全文获取类型
收费全文 | 102488篇 |
免费 | 10153篇 |
国内免费 | 6799篇 |
专业分类
电工技术 | 7901篇 |
技术理论 | 3篇 |
综合类 | 8321篇 |
化学工业 | 14520篇 |
金属工艺 | 6606篇 |
机械仪表 | 7202篇 |
建筑科学 | 8260篇 |
矿业工程 | 3281篇 |
能源动力 | 3202篇 |
轻工业 | 7276篇 |
水利工程 | 2585篇 |
石油天然气 | 4762篇 |
武器工业 | 1284篇 |
无线电 | 12505篇 |
一般工业技术 | 10911篇 |
冶金工业 | 4010篇 |
原子能技术 | 1555篇 |
自动化技术 | 15256篇 |
出版年
2024年 | 440篇 |
2023年 | 1335篇 |
2022年 | 2709篇 |
2021年 | 3959篇 |
2020年 | 2948篇 |
2019年 | 2483篇 |
2018年 | 2684篇 |
2017年 | 3166篇 |
2016年 | 2970篇 |
2015年 | 4322篇 |
2014年 | 5567篇 |
2013年 | 6428篇 |
2012年 | 7649篇 |
2011年 | 8432篇 |
2010年 | 7855篇 |
2009年 | 7560篇 |
2008年 | 7601篇 |
2007年 | 7326篇 |
2006年 | 6849篇 |
2005年 | 5448篇 |
2004年 | 4038篇 |
2003年 | 3297篇 |
2002年 | 3214篇 |
2001年 | 2718篇 |
2000年 | 2138篇 |
1999年 | 1540篇 |
1998年 | 955篇 |
1997年 | 806篇 |
1996年 | 666篇 |
1995年 | 538篇 |
1994年 | 415篇 |
1993年 | 326篇 |
1992年 | 227篇 |
1991年 | 176篇 |
1990年 | 132篇 |
1989年 | 122篇 |
1988年 | 70篇 |
1987年 | 64篇 |
1986年 | 58篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 30篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1959年 | 17篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
121.
预分离色谱法可直接测定混合物中微量组份的无限稀释活度系数(γ~∞),而不必把此组份从混合物中分离出来。主要由四步组成:被测组份的预浓缩,被测组份的定性,选择预分离柱和γ~∞的测定。预浓缩样品经过预分离柱分出被测组份,然后进入测量柱测定γ~∞。此方法简捷、可靠与常规以纯溶质进样的色谱测y~∞的方法具有相同的测定精度,可广泛用于缺少纯样的场合。用此法测定了戊烯-1-炔-4、丁炔-2在若干酸醇中的γ~∞,分别求得了修正和未修正的UNlFAC参数,对kikic修正模型其值为ac=c,CooH=694.9(K)acooH,c=c=-99.08(K),ac=c,oH=812.99(K),aoH,c=c=143.36(K) 相似文献
122.
123.
124.
125.
在介绍循环经济的内涵和发展的基础上 ,结合辽宁省的环境问题 ,提出了只有通过大力发展循环经济 ,才能尽快解决辽宁省的结构性、区域性环境污染问题 相似文献
126.
Sodium-ion battery (SIB) is an ideal device that could replace lithium-ion battery (LIB) in grid-scale energy storage system for power because of the low cost and rich reserve of raw material. The key challenge lies in developing electrode materials enabling reversible Na+ insertion/desertion and fast reaction kinetics. Herein, a core-shell structure, FeS2 nanoparticles encapsulated in biphase TiO2 shell (FeS2@TiO2), is developed towards the improvement of sodium storage. The diphase TiO2 coating supplies abundant anatase/rutile interface and oxygen vacancies which will enhance the charge transfer, and avoid severe volume variation of FeS2 caused by the Na+ insertion. The FeS2 core will deliver high theoretical capacity through its conversion reaction mechanism. Consequently, the FeS2@TiO2 nanorods display notable performance as anode for SIBs including long-term cycling performance (637.8 mA·h·g-1 at 0.2 A·g-1 after 300 cycles, 374.9 mA·h·g-1 at 5.0 A·g-1 after 600 cycles) and outstanding rate capability (222.2 mA·h·g-1 at 10 A·g-1). Furthermore, the synthesized FeS2@TiO2 demonstrates significant pseudocapacitive behavior which accounts for 90.7% of the Na+ storage, and efficiently boosts the rate capability. This work provides a new pathway to fabricate anode material with an optimized structure and crystal phase for SIBs. 相似文献
127.
128.
The oxygen evolution reaction (OER) is the anodic reaction in several industrial electrolytic processes. The objective of this work was to develop a new electrocatalytic material for long-lasting and economical high performance electrodes. New electrodes were prepared by electrodeposition of nickel, nickel-ruthenium and nickel-iridium alloys. They were then activated by anodic polarization at 100 mA cm–2 to form an oxide layer. The electrocatalytic activity was characterized for the OER in 5M KOH solution. The results show that nickel-iridium alloys provide greater electrocatalytic activity for the OER and better corrosion resistance than nickel-ruthenium in alkaline solution. The effects of transition elements on improving the performance of the nickel electrode are then discussed.Notation
b
Tafel slope
-
i
ex
exchange current density
-
i
dp
electrodeposition current density
-
i
OER
oxygen evolution reaction current density
-
C
dl
double-layer capacity
- o2
oxygen overpotential 相似文献
129.
叙述了选择混炼型聚氨酯(PU)与分子量适中的Ⅱ型聚氯乙烯(PVC)树脂制备PVC/PU合金的过程,讨论了PVC/PU共混比、填充剂、硫化体系、共混工艺等因素对PVC/PU合金性能的影响。结果表明:选择PVC/PU=60/40(质量比),硫化剂TD15份,白炭黑30份,混炼温度140—160℃,可制得性能优良的PVC/PU合金。动态力学性能实验显示了PVC/PU合金有较好的相容性。 相似文献
130.
The garment fit played an important role in protective performance, comfort and mobility. The purpose of this study is to quantify the air gap to quantitatively characterize a three-dimensional (3-D) garment fit using a 3-D body scanning technique. A method for processing of scanned data was developed to investigate the air gap size and distribution between the clothing and human body. The mesh model formed from nude and clothed body was aligned, superimposed and sectioned using Rapidform software. The air gap size and distribution over the body surface were analyzed. The total air volume was also calculated. The effects of fabric properties and garment size on air gap distribution were explored. The results indicated that average air gap of the fit clothing was around 25–30 mm and the overall air gap distribution was similar. The air gap was unevenly distributed over the body and it was strongly associated with the body parts, fabric properties and garment size. The research will help understand the overall clothing fit and its association with protection, thermal and movement comfort, and provide guidelines for clothing engineers to improve thermal performance and reduce physiological burden. 相似文献