全文获取类型
收费全文 | 34139篇 |
免费 | 3103篇 |
国内免费 | 1650篇 |
专业分类
电工技术 | 832篇 |
综合类 | 2218篇 |
化学工业 | 8691篇 |
金属工艺 | 4006篇 |
机械仪表 | 1406篇 |
建筑科学 | 2105篇 |
矿业工程 | 1528篇 |
能源动力 | 705篇 |
轻工业 | 3974篇 |
水利工程 | 507篇 |
石油天然气 | 785篇 |
武器工业 | 429篇 |
无线电 | 1253篇 |
一般工业技术 | 4998篇 |
冶金工业 | 4063篇 |
原子能技术 | 282篇 |
自动化技术 | 1110篇 |
出版年
2024年 | 71篇 |
2023年 | 553篇 |
2022年 | 950篇 |
2021年 | 1132篇 |
2020年 | 1171篇 |
2019年 | 1010篇 |
2018年 | 970篇 |
2017年 | 1225篇 |
2016年 | 1180篇 |
2015年 | 1138篇 |
2014年 | 1737篇 |
2013年 | 2033篇 |
2012年 | 2122篇 |
2011年 | 2342篇 |
2010年 | 1723篇 |
2009年 | 1806篇 |
2008年 | 1577篇 |
2007年 | 2129篇 |
2006年 | 2137篇 |
2005年 | 1907篇 |
2004年 | 1586篇 |
2003年 | 1418篇 |
2002年 | 1229篇 |
2001年 | 994篇 |
2000年 | 835篇 |
1999年 | 752篇 |
1998年 | 604篇 |
1997年 | 509篇 |
1996年 | 373篇 |
1995年 | 327篇 |
1994年 | 322篇 |
1993年 | 235篇 |
1992年 | 177篇 |
1991年 | 113篇 |
1990年 | 107篇 |
1989年 | 92篇 |
1988年 | 58篇 |
1987年 | 40篇 |
1986年 | 28篇 |
1985年 | 26篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1964年 | 7篇 |
1959年 | 8篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
21.
Rong Yang Anqi Xu Yanting Chen Nan Sun Jinjie Zhang Ru Jia Tao Huang Wenge Yang 《Journal of texture studies》2020,51(6):968-978
In order to ameliorate the gel quality of Dosidicus gigas surimi, the effects of laver powder on gel properties, rheological properties, and water-holding capacity (WHC) were investigated. Results indicated that the addition of laver powder could significantly increase the hardness, chewiness, and breaking force of surimi gels. However, the texture indexes and gel strength began to decline when additional amount exceeded 0.6%. Rheological results demonstrated that the addition of laver powder increased the storage modulus (G′) and viscosity of surimi, prolonged protein denaturation temperature in surimi gels. Moreover, the WHC of surimi gel was improved with the increase of laver powder. Further analyses in low-field nuclear magnetic resonance revealed that laver powder could shorten the transverse relaxation time, enhanced the combination with water, and altered the distribution of different water categories. The proportion of bound water and immobilized water reached its maximum and minimum at 0.6% of laver powder, respectively. Correlation analyses showed that WHC of surimi gel was negatively correlated well with the proportion of loose-bound water, but positively correlated with the strong-bound water and free water. In conclusion, the results supported that 0.6% was the optimal additional amount of laver powder for the squid-based surimi production based on the current ingredients of surimi products. 相似文献
22.
Zviadi Mestvirishvili Vakhtang Kvatchadze Irakli Bairamashvili Nikoloz Jalabadze Tornike Mestvirishvili 《Materials Science & Technology》2020,36(3):327-333
ABSTRACTA method of ultrafine macro-homogeneous composite powder – B4C–ZrO2 production using a planetary mill was developed. From the macro-homogeneous composite high-density ceramics, B4C–ZrB2 was produced by the method of reactive sintering (in situ) at 2000°C under the pressure of 41–42?MPa. The effect of ZrO2 grain size and of its distribution in the matrix on the consolidation parameters, and the microstructure of the obtained ceramics was studied. 相似文献
23.
Natacha Linas Marie-Agnès Peyron Caroline Eschevins Martine Hennequin Emmanuel Nicolas Valérie Collado 《Journal of texture studies》2020,51(5):755-765
This study investigated, for the first time, the masticatory capability of preschool children using natural foods, and the impact of an early oral health alteration (early childhood caries: ECC) on the granulometry of ready-to-swallow food boluses. Thirteen children with ECC were compared to 13 preschool children with a healthy oral condition. Oral health criteria and NOT-S scores (Nordic Orofacial dysfunction Test-Screening) were recorded. For each child, number of masticatory cycles (Nc), chewing time (Ti), and frequency (Fq = Nc/Ti) were recorded during mastication of raw carrot (CAR), cheese (CHS) and breakfast cereals (CER) samples. Food boluses were collected by stopping children at their food-dependent individual swallowing threshold (Nc), and the median food bolus particle size value (D50) was calculated. Correlations were sought between oral health and masticatory criteria. In the ECC group, mean Fq values were significantly decreased for all three foods (p ≤ .001) and mean D50 values were significantly increased (p ≤ .001) compared to the control group (i.e., D50 CAR = 4,384 μm ± 929 vs. 2,960 μm ± 627). These alterations were related to the extent of ECC. The NOT-S mean global score was significantly increased in children with ECC (2.62 ± 1.37 vs. 1 ± 0.91 in the control group, p ≤ .01), due to “Mastication and swallowing” domain impairment. This study gives granulometric normative values for three foods in preschool children and shows the impact of ECC on D50 values. The progression of children's masticatory capability after dental treatment, and the impact of such modifications of sensory input on future eating habits should be explored. 相似文献
24.
