全文获取类型
收费全文 | 5900篇 |
免费 | 396篇 |
国内免费 | 295篇 |
专业分类
电工技术 | 683篇 |
技术理论 | 3篇 |
综合类 | 298篇 |
化学工业 | 1092篇 |
金属工艺 | 626篇 |
机械仪表 | 236篇 |
建筑科学 | 431篇 |
矿业工程 | 118篇 |
能源动力 | 210篇 |
轻工业 | 310篇 |
水利工程 | 27篇 |
石油天然气 | 151篇 |
武器工业 | 27篇 |
无线电 | 581篇 |
一般工业技术 | 517篇 |
冶金工业 | 321篇 |
原子能技术 | 243篇 |
自动化技术 | 717篇 |
出版年
2024年 | 17篇 |
2023年 | 75篇 |
2022年 | 193篇 |
2021年 | 212篇 |
2020年 | 164篇 |
2019年 | 140篇 |
2018年 | 111篇 |
2017年 | 158篇 |
2016年 | 203篇 |
2015年 | 224篇 |
2014年 | 336篇 |
2013年 | 446篇 |
2012年 | 399篇 |
2011年 | 478篇 |
2010年 | 384篇 |
2009年 | 419篇 |
2008年 | 312篇 |
2007年 | 410篇 |
2006年 | 386篇 |
2005年 | 288篇 |
2004年 | 182篇 |
2003年 | 185篇 |
2002年 | 158篇 |
2001年 | 113篇 |
2000年 | 115篇 |
1999年 | 106篇 |
1998年 | 80篇 |
1997年 | 50篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1978年 | 4篇 |
1975年 | 1篇 |
排序方式: 共有6591条查询结果,搜索用时 15 毫秒
81.
Susana P. Alves Payam Vahmani Cletos Mapiye Tim A. McAllister Rui J. B. Bessa Michael E. R. Dugan 《Lipids》2021,56(6):539-562
Trans (t) fatty acids (TFA) from partially hydrogenated vegetable oils (i.e., industrial trans) have been phased out of foods in many countries due to their promotion of cardiovascular disease. This leaves ruminant-derived foods as the main source of TFA. Unlike industrial TFA where catalytic hydrogenation yields a broad distribution of isomers, ruminant TFA are enzymatically derived and can result in enrichment of specific isomers. Comparisons between industrial and ruminant TFA have often exonerated ruminant TFA due to their lack or at times positive effects on health. At extremes, however, ruminant-sourced foods can have either high levels of t10- or t11-18:1, and when considering enriched sources, t10-18:1 has properties similar to industrial TFA, whereas t11-18:1 can be converted to an isomer of conjugated linoleic acid (cis(c)9,t11-conjugated linoleic acid), both of which have potential positive health effects. Increased t10-18:1 in meat-producing ruminants has not been associated with negative effects on live animal production or meat quality. As such, reducing t10-18:1 has not been of immediate concern to ruminant meat producers, as there have been no economic consequences for its enrichment; nevertheless at high levels, it can compromise the nutritional quality of beef and lamb. In anticipation that regulations regarding TFA may focus more on t10-18:1 in beef and lamb, the present review will cover its production, analysis, biological effects, strategies for manipulation, and regulatory policy. 相似文献
82.
采用高能球磨方法制备了PM304复合粉末。研究了纳米PM304粉末的真空烧结致密化和显微组织演化现象,并与未球磨粉末的烧结试样进行了比较。结果表明,提高烧结温度和延长烧结时间有利于提高相对密度,同时组织长大。1100℃,2h是最佳烧结工艺。机械合金化导致粉末纳米化,使真空烧结后的显微组织结构明显细化,使试样的相对密度和抗拉强度比未球磨粉末烧结后的试样有显著提高。 相似文献
83.
[CoPt 1.5 ml/ZrO2 xnm]10 multilayer films were deposited on glass substrates by magnetron sputtering and then annealed in vacuum at 600℃ for 30 min. Their structures and magnetic properties were investigated as a function of ZrO2 content. The results show that the grain size and coercivity first increase and then decrease with the increase in ZrO2 content. The maximum coercivity and grain size are obtained at 37 vol.% of ZrO2. The content of ZrO2 in the film plays an important role in the separation of CoPt grains and in the reduction of intergrain exchange interaction. On the basis of the studies of angular dependent coercivity, it is found that the magnetization reversal of CoPt films with (111 ) texture is different from either the domain wall motion or the S-W type of rotation mode. 相似文献
84.
