全文获取类型
收费全文 | 178479篇 |
免费 | 2199篇 |
国内免费 | 711篇 |
专业分类
电工技术 | 3310篇 |
综合类 | 107篇 |
化学工业 | 28156篇 |
金属工艺 | 7800篇 |
机械仪表 | 5139篇 |
建筑科学 | 4508篇 |
矿业工程 | 876篇 |
能源动力 | 4757篇 |
轻工业 | 16597篇 |
水利工程 | 1713篇 |
石油天然气 | 3130篇 |
武器工业 | 2篇 |
无线电 | 19917篇 |
一般工业技术 | 33521篇 |
冶金工业 | 33442篇 |
原子能技术 | 4306篇 |
自动化技术 | 14108篇 |
出版年
2021年 | 1338篇 |
2019年 | 1275篇 |
2018年 | 2134篇 |
2017年 | 2114篇 |
2016年 | 2224篇 |
2015年 | 1599篇 |
2014年 | 2763篇 |
2013年 | 7874篇 |
2012年 | 4624篇 |
2011年 | 6454篇 |
2010年 | 5099篇 |
2009年 | 5951篇 |
2008年 | 5950篇 |
2007年 | 5937篇 |
2006年 | 5084篇 |
2005年 | 4738篇 |
2004年 | 4525篇 |
2003年 | 4192篇 |
2002年 | 4138篇 |
2001年 | 4153篇 |
2000年 | 3944篇 |
1999年 | 4078篇 |
1998年 | 10431篇 |
1997年 | 7423篇 |
1996年 | 5682篇 |
1995年 | 4299篇 |
1994年 | 3648篇 |
1993年 | 3589篇 |
1992年 | 2627篇 |
1991年 | 2548篇 |
1990年 | 2427篇 |
1989年 | 2440篇 |
1988年 | 2386篇 |
1987年 | 2145篇 |
1986年 | 2083篇 |
1985年 | 2391篇 |
1984年 | 2200篇 |
1983年 | 2033篇 |
1982年 | 1891篇 |
1981年 | 1960篇 |
1980年 | 1811篇 |
1979年 | 1823篇 |
1978年 | 1783篇 |
1977年 | 2117篇 |
1976年 | 2692篇 |
1975年 | 1566篇 |
1974年 | 1555篇 |
1973年 | 1612篇 |
1972年 | 1355篇 |
1971年 | 1266篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
V. V. Gribova A. S. Kleshchev F. M. Moskalenko V. A. Timchenko 《Automatic Documentation and Mathematical Linguistics》2015,49(6):221-231
A model for generation of directed graphs of information by the directed graph of metainformation for a two-level connected directed graph model of information units is described. It can be used as a basis in computer tools for editing information with a complex structure with different levels of abstraction and invariance to technological spaces (subject domains) in a common conceptual framework for carriers of this information, making it unnecessary to organize specialized training for these carriers or to involve professional intermediaries. 相似文献
942.
Computational Visual Media - Pool and billiards are amongst a family of games played on a table with six pockets along the rails. This paper presents an augmented reality tool designed to assist... 相似文献
943.
944.
De Angeli M Castaldo C Ratynskaia S Grosso G Almaviva S Caneve L Colao F Maddaluno G 《The Review of scientific instruments》2011,82(10):106101
The scheme and construction of an electro-optical probe able to collect charge and detect optical emission from expanding dense partially ionized vapour clouds are reported. The instrument can be applied to phenomena such as dust impact ionization and solid target laser ablation. First, results of measurements of expanding plasma cloud formed upon ablating W target are presented. Use of the instrument in different experimental facilities, including tokamak, is discussed. 相似文献
945.
Nuclear magnetic resonance is widely employed in studies of chemical reactions and molecular motions at moderate pressure and temperature, but for CO(2) solutions under supercritical conditions encountered in geological or mineral sequestration (pressures to 150 atm and temperatures to 150 °C) a specialized variable-temperature probe is required. The critical component of such a probe is its pressure chamber, and our working design is presented along with examples of its use in (13)C NMR measurements of bicarbonate and dissolved CO(2) fractions as functions of time, following initial pressurization to 70 atm. Also shown are final, steady-state values of these fractions as functions of temperature from 50 to 125 °C at 70 atm. 相似文献
946.
