全文获取类型
收费全文 | 30229篇 |
免费 | 2999篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 1442篇 |
综合类 | 411篇 |
化学工业 | 13348篇 |
金属工艺 | 377篇 |
机械仪表 | 680篇 |
建筑科学 | 1652篇 |
矿业工程 | 183篇 |
能源动力 | 459篇 |
轻工业 | 4904篇 |
水利工程 | 226篇 |
石油天然气 | 139篇 |
无线电 | 830篇 |
一般工业技术 | 4581篇 |
冶金工业 | 727篇 |
原子能技术 | 61篇 |
自动化技术 | 3222篇 |
出版年
2023年 | 930篇 |
2022年 | 1216篇 |
2021年 | 1933篇 |
2020年 | 1304篇 |
2019年 | 972篇 |
2018年 | 1002篇 |
2017年 | 863篇 |
2016年 | 1134篇 |
2015年 | 1194篇 |
2014年 | 1357篇 |
2013年 | 2240篇 |
2012年 | 1347篇 |
2011年 | 1335篇 |
2010年 | 1444篇 |
2009年 | 1546篇 |
2008年 | 1010篇 |
2007年 | 943篇 |
2006年 | 717篇 |
2005年 | 595篇 |
2004年 | 495篇 |
2003年 | 458篇 |
2002年 | 342篇 |
2001年 | 258篇 |
2000年 | 158篇 |
1999年 | 222篇 |
1998年 | 307篇 |
1997年 | 254篇 |
1996年 | 302篇 |
1995年 | 260篇 |
1994年 | 217篇 |
1993年 | 282篇 |
1992年 | 217篇 |
1991年 | 167篇 |
1990年 | 189篇 |
1989年 | 206篇 |
1988年 | 170篇 |
1987年 | 192篇 |
1986年 | 222篇 |
1985年 | 200篇 |
1984年 | 194篇 |
1983年 | 198篇 |
1982年 | 170篇 |
1981年 | 219篇 |
1980年 | 184篇 |
1979年 | 190篇 |
1977年 | 161篇 |
1975年 | 214篇 |
1974年 | 189篇 |
1973年 | 367篇 |
1972年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Zein‐based ultrathin fibers containing ceramic nanofillers obtained by electrospinning. II. Mechanical properties,gas barrier,and sustained release capacity of biocide thymol in multilayer polylactide films 下载免费PDF全文
The combination of electrospinning technology and nanomaterials such as nanoclays can synergistically lead to novel materials with enhanced properties and functionalities for their usage in passive and active packaging applications. Part I of this work was focused on the development of ultrathin zein fibers containing nanoclays, which were oriented along the fiber axis and increased the thermal properties. Part II presents the use of the hybrid fibers as passive and active components in multilayer packaging structures. The hybrid fibers are incorporated in poly(lactic acid) films via a two‐step process: Electrospinning and compression molding. The composites thus produced presented improved mechanical and barrier properties than the unfilled material. The natural biocide extract thymol is then incorporated in the coating, and its sustained release properties are shown. The antimicrobial capacity of the hybrid fibers was also determined against foodborne bacteria. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40768. 相似文献
14.
Comparative Cytotoxicity of Artemisinin and Cisplatin and Their Interactions with Chlorogenic Acids in MCF7 Breast Cancer Cells 下载免费PDF全文
Dr. John O. Suberu Dr. Isolda Romero‐Canelón Dr. Neil Sullivan Prof. Alexei A. Lapkin Dr. Guy C. Barker 《ChemMedChem》2014,9(12):2791-2797
In parts of Africa and Asia, self‐medication with a hot water infusion of Artemisia annua (Artemisia tea) is a common practice for a number of ailments including malaria and cancer. In our earlier work, such an extract showed better potency than artemisinin alone against both chloroquine‐sensitive and ‐resistant parasites. In this study, in vitro tests of the infusion in MCF7 cells showed high IC50 values (>200 μM ). The combination of artemisinin and 3‐caffeoylquinic acid (3CA), two major components in the extract, was strongly antagonistic and gave a near total loss of cytotoxicity for artemisinin. We observed that the interaction of 3CAs with another cytotoxic compound, cisplatin, showed potentiation of activity by 2.5‐fold. The chelation of cellular iron by 3CA is hypothesized as a possible explanation for the loss of artemisinin activity. 相似文献
15.
Linear Aliphatic Dialkynes as Alternative Linkers for Double‐Click Stapling of p53‐Derived Peptides 下载免费PDF全文
Yu Heng Lau Dr. Peterson de Andrade Dr. Grahame J. McKenzie Prof. Ashok R. Venkitaraman Prof. David R. Spring 《Chembiochem : a European journal of chemical biology》2014,15(18):2680-2683
We investigated linear aliphatic dialkynes as a new structural class of i,i+7 linkers for the double‐click stapling of p53‐based peptides. The optimal combination of azido amino acids and dialkynyl linker length for MDM2 binding was determined. In a direct comparison between aliphatic and aromatic staple scaffolds, the aliphatic staples resulted in superior binding to MDM2 in vitro and superior p53‐activating capability in cells when using a diazidopeptide derived from phage display. This work demonstrates that the nature of the staple scaffold is an important factor that can affect peptide bioactivity in cells. 相似文献
16.
