全文获取类型
收费全文 | 3228篇 |
免费 | 158篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 59篇 |
综合类 | 6篇 |
化学工业 | 798篇 |
金属工艺 | 81篇 |
机械仪表 | 75篇 |
建筑科学 | 181篇 |
矿业工程 | 4篇 |
能源动力 | 124篇 |
轻工业 | 247篇 |
水利工程 | 9篇 |
石油天然气 | 2篇 |
无线电 | 298篇 |
一般工业技术 | 640篇 |
冶金工业 | 393篇 |
原子能技术 | 20篇 |
自动化技术 | 453篇 |
出版年
2022年 | 34篇 |
2021年 | 54篇 |
2020年 | 34篇 |
2019年 | 50篇 |
2018年 | 54篇 |
2017年 | 75篇 |
2016年 | 77篇 |
2015年 | 80篇 |
2014年 | 105篇 |
2013年 | 157篇 |
2012年 | 132篇 |
2011年 | 206篇 |
2010年 | 121篇 |
2009年 | 145篇 |
2008年 | 155篇 |
2007年 | 152篇 |
2006年 | 140篇 |
2005年 | 118篇 |
2004年 | 103篇 |
2003年 | 101篇 |
2002年 | 76篇 |
2001年 | 72篇 |
2000年 | 68篇 |
1999年 | 59篇 |
1998年 | 141篇 |
1997年 | 92篇 |
1996年 | 100篇 |
1995年 | 52篇 |
1994年 | 53篇 |
1993年 | 43篇 |
1992年 | 40篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 16篇 |
1986年 | 27篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 23篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 21篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1970年 | 13篇 |
排序方式: 共有3390条查询结果,搜索用时 31 毫秒
21.
22.
Quinine induces changes in the motion of the cupula in the lateral line canal of the African knife-fish in response to sinusoidal water movements. Two different phases in the action of quinine on the cupular frequency response can be discerned. In the first phase the best frequency, i.e., the frequency at which the cupular vibratory displacement is maximal in response to constant-amplitude sinusoidal canal fluid displacement, shifts toward higher frequencies. During this phase, lasting about 70-100 min, the best frequency increases by a factor between 1.3 and 1.5. In the second phase, during roughly the following 90 min, the best frequency decreases gradually to a value 0.3-0.5 times that observed before the application of quinine. 相似文献
23.
24.
Fifty-five patients (46 women and 9 men) with craniomandibular disorders and a history of pain of at least 6 months' duration participated in this trial. The patients were randomly assigned to three groups: one group to receive acupuncture; one group to receive occlusal splint therapy; and one group to act as controls. Pressure pain threshold, clinical dysfunction score, and visual analog scale measures were used to evaluate patients before, immediately after, and 6 months after treatment. A moderate, but statistically significant, correlation was found between pressure pain threshold and the number of tender spots in the masticatory muscles (tau = -.43; P < .001), degree of tenderness in the masticatory muscles (tau = -.43; P < .001), clinical dysfunction score (tau = .32; P < .001), and the visual analog scale (tau = -.25; P < .01). The short-term results showed a statistically significant improvement in all evaluations for both treatment groups. No significant differences were found in the control group. The improvements resulted in significant differences between the control and each treatment group immediately after treatment. At the 6-month follow-up, no significant differences in pressure pain threshold or clinical dysfunction score were found in the two treatment groups compared with the short-term results. 相似文献
25.
Joachim von zur Gathen 《Computational Complexity》1991,1(4):360-394
Optimal sequential and parallel algorithms for exponentiation in a finite field containing F
q
are presented, assuming thatqth powers can be computed for free. 相似文献
26.
Cornelius Temmel Nils-Gunnar Ingesten Birger Karlsson 《Metallurgical and Materials Transactions A》2006,37(10):2995-3007
Anisotropy of forged steel components is especially adverse when it concerns rotationally symmetric components. Manganese
sulfides (MnS) in steels may be desired for their improvement of machining properties; however, they also deteriorate fatigue
behavior. A quantification of the effect of MnS on anisotropy is necessary to find an optimum for component dimensioning.
