全文获取类型
收费全文 | 96074篇 |
免费 | 6872篇 |
国内免费 | 3662篇 |
专业分类
电工技术 | 5305篇 |
技术理论 | 5篇 |
综合类 | 5672篇 |
化学工业 | 15723篇 |
金属工艺 | 5537篇 |
机械仪表 | 6431篇 |
建筑科学 | 6279篇 |
矿业工程 | 2717篇 |
能源动力 | 2251篇 |
轻工业 | 6321篇 |
水利工程 | 1798篇 |
石油天然气 | 5625篇 |
武器工业 | 675篇 |
无线电 | 10072篇 |
一般工业技术 | 14001篇 |
冶金工业 | 5581篇 |
原子能技术 | 1270篇 |
自动化技术 | 11345篇 |
出版年
2024年 | 342篇 |
2023年 | 1341篇 |
2022年 | 2557篇 |
2021年 | 3441篇 |
2020年 | 2790篇 |
2019年 | 2507篇 |
2018年 | 3263篇 |
2017年 | 3650篇 |
2016年 | 3505篇 |
2015年 | 3701篇 |
2014年 | 5009篇 |
2013年 | 5938篇 |
2012年 | 6074篇 |
2011年 | 6600篇 |
2010年 | 5909篇 |
2009年 | 5816篇 |
2008年 | 5635篇 |
2007年 | 5248篇 |
2006年 | 5027篇 |
2005年 | 3974篇 |
2004年 | 2888篇 |
2003年 | 2498篇 |
2002年 | 2626篇 |
2001年 | 2275篇 |
2000年 | 2231篇 |
1999年 | 2249篇 |
1998年 | 1877篇 |
1997年 | 1656篇 |
1996年 | 1238篇 |
1995年 | 999篇 |
1994年 | 800篇 |
1993年 | 580篇 |
1992年 | 519篇 |
1991年 | 338篇 |
1990年 | 274篇 |
1989年 | 204篇 |
1988年 | 154篇 |
1987年 | 104篇 |
1986年 | 95篇 |
1985年 | 83篇 |
1984年 | 62篇 |
1983年 | 56篇 |
1982年 | 44篇 |
1981年 | 35篇 |
1980年 | 40篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1976年 | 31篇 |
1970年 | 18篇 |
1969年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
961.
962.
The effect of the processing molding temperature on the properties and crystalline structure of acrylonitile‐butadiene rubber (NBR)/nylon 6,66,1010 (trinylon) thermoplastic vulcanizates (TPV) was studied. With decreasing molding temperature, the stress at 100% and elongation at break of TPV changed slightly, and the solvent resistance of TPV improved. The best conditions for processing molding were 170°C and 12 min. The crystalline structure of the nylon continuous phase in TPV was investigated by X‐ray diffraction, polarized optical microscopy, and differential scanning calorimetry. The results show that the crystalline structure of the nylon phase in TPV was more perfect/orderly and formed α‐crystalline structure at a processing molding temperature of 170°C. Therefore, the oil resistance of NBR/trinylon TPV clearly improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1374–1379, 2006 相似文献
963.
The polyesterification and isomerization reaction of 1,6-hexane diol and maleic anydride in a melt without catalyst was studied by 13C and 1H n.m.r. spectroscopy. The structure and concentration of oligoester species during the polyesterification and isomerization were determined depending on the reaction temperature and time. According to the number and configuration of repeating units determined from 1H n.m.r. spectra kinetics of both reactions were also considered. The degree of isomerization is continuously increasing in the investigated reaction range. 相似文献
964.
A range of ceramic materials with low sintering temperature have been developed using ceramic and glass wastes (up to 70%). Properties of the newly synthesized materials are given, and areas of application and fabrication methods are discussed.__________Translated from Novye Ogneupory, No. 10, pp. 39 – 41, October, 2004. 相似文献
965.
T. V. Barinova I. P. Borovinskaya V. I. Ratnikov T. I. Ignat’eva 《International Journal of Self-Propagating High-Temperature Synthesis》2007,16(2):92-95
Synthetic analogs of titanate ceramics (perovskite and zirconolite) designed for use as a matrix for immobilization of high-level
nuclear fuel reprocessing wastes (HLW). Such ceramics have been prepared by SHS method from a mixture of titanate ceramics
and non-radioactive model oxides. Synthesis conditions have been optimized. The synthesized low-porosity cylindrical compacts
exhibited a high strength and low rate for leaching Cs, Sr, Y, Ce, and La in bidistilled water. The phase composition and
microstructure of synthesized products have been characterized. The immobilization of Cs was found to be accompanied by a
marked loss of this element.
The text was submitted by the authors in English. 相似文献
966.
