全文获取类型
收费全文 | 2520篇 |
免费 | 298篇 |
国内免费 | 260篇 |
专业分类
电工技术 | 15篇 |
综合类 | 130篇 |
化学工业 | 909篇 |
金属工艺 | 409篇 |
机械仪表 | 100篇 |
建筑科学 | 33篇 |
矿业工程 | 50篇 |
能源动力 | 37篇 |
轻工业 | 83篇 |
水利工程 | 7篇 |
石油天然气 | 74篇 |
武器工业 | 40篇 |
无线电 | 186篇 |
一般工业技术 | 530篇 |
冶金工业 | 327篇 |
原子能技术 | 129篇 |
自动化技术 | 19篇 |
出版年
2024年 | 20篇 |
2023年 | 75篇 |
2022年 | 98篇 |
2021年 | 107篇 |
2020年 | 119篇 |
2019年 | 116篇 |
2018年 | 91篇 |
2017年 | 122篇 |
2016年 | 98篇 |
2015年 | 110篇 |
2014年 | 149篇 |
2013年 | 176篇 |
2012年 | 153篇 |
2011年 | 137篇 |
2010年 | 94篇 |
2009年 | 118篇 |
2008年 | 85篇 |
2007年 | 141篇 |
2006年 | 149篇 |
2005年 | 112篇 |
2004年 | 105篇 |
2003年 | 80篇 |
2002年 | 104篇 |
2001年 | 85篇 |
2000年 | 61篇 |
1999年 | 58篇 |
1998年 | 49篇 |
1997年 | 38篇 |
1996年 | 38篇 |
1995年 | 36篇 |
1994年 | 21篇 |
1993年 | 9篇 |
1992年 | 21篇 |
1991年 | 28篇 |
1990年 | 22篇 |
1989年 | 22篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1976年 | 1篇 |
1959年 | 3篇 |
排序方式: 共有3078条查询结果,搜索用时 15 毫秒
101.
以四硼酸钠、钛酸丁酯、三乙醇胺、甘油、乙二醇为原料,合成了有机硼钛交联剂,制备了葫芦巴胶压裂液。研究了主剂及配体物料比,反应温度与反应时间对交联剂成胶性能的影响。结果表明,m(四硼酸钠)∶m(钛酸丁酯)=1∶4,m(三乙醇胺)∶m(甘油)=1∶2,反应温度70℃,反应时间3 h的条件下,合成的交联剂性能最优。考察了w(葫芦巴胶溶液)=0.4%,m(葫芦巴胶溶液)∶m(硼钛交联剂)=100∶(0.4~0.6)时,葫芦巴胶压裂液的性能,交联延时150 s,耐温耐剪切性能良好;常温下,携砂比V(压裂液)∶V(石英砂)=70∶30时,沉降速度0.009mm/s;体系易破胶,破胶液黏度低于5 m Pa·s,对储层伤害小。 相似文献
102.
Preparation and Use of a Boron Nitride Precursor as Binder for the Densification of Boron Nitride 总被引:1,自引:0,他引:1
A precursor of boron nitride was prepared through the partial condensation of 2,4,6-trichloroborazine and bis-(trimethylsilyl)acetylene. This reaction was conducted at 100°C and is catalyzed by AlCl3 . The condensation product pyrolyzed at 800°C, producing trimethylsilyl chloride as a volatile product and a boron nitride rich residue containing 54 wt% of the initial weight. Mixtures of the precursor and commercial boron nitride were made and hot-pressed at 800°C and 27.6 MPa. A maximum density of 1.84 g/cm3 is reached at a loading corresponding to the deposition of 13 wt% residue derived from the precursor. Examination by analytical electron microscopy, including X-ray energy dispersive spectroscopy and electron energy loss spectroscopy analyses, revealed the location of material derived from the precursor in BN-binder composites through the presence of residual aluminum, silicon, and carbon. Crystallization of boron nitride from the precursor appears to have taken place, as deduced from the morphology of the phases observed and association with residual elements present in the binder. 相似文献
103.
A novel gel polymer electrolyte (GPE) which is based on new synthesized boron‐containing monomer, benzyl methacrylate, 1 m LiClO4/N,N‐dimethylformamidel liquid electrolyte solution is prepared through a one‐step synthesis method. The boron‐containing GPE (B‐GPE) not only displays excellent mechanical behavior, favorable thermal stability, but also exhibits an outstanding ionic conductivity of 2.33 mS cm?1 at room temperature owing to the presence of anion‐trapping boron sites. The lithium ion transference in this gel polymer film at ambient temperature is 0.60. Furthermore, the symmetrical supercapacitor which is fabricated with B‐GPE as electrolyte and reduced graphene oxide as electrode demonstrates a broad potential window of 2.3 V. The specific capacitance of symmetrical B‐GPE supercapacitors retains 90% after 3000 charge–discharge cycles at current density of 1 A g?1. 相似文献
104.
