全文获取类型
收费全文 | 3625篇 |
免费 | 425篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 36篇 |
综合类 | 2篇 |
化学工业 | 883篇 |
金属工艺 | 114篇 |
机械仪表 | 184篇 |
建筑科学 | 136篇 |
矿业工程 | 7篇 |
能源动力 | 96篇 |
轻工业 | 520篇 |
水利工程 | 30篇 |
石油天然气 | 11篇 |
无线电 | 402篇 |
一般工业技术 | 761篇 |
冶金工业 | 226篇 |
原子能技术 | 27篇 |
自动化技术 | 628篇 |
出版年
2024年 | 8篇 |
2023年 | 61篇 |
2022年 | 60篇 |
2021年 | 184篇 |
2020年 | 148篇 |
2019年 | 146篇 |
2018年 | 210篇 |
2017年 | 203篇 |
2016年 | 231篇 |
2015年 | 156篇 |
2014年 | 204篇 |
2013年 | 290篇 |
2012年 | 279篇 |
2011年 | 302篇 |
2010年 | 219篇 |
2009年 | 206篇 |
2008年 | 196篇 |
2007年 | 149篇 |
2006年 | 95篇 |
2005年 | 94篇 |
2004年 | 66篇 |
2003年 | 62篇 |
2002年 | 63篇 |
2001年 | 49篇 |
2000年 | 34篇 |
1999年 | 33篇 |
1998年 | 46篇 |
1997年 | 39篇 |
1996年 | 35篇 |
1995年 | 19篇 |
1994年 | 22篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1963年 | 2篇 |
排序方式: 共有4063条查询结果,搜索用时 390 毫秒
991.
Heart failure (HF) and atrial fibrillation (AF) are two growing epidemics associated with significant morbidity and mortality. They often coexist due to common risk factors and shared pathophysiological mechanisms. Patients presenting with both HF and AF have a worse prognosis and present a particular therapeutic challenge to clinicians. This review aims to appraise the common pathophysiological background, as well as the prognostic and therapeutic implications of coexistent HF and AF. 相似文献
992.
Marek Bajda Jakub Jończyk Barbara Malawska S?awomir Filipek 《International journal of molecular sciences》2014,15(3):5128-5139
β-Secretase (BACE-1) constitutes an important target for search of anti-Alzheimer’s drugs. The first inhibitors of this enzyme were peptidic compounds with high molecular weight and low bioavailability. Therefore, the search for new efficient non-peptidic inhibitors has been undertaken by many scientific groups. We started our work from the development of in silico methodology for the design of novel BACE-1 ligands. It was validated on the basis of crystal structures of complexes with inhibitors, redocking, cross-docking and training/test sets of reference ligands. The presented procedure of assessment of the novel compounds as β-secretase inhibitors could be widely used in the design process. 相似文献
993.
994.
995.
Fernando C. Franceschini Tatiana T. da R. Tavares Daniela Bianchini Maria do Carmo M. Alves Maria Lujan Ferreira João H. Z. dos Santos 《应用聚合物科学杂志》2009,112(1):563-571
rac‐Dimethylsilylenebis(indenyl)zirconium dichloride was grafted onto commercial methyl aluminoxane modified silica (SMAO) at different loadings (0.1–1.5 wt % Zr/SMAO). Supported catalysts were evaluated in ethylene polymerization with isoprenylaluminum as a cocatalyst. The characterization of two supported catalysts bearing 0.3 and 0.8 wt % Zr/SiO2 by extended X‐ray absorption fine structure indicated that the number and the intensity of the peaks beyond the coordination shell, associated with the next nearest neighbors, depended on the Zr concentration. For the catalyst with a higher Zr content, only one peak (2.8 Å) was observed. The catalyst with 0.3 wt % Zr/SMAO presented two small peaks at 2.8 and 3.8 Å. Polymers produced with the supported catalysts presented lower crystallinity and higher molar mass and polydispersity values in comparison to that produced by the homogeneous one. Gel permeation chromatogram deconvolution suggested the presence of four catalyst sites for the supported systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
996.
