全文获取类型
收费全文 | 3015篇 |
免费 | 32篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 40篇 |
综合类 | 1篇 |
化学工业 | 174篇 |
金属工艺 | 20篇 |
机械仪表 | 23篇 |
建筑科学 | 24篇 |
矿业工程 | 2篇 |
能源动力 | 13篇 |
轻工业 | 119篇 |
水利工程 | 7篇 |
石油天然气 | 7篇 |
武器工业 | 2篇 |
无线电 | 234篇 |
一般工业技术 | 165篇 |
冶金工业 | 2054篇 |
原子能技术 | 3篇 |
自动化技术 | 161篇 |
出版年
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 16篇 |
2015年 | 16篇 |
2014年 | 23篇 |
2013年 | 38篇 |
2012年 | 37篇 |
2011年 | 32篇 |
2010年 | 15篇 |
2009年 | 30篇 |
2008年 | 40篇 |
2007年 | 53篇 |
2006年 | 36篇 |
2005年 | 45篇 |
2004年 | 33篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 43篇 |
2000年 | 33篇 |
1999年 | 112篇 |
1998年 | 733篇 |
1997年 | 415篇 |
1996年 | 251篇 |
1995年 | 155篇 |
1994年 | 108篇 |
1993年 | 163篇 |
1992年 | 38篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 17篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 30篇 |
1978年 | 7篇 |
1977年 | 37篇 |
1976年 | 89篇 |
1975年 | 11篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有3049条查询结果,搜索用时 187 毫秒
81.
SA de Oliveira WN Soares MO Dalston MT de Almeida AJ Costa 《Canadian Metallurgical Quarterly》1995,28(4):339-343
Malignant mesothelioma is caused almost exclusively by occupational exposure to asbestos. During the past few years, however, increasing evidence has mounted that background exposure to asbestos could be sufficient to cause mesothelioma. Treatment of malignant mesothelioma remains a big problem. Some new approaches are on their way, and the most exciting ones are local immunotherapy in very early cases. Some success has been reported with local interferon treatment. As for treatment of metastatic pleural disease, the main purpose is symptomatic relief of dyspnea caused by fluid accumulation. The best way to achieve a lasting palliation is pleurodesis, and the most common way to do this, is by chemical means. The drug of choice in the United States has for many years been tetracycline, but since injectable tetracycline is no longer available, some substitute must be found. The substance that will "win" is not yet clear, but the two leading contestants are talc and doxycycline. Bleomycin also has its supporters, and a dark horse is quinacrine, which although not easily available in the United States, has been used in many European centers for decades. 相似文献
82.
OBJECTIVE: With recent advances in molecular genetics, the rate-limiting step in identifying susceptibility genes for psychiatric disorders has become phenotype definition. The success of psychiatric genetics may require the development of a "genetic nosology" that can classify individuals in terms of the heritable aspects of psychopathology. The authors' aim is to begin to apply this analysis to the anxiety disorders, focusing on panic and phobic disorders. METHOD: Two parallel traditions of defining anxiety phenotypes are reviewed: the first, more closely identified with clinical psychiatry, has identified categorical diagnoses (e.g., panic disorder and social phobia). The other, more closely identified with psychological studies of personality development, has examined dimensional traits (e.g., neuroticism) and anxious temperament (e.g., behavioral inhibition). RESULTS: The authors suggest that a genetic nosology of panic and phobic disorders may incorporate features of both traditions and discuss strategies for optimizing genetic approaches to anxiety including 1) studying phenotypic extremes, 2) identifying biological trait markers, and 3) using animal models to identify candidate loci. CONCLUSIONS: An important dividend from the effort to define the boundaries of heritable phenotypes for genetic studies of anxiety may be a refinement of the nosology of anxiety disorders. 相似文献
83.
Sebastiani G Godtliebsen F Jones RA Haraldseth O Muller TB Rinck PA 《IEEE transactions on medical imaging》1996,15(3):268-277
Dynamic magnetic resonance (MR) imaging with contrast agents is a very promising technique for studying tissue perfusion in vivo. A temporal series of magnetic resonance images of the same slice are acquired following the injection of a contrast agent into the blood stream. The image intensity depends on the local concentration of the contrast agent, so that tissue perfusion can be studied by the image series. A new method of analyzing such series is described here. Nonparametric linear regression is used for modeling the image intensity along the series on a pixel by pixel basis. After modeling, some relevant quantities describing the time series are obtained and displayed as images. Due to its flexibility, this approach is preferred to parametric modeling when pathology is present since this can induce a wide spread of patterns for the pixel image intensity along time. Results of the application of the method to series of dynamic magnetic resonance images from ischaemic rat brains after the injection of the susceptibility agent Sprodiamide Inj. (Dy-DTPA-BMA) are shown and compared to results from a related known method. 相似文献
84.
SH Selesnick MT Abraham JF Carew 《Canadian Metallurgical Quarterly》1996,17(5):793-805; discussion 806-9
Anterior rerouting of the intratemporal facial nerve in the infratemporal fossa approach is employed to access to the jugular bulb, hypotympanum, and lateral skull base, whereas posterior rerouting of the facial nerve, as employed in the transcochlear craniotomy, is most frequently used for surgery of the posterior fossa, cerebellopontine angle, prepontine region, and petrous apex. Facial nerve rerouting may lead to facial paresis or paralysis. This review of the literature is intended to define the physiologic "cost" of these procedures, so that the neurotologic surgeon can determine if the morbidity incurred in these techniques is worth the resultant exposure. Inconsistencies in reporting facial function places into question the validity of some of the cumulative data reported. Postoperatively, grades I-II facial nerve function was seen in 91% of patients undergoing short anterior rerouting, 74% of patients undergoing long anterior rerouting, and 26% of patients undergoing posterior complete rerouting. Although facial nerve rerouting allows unhindered exposure to previously inaccessible regions, it is achieved at the cost of facial nerve function. Facial nerve dysfunction increases with the length of facial nerve rerouted. 相似文献
85.
