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61.
beta-N-Acetylhexosaminidase was purified from the extract of cabbage by sequential steps of ammonium sulfate fractionation, chromatofocusing, DEAE-Sepharose CL-6B ion exchange chromatography and Sephacryl S-200 HR gel filtration. By these steps, the purity of the enzyme increased by 256 fold with a recovery of 8%. The purified enzyme was homogeneous as examined by native PAGE. It showed an optimal pH of 4, an optimal temperature of 60 degrees C and a Km of 0.94 mM for hydrolysis of pNp-beta-GlcNAc. The molecular mass of the enzyme determined from filtration through Sephacryl S-200 was 150 kDa. Three subunits with molecular mass of 64, 57 and 51 kDa were observed as determined by SDS-PAGE. NBS (0.025 mM), DEPC (3 mM) and WRK (30 mM) significantly inhibited the activity of the enzyme. The enzyme also showed activity toward pNp-beta-GalNAc, N,N'-diacetylchitobiose, N,N',N"-triacetylchitotriose and N,N',N",N"'-tetraacetyl chitotetraose but showed no activity toward pNp-alpha-GlcNAc, chitin and ethylene glycol chitin. 相似文献
62.
The Arabidopsis CHL1 (AtNRT1) gene confers sensitivity to the herbicide chlorate and encodes a nitrate-regulated nitrate transporter. However, how CHL1 participates in nitrate uptake in plants is not yet clear. In this study, we examined the in vivo function of CHL1 with in vivo uptake measurements and in situ hybridization experiments. Under most conditions tested, the amount of nitrate uptake by a chl1 deletion mutant was found to be significantly less than that of the wild type. This uptake deficiency was reversed when a CHL1 cDNA clone driven by the cauliflower mosaic virus 35S promoter was expressed in transgenic chl1 plants. Furthermore, tissue-specific expression patterns showed that near the root tip, CHL1 mRNA is found primarily in the epidermis, but further from the root tip, the mRNA is found in the cortex or endodermis. These results are consistent with the involvement of CHL1 in nitrate uptake at different stages of root cell development. A functional analysis in Xenopus oocytes indicated that CHL1 is a low-affinity nitrate transporter with a K(m) value of approximately 8.5 mM for nitrate. This finding is consistent with the chlorate resistance phenotype of chl1 mutants. However, these results do not fit the current model of a single, constitutive component for the low-affinity uptake system. To reconcile this discrepancy and the complex uptake behavior observed, we propose a "two-gene" model for the low-affinity nitrate uptake system of Arabidopsis. 相似文献
63.
Bin-Shyan Jong Chien-Hsing Chiang Pai-Feng Lee Tsong-Wuu Lin 《The Visual computer》2010,26(2):121-136
This study proposes a robust and efficient 3D surface remeshing algorithm for mesh quality optimization. Instead of the global
mesh relaxation method proposed in the previous study conducted on remeshing, this study proposes an equilateral triangle
grid-resampling scheme for achieving mesh optimization more efficiently. In order to improve the feasibility of resampling
by directly using an equilateral triangle grid, the surface structure of the original model is correctly extracted by an automatic
surface segmentation technique before the resampling step is executed. Results of this study show that the proposed remeshing
algorithm can automatically and substantially improve the quality of triangulation, as well as automatically preserve shape
features under an acceptable level of measurement error in the shape approximation, which is suitable for a mesh with a specific
topology. 相似文献
64.
Tsung-Che Chiang Hsueh-Chien Cheng Li-Chen Fu 《Computers & Operations Research》2010,37(12):2257-2269
This paper addresses a scheduling problem motivated by scheduling of diffusion operations in the wafer fabrication facility. In the target problem, jobs arrive at the batch machines at different time instants, and only jobs belonging to the same family can be processed together. Parallel batch machine scheduling typically consists of three types of decisions—batch forming, machine assignment, and batch sequencing. We propose a memetic algorithm with a new genome encoding scheme to search for the optimal or near-optimal batch formation and batch sequence simultaneously. Machine assignment is resolved in the proposed decoding scheme. Crossover and mutation operators suitable for the proposed encoding scheme are also devised. Through the experiment with 4860 problem instances of various characteristics including the number of machines, the number of jobs, and so on, the proposed algorithm demonstrates its advantages over a recently proposed benchmark algorithm in terms of both solution quality and computational efficiency. 相似文献
65.
Tomoko Watanabe Traphagan Yueh-hui Vanessa Chiang Hyeseung Maria Chang Benjaporn Wattanawaha Haekyung Lee Michael Charles Mayrath Jeongwon Woo Hyo-Jin Yoon Min Jung Jee Paul E. Resta 《Computers & Education》2010
Using a framework of cognitive, social, and teaching presence, the nature of learning experiences in a three-dimensional virtual world environment (Second Life) and a text-chat learning environment without visuals (TeachNet) were investigated. A mixed method of code frequencies, coherence graphs, interviews, and a survey was used. The results revealed that the TeachNet debates included more cognitive presence codes that indicate higher levels of cognitive processing than in SL debates. The teams were significantly different from each other in the collaboration style for developing arguments and in the ways to use utterances associated with cognitive, social, and teaching presences, and the groups’ collaboration style became more established with more experience with the tasks. The three critical factors–tool, tasks and group cohesion–that affect cognitive, teaching, and social presence are discussed. 相似文献
66.
