全文获取类型
收费全文 | 4865篇 |
免费 | 232篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 77篇 |
综合类 | 40篇 |
化学工业 | 1059篇 |
金属工艺 | 107篇 |
机械仪表 | 133篇 |
建筑科学 | 76篇 |
矿业工程 | 3篇 |
能源动力 | 264篇 |
轻工业 | 480篇 |
水利工程 | 42篇 |
石油天然气 | 34篇 |
无线电 | 523篇 |
一般工业技术 | 1008篇 |
冶金工业 | 589篇 |
原子能技术 | 59篇 |
自动化技术 | 636篇 |
出版年
2023年 | 83篇 |
2022年 | 170篇 |
2021年 | 263篇 |
2020年 | 172篇 |
2019年 | 179篇 |
2018年 | 229篇 |
2017年 | 195篇 |
2016年 | 196篇 |
2015年 | 124篇 |
2014年 | 198篇 |
2013年 | 321篇 |
2012年 | 221篇 |
2011年 | 257篇 |
2010年 | 182篇 |
2009年 | 157篇 |
2008年 | 154篇 |
2007年 | 146篇 |
2006年 | 125篇 |
2005年 | 104篇 |
2004年 | 89篇 |
2003年 | 72篇 |
2002年 | 71篇 |
2001年 | 45篇 |
2000年 | 50篇 |
1999年 | 54篇 |
1998年 | 199篇 |
1997年 | 134篇 |
1996年 | 110篇 |
1995年 | 72篇 |
1994年 | 79篇 |
1993年 | 71篇 |
1992年 | 51篇 |
1991年 | 46篇 |
1990年 | 27篇 |
1989年 | 40篇 |
1988年 | 42篇 |
1987年 | 24篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 34篇 |
1983年 | 16篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 33篇 |
1975年 | 17篇 |
1974年 | 24篇 |
1972年 | 14篇 |
排序方式: 共有5130条查询结果,搜索用时 15 毫秒
241.
Matching Trajectories of Anatomical Landmarks Under Viewpoint,Anthropometric and Temporal Transforms
Alexei Gritai Yaser Sheikh Cen Rao Mubarak Shah 《International Journal of Computer Vision》2009,84(3):325-343
An approach is presented to match imaged trajectories of anatomical landmarks (e.g. hands, shoulders and feet) using semantic
correspondences between human bodies. These correspondences are used to provide geometric constraints for matching actions
observed from different viewpoints and performed at different rates by actors of differing anthropometric proportions. The
fact that the human body has approximate anthropometric proportion allows innovative use of the machinery of epipolar geometry
to provide constraints for analyzing actions performed by people of different sizes, while ensuring that changes in viewpoint
do not affect matching. In addition, for linear time warps, a novel measure, constructed only from image measurements of the
locations of anatomical landmarks across time, is proposed to ensure that similar actions performed at different rates are
accurately matched as well. An additional feature of this new measure is that two actions from cameras moving at constant
(and possibly different) velocities can also be matched. Finally, we describe how dynamic time warping can be used in conjunction
with the proposed measure to match actions in the presence of nonlinear time warps. We demonstrate the versatility of our
algorithm in a number of challenging sequences and applications, and report quantitative evaluation of the matching approach
presented. 相似文献
242.
243.
Tapas Debnath Subrata Chandra Roy Claus H. Rüscher Altaf Hussain 《Journal of Materials Science》2009,44(1):179-185
Needle-shaped crystals of sizes up to 5 μm × 5 μm × 40 μm of nominal composition K
x
Nb
y
W1−y
O3 were synthesized by solid state method at 800 °C using appropriate amount of WO3, WO2, Nb2O5, and K2WO4. The samples were characterized with XRD, SEM, microprobe analysis, optical spectroscopy, and Raman spectroscopy. The XRD
patterns of the samples show single phase of tetragonal tungsten bronze (TTB) type (P4/mbm, No. 127) up to y = 0.07. Structure refinements reveal an increase in cell parameter with increasing nominal niobium content within the TTB
phase. The elemental compositions of the crystals determined by electron microprobe analysis also show an increase in Nb content
with increasing y. With increasing Nb content the reflectivity minimum in the near infrared spectral range shifts towards lower wavenumber
indicating the effect of decreasing carrier concentration. Pyrochlore type phase (KNbWO6) is obtained as a second phase when nominal composition y > 0.07. 相似文献
244.
This work is aimed at the development of a state observer (steady state Kalman filter) for a multivariable system with unknown time delays, which is subjected to unmeasured disturbances. To design such a filter, we explore the feasibility of capturing system dynamics using generalized orthonormal basis filters (GOBF). A two step identification procedure is proposed by exploiting the fact that the GOBF based models have output error structure. The deterministic component of the model is identified in the first step and used to compute a residual signal. In the second step, a filter that whitens the residuals is estimated using GOBF and combined with the deterministic component. A minimal order state realization of the innovation form of the state model is then generated from this high order model using realization based sub-space based state space (4SID) identification algorithm. When time delays are not known a-priori, the similarity between GOBF and Pade approximation is used to estimates time delay matrix directly from multivariate data. The efficacy of the proposed modeling technique is demonstrated by carrying out simulation studies on the benchmark Shell control problem and experimental evaluation on a stirred tank heater (STH) system. From the analysis of simulation and experimental results, it can be inferred that the proposed approach produces fairly accurate estimates of the time delay matrix and the deterministic and stochastic components of the dynamic model. 相似文献
245.
