全文获取类型
收费全文 | 203623篇 |
免费 | 2461篇 |
国内免费 | 652篇 |
专业分类
电工技术 | 4175篇 |
综合类 | 127篇 |
化学工业 | 28047篇 |
金属工艺 | 7742篇 |
机械仪表 | 5844篇 |
建筑科学 | 4149篇 |
矿业工程 | 749篇 |
能源动力 | 4986篇 |
轻工业 | 14874篇 |
水利工程 | 1715篇 |
石油天然气 | 2848篇 |
武器工业 | 9篇 |
无线电 | 28204篇 |
一般工业技术 | 38756篇 |
冶金工业 | 45670篇 |
原子能技术 | 3617篇 |
自动化技术 | 15224篇 |
出版年
2021年 | 1408篇 |
2020年 | 1077篇 |
2019年 | 1418篇 |
2018年 | 2311篇 |
2017年 | 2286篇 |
2016年 | 2377篇 |
2015年 | 1645篇 |
2014年 | 2878篇 |
2013年 | 8302篇 |
2012年 | 4897篇 |
2011年 | 6606篇 |
2010年 | 5278篇 |
2009年 | 6168篇 |
2008年 | 6504篇 |
2007年 | 6483篇 |
2006年 | 5850篇 |
2005年 | 5512篇 |
2004年 | 5420篇 |
2003年 | 5244篇 |
2002年 | 5053篇 |
2001年 | 5428篇 |
2000年 | 5041篇 |
1999年 | 5536篇 |
1998年 | 15749篇 |
1997年 | 10425篇 |
1996年 | 8008篇 |
1995年 | 5850篇 |
1994年 | 5056篇 |
1993年 | 5066篇 |
1992年 | 3411篇 |
1991年 | 3276篇 |
1990年 | 3236篇 |
1989年 | 3061篇 |
1988年 | 2801篇 |
1987年 | 2248篇 |
1986年 | 2312篇 |
1985年 | 2614篇 |
1984年 | 2315篇 |
1983年 | 2070篇 |
1982年 | 1908篇 |
1981年 | 2048篇 |
1980年 | 1791篇 |
1979年 | 1662篇 |
1978年 | 1657篇 |
1977年 | 2026篇 |
1976年 | 2708篇 |
1975年 | 1424篇 |
1974年 | 1369篇 |
1973年 | 1317篇 |
1972年 | 1124篇 |
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
991.
Mats L. Cain J.T. Mickle M.H. 《Automation Science and Engineering, IEEE Transactions on》2009,6(1):4-8
In this paper, an indirect noninvasive method for measuring input impedance and the variations in the assembly of the interconnect and packaging between antenna and the integrated circuit (IC) effects of passive radio frequency identification (RFID) transponder (tags) antennas is presented. The analysis of different RFID tags is presented together with the experimental data. 相似文献
992.
993.
Laganà K Moretti M Dubini G Raimondi MT 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2008,222(5):705-715
Mechanical stimuli have been shown to enhance chondrogenesis on both animal and human chondrocytes cultured in vitro. Different mechanical stimuli act simultaneously in vivo in cartilage tissue and their effects have been extensively studied in vitro, although often in a separated manner. A new bioreactor is described where different mechanical stimuli, i.e. shear stress and hydrostatic pressure, can be combined in different ways to study the mechanobiology of tissue engineered cartilage. Shear stress is imposed on cells by forcing the culture medium through the scaffolds, whereas a high hydrostatic pressure up to 15 MPa is generated by pressurizing the culture medium. Fluid-dynamic experimental tests have been performed and successful validation of the bioreactor has been carried out by dynamic culture of tissue-engineered cartilage constructs. The bioreactor system allows the investigation of the combined effects of different mechanical stimuli on the development of engineered cartilage, as well as other possible three-dimensional tissue-engineered constructs. 相似文献
994.
Matthew O.T. Cole Author Vitae Theeraphong Wongratanaphisan Author Vitae 《Automatica》2008,44(11):2876-2883
Model-based feedback control of vibration in flexible structures can be complicated by the possibility that interaction with an external body occurs. If not accounted for, instability or poor performance may result. In this paper, a method is proposed for achieving robust vibration control of flexible structures under contact. The method uses robust linear state feedback, coupled with a state estimation scheme utilizing contact force measurement. Uncertain contact characteristics are modelled by a sector-bounded non-linear function, such that state feedback gains can be synthesized using a matrix inequality formulation of the Popov stability criterion. A separation theorem is used to establish a robust H2 cost bound for the closed loop system. Experimental results from a multi-mode flexible structure testbed confirm that vibration attenuation and stability can be maintained over a broad range of contact characteristics, in terms of compliance and clearance. 相似文献
995.
