全文获取类型
收费全文 | 2352篇 |
免费 | 91篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 40篇 |
综合类 | 1篇 |
化学工业 | 425篇 |
金属工艺 | 53篇 |
机械仪表 | 53篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 121篇 |
轻工业 | 83篇 |
水利工程 | 15篇 |
石油天然气 | 39篇 |
无线电 | 522篇 |
一般工业技术 | 411篇 |
冶金工业 | 176篇 |
原子能技术 | 14篇 |
自动化技术 | 459篇 |
出版年
2023年 | 35篇 |
2022年 | 96篇 |
2021年 | 82篇 |
2020年 | 59篇 |
2019年 | 60篇 |
2018年 | 92篇 |
2017年 | 75篇 |
2016年 | 66篇 |
2015年 | 68篇 |
2014年 | 79篇 |
2013年 | 177篇 |
2012年 | 106篇 |
2011年 | 98篇 |
2010年 | 108篇 |
2009年 | 78篇 |
2008年 | 80篇 |
2007年 | 77篇 |
2006年 | 72篇 |
2005年 | 67篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 55篇 |
2001年 | 31篇 |
2000年 | 45篇 |
1999年 | 39篇 |
1998年 | 70篇 |
1997年 | 50篇 |
1996年 | 36篇 |
1995年 | 41篇 |
1994年 | 42篇 |
1993年 | 38篇 |
1992年 | 23篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 9篇 |
排序方式: 共有2449条查询结果,搜索用时 15 毫秒
81.
Katharina N?ske Hans-Jürgen Stark Leonard Nevaril Manuel Berning Lutz Langbein Ashish Goyal Sven Diederichs Petra Boukamp 《International journal of molecular sciences》2016,17(2)
Despite decades of skin research, regulation of proliferation and homeostasis in human epidermis is still insufficiently understood. To address the role of mitoses in tissue regulation, we utilized human long-term skin equivalents and systematically assessed mitoses during early epidermal development and long-term epidermal regeneration. We now demonstrate four different orientations: (1) horizontal, i.e., parallel to the basement membrane (BM) and suggestive of symmetric divisions; (2) oblique with an angle of 45°–70°; or (3) perpendicular, suggestive of asymmetric division. In addition, we demonstrate a fourth substantial fraction of suprabasal mitoses, many of which are committed to differentiation (Keratin K10-positive). As verified also for normal human skin, this spatial mitotic organization is part of the regulatory program of human epidermal tissue homeostasis. As a potential marker for asymmetric division, we investigated for Numb and found that it was evenly spread in almost all undifferentiated keratinocytes, but indeed asymmetrically distributed in some mitoses and particularly frequent under differentiation-repressing low-calcium conditions. Numb deletion (stable knockdown by CRISPR/Cas9), however, did not affect proliferation, neither in a three-day follow up study by life cell imaging nor during a 14-day culture period, suggesting that Numb is not essential for the general control of keratinocyte division. 相似文献
82.
J. Menghani S. K. Agrawal Vikram Agarwal Dhaval Bhatt 《Transactions of the Indian Institute of Metals》2012,65(1):107-109
Reduced weight of automobiles for the purpose of fuel economy has encouraged the use of light metals especially aluminium
alloys. A356 Al alloy containing 7% Si and 0.3% Mg is widely used in automobile and aircraft industries due to excellent castability,
good corrosion resistance and good pressure tightness. A356 is age hardenable alloy and there is appreciable improvement in
strength and hardness achievable due to precipitation of intermetallic compound Mg2Si. In the present investigation, aluminium alloy A356 with and without rare earth (RE) addition (0.5 wt%) was subjected to
single ageing as well as double aging treatment. The results were compared for mechanical properties like hardness and ultimate
tensile strength with the material not containing RE additions. 相似文献
83.
84.
85.
86.
A method of extraction of source and drain resistances in linear mode of operation from a single transistor is described. The proposed method can also be used to measure source resistance over the entire operating range from linear to saturation mode of operation. The method uses two floating probes outside the channel, one adjacent to the source and the other to the drain to sense the voltage under these contacts. Using transmission line analysis, the source and drain resistances are directly extracted from these measurements. 2D numerical simulation results confirm the validity of the proposed technique and sensitivity analysis shows that the method is more accurate than the conventional gated four probe technique, especially, when the source resistance is much smaller than the channel resistance. Experimental results obtained with Pentacene top-contact transistors are used to illustrate the proposed technique. Analysis of two devices with very different source resistance is carried out to highlight the ability of the proposed technique to offer insight into the different contributing factors. Current crowding under the source contact and accurate estimation of mobility without the distorting effects of source resistance are also described. 相似文献
87.
Singh Chitranjan Prasad Agrawal Hemant Mishra Arvind Kumar 《Bulletin of Engineering Geology and the Environment》2021,80(10):8009-8019
Bulletin of Engineering Geology and the Environment - Vibrations induced due to blasting in mines may damage the nearby houses and disturb the habitants. The monitoring, prediction, and control of... 相似文献
88.
89.
Puneet Negi H. M. Agrawal Jitendra Pal Singh Hemaunt Kumar R. C. Srivastava K. Asokan Keun Hwa Chae 《Journal of Superconductivity and Novel Magnetism》2017,30(6):1419-1425
The present study deals with the investigation of magnetic properties along with morphological and microstructure analyses of a multiferroic GdMnO3 film fabricated on Si(100) substrate by the pulsed laser deposition technique. Rutherford backscattering spectroscopic analysis suggests that the film is fabricated in the form of diffused layers having different stoichiometric proportions. Raman spectroscopy signifies that few modes present in the film are associated with MnO6 octahedra and some extra peaks indicating the mixed phase formation in tuning with the Rutherford backscattering spectroscopy. Atomic force microscopy confirms the granular nature of the film. Field-cooled and zero-field-cooled thermal magnetization curves show irreversible behaviour extending well above room temperature, which is associated with spin disorder. The presence of Gd+3 state and Mn+3/Mn+4 mixed states in the uppermost layers of the film was confirmed by near-edge X-ray absorption fine structure. Subsequently, in association with these observations, the film is a weak ferromagnetic at 5 K and even at room temperature. 相似文献
90.
3D Numerical study of temperature variation for subsonic rarefied gas flow in a microchannel is carried out using an in-house MPI-based parallelized DSMC code. The temperature drop in the microchannel decreases with an increase in the aspect ratio whereas it increases with an increase in the pressure ratio, the cross-aspect ratio (CAR), and the Knudsen number. 3D and 2D simulations results are compared and effect of the CAR and Knudsen number are brought out. Finally, a correlation that predicts the temperature drop is formulated along with a list of conditions that ensures a near isothermal flow. 相似文献