Arregui-Dalmases C Del Pozo E Stacey S Kindig M Lessley D Lopez-Valdes F Forman J Kent R 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2011,225(7):688-695
While rupture of the aorta is a leading cause of sudden death following motor vehicle crashes, the specific mechanism that causes this injury is not currently well understood. Aortic ruptures occurring in the field are likely due to a complex combination of contributing factors such as acceleration, compression of the chest, and increased pressure within the aorta. The objective of the current study was to investigate one of these factors in more detail than has been done previously; specifically, to investigate the in situ intra-aortic pressure generated during isolated belt loading to the abdomen. Ten juvenile swine were subjected to dynamic belt loads applied to the abdomen. Intraaortic pressure was measured at multiple locations to assess the magnitude and propagation of the resulting blood pressure wave. The greatest average peak pressure (113.6 +/- 43.5 kPa) was measured in the abdominal aorta. Pressures measured in the thoracic aorta and aortic arch were 70 per cent and 50 per cent, respectively, that measured in the abdominal aorta. No macroscopic aortic trauma was observed. To the authors' knowledge the present study is the first one to document the presence, propagation, and attenuation of a transient pressure wave in the aorta generated by abdominal belt loading. The superiorly moving wave is sufficient to generate hydrostatic and intimal shear stress in the aorta, possibly contributing to the hypothesized mechanisms of traumatic aortic rupture. 相似文献
947.
This study aimed at enhancing knowledge on the fate of diclofenac (DF), together with its main human metabolite 4'-hydroxydiclofenac (4'OHDF), during wastewater treatment by using a laboratory-scale membrane bioreactor (MBR). The reactor was fed continuously with non-radiolabelled diclofenac for a one month period prior to a single pulse of a 14C-radiolabelled solution of DF and 4'OHDF. The solution spike contained approximately 25% 4'OHDF and 65% DF, which corresponds to the ratio observed in municipal sewage, as well as traces of two other metabolites. The radioactivity was monitored for a total of twelve days in the various output streams. The calculation of the complete mass balance in the system demonstrated that the major part of the radioactivity left the reactor with the permeate (88.7%), while 2.1% was recovered in the excess sludge. Negligible amounts were recovered in the off-gas traps and on the membranes. Chromatographic analyses of effluent samples, by means of HPLC-MS coupled in parallel to a radiodetector, displayed a different pattern than the one of the spiked solution. It showed the occurrence of three additional metabolites. 相似文献
948.
James M. Chappell Azhar Iqbal M. A. Lohe Lorenz von Smekal Derek Abbott 《Quantum Information Processing》2013,12(4):1719-1735
The Grover search algorithm is one of the two key algorithms in the field of quantum computing, and hence it is desirable to represent it in the simplest and most intuitive formalism possible. We show firstly, that Clifford’s geometric algebra, provides a significantly simpler representation than the conventional bra-ket notation, and secondly, that the basis defined by the states of maximum and minimum weight in the Grover search space, allows a simple visualization of the Grover search analogous to the precession of a spin- ${\frac{1}{2}}$ particle. Using this formalism we efficiently solve the exact search problem, as well as easily representing more general search situations. We do not claim the development of an improved algorithm, but show in a tutorial paper that geometric algebra provides extremely compact and elegant expressions with improved clarity for the Grover search algorithm. Being a key algorithm in quantum computing and one of the most studied, it forms an ideal basis for a tutorial on how to elucidate quantum operations in terms of geometric algebra—this is then of interest in extending the applicability of geometric algebra to more complicated problems in fields of quantum computing, quantum decision theory, and quantum information. 相似文献
949.
ProDA employs wavelets to support exact, approximate, and progressive OLAP queries on large multidimensional datasets, while keeping update costs relatively low. ProDA not only supports online execution of ad hoc analytical queries on massive datasets, but also extends the set of supported analytical queries to include the entire family of polynomial aggregate queries as well as the new class of plot queries. 相似文献
950.
The MAC method 总被引:1,自引:0,他引:1
In this article recent advances in the Marker and Cell (MAC) method will be reviewed. The MAC technique dates back to the early 1960s at the Los Alamos Laboratories and this article starts with a historical review, and then a brief discussion of related techniques. Improvements since the early days of MAC (and the Simplified MAC - SMAC) include automatic time-stepping, the use of the conjugate gradient method to solve the Poisson equation for the corrected velocity potential, greater efficiency through stripping out the virtual particles (markers) other than those near the free surface, and more accurate approximations of the free surface boundary conditions, the addition of bounded high accuracy upwinding for the convected terms (thereby being able to solve higher Reynolds number flows), and a (dynamics) flow visualization facility. More recently, effective techniques for surface and interfacial flows and, in particular, for accurately tracking the associated surface(s)/interface(s) including moving contact angles have been developed. This article will concentrate principally on a three-dimensional version of the SMAC method. It will eschew both code verification and model validation; instead it will emphasize the applications that the MAC method can solve, from multiphase flows to rheology. 相似文献