全文获取类型
收费全文 | 3857篇 |
免费 | 206篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 48篇 |
综合类 | 13篇 |
化学工业 | 1086篇 |
金属工艺 | 108篇 |
机械仪表 | 132篇 |
建筑科学 | 102篇 |
矿业工程 | 10篇 |
能源动力 | 296篇 |
轻工业 | 516篇 |
水利工程 | 35篇 |
石油天然气 | 41篇 |
无线电 | 283篇 |
一般工业技术 | 703篇 |
冶金工业 | 158篇 |
原子能技术 | 42篇 |
自动化技术 | 512篇 |
出版年
2024年 | 14篇 |
2023年 | 65篇 |
2022年 | 155篇 |
2021年 | 189篇 |
2020年 | 156篇 |
2019年 | 159篇 |
2018年 | 209篇 |
2017年 | 208篇 |
2016年 | 179篇 |
2015年 | 123篇 |
2014年 | 157篇 |
2013年 | 346篇 |
2012年 | 241篇 |
2011年 | 238篇 |
2010年 | 177篇 |
2009年 | 203篇 |
2008年 | 204篇 |
2007年 | 149篇 |
2006年 | 105篇 |
2005年 | 89篇 |
2004年 | 61篇 |
2003年 | 61篇 |
2002年 | 49篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 53篇 |
1997年 | 30篇 |
1996年 | 26篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 24篇 |
1985年 | 15篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1975年 | 6篇 |
排序方式: 共有4085条查询结果,搜索用时 15 毫秒
81.
Baha Vural kok Mehmet Yilmaz Mustafa Akpolat 《International Journal of Pavement Engineering》2017,18(12):1052-1059
In this study, the rheological and conventional properties of binders prepared with crumb rubber (CR) and FT-paraffin were compared to styrene-butadiene-styrene (SBS)-modified binders’ properties. The objective of this study was to determine which modified binders in different combinations of the CR and the FT-paraffin exhibited better performance than the SBS-modified binders, in terms of conventional and rheological properties. Results showed that the additives exhibited different performances for different types of tests. Many of the combinations including the common usage of the CR and the FT-paraffin performed better at high temperature than the SBS modification. Overall, the test results show that the binders prepared by 6% CR with 3 and 4% FT-paraffin and those prepared with 8% CR with 3% FT-paraffin were better binders than the 4% SBS-modified binder, in terms of low and high temperature properties. 相似文献
82.
Ali Firat Cabalar Waleed Sulaiman Mustafa 《International Journal of Pavement Engineering》2017,18(8):714-726
Materials forming sand grains and colluvial soil deposits have a distinct structure, consisting of a composite matrix of coarse and fine soil grains. The influence of sand grains content on the behaviour of sand–clay mixtures was investigated by a series of intensive laboratory experiments. The California bearing ratio (CBR), unconfined compression strength (UCS) and compaction tests were carried out on various contents of sand and clay mixtures. The sand–clay mixtures were prepared with sand contents of 0, 10, 20, 30, 40, and 50% by weight. The laboratory tests on these mixtures have indicated that their behaviour will depend on the relative concentration of the sand and clay samples. The results of the tests showed a decrease in the UCS, and an increase the CBR values with an increase in the amount of sand. An increase in dry unit weight and a decrease in respective moisture content by an increase in the amount of sand were observed in the compaction tests. 相似文献
83.
84.
85.
Noraini Nordin Samikannu Kanagesan Nur Rizi Zamberi Swee Keong Yeap Nadiah Abu Subramani Tamilselvan Mansor Hashim Noorjahan Banu Alitheen 《IET nanobiotechnology / IET》2017,11(3):343
In this study, nanocrystalline magnesium zinc ferrite nanoparticles were successfully prepared by a simple sol–gel method using copper nitrate and ferric nitrate as raw materials. The calcined samples were characterised by differential thermal analysis/thermogravimetric analysis, Fourier transform infrared spectroscopy and X‐ray diffraction. Transmission electron microscopy revealed that the average particle size of the calcined sample was in a range of 17–41 nm with an average of 29 nm and has spherical size. A cytotoxicity test was performed on human breast cancer cells (MDA MB‐231) and (MCF‐7) at various concentrations starting from (0 µg/ml) to (800 µg/ml). The sample possessed a mild toxic effect toward MDA MB‐231 and MCF‐7 after being examined with MTT (3‐[4, 5‐dimethylthiazol‐2‐yl]‐2, 5 diphenyltetrazolium bromide) assay for up to 72 h of incubation. Higher reduction of cells viability was observed as the concentration of sample was increased in MDA MB‐231 cell line than in MCF‐7. Therefore, further cytotoxicity tests were performed on MDA MB‐231 cell line.Inspec keywords: sol‐gel processing, nanoparticles, nanofabrication, magnesium compounds, zinc compounds, toxicology, biological organs, cancer, cellular biophysics, nanomedicine, calcination, differential thermal analysis, Fourier transform infrared spectra, X‐ray diffraction, transmission electron microscopy, particle size, organic compoundsOther keywords: sol‐gel method, cytotoxic effects, breast cancer cell line, MDA MB‐231 in vitro, nanocrystalline magnesium zinc ferrite nanoparticles, copper nitrate, ferric nitrate, raw materials, calcined samples, differential thermal analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, average particle size, cytotoxicity testing, human breast cancer cells, mild toxic effect, 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5 diphenyltetrazolium bromide) assay, cell viability, MCF‐7, MDA MB‐231 cell line, size 17 nm to 41 nm 相似文献
86.