R.B. Gopaluni H. Raghavan R.S. Patwardhan S.L. Shah G.A. Dumont 《Journal of Process Control》2006,16(9):903-912
A new identification method for single-input–single-output delay dominant recycle systems is presented in this paper. Identification of recycle systems is similar to that of closed loop systems. However, identification of recycle systems poses certain challenges in that the input-equivalent signal in the closed loop identification is not available for recycle systems. Therefore, special identification routines are required to ensure consistency of recycle and forward models. It is shown that consistent estimates of delay dominant recycle systems can be obtained by treating a delayed output as one of the inputs. Asymptotic variance expressions for the estimates of forward and recycle models are provided. These are then used in designing an optimal excitation signal for recycle systems. The results are illustrated through an industrial example. 相似文献
246.
Discretization: An Enabling Technique 总被引:26,自引:0,他引:26
247.
We report the uniform planar anchoring of thermotropic liquid crystals on films of bovine serum albumin (BSA) covalently immobilized on the surface of glass microscope slides and mechanically rubbed using a cloth. The azimuthal orientations of the liquid crystals were measured to be parallel to the direction of rubbing. Following immersion and removal of these rubbed films of BSA from aqueous solutions containing either BSA, fibrinogen, lysozyme, anti-FITC immunoglobulin G (IgG), or antistreptavidin IgG, we measured liquid crystals placed onto these surfaces to largely retain their uniform alignment. In contrast, following immersion of a rubbed film of BSA into an aqueous solution of anti-BSA IgG, we observed liquid crystals on these surfaces to assume nonuniform orientations. We conclude that specific binding of anti-BSA IgG to the film of rubbed BSA erased anisotropy induced within the film of BSA by rubbing. This result suggests that the spatial scale of anisotropy within the rubbed film of BSA is comparable to or smaller than the size of the IgG molecule. Because the anisotropy within a rubbed film of a protein can be erased by specific binding of a second protein, we believe these types of substrates (rubbed films of proteins) have the potential to be useful in a variety of label-free biomolecular assays where specific binding of a target species to its ligand can be imaged through observation of the optical appearance of liquid crystal placed onto the surface. 相似文献
248.
D. G. Kuberkar N. A. Shah M. R. Gonal R. Prasad R. G. Kulkarni 《Journal of Superconductivity》2000,13(1):37-40
It has been reported that, by adding equal amounts of CaO and CuO to non superconducting La3Ba3Cu6O
z
(La-336), a series of superconductors with nominal compositions La3Ca
y
Ba3Cu6+y
O
z
were prepared with maximum Ton
c 80K. Similar studies on addition of CaO and CuO in nonsuperconducting LaBaCu2O
z
(La-112) resulted into superconducting LaCaBaCu3O
z
(La-1113). To date no attempt has been made to synthesize La2CaBa2Cu5O
z
(La-2125) superconducting phase by addition of CaO and CuO to non superconducting La2Ba2Cu4O
z
(La-224) system. Also no reports are published to study the effect of replacing larger La3+-ions (1.01Å) by smaller rare earth ions viz Y3+(0.89Å), Er3+(0.91Å), Gd3+(0.91Å) on the structural and superconducting properties of (La2–x
R
x
)Ba2(Ca
y
Cu4+y
)O
z
(LRBCaC); 0.0 x 0.5; y=2x system. In this paper, we report the method of synthesis, structural and superconducting property characterization using X-ray diffraction, oxygen content measurements using iodometry, resistivity measurements using d.c. four probe technique and a.c. susceptibility measurements in the temperature range RT to 15K. Also a comparative study, on the evolution of superconducting phase with Ca-concentration for different rare earth substitutions for LRBCaC system in the context of hole doping mechanism, is carried out. 相似文献
249.
The use of grounding transformers on three-phase ungrounded governmental, industrial, and commercial distribution systems is addressed. Ground-fault protection schemes that provide selective and reasonably fast tripping are often incorporated with these grounding transformers. The authors first review the state of the art of grounding transformers to assist electric power systems engineers in the proper understanding of the use and applications of these devices and then discuss two governmental system case studies illustrating improperly applied grounding transformers and/or associated ground-fault protection systems. In addition, they describe remedial actions taken to correct these deficiencies. The objective in presenting improper grounding transformer applications is to highlight protection concerns that are often ignored. It is stressed that a single grounding transformer is not adequate for use with a multibus configuration. A unique protection scheme for use on a multibus arrangement is presented 相似文献
250.
D'Souza MJ Oettinger CW Shah A Tipping PG Huang XR Milton GV 《Drug development and industrial pharmacy》1999,25(5):591-596
A macrophage plays an important role in mediating the inflammatory response. Cytokines released by activated macrophages contribute to inflammation in glomerulonephritis (GN). Clodronate, a biphosphonate, causes macrophage depletion when administered in an encapsulated form in liposomes. We used albumin as the polymer matrix to microencapsulate clodronate to the microspheres (MS) in the 1-micron size range. The purpose of this study was to (a) determine macrophage depletion by clodronate MS, (b) determine the effect of clodronate MS on endotoxin-induced cytokine release in vitro, and (c) assess the effect of clodronate MS on macrophage infiltration in experimental antiglomerular basement membrane nephritis. Macrophage depletion by clodronate MS was assessed by staining for the EDI marker. The results indicate greater than 95% depletion of macrophages from the spleen, liver, kidney, and blood. In the whole blood model, clodronate MS attenuated endotoxin-induced tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) release, and the attenuation by the microencapsulated form of clodronate was also more effective than the free (solution) form of clodronate. Macrophage infiltration into the glomerulus in experimental GN was also blocked very effectively by pretreatment with clodronate MS. In conclusion, macrophage depletion by clodronate MS may be beneficial in reducing cytokine release and renal damage in GN. 相似文献