全文获取类型
收费全文 | 297097篇 |
免费 | 5894篇 |
国内免费 | 2272篇 |
专业分类
电工技术 | 6964篇 |
技术理论 | 2篇 |
综合类 | 2560篇 |
化学工业 | 43552篇 |
金属工艺 | 12345篇 |
机械仪表 | 10723篇 |
建筑科学 | 9031篇 |
矿业工程 | 1993篇 |
能源动力 | 7253篇 |
轻工业 | 25080篇 |
水利工程 | 3072篇 |
石油天然气 | 6496篇 |
武器工业 | 269篇 |
无线电 | 39136篇 |
一般工业技术 | 54610篇 |
冶金工业 | 48529篇 |
原子能技术 | 5809篇 |
自动化技术 | 27839篇 |
出版年
2022年 | 2155篇 |
2021年 | 3421篇 |
2020年 | 2567篇 |
2019年 | 2901篇 |
2018年 | 4418篇 |
2017年 | 4667篇 |
2016年 | 4744篇 |
2015年 | 3657篇 |
2014年 | 5746篇 |
2013年 | 13453篇 |
2012年 | 8695篇 |
2011年 | 11287篇 |
2010年 | 9164篇 |
2009年 | 9860篇 |
2008年 | 10655篇 |
2007年 | 10568篇 |
2006年 | 9796篇 |
2005年 | 8876篇 |
2004年 | 8058篇 |
2003年 | 7738篇 |
2002年 | 7360篇 |
2001年 | 7316篇 |
2000年 | 7043篇 |
1999年 | 7332篇 |
1998年 | 15155篇 |
1997年 | 11073篇 |
1996年 | 8912篇 |
1995年 | 7031篇 |
1994年 | 6250篇 |
1993年 | 5953篇 |
1992年 | 4880篇 |
1991年 | 4457篇 |
1990年 | 4231篇 |
1989年 | 3935篇 |
1988年 | 3748篇 |
1987年 | 3269篇 |
1986年 | 3141篇 |
1985年 | 3666篇 |
1984年 | 3439篇 |
1983年 | 3061篇 |
1982年 | 2883篇 |
1981年 | 2972篇 |
1980年 | 2777篇 |
1979年 | 2659篇 |
1978年 | 2502篇 |
1977年 | 2951篇 |
1976年 | 3560篇 |
1975年 | 2318篇 |
1974年 | 2316篇 |
1973年 | 2321篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Kahny D. Schmitt K. Wiesbeck W. 《Geoscience and Remote Sensing, IEEE Transactions on》1992,30(5):847-852
A calibration technique for laboratory type polarimetric, bistatic instrumentation radars is presented. It describes the errors induced by the standard radiation transfer approach (I-SRT) in a way similar to that for the monostatic case. A 12-term error correction and absolute polarimetric calibration is performed with two external reference targets. Only the polarimetric bistatic reference of the first target must be theoretically determined. The scattering reference of the second target is determined by a measurement during the calibration process (single reference calibration). The simulation of a third cross-polarization measurement is performed by an antenna rotation and a remeasurement of the second target. Thus all data are gained for the determination of the error terms and measurements of unknown objects can be full polarimetrically calibrated. The procedures are shown for an adapted dihedral corner reflector. Misalignment errors are discussed 相似文献
993.
We explain why the methods in Langridge, Hart and Crampin [Comput. Phys. Commun. 134 (2001) 78] suffice for the evaluation of the lattice sums entering the Madelung matrix describing multipole interactions in systems with one-dimensional translational periodicity. 相似文献
994.
Computational and laboratory experiments generate masses of data that must be stored reliably, with minimal effort on each researcher's part, and must be retrievable for decades. The storage environment must also work seamlessly across scientific disciplines and capture all of a file system's features in a semantically-based catalog that provides Boolean, keyword, and tree-based data access. The authors describe a metadata-based archive for scientific data that provides flexible archive storage for very large data sets. The system uses metadata to organize and manage the data without imposing predefined metadata formats on scientists. 相似文献
995.
996.