Yuqiang Mao Xiangning Bu Guangyuan Xie Erdong Wu Wencheng Xia 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(8):940-950
In this study, the ultrasound was fixed in the pulp zone of flotation cell and its effect on the true flotation of lignite was analyzed. Flotation results indicated that the simultaneous ultrasound treatment increased the concentrate yield and decreased the concentrate ash content. Screening analysis of flotation products revealed that the ultrasound could crush coarse coal to fine coal and scanning electron microscopy (SEM) tests indicated that the ultrasound could reduce the coverage of high-ash coal fines on the coarse particle surface. Thus, the flotation recovery of coarse lignite particle was increased. In addition, the true flotation and entrainment of ?0.074 mm fine particles were studied by the sink-float test and the method of Trahar. It was found the ultrasound significantly enhanced the true flotation of fine particles and improved the overall water recovery in lignite flotation. 相似文献
25.
26.
Waste glass powder was used as a low cost precursor for production of colloidal nanosilica for the first time. The process includes production of wet silica gel and thermal peptization of the wet gel. Purification of the glass powder and wet gel production were initiated by acid washing. The obtained powder was reacted with sodium hydroxide to produce wet silica gel. Type of the applied acid was examined in one factor at a time route. Temperature of the alkaline step and concentrations of the applied acid and base were investigated using Taguchi design of experiments. After finding the best combination of the investigated factor levels in production of the wet gel, time of the stabilization in thermal peptization was studied. Characterizations of the wet gel and colloidal silica were performed by XRF, DLS, FESEM, TEM, FTIR and N2 sorption evaluation. Accordingly pure and stable colloidal nanosilica (98.50%) with average particle size of 21.9?nm was produced from the glass powder successfully. Specific surface area of the dried porous optimum sample was 83.63?m2/g. 相似文献
27.
Sarabjeet Singh Sidhu Malkeet Singh Preetkanwal Singh Bains 《Particulate Science and Technology》2018,36(3):324-331
The present study investigates the thermal conductivity of bimodal SiC particulate distribution in aluminum matrix composites fabricated via powder metallurgy route. The effects of the SiCp reinforcement size distribution and processing parameters such as sintering time and temperature on the thermal conductivity have been examined. The Box–Behnken experimental array was employed to identify the effects of selected variables on the thermal conductivity of the composite. A reasonable augmentation in the thermal conductivity was observed with an increase in sintering time and %volume fraction of fine SiC particulates. It has been demonstrated that the matrix doped with fine SiC particulates (37?µm) occupied interstitial positions and formed continuous SiC–matrix network resulting in minimizing the micropores that contributed for good thermal conductivity, that is, 235?W/mK. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were conducted to evaluate the microstructure architecture and interfacial phase formation. 相似文献
28.
《Advanced Powder Technology》2020,31(1):287-299
The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed. 相似文献
29.
采用等离子堆焊技术在H13钢基体表面上制备了Ni60A/Cr3C2堆焊覆层,研究了覆层的磨损行为和热疲劳性能。在600 ℃下销盘试验的结果表明,镍基碳化铬复合覆层的耐磨性是Ni60A堆焊覆层的2.8倍和基材H13钢的11.6倍。镍基覆层可以显著降低H13钢的摩擦因数,加入碳化铬则会削弱覆层的摩擦性能。随着磨损的进行,主要磨损机理从氧化磨损演变为磨粒磨损和粘着磨损。在800 ℃到室温下的热疲劳测试结果表明,镍基碳化铬复合覆层在48个热循环后疲劳裂纹达到200 μm,早于镍基覆层的62次。这说明高温氧化促进热疲劳裂纹的产生。碳化铬增强相从镍基上剥离,导致镍基复合覆层热疲劳性能下降。 相似文献
30.
采用QBWP-6000J型简支梁旋转弯曲疲劳试验机测定了高疲劳寿命工程机械用钢Q345FCA的疲劳寿命;采用扫描电镜(SEM)对疲劳断口形貌进行了观察,并用附带的能谱仪(EDS)寻找断口上的夹杂物;借助夹杂物自动分析系统对钢中的夹杂物进行了分析。通过对试验数据的分析,计算得出了Q345FCA钢和Q345钢夹杂物的表面临界尺寸、次表面临界尺寸和内部临界尺寸。结果表明,Q345FCA钢的疲劳极限为273 MPa,Q345钢的疲劳极限为266 MPa。Q345FCA钢和Q345钢中夹杂物尺寸均小于临界夹杂物尺寸,且断口形貌显示所有疲劳断裂均不是由夹杂物所引起,夹杂物不是疲劳源。 相似文献