全文获取类型
收费全文 | 