全文获取类型
收费全文 | 3760篇 |
免费 | 64篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 142篇 |
综合类 | 3篇 |
化学工业 | 652篇 |
金属工艺 | 68篇 |
机械仪表 | 73篇 |
建筑科学 | 47篇 |
矿业工程 | 1篇 |
能源动力 | 118篇 |
轻工业 | 295篇 |
水利工程 | 9篇 |
石油天然气 | 16篇 |
无线电 | 381篇 |
一般工业技术 | 513篇 |
冶金工业 | 1246篇 |
原子能技术 | 81篇 |
自动化技术 | 183篇 |
出版年
2023年 | 18篇 |
2022年 | 25篇 |
2021年 | 43篇 |
2020年 | 24篇 |
2019年 | 27篇 |
2018年 | 36篇 |
2017年 | 46篇 |
2016年 | 51篇 |
2015年 | 33篇 |
2014年 | 60篇 |
2013年 | 138篇 |
2012年 | 109篇 |
2011年 | 110篇 |
2010年 | 106篇 |
2009年 | 99篇 |
2008年 | 108篇 |
2007年 | 112篇 |
2006年 | 96篇 |
2005年 | 79篇 |
2004年 | 81篇 |
2003年 | 101篇 |
2002年 | 69篇 |
2001年 | 80篇 |
2000年 | 81篇 |
1999年 | 135篇 |
1998年 | 472篇 |
1997年 | 262篇 |
1996年 | 207篇 |
1995年 | 120篇 |
1994年 | 117篇 |
1993年 | 118篇 |
1992年 | 62篇 |
1991年 | 57篇 |
1990年 | 49篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 34篇 |
1986年 | 38篇 |
1985年 | 40篇 |
1984年 | 31篇 |
1983年 | 35篇 |
1982年 | 21篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 23篇 |
1977年 | 27篇 |
1976年 | 52篇 |
1974年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有3828条查询结果,搜索用时 15 毫秒
21.
S Ohkawa A Yamadori K Maeda M Tabuchi Y Ohsumi E Mori T Yoshida Y Yoneda T Uehara 《Canadian Metallurgical Quarterly》1993,56(8):894-896
In right middle cerebral territory infarction a new sign, excessive closure of the right eye ipsilateral to the lesion and mild closure of the left eye on command, was noted. The excessive ipsilateral eye closure was not observed on spontaneous eye closure. 相似文献
22.
23.
Wakabayashi H. Ueki M. Narihiro M. Fukai T. Ikezawa N. Matsuda T. Yoshida K. Takeuchi K. Ochiai Y. Mogami T. Kunio T. 《Electron Devices, IEEE Transactions on》2002,49(1):89-95
Sub-50-nm CMOS devices are investigated using steep halo and shallow source/drain extensions. By using a high-ramp-rate spike annealing (HRR-SA) process and high-dose halo, 45-nm CMOS devices are fabricated with drive currents of 650 and 300 μA/μm for an off current of less than 10 nA/μm at 1.2 V with Toxinv =2.5 nm. For an off current less than 300 nA/μm, 33-nm pMOSFETs have a high drive current of 400 uA/μm. Short-channel effect and reverse short-channel effect are suppressed simultaneously by using the HRR-SA process to activate a source/drain extension (SDE) after forming a deep source/drain (S/D). This process sequence is defined as a reverse-order S/D (R-S/D) formation. By using this formation, 24-nm nMOSFETs are achieved with a high drive current of 800 μA/μm for an off current of less than 300 μA/μm at 1.2 V. This high drive current might be a result of a steep halo structure reducing the spreading resistance of source/drain extensions 相似文献
24.
S Maeshima T Terada N Yoshida K Nakai T Itakura N Komai 《Canadian Metallurgical Quarterly》1997,78(6):666-669
A mechanical computerized three-dimensional scanner with a resolution of 1 micron was used to assess loss of enamel caused by orthodontic bonding and debonding. A total of 2646 measurements was performed on six human premolars. The results showed an average loss of enamel of 7.4 microns. The range was between 1 and 52 microns, which may account for discrepancies with earlier studies that measured only a few points per tooth surface. 相似文献
25.
XIII. Yeast sequencing reports. Cloning and sequencing of the NES24 gene of Saccharomyces cerevisiae
We have cloned NES24 using a temperature-sensitive nes24-1 mutant as a host and sequenced a 3162 bp XhoI-EcoRI DNA fragment containing the NES24 gene. Computer analysis revealed that this segment contains a 1806 bp open reading frame which is needed for complementation of the nes24-1 mutation. We found SUP8 in the region upstream of the NES24 gene, placing the NES24 gene on chromosome XIII. A protein homology search indicated that NES24 encodes a new protein. The disruption of the NES24 gene resulted in temperature-sensitive growth. The sequence has been deposited in DDBJ/EmBL/GenBank data bases under Accession Number D15052. 相似文献
26.
Neural network approach to land cover mapping 总被引:3,自引:0,他引:3
A pattern classification method is proposed for remote sensing data using neural networks. First, the authors apply the error backpropagation (BP) algorithm to classify the remote sensing data. In this case, the classification performance depends on a training data set. In order to get stable and precise classification results, the training data set is selected based on geographical information and Kohonen's self-organizing feature map. Using the training data set and the error backpropagation algorithm, a layered neural network is trained such that the training patterns are classified with a specified accuracy. After training the neural network, some pixels are deleted from the original training data set if they are incorrectly classified and a new training data set is built up. Once training is complete, a testing data set is classified by using the trained neural network. The classification results of LANDSAT TM data show that this approach produces excellent results which are more realistic and noiseless compared with a conventional Bayesian method 相似文献
27.
T Yoshida M Satoh Y Nakagaito H Kuno M Takeuchi 《Canadian Metallurgical Quarterly》1993,76(1):147-150
The effects of various cytokines on survival and differentiation of an astrocyte progenitor cell line (AP-16) were examined. Epidermal growth factor (EGF) deprivation caused death of AP-16 cells by apoptosis. Transforming growth factor-alpha (TGF-alpha) and basic fibroblast growth factor (bFGF) prevented the apoptosis occurring in the absence of EGF. Leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) induced glial fibrillary acidic protein (GFAP) and decreased A2B5 antigen in AP-16 cells, indicating that these cytokines induced AP-16 cells to differentiate into astrocytes. 相似文献
28.
29.
30.
Nakamura K. Kuhara S. Kimura T. Takada M. Suzuki H. Yoshida H. Yamazaki T. 《Solid-State Circuits, IEEE Journal of》1994,29(11):1317-1322
This 512 Kw×8 b×3 way synchronous BiCMOS SRAM uses a 2-stage wave-pipeline scheme, a PLL self-timing generator and a 0.4-μm BiCMOS process to achieve 220 MHz fully-random read/write operations with a GTL I/O interface. Newly developed circuit technologies include: 1) a zig-zag double word-line scheme, 2) a centered bit-line load layout scheme, and 3) a phase-locked-loop (PLL) with a multistage-tapped ring oscillator which generates a clock cycle proportional pulse (CCPP) and a clock edge lookahead pulse (CELP) 相似文献