全文获取类型
收费全文 | 22473篇 |
免费 | 1208篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 121篇 |
综合类 | 14篇 |
化学工业 | 5274篇 |
金属工艺 | 362篇 |
机械仪表 | 410篇 |
建筑科学 | 622篇 |
矿业工程 | 50篇 |
能源动力 | 474篇 |
轻工业 | 4131篇 |
水利工程 | 235篇 |
石油天然气 | 85篇 |
武器工业 | 2篇 |
无线电 | 927篇 |
一般工业技术 | 3517篇 |
冶金工业 | 4580篇 |
原子能技术 | 87篇 |
自动化技术 | 2806篇 |
出版年
2024年 | 54篇 |
2023年 | 227篇 |
2022年 | 606篇 |
2021年 | 814篇 |
2020年 | 536篇 |
2019年 | 573篇 |
2018年 | 934篇 |
2017年 | 901篇 |
2016年 | 903篇 |
2015年 | 703篇 |
2014年 | 920篇 |
2013年 | 1682篇 |
2012年 | 1388篇 |
2011年 | 1235篇 |
2010年 | 1014篇 |
2009年 | 941篇 |
2008年 | 961篇 |
2007年 | 889篇 |
2006年 | 590篇 |
2005年 | 468篇 |
2004年 | 460篇 |
2003年 | 400篇 |
2002年 | 369篇 |
2001年 | 249篇 |
2000年 | 223篇 |
1999年 | 303篇 |
1998年 | 1506篇 |
1997年 | 976篇 |
1996年 | 616篇 |
1995年 | 325篇 |
1994年 | 257篇 |
1993年 | 298篇 |
1992年 | 93篇 |
1991年 | 88篇 |
1990年 | 77篇 |
1989年 | 82篇 |
1988年 | 80篇 |
1987年 | 67篇 |
1986年 | 68篇 |
1985年 | 84篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1982年 | 58篇 |
1981年 | 69篇 |
1980年 | 56篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 99篇 |
1976年 | 192篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Summary The transition of a poly(vinyl chloride) after either nucleophilic substitution to various extents or plasticization with distinct amounts of diocytl phthalate has been measured by Dynamical Mechanical Thermal Analysis. Both sets of experiments are shown to result in similar loss of transition. The results are argued in the light of prior work on the substitution mechanism determining role of the mmr chain segments at the end of isotactic sequences. They strongly suggest the mmr structures to interact specifically with plasticizer thereby becoming stiffer (antiplasticization). 相似文献
42.
OBJECTIVE: a) To find the reasons for inadequate use of Hospital Casualty Departments (HCDs); b) to discover the general population's levels of information concerning non-hospital Emergency Services (NESs); c) to analyse the relationship between the type of Primary Care Centre (PCC), i.e. whether reformed or not, and inadequate use of HCDs. DESIGN: A crossover study. SETTING: The Germans Trias i Pujol Hospital Casualty Department, Badalona. PATIENTS: A random sample of 321 patients over 14 years old, who were attended for pathologies considered emergencies not requiring hospital treatment. MEASUREMENTS AND MAIN RESULTS: The variables gathered were: age, gender, where the patient came from, reason for hospital use, knowledge of NESs and subsequent referral. 83.2% of patients attended on their own initiative. The main reasons given were "advantages of a hospital" and "the persistence of symptoms." 49% of the patients stated they knew of the NESs. 80% of the patients proceeded from PCCs which had not been reformed. There were no statistically significant differences (p > 0.05) when the variables "reason for use" and "knowledge of NESs" were compared in relation to where the patient came from (i.e. reformed or non-reformed PCC). CONCLUSIONS: General practitioners in reformed PCCs are less likely to refer to HCDs. Knowledge and use of NESs should be actively supported. 相似文献
43.
A novel complex formed by ruthenium (III) and the sequestering ligand 1,2-propylenediaminetetraacetic acid (PDTA) has been synthetized and characterized. The structure of the monomeric compound, studied by X-ray diffraction , shows an almost symmetric octahedral geometry around the metal ion, with two chlorine atoms in a cis conformation. The antitumour activity against a variety of murine and human cancers is reported. 相似文献
44.
Introduction and General Overview of Cyclodextrin Chemistry 总被引:6,自引:0,他引:6
Szejtli J 《Chemical reviews》1998,98(5):1743-1754
45.
S. Rodríguez C. Lafuente J. A. Carrión F. M. Royo J. S. Urieta 《International Journal of Thermophysics》1996,17(6):1281-1288
Excess Volumes,V
E, and excess viscosities,
E, at 293.15 and 313.15 K are reported for binary mixtures of some cyclic ethers (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran) + bromocyclohexane. These properties were obtained from density and viscosity measurements.
