全文获取类型
收费全文 | 173215篇 |
免费 | 25014篇 |
国内免费 | 6696篇 |
专业分类
电工技术 | 9822篇 |
技术理论 | 8篇 |
综合类 | 9583篇 |
化学工业 | 38298篇 |
金属工艺 | 8474篇 |
机械仪表 | 9479篇 |
建筑科学 | 13028篇 |
矿业工程 | 4356篇 |
能源动力 | 4580篇 |
轻工业 | 16017篇 |
水利工程 | 3138篇 |
石油天然气 | 7343篇 |
武器工业 | 1355篇 |
无线电 | 21699篇 |
一般工业技术 | 26109篇 |
冶金工业 | 7122篇 |
原子能技术 | 1633篇 |
自动化技术 | 22881篇 |
出版年
2024年 | 650篇 |
2023年 | 2431篇 |
2022年 | 4500篇 |
2021年 | 6265篇 |
2020年 | 5959篇 |
2019年 | 6686篇 |
2018年 | 7129篇 |
2017年 | 8152篇 |
2016年 | 7871篇 |
2015年 | 9589篇 |
2014年 | 10871篇 |
2013年 | 13214篇 |
2012年 | 11977篇 |
2011年 | 12023篇 |
2010年 | 10929篇 |
2009年 | 10281篇 |
2008年 | 9654篇 |
2007年 | 8968篇 |
2006年 | 8568篇 |
2005年 | 7341篇 |
2004年 | 5553篇 |
2003年 | 5115篇 |
2002年 | 5111篇 |
2001年 | 4370篇 |
2000年 | 4044篇 |
1999年 | 3577篇 |
1998年 | 2510篇 |
1997年 | 2089篇 |
1996年 | 2059篇 |
1995年 | 1676篇 |
1994年 | 1381篇 |
1993年 | 991篇 |
1992年 | 798篇 |
1991年 | 630篇 |
1990年 | 461篇 |
1989年 | 383篇 |
1988年 | 304篇 |
1987年 | 211篇 |
1986年 | 158篇 |
1985年 | 107篇 |
1984年 | 68篇 |
1983年 | 53篇 |
1982年 | 52篇 |
1981年 | 50篇 |
1980年 | 39篇 |
1979年 | 20篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1973年 | 6篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
The RPE (recursive prediction error) method in state-space form is developed in the nonlinear systems and extended to include the exact form of a nonlinearity, thus enabling structure preservation for certain classes of nonlinear systems. Both the discrete and the continuous-discrete versions of the algorithm in an innovations model are investigated, and a nonlinear simulation example shows a quite convincing performance of the filter as combined parameter and state estimator 相似文献
63.
利用引进的制造技术和设备,制作出了 APT(STLRI)—1.78型系列化光纤连接器。 相似文献
64.
65.
66.
67.
In this paper, two brittle fracture problems are numerically simulated: the failure of a ceramic ring under centrifugal loading and crack branching in a PMMA strip. A three‐dimensional finite element package in which cohesive elements are dynamically inserted has been developed. The cohesive elements' strength is chosen to follow a modified weakest link Weibull distribution. The probability of introducing a weak cohesive element is set to increase with the cohesive element size. This reflects the physically based effect according to which larger elements are more likely to contain defects. The calculations illustrate how the area dependence of the Weibull model can be used to effectively address mesh dependency. On the other hand, regular Weibull distributions have failed to reduce mesh dependency for the examples shown in this paper. The ceramic ring calculations revealed that two distinct phenomena appear depending on the magnitude of the Weibull modulus. For low Weibull modulus, the fragmentation of the ring is dominated by heterogeneities. Whereas many cracks were generated, few of them could propagate to the outer surface. Monte Carlo simulations revealed that for highly heterogeneous rings, the number of small fragments was large and that few large fragments were generated. For high Weibull modulus, signifying that the ring is close to being homogeneous, the fragmentation process was very different. Monte Carlo simulations highlighted that a larger number of large fragments are generated due to crack branching. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
68.
69.
本文提出了强扩散准则,强雪崩效应以及扩散效应的逼近优势等相关概念,给出了差分均匀性与强k阶扩散准则之间的相互关系,利用给出的设计准则改进了Rijndael密码的S盒。 相似文献
70.
Gonzalo Martínez‐Barrera Enrique Vigueras‐Santiago Susana Hernndez‐Lpez Gonzalo Martínez‐Barrera Witold Brostow Carmina Menchaca‐Campos 《Polymer Engineering and Science》2005,45(10):1426-1431
Fiber reinforced concrete (FRC) contains fibers physically mixed with gravel, sand, cement, and water. So far, adequate mechanical performance of FRC has been obtained at high cost and using complex technologies; important here is the geometry and surface characteristics of the polymers. We have modified polymeric‐fiber surfaces by using gamma radiation. Irradiated polypropylene (PP) fibers were submitted to 0, 5, 10, 50, and 100 kGy of gamma irradiation dosages. First, tensile strength of PP fibers was evaluated, and then fibers blended at 0, 1.0, 1.5, and 2.0% in volume with Portland cement, gravel, sand, and water. The highest values of compressive strength were obtained with irradiated‐fibers at 10 kGy and 1.5% in volume of fiber. The result is 101 MPa, as compared to 35 MPa for simple concrete without fibers. POLYM. ENG. SCI., 45:1426–1431, 2005. © 2005 Society of Plastics Engineers 相似文献