To isolate the influence of MnS on anisotropy only, high cleanness of the test material is required. The test material in
the current investigation was molten in a vacuum furnace to high-cleanness composition. Materials with two different S levels
were produced to detect variations in anisotropy according to amount, shape, and distribution of the MnS inclusions. The two
batches were cross-rolled to plates with a deformation ratio of 4.5. The MnS phase constitutes, upon forging or rolling, pancake-shaped
inclusions. In the case of cross-rolling, an in-plane rotational symmetry of the inclusions could be created. The shape and
size of these inclusions are essential for the mechanical behavior of the material. Push-pull fatigue testing was performed
in longitudinal (in plane) and short transversal directions relative to the rolling plane. The results showed strong anisotropy
of the fatigue behavior with inferior performance in short transverse directions where the principal stress is perpendicular
to the flattened inclusions. The anisotropy was somewhat more pronounced for the high-S material, resulting from a different
fatigue crack growth mechanism. 相似文献
27.
The calculation of an electron dose distribution in a patient is a difficult problem because of the presence of tissue and surface inhomogeneities. Verification of the dose planning system is therefore essential. In this investigation, a novel method is used to evaluate a commercially available system (Helax-TMS), at electron energies between 10 and 50 MeV, both for a conventional treatment unit and an MLC-collimated scanned beam unit with a helium-filled treatment head. First, the experiments were designed to verify the local beam database and some fundamental characteristics of the electron beam calculations. Secondly, a number of generalised situations that would be encountered in the clinical treatment planning were evaluated oblique incidence, field shaping with multi-leaf collimator, bolus edges, and air cavities. Dose distributions in two generalised anatomical phantoms simulating a neck and a nose were also analysed. The results have, when so possible, been presented as the dose ratio within the 'flattened area' for dose profiles and down to the 'treatment depth' (80% dose level) for depth doses. In the penumbra region and in the dose fall-off region, the comparison has been represented by the distance deviation between calculated and measured dose profiles or depth doses. A new tool, 'volume integration', was used to evaluate the deviations from a more clinical point of view. Most results were within +/- 2% in dose for volumes larger than a sphere with a diameter of 15 mm, or +/- 2 mm in position. Dose deviations were generally found for oblique incidences and below heterogeneities such as small air cavities and bolus edges in limited volumes. 相似文献
28.
An Extended Replication of an Experiment for Assessing Methods for Software Requirements Inspections 总被引:1,自引:1,他引:0
Kristian Sandahl Ola Blomkvist Joachim Karlsson Christian Krysander Mikael Lindvall Niclas Ohlsson 《Empirical Software Engineering》1998,3(4):327-354
We have performed an extended replication of the Porter-Votta-Basili experiment comparing the Scenario method and the Checklist method for inspecting requirements specifications using identical instruments. The experiment has been conducted in our educational context represented by a more general definition of a defect compared to the original defect list. Our study involving 24 undergraduate students manipulated three independent variables: detection method, requirements specification, and the order of the inspections. The dependent variable measured is the defect detection rate. We found the requirements specification inspected and not the detection method to be the most probable explanation for the variance in defect detection rate. This suggests that it is important to gather knowledge of how a requirements specification can convey an understandable view of the product and to adapt inspection methods accordingly. Contrary to the original experiment, we can not significantly support the superiority of the Scenario method. This is in accordance with a replication conducted by Fusaro, Lanubile and Visaggio, and might be explained by the lack of individual defect detection skill of our less experienced subjects. 相似文献
29.
Jantsch Simon Müller David Baier Christel Klein Joachim 《Formal Methods in System Design》2021,58(1-2):42-82
Formal Methods in System Design - Due to the high complexity of translating linear temporal logic (LTL) to deterministic automata, several forms of “restricted” nondeterminism have been... 相似文献
30.