全文获取类型
收费全文 | 21637篇 |
免费 | 1662篇 |
国内免费 | 190篇 |
专业分类
电工技术 | 366篇 |
综合类 | 98篇 |
化学工业 | 5709篇 |
金属工艺 | 533篇 |
机械仪表 | 827篇 |
建筑科学 | 816篇 |
矿业工程 | 37篇 |
能源动力 | 1476篇 |
轻工业 | 2044篇 |
水利工程 | 352篇 |
石油天然气 | 333篇 |
武器工业 | 9篇 |
无线电 | 2247篇 |
一般工业技术 | 3910篇 |
冶金工业 | 696篇 |
原子能技术 | 156篇 |
自动化技术 | 3880篇 |
出版年
2024年 | 102篇 |
2023年 | 435篇 |
2022年 | 886篇 |
2021年 | 1408篇 |
2020年 | 1203篇 |
2019年 | 1394篇 |
2018年 | 1588篇 |
2017年 | 1450篇 |
2016年 | 1408篇 |
2015年 | 845篇 |
2014年 | 1352篇 |
2013年 | 2234篇 |
2012年 | 1444篇 |
2011年 | 1578篇 |
2010年 | 1070篇 |
2009年 | 955篇 |
2008年 | 642篇 |
2007年 | 519篇 |
2006年 | 438篇 |
2005年 | 293篇 |
2004年 | 264篇 |
2003年 | 209篇 |
2002年 | 172篇 |
2001年 | 117篇 |
2000年 | 111篇 |
1999年 | 101篇 |
1998年 | 164篇 |
1997年 | 138篇 |
1996年 | 120篇 |
1995年 | 88篇 |
1994年 | 63篇 |
1993年 | 74篇 |
1992年 | 58篇 |
1991年 | 54篇 |
1990年 | 55篇 |
1989年 | 44篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 41篇 |
1985年 | 33篇 |
1984年 | 41篇 |
1983年 | 35篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 22篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1976年 | 25篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Murad Nour Mohammad Belfiore Jean Claude Guisantes George Rodriguez 《Wireless Personal Communications》2002,20(2):145-161
In DS-WCDMA mobile systems such the UMTS, asynchronous cell site operation,assigning different long spreading code to each cell, yields the advantageof flexible system deployment. We can design an indoor system basedon an outdoor one. However, in general, much longer search time isrequired in asynchronous operation than in synchronous. This paperproposes three techniques to take decisions about synchronizationbased on observation of correlated signals. Classical decision criterialike maximum and threshold criterion are presented. A new decisioncriteria that we call Threshold&Max combined decision criteriais analyzed. The results of this new introduced technique is comparedwith the classical ones. 相似文献
72.
73.
Abdelbaki Benamor Brahim Si Ali Mohamed Kheireddine Aroua 《Korean Journal of Chemical Engineering》2008,25(3):451-460
The absorption rates of CO2 into aqueous solutions of Diethanolamine (DEA) with varying concentrations from 0.2 to 4M and temperature range from 293
to 323 K were measured by using a laboratory stirred reactor. The CO2 partial pressure was varied in a range that the reaction would occur in pseudo first order regime. Experimental data were
analyzed and the kinetic parameters associated with the reaction were determined. The activation energy for the deprotonation
of the intermediate zwitterion was estimated at about 11.4 kcal/mol. The contribution of carbamate formation to the overall
absorbed CO2 was experimentally evaluated and found to be of the order of 100%. 相似文献
74.
Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry 相似文献
75.
Mohammad Mozammel Hoq Tsuneo Yamane Shoichi Shimizu Tadashi Funada Shiro Ishida 《Journal of the American Oil Chemists' Society》1985,62(6):1016-1021
Continuous hydrolysis of olive oil byCandida cylindracea’s lipase was studied in a microporous hydrophobic membrane bioreactor. Olive oil and buffer solution, fed continuously through two compartments partitioned by membrane, caused reaction at the interface of lipase-adsorbed membrane and buffer solution. Fatty acid was obtained in a single phase without being mixed with components of other phases. At all mean residence times, countercurrent flow mode was superior to cocurrent one. The lipase was adsorbed onto the membrane, and its adsorption was suggested to be partially specific from the experiments with enzymes having various levels of purity. The percent hydrolysis depended hyperbolically on the interfacial enzyme concentration. The hydrolysis seemed to be limited by diffusion of fat or fatty acid through the micropores of the membrane at higher interfacial enzyme concentrations. The lipase was stabilized significantly by glycerol added to the buffer solution. Satisfactory performance of the membrane bioreactor was obtained in a longterm continuous operation which lasted for 24 days by feeding buffer-glycerol (18.0%) solution over the adsorbed lipase. The operational half-life of the adsorbed enzyme was 15 days at 40 C. 相似文献
76.
Ali J. Koshkouei 《International Journal of Adaptive Control and Signal Processing》2008,22(9):859-874
Passivity with sliding mode control for a class of nonlinear systems with and without unknown parameters is considered in this paper. In fact, a method for deriving a nonlinear system with external disturbances to a passive system is considered. Then a passive sliding mode control is designed corresponding to a given storage function. The passivity property guarantees the system stability while sliding mode control techniques assures the robustness of the proposed controller. When the system includes unknown parameters, an appropriate updated law is obtained so that the new transformed system is passive. The passivation property of linear systems with sliding mode is also analysed. The linear and nonlinear theories are applied to a simple pendulum model and the gravity‐flow/pipeline system, respectively. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
77.
This study describes a laboratory method for the estimation of emission from preservative-treated wood in the different situations where emissions could enter the environment for use classes 3 (not in contact with ground) and 4 and 5 (in contact with the ground, fresh water or sea water) according to OECD Guidelines. Samples of scotch pine sapwood (Pinus sylvestris L.) were treated with CCA (1% and 2%), ACQ-1900 (3% and 7%), ACQ-2200 (2%), Tanalith E 3491 (2% and 2.8%), and Wolmanit CX-8 (2%). 相似文献
78.
Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments. 相似文献
79.
80.