全文获取类型
收费全文 | 31788篇 |
免费 | 645篇 |
国内免费 | 90篇 |
专业分类
电工技术 | 523篇 |
综合类 | 260篇 |
化学工业 | 5350篇 |
金属工艺 | 840篇 |
机械仪表 | 711篇 |
建筑科学 | 973篇 |
矿业工程 | 149篇 |
能源动力 | 535篇 |
轻工业 | 4195篇 |
水利工程 | 235篇 |
石油天然气 | 144篇 |
武器工业 | 20篇 |
无线电 | 1671篇 |
一般工业技术 | 5635篇 |
冶金工业 | 7404篇 |
原子能技术 | 205篇 |
自动化技术 | 3673篇 |
出版年
2024年 | 382篇 |
2023年 | 425篇 |
2022年 | 322篇 |
2021年 | 732篇 |
2020年 | 638篇 |
2019年 | 522篇 |
2018年 | 932篇 |
2017年 | 849篇 |
2016年 | 952篇 |
2015年 | 817篇 |
2014年 | 973篇 |
2013年 | 1821篇 |
2012年 | 1363篇 |
2011年 | 1416篇 |
2010年 | 1189篇 |
2009年 | 1118篇 |
2008年 | 1269篇 |
2007年 | 1199篇 |
2006年 | 861篇 |
2005年 | 706篇 |
2004年 | 521篇 |
2003年 | 506篇 |
2002年 | 444篇 |
2001年 | 356篇 |
2000年 | 334篇 |
1999年 | 461篇 |
1998年 | 2292篇 |
1997年 | 1400篇 |
1996年 | 983篇 |
1995年 | 608篇 |
1994年 | 491篇 |
1993年 | 435篇 |
1992年 | 188篇 |
1991年 | 185篇 |
1990年 | 169篇 |
1989年 | 164篇 |
1988年 | 152篇 |
1987年 | 164篇 |
1986年 | 148篇 |
1985年 | 228篇 |
1984年 | 193篇 |
1983年 | 176篇 |
1982年 | 142篇 |
1981年 | 181篇 |
1980年 | 180篇 |
1979年 | 129篇 |
1978年 | 114篇 |
1977年 | 225篇 |
1976年 | 484篇 |
1973年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A procedure is presented to automatically assign a modified Pfafstetter code to a stream network and its associated watersheds. The first step is to build a topological network according to the object-oriented Arc Hydro framework definition in ArcGIS. These network relations are then mapped into a code that fully represents the stream hierarchy of a basin in a single attribute. Its use does not depend on ArcGIS object orientation and facilitates simple hierarchical aggregation and querying using only the attribute tables of shapefile versions of the stream network and watershed datasets. The code was implemented for the whole of Austria to support the flexible presentation and user-defined aggregation of water balance results in the digital version of the Hydrological Atlas of Austria. 相似文献
62.
For the efficient analysis and optimization of flexible multibody systems, gradient information is often required. Next to simple and easy-to-implement finite difference approaches, analytical methods, such as the adjoint variable method, have been developed and are now well established for the sensitivity analysis in multibody dynamics. They allow the computation of exact gradients and require normally less computational effort for large-scale problems. In the current work, we apply the adjoint variable method to flexible multibody systems with kinematic loops, which are modeled using the floating frame of reference formulation. Thereby, in order to solve ordinary differential equations only, the equations of motion are brought into minimal form using coordinate partitioning, and the constraint equations at position and velocity level are incorporated in the adjoint dynamics. For testing and illustrative purposes, the procedure is applied to compute the structural gradient for a flexible piston rod of a slider–crank mechanism. 相似文献
63.
A three-axial tactile force sensor for the investigation of micromechanical structures has been developed using silicon micromachining
technology. The sensor is capable of performing mechanical micro material characterisation such as the determination of the
spring constant of complex micromechanical structures. Another application for this sensor is dimensional metrology where
it has been tested as a 3D probe in a test set-up for coordinate measurements. 相似文献
64.
In this paper we present storage structures for efficiently processing XML path queries on healthcare data stored in smart cards using XML format. In the design of the storage structures that we present, properties of healthcare data and fundamental types of queries on the healthcare data are taken into account as well as the constraints of the smart cards. We compare the space and time efficiency of the proposed storage structures for various types of queries. 相似文献
65.
