全文获取类型
收费全文 | 4502篇 |
免费 | 162篇 |
国内免费 | 5篇 |
学科分类
工业技术 | 4669篇 |
出版年
2023年 | 27篇 |
2022年 | 189篇 |
2021年 | 206篇 |
2020年 | 93篇 |
2019年 | 99篇 |
2018年 | 108篇 |
2017年 | 85篇 |
2016年 | 100篇 |
2015年 | 95篇 |
2014年 | 135篇 |
2013年 | 260篇 |
2012年 | 174篇 |
2011年 | 229篇 |
2010年 | 195篇 |
2009年 | 161篇 |
2008年 | 218篇 |
2007年 | 194篇 |
2006年 | 149篇 |
2005年 | 136篇 |
2004年 | 121篇 |
2003年 | 99篇 |
2002年 | 124篇 |
2001年 | 74篇 |
2000年 | 67篇 |
1999年 | 85篇 |
1998年 | 89篇 |
1997年 | 58篇 |
1996年 | 77篇 |
1995年 | 53篇 |
1994年 | 56篇 |
1993年 | 54篇 |
1992年 | 67篇 |
1991年 | 18篇 |
1990年 | 49篇 |
1989年 | 69篇 |
1988年 | 46篇 |
1987年 | 52篇 |
1986年 | 56篇 |
1985年 | 53篇 |
1984年 | 60篇 |
1983年 | 46篇 |
1982年 | 32篇 |
1981年 | 47篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1978年 | 22篇 |
1977年 | 23篇 |
1976年 | 30篇 |
1975年 | 27篇 |
1970年 | 17篇 |
排序方式: 共有4669条查询结果,搜索用时 15 毫秒
101.
102.
This study investigates the structural, morphological, thermal, and mechanical properties of type A gelatin/montmorillonite (MMT) films as a function of MMT concentration. The variations of the X‐ray diffraction pattern suggest that the structure of the nanocomposites turns from intercalated to exfoliated on increasing clay loading up to 20 wt %. Simultaneously, gelatin interaction with clay negative sheets during gelling provokes a reduction of the triple helix content of the composite films, in agreement with the reduction of the relative intensity of the 1.1 nm diffraction reflection of gelatin and of the values of denaturation enthalpy. On the other hand, the increase of the denaturation and decomposition temperatures, the significant rise of the Young's modulus, as well as the swelling decrease observed as clay content increases, demonstrate a relevant stabilizing effect of MMT on gelatin. The reinforcement action of MMT allows to utilize a relatively low concentration of the crosslinking agent genipin to further stabilize the films. The synergic action of clay and genipin prevents dissolution of the nanocomposites in aqueous solution and enhances their mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40301. 相似文献
103.
104.
Urszula Wjcik-Bojek Barbara Ralska Beata Sadowska 《International journal of molecular sciences》2022,23(2)
The main purpose of this review is to present justification for the urgent need to implement specific prophylaxis of invasive Staphylococcus aureus infections. We emphasize the difficulties in achieving this goal due to numerous S. aureus virulence factors important for the process of infection and the remarkable ability of these bacteria to avoid host defense mechanisms. We precede these considerations with a brief overview of the global necessitiy to intensify the use of vaccines against other pathogens as well, particularly in light of an impasse in antibiotic therapy. Finally, we point out global trends in research into modern technologies used in the field of molecular microbiology to develop new vaccines. We focus on the vaccines designed to fight the infections caused by S. aureus, which are often resistant to the majority of available therapeutic options. 相似文献
105.
