全文获取类型
收费全文 | 240132篇 |
免费 | 2943篇 |
国内免费 | 451篇 |
学科分类
工业技术 | 243526篇 |
出版年
2021年 | 2095篇 |
2019年 | 2019篇 |
2018年 | 3487篇 |
2017年 | 3426篇 |
2016年 | 3684篇 |
2015年 | 2236篇 |
2014年 | 3899篇 |
2013年 | 10196篇 |
2012年 | 6150篇 |
2011年 | 8309篇 |
2010年 | 6561篇 |
2009年 | 7238篇 |
2008年 | 7589篇 |
2007年 | 7716篇 |
2006年 | 6887篇 |
2005年 | 6050篇 |
2004年 | 5845篇 |
2003年 | 5625篇 |
2002年 | 5714篇 |
2001年 | 5586篇 |
2000年 | 5408篇 |
1999年 | 5323篇 |
1998年 | 12622篇 |
1997年 | 8954篇 |
1996年 | 6873篇 |
1995年 | 5351篇 |
1994年 | 4755篇 |
1993年 | 4648篇 |
1992年 | 3691篇 |
1991年 | 3363篇 |
1990年 | 3589篇 |
1989年 | 3459篇 |
1988年 | 3253篇 |
1987年 | 2858篇 |
1986年 | 2895篇 |
1985年 | 3334篇 |
1984年 | 3185篇 |
1983年 | 2851篇 |
1982年 | 2697篇 |
1981年 | 2775篇 |
1980年 | 2675篇 |
1979年 | 2596篇 |
1978年 | 2654篇 |
1977年 | 2917篇 |
1976年 | 3779篇 |
1975年 | 2344篇 |
1974年 | 2224篇 |
1973年 | 2351篇 |
1972年 | 1958篇 |
1971年 | 1839篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Julio E. Trevino Swati Mohan Alexandra E. Salinas Emilia Cueva Karen Lozano 《应用聚合物科学杂志》2021,138(28):50665
This study presents the development and characterization of PVDF-conjugated polymer nanofiber-based systems. Five different conducting polymers (CPs) were synthesized successfully and used to create the nanofiber systems. The CPs used are polyaniline (PANI), polypyrrole (PPY), polyindole (PIN), polyanthranilic acid (PANA), and polycarbazole (PCZ). Nanofiber systems were produced utilizing the Forcespinning® technique. The nanofiber systems were developed by mechanical stretching. No electrical field or post-process poling was used in the nanofiber systems. The morphology, structure, electrochemical and piezoelectric performance was characterized. All of the nanofiber PVDF/CP systems displayed higher piezoelectric performance than the fine fiber PVDF systems. The PVDF/PPY nanofiber system displays the highest piezoelectric performance of 15.56 V. The piezoelectric performance of the PVDF/CP nanofiber systems favors potential for an attractive source of energy where highly flexible membranes could be used in power actuators, sensors and portable, and wireless devices to mention some. 相似文献
4.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
5.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
6.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献
7.
Abulyazied Dalia E. Alturki Asma M. Youness Rasha A. Abomostafa H. M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4077-4092
Journal of Inorganic and Organometallic Polymers and Materials - In this work, a borosilicate glass sample (5SiO2–45B2O3–20Na2O–25CaO–5Ag2O) was added to nano-sized... 相似文献
8.
Dr. Yibin Zhang Dr. Shuai Xia Shulin Wan Tessa E. Steenwinkel Tara Vohs Prof. Rudy L. Luck Prof. Thomas Werner Prof. Haiying Liu 《Chembiochem : a European journal of chemical biology》2021,22(13):2282-2291
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae. 相似文献
9.
Deep geological repositories for radioactive waste contain metallic materials, either used to construct disposal canisters or as low-/intermediate-level waste (L/ILW). The safety relevance of corrosion is linked to canister lifetime in the former case and gas generation in the latter. More specifically, the Belgian “supercontainer” concept envisages mild steel for the used fuel disposal canister, and in the case of the Swiss L/ILW repository, mild steels are the largest metallic waste component due to the decommissioning of civilian power-generating facilities. For these circumstances, the corrosion environment is dominated by the chemistry of cement, which is used as buffer or backfill material. The corrosion behaviour of mild steel in anoxic environments was studied through the analysis of the hydrogen end-product. Hydrogen analysis was conducted by periodically purging the cell head-space and analysing the gas using a solid-state hydrogen sensor. While this method is limited to providing only uniform corrosion rates averaged over periods of time, ranging from weeks to months, it provides excellent resolution and sensitivity. The test cell environments were matched against the anticipated Belgian high-level waste and Swiss L/ILW repository environments, and also against experiments that have been conducted by other researchers for comparative purposes. Samples were exposed to synthetic cement pore waters, representing fresh and degraded cement. In young cement waters, the formation of initial corrosion products resulted in steel wire corrosion rates of the order of µm/year, which, at 80°C rapidly declined to ∼10 nm/year. In contrast, SA516 grade 70 steel plate corroded much more slowly under similar conditions. In aged cement waters, initial corrosion rates were higher but declined faster towards a longer-term rate of ∼10 nm/year. 316L stainless steel, embedded in cementitious material, corroded at a rate of <1 nm/year at 50°C. 相似文献
10.
Glass and Ceramics - An analysis of the specific mechanisms of the influence of the state of the grain structure on the thermoelectric properties (electrical resistivity and total thermal... 相似文献