A precise calculation of the amount of intraalveolar fluid is the basis of a quantitative analysis of intraalveolar compounds. Different approaches have been made to cover this important problem. Here, we report a comparative study with five markers: 99mTc-DTPA, 51Cr-EDTA, inulin, urea, and methylene blue in animal experiments as well as in human experiments. The marker substances were added to the lavage fluid, and the "dilution" of the markers, i.e., the alveolar fluid, was calculated. The results showed that in animals with healthy lungs the tracer methods are able to calculate amounts of intraalveolar fluid that are comparable to morphologic findings. In animals as well as in humans, methylene blue and inulin were shown to be useless in determining alveolar fluid volume compared with the tracer methods. In humans, the calculations with the urea method and with Tc-DTPA were in the same magnitude, but there was no individual correlation. We conclude that, at present, the methods to quantitate alveolar fluid volume lack precision and add nothing to a deeper understanding of alveolar biology. 相似文献
66.
Diclofenac HEP plaster was tested in an open study in the treatment of different traumatic sport and overload injuries, to confirm the results of efficacy and tolerability already shown in other clinical studies. A total of 101 patients were assigned to treatment and were eligible for the evaluation of results at the end of a 14-day treatment period. The average score of spontaneous pain, assessed by means of a verbal scale and a visual analogical scale, showed a clear difference in pain rating between the beginning and end of treatment. In general 60% pain reduction was observed. The difference in analgesic activity was already apparent on the 7th day of treatment (-28%). The reduction of pain was confirmed by changes in another subjective sign related to the injury: provoked pain. This symptom decreased in a manner comparable to spontaneous pain: 61% pain reduction after 2 weeks of treatment. Global assessment of efficacy, performed by the investigator at the end of treatment, showed the clear therapeutic activity of local treatment with diclofenac HEP plaster. Satisfactory results were obtained and only 18% of the patients (most of them with chronic and persistent pain) experienced ineffective pain relief at the end of the 2-week treatment. The beneficial effects of diclofenac HEP plaster on pain are confirmed by the patients' assessment, since almost identical scores were obtained. It is striking that the overall tolerance of diclofenac HEP plaster, applied topically twice a day for 2 weeks, was "good" or "excellent" in the 101 patients treated. Any side effect was reported on the patient's card and all the patients completed the study. 相似文献
67.
Results from investigations on the metabolism of 14C-Fenazox show that in 6-8 weeks old tomato-plants (sort "Harzfeuer") the agent undergoes a biotransformation. After chromatographic separation the structure of the biotransformation products was elucidated by comparison to authentic test substances, by derivatization as well as by means of physico-chemical methods. With that, the following metabolites were identified: non-transformed Fenazox, o-hydroxyazobenzene, o-hydroxyaniline, and p-hydroxyaniline. Probably, the agent is first transformed enzymatically or non-enzymatically into o-hydroxyazobenzene, then follows a reductive cleavage into o-hydroxyaniline and aniline. In its turn, the latter is transformed into o-hydroxy- and p-hydroxyaniline. Experiments in the field of transformation kinetics indicated that the concentration of the applied Fenazox rapidly decreases and that the first transformation product o-hydroxyazobenzene in the beginning increases and then again decreases in its concentration. With increasing application time it comes to an increase of the non-extractable residues. 相似文献
68.
H. Buggisch H. Bucka F. Reutter H. G. Hahn F. Kolberg H. Unbehauen M. Biermann M. Ziegner H. Kilger H. Brüggemann H. Regenbogen 《Forschung im Ingenieurwesen》1978,44(6):197-200
Ohne Zusammenfassung 相似文献
69.
Antioxidative effects of Carum seeds 总被引:1,自引:0,他引:1
K. Aitztmüller 《Journal of the American Oil Chemists' Society》1997,74(2):185-185
70.
By means of animal experiments on rabbits the significance of dural tension in relation to skull growth is emphasised. Our findings support our "new points of view on the pathology and therapy of craniosynostosis", previously published in this journal. 相似文献