Giulia Sierri Roberta Dal Magro Barbara Vergani Biagio Eugenio Leone Beatrice Formicola Lorenzo Taiarol Stefano Fagioli Marcelo Kravicz Lucio Tremolizzo Laura Calabresi Francesca Re 《International journal of molecular sciences》2022,23(1)
The cerebral synthesis of cholesterol is mainly handled by astrocytes, which are also responsible for apoproteins’ synthesis and lipoproteins’ assembly required for the cholesterol transport in the brain parenchyma. In Alzheimer disease (AD), these processes are impaired, likely because of the astrogliosis, a process characterized by morphological and functional changes in astrocytes. Several ATP-binding cassette transporters expressed by brain cells are involved in the formation of nascent discoidal lipoproteins, but the effect of beta-amyloid (Aβ) assemblies on this process is not fully understood. In this study, we investigated how of Aβ1-42-induced astrogliosis affects the metabolism of cholesterol in vitro. We detected an impairment in the cholesterol efflux of reactive astrocytes attributable to reduced levels of ABCA1 transporters that could explain the decreased lipoproteins’ levels detected in AD patients. To approach this issue, we designed biomimetic HDLs and evaluated their performance as cholesterol acceptors. The results demonstrated the ability of apoA-I nanodiscs to cross the blood–brain barrier in vitro and to promote the cholesterol efflux from astrocytes, making them suitable as a potential supportive treatment for AD to compensate the depletion of cerebral HDLs. 相似文献
106.
Florence Bonnet-Magnaval Leïla Halidou Diallo Valrie Brunchault Nathalie Laugero Florent Morfoisse Florian David Emilie Roussel Manon Nougue Audrey Zamora Emmanuelle Marchaud Florence Tatin Anne-Catherine Prats Barbara Garmy-Susini Luc DesGroseillers Eric Lacazette 《International journal of molecular sciences》2022,23(1)
107.
Elbieta Masiukiewicz Barbara Rzeszotarska Gabriela Fortuna Kazimierz Kochman 《Advanced Synthesis \u0026amp; Catalysis》1991,333(4):573-578
Synthesis of two mammalian gonadoliberin analogs, [Gln1]GnRH and [Glu1]GnRH, in solution by the peptide segment coupling of the [(2 + 4) + 4] type has been described. 相似文献
108.
109.
Bernarda Majc Anamarija Habi
Metka Novak Ana Rotter Andrej Por
nik Jernej Mlakar Vera
upunski Ura Pe
ar Fonovi Damijan Knez Nace Zidar Stanislav Gobec Janko Kos Tamara Lah Turnek Anja Pilar Barbara Breznik 《International journal of molecular sciences》2022,23(3)
Glioblastoma (GBM) is the most common and deadly primary brain tumor in adults. Understanding GBM pathobiology and discovering novel therapeutic targets are critical to finding efficient treatments. Upregulation of the lysosomal cysteine carboxypeptidase cathepsin X has been linked to immune dysfunction and neurodegenerative diseases, but its role in cancer and particularly in GBM progression in patients is unknown. In this study, cathepsin X expression and activity were found to be upregulated in human GBM tissues compared to low-grade gliomas and nontumor brain tissues. Cathepsin X was localized in GBM cells as well as in tumor-associated macrophages and microglia. Subsequently, potent irreversible (AMS36) and reversible (Z7) selective cathepsin X inhibitors were tested in vitro. Selective cathepsin X inhibitors decreased the viability of patient-derived GBM cells as well as macrophages and microglia that were cultured in conditioned media of GBM cells. We next examined the expression pattern of neuron-specific enzyme γ-enolase, which is the target of cathepsin X. We found that there was a correlation between high proteolytic activity of cathepsin X and C-terminal cleavage of γ-enolase and that cathepsin X and γ-enolase were colocalized in GBM tissues, preferentially in GBM-associated macrophages and microglia. Taken together, our results on patient-derived material suggest that cathepsin X is involved in GBM progression and is a potential target for therapeutic approaches against GBM. 相似文献
110.
Saturated water solutions of selected alkaline and alkaline earth metal salts have been studied whether or not they catalyze the formation of levulinic acid from glucose. The most active was a solution of magnesium chloride. Activity was further increased in the system (MgCl2+H+). We observed complete inhibition of this reaction by NO3−. Contrary to the generally accepted opinion that formation of hydroxymethylfurfural is only H+ catalyzed, we observed activity of the system formed from MgO and MgCl2 when one starts from glucose. (MgCl2+ MgO) in water is alkaline. 相似文献