全文获取类型
收费全文 | 5242篇 |
免费 | 119篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 413篇 |
综合类 | 17篇 |
化学工业 | 1503篇 |
金属工艺 | 136篇 |
机械仪表 | 138篇 |
建筑科学 | 189篇 |
矿业工程 | 1篇 |
能源动力 | 244篇 |
轻工业 | 513篇 |
水利工程 | 19篇 |
石油天然气 | 7篇 |
无线电 | 292篇 |
一般工业技术 | 923篇 |
冶金工业 | 196篇 |
原子能技术 | 215篇 |
自动化技术 | 582篇 |
出版年
2023年 | 31篇 |
2022年 | 60篇 |
2021年 | 97篇 |
2020年 | 53篇 |
2019年 | 64篇 |
2018年 | 76篇 |
2017年 | 63篇 |
2016年 | 112篇 |
2015年 | 80篇 |
2014年 | 152篇 |
2013年 | 323篇 |
2012年 | 187篇 |
2011年 | 306篇 |
2010年 | 257篇 |
2009年 | 279篇 |
2008年 | 317篇 |
2007年 | 263篇 |
2006年 | 204篇 |
2005年 | 222篇 |
2004年 | 177篇 |
2003年 | 161篇 |
2002年 | 166篇 |
2001年 | 105篇 |
2000年 | 97篇 |
1999年 | 99篇 |
1998年 | 109篇 |
1997年 | 78篇 |
1996年 | 75篇 |
1995年 | 55篇 |
1994年 | 82篇 |
1993年 | 69篇 |
1992年 | 56篇 |
1991年 | 76篇 |
1990年 | 52篇 |
1989年 | 77篇 |
1988年 | 65篇 |
1987年 | 39篇 |
1986年 | 73篇 |
1985年 | 56篇 |
1984年 | 53篇 |
1983年 | 57篇 |
1982年 | 60篇 |
1981年 | 47篇 |
1980年 | 42篇 |
1979年 | 41篇 |
1978年 | 41篇 |
1977年 | 28篇 |
1976年 | 28篇 |
1975年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有5388条查询结果,搜索用时 17 毫秒
41.
42.
Hiroshi Kametani 《Metallurgical and Materials Transactions B》1998,29(6):1261-1267
Data concerning the length of longitudinal cracks on the surface of continuously cast steel slabs were collected from two
plants. The data were analyzed to find the relation between crack length and crack frequency. The analysis revealed the following.
相似文献
(1) |
After normalization to eliminate the effect of different casting conditions, the fractal relation characterizing the normalized
cumulative frequency distribution (N (m−2)) and the crack length (L (mm)) of the primary surface cracks could be represented by the equation |
|
(2) | The values for γ varied over a wide range, but remained constant throughout a heat and were the same for both the upper and lower faces of the slab. | |
(3) | It was found that in some instances, when L exceeded a critical value (L c), the value of L became δ times longer than the length predicted by the previous distribution. This increase in L was ascribed to secondary growth of the cracks. This occurred more frequently on the lower, rather than on the upper, face of the slab. The product of L c and δ was approximately constant. The formation of the surface cracks is discussed in view of the fractal phenomena. |
43.
C. Bäuerle N. Mori G. Kurata Hiroshi Fukuyama 《Journal of Low Temperature Physics》1998,113(5-6):927-932
Scanning tunneling microscopy (STM) studies of two-dimensional (2D) cryocrystals
4
He, Kr, Xe) physisorbed on graphite surfaces are presented. Individual helium atoms, usually thought to be invisible with STM, were recently observed on graphite surfaces at a density corresponding to the
commensurate solid. Here we show that a local elastic deformation seems to be the principal mechanism responsible to render the atoms visible. Recent tight-binding calculations of the local density of states (LDOS) of graphite which predict the appearance of an energy gap support this picture. I-z curve measurements for the case of
4
He show a sharp drop (increase) of the tunneling current I at a certain tip-surface distance z during retraction (approach) of the tip. This drop (increase) may be associated with the tunneling of a single He adatom, opening new possibilities to study the quantum tunneling of atoms via STM. 相似文献
44.
Hiroyuki Ishida Author Vitae Tomokazu Takahashi Author Vitae Author Vitae Hiroshi Murase Author Vitae 《Pattern recognition》2010,43(8):2799-2806
We propose a novel sequence alignment algorithm for recognizing handwriting gestures by a camera. In the proposed method, an input image sequence is aligned to the reference sequences by phase-synchronization of analytic signals which are transformed from original feature values. A cumulative distance is calculated simultaneously with the alignment process, and then used for the classification. A major benefit of this method is that over-fitting to sequences of incorrect categories is restricted. The proposed method exhibited higher recognition accuracy in handwriting gesture recognition, compared with the conventional dynamic time warping method which explores optimal alignment results for all categories. 相似文献
45.