Shahad Alyousif Mohammed Dauwed Rafal Nader Mohammed Hasan Ali Mustafa Musa Jabar Ahmed Alkhayyat 《计算机、材料和连续体(英文)》2023,75(1):531-546
The number of mobile devices accessing wireless networks is skyrocketing due to the rapid advancement of sensors and wireless communication technology. In the upcoming years, it is anticipated that mobile data traffic would rise even more. The development of a new cellular network paradigm is being driven by the Internet of Things, smart homes, and more sophisticated applications with greater data rates and latency requirements. Resources are being used up quickly due to the steady growth of smartphone devices and multimedia apps. Computation offloading to either several distant clouds or close mobile devices has consistently improved the performance of mobile devices. The computation latency can also be decreased by offloading computing duties to edge servers with a specific level of computing power. Device-to-device (D2D) collaboration can assist in processing small-scale activities that are time-sensitive in order to further reduce task delays. The task offloading performance is drastically reduced due to the variation of different performance capabilities of edge nodes. Therefore, this paper addressed this problem and proposed a new method for D2D communication. In this method, the time delay is reduced by enabling the edge nodes to exchange data samples. Simulation results show that the proposed algorithm has better performance than traditional algorithm. 相似文献
87.
Zaher Al Aghbari Ibrahim Kamel Ahmed Mustafa 《Peer-to-Peer Networking and Applications》2011,4(4):391-409
Recently, many applications have used Peer-to-Peer (P2P) systems to overcome the current problems with client/server systems
such as non-scalability, high bandwidth requirement and single point of failure. In this paper, we propose an efficient scheme
to support efficient range query processing over structured P2P systems, while balancing both the storage load and access
load. The paper proposes a rotating token scheme to balance the storage load by placing joining nodes in appropriate locations
in the identifier space to share loads with already overloaded nodes. Then, to support range queries, we utilize an order-preserving
mapping function to map keys to nodes in order preserving way and without hashing. This may result in an access load imbalance
due to non-uniform distribution of keys in the identifier space. Thus, we propose an adaptive replication scheme to relieve
overloaded nodes by shedding some load on other nodes to balance the access load. We derive a formula for estimating the overhead
of the proposed adaptive replication scheme. In this study, we carry simulation experiments with synthetic data to measure
the performance of the proposed schemes. Our simulation experiments show significant gains in both storage load balancing
and access load balancing. 相似文献
88.
In this paper, we present general formulae for the mask of (2b + 4)-point n-ary approximating as well as interpolating subdivision schemes for any integers ${b\,\geqslant\,0}$ and ${n\,\geqslant\,2}$ . These formulae corresponding to the mask not only generalize and unify several well-known schemes but also provide the mask of higher arity schemes. Moreover, the 4-point and 6-point a-ary schemes introduced by Lian [Appl Appl Math Int J 3(1):18–29, 2008] are special cases of our general formulae. 相似文献
89.
Xiaoping Tu Louis-A. Dessaint Roger Champagne Kamal Al-Haddad 《Mathematics and computers in simulation》2010,81(2):194-207
Most simulation models of electric machines use the coupled circuit approach, where the machine is considered as an electric circuit element with time-varying inductances (abc model) or with constant inductances (dq0 model). On the other hand, the rotating magnetic field approach, which considers the electric machine as two groups of windings producing rotating magnetic fields and can give insight into internal phenomena of the machines, has not yet received much attention in electric machines modeling, especially for machine transient analysis. Based on the rotating magnetic field approach, this paper presents a transient model of the induction machine including main flux saturation effect. Based on the direct computation of the magnetizing fluxes of all machine windings, the model represents instantaneous main flux saturation by simply introducing a main flux saturation factor. No iteration process is involved to incorporate the saturation effects. The model combines the advantages of the dq0 and abc models advantages, such as rapid computation time and nonsymmetrical conditions simulation, respectively. The simulation results and the experimental tests show advantages and verification of the model. 相似文献
90.
Mustafa Sarıdemir 《Expert systems with applications》2011,38(11):14257-14268
Compressive strength and splitting tensile strength are both mechanical properties of concrete that are utilized in structural design. This study presents gene expression programming (GEP) as a new tool for the formulations of splitting tensile strength from compressive strength of concrete. For purpose of building the GEP-based formulations, 536 experimental data have been gathered from existing literature. The GEP-based formulations are developed for splitting tensile strength of concrete as a function of age of specimen and cylinder compressive strength. In experimental parts of this study, cylindrical specimens of 150 × 300 mm and 100 × 200 mm in dimensions are utilized. Training and testing sets of the GEP-based formulations are randomly separated from the complete experimental data. The GEP-based formulations are also validated with additional 173 data of experimental results other than the data used in training and testing sets of the GEP-based formulations. All of the results obtained from the GEP-based formulations are compared with the results obtained from experimental data, the developed regression-based formulation and formulas given by some national building codes. These comparisons showed that the GEP-based formulations appeared to well agree with the experimental data and found to be quite reliable. 相似文献