全文获取类型
收费全文 | 59721篇 |
免费 | 4885篇 |
国内免费 | 2712篇 |
专业分类
电工技术 | 2637篇 |
技术理论 | 7篇 |
综合类 | 6684篇 |
化学工业 | 5516篇 |
金属工艺 | 1650篇 |
机械仪表 | 2113篇 |
建筑科学 | 15046篇 |
矿业工程 | 2388篇 |
能源动力 | 1216篇 |
轻工业 | 3969篇 |
水利工程 | 2077篇 |
石油天然气 | 2302篇 |
武器工业 | 324篇 |
无线电 | 4385篇 |
一般工业技术 | 4201篇 |
冶金工业 | 2656篇 |
原子能技术 | 380篇 |
自动化技术 | 9767篇 |
出版年
2024年 | 338篇 |
2023年 | 991篇 |
2022年 | 1590篇 |
2021年 | 1865篇 |
2020年 | 1839篇 |
2019年 | 1568篇 |
2018年 | 1206篇 |
2017年 | 1401篇 |
2016年 | 1457篇 |
2015年 | 1724篇 |
2014年 | 3429篇 |
2013年 | 2970篇 |
2012年 | 3856篇 |
2011年 | 4150篇 |
2010年 | 3373篇 |
2009年 | 3728篇 |
2008年 | 3568篇 |
2007年 | 4268篇 |
2006年 | 3823篇 |
2005年 | 3399篇 |
2004年 | 2874篇 |
2003年 | 2540篇 |
2002年 | 2053篇 |
2001年 | 1729篇 |
2000年 | 1453篇 |
1999年 | 1144篇 |
1998年 | 783篇 |
1997年 | 652篇 |
1996年 | 561篇 |
1995年 | 530篇 |
1994年 | 395篇 |
1993年 | 338篇 |
1992年 | 286篇 |
1991年 | 203篇 |
1990年 | 195篇 |
1989年 | 178篇 |
1988年 | 158篇 |
1987年 | 120篇 |
1986年 | 81篇 |
1985年 | 90篇 |
1984年 | 76篇 |
1983年 | 34篇 |
1982年 | 29篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1979年 | 35篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1975年 | 20篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
The development of a sustainable energy system throughout an enterprise is a complex task, which requires an agile holistic approach. Such an approach needs to include a variety of objectives including energy strategy formation and strategic decision-making, which are directly related to the analysis and management of the main areas of sustainable development:The economic, technological, environmental, and social. These multidimensional requirements of sustainability are often difficult to achieve within the enterprise, because these aspects are interrelated and influenced by various internal and external environment factors. This paper first reviews the main challenges for an energy system, and then demonstrates how a strategic agile enterprise architecture driven approach could effectively guide the sustainable energy system development. The study presented in this paper provides a holistic approach that contributes to the advancement and usage of literature dealing with issues of sustainable energy system development and agile enterprise architecture, which has not been discussed before to any great extent. 相似文献
3.
We investigated the resistive switching characteristics of a polystyrene:ZnO–graphene quantum dots system and its potential application in a one diode-one resistor architecture of an organic memory cell. The log–log I–V plot and the temperature-variable I–V measurements revealed that the switching mechanism in a low-current state is closely related to thermally activated transport. The turn-on process was induced by a space-charge-limited current mechanism resulted from the ZnO–graphene quantum dots acting as charge trap sites, and charge transfer through filamentary path. The memory device with a diode presented a ∼103 ION/IOFF ratio, stable endurance cycles (102 cycles) and retention times (104 s), and uniform cell-to-cell switching. The one diode-one resistor architecture can effectively reduce cross-talk issue and realize a cross bar array as large as ∼3 kbit in the readout margin estimation. Furthermore, a specific word was encoded using the standard ASCII character code. 相似文献
4.
Protein databases used in research are huge and still grow at a fast pace. Many comparisons need to be done when searching similar (homologous) sequences for a given query sequence in these databases. Comparing a query sequence against all sequences of a huge database using the well-known Smith–Waterman algorithm is very time-consuming. Hidden Markov Models pose an opportunity for reducing the number of entries of a database and also enable to find distantly homologous sequences. Fewer entries are achieved by clustering similar sequences in a Hidden Markov Model. Such an approach is used by the bioinformatics tool HHblits. To further reduce the runtime, HHblits uses two-level prefiltering to reduce the number of time-consuming Viterbi comparisons. Still, prefiltering is very time-consuming. Highly parallel architectures and huge bandwidth are required for processing and transferring the massive amounts of data. In this article, we present an approach exploiting the reconfigurable, hybrid computer architecture Convey HC-1 for migrating the most time-consuming part. The Convey HC-1 with four FPGAs and high memory bandwidth of up to 76.8 GB/s serves as the platform of choice. Other bioinformatics applications have already been successfully supported by the HC-1. Limited by FPGA size only, we present a design that calculates four first-level prefiltering scores per FPGA concurrently, i.e. 16 calculations in total. This score calculation for the query profile against database sequences is done by a modified Smith–Waterman scheme that is internally parallelized 128 times in contrast to the original Streaming ‘Single Instruction Multiple Data (SIMD)’ Extensions (SSE)-supported implementation where only 16-fold parallelism can be exploited and where memory bandwidth poses the limiting factor. Preloading the query profile, we are able to transform the memory-bound implementation to a compute- and resource-bound FPGA design. We tightly integrated the FPGA-based coprocessor into the hybrid computing system by employing task-parallelism for the two-level prefiltering. Despite much lower clock rates, the FPGAs outperform SSE-based execution for the calculation of the prefiltering scores by a factor of 7.9. 相似文献
5.
6.
Measuring nonlinear optical response of a specific material in a mixture, not only leads to investigate the behavior of a particular component in various circumstances, but also can be a way to select suitable combination and optimum concentration of additives and therefore obtaining the maximum nonlinear optical signals. In this work, by using dual-arm Z-scan technique, the nonlinear refractive index of Disperse Red1 (DR1) organic dye molecules inside the core of prepared polymeric nanocapsules was measured among various materials which prepared nanocapsules were made of them. Then the measured value was compared with nonlinear refractive index of DR1 solved in dichloromethane. 相似文献
7.
The aim of this paper was to determine the content of vasoactive biogenic amines in Sremski kulen and Sremska kobasica and to estimate hygienic conditions and good manufacturing practice (GMP) according to proposed criteria. Formation of dansyl chloride derivatizated vasoactive amines were determined using HPLC–DAD. Tryptamine (47.6; 34.2 mg/kg), histamine (16.1; 6.42 mg/kg) and tyramine (95.1; 45.2 mg/kg) were detected in both investigated type of traditional dry fermented sausages while phenylethylamine was not detected. Total content of vasoactive amines did not exceed the sum (200 mg/kg) proposed as a possible indicator of hygienic conditions and GMP in sausage production. 相似文献
8.
文章中主要采用有机溶剂萃取法(OSE)对高浓度石油污染土壤进行修复,经过精馏操作,有效回收原油,建立脱附等温曲线,研究了石油污染物在土壤-有机溶剂两相间的迁移规律。 相似文献
9.
10.
针对辽河油区超稠油采油污水的特点,采用Fenton试剂催化氧化,对采油污水处理进行研究。实验研究及现场应用结果表明,此方法对污水的CODCr具有良好的去除效果。处理后污水经过简单生化,进一步降解污染物,能够实现稳定迭标排放,且具有能耗低、运行成本低和操作简单等特点。 相似文献