurley Rong Xiao Thomas Acton Masayori Inouye Gaetano T. Montelione Nancy A. Woychik John F. Hunt 《Structure (London, England : 1993)》2010,18(8):996-1010
92.
The present paper shows the results of chromosome banding and rDNA-FISH study performed on several specimens of different
populations of Patella caerulea, Patella
rustica and Patella
ulyssiponensis. The taxonomic attribution of specimens was ascertained by the molecular phylogenetic analysis of the mitochondrial 16S rRNA
gene. P. caerulea and P. rustica had 2n = 18 chromosomes with first seven of biarmed pairs and the remaining two uniarmed pairs. P. ulyssiponensis had 2n = 16 with all biarmed chromosomes. Ag-NOR loci were on the short arms of the first metacentric pair in the three studied
limpets, whereas they showed a different pattern of heterochromatin distribution and composition. A chromosome mosaicism was
observed in several P. caerulea specimens, which exhibited an unpaired metacentric element and loss of a telocentric pair. The obtained results suggest that
in the genus Patella specific diversification was accompanied by variations in heterochromatin distribution and composition and reduction of chromosome
number by Robertsonian centric fusion. 相似文献
93.
94.
de Amicis F Lanzino M Kisslinger A Calì G Chieffi P Andò S Mancini FP Tramontano D 《Journal of cellular physiology》2006,209(1):74-80
Although prostate carcinoma is an aggressive cancer preferentially metastasizing to the bones, many prostate tumors remain localized and confined to the prostate indefinitely. Prediction of the behavior of anatomically localized and moderately differentiated prostate tumors remains difficult because of lack of prognostic markers. Cell motility is an important step in the progression of epithelial tumor toward invasive metastatic carcinomas and changes in the expression and function of adhesion molecules contribute to the acquisition of a more malignant phenotype. Proline-rich tyrosine kinase 2 (Pyk2) is implicated in regulating the organization of actin cytoskeleton, a process critical for cell migration, mitosis, and tumor metastasis. In this report, we investigated whether Pyk2 played a role in the acquisition of an aggressive phenotype in prostate cell. Data reported here demonstrate that loss of Pyk2 kinase function results in induction of cell motility and migration in EPN cells, a line of non-transformed epithelial cells derived from human normal prostate tissue. Changes in motility and migration of prostate cells were associated with changes in the expression of several proteins involved in cell adhesion and reorganization of actin cytoskeleton. Ablation of Pyk2 kinase activity caused a dramatic decrease of the expression of E-cadherin and IRS1 and an increase of the expression of alpha5-integrin. In addition, a massive reorganization of actin cytoskeleton was observed. Our data indicate that Pyk2 plays a central role in the mechanism that regulate cell-cell and cell-substrate interaction and lack of its kinase activity induces prostate cells to acquire a malignant, migrating phenotype. 相似文献
95.
The Euglycemic Hyperinsulinemic Clamp (EHC) is the most widely used experimental procedure for the determination of insulin sensitivity. In the present study, 16 subjects with BMI between 18.5 and 63.6 kg/m2 have been studied with a long-duration (5 hours) EHC. In order to explain the oscillations of glycemia occurring in response to the hyperinsulinization and to the continuous glucose infusion at varying speeds, we first hypothesized a system of ordinary differential equations (ODEs), with limited success. We then extended the model and represented the experiment using a system of stochastic differential equations (SDEs). The latter allow for distinction between (i) random variation imputable to observation error and (ii) system noise (intrinsic variability of the metabolic system), due to a variety of influences which change over time. The stochastic model of the EHC was fitted to data and the system noise was estimated by means of a (simulated) maximum likelihood procedure, for a series of different hypothetical measurement error values. We showed that, for the whole range of reasonable measurement error values: (i) the system noise estimates are non-negligible; and (ii) these estimates are robust to changes in the likely value of the measurement error. Explicit expression of system noise is physiologically relevant in this case, since glucose uptake rate is known to be affected by a host of additive influences, usually neglected when modeling metabolism. While in some of the studied subjects system noise appeared to only marginally affect the dynamics, in others the system appeared to be driven more by the erratic oscillations in tissue glucose transport rather than by the overall glucose-insulin control system. It is possible that the quantitative relevance of the unexpressed effects (system noise) should be considered in other physiological situations, represented so far only with deterministic models.The work was supported by grants from the Danish Medical Research Council and the Lundbeck Foundation to S. Ditlevsen. 相似文献
96.
We have investigated the oxidative behavior of sterols such as cholesteryl acetate (1), 7-dehydrocholesteryl acetate (2), ergosteryl acetate (3), cholecalciferol acetate (Vitamin D(3) acetate) (4) and ergocalciferol acetate (Vitamin D(2) acetate) (5) with the oxidant system methyltrioxorhenium/H(2)O(2)/pyridine in order to check potential parameters controlling the selectivity. The reactions, performed in CH(2)Cl(2)/H(2)O at 25 degrees C, have shown good regio- and stereoselectivity. All oxidation products were isolated by high-performance liquid chromatography (HPLC) and characterized by MS(EI) or FAB, (1)H NMR, (13)C NMR, APT, COSY, HSQC, HMBC, ROESY and NOEDS measurements. Seven new oxygenated compounds were also obtained. Under the experimental conditions adopted in this work, only the diene steroids, i.e. 7-dehydrocholesteryl acetate and ergosteryl acetate, undergo hydrolytic oxirane ring opening, whereas Vitamin D(2) and D(3) acetates, containing the triene system and cholesteryl acetate yield only epoxides. The selectivity seems to be controlled by the nucleophilicity of double bonds and by stereoelectronic and steric effects. 相似文献
97.
98.
Snyder DA Aramini JM Yu B Huang YJ Xiao R Cort JR Shastry R Ma LC Liu J Rost B Acton TB Kennedy MA Montelione GT 《Proteins》2012,80(7):1901-1906
The ribosome consists of small and large subunits each composed of dozens of proteins and RNA molecules. However, the functions of many of the individual protomers within the ribosome are still unknown. In this article, we describe the solution NMR structure of the ribosomal protein RP-L35Ae from the archaeon Pyrococcus furiosus. RP-L35Ae is buried within the large subunit of the ribosome and belongs to Pfam protein domain family PF01247, which is highly conserved in eukaryotes, present in a few archaeal genomes, but absent in bacteria. The protein adopts a six-stranded anti-parallel β-barrel analogous to the "tRNA binding motif" fold. The structure of the P. furiosus RP-L35Ae presented in this article constitutes the first structural representative from this protein domain family. 相似文献
99.
RAGE, the multiligand receptor of the immunoglobulin superfamily of cell surface molecules, is implicated in innate and adaptive immunity. Complement component C1q serves roles in complement activation and antibody-independent opsonization. Using soluble forms of RAGE (sRAGE) and RAGE-expressing cells, we determined that RAGE is a native C1q globular domain receptor. Direct C1q-sRAGE interaction was demonstrated with surface plasmon resonance (SPR), with minimum K(d) 5.6 μM, and stronger binding affinity seen in ELISA-like experiments involving multivalent binding. Pull-down experiments suggested formation of a receptor complex of RAGE and Mac-1 to further enhance affinity for C1q. C1q induced U937 cell adhesion and phagocytosis was inhibited by antibodies to RAGE or Mac-1. These data link C1q and RAGE to the recruitment of leukocytes and phagocytosis of C1q-coated material. 相似文献