全文获取类型
收费全文 | 33160篇 |
免费 | 2730篇 |
国内免费 | 1674篇 |
专业分类
电工技术 | 2715篇 |
综合类 | 4091篇 |
化学工业 | 3387篇 |
金属工艺 | 1261篇 |
机械仪表 | 2890篇 |
建筑科学 | 4330篇 |
矿业工程 | 1907篇 |
能源动力 | 1141篇 |
轻工业 | 1865篇 |
水利工程 | 1398篇 |
石油天然气 | 1845篇 |
武器工业 | 352篇 |
无线电 | 1913篇 |
一般工业技术 | 2351篇 |
冶金工业 | 1736篇 |
原子能技术 | 195篇 |
自动化技术 | 4187篇 |
出版年
2024年 | 117篇 |
2023年 | 323篇 |
2022年 | 639篇 |
2021年 | 815篇 |
2020年 | 889篇 |
2019年 | 679篇 |
2018年 | 660篇 |
2017年 | 858篇 |
2016年 | 1004篇 |
2015年 | 1038篇 |
2014年 | 2019篇 |
2013年 | 1736篇 |
2012年 | 2384篇 |
2011年 | 2610篇 |
2010年 | 2090篇 |
2009年 | 2179篇 |
2008年 | 1999篇 |
2007年 | 2381篇 |
2006年 | 2128篇 |
2005年 | 1857篇 |
2004年 | 1539篇 |
2003年 | 1393篇 |
2002年 | 1171篇 |
2001年 | 1022篇 |
2000年 | 835篇 |
1999年 | 619篇 |
1998年 | 470篇 |
1997年 | 411篇 |
1996年 | 311篇 |
1995年 | 279篇 |
1994年 | 235篇 |
1993年 | 156篇 |
1992年 | 142篇 |
1991年 | 127篇 |
1990年 | 99篇 |
1989年 | 98篇 |
1988年 | 64篇 |
1987年 | 38篇 |
1986年 | 31篇 |
1985年 | 16篇 |
1984年 | 20篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1977年 | 4篇 |
1964年 | 6篇 |
1960年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
71.
72.
Shang-Ching Chou 《Journal of Automated Reasoning》1988,4(3):237-267
Wu's algebraic method for mechanically proving geometry theorems is presented at a level as elementary as possible with sufficient examples for further understanding the complete method.The work reported here was supported by NSF Grant DCR-8503498. 相似文献
73.
本文研究了加法复合布尔函数和乘法复合布尔函数,在平衡性、k次项系数、K次扩散准则(PC)、相关免疫 性(CI)、Walsh谱、代数次数、小项分布等方面得到了一批新结果。 相似文献
74.
乌江索风营水电站坝址区分布有7个堆积体,其成因有崩塌堆积、蠕变-拉裂-崩解堆积、塌滑堆积及混和堆积等.在勘察过程中采用了地质测绘、钻探、硐探、物探、科研试验等多种勘察方法与手段,在勘察成果基础上对堆积体稳定性进行了分析,并结合对工程的不同影响提出了相应的工程处理措施. 相似文献
75.
76.
77.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(8):787
Provides the biography of Cortney S. Warren and announces that she has received the APA Psi Chi/APA Edwin B. Newman Graduate Research Award (2004) for an outstanding research paper whose findings examine the potential for ethnicity to protect against body image disturbance by moderating the relationships between awareness and internalization of a thin physical ideal and body dissatisfaction. A selected bibliography is also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
79.
In general, this paper deals with general nonlinear oscillations of a nonconservative and single degree-of-freedom system with odd nonlinearity and, in particular, it presents accurate higher-order analytical approximate solutions to van der Pol damped nonlinear oscillators having odd nonlinearity and the Rayleigh equation. By combining the linearization of the governing equation with harmonic balancing and the method of averaging, we establish accurate analytical approximate solutions for the general weakly damped nonlinear systems. Unlike the classical harmonic balance method, simple linear algebraic equations instead of nonlinear algebraic equations are obtained upon linearization prior to harmonic balancing. The combination of these two methods results in very accurate transient response of the periodic solution. In addition and for the first time, this paper also presents a method for deducing fourth-, fifth- and higher-order linearized governing equations from the lower-order equations without the requirement of formulating the problem from the first principle. Three examples including the van der Pol damped nonlinear oscillator are presented to illustrate the excellent agreement with approximate solution using the exact frequency. 相似文献
80.
A new discretization method for aggregation equations is developed. It is compared to the fixed pivot technique proposed by Kumar and Ramkrishna (1996a. On the solution of population balance equations by discretization—I. A fixed pivot technique. Chemical Engineering Science 51, 1311-1332). The numerical results for aggregation problems by discretized population balances are consistently overpredicting and diverge before the gelling point in the case of a gelling kernel. The present work establishes a new technique which assigns the particles within the cells more precisely. This is achieved by taking first the average of the newborn particles within the cell and then assigning them to the neighboring nodes such that pre-chosen properties are exactly preserved. The new technique preserves all the advantages of the conventional discretized methods and provides a significant improvement in predicting the particle size distribution (PSD). In addition, it is found that the technique is a powerful tool for the computation of gelling problems. The effectiveness of the technique is illustrated by application to several aggregation problems for suitably selected aggregation kernels including physically relevant kernels. 相似文献