全文获取类型
收费全文 | 501416篇 |
免费 | 5842篇 |
国内免费 | 1840篇 |
专业分类
电工技术 | 9013篇 |
综合类 | 732篇 |
化学工业 | 71545篇 |
金属工艺 | 23215篇 |
机械仪表 | 17730篇 |
建筑科学 | 11748篇 |
矿业工程 | 3252篇 |
能源动力 | 11801篇 |
轻工业 | 37447篇 |
水利工程 | 5811篇 |
石油天然气 | 10152篇 |
武器工业 | 49篇 |
无线电 | 57396篇 |
一般工业技术 | 103866篇 |
冶金工业 | 86641篇 |
原子能技术 | 12049篇 |
自动化技术 | 46651篇 |
出版年
2021年 | 3459篇 |
2019年 | 3341篇 |
2018年 | 12628篇 |
2017年 | 13088篇 |
2016年 | 10026篇 |
2015年 | 4414篇 |
2014年 | 6937篇 |
2013年 | 19520篇 |
2012年 | 13270篇 |
2011年 | 22248篇 |
2010年 | 18690篇 |
2009年 | 19484篇 |
2008年 | 19707篇 |
2007年 | 21392篇 |
2006年 | 12435篇 |
2005年 | 14363篇 |
2004年 | 12814篇 |
2003年 | 12240篇 |
2002年 | 10949篇 |
2001年 | 10655篇 |
2000年 | 10309篇 |
1999年 | 10581篇 |
1998年 | 25590篇 |
1997年 | 18217篇 |
1996年 | 14189篇 |
1995年 | 10661篇 |
1994年 | 9592篇 |
1993年 | 9470篇 |
1992年 | 7068篇 |
1991年 | 6782篇 |
1990年 | 6451篇 |
1989年 | 6529篇 |
1988年 | 6092篇 |
1987年 | 5395篇 |
1986年 | 5311篇 |
1985年 | 6016篇 |
1984年 | 5535篇 |
1983年 | 5166篇 |
1982年 | 4742篇 |
1981年 | 4827篇 |
1980年 | 4737篇 |
1979年 | 4611篇 |
1978年 | 4633篇 |
1977年 | 5154篇 |
1976年 | 6839篇 |
1975年 | 3944篇 |
1974年 | 3830篇 |
1973年 | 3847篇 |
1972年 | 3204篇 |
1971年 | 2898篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
131.
Kazantsev Yu. N. Kraftmakher G. A. Mal’tsev V. P. 《Journal of Communications Technology and Electronics》2019,64(6):550-554
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice... 相似文献
132.
Lingfeng Zhou Zhipeng Zeng Michael P. Brady Donovan N. Leonard Harry M. Meyer Yukinori Yamamoto Wenyuan Li Greg Collins Xingbo Liu 《International Journal of Hydrogen Energy》2021,46(41):21619-21633
The chromium (Cr) evaporation behavior of several different types of iron (Fe)-based AFA alloys and benchmark Cr2O3-forming Fe-based 310 and Ni-based 625 alloys was investigated for 500 h exposures at 800 °C to 900 °C in air with 10% H2O. The Cr evaporation rates from alumina-forming austenitic (AFA) alloys were ~5 to 35 times lower than that of the Cr2O3-forming alloys depending on alloy and temperature. The Cr evaporation behavior was correlated with extensive characterization of the chemistry and microstructure of the oxide scales, which also revealed a degree of quartz tube Si contamination during the test. Long-term oxidation kinetics were also assessed at 800 to 1000 °C for up to 10,000 h in air with 10% H2O to provide further guidance for SOFC BOP component alloy selection. 相似文献
133.
