全文获取类型
收费全文 | 28846篇 |
免费 | 1520篇 |
国内免费 | 128篇 |
专业分类
电工技术 | 468篇 |
综合类 | 233篇 |
化学工业 | 4820篇 |
金属工艺 | 790篇 |
机械仪表 | 660篇 |
建筑科学 | 786篇 |
矿业工程 | 148篇 |
能源动力 | 501篇 |
轻工业 | 3990篇 |
水利工程 | 210篇 |
石油天然气 | 135篇 |
武器工业 | 10篇 |
无线电 | 1522篇 |
一般工业技术 | 5292篇 |
冶金工业 | 7306篇 |
原子能技术 | 164篇 |
自动化技术 | 3459篇 |
出版年
2023年 | 300篇 |
2022年 | 261篇 |
2021年 | 608篇 |
2020年 | 502篇 |
2019年 | 426篇 |
2018年 | 904篇 |
2017年 | 814篇 |
2016年 | 898篇 |
2015年 | 777篇 |
2014年 | 907篇 |
2013年 | 1731篇 |
2012年 | 1336篇 |
2011年 | 1342篇 |
2010年 | 1139篇 |
2009年 | 1087篇 |
2008年 | 1221篇 |
2007年 | 1168篇 |
2006年 | 828篇 |
2005年 | 664篇 |
2004年 | 487篇 |
2003年 | 451篇 |
2002年 | 418篇 |
2001年 | 331篇 |
2000年 | 322篇 |
1999年 | 448篇 |
1998年 | 2282篇 |
1997年 | 1373篇 |
1996年 | 960篇 |
1995年 | 580篇 |
1994年 | 471篇 |
1993年 | 427篇 |
1992年 | 171篇 |
1991年 | 179篇 |
1990年 | 153篇 |
1989年 | 158篇 |
1988年 | 150篇 |
1987年 | 159篇 |
1986年 | 138篇 |
1985年 | 217篇 |
1984年 | 180篇 |
1983年 | 165篇 |
1982年 | 131篇 |
1981年 | 175篇 |
1980年 | 172篇 |
1979年 | 121篇 |
1978年 | 105篇 |
1977年 | 222篇 |
1976年 | 480篇 |
1975年 | 85篇 |
1973年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
932.
B. Nagy Y. N. Khaydukov L. F. Kiss S. Sajti D. G. Merkel F. Tanczikó A. S. Vasenko R. O. Tsaregorodsev A. Rühm T. Keller L. Bottyán 《Journal of Superconductivity and Novel Magnetism》2013,26(5):1957-1961
The thickness (d F) and concentration (x) dependence of the Curie temperature of Ni x Cu1?x (d F) ferromagnetic alloy layers (x=0.55, 0.65, d F=[4.5 nm÷12 nm]) in contact with a vanadium layer was studied. The Curie temperature of the ferromagnetic layers depends on the thickness when it is comparable with the transition layer between the F and the vanadium layers, which is attributed to the proximity coupling of the interface region with the rest of the F layer. The present study provides valuable information for fabrication of samples with controlled exchange coupling strength for studies of superconductor/ferromagnet proximity effects. 相似文献
933.
A. Bükki-Deme C.G. Alecu B. Kloppe B. Bornschein 《Fusion Engineering and Design》2013,88(11):2865-2869
At Tritium Laboratory Karlsruhe (TLK) calorimetry has been used for almost 20 years as the main accountancy method for tritium inventory. An extensive work has been carried out in order to improve the existing calorimeters. This paper covers the efforts made for the upgrade of the IGC-V0.5 calorimeter. We replaced the hardware interface – including the obsolete PC – and developed a new control and data acquisition software. The new software applies a smart automatic process control during measurements, significantly reducing measurement time and possible user errors. The three PID control loops have been re-tuned using the standard closed loop Ziegler–Nichols procedure to find the optimal PID parameters. Five calibration runs have been performed between 0.5 μW and 1 W, and their results are being presented and discussed. 相似文献
934.
Per Weslien Tobias Rütting ?sa Kasimir-Klemedtsson Leif Klemedtsson 《Nutrient Cycling in Agroecosystems》2012,94(2-3):249-253
The emissions of the greenhouse gas nitrous oxide (N2O) were measured from a non nitrogen fertilized carrot (Daucus carota ssp. sativa) field on an organic soil in Sweden during one cropping and post-harvest season. The cumulative emission during the measuring period of 149?days was 41 (±2.8) kg N2O ha?1. Dividing the measuring period into a cropping and a post-harvest period revealed that the presence of carrots strongly stimulated N2O emissions, as the emission during the cropping period was one order of magnitude higher compared to the post-harvest period. The N2O emission from the carrot field were higher than fluxes reported from cereal crop and grass production, but in the same order as reported fluxes from vegetable cropping on organic soils. In conclusion, our results indicate that the cultivation of root vegetable, such as carrots, on organic soil can be a high point source for N2O emissions. 相似文献
935.
Eva Hoch Christian Schuh Thomas Hirth Günter E. M. Tovar Kirsten Borchers 《Journal of materials science. Materials in medicine》2012,23(11):2607-2617
Gelatin is a very promising matrix material for in vitro cell culture and tissue engineering, e.g. due to its native RGD content. For the generation of medical soft tissue implants chemical modification of gelatin improves the mechanical properties of gelatin hydrogels and the viscous behavior of gelatin solutions for liquid handling. We present a systematic study on the influence of high degrees of methacrylation on the properties of gelatin solutions and photo-chemically crosslinked hydrogels. Changes from shear thinning to shear thickening behavior of gelatin solutions were observed depending on mass fraction and degree of methacrylation. Degrees of swelling of crosslinked hydrogels ranged from 194 to 770?% and storage moduli G′ from 368 to 5?kPa, comparable to various natural tissues including several types of cartilage. Crosslinked gels proofed to be cytocompatible according to extract testings based on DIN ISO 10933-5 and in contact with porcine chondrocytes. 相似文献
936.
937.
938.
M. Hübner J.-E. Rocher S. Allaoui G. Hivet T. Gereke C. Cherif 《International Journal of Material Forming》2016,9(5):591-599
Composites based on 3D woven fabrics offer excellent mechanical properties due to the nearly non-crimp reinforcement fibers. Additionally, a reduced number of process steps results from the 3D nature of the reinforcement. Their in-plane and out-of-plane behaviors are purposefully adjustable to the expected loading conditions. A previously introduced modelling approach is extended to the simulation of 3D woven fabrics. The tensile, shear and bending behaviors of the fabric are considered in a material formulation for large deformations using shell elements. The model is successfully validated and parameter studies show the significant influence of shear and bending parameters on forming results. Furthermore, it is shown that also the forming process parameters have a significant influence on the draping results. It is concluded that the shearing and wrinkling can be reduced to a minimum with adapted material and process parameters. 相似文献
939.
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
940.
Neural Computing and Applications - In this paper, we consider a system of nonlinear delay integro-differential equations with convolution kernels, which arises in biology. This problem... 相似文献