全文获取类型
收费全文 | 287494篇 |
免费 | 3379篇 |
国内免费 | 963篇 |
专业分类
电工技术 | 4260篇 |
综合类 | 2453篇 |
化学工业 | 42733篇 |
金属工艺 | 14934篇 |
机械仪表 | 9979篇 |
建筑科学 | 6124篇 |
矿业工程 | 2714篇 |
能源动力 | 5711篇 |
轻工业 | 16369篇 |
水利工程 | 4147篇 |
石油天然气 | 8053篇 |
武器工业 | 22篇 |
无线电 | 30554篇 |
一般工业技术 | 60854篇 |
冶金工业 | 36898篇 |
原子能技术 | 6863篇 |
自动化技术 | 39168篇 |
出版年
2021年 | 2044篇 |
2019年 | 2000篇 |
2018年 | 17867篇 |
2017年 | 16826篇 |
2016年 | 13788篇 |
2015年 | 2817篇 |
2014年 | 3989篇 |
2013年 | 8910篇 |
2012年 | 8735篇 |
2011年 | 16402篇 |
2010年 | 13958篇 |
2009年 | 11909篇 |
2008年 | 13241篇 |
2007年 | 14087篇 |
2006年 | 5676篇 |
2005年 | 6276篇 |
2004年 | 5712篇 |
2003年 | 5683篇 |
2002年 | 4888篇 |
2001年 | 4560篇 |
2000年 | 4352篇 |
1999年 | 4250篇 |
1998年 | 10232篇 |
1997年 | 7206篇 |
1996年 | 5538篇 |
1995年 | 4139篇 |
1994年 | 3607篇 |
1993年 | 3846篇 |
1992年 | 2995篇 |
1991年 | 3017篇 |
1990年 | 2890篇 |
1989年 | 2852篇 |
1988年 | 2874篇 |
1987年 | 2508篇 |
1986年 | 2568篇 |
1985年 | 2854篇 |
1984年 | 2687篇 |
1983年 | 2554篇 |
1982年 | 2300篇 |
1981年 | 2269篇 |
1980年 | 2345篇 |
1979年 | 2359篇 |
1978年 | 2382篇 |
1977年 | 2487篇 |
1976年 | 2876篇 |
1975年 | 2188篇 |
1974年 | 2068篇 |
1973年 | 2166篇 |
1972年 | 1940篇 |
1971年 | 1755篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
111.
O.N. Kondrateva G.E. Nikiforova A.V. Tyurin M.A. Ryumin V.M. Gurevich A.P. Kritskaya K.S. Gavrichev 《Ceramics International》2018,44(15):18103-18107
The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO4 was compared with the data known for YbPO4. 相似文献
112.
113.
T. Galvin N.C. Hyatt W.M. Rainforth I.M. Reaney D. Shepherd 《Journal of the European Ceramic Society》2018,38(14):4585-4589
The molten salt method was used to synthesise the MAX phase compounds Ti2AlC and Ti3AlC2 from elemental powders. Between 900–1000?°C, Ti2AlC was formed alongside ancillary phases TiC and TiAl, which decreased in abundance with increasing synthesis temperature. Changing the stoichiometry and increasing the synthesis temperature to 1300?°C resulted in formation of Ti3AlC2 alongside Ti2AlC and TiC. The type of salt flux used had little effect on the product formation. The reaction pathway for Ti2AlC was determined to be the initial formation of TiC1-x templating on the graphite and titanium aluminides. 相似文献
114.
115.
Radiochemistry - Reaction of solid-phase catalytic heterogeneous isotope exchange of 2-deoxy-D-glucose and its derivative, O(6)-(4-bromothiophenyl)guanine-C8-β-D-glucose with tritium has been... 相似文献
116.
117.
Programming and Computer Software - Modern computer systems often include specialized processors that are programmed in domain-specific languages. The compiler-in-the-loop technology, which assumes... 相似文献
118.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts. 相似文献
119.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding. 相似文献
120.
This study addresses the thermo‐diffusion and the diffusion‐thermo phenomena in a semi‐infinite absorbent channel whose walls are contracting/expanding, with heat source/sink effects. The governing partial differential equations with suitable boundary conditions are transformed to a system of dimensionless ordinary differential equations. An analytic solution of the problem has been found using a technique called homotopy analysis method (HAM). HAM gives consistently valid answers to the problem over an extensive variety of parameters and also provides better accuracy. To validate the analytical results, a comparison has been presented with a numerical solution calculated by using the parallel shooting method. The effects of dimensionless parameters, that is, deformation parameter, Reynolds number, Soret and Dufour numbers, and heat source/sink parameter on the expressions of velocity, temperature, and concentration profiles are analyzed graphically to understand the physics of the deformable channel. It has been noted that the velocity across the channel is higher for the expanding channel, as compared to that for the contracting channel. Also the Soret and Dufour number increases the temperature of the fluid, and decreases the concentration. The temperature profile has an increasing behavior in the case of heat source, and a decreasing behavior in the case of heat sink. 相似文献