《Ceramics International》2019,45(15):18556-18562
In order to improve bonding property between SiC fibers and matrix of SiCf/SiC composites, boron nitride (BN) interfacial coatings were synthesized by chemical vapor infiltration. BN coatings were fabricated from BCl3–NH3 gaseous mixtures at four different temperatures (843 °C, 900 °C, 950 °C and 1050 °C) with different deposition times. Growth kinetics, nucleation and growth processes, microstructure and chemical composition of boron nitride coatings were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectrometry. Results showed that deposition rate increased as the temperature increased from 843 °C to 950 °C. However, deposition rate decreased slightly from 23.10 ± 0.85 nm/min (950 °C) to 21.39 ± 0.67 nm/min when the temperature was increased further to 1050 °C. It could be due to the nucleation occurring in the gas and the consumption of a large amount of BCl3 and NH3. When deposition temperature was 843 °C, BN grains deposited on top layer of the coating could not completely cross Ehrlich-Schwoebel barrier and grew in island growth mode. On the other hand, the deposition pattern followed a layer-by-layer growth mode when deposition temperature was 1050 °C. Deposition temperature significantly affected the microstructure of as-deposited BN coatings. At 843 °C, 950 °C and 1050 °C, the coatings presented amorphous, polycrystalline and hexagonal structures, respectively. 相似文献
105.
研究了高密度聚乙烯/铅硼复合材料的屏蔽性能和力学性能,通过屏蔽仿真比较了密度及碳化硼(B4C)含量对屏蔽性能的影响,通过试验比较了B4C含量对屏蔽性能、弯曲强度及冲击强度的影响。仿真结果表明,随聚乙烯/铅硼复合材料密度升高,快中子屏蔽性能下降,热中子屏蔽性能和γ屏蔽性能提高;保持聚乙烯/铅硼复合材料密度不变,随B4C含量的提高,中子屏蔽性能提高而γ屏蔽性能下降;实验数据表明,随B4C含量的升高,高密度聚乙烯/铅硼材料的快中子屏蔽性能、热中子屏蔽性能升高,γ屏蔽系数下降,冲击强度和弯曲强度下降明显,屏蔽性能测试结果和仿真结果规律性相符;综合仿真结果和实验数据表明,含B4C 2 %左右的高密度聚乙烯/铅硼复合材料同时具有较好的屏蔽性能和力学性能。 相似文献
106.
107.
纳米TiO2填料在防火涂料中的主要作用是增强涂膜的机械强度和附着力,防止裂纹,防止紫外线和水分透过,延长涂膜的使用寿命等.以硼酚醛树脂、环氧树脂作为基料,三聚氰胺、六次甲基四胺为防火助剂,制备了添加纳米TiO2填料的防火涂料.通过理化性能、防火性能检测及热重分析、扫描电镜测试、红外光谱分析等手段,研究了添加纳米TiO2填料对硼酚醛防火涂料性能的影响,并利用锥形量热仪对涂料进行火灾危险性评价. 相似文献
108.
109.
使用硅烷偶联剂对纳米二氧化硅表面进行化学改性和修饰,制备出一种纳米有机硼交联剂BC-27,采用FTIR、SEM、高温流变仪、高温高压失水仪对交联剂BC-27及其配制的压裂液进行了结构表征与性能测试,考察了改性纳米SiO2含量、稠化剂羟丙基胍胶(HPG)质量分数、交联比(压裂液基液与交联剂的质量之比)、pH值对交联剂BC-27交联性能的影响,并测试了交联剂形成羟丙基胍胶压裂液的抗温抗剪切性能、静态滤失性能、破胶与反排性能以及岩芯渗透率伤害性能。研究结果表明:w(改性纳米SiO2)=0.18%时制备得到纳米交联剂BC-27的性能最佳;当压裂液基液中w(HPG)=0.35%,交联比为100:0.3,调节pH值约为11时,形成的压裂液冻胶效果最好,最高抗温温度为130℃,交联时间在89~225s可调;纳米有机硼交联剂BC-27配制的压裂液在130℃下连续剪切120min,其黏度仍保持在440mPa·s以上,而普通有机硼交联剂OS-150配制的压裂液仅为280mPa·s左右;有机硼交联剂OS-150形成的压裂液对储层岩芯伤害率为23.08%,而交联剂BC-27形成的压裂液仅为19.47%。该纳米交联剂性能优异,具有良好的延缓交联性能,可有效降低羟丙基胍胶用量。 相似文献
110.