全文获取类型
收费全文 | 5709篇 |
免费 | 478篇 |
国内免费 | 182篇 |
专业分类
电工技术 | 229篇 |
技术理论 | 2篇 |
综合类 | 342篇 |
化学工业 | 1084篇 |
金属工艺 | 324篇 |
机械仪表 | 326篇 |
建筑科学 | 536篇 |
矿业工程 | 205篇 |
能源动力 | 137篇 |
轻工业 | 303篇 |
水利工程 | 98篇 |
石油天然气 | 419篇 |
武器工业 | 53篇 |
无线电 | 639篇 |
一般工业技术 | 674篇 |
冶金工业 | 274篇 |
原子能技术 | 57篇 |
自动化技术 | 667篇 |
出版年
2024年 | 28篇 |
2023年 | 108篇 |
2022年 | 170篇 |
2021年 | 255篇 |
2020年 | 204篇 |
2019年 | 174篇 |
2018年 | 186篇 |
2017年 | 215篇 |
2016年 | 189篇 |
2015年 | 235篇 |
2014年 | 295篇 |
2013年 | 389篇 |
2012年 | 388篇 |
2011年 | 408篇 |
2010年 | 346篇 |
2009年 | 298篇 |
2008年 | 295篇 |
2007年 | 272篇 |
2006年 | 306篇 |
2005年 | 248篇 |
2004年 | 174篇 |
2003年 | 143篇 |
2002年 | 130篇 |
2001年 | 100篇 |
2000年 | 98篇 |
1999年 | 133篇 |
1998年 | 123篇 |
1997年 | 108篇 |
1996年 | 82篇 |
1995年 | 63篇 |
1994年 | 49篇 |
1993年 | 39篇 |
1992年 | 29篇 |
1991年 | 21篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有6369条查询结果,搜索用时 15 毫秒
991.
Gong Q Wang J Ahmad KM Csordas AT Zhou J Nie J Stewart R Thomson JA Rossi JJ Soh HT 《Analytical chemistry》2012,84(12):5365-5371
Many analytical techniques benefit greatly from the use of affinity reagent pairs, wherein each reagent recognizes a discrete binding site on a target. For example, antibody pairs have been widely used to dramatically increase the specificity of enzyme linked immunosorbent assays (ELISA). Nucleic acid-based aptamers offer many advantageous features relative to protein-based affinity reagents, including well-established chemical synthesis, thermostability, and low production cost. However, the generation of suitable aptamer pairs has posed a significant challenge, and few such pairs have been reported to date. To address this important challenge, we present multivalent aptamer isolation systematic evolution of ligands by exponential enrichment (MAI-SELEX), a technique designed for the efficient selection of aptamer pairs. In contrast to conventional selection methods, our method utilizes two selection modules to generate separate aptamer pools that recognize distinct binding sites on a single target. Using MAI-SELEX, we have isolated two groups of 2'-fluoro-modified RNA aptamers that specifically recognize the αV or β3 subunits of integrin αVβ3. These aptamers exhibit low nanomolar affinities for their targets, with minimal cross-reactivity to other closely related integrin homologues. Moreover, we show that these aptamer pairs do not interfere with each other's binding and effectively detect the target even in complex mixtures such as undiluted serum. 相似文献
992.
In this study, we have used PEO (plasma electrolytic oxidation) for the production of oxide coatings on a Ti–6Al–4V alloy at two different current modes, namely pulsed unipolar and bipolar. Optical emission spectroscopy (OES) in the visible and near UV band (280–800 nm) was used to characterize the PEO plasma. The emission spectra were recorded and the plasma temperature profile versus processing time was constructed using a line intensity ratios method. The aim of this work was to study the effect of the process parameters, including current mode and pulse duration time, on the plasma characteristics, surface morphology and microstructure and corrosion resistance of oxides grown on Ti–6Al–4V by PEO process. Scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) were used to study the coating microstructure, morphology and phase composition. The corrosion resistance of the coated and uncoated samples was examined by potentiodynamic polarization in a 3.5% NaCl solution. It was found that the plasma temperature profiles are significantly influenced by changing the current mode from unipolar to bipolar. The strongest discharges that are initiated at the interface between the substrate and the coating can be reduced or eliminated by using a bipolar current mode. This produces a thinner, denser and more corrosion-resistant coating. 相似文献
993.
M. Guo X. Wang H.M. Zhou L. Li F.L. Nie Y. Cheng Y.F. Zheng 《Materials science & engineering. C, Materials for biological applications》2012,32(4):909-915
Porous silver scaffolds, with the porosity ranging from 68% to 81% and the apparent density ranging from 0.4 to 1 g?cm? 3 were prepared by electroplating method using cellular carbon skeleton as the substrate. The microstructure, mechanical property, cytotoxicity and antibacterial activity of the prepared porous silver scaffold were studied. The present porous silver scaffolds had a highly three-dimensional trabecular porous structure with the porosity and the apparent density close to that of the cancellous bone. Furthermore, the mechanical property such as elastic modulus and yield strength of the porous silver scaffolds were lower than that of commercial available porous Ti and porous Ti alloys but much closer to that of the cancellous bone and porous Ta. In addition, study of in vitro behavior showed that the porous silver scaffold possessed significant antibacterial capability of inhibition of bacterial proliferation and adherence against Staphylococcus aureus and Staphylococcus epidermidis, and little cytotoxicity to Mg-63 cell line and NIH-3T3 cell line. Consequently, the porous silver scaffolds prepared by electrodeposition possess a promising application for bone implants. 相似文献
994.