Tsuji S Kasumi T Nagase K Yoshikawa E Kobayashi H Kurita N 《Journal of molecular graphics & modelling》2011,29(8):975-984
During cancer invasion, the binding of urokinase-type plasminogen activator (uPA) to its receptor (uPAR) on the surface of a cancer cell is considered a trigger for invasion. Here, we present a stable structure of the solvated complex formed between uPA and uPAR (uPA-uPAR) and investigate the specific interactions between uPA and uPAR by ab initio fragment molecular orbital (FMO) calculations. The result indicates that the electrostatic interactions between the charged amino acid residues existing in both uPA and uPAR make a large contribution to the binding between uPA and uPAR. In particular, Lys23, Lys46, Lys98 and Lys61 of uPA are found to have strong attractive interactions with uPAR. To elucidate the effect of these residues on the interactions between uPA and uPAR, we substituted each of them with the uncharged amino acid Leu and investigated the interactions between the mutated uPA and wild-type uPAR. The interaction energies indicate that Lys46 and Lys98, which bind uPA to the rim of the central ligand-binding cavity of uPAR, make greater contributions to the binding between uPA and uPAR than Lys23, which is positioned at the bottom of the ligand-binding cavity of uPAR. The effect of hydrating water molecules located between uPA and uPAR is also investigated to be significant for the specific interactions between uPA and uPAR. These results are expected to be informative for developing new peptide antagonists that block the binding of uPA to uPAR. 相似文献
46.
Hybrid Petri net (HPN) is an extension of the Petri net formalism, which enables us to handle continuous information in addition
to discrete information. Firstly, this paper demonstrates how biological pathways can be modeled by the integration of discrete
and continuous elements, with an example of the λ phage genetic switch system including induction and retroregulation mechanisms.
Although HPN allows intuitive modeling of biological pathways, some fundamental biological processes such as complex formation
cannot be represented with HPN. Thus, this paper next provides the formal definition of hybrid functional Petri net with extension
(HFPNe), which has high potential for modeling various kinds of biological processes. Cell Illustrator is a software tool
developed on the basis of the definition of HFPNe. Hypothesis creation by Cell Illustrator is demonstrated with the example
of the cyanobacterial circadian gene clock system. Finally, our ongoing tasks, which include the development of a computational
platform for systems biology, are presented. 相似文献
47.
We study a crossing minimization problem of drawing a bipartite graph with a radial drawing of two orbits. Radial drawings are one of well-known drawing conventions in social network analysis and visualization, in
particular, displaying centrality indices of actors (Wasserman and Faust, Social Network Analysis: Methods and Applications. Cambridge University Press, Cambridge,
1994). The main problem in this paper is called the one-sided radial crossing minimization, if the positions of vertices in the outer orbit are fixed. The problem is known to be NP-hard (Bachmaier, IEEE Trans. Vis.
Comput. Graph. 13, 583–594, 2007), and a number of heuristics are available (Bachmaier, IEEE Trans. Vis. Comput. Graph. 13, 583–594, 2007). However, there is no approximation algorithm for the crossing minimization problem in radial drawings. We present the first polynomial time constant-factor approximation algorithm for the one-sided radial crossing minimization problem. 相似文献
48.
49.
This study addresses the optimal changes in geometry of a two-dimensional variable geometry truss (VGT) to identify the stiffness matrix of the truss using the concept of self-identification. The optimization of the geometry changing of the VGT is a problem of selecting the optimal combination of multiple design variables from a large number of candidate sets. This study proposes a simple optimization method for determining a set of optimal geometric parameters; in this method, the approximated mode shape matrix obtained using spline interpolation techniques is used to calculate the objective function for self-identification. The objective function used in this paper is a function of the condition number of the coefficient matrix of a linear matrix equation and a criterion for self-identification. The proposed algorithm can be used to reduce the number of actual vibration tests required for measuring the mode shapes and modal frequency while it maximizes the objective function. Numerical experiments are conducted to investigate the relationship between the convergence characteristics of the optimization and the target vibration modes. The effectiveness of the optimized geometry changing is verified by comparing the identification error for the uniform geometry changing, the optimized one for the three lower modes of the VGT, and the one found by a classical QR decomposition. Furthermore, the numerical results show that the identification sensitivity with respect to noisy data is reduced by the optimization. 相似文献
50.
Recently, various techniques of shape reconstruction using cast shadows have been proposed. These techniques have the advantage
that they can be applied to various scenes, including outdoor scenes, without using special devices. Previously proposed techniques
usually require calibration of camera parameters and light source positions, and such calibration processes limit the range
of application of these techniques. In this paper, we propose a method to reconstruct 3D scenes even when the camera parameters
or light source positions are unknown. The technique first recovers the shape with 4-DOF indeterminacy using coplanarities
obtained by cast shadows of straight edges or visible planes in a scene, and then upgrades the shape using metric constraints
obtained from the geometrical constraints in the scene. In order to circumvent the need for calibrations and special devices,
we propose both linear and nonlinear methods in this paper. Experiments using simulated and real images verified the effectiveness
of this technique. 相似文献