Renata Cardoso Magagnin Maria Solange Gurgel de Castro Fontes Rosio Fernandez Baca Salcedo 《土木工程与建筑:英文版》2014,(12):1567-1574
This paper presents an assessment of the spatial quality of a pedestrian street located in downtown Bauru, S~o Paulo State, Brazil, from the application of some urban sustainability indicators. Multi-method was used to evaluate the thermal comfort quality of users, urban accessibility and preservation of architectural heritage. The results show that the sustainability indicators, apart from being effective tools in identifying problems, can assist local managers in decision making, planning and monitoring of pedestrian public space. These indicators contribute to a broad diagnosis of the pedestrian street and also the formulation of programs, projects and municipal policies, aimed at providing a better life quality for pedestrians. 相似文献
17.
Ksenia Skobeleva Alexey Shalygin Elena Mikhaylova Irina Guzhova Maria Ryazantseva Elena Kaznacheyeva 《International journal of molecular sciences》2022,23(23)
Alzheimer’s disease (AD) is the most common cause of age-related dementia. Neuronal calcium homeostasis impairment may contribute to AD. Here we demonstrated that voltage-gated calcium (VGC) entry and store-operated calcium (SOC) entry regulated by calcium sensors of intracellular calcium stores STIM proteins are affected in hippocampal neurons of the 5xFAD transgenic mouse model. We observed excessive SOC entry in 5xFAD mouse neurons, mediated by STIM1 and STIM2 proteins with increased STIM1 contribution. There were no significant changes in cytoplasmic calcium level, endoplasmic reticulum (ER) bulk calcium levels, or expression levels of STIM1 or STIM2 proteins. The potent inhibitor BTP-2 and the FDA-approved drug leflunomide reduced SOC entry in 5xFAD neurons. In turn, excessive voltage-gated calcium entry was sensitive to the inhibitor of L-type calcium channels nifedipine but not to the T-type channels inhibitor ML218. Interestingly, the depolarization-induced calcium entry mediated by VGC channels in 5xFAD neurons was dependent on STIM2 but not STIM1 protein in cells with replete Ca2+ stores. The result gives new evidence on the VGC channel modulation by STIM2. Overall, the data demonstrate the changes in calcium signaling of hippocampal neurons of the AD mouse model, which precede amyloid plaque accumulation or other signs of pathology manifestation. 相似文献
18.
Maria Addolorata Bonifacio Riccardo Laterza Angela Vinella Annalisa Schirinzi Mariangela Defilippis Francesca Di Serio Angelo Ostuni Antonio Fasanella Maria Addolorata Mariggi 《International journal of molecular sciences》2022,23(17)
Serological assays are useful in investigating the development of humoral immunity against SARS-CoV-2 in the context of epidemiological studies focusing on the spread of protective immunity. The plaque reduction neutralization test (PRNT) is the gold standard method to assess the titer of protective antibodies in serum samples. However, to provide a result, the PRNT requires several days, skilled operators, and biosafety level 3 laboratories. Therefore, alternative methods are being assessed to establish a relationship between their outcomes and PRNT results. In this work, four different immunoassays (Roche Elecsys® Anti SARS-CoV-2 S, Snibe MAGLUMI® SARS-CoV-2 S-RBD IgG, Snibe MAGLUMI® 2019-nCoV IgG, and EUROIMMUN® SARS-CoV-2 NeutraLISA assays, respectively) have been performed on individuals healed after SARS-CoV-2 infection. The correlation between each assay and the reference method has been explored through linear regression modeling, as well as through the calculation of Pearson’s and Spearman’s coefficients. Furthermore, the ability of serological tests to discriminate samples with high titers of neutralizing antibodies (>160) has been assessed by ROC curve analyses, Cohen’s Kappa coefficient, and positive predictive agreement. The EUROIMMUN® NeutraLISA assay displayed the best correlation with PRNT results (Pearson and Spearman coefficients equal to 0.660 and 0.784, respectively), as well as the ROC curve with the highest accuracy, sensitivity, and specificity (0.857, 0.889, and 0.829, respectively). 相似文献
19.
20.
Irina Lascu Ana Maria Tnase Piotr Jablonski Iulia Chiciudean Maria Irina Preda Sorin Avramescu Knut Irgum Ileana Stoica 《International journal of molecular sciences》2022,23(22)
Polyhydroxyalkanoates (PHA) are promising biodegradable and biocompatible bioplastics, and extensive knowledge of the employed bacterial strain’s metabolic capabilities is necessary in choosing economically feasible production conditions. This study aimed to create an in-depth view of the utilization of Photobacterium ganghwense C2.2 for PHA production by linking a wide array of characterization methods: metabolic pathway annotation from the strain’s complete genome, high-throughput phenotypic tests, and biomass analyses through plate-based assays and flask and bioreactor cultivations. We confirmed, in PHA production conditions, urea catabolization, fatty acid degradation and synthesis, and high pH variation and osmotic stress tolerance. With urea as a nitrogen source, pure and rapeseed-biodiesel crude glycerol were analyzed comparatively as carbon sources for fermentation at 20 °C. Flask cultivations yielded 2.2 g/L and 2 g/L PHA at 120 h, respectively, with molecular weights of 428,629 g/mol and 81,515 g/mol. Bioreactor batch cultivation doubled biomass accumulation (10 g/L and 13.2 g/L) in 48 h, with a PHA productivity of 0.133 g/(L·h) and 0.05 g/(L·h). Thus, phenotypic and genomic analyses determined the successful use of Photobacterium ganghwense C2.2 for PHA production using urea and crude glycerol and 20 g/L NaCl, without pH adjustment, providing the basis for a viable fermentation process. 相似文献