全文获取类型
收费全文 | 268193篇 |
免费 | 5259篇 |
国内免费 | 2964篇 |
专业分类
电工技术 | 6359篇 |
技术理论 | 6篇 |
综合类 | 2042篇 |
化学工业 | 37748篇 |
金属工艺 | 11690篇 |
机械仪表 | 9199篇 |
建筑科学 | 8128篇 |
矿业工程 | 1326篇 |
能源动力 | 7183篇 |
轻工业 | 24386篇 |
水利工程 | 2199篇 |
石油天然气 | 2674篇 |
武器工业 | 175篇 |
无线电 | 37361篇 |
一般工业技术 | 50146篇 |
冶金工业 | 49261篇 |
原子能技术 | 3811篇 |
自动化技术 | 22722篇 |
出版年
2022年 | 1568篇 |
2021年 | 2407篇 |
2020年 | 1819篇 |
2019年 | 2104篇 |
2018年 | 2788篇 |
2017年 | 2936篇 |
2016年 | 3042篇 |
2015年 | 2895篇 |
2014年 | 4366篇 |
2013年 | 12167篇 |
2012年 | 7086篇 |
2011年 | 9747篇 |
2010年 | 7621篇 |
2009年 | 8675篇 |
2008年 | 9324篇 |
2007年 | 9635篇 |
2006年 | 8815篇 |
2005年 | 8049篇 |
2004年 | 7464篇 |
2003年 | 7164篇 |
2002年 | 6918篇 |
2001年 | 7123篇 |
2000年 | 6670篇 |
1999年 | 7067篇 |
1998年 | 16094篇 |
1997年 | 11439篇 |
1996年 | 9308篇 |
1995年 | 6955篇 |
1994年 | 6234篇 |
1993年 | 5896篇 |
1992年 | 4381篇 |
1991年 | 4228篇 |
1990年 | 4094篇 |
1989年 | 3873篇 |
1988年 | 3596篇 |
1987年 | 2992篇 |
1986年 | 2969篇 |
1985年 | 3406篇 |
1984年 | 3081篇 |
1983年 | 2854篇 |
1982年 | 2727篇 |
1981年 | 2631篇 |
1980年 | 2386篇 |
1979年 | 2316篇 |
1978年 | 2142篇 |
1977年 | 2591篇 |
1976年 | 3480篇 |
1975年 | 1855篇 |
1974年 | 1680篇 |
1973年 | 1696篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes. 相似文献
92.
A temperature sensor using a fiber-optic Fabry-Perot interferometer is described. A pseudo-heterodyne detection scheme is adopted to read the light phase difference in the Fabry-Perot interference output. A higher harmonic components comparison method is used to stabilize the system and to increase detection linearity. This system realizes not only highly sensitive temperature sensing with good linearity and minimal adjusting error, but also application to the sensing of other physical quantities such as vibrations. Additionally, the signal-to-noise ratio and distortion of the detected signal are investigated as functions of fiber end reflectivity. These results will be useful in designing a high performance fiber-optic Fabry-Perot thermometer. 相似文献
93.
Y. Rey-Tauriac J. Badoc B. Reynard R.A. Bianchi D. Lachenal A. Bravaix 《Microelectronics Reliability》2005,45(9-11):1349
This paper presents results of reliability investigation of 20 V N-Drift MOS transistor in 0.13 μm CMOS technology. Due to high performances required for CMOS applications, adding high voltage devices becomes a big challenge to guarantee the reliability criteria. In this context, new reliability approaches are needed. Safe Operating Area are defined for switch, Vds limited and Vgs limited applications in order to improve circuit designs. For Vds limited applications, deep doping dose effects in drift area are investigated in correlation to lifetime evaluations based on device parameter shifts under hot carrier stressing. To further determine the amount and locations of hot carriers injections, accurate 2D technological and electrical simulations are performed and permit to select the best compromise between performance and reliability for N-Drift MOS transistor. 相似文献
94.
This paper discusses another generalization of the direct Routh table truncation method for interval systems. It is shown that the existing generalization of the direct Routh table truncation fails to produce a stable system, in contradiction to the equivalent result for fixed-coefficients systems. The present method guarantees a stable reduced order model for interval systems as well. 相似文献
95.
96.
The US Centers for Disease Control and Prevention (CDC) created the Public Health Information Network to advance fully capable, interoperable information systems in public health organizations. PHIN prioritizes public health information systems' functional requirements, capabilities, performance measures, and operational characteristics while letting the architects of those systems choose enabling approaches, methods, and concepts to meet the requirements. PHIN also provides a certification process for public health administrators to evaluate their information infrastructure's quality. The certification process is important because affected organizations often depend on certification for continued funding. 相似文献
97.
Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2-coated and non-coated surfaces were used for comparison. In the case of the TiO2-coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
98.
99.
A survey of the state of SQA in Japan finds that the situation is much like, but slightly different than, that in the US. 相似文献
100.
We introduce a new probabilistic approach to dealing with uncertainty, based on the observation that probability theory does not require that every event be assigned a probability. For a nonmeasurable event (one to which we do not assign a probability), we can talk about only the inner measure and outer measure of the event. In addition to removing the requirement that every event be assigned a probability, our approach circumvents other criticisms of probability-based approaches to uncertainty. For example, the measure of belief in an event turns out to be represented by an interval (defined by the inner and outer measures), rather than by a single number. Further, this approach allows us to assign a belief (inner measure) to an event E without committing to a belief about its negation -E (since the inner measure of an event plus the inner measure of its negation is not necessarily one). Interestingly enough, inner measures induced by probability measures turn out to correspond in a precise sense to Dempster-Shafer belief functions. Hence, in addition to providing promising new conceptual tools for dealing with uncertainty, our approach shows that a key part of the important Dempster-Shafer theory of evidence is firmly rooted in classical probability theory. Cet article présente une nouvelle approche probabiliste en ce qui concerne le traitement de l'incertitude; celle-ci est basée sur l'observation que la théorie des probabilityés n'exige pas qu'une probabilityé soit assignée à chaque événement. Dans le cas d'un événement non mesurable (un événement pour lequel on n'assigne aucune probabilityé), nous ne pouvons discuter que de la mesure intérieure et de la mesure extérieure de l'évenément. En plus d'éliminer la nécessité d'assigner une probabilityéà l'événement, cette nouvelle approche apporte une réponse aux autres critiques des approches à l'incertitude basées sur des probabilityés. Par exemple, la mesure de croyance dans un événement est représentée par un intervalle (défini par la mesure intérieure et extérieure) plutǒt que par un nombre unique. De plus, cette approche nous permet d'assigner une croyance (mesure intérieure) à un événement E sans se compromettre vers une croyance à propos de sa négation -E (puisque la mesure intérieure d'un événement et la mesure intérieure de sa négation ne sont pas nécessairement une seule et unique mesure). II est intéressant de noter que les mesures intérieures qui résultent des mesures de probabilityé correspondent d'une manière précise aux fonctions de croyance de Dempster-Shafer. En plus de constituer un nouvel outil conceptuel prometteur dans le traitement de l'incertitude, cette approche démontre qu'une partie importante de la théorie de l'évidence de Dempster-Shafer est fermement ancrée dans la theorie classique des probabilityés. 相似文献