全文获取类型
收费全文 | 89545篇 |
免费 | 6865篇 |
国内免费 | 3477篇 |
专业分类
电工技术 | 4970篇 |
技术理论 | 5篇 |
综合类 | 5729篇 |
化学工业 | 15737篇 |
金属工艺 | 5435篇 |
机械仪表 | 5496篇 |
建筑科学 | 7868篇 |
矿业工程 | 2583篇 |
能源动力 | 2378篇 |
轻工业 | 5366篇 |
水利工程 | 1573篇 |
石油天然气 | 5280篇 |
武器工业 | 683篇 |
无线电 | 9351篇 |
一般工业技术 | 10643篇 |
冶金工业 | 4516篇 |
原子能技术 | 1068篇 |
自动化技术 | 11206篇 |
出版年
2024年 | 361篇 |
2023年 | 1497篇 |
2022年 | 2430篇 |
2021年 | 3380篇 |
2020年 | 2627篇 |
2019年 | 2188篇 |
2018年 | 2543篇 |
2017年 | 2881篇 |
2016年 | 2458篇 |
2015年 | 3268篇 |
2014年 | 4137篇 |
2013年 | 5075篇 |
2012年 | 5556篇 |
2011年 | 5933篇 |
2010年 | 5038篇 |
2009年 | 4977篇 |
2008年 | 4770篇 |
2007年 | 4586篇 |
2006年 | 4894篇 |
2005年 | 4350篇 |
2004年 | 2907篇 |
2003年 | 2505篇 |
2002年 | 2303篇 |
2001年 | 2026篇 |
2000年 | 2303篇 |
1999年 | 2687篇 |
1998年 | 2185篇 |
1997年 | 1778篇 |
1996年 | 1825篇 |
1995年 | 1489篇 |
1994年 | 1212篇 |
1993年 | 860篇 |
1992年 | 701篇 |
1991年 | 556篇 |
1990年 | 404篇 |
1989年 | 332篇 |
1988年 | 270篇 |
1987年 | 184篇 |
1986年 | 123篇 |
1985年 | 88篇 |
1984年 | 57篇 |
1983年 | 36篇 |
1982年 | 40篇 |
1981年 | 34篇 |
1980年 | 23篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
51.
A novel monomer containing pyridylazo-2-naphthoxyl group, 1-(1-(4-vinylbenzyloxy)naphthalen-2-yl)-2-(pyridin-2-yl)diazene (VBNPA), was successfully synthesized and copolymerized with styrene (St) in N,N-dimethyl formamide (DMF) via reversible addition–fragmentation chain transfer (RAFT) polymerization using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as RAFT agent. The polymerization behavior exhibited “living”/controlled characters. The obtained copolymer, poly(St-co-VBNPA), with pre-determinable molecular weight and narrow molecular weight distribution can be used as a carrier in metal ion detection and analysis via pre-concentration technique. The copolymer–metal ion (copper (Cu) and europium (Eu)) complexes were prepared and characterized. 相似文献
52.
53.
54.
An analytical method is presented for calculating the resonant frequency andQ-factor of a superconducting dielectric disk resonator operating in millimeter-wave regime with whispering-gallery mode. Resonant frequency shift due to the optical generation of quasi-particles in superconducting film is investigated as a function of photon flux. An optically tunable resonant frequency of about 500 MHz is estimated, and good agreement is found between numerical results and experimental ones. 相似文献
55.
PURPOSE: The purpose of this research is to obtain the tablet coating distribution from weight distributions of uncoated and coated tablets. METHODS: The method of deconvolution with digital smoothing was used to calculate the distribution of coating applied to a tablet population from separate random measurements of individual uncoated and coated tablets. RESULTS: It was demonstrated that the calculated coating weight distribution agrees well with the measured distribution. The effect of the smoothing factor on the solution is illustrated. CONCLUSIONS: This method can be used during development to facilitate process scale-up/optimization. In routine production, the method can assess the reproducibility and consistency of a coating process. 相似文献
56.
Conventional drying, dehumidification drying, and combined conventional-dehumidification drying of wood were experimentally studied in this article. The results showed that the energy consumption in the dehumidification drying is the least but its drying time is the longest. The energy consumption in the combined drying is more than that in the dehumidification drying but less than that in the conventional drying, and the drying time is half of that in the dehumidification drying. The advantages of the combined conventional and dehumidification drying are discussed from the experiments results. 相似文献
57.
58.
Two experimental devices were designed and built to determine four coefficients KT KM DM D (or δT = DT / DM occurring in simultaneous heat and mass transfer equations, where,K T and DM are thermal conductivity and moisture diffcusivity respectively, DT ( or δ T is temperature gradient Induced moisture migration coefficient and KM is moisture gradient Induced heat transfer coefficient. Three food materials, i.e. potato, bread dough and bread, were tested. From this study, it was found that the value of 5 was higher for low density food materials, such as bread, than for high density materials, such as potato. The coefficient & measures moisture migration contribution due to temperature gradient within the material. The average values of δ T for potato, bread dough and bread were 0.0014, 0.0059 and 0.0127 per °C, respectively. The contribution of temperature gradient to the overall moisture migration is negligible In high density materials. However, this contribution may be important in the moisture migratlon analysls for low density materials. The moisture gradient induced heat transfer coefficient % as found to be negligible for the materials tested in this study 相似文献
59.
To investigate the prognostic factors of primary liver cancer (PLC) and improve the long-term results, 1,248 cases of PLC were analysed. Univariate analysis demonstrated that discovery approach, staging of PLC, original gamma-GPT, resection, radical resection, original AFP, tumor size, tumor number, and tumor capsule have very significant effects on prognosis of PLC (all P < 0.001); cirrhosis, HBsAg, local resection, and tumor embolus in portal vein were also significant difference (all P < 0.05); age, sex, original AFP, hepatitis, and differentiation of PLC cells were no significant difference (all P > 0.05). Multivariate analysis demonstrated that original gamma-GPT, radical resection, tumor size, and tumor number were the most significant prognostic factors (all P < 0.001). Some aspects improving long-term survival were discussed. 相似文献
60.