Soline Boyer-Richard Cédric Robert Lionel Gérard Jan-Peter Richters Régis André Jo?l Bleuse Henri Mariette Jacky Even Jean-Marc Jancu 《Nanoscale research letters》2012,7(1):543
We perform accurate tight binding simulations to design type-II short-period CdSe/ZnTe superlattices suited for photovoltaic applications. Absorption calculations demonstrate a very good agreement with optical results with threshold strongly depending on the chemical species near interfaces. 相似文献
997.
998.
Hyun Young Kil Eun Soo Seong Bimal Kumar Ghimire Ill-Min Chung Soon Sung Kwon Eun Jeong Goh Kweon Heo Myong Jo Kim Jung Dae Lim Dokyoung Lee Chang Yeon Yu 《Food chemistry》2009
Here, we report the antioxidant and antimicrobial activities of sorghum (Sorghum bicolor Moench) extracts prepared from 25 cultivars from South Korea. Four cultivars of sorghum were extracted with methanol, then further fractioned with n-hexane, ethyl acetate, n-butanol, and water. The RC50 (the concentration of antioxidant required to achieve absorbance equal to 50% that of a control containing no antioxidants) value of the DPPH method and reducing power showed higher efficiency in the BuOH layer of all selected cultivars except Neulsusu. The various fractions were then examined for antimicrobial activity by a serial two fold dilution assays using the paper disc method. The methanol extracts showed higher levels of antimicrobial activity than the other fractions. Our results indicate that sorghum extracts could be used as a source of antioxidant and antimicrobial ingredients in the food industry. 相似文献
999.
Joon-Soo Sim A-Rang Im Seung Mock Cho Hae Jin Jang Jin Ho Jo Yeong Shik Kim 《Food chemistry》2007,101(2):532-539
We evaluated the content and biochemical properties of chondroitin sulfate (CS) in shark cartilage powders being used as nutraceutical supplements. The quantities of CS in shark cartilage products (SCPs) and finished products containing shark cartilage powder were determined by analyzing unsaturated disaccharides after treatment with chondroitinase ABC, and the results were compared with the specifications on the product labels. This method was validated and good linearity (r ? 0.999) was obtained. The recovery ranged from 95.27% to 102.39% with precision from 2.27% to 3.95%. Furthermore, the average molecular weights (MW) and the origins of CS in SCPs and finished products were evaluated by agarose gel-electrophoresis and assessment of disaccharide compositional patterns, respectively. Quantitative and compositional analysis of disaccharides after enzymatic depolymerization showed that the amount of CS in the samples of SCPs ranged from 0% to 28.92 ± 0.03%. All of the SCP samples except for SCP D had ΔDi-2,6diS and had more ΔDi-6S than ΔDi-4S, indicating that they originated from shark cartilage. In the finished products, the amount of CS ranged from 0.58 ± 0.01% to 21.30 ± 0.08%. With the exception of SCP D and two finished products (F and D), which contained CS with lower MWs, the average MW of CS in the SCPs and finished products was approximately 40 kDa or higher than that of MW standard (40 kDa) of CS. These analyses contribute to the evaluation of the quantity and quality of CS in SCPs and finished products containing CS, which is necessary for the manufacture of high-grade nutraceuticals. 相似文献
1000.
Nenad Gubeljak Jelena Vojvodi? Tuma Jo?ef Predan 《Engineering Fracture Mechanics》2007,74(6):995-1005
High-alloyed Cr-Ni-based two-phase stainless steel (SS) cast alloys are commonly used in nuclear power plants. The mechanical equipment in these facilities can contribute to a reduction in its resistance to stable crack growth as a result of extended operating times and high temperatures. The toughness of these materials strongly depends on their delta (δ) ferrite content, which spinodally decomposes into two phases with different ratios of Cr and Ni at a relatively low (slightly above 300 °C) temperature. This temperature is similar to the operating temperature of the vital parts, for example, the coolant system. The formation of two phases with the same crystal structure but different lattice parameters causes internal elastic stresses that result in a hardness increase and an impact-toughness decrease. The result is an increased risk of crack formation in the stress-concentration zones such as the critical regions of different welded joints (e.g. “L, T, K and X” shapes). The values of the critical stress intensity factor change according to its position along the crack contour. Therefore, the aim of our study was to assess the influence of the materials’ changes on the crack extension and the decrease of the primary pipeline’s bearing capacity by taking account of the increased temperature and time of operation for the given loading conditions. The SINTAP (European Structural Integrity Assessment Procedure) was used for this assessment. 相似文献