全文获取类型
收费全文 | 132719篇 |
免费 | 12233篇 |
国内免费 | 7920篇 |
专业分类
电工技术 | 9346篇 |
技术理论 | 3篇 |
综合类 | 10161篇 |
化学工业 | 19748篇 |
金属工艺 | 7958篇 |
机械仪表 | 8881篇 |
建筑科学 | 11155篇 |
矿业工程 | 3875篇 |
能源动力 | 4113篇 |
轻工业 | 9109篇 |
水利工程 | 3048篇 |
石油天然气 | 6518篇 |
武器工业 | 1491篇 |
无线电 | 16106篇 |
一般工业技术 | 14615篇 |
冶金工业 | 5622篇 |
原子能技术 | 1945篇 |
自动化技术 | 19178篇 |
出版年
2024年 | 560篇 |
2023年 | 1750篇 |
2022年 | 3452篇 |
2021年 | 4986篇 |
2020年 | 3727篇 |
2019年 | 3142篇 |
2018年 | 3381篇 |
2017年 | 4009篇 |
2016年 | 3728篇 |
2015年 | 5313篇 |
2014年 | 6843篇 |
2013年 | 8102篇 |
2012年 | 9366篇 |
2011年 | 10310篇 |
2010年 | 9480篇 |
2009年 | 9148篇 |
2008年 | 9167篇 |
2007年 | 8867篇 |
2006年 | 8463篇 |
2005年 | 6910篇 |
2004年 | 5025篇 |
2003年 | 4187篇 |
2002年 | 4103篇 |
2001年 | 3482篇 |
2000年 | 2978篇 |
1999年 | 2438篇 |
1998年 | 1831篇 |
1997年 | 1516篇 |
1996年 | 1381篇 |
1995年 | 1139篇 |
1994年 | 881篇 |
1993年 | 742篇 |
1992年 | 511篇 |
1991年 | 389篇 |
1990年 | 352篇 |
1989年 | 274篇 |
1988年 | 201篇 |
1987年 | 147篇 |
1986年 | 130篇 |
1985年 | 76篇 |
1984年 | 67篇 |
1983年 | 60篇 |
1982年 | 49篇 |
1981年 | 39篇 |
1980年 | 33篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
"橄榄型"社会阶层结构范式论 总被引:1,自引:0,他引:1
拥有一个"橄榄型"社会阶层结构,社会就会减少动荡,保持社会的相对稳定与和谐.现阶段培育"橄榄型"的社会阶层结构,是构建社会主义和谐社会的重要基础. 相似文献
12.
针对烧结厂烧结电除尘灰的工况特性,介绍了输送烧结电除尘灰的正压气力输灰系统的特点、组成,还对在调试和试运行过程中遇到的故障进行了分析并制订了解决措施。 相似文献
13.
14.
Fernando J. Muzzio Marcos Llusa Christopher L. Goodridge Nhat-Hang Duong Elizabeth Shen 《Powder Technology》2008,186(3):247-254
This paper investigates the effects of processing and equipment parameters of a ribbon blender (i.e. loading method of lubricant, fill level, blade speed and blade design) on magnesium stearate homogeneity. A core sampling technique is used to obtain at least one hundred samples per sampling event, which are extracted throughout the blender and yield a thorough characterization of the entire bed. The results presented here can be used as a guideline to develop appropriate blending processes and characterization protocols for ribbon blenders. 相似文献
15.
Ring‐opening polymerization of D,L ‐lactide (LA) has been successfully carried out by using rare earth 2,6‐dimethylaryloxide (Ln(ODMP)3) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)3 exhibits higher activity to prepare poly(D,L ‐lactide) (PLA) with a viscosity molecular weight of 4.5 × 104 g mol?1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)3 has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)3 is 69.6 kJ mol?1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ‘coordination–insertion’ mechanism with selective cleavage of the acyl–oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry 相似文献
16.
以三维软件进行车轮造型,用CAD软件建立固有频率分析数学模型,对车轮固有频率进行分析和处理.结合其他试验的分析,对车轮进行优化设计. 相似文献
17.
根据在农村通自来水工程实践中积累的经验,提出并较好地解决了农村供水工程的评价标准,设计供水时间的确定,输配水管网设计中的优化等问题,对建好、管好和用好农村自来水工程具有一定的帮助作用. 相似文献
18.
19.
Yun‐Hwei Shen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):581-586
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry 相似文献
20.
In this paper, we investigate the problem of determining the optimal bandwidth allocation for a Dynamic Bandwidth Allocation Scheme (DBAS). The objective is to minimize the total amount of bandwidth required to satisfy the Quality of Service (QoS) requirements of all traffic streams. It is shown that when the performance functions satisfy a certain number of conditions, there exists a unique optimal bandwidth allocation such that, for each traffic stream, either its QoS is just satisfied or its QoS is over-satisfied and it is allocated zero bandwidth. Such an allocation is said to be efficient. It is also shown that there exists a unique efficient allocation in the entire feasible region. An iterative algorithm is developed to compute the efficient allocation employing its special properties. Numerical examples are presented to demonstrate how the algorithm works. Future extensions of this work are also discussed.Partially supported by NSERC of Canada through grants OGP14020 and STRIN-200. 相似文献