Songlin Nie Jiandong Wen Yongping Li Xionghui Tang Guohe Huang 《Optimization and Engineering》2012,13(2):319-347
A fuzzy robust nonlinear programming model is developed for the assessment of filter allocation and replacement strategies in hydraulic systems under uncertainty. It integrates the methods of fuzzy mathematic programming (FMP) and robust programming (RP) within the mixed integer nonlinear programming framework, and can facilitate dynamic analysis and optimization of filters allocation and replacement planning where the uncertainties are expressed as fuzzy membership functions. In modeling formulation, theory of contamination wear of typical hydraulic components is introduced to strengthen the presentation of relationship between system contamination and work performance. The fuzzy decision space is delimited into a more robust one by specifying the uncertainties through dimensional enlargement of the original fuzzy constraints. The piecewise linearization approach is employed to handle the nonlinearities of problem. The developed method has been applied to a case of planning filter allocation and replacement strategies under uncertainty and the generated optimal solution will help to reduce the total system cost and failure-risk level of the FPS. 相似文献
995.
Han S Liu Y Nie X Xu Q Jiao F Li W Zhao Y Wu Y Chen C 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(10):1596-1606
The use of biodegradable polymeric nanoparticles (NPs) for controlled drug delivery has shown significant therapeutic potential. Polyaspartic acid and polylactic acid are the most intensively studied biodegradable polymers. In the present study, novel amphiphilic biodegradable co-polymer NPs, poly(L-aspartic acid-co-lactic acid) with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) (poly(AA-co-LA)/DPPE) is synthesized and subsequently used to encapsulate an antitumor drug doxorubicin (DOX). The formulation parameters of the NPs are optimized to improve encapsulation efficiency. The resulting drug-loaded NPs possess better size homogeneity (polydispersity) and exhibit pH-responsive drug release profiles. Cellular viability assays indicate that the poly(AA-co-LA)/DPPE NPs did not induce cell death, whereas doxorubicin encapsulated NPs were cytotoxic to various types of tumor cells. In addition, the free NPs could not enter the cell nuclei after internalized in tumor cells. The DOX-loaded NPs exhibit efficient intracellular delivery in tumor cells with co-localization in lysosome and delay entering into the nucleus, which suggests a time- and pH-dependent drug release profile within cells. When applied to deliver chemotherapeutics to a mouse xenograft model of human lung adenocarcinoma, DOX-loaded NPs have a comparable antitumor activity with free DOX, and greatly reduce systemic toxicity and mortality. The delivery of cytotoxic drugs directly to the nucleus specifically within tumor cells is of great interest. These results demonstrate the feasibility of the application of the amphiphilic polyaspartic acid derivative, poly(AA-co-LA)/DPPE, as a nanocarrier for cell nuclear delivery of potent antitumor drugs. 相似文献
996.
997.
Nie H Yang Z Huang S Wu Z Wang H Yu R Jiang J 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(9):1407-1414
A novel electrochemical strategy that uses DNA-wrapped carbon nanotubes (CNTs) as electrochemical labels is developed for sensitive and selective detection of sequence-specific DNA. The presence of target DNA mediates the formation of a sandwiched complex between the DNA-wrapped CNT and a hairpin DNA capture probe immobilized on magnetic beads. This allows target-selective collection of the CNT labels by magnetic separation and transfer on the electrode surface modified with an insulating self-assembled monolayer (SAM). After treatment with N,N-dimethylformamide, the collected sandwiched complex releases the bare CNTs and facilitates the removal of magnetic beads from the electrode surface. The bare CNTs can then assemble on the SAM-modified electrode surface and mediate efficient electron transfer between the electrode and the electroactive species in the solution with a strong current signal generated. The results indicate that the developed strategy shows a sensitive response to target DNA with a desirable signal gain and a low detection limit of 0.9 pM. This strategy is also demonstrated to provide excellent differentiation of single-base mismatch in target DNA. It is expected that this electrochemical strategy may hold great potential as a novel platform for clinical diagnostics and genetic analysis. 相似文献
998.
采用外涂布工艺技术制备了聚丙烯涂覆膜,并将不同浓度的失水山梨醇脂肪酸酯溶液涂覆于聚丙烯薄膜上,测试进行水浴实验之后的涂覆膜的透光率及力学性能,并与未涂膜的透光率进行对比和评价。结果表明:空白聚丙烯膜的透光率为93.24%,涂覆膜的透光率明显提高,当失水山梨醇脂肪酸酯的质量分数为12%时,薄膜的透光率最高,达96.03%;同时,涂层使薄膜的力学性能有不同程度的提高。红外光谱分析结果表明:酯基团在水浴实验时水解可生成亲水基团,改善薄膜的润湿张力,因此薄膜表面涂覆层对透光率的改善起到了较大作用。 相似文献
999.
1000.
Anqiang Pan Daiwon ChoiJi-Guang Zhang Shuquan Liang Guozhong CaoZimin Nie Bruce W. AreyJun Liu 《Journal of power sources》2011,196(7):3646-3649
In this work, we have synthesized monoclinic Li3V2(PO4)3 nanobelts via a single-step, solid-state reaction process in a molten hydrocarbon. The as-prepared Li3V2(PO4)3 nanoparticles have a unique nanobelt shape and are ∼50-nm thick. When cycled in a voltage range between 3.0 V and 4.3 V at a 1C rate, these unique Li3V2(PO4)3 nanobelts demonstrate a specific discharge capacity of 131 mAh g−1 (which is close to the theoretical capacity of 132 mAh g−1) and stable cycling characteristics. 相似文献