全文获取类型
收费全文 | 28109篇 |
免费 | 2435篇 |
国内免费 | 1430篇 |
专业分类
电工技术 | 1748篇 |
技术理论 | 1篇 |
综合类 | 1989篇 |
化学工业 | 4652篇 |
金属工艺 | 1459篇 |
机械仪表 | 1791篇 |
建筑科学 | 2175篇 |
矿业工程 | 911篇 |
能源动力 | 770篇 |
轻工业 | 2491篇 |
水利工程 | 543篇 |
石油天然气 | 1810篇 |
武器工业 | 206篇 |
无线电 | 2800篇 |
一般工业技术 | 2985篇 |
冶金工业 | 1320篇 |
原子能技术 | 320篇 |
自动化技术 | 4003篇 |
出版年
2024年 | 144篇 |
2023年 | 508篇 |
2022年 | 896篇 |
2021年 | 1206篇 |
2020年 | 871篇 |
2019年 | 747篇 |
2018年 | 849篇 |
2017年 | 939篇 |
2016年 | 829篇 |
2015年 | 1115篇 |
2014年 | 1484篇 |
2013年 | 1801篇 |
2012年 | 1875篇 |
2011年 | 2147篇 |
2010年 | 1836篇 |
2009年 | 1770篇 |
2008年 | 1789篇 |
2007年 | 1617篇 |
2006年 | 1543篇 |
2005年 | 1384篇 |
2004年 | 923篇 |
2003年 | 758篇 |
2002年 | 715篇 |
2001年 | 625篇 |
2000年 | 614篇 |
1999年 | 584篇 |
1998年 | 450篇 |
1997年 | 413篇 |
1996年 | 349篇 |
1995年 | 287篇 |
1994年 | 257篇 |
1993年 | 170篇 |
1992年 | 147篇 |
1991年 | 83篇 |
1990年 | 66篇 |
1989年 | 38篇 |
1988年 | 48篇 |
1987年 | 28篇 |
1986年 | 15篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Let G1 and G2 be two connected graphs. The Kronecker product G1×G2 has vertex set V(G1×G2)=V(G1)×V(G2) and the edge set . In this paper, we show that if G is a bipartite graph with κ(G)=δ(G), then G×Kn(n?3) is super-κ. 相似文献
42.
43.
A system-level model with lumped parameters for a thermal flow sensor is presented. The model is built with 13 circuit cells
consisting of thermal resistors and thermal capacitors in SPICE. The circuit cell originates from the heat conduction equation
using the Finite Differential Method, including the 2-D thermal conduction cell, the convection cell, and the thermal capacity
in the chip. Based on the thermal model of the flow sensor, the 2-D temperature distribution of the chip can be calculated
with SPICE in both the constant power mode (CP) and constant temperature difference mode (CTD). As an example, the system
level model of the thermal anemometer in the CTD mode was established in PSPICE. Wind tunnel test was carried out to verify
the system model, and show a reasonable agreement with the simulation results, with an error less than 8%. 相似文献
44.
45.
To deal with the planarization problem widely used in many applications including routing very-large-scale integration (VLSI) circuits, this paper points out that only when its vertices are arranged in some specific order in a line can a planar graph be embedded on a line without any cross connections or cross edges. Energy function is proposed to meet the need of embedding a graph on a single line and route it correctly. A Hopfield network is designed according to the proposed energy function for such embedding and routing. The advantage of the proposed method is that it not only can detect if a graph is a planar one or not, but also can embed a planar graph or the maximal planar subgraph of a non-planar graph on a single line. In addition, simulated annealing is employed for helping the network to escape from local minima during the running of the Hopfield network. Experiments of the proposed method and its comparison with some existent conventional methods were performed and the results indicate that the proposed method is of great feasibility and effectiveness especially for the planarization problem of large graphs. 相似文献
46.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity. 相似文献
47.
The prototype of a CO2 sensor made of CuO–BaTiO3, which has capacitance sensitive effect, is designed based on the pn heterojunctions of CuO and BaTiO3 semiconductors. The preparation of BaTiO3 semiconductor powders is pointed out, using the coprecipitation and semiconducting techniques. The characteristic quantities relating to the capacitance sensitive effect of the sensor are studied systematically with the aid of a gas tester. A reasonable mechanism of the sensor is proposed. 相似文献
48.
49.
50.
Acoustic emission (AE) experiments have been performed on gas-saturated coal specimens under conventional triaxial compression. The AE characteristics were investigated for a methane gas flow through the coal specimen. One AE parameter, AE count, when normalized by the total count number was used to represent the damage evolution in the gassy coal. It is shown that this AE parameter is a reasonable indicator for damage occurring within the coal specimen since its envelope has almost the same shape as the complete stress–strain curve, except for a short time delay. In addition, the change in AE count is highly consistent with the change in coal permeability. Test results also show that methane containing coal emits a small number of AE events before entering the yield stage. AE activity gradually increases during the yield process up to the peak stress. The lowest permeability corresponds to the highest AE activity, implying failure will soon occur. An AE based constitutive model was constructed and the theoretical results agree well with those of experiments. 相似文献