全文获取类型
收费全文 | 24340篇 |
免费 | 2455篇 |
国内免费 | 1715篇 |
专业分类
电工技术 | 1130篇 |
综合类 | 3681篇 |
化学工业 | 4814篇 |
金属工艺 | 2303篇 |
机械仪表 | 1221篇 |
建筑科学 | 1421篇 |
矿业工程 | 686篇 |
能源动力 | 809篇 |
轻工业 | 1020篇 |
水利工程 | 548篇 |
石油天然气 | 1031篇 |
武器工业 | 168篇 |
无线电 | 1547篇 |
一般工业技术 | 3596篇 |
冶金工业 | 1382篇 |
原子能技术 | 274篇 |
自动化技术 | 2879篇 |
出版年
2024年 | 78篇 |
2023年 | 277篇 |
2022年 | 441篇 |
2021年 | 630篇 |
2020年 | 671篇 |
2019年 | 678篇 |
2018年 | 599篇 |
2017年 | 771篇 |
2016年 | 876篇 |
2015年 | 822篇 |
2014年 | 1317篇 |
2013年 | 1511篇 |
2012年 | 1770篇 |
2011年 | 1770篇 |
2010年 | 1303篇 |
2009年 | 1405篇 |
2008年 | 1363篇 |
2007年 | 1562篇 |
2006年 | 1497篇 |
2005年 | 1339篇 |
2004年 | 1131篇 |
2003年 | 1049篇 |
2002年 | 848篇 |
2001年 | 705篇 |
2000年 | 653篇 |
1999年 | 540篇 |
1998年 | 428篇 |
1997年 | 401篇 |
1996年 | 351篇 |
1995年 | 313篇 |
1994年 | 299篇 |
1993年 | 212篇 |
1992年 | 190篇 |
1991年 | 167篇 |
1990年 | 135篇 |
1989年 | 117篇 |
1988年 | 87篇 |
1987年 | 52篇 |
1986年 | 23篇 |
1985年 | 23篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1959年 | 3篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Stephen J. Spells 《Polymer》1985,26(13):1921-1928
The chain conformation of solution-crystallized polyethylene has previously been confirmed by infra-red spectroscopy, using the CD2 bending bandshape for samples with a minority of the deuterated species1–3. The method of calculating the i.r. band profile from molecular conformational models is now developed to give a more accurate representation of doublet splittings and to include the singlet component. The CH2 bending profile is calculated for samples with a deuterated matrix, and the good agreement with experimental data indicates that the same molecular model is applicable for samples with the deuterated polymer as either guest or matrix, for identical crystallization conditions. This result implies that isotopic fractionation is unimportant under these conditions. 相似文献
62.
叠前地震数据的规则化 总被引:6,自引:1,他引:5
本文通过对动校正前积分法DMO原理的探讨,在借鉴Canning(1996)提出的利用DMO实现三维数据规则化的方法和Biondi(1998)提出的三维叠前地震数据方位角校正方法的基础上,从方位角校正的角度入手,利用DMO和DMO^-1相结合的处理流程对地震数据进行规则化,以得到新的规则的观测系统下具有所需特定方位角的观测数据。此方法可用于解决叠前地震数据道插值、陆上地震勘探中不规则观测数据的规则化和海上地震勘探中的羽状现象校正等问题,可将已有地震观测数据转变为特定观测系统的叠前地震数据,以便于某些处理方法的应用。此方法原理简单并具有广泛的适用性。 相似文献
63.
64.
65.
Shu-Chu Ren Nelson N. Hsu Donald G. Eitzen 《Journal of research of the National Institute of Standards and Technology》2002,107(5):445-473
Pulsed ultrasonic techniques can be and have been used to examine the interface conditions of a bonded structure. To provide a theoretical basis for such testing techniques we model the structure as a layer on top of a half-space, both of different elastic properties, with various interface bonding conditions. The exact dynamic Green’s tensor for such a structure is explicitly derived from the three-dimensional equations of motion. The final solution is a series. Each term of the series corresponds to a successive arrival of a “generalized ray” and each is a definite line integral along a fixed path which can be easily computed numerically. Willis’ method is used in the derivation. A new scheme of automatic generation of the arrivals and ray paths using combinatorial analysis, along with the summation of the corresponding products of reflection coefficients is presented. A FORTRAN code is developed for computation of the Green’s tensor when both the source and the detector are located on the top surface. The Green’s tensor is then used to simulate displacements due to pulsed ultrasonic point sources of known time waveform. Results show that the interface bonding conditions have a great influence on the transient displacements. For example, when the interface bonding conditions vary, some of the first few head waves and regular reflected rays change polarities and amplitudes. This phenomenon can be used to infer the quality of the interface bond of materials in ultrasonic nondestructive evaluation. In addition the results are useful in the study of acoustic microscopy probes, coatings, and geo-exploration. 相似文献
66.
求得了带有集中质量的分布质量弹性转轴系统横向自由振动的频率方程和振型函数的精确解析表达式,及其与不转动轴系统自由振动的频率方程和振型函数及转动角速度之间的精确解析关系 相似文献
67.
通过电化学极化曲线和失重实验,研究了氨荒酸盐对铜在氯化钠溶液中的缓蚀性能,并与相应胺的缓蚀性能进行了对比。结果表明:氨荒酸盐对铜具有较好的缓蚀性能。 相似文献
68.
TRT入口方管道爆裂原因剖析 总被引:1,自引:0,他引:1
介绍了鞍钢7#高炉TRT装置入口方管道爆裂事故经过,进行了原因分析,并提出了解决措施。 相似文献
69.
M. Portillo
J. H. Dohr
《Design Studies》1994,15(4):403-416Scholars in design face two central challenges in design methods inquiry: firstly, to integrate process and solution, and secondly, to examine developmental junctures leading to innovation. With these goals in mind, we maintain that design criteria deserve greater attention and illustrate this position with a study of noted designers' use of criteria. The primary finding was that five criteria functions were considered during the design process. The study also explored potential relationships between designer variables (i.e., professional expertise and personality type) and criteria use. 相似文献
70.
何明一 《电子科学学刊(英文版)》1994,11(1):1-10
A new concept, the generalized inverse group (GIG) of signal, is firstly proposed and its properties, leaking coefficients and implementation with neural networks are presented. Theoretical analysis and computational simulation have shown that (1) there is a group of finite length of generalized inverse signals for any given finite signal, which forms the GIG; (2) each inverse group has different leaking coefficients, thus different abnormal states; (3) each GIG can be implemented by a grouped and improved single-layer perceptron which appears with fast convergence. When used in deconvolution, the proposed GIG can form a new parallel finite length of filtering deconvolution method. On off-line processing, the computational time is reduced to O(N) from O(N2). And the less the leaking coefficient is, the more reliable the deconvolution will be. 相似文献