The creep behavior of directionally solidified (DS) superalloy IC 10 was investigated under 192 MPa and 218 MPa at 980 ℃. Under the testing conditions, the marked creep characteristic of the superalloy is that the creep curve has a short primary and secondary stage and a long tertiary stage. Another creep characteristic is that the superalloy has excellent plasticity at high temperature. To study the creep behavior, the microstructure was observed by SEM and TEM. Different from other microstructure of Ni-base superalloys, superalloy IC10 forms incompletely rafted γ' phase during the creep processes. To understand the creep deformation mechanism of superalloy IC10, the movement of dislocations was analyzed. The results show that the dislocations moving in the γ matrix and climbing over the γ' precipitates is the main deformation mechanism under the experimental conditions. 相似文献
85.
Synthesis and characterization of LiNi0.45Co0.10Mn0.45O2 cathode for lithium ion batteries 总被引:1,自引:1,他引:1
1INTRODUCTIONAdvanced rechargeable lithium ion batteriesare attractive for use in consumer electronic andelectric vehicle(EV)application because of a fa-vorable combination of voltage,energy density,cycling performance,and have been developed rap-idly worldwide during the past decade[1,2].LiCoO2has been widely used as a cathode material in com-mercial lithiumion battery because it is reasonableeasy to synthesize and shows a stable discharge ca-pacity[3].But due to its high cost and toxic… 相似文献
86.
研究两种不同成分具有较大过冷液相区的四元合金Zr65Al7.5Ni10Cu17.5和Zr65Al10Ni10Cu15,非晶和晶态薄带吸氢行为,结果表qt两种薄带的吸氢量均随着温度的升高而增大,非晶薄带的吸氢量要小于同等条件下的晶态薄带的吸氢量且只有在673K吸氢后形成了氢化物,Zr65Al7.5Ni10Cu17.5非晶和晶态薄带吸氢后分别生成了Zr2NiH4.7和ZrH2;而Zr65Al10Ni10Cu15非晶和晶态两种薄带最后生成的氢化物同为ZrH2。 相似文献
87.
由于芯片封装成器件后频率响应会降低,介绍了10 Gbit/s系统用的激光器和探测器的封装技术来封装芯片.通过研究发现,通过金丝电感可以补偿芯片和热沉的寄生电容,从而使封装后的器件频率响应有所改善.利用此封装技术,实现了3 dB调制带宽为10.5 GHz的TO封装激光器.并在此基础上,研发了10 Gbit/s Transponder,且此10 Gbit/s Transponder的测试性能完全满足MSA和ITU-T规范,符合应用要求. 相似文献
88.
89.
退火变脆Fe75Si10B15金属玻璃的脆韧性转变 总被引:1,自引:0,他引:1
研究了机械研磨对退火变脆Fe_(75)Si_(10)B_(15)金属玻璃的弛豫过程,晶化行为及脆韧性转变的影响。发现退火变脆的Fe_(75)Si_(10)B_(15)金属玻璃,经不同时间机械研磨,Curie温度T_C逐渐回落,总的弛像焓ΔH_?逐渐回升。在DSC曲线上观察到明显的玻璃转变温度T_(g_1)和一个附加的宽放热峰T_(x_1),随着研磨时间的增加,T_(x_1),T_(x_1),T_C同步降低,与T_(x_1)对应的放热面积ΔH_(x_1)逐渐增大,并在片状粒子表面形成切变带以及与其对应的剪切带,玻璃在退火过程中失掉的韧性逐渐得到恢复。 相似文献
90.
THERMAL STABILITY OF THE MECHANICALLY ALLOYED Al-10Ti NANOCRYSTALLINE ALLOY DURING CONSOLIDATION PROCESS 总被引:1,自引:0,他引:1
THERMALSTABILITYOFTHEMECHANICALLYALLOYEDAl-10TiNANOCRYSTALLINEALLOYDURINGCONSOLIDATIONPROCESSLiangGuoxian;LiZhichao;WangErde(... 相似文献