E and
E show negatives values for all the mixtures. 相似文献
46.
E Maganto Pavón 《Canadian Metallurgical Quarterly》1996,20(6):522-533
In spite of the names and works of practically all the early 19th Century Spanish specialists in urinary tract being widely known, there are still in my opinion several names and writings, either forgotten or misplaced in newspaper libraries, archives and general libraries, awaiting to be discovered. The second half of the 19th Century was a prolific age in every aspect of Spanish life, most particularly literature. In Medicine, apart from the well known professional writings, the number of scientific journals and publications, whether in the form of brochures or divulgative articles, that came to light was countless. Computer management of collections currently under implementation in many registers, will allow their location and the finding of new texts. One of these long forgotten pioneers, is Doctor Alejandro Settier (1858-1915), a Valencian practitioner who describes himself as a "disciple of the Paris hospitals and specialist in genitourinary tract disorders", who practised in Madrid between 1883 and 1890. Surprisingly, and in spite of him being the most prolific author in urological issues during the last century (my investigations show he is the author of 2 books, 3 brochures and 40 articles in journals), neither his name nor his work, as far as we know, are mentioned by none of the historians consulted, which is nothing but highly surprising if we also take into consideration that Alejandro Settier was the founder of the first Spanish monographic journal for urinary disorders: "Gaceta de enfermedades de los órganos génito-urinarios" (Gazette of genitourinary organs disorders), Madrid 1887, which in spite of its short existence, can be considered as the first scientific periodical publication in our specialty. 相似文献
47.
Levente Sajó Zsófia Ruttkay Attila Fazekas 《International journal of human-computer studies》2011,69(7-8):483-495
In this paper we present Turk-2, a hybrid multi-modal chess player with a robot arm and a screen-based talking head. Turk-2 can not only play chess, but can see and hear the opponent, can talk to him and display emotions. We were interested to find out if a simple embodiment with human-like communication capabilities enhances the experience of playing chess against a computer. First, give an overview of the development road to multi-modal communication with computers. Then we motivate our research with a hybrid system, we introduce the architecture of Turk-2, we describe the human experiments and its evaluation. The results justify that multi-modal interaction makes game playing more engaging, enjoyable – and even more effective. These findings for a specific game situation provide yet another evidence of the power of human-like interaction in turning computer systems more attractive and easier to use. 相似文献
48.
49.
Carlos López-Vázquez 《International journal of remote sensing》2016,37(19):4683-4697
The choice of the best interpolation algorithm of data gathered at a finite number of locations has been a persistently relevant topic. Typical papers take a single data set, a single set of data points, and a handful of algorithms. The process considers a subset I of the data points as known, builds the interpolant with each algorithm, applies it to the points of another subset C, and evaluates the MAE (mean absolute error), the RMSE (root mean square error), or any other metric over such points. The less these statistics are, the better the algorithm is, so a deterministic ranking between methods (without confidence level) can be derived based upon it. Ties between methods are usually not considered. In this article a complete protocol is proposed in order to build, with a modest additional effort, a ranking with a confidence level. To illustrate this point, the results of two tests are shown. In the first one, a simple Monte Carlo experiment was devised using irregularly distributed points taken from a reference DEM (digital elevation model) in raster format. Different metrics led to different rankings, suggesting that the choice of the metric to define the ‘best interpolation algorithm’ would need a trade-off. The second experiment used mean daily radiation data from an international interpolation comparison exercise and RMSE as the metric of success. Only five simple interpolation methods were employed. The ranking using this protocol anticipated correctly the first and second place, afterwards confirmed employing independent control data. 相似文献
50.
Juan Francisco Gómez-Lopera José Martínez-Aroza Aureliano M. Robles-Pérez Ramón Román-Roldán 《Journal of Mathematical Imaging and Vision》2000,13(1):35-56
This work constitutes a theoretical study of the edge-detection method by means of the Jensen-Shannon divergence, as proposed by the authors. The overall aim is to establish formally the suitability of the procedure of edge detection in digital images, as a step prior to segmentation. In specific, an analysis is made not only of the properties of the divergence used, but also of the method's sensitivity to the spatial variation, as well as the detection-error risk associated with the operating conditions due to the randomness of the spatial configuration of the pixels. Although the paper deals with the procedure based on the Jensen-Shannon divergence, some problems are also related to other methods based on local detection with a sliding window, and part of the study is focused to noisy and textured images. 相似文献