全文获取类型
收费全文 | 1497篇 |
免费 | 71篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 18篇 |
综合类 | 3篇 |
化学工业 | 333篇 |
金属工艺 | 34篇 |
机械仪表 | 66篇 |
建筑科学 | 54篇 |
矿业工程 | 5篇 |
能源动力 | 60篇 |
轻工业 | 85篇 |
水利工程 | 22篇 |
石油天然气 | 5篇 |
无线电 | 233篇 |
一般工业技术 | 237篇 |
冶金工业 | 137篇 |
原子能技术 | 10篇 |
自动化技术 | 274篇 |
出版年
2023年 | 21篇 |
2022年 | 52篇 |
2021年 | 75篇 |
2020年 | 62篇 |
2019年 | 63篇 |
2018年 | 59篇 |
2017年 | 53篇 |
2016年 | 107篇 |
2015年 | 47篇 |
2014年 | 61篇 |
2013年 | 113篇 |
2012年 | 99篇 |
2011年 | 102篇 |
2010年 | 73篇 |
2009年 | 67篇 |
2008年 | 54篇 |
2007年 | 47篇 |
2006年 | 34篇 |
2005年 | 36篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 45篇 |
1997年 | 35篇 |
1996年 | 17篇 |
1995年 | 20篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有1576条查询结果,搜索用时 31 毫秒
11.
The authors present an adaptive space-time reduced-length minimum mean-squared error (MMSE) receiver to suppress co-channel interference in the near-far environment for an asynchronous direct-sequence code-division multiple-access (DS/CDMA) system. Simulation results show that better bit-error rate and faster and more stable convergence are achieved over the existing full- and reduced-length MMSE receivers 相似文献
12.
13.
14.
Yi Fang Vu Anh Pham Takeshi Matsuura J. P. Santerre Roberto M. Narbaitz 《应用聚合物科学杂志》1994,54(12):1937-1943
Polyethersulfone (PES) membranes using different evaporation periods were fabricated by the phase-inversion method. Pervaporation experiments were conducted for chloroform/water mixtures to determine the selectivity of the PES membranes. It was found that chloroform could be concentrated in the permeate from chloroform/water binary feed mixtures by PES membranes prepared using longer evaporation periods, and that the selectivity of PES membranes in pervaporation could be reversed by shorter evaporation periods. This study also showed that by adding surface-modifying macromolecules (SMM) up to 1 wt % into the casting solution, chloroform enrichment in the permeate could be increased by 50%. Chloroform enrichment increased with increasing SMM concentration until an optimal value, after which the enrichment decreased. © 1994 John Wiley & Sons, Inc. 相似文献
15.
Krivelevich M. Sudakov B. Vu V.H. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(7):1812-1815
We prove a general recursive inequality concerning /spl mu//sup */(R), the asymptotic (least) density of the best binary covering codes of radius R. In particular, this inequality implies that /spl mu//sup */(R)/spl les/e/spl middot/(RlogR+logR+loglogR+2), which significantly improves the best known density 2/sup R/R/sup R/(R+1)/R!. Our inequality also holds for covering codes over arbitrary alphabets. 相似文献
16.
We propose a method for non-uniform reconstruction of 3D scalar data. Typically, radial basis functions, trigonometric polynomials or shift-invariant functions are used in the functional approximation of 3D data. We adopt a variational approach for the reconstruction and rendering of 3D data. The principle idea is based on data fitting via thin-plate splines. An approximation by B-splines offers more compact support for fast reconstruction. We adopt this method for large datasets by introducing a block-based reconstruction approach. This makes the method practical for large datasets. Our reconstruction will be smooth across blocks. We give reconstruction measurements as error estimations based on different parameter settings and also an insight on the computational effort. We show that the block size used in reconstruction has a negligible effect on the reconstruction error. Finally we show rendering results to emphasize the quality of this 3D reconstruction technique. 相似文献
17.
18.
Thi Kieu Oanh Nguyen Thi Luong Vu Minh Quan Nguyen Huynh Kim Khanh Ta Kyoung Sun Park Soo Hyeon Kim Chong Jai Kim Yeon Jin Jang Han Choe 《International journal of molecular sciences》2021,22(10)
Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a member of the colony-stimulating factor (CSF) family, which functions to enhance the proliferation and differentiation of hematopoietic stem cells and other hematopoietic lineages such as neutrophils, dendritic cells, or macrophages. These proteins have thus generated considerable interest in clinical therapy research. A current obstacle to the prokaryotic production of human GM-CSF (hGM-CSF) is its low solubility when overexpressed and subsequent complex refolding processes. In our present study, the solubility of hGM-CSF was examined when combined with three N-terminal fusion tags in five E. coli strains at three different expression temperatures. In the five E. coli strains BL21 (DE3), ClearColi BL21 (DE3), LOBSTR, SHuffle T7 and Origami2 (DE3), the hexahistidine-tagged hGM-CSF showed the best expression but was insoluble in all cases at each examined temperature. Tagging with the maltose-binding protein (MBP) and the b′a′ domain of protein disulfide isomerase (PDIb′a′) greatly improved the soluble overexpression of hGM-CSF at 30 °C and 18 °C. The solubility was not improved using the Origami2 (DE3) and SHuffle T7 strains that have been engineered for disulfide bond formation. Two conventional chromatographic steps were used to purify hGM-CSF from the overexpressed PDIb′a′-hGM-CSF produced in ClearColi BL21 (DE3). In the experiment, 0.65 mg of hGM-CSF was isolated from a 0.5 L flask culture of these E. coli and showed a 98% purity by SDS-PAGE analysis and silver staining. The bioactivity of this purified hGM-CSF was measured at an EC50 of 16.4 ± 2 pM by a CCK8 assay in TF-1 human erythroleukemia cells. 相似文献
19.
B. M. Khusid B. B. Khina Vu Zui Kuang E. A. Bashtovaya 《Combustion, Explosion, and Shock Waves》1992,28(4):389-395
The quenching of a SHS sample under conditions of intense heat removal from the outer surface was investigated numerically. A two-step reaction was considered. The reaction proceeds in the reginmes of blending, control, and takeoff. It was established that in the control and takeoff regimes a significant amount of an intermediate phase is fixed during quenching. In the blending regime the relative fraction of the intermediate product in the quenched sample is small. It is shown that the method of quenching with an impacting water jet can be used to investigate phase-and structure-formation processes during SHS.Minsk Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 4, pp. 76–82, July–August, 1992. 相似文献
20.
The mobile wireless market has been attracting many customers. Technically, the paradigm of anytime-anywhere connectivity raises previously unthinkable challenges, including the management of million of mobile customers, their profiles, the profiles-based selective information dissemination, and server-side computing infrastructure design issues to support such a large pool of users automatically and intelligently. In this paper, we propose a data mining technique for discovering frequent behavioral patterns from a collection of trajectories gathered by Global Positioning System. Although the search space for spatiotemporal knowledge is extremely challenging, imposing spatial and temporal constraints on spatiotemporal sequences makes the computation feasible. Specifically, the mined patterns are incorporated with synthetic constraints, namely spatiotemporal sequence length restriction, minimum and maximum timing gap between events, time window of occurrence of the whole pattern, inclusion or exclusion event constraints, and frequent movement patterns predictive of one ore more classes. The algorithm for mining all frequent constrained patterns is named cAllMOP. Moreover, to control the density of pattern regions a clustering algorithm is exploited. The proposed method is efficient and scalable. Its efficiency is better than that of the previous algorithms AllMOP and GSP with respect to the compactness of discovered knowledge, execution time, and memory requirement. 相似文献