全文获取类型
收费全文 | 267057篇 |
免费 | 3876篇 |
国内免费 | 270篇 |
专业分类
电工技术 | 5417篇 |
综合类 | 955篇 |
化学工业 | 49146篇 |
金属工艺 | 15381篇 |
机械仪表 | 10460篇 |
建筑科学 | 4871篇 |
矿业工程 | 3938篇 |
能源动力 | 3977篇 |
轻工业 | 11408篇 |
水利工程 | 4212篇 |
石油天然气 | 13063篇 |
武器工业 | 29篇 |
无线电 | 20525篇 |
一般工业技术 | 65930篇 |
冶金工业 | 32266篇 |
原子能技术 | 11161篇 |
自动化技术 | 18464篇 |
出版年
2021年 | 3446篇 |
2019年 | 3326篇 |
2018年 | 5994篇 |
2017年 | 6097篇 |
2016年 | 6663篇 |
2015年 | 3857篇 |
2014年 | 6146篇 |
2013年 | 11545篇 |
2012年 | 7859篇 |
2011年 | 9349篇 |
2010年 | 8110篇 |
2009年 | 9049篇 |
2008年 | 8588篇 |
2007年 | 8228篇 |
2006年 | 6634篇 |
2005年 | 5852篇 |
2004年 | 5801篇 |
2003年 | 5579篇 |
2002年 | 5381篇 |
2001年 | 5103篇 |
2000年 | 5008篇 |
1999年 | 4360篇 |
1998年 | 7376篇 |
1997年 | 5973篇 |
1996年 | 4626篇 |
1995年 | 3851篇 |
1994年 | 3596篇 |
1993年 | 3867篇 |
1992年 | 3385篇 |
1991年 | 3499篇 |
1990年 | 3648篇 |
1989年 | 3561篇 |
1988年 | 3413篇 |
1987年 | 3446篇 |
1986年 | 3358篇 |
1985年 | 3485篇 |
1984年 | 3430篇 |
1983年 | 3332篇 |
1982年 | 3165篇 |
1981年 | 3265篇 |
1980年 | 3243篇 |
1979年 | 3429篇 |
1978年 | 3608篇 |
1977年 | 3619篇 |
1976年 | 4070篇 |
1975年 | 3426篇 |
1974年 | 3492篇 |
1973年 | 3715篇 |
1972年 | 3208篇 |
1971年 | 2909篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
U Kachintorn O Chinapak V Vongphanich C Kositchaiwat S Lekhayananda U Khow-ean C Suttinont V Saowaros N Kludchareon M Leethochawalit 《Canadian Metallurgical Quarterly》1995,78(12):641-647
BACKGROUND: Roxatidine acetate is a novel H2-receptor antagonist and several studies have shown that it is effective in healing duodenal ulcers. We evaluated the efficacy of roxatidine in a non-western society with particular different features and its healing of duodenal ulcers was compared in Thailand with that of ranitidine. METHOD: The design was controlled, randomized, double-blind, and multicenter. The study recruited a total of 215 patients who were endoscoped at the start of the trial and then randomized to receive a single capsule of roxatidine acetate, 150 mg, or an identical capsule containing ranitidine, 300 mg, both to be taken at night. Patients were evaluated at 1, 2, and 4 weeks, including endoscopy at the last session, as well as at 6 weeks with repeat endoscopy if the ulcer had not healed. RESULT: Both drugs relieved pain rapidly, usually within a week, and at repeat endoscopy at 4 weeks most ulcers (78%) were healed, 77.0 and 79.5 per cent in ranitidine and roxatidine, and in those patients in whom healing was not completed the healing rate had risen appreciably to 89.8 and 93.8 per cent respectively at 6 weeks. Small ulcers tended to heal quicker than larger ones, but smoking and alcohol intake had no negative effects on the results. CONCLUSION: The study was valid proof that roxatidine, in a single evening dose of 150 mg, was found to be both safe and effective in the rapid healing of duodenal ulcers when compared with 300 mg ranitidine. 相似文献
994.
E V?is?nen 《Canadian Metallurgical Quarterly》1995,111(22):2186-2187
995.
Arata L.K. Dhawan A.P. Broderick J.P. Gaskil-Shipley M.F. Levy A.V. Volkow N.D. 《IEEE transactions on bio-medical engineering》1995,42(11):1069-1078
Model-based segmentation and analysis of brain images depends on anatomical knowledge which may be derived from conventional atlases. Classical anatomical atlases are based on the rigid spatial distribution provided by a single cadaver. Their use to segment internal anatomical brain structures in a high-resolution MR brain image does not provide any knowledge about the subject variability, and therefore they are not very efficient in analysis. The authors present a method to develop three-dimensional computerized composite models of brain structures to build a computerized anatomical atlas. The composite models are developed using the real MR brain images of human subjects which are registered through the principal axes transformation. The composite models provide probabilistic spatial distributions, which represent the variability of brain structures and can be easily updated for additional subjects. The authors demonstrate the use of such a composite model of ventricular structure to help segmentation of the ventricles and cerebrospinal fluid of MR brain images. Here, a composite model of ventricles using a set of 22 human subjects is developed and used in a model-based segmentation of ventricles, sulci, and white matter lesions. To illustrate the clinical usefulness, automatic volumetric measurements on ventricular size and cortical atrophy for an additional eight alcoholics and 10 normal subjects were made. The volumetric quantitative results indicated regional brain atrophy in chronic alcoholics 相似文献
996.
997.
998.
Ferdinand P. Ferragu O. Lechien J.L. Lescop B. Magne S. Marty V. Rougeault S. Kotrotsios G. Neuman V. Depeursinge Y. Michel J.B. Van Uffelen M. Varelas D. Berthou H. Pierre G. Renouf C. Jarret B. Verbandt Y. Stevens W. Voet M.R.H. Toscano D. 《Lightwave Technology, Journal of》1995,13(7):1303-1313
Recent developments of stability control in mines, essentially based on Ge-doped fiber Bragg gratings (FBG) are reported including results about the different aspects of the system: accurate characterizations of FBG, sensor network topology and multiplexing method, user interface design and sensor packaging 相似文献
999.
We investigate, analytically and numerically, stationary pulse propagation in n-core nonlinear fiber arrays of circular symmetry. It is shown that many types of stationary pulse-like solitary waves exist in these arrays. Transitions between the states of different symmetries occur in the form of bifurcations. The exact formula which specifies the points where asymmetric solutions bifurcate from the solution, which has identical pulses in each core, is obtained for the general n-core case. Energy-spatial frequency bifurcation diagrams are constructed for the lowest order soliton solutions for the n=3, 4, and 5 cases. The envelopes of these solutions and distributions of their field amplitude maxima among the cores are also presented 相似文献
1000.