全文获取类型
收费全文 | 456164篇 |
免费 | 6087篇 |
国内免费 | 885篇 |
学科分类
工业技术 | 463136篇 |
出版年
2021年 | 4977篇 |
2020年 | 3962篇 |
2019年 | 4899篇 |
2018年 | 9051篇 |
2017年 | 9317篇 |
2016年 | 9830篇 |
2015年 | 5838篇 |
2014年 | 9292篇 |
2013年 | 21167篇 |
2012年 | 13868篇 |
2011年 | 16998篇 |
2010年 | 13797篇 |
2009年 | 15056篇 |
2008年 | 15206篇 |
2007年 | 14902篇 |
2006年 | 12076篇 |
2005年 | 10885篇 |
2004年 | 10515篇 |
2003年 | 10276篇 |
2002年 | 9693篇 |
2001年 | 9415篇 |
2000年 | 9279篇 |
1999年 | 8950篇 |
1998年 | 20464篇 |
1997年 | 15022篇 |
1996年 | 11425篇 |
1995年 | 8550篇 |
1994年 | 7805篇 |
1993年 | 7829篇 |
1992年 | 6146篇 |
1991年 | 6151篇 |
1990年 | 6001篇 |
1989年 | 5963篇 |
1988年 | 5758篇 |
1987年 | 5376篇 |
1986年 | 5105篇 |
1985年 | 5674篇 |
1984年 | 5415篇 |
1983年 | 5114篇 |
1982年 | 4748篇 |
1981年 | 4928篇 |
1980年 | 4815篇 |
1979年 | 4961篇 |
1978年 | 5138篇 |
1977年 | 5587篇 |
1976年 | 7101篇 |
1975年 | 4627篇 |
1974年 | 4599篇 |
1973年 | 4713篇 |
1972年 | 4029篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A. Mandrino R. Eloy B. Moyen J. L. Lerat D. Treheux 《Journal of materials science. Materials in medicine》1992,3(6):457-463
Base alumina ceramics with dispersoids (BAC) are a new class of ceramics with improved mechanical properties as compared to pure alumina. They are obtained by dispersion of powder within an alumina matrix. Of the three new ceramics studied here, A20Z possesses the best mechanical properties as well as tribological properties superior to those of pure alumina whether it is used in ceramic-ceramic or ceramic-polyethylene combination.Mechanical behaviour and tissue response afterin vivo implantation were studied. Small four-point flexion bars obtained by pressureless sintering were implanted subcutaneously in the rat. The mechanical properties were unmodified even after one year from implantation.The tissue response was studied up to one year on cylinders implanted in the paravertebral muscles of Wistar rats, and was evaluated by qualitative examination of the encapsulating membrane and measurement of its thickness in relation to pure alumina. The tissue responses were comparable for both alumina and the three tested ceramics. 相似文献
992.
A. Inoue B. G. Kim K. Nosaki T. Yamaguchi T. Masumoto 《Journal of Materials Science Letters》1992,11(12):865-867
On leave from: Honda Research and Development Co., Ltd, Wako 351-01, Japan. 相似文献
993.
The eigenstructures of common covariance matrices are identified for the general case of M closely spaced signals. It is shown that the largest signal-space eigenvalue is relatively insensitive to signal separation. By contrast, the i th largest eigenvalue is proportional to δω2(i-1) or δω4(i-1), where δω is a measure of signal separation. Therefore, matrix conditioning degrades rapidly as signal separation is reduced. It is also shown that the limiting eigenvectors have remarkably simple structures. The results are very general, and apply to planar far-field direction-finding problems involving almost arbitrary scenarios, and also to time-series analysis of sinusoids, exponentials, and other signals 相似文献
994.
Softening behaviour of 50 CrV4 steel on thermomechanical treatment Determination of static softening of austenite on thermomechanical treatment of steel by rolling. Analysed was the development of the austenite structure and influencing the work softening processes depending on the deformation-temperature-time mode. The static softening processes were modelled mathematically by using Avrami's relationships. 相似文献
995.
This paper presents the results of laboratory measurements of relative permeability for two phase flow in partially saturated samples of unconsolidated sands. Relative permeabilities for tap water and air, de-aired water and nitrogen were measured using a steady—state technique. Three different sand samples (fine sand, heterogeneous sand and coarse sand) were tested. 相似文献
996.
Translated from Izmeritel'naya Tekhnika, No. 7, pp. 8–9, July, 1992. 相似文献
997.
Results of ballistic tests for obstacles made of combined materials in relation to striker shape are presented in the form of penetration curves. It is established that striker shape affects not only quantitative indices, but also the qualitative nature of these curves.Translated from Problemy Prochnosti, No. 1, pp. 60–62, January, 1992. 相似文献
998.
A coupled-mode analysis of superimposed holographic transmission gratings in single-mode planar optical waveguides is presented. The diffraction characteristics are shown to be sensitive to the polarization of the incident wave, the angular separation of the output waves and the relative index modulation between the gratings. The coupling between gratings affects the diffraction efficiencies and decreases the angular and wavelength selectivities. Nevertheless, good channel separation and high fanout can be obtained together 相似文献
999.
1000.