The Lucas–Kanade tracker (LKT) is a commonly used method to track target objects over 2D images. The key principle behind
the object tracking of an LKT is to warp the object appearance so as to minimize the difference between the warped object’s
appearance and a pre-stored template. Accordingly, the 2D pose of the tracked object in terms of translation, rotation, and
scaling can be recovered from the warping. To extend the LKT for 3D pose estimation, a model-based 3D LKT assumes a 3D geometric
model for the target object in the 3D space and tries to infer the 3D object motion by minimizing the difference between the
projected 2D image of the 3D object and the pre-stored 2D image template. In this paper, we propose an extended model-based
3D LKT for estimating 3D head poses by tracking human heads on video sequences. In contrast to the original model-based 3D
LKT, which uses a template with each pixel represented by a single intensity value, the proposed model-based 3D LKT exploits
an adaptive template with each template pixel modeled by a continuously updated Gaussian distribution during head tracking.
This probabilistic template modeling improves the tracker’s ability to handle temporal fluctuation of pixels caused by continuous
environmental changes such as varying illumination and dynamic backgrounds. Due to the new probabilistic template modeling,
we reformulate the head pose estimation as a maximum likelihood estimation problem, rather than the original difference minimization
procedure. Based on the new formulation, an algorithm to estimate the best head pose is derived. The experimental results
show that the proposed extended model-based 3D LKT achieves higher accuracy and reliability than the conventional one does.
Particularly, the proposed LKT is very effective in handling varying illumination, which cannot be well handled in the original
LKT. 相似文献
67.
Wen-Bin Lin Huann-Keng Chiang Kuang-Rong Shih Chien-An Chen 《Artificial Life and Robotics》2010,15(4):473-477
This article proposes the PC-based LabVIEW as the software to develop the algorithm of the robust complex extended Kalman
filter (RCEKF) to detect the parameters of the voltage signal in power systems. The hardware used is a sample-and-hold card
and a data acquisition (DAQ) card to extract the data from an outside system to the PC, and the program will compute the amplitude,
frequency, and phase of the voltage signal with RCEKF. To validate the performance of RCEKF, the voltage signal from a function
generator was applied to check the feasibility of the algorithm. This application was also used in the Taiwan Power Company
(TPC) secondary substation in Sijhou, Taiwan. 相似文献
68.
In this article, a sliding mode control (SMC) design based on a Gaussian radial basis function neural network (GRBFNN) is
proposed for the synchronous reluctance motor (SynRM) system in electrical motorcycle applications. The conventional SMC assumes
that the upper lumped boundaries of parameter variations and external disturbances are known, and the sign function is used.
This causes high-frequency chattering and the high-gain phenomenon. In order to avoid these drawbacks, the proposed method
utilizes the Lyapunov stability method and the steep descent rule to guarantee the convergence asymptotically, and reduce
the magnitude of the chattering or avoid it completely. Finally, numerical simulations are shown to illustrate the good performance
of our controller design. 相似文献
69.
Cheng-Feng Tai Tzu-Chiang Chiang Ting-Wei Hou 《Expert systems with applications》2011,38(3):2099-2109
Resolving the broadcast storm problem is an important issue in mobile ad hoc networks (MANETs). In this paper, we propose an approach for constructing a virtual subnet whose nodes are logically related. The virtual subnet can be spread upon clusters of a MANET. An intelligent agent with a routing filtering table is proposed to assist the best known clustering algorithms, the original Least ID algorithm and the original Highest Connection Cluster (HCC) algorithm, to improve group communication efficiency. Our simulation covers the network factors of hop count, deprave rate, and delay time. The simulation results show that when the proposed intelligent agent is used with the HCC algorithm, the delay time was reduced by 81.84% as compared with flooding, and by 49.25% as compared with the Ad Hoc On-Demand Distance Vector (AODV) routing algorithm. The delay time for the Least ID algorithm assisted by the proposed agents reduced by 81.84% compared to that of flooding and by 50% compared to that of AODV. 相似文献
70.
Krishna Tushar Kumar Amit Peh Li-Shiuan Postman Jacob Chiang Patrick Erez Mattan 《Micro, IEEE》2009,29(4):48-61
Networks on chip must deliver high bandwidth at low latencies while keeping within a tight power envelope. Using express virtual channels for flow control improves energy-delay throughput by letting packets bypass intermediate routers, but EVCs have key limitations. Nochi (NoC with hybrid interconnect) overcomes these limitations by transporting data payloads and control information on separate planes, optimized for bandwidth and latency respectively. 相似文献