The fluid, urgent nature of crises requires flexible, responsive information sharing. Recent studies show, however, that in business catastrophes and other kinds of crises conventional access control mechanisms favor security over flexibility. Our work addresses these seemingly contradictory needs for security and flexibility and designs a trust inference model based on fuzzy logic, a model that can be used with pervasive computing technologies using sensors and mobile devices. Drawing upon research on trust, we design a trust inference model using attributes of affiliation, task performance, and urgency; apply the model to a known crisis; discuss implementation issues; and explore issues for further research. This article is dedicated to Alan Jarman, a founding influence in the Journal of Contingencies and Crisis Management who died in Canberra 15 July 2010. Alan's quantitative, engineering background and his long standing commitment to improving crisis decision making prompted him to encourage our applying fuzzy logic to crisis information sharing. We are grateful for Alan's encouragement and advice. 相似文献
86.
87.
Tegawendé F. Bissyandé Laurent Réveillère Julia L. Lawall Gilles Muller 《Automated Software Engineering》2016,23(1):3-41
The Linux kernel does not export a stable, well-defined kernel interface, complicating the development of kernel-level services, such as device drivers and file systems. While there does exist a set of functions that are exported to external modules, this set of functions frequently changes, and the functions have implicit, ill-documented preconditions. No specific debugging support is provided. We present Diagnosys, an approach to automatically constructing a debugging interface for the Linux kernel. First, a designated kernel maintainer uses Diagnosys to identify constraints on the use of the exported functions. Based on this information, developers of kernel services can then use Diagnosys to generate a debugging interface specialized to their code. When a service including this interface is tested, it records information about potential problems. This information is preserved following a kernel crash or hang. Our experiments show that the generated debugging interface provides useful log information and incurs a low performance penalty. 相似文献
88.
In the cold, Purdue Pegboard (PP) performance declines. The purpose of this study was to determine if this cold-induced impairment is consistent across days (i.e. test-retest reliability) in 5°C. In thermoneutral air (25°C), 14 men were familiarised to the dominant hand (PPa) and bimanual (PPb) PP tasks. They then experienced two 90-min cold exposures (Day 1, Day 2) while wearing ~1 clo. Bare hands were maintained throughout. Performance on both tasks showed high reliability from day to day (intraclass correlations >0.700) in both thermoneutral and cold conditions. However for both tasks, room temperature performance did not predict performance in the cold (intraclass correlations <0.450). When screening applicants for manual labour in the cold, one must consider that room temperature dexterity does not correlate with dexterity in the cold. It is recommended that a 60-min period of cold exposure be employed to assess manual dexterity in these workers. STATEMENT OF RELEVANCE: This study shows that PP performance in room temperature does not predict performance in the cold but performance in the cold is consistent from day to day. When screening applicants for manual labour in the cold, it is recommended that dexterity tests be conducted in the same ambient conditions. 相似文献
89.
Steven Hancock Mathias Disney Jan-Peter Muller Philip Lewis Mike Foster 《Remote sensing of environment》2011,115(12):3286-3297
Lidars have the unique ability to make direct, physical measurements of forest height and vertical structure in much denser canopies than is possible with passive optical or short wavelength radars. However the literature reports a consistent underestimate of tree height when using physically based methods, necessitating empirical corrections. This bias is a result of overestimating the range to the canopy top due to background noise and failing to correctly identify the ground.This paper introduces a method, referred to as “noise tracking”, to avoid biases when determining the range to the canopy top. Simulated waveforms, created with Monte-Carlo ray tracing over geometrically explicit forest models, are used to test noise tracking against simple thresholding over a range of forest and system characteristics. It was found that noise tracking almost completely removed the bias in all situations except for very high noise levels and very low (< 10%) canopy covers. In all cases noise tracking gave lower errors than simple thresholding and had a lower sensitivity to the initial noise threshold.Finite laser pulses spread out the measured signal, potentially overriding the benefit of noise tracking. In the past laser pulse length has been corrected by adding half that length to the signal start range. This investigation suggests that this is not always appropriate for simple thresholding and that the results for noise tracking were more directly related to pulse length than for simple thresholding. That this effect has not been commented on before may be due to the possible confounding impacts of instrument and survey characteristics inherent in field data. This method should help improve the accuracy of waveform lidar measurements of forests, whether using airborne or spaceborne instruments. 相似文献
90.
A thin-film micromolding process enabled the construction of microtorsional springs with unique cross-sectional designs by combining high-aspect-ratio beams with horizontal surface features. Cross sections such as T-bars, pi sections, and channels were utilized in creating torsional springs with low torsional stiffnesses and high in- and out-of-plane bending stiffnesses. Experimental modal analysis was used to determine torsional stiffnesses as low as 0.13 μN·m/deg with T-bar springs 45 μm tall, 50 μm wide, and 100 μm long. Springs of the same outer dimensions but with solid rectangular cross sections were calculated to have torsional stiffnesses of at least two orders of magnitude greater. Several microgimbals were constructed using the thin-film micromolding process with various torsional spring designs. Modal analysis was used to experimentally determine pitch and roll natural frequencies. Torsional stiffness models for open, thin-walled sections that included warping effects were developed and used to analytically predict the torsional natural frequencies of tested spring designs to within 20% 相似文献