全文获取类型
收费全文 | 19700篇 |
免费 | 915篇 |
国内免费 | 141篇 |
专业分类
电工技术 | 329篇 |
综合类 | 33篇 |
化学工业 | 4412篇 |
金属工艺 | 603篇 |
机械仪表 | 646篇 |
建筑科学 | 398篇 |
矿业工程 | 48篇 |
能源动力 | 1404篇 |
轻工业 | 1213篇 |
水利工程 | 152篇 |
石油天然气 | 96篇 |
武器工业 | 1篇 |
无线电 | 2409篇 |
一般工业技术 | 4484篇 |
冶金工业 | 1469篇 |
原子能技术 | 181篇 |
自动化技术 | 2878篇 |
出版年
2024年 | 103篇 |
2023年 | 427篇 |
2022年 | 1018篇 |
2021年 | 1184篇 |
2020年 | 926篇 |
2019年 | 955篇 |
2018年 | 1247篇 |
2017年 | 986篇 |
2016年 | 957篇 |
2015年 | 614篇 |
2014年 | 856篇 |
2013年 | 1563篇 |
2012年 | 923篇 |
2011年 | 1115篇 |
2010年 | 900篇 |
2009年 | 850篇 |
2008年 | 758篇 |
2007年 | 606篇 |
2006年 | 501篇 |
2005年 | 387篇 |
2004年 | 294篇 |
2003年 | 255篇 |
2002年 | 199篇 |
2001年 | 189篇 |
2000年 | 173篇 |
1999年 | 174篇 |
1998年 | 296篇 |
1997年 | 247篇 |
1996年 | 222篇 |
1995年 | 177篇 |
1994年 | 160篇 |
1993年 | 162篇 |
1992年 | 106篇 |
1991年 | 134篇 |
1990年 | 101篇 |
1989年 | 103篇 |
1988年 | 83篇 |
1987年 | 93篇 |
1986年 | 79篇 |
1985年 | 90篇 |
1984年 | 79篇 |
1983年 | 71篇 |
1982年 | 64篇 |
1981年 | 70篇 |
1980年 | 50篇 |
1979年 | 35篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1976年 | 35篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
In this paper a new estimation approach combining both Recursive Least Square (RLS) and Bacterial Foraging Optimization (BFO) is developed for accurate estimation of harmonics in distorted power system signals. The proposed RLS–BFO hybrid technique has been employed for estimating the fundamental as well as harmonic components present in power system voltage/current waveforms. The basic foraging strategy is made adaptive by using RLS that sequentially updates the unknown parameters of the signal. Simulation and experimental studies are included justifying the improvement in performance of this new estimation algorithm. 相似文献
132.
Anil Kumar William R. Leo Lawrence Green Gene L. Woodruff 《Journal of Fusion Energy》1989,8(1-2):107-126
The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2×2 NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.Work done while on visiting assignment to Institut de Génie Atomique, E.P.F.L. 相似文献
133.
A mathematical model for the transient heat flow analysis in arc-welding processes is proposed, based on a unique set of boundary conditions. The model attempts to make use of the relative advantages of analytical as well as numerical techniques in order to reduce the problem size for providing a quicker solution without sacrificing the accuracy of prediction. The variation of thermo-physical properties with temperature has been incorporated into the model to improve the thermal analysis in the weld and heat-affected zones. The model has been evaluated using a five-point explicit finite difference method for analysing the welding heat flow in thin plates of two different geometric configurations. The temperature distribution closer to the heat source, primarily in the weld zone and the heat-affected zones, are predicted by the numerical technique. The thermal characteristics beyond the heat-affected zone are amenable to standard analytical techniques. The behaviour of the boundary condition in the model has been investigated in detail.Nomenclature
q
Rate of heat per unit thickness (Wm–1)
-
d
Plate thickness (m)
-
v
Velocity of source (m s–1)
-
t
Time (s)
-
T
Temperature value at the desired point (K)
-
T
0
Initial temperature (K)
-
K
Thermal conductivity (W m–1 K–1)
-
Density (kg m–3)
-
c
p
Specific heat (J kg–1 K–1)
-
Thermal diffusivity (m2 s–1)
-
n
-
Distance of point considered from the source (=x–vt) (m)
-
K
0
Modified Bessel function of second kind and zero order
-
r
Radial distance from the source (r=(x
2+y
2)1/2) (m)
-
Model width (m)
-
a
Plate width (m)
-
Distance from the source =(2+4 ×10–4)1/2 (m)
- n
相似文献
134.
This paper presents the analysis of a parallel formulation of depth-first search. At the heart of this parallel formulation is a dynamic work-distribution scheme that divides the work between different processors. The effectiveness of the parallel formulation is strongly influenced by the work-distribution scheme and the target architecture. We introduce the concept of isoefficiency function to characterize the effectiveness of different architectures and work-distribution schemes. Many researchers considered the ring architecture to be quite suitable for parallel depth-first search. Our analytical and experimental results show that hypercube and shared-memory architectures are significantly better. The analysis of previously known work-distribution schemes motivated the design of substantially improved schemes for ring and shared-memory architectures. In particular, we present a work-distribution algorithm that guarantees close to optimal performance on a shared-memory/-network-with-message-combining architecture (e.g. RP3). Much of the analysis presented in this paper is applicable to other parallel algorithms in which work is dynamically shared between different processors (e.g., parallel divide-and-conquer algorithms). The concept of isoefficiency is useful in characterizing the scalability of a variety of parallel algorithms.This work was supported by Army Research Office Grant No. DAAG29-84-K-0060 to the Artificial Intelligence Laboratory, and Office of Naval Research Grant N00014-86-K-0763 to the Computer Science Department at the University of Texas at Austin. 相似文献
135.
Manu Kumar Sang-Min Chung Ganuskh Enkhtaivan Rahul V. Patel Han-Seung Shin Bhupendra M. Mistry 《International journal of molecular sciences》2021,22(5)
In this study, we have introduced newly synthesized substituted benzothiazole based berberine derivatives that have been analyzed for their in vitro and in silico biological properties. The activity towards various kinds of influenza virus strains by employing the cytopathic effect (CPE) and sulforhodamine B (SRB) assay. Several berberine–benzothiazole derivatives (BBDs), such as BBD1, BBD3, BBD4, BBD5, BBD7, and BBD11, demonstrated interesting anti-influenza virus activity on influenza A viruses (A/PR/8/34, A/Vic/3/75) and influenza B viral (B/Lee/40, and B/Maryland/1/59) strain, respectively. Furthermore, by testing neuraminidase activity (NA) with the neuraminidase assay kit, it was identified that BBD7 has potent neuraminidase activity. The molecular docking analysis further suggests that the BBD1–BBD14 compounds’ antiviral activity may be because of interaction with residues of NA, and the same as in oseltamivir. 相似文献
136.
Biswas Uttara Rakshit Jayanta Kumar Das Joyashree Bharti Gaurav Kumar Suthar Bhuvneshwer Amphawan Angela Najjar Monia 《SILICON》2021,13(3):885-892
Silicon - In the present report, a photonic crystal based micro-ring resonator (MRR) structure is proposed which is very compact in size and has very fast response and is employed for temperature... 相似文献
137.
Silicon - The primary purpose of this work is to study the effect of symmetric and asymmetric variation of underlap regions both on source and drain side of 3D SOI n-FinFET. Underlap length is... 相似文献
138.
Silicon - In this paper, a dielectric modulated dual material gate TFET (DM-DMG_TFET)based biosensor is proposed. In order to detect various biomolecules, a nanogap cavity is formed by the... 相似文献
139.
Solay Leo Raj Singh Sarabdeep Kumar Naveen Amin S. Intekhab Anand Sunny 《SILICON》2021,13(12):4633-4640
Silicon - In this treatise, we have proposed a Single Material Gate–Dual Gate Impact Ionization Metal Oxide Semiconductor (SMG DG-IMOS) based Pressure Sensor. The pressure sensor has the most... 相似文献
140.
Silicon - In recent times, the study on machining characteristics of combined (hybrid) fiber polymer composites has drawn a remarkable research attention because of its emerging industrial... 相似文献