对比分析了动态热塑性硫化胶(TPV)的加工设备,着重介绍了附加振动力场的三螺杆反应挤出机的结构特点以及利用该机进行三元乙丙橡胶/聚丙烯(EPDM/PP)的动态全硫化,对制品的物理力学性能和微观结构分别进行了测试分析和电镜扫描。结果表明,振动力场作用下EPDM/PP共混体系反应挤出动态硫化加工可有效地实现动态硫化反应、硫化橡胶的粉碎和分散以及相态反转,振动力场的作用明显提高了TPV性能。 相似文献
967.
Meng-Fei Luo Mai He Yun-Long Xie Ping Fang Ling-Yun Jin 《Applied catalysis. B, Environmental》2007,69(3-4):213-218
A novel CeO2–Y2O3 (CY) washcoat on cordierite honeycomb was prepared by an impregnation method, which was used as a support to prepare a Pd catalyst. A model reaction of the complete combustion of toluene was conducted to evaluate the performance of the developed Pd/CY catalyst. The CY washcoat support and the Pd/CY catalyst were characterized by XRD, Raman spectroscopy, H2-TPR and SEM techniques. The results show that compared with conventional washcoat the CY washcoat has better adhesion and higher vibration- and heat-resistance. The CY washcoat can anchor well Pd onto the cordierite honeycomb substrate. The formation of a CeO2–Y2O3 solid solution and the steady present of PdO occur at high calcination temperatures, resulting in a better thermal stability. On a Pd/CY catalyst calcined at 500 °C, a 99% of toluene conversion was obtained at 210 °C, and it was stable for reaction time up to 30 h. 相似文献
968.
Abstract Multi-core digital signal processors (DSPs) are widely used in wireless telecommunication, core network transcoding, industrial control, and audio/video processing technologies, among others. In comparison with general-purpose multi-processors, multi-core DSPs normally have a more complex memory hierarchy, such as on-chip core-local memory and non-cache-coherent shared memory. As a result, efficient multi-core DSP applications are very difficult to write. The current approach used to program multi-core DSPs is based on proprietary vendor software development kits (SDKs), which only provide low-level, non-portable primitives. While it is acceptable to write coarse-grained task-level parallel code with these SDKs, writing fine-grained data parallel code with SDKs is a very tedious and error-prone approach. We believe that it is desirable to possess a high-level and portable parallel programming model for multi-core DSPs. In this paper, we propose OpenMDSP, an extension of OpenMP designed for multi-core DSPs. The goal of OpenMDSP is to fill the gap between the OpenMP memory model and the memory hierarchy of multi-core DSPs. We propose three classes of directives in OpenMDSP, including 1) data placement directives that allow programmers to control the placement of global variables conveniently, 2) distributed array directives that divide a whole array into sections and promote the sections into core-local memory to improve performance, and 3) stream access directives that promote big arrays into core-local memory section by section during parallel loop processing while hiding the latency of data movement by the direct memory access (DMA) of a DSP. We implement the compiler and runtime system for OpenMDSP on PreeScale MSC8156. The benchmarking results show that seven of nine benchmarks achieve a speedup of more than a factor of 5 when using six threads. 相似文献
969.
根据不同成分的水样中细菌再生长情况,研究了水中磷对生物稳定性的限制因子作用。结果显示,在测试水样中添加1 mg/L的NaAc后,细菌总数增加了100%-187%;在水样中添加15μg/L的NaH2PO4后,细菌总数增加了180%-203%。随水样中PO43-P含量的增加,细菌数目也在逐渐增加,但当水中PO43-P的含量大于等于5μg/L时,细菌已无明显增长趋势。试验结果表明磷和碳一样也是水中微生物生长的限制因素之一,并且对于该水样当PO43-P的含量为2μg/L—5μg/L之间的某个值时,磷的限制作用将会表现出来。 相似文献
970.
Calcium carbonate/natural rubber (NR) latex nanometer composites were prepared by adding nanometer CaCO3 whose surface had been treated to natural rubber latex (NRL) before sulfuration. The physical, thermooxidative aging, and thermal degradation properties and the ultra‐microstructure were analyzed with a multipurpose material testing meter, a thermal analysis meter and a Philips XL‐30 SEM, respectively. The results showed that the structures and properties of nanometer composites could be clearly improved by NRL mixed with surface‐treated nanometer CaCO3. The physical properties of the nanometer composites were best when the content of surface treatment agent was 2.5% (to nanometer CaCO3), the nanometer CaCO3/NRL content was 3:100, and the stirring time for treating the surface of the nanometer CaCO3 was 20 min. Simultaneously, the thermooxidative aging resistance of the nanometer composites also was significantly improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3442–3447, 2006 相似文献