全文获取类型
收费全文 | 71032篇 |
免费 | 8295篇 |
国内免费 | 5930篇 |
专业分类
电工技术 | 5482篇 |
技术理论 | 4篇 |
综合类 | 6196篇 |
化学工业 | 13433篇 |
金属工艺 | 2654篇 |
机械仪表 | 6602篇 |
建筑科学 | 5161篇 |
矿业工程 | 2373篇 |
能源动力 | 6071篇 |
轻工业 | 5343篇 |
水利工程 | 5843篇 |
石油天然气 | 4480篇 |
武器工业 | 736篇 |
无线电 | 2417篇 |
一般工业技术 | 6130篇 |
冶金工业 | 3690篇 |
原子能技术 | 1780篇 |
自动化技术 | 6862篇 |
出版年
2024年 | 353篇 |
2023年 | 1099篇 |
2022年 | 2185篇 |
2021年 | 2750篇 |
2020年 | 2692篇 |
2019年 | 2494篇 |
2018年 | 2307篇 |
2017年 | 2629篇 |
2016年 | 2918篇 |
2015年 | 2897篇 |
2014年 | 4064篇 |
2013年 | 4976篇 |
2012年 | 4639篇 |
2011年 | 5371篇 |
2010年 | 3742篇 |
2009年 | 3979篇 |
2008年 | 3707篇 |
2007年 | 4484篇 |
2006年 | 4166篇 |
2005年 | 3751篇 |
2004年 | 3081篇 |
2003年 | 2798篇 |
2002年 | 2236篇 |
2001年 | 1851篇 |
2000年 | 1565篇 |
1999年 | 1374篇 |
1998年 | 1177篇 |
1997年 | 1017篇 |
1996年 | 904篇 |
1995年 | 810篇 |
1994年 | 683篇 |
1993年 | 541篇 |
1992年 | 443篇 |
1991年 | 295篇 |
1990年 | 279篇 |
1989年 | 212篇 |
1988年 | 156篇 |
1987年 | 123篇 |
1986年 | 93篇 |
1985年 | 54篇 |
1984年 | 75篇 |
1983年 | 50篇 |
1982年 | 34篇 |
1981年 | 60篇 |
1980年 | 29篇 |
1979年 | 22篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1959年 | 23篇 |
1951年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
以重庆市甄子岩29号危岩体为研究对象,基于现场调查和分析解剖,建立UDEC离散元数值计算模型,对其演化变形过程进行模拟分析。研究表明,在巨大的自重作用下,由于基座岩体岩质软,岩体较破碎,且基座外侧为直立的陡崖,具有完整的临空面,从而使基座岩体易发生压缩流变及剪切流变,进而使危岩体存在滑移垮塌的危险。 相似文献
2.
The supervision of a hybrid power plant, including solar panels, a gas microturbine and a storage unit operating under varying solar power profiles is considered. The Economic Supervisory Predictive controller assigns the power references to the controlled subsystems of the hybrid cell using a financial criterion. A prediction of the renewable sources power is embedded into the supervisor. Results deteriorate when the solar power is unsteady, owing to the inaccuracy of the predictions for a long-range horizon of 10 s. The receding horizon is switched between an upper and a lower value according to the amplitude of the solar power trend. Theoretical results show the relevance of horizon switching, according to a tradeoff between performance and prediction accuracy. Experimental results, obtained in a Hardware In the Loop (HIL) framework, show the relevance of the variable horizon approach. Power amplifiers allow us to simulate virtual components, such as a gas microturbine, and to blend their powers with that of real devices (storage unit, real solar panels). In this case, fuel savings, reaching 15%, obtained under unsteady operating conditions lead to a better overall performance of the hybrid cell. The overall savings obtained in the experiments amount to 12%. 相似文献
3.
Although rainfall input uncertainties are widely identified as being a key factor in hydrological models, the rainfall uncertainty is typically not included in the parameter identification and model output uncertainty analysis of complex distributed models such as SWAT and in maritime climate zones. This paper presents a methodology to assess the uncertainty of semi-distributed hydrological models by including, in addition to a list of model parameters, additional unknown factors in the calibration algorithm to account for the rainfall uncertainty (using multiplication factors for each separately identified rainfall event) and for the heteroscedastic nature of the errors of the stream flow. We used the Differential Evolution Adaptive Metropolis algorithm (DREAM(zs)) to infer the parameter posterior distributions and the output uncertainties of a SWAT model of the River Senne (Belgium). Explicitly considering heteroscedasticity and rainfall uncertainty leads to more realistic parameter values, better representation of water balance components and prediction uncertainty intervals. 相似文献
4.
Alexandra Kodadová Zuzana Vitková Petra Herdová Anton Ťažký Jarmila Oremusová Daniel Grančai 《Drug development and industrial pharmacy》2015,41(7):1080-1088
This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications. 相似文献
5.
A steelmaking-continuous casting (SCC) scheduling problem is an example of complex hybrid flow shop scheduling problem (HFSSP) with a strong industrial background. This paper investigates the SCC scheduling problem that involves controllable processing times (CPT) with multiple objectives concerning the total waiting time, earliness/tardiness and adjusting cost. The SCC scheduling problem with CPT is seldom discussed in the existing literature. This study is motivated by the practical situation of a large integrated steel company in which the just-in-time (JIT) and cost-cutting production strategy have become a significant concern. To address this complex HFSSP, the scheduling problem is decomposed into two subproblems: a parallel machine scheduling problem (PMSP) in the last stage and an HFSSP in the upstream stages. First, a hybrid differential evolution (HDE) algorithm combined with a variable neighborhood decomposition search (VNDS) is proposed for the former subproblem. Second, an iterative backward list scheduling (IBLS) algorithm is presented to solve the latter subproblem. The effectiveness of this bi-layer optimization approach is verified by computational experiments on well-designed and real-world scheduling instances. This study provides a new perspective on modeling and solving practical SCC scheduling problems. 相似文献
6.
7.
8.
聚α-烯烃是一种性能优良的润滑油基础油,其相对分子质量及分布直接影响宏观性能。本研究建立了一种用于表征1-癸烯齐聚物相对分子质量及分布的方法。采用带示差折光检测器的凝胶渗透色谱系统,综合考虑分离效果和测试可操作性,优化了流动相流速和凝胶色谱柱的组合方式。以四氢呋喃为流动相,流速为0.8 mL/min,色谱柱组合方式为Styragel HR 0.5,Styragel HR 1,PLGEL 3μm MIXED-E三柱串联,以聚苯乙烯作为标准样品,采用普适校正方法处理色谱流出曲线。此方法测得样品的质均相对分子质量与凝胶渗透色谱-光散射法所测定结果相比较,相对误差相对偏差在3%以内。 相似文献
9.
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
10.
软件集成测试技术研究 总被引:1,自引:0,他引:1
首先分析了集成测试的原理和特点,并指出了集成测试的重要性。然后结合传统软件与面向对象软件开发的方法和技术,详细介绍了传统软件的集成测试方法和策略,并深入分析了面向对象软件集成测试的原理和方法。 相似文献