Mining high utility itemsets (HUIs) from transaction databases considers such factors as the unit profit and quantity of purchased items. Two-phase tree-based algorithms transform a database into compressed tree structures and generate candidate patterns through a recursive pattern-growth procedure. This procedure requires a lot of memory and time to construct conditional pattern trees. To address this issue, this study employs two compressed tree structures, namely, Utility Count Tree and String Utility Tree, to enumerate valid patterns and thus promote fast utility computation. Furthermore, the study presents an algorithm called single-phase utility computation (SPUC) that leverages these two tree structures to mine HUIs in a single phase by incorporating novel pruning strategies. Experiments conducted on both real and synthetic datasets demonstrate the superior performance of SPUC compared with IHUP, UP-Growth, and UP-Growth+ algorithms. 相似文献
134.
Chertkov Yu. B. Anikin M. N. Lebedev I. I. Naimushin A. G. Smol’nikov N. V. 《Atomic Energy》2021,131(1):42-45
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with... 相似文献
135.
ABSTRACTGiven that online platforms disrupt established industries and challenge existing institutions, they can only be successful if their innovation becomes both legal and legitimate. This requires ‘institutional work’ that changes perceptions and regulations within society. Rather than only focussing on the online platform as the sole agent engaging in institutional work, our study analyses institutional work as a collective process. We investigate the case of home-sharing platform Airbnb and the process of institutional change its introduction prompted regarding short-term rental in Amsterdam, London and New York. We find, contrary to the popular view of online platforms as disruptive entrepreneurs, that the platform mainly focusses on creating new institutions rather than disrupting existing ones, and that users and non-users undertake most of the institutional work activities. We also show that different types of actors carry out different types of institutional work suggesting that the process of institutional work is highly distributed. 相似文献
136.
D.R. Santos‐Peñate C.M. Campos‐Rodríguez J.A. Moreno‐Pérez 《International Transactions in Operational Research》2019,26(1):340-363
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included. 相似文献
137.
Myriam Gonzlez María Ovejero-Snchez Alba Vicente-Blzquez Raquel lvarez Ana B. Herrero Manuel Medarde Rogelio Gonzlez-Sarmiento Rafael Pelez 《International journal of molecular sciences》2021,22(4)
Pan-Gyn cancers entail 1 in 5 cancer cases worldwide, breast cancer being the most commonly diagnosed and responsible for most cancer deaths in women. The high incidence and mortality of these malignancies, together with the handicaps of taxanes—first-line treatments—turn the development of alternative therapeutics into an urgency. Taxanes exhibit low water solubility that require formulations that involve side effects. These drugs are often associated with dose-limiting toxicities and with the appearance of multi-drug resistance (MDR). Here, we propose targeting tubulin with compounds directed to the colchicine site, as their smaller size offer pharmacokinetic advantages and make them less prone to MDR efflux. We have prepared 52 new Microtubule Destabilizing Sulfonamides (MDS) that mostly avoid MDR-mediated resistance and with improved aqueous solubility. The most potent compounds, N-methyl-N-(3,4,5-trimethoxyphenyl-4-methylaminobenzenesulfonamide 38, N-methyl-N-(3,4,5-trimethoxyphenyl-4-methoxy-3-aminobenzenesulfonamide 42, and N-benzyl-N-(3,4,5-trimethoxyphenyl-4-methoxy-3-aminobenzenesulfonamide 45 show nanomolar antiproliferative potencies against ovarian, breast, and cervix carcinoma cells, similar or even better than paclitaxel. Compounds behave as tubulin-binding agents, causing an evident disruption of the microtubule network, in vitro Tubulin Polymerization Inhibition (TPI), and mitotic catastrophe followed by apoptosis. Our results suggest that these novel MDS may be promising alternatives to taxane-based chemotherapy in chemoresistant Pan-Gyn cancers. 相似文献
138.
139.
Daniela Frasca Maria Romero Alain Diaz Denisse Garcia Seth Thaller Bonnie B. Blomberg 《International journal of molecular sciences》2021,22(4)
Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation. 相似文献
140.
Wei LingNan Wang ZhenHua Zhang ZhiDong Liu Chieh-Wen Gao Xuan P. A. 《Nano Research》2020,13(5):1332-1338
Nano Research - We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition (CVD). It is... 相似文献