Mark T.Hoske 《软件》2008,(5):4
我非常钟爱办公用品商店的商业模式,就如同按下按钮那般简单。如果收益同按按钮一样简单,你能想象将会发生什么吗?现在就有这样一个例子:我们写(按钮),您接受(动),每个人都获取收益(这很简单)。标准其实就处于可盈利的按钮之间。我坚信ISA88第5部分标准的价值,如果可以得到广泛的应用,将意味着许多设施的盈 相似文献
996.
最近有些读者朋友问:现在微软为什么这么霸道,连显示器都要通过它的认证,没有通过Windows Vista认证的液晶显示器会有什么不同吗?液晶显示器和Windows Vista操作系统之间到底有什么必要的联系呢?通过Windows Vista认证的显示器又有什么好处呢?针对上述种种疑问,今天我们将为大家一一解答。 相似文献
997.
A. V. Inyushkin A. N. Taldenkov S. Yu. Shabanov L. N. Dem'yanets T. G. Uvarova 《Journal of Superconductivity and Novel Magnetism》1994,7(2):331-335
We present precise measurements of in-plane thermal conductivity for superconducting single crystals of YBa2Cu3O7?x (YBCO) withT c =92 and 60 K, Bi2Sr2CaCu2O8 (BSCCO), and of Zn-doped YBCO. Magnetization and thermal conductivity data obtained with the same 90-K YBCO crystal demonstrate a close relationship between the magnetic thermal resistivity and the internal magnetic fieldB in a superconductor in the mixed state. For all superconductors studied here, the magnetic thermal resistivity is a sublinear function of magnetic field. The origins of the nonlinearity are discussed. Angular dependences of the magnetic thermal resistivity have been shown to depart from the anisotropic 3D superconductor model and are in quantitative agreement with a quasi-2D model. Implications for spatial modulation of the order parameter are made. 相似文献
998.
In clinical trials in advanced urogenital cancer with metastasis there are cases showing a poor clinical response and poor prognosis. The cure of advanced urogenital cancer still remains a major problem in management. The present paper is a summary of 8 articles presented at the symposium on "Management of advanced urogenital cancer: Treatment of metastasis" in the 43th Annual Meeting of Center Section of Japanese Urological Association in November, 1993. The present status, problems and future conception of treatment modalities for advanced urogenital cancer were discussed. 相似文献
999.
T Sugishita 《Canadian Metallurgical Quarterly》1994,46(8):717-722
The points of this presentation are reform of the theory relating to "Dysplasia and Carcinogenesis" and the cytological methods. In 1976, Meisels and Fortin reported that dysplasia is the disease caused by Human papilloma virus (HPV), and surprisingly, intermediate cells infected by HPV possessed the ability of proliferation and mitosis, resulting in binucleation and multinucleation. In cytology, dysplasia is thought to be delivered from basal cells and abnormal cells are differentiated from lower layer to upper layer, the grade of dysplasia is judged from the level of cell-differentiation. In histology, however, differentiated cells are thought to be normal cells from the histological definition. Therefore, the histological theory cannot explain the fact that the appearance of the abnormal cells from the all layers in cytology of the mild dysplasia. This discrepancy can be understood well if we think it is caused by HPV infection. HPV (ds-DNA) can only proliferate using cellular factors. And as keratinocytes is important with relating to this proliferation, HPV affects human intermediate layer and upper layer. In HPV-infected cells, HPV-E6 protein and E7 protein can bind the products of p53 and pRB, suppressor genes, respectively. These lead to degradation of these proteins' function, acceleration of cell proliferation, and abnormality of cell-cycle time. Our fundamental theory of dyskaryosis is based on these findings. Mild dysplasia is transferred from intermediate layer to upper layer and vanish after cell maturation. Immortalization, transformation, and gene alteration are important factors for carcinogenesis. The deletion of chromosome 3p is one of the most important genetic changes during carcinogenesis. On the basis of carcinogenesis theory described above, the cytological findings of HPV-infected cells are classified into three steps.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
1000.
Process simulation and fabrication of advanced multi-step three-dimensional braided preforms 总被引:3,自引:0,他引:3
The fundamentals of multi-step braiding for the fabrication of three-dimensional fibre preforms for composites have been studied. To facilitate the understanding of the complex multi-step braiding processes, a computer simulation algorithm has been developed. The simulation acts as a tool to allow the identification of individual yarn paths, number and location of yarn groups, and braid geometry. It was found that individual control of the rows and columns of yarn carriers on a Cartesian braiding bed allows for the fabrication of advanced multi-step braids; the micro-structural possibilities of three-dimensional braids are thus greatly extended. Some basic relationships of the braiding parameters have been identified. It has been concluded that the traditional four-step and two-step braidings are special cases of multi-step braidings. To verify the feasibility of the structures, experimental investigations have also been carried out. Innovative braid architectures have been designed and fabricated using a prototype multi-step braiding machine. 相似文献