全文获取类型
收费全文 | 40088篇 |
免费 | 3650篇 |
国内免费 | 2111篇 |
学科分类
工业技术 | 45849篇 |
出版年
2024年 | 131篇 |
2023年 | 530篇 |
2022年 | 831篇 |
2021年 | 1143篇 |
2020年 | 1180篇 |
2019年 | 1037篇 |
2018年 | 1008篇 |
2017年 | 1245篇 |
2016年 | 1497篇 |
2015年 | 1648篇 |
2014年 | 2424篇 |
2013年 | 2574篇 |
2012年 | 2420篇 |
2011年 | 3312篇 |
2010年 | 2202篇 |
2009年 | 2446篇 |
2008年 | 2369篇 |
2007年 | 2823篇 |
2006年 | 2391篇 |
2005年 | 2186篇 |
2004年 | 1859篇 |
2003年 | 1668篇 |
2002年 | 1348篇 |
2001年 | 1081篇 |
2000年 | 945篇 |
1999年 | 704篇 |
1998年 | 577篇 |
1997年 | 436篇 |
1996年 | 349篇 |
1995年 | 297篇 |
1994年 | 273篇 |
1993年 | 199篇 |
1992年 | 167篇 |
1991年 | 134篇 |
1990年 | 96篇 |
1989年 | 77篇 |
1988年 | 50篇 |
1987年 | 29篇 |
1986年 | 29篇 |
1985年 | 26篇 |
1984年 | 27篇 |
1983年 | 9篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 10篇 |
1975年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
番禺30-1砂岩强水驱气藏储层非均质性研究 总被引:7,自引:5,他引:2
针对垂向非均质性严重且边底水能量强的番禺30-1气田面临的潜在开发问题,通过岩心分析及测井二次解释,对其夹层特征及储层非均质性等进行了研究,划分出19个流动单元并定量描述了各流动单元的特征参数,建立了该气田的精细地质模型。综合评价表明,新建的地质模型具有较高的精度,为该气藏合理开发提供了坚实的地质基础。 相似文献
4.
5.
6.
7.
This article, the first of three articles on the synthesis of rice processing plants, focuses on the development of simplified mathematical models necessary for use in optimizing rice processing plants. The second concentrates on the optimal synthesis of a rice plant and the third on the sensitivity of the optimization to uncertainty in model parameters. Existing models for rice processing unit operations are not suitable for flowsheet optimization and new models need to be developed to overcome numerical difficulties that occur in optimization applications, specifically in mixed integer nonlinear programming (MINLP) applications. Simplified models of the drying, cooling, and tempering units are developed. In addition head rice yield models, used as a quality indicator, energy consumption, and economic models were also developed. Naturally, the new models exhibit some mismatch with respect to the existing models from which they were developed. However, a sensitivity analysis, presented in Part III, has shown that the optimal flowsheet structure was not sensitive to a lack of fit between the simplified and complex models. The simplified models were found adequate to be appropriate for use at the synthesis stage. 相似文献
8.
9.
10.
A stochastic model for local disturbances, particularly for a temporal harmonic with random modulations in amplitude and/or phase, is proposed in this paper. Results for the second moment responses of a linear single-degree-of-freedom system to this type of stochastic loading demonstrate a significant change in response characteristics due to a small uncertainty. A local phenomenon may last much longer and resonance may be smeared to a broad range. Integrated with wavelet transform, the proposed approach may be used to model a random process with non-stationary frequency content. Especially, it can be effectively used for Monte Carlo simulation to generate large size of samples that have similar characteristics in time and frequency domains as a pre-selected mother sample has. The technique has a great potential for the case where uncertainty study is warranted but the available samples are limited. 相似文献