Dianov E.M. Grudinin A.B. Gurjanov A.N. Gusovsky D.D. Harutjunian Z.E. Ignatev S.V. Smirnov O.B. 《Lightwave Technology, Journal of》1992,10(2):118-124
The reproducible technology for producing high-birefringence fibers with stress-induced elliptical cladding and circular core is described. The authors have obtained fibers that have a birefringence of about (1-3) 10-4, a mode coupling parameter of about (2-7) 10 -5 m-1, and loss of less than 0.5 dB/km at 1.6 μm. The authors have found effects restricting the capability of test fibers to maintain the state of linear polarization 相似文献
997.
Bykov Yu. A. Karpukhin S. D. Panfilov Yu. V. Boichenko M. K. Cheptsov V. O. Osipov A. V. 《Metal Science and Heat Treatment》2003,45(9-10):396-399
A method for evaluating the hardness of coatings with nanosize thickness is suggested. The method includes the determination of the hardness of the “coating-substrate” composition by indenting the coating and subsequent computation of the hardness with the use of the additivity rule. This requires determination of the thickness of the coating, of the hardness of the substrate, and of the indentation depth. 相似文献
998.
J Cremer G Steinhoff M Karck T Ahnsell M Brandt OE Teebken D Hollander A Haverich 《Canadian Metallurgical Quarterly》1997,12(5):753-758
OBJECTIVE: Encouraging results on myocardial preconditioning in experimental models of infarction, stunning or prolonged ischemia raise the question whether preconditioning techniques may enhance conventional cardioplegic protection used for routine coronary surgery. METHODS: A prospective clinical trial was conducted to investigate the effect of additional ischemic normothermic preconditioning prior to cardioplegic arrest applying cold blood cardioplegia in patients scheduled for routine coronary surgery (3 vessel disease, left ventricular ejection fraction > 50%). Two cross clamp periods of 5 min with the hearts beating in sinus rhythm were applied followed by 10 min of reperfusion, each (n = 7, group I). Inducing moderate hypothermia cold blood cardioplegia was delivered antegradely. In control groups, cold intermittent blood cardioplegia (n = 7, group II) was used alone. Coronary sinus effluents were analyzed for release of creatine kinase (CK), CK-MB, lactate, and troponin T at 1, 3, 6, 9, and 12 h. In addition, postoperative catecholamine requirements were monitored. RESULTS: The procedure was tolerated well, and no perioperative myocardial infarction in any of the groups studied occurred. Concentrations of lactate tended to be higher in group I, but this difference was not significant. In addition, no significant differences for concentrations of CK, CK-MB, and troponin T were found. Following ischemic preconditioning an increased dosage of dopamine was required within the first 12 h postoperatively (group I: 2.63 +/- 1.44 microg/kg/min, group II: 0.89 +/- 1.06 microg/kg/min). CONCLUSIONS: Combining ischemic preconditioning and cardioplegic protection with cold blood cardioplegia does not appear to ameliorate myocardial protection when compared to cardioplegic protection applying cold blood cardioplegia alone. Inversely, contractile function seemed to be impaired when applying this protocol of ischemic preconditioning. 相似文献
999.
A tennis novice watching a match for the first time might be surprised that the crowd erupts with cheers when a player wins one point, then barely applauds when he wins the next. The crowd is not necessarily fickle; some points are genuinely more important than others because a tennis match is hierarchically structured. One match consists of several sets. One set consists of several games. One game consists of several points. The match-winning point is the most important one. How can we make that importance visible? Our goal is to let a fan, a player, or a coach examine tennis data visually, extract the interesting parts, and jump from one item to another quickly and easily. The visualization tool should help parse the elements of a match. We developed an interactive system called TennisViewer to visualize the dynamic, tree-structured data representing a tennis match. It provides an interface for users to quickly explore tennis match information. The visualization tool reveals the overall structure of the match as well as the fine details in a single screen. It uses a 2D display of translucent layers, a design that contains elements of Tree-Maps and of the Visual Scheduler system, which was designed to help faculty and students identify mutually available (transparent) time slots when arranging group meetings. TennisViewer provides MagicLens filters to explore specialized views of the information and a time-varying display to animate all or part of a match 相似文献
1000.
L. P. Podenok L. I. Sharakhovskii V. D. Shimanovich O. I. Yas’ko 《Journal of Engineering Physics and Thermophysics》1997,70(1):95-99
The influence of heat transfer processes in arc discharges on the development of thermal instability is considered. A substantial
dependence of the process of destabilization on the plasma properties is shown by the example of argon and helium arcs.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 93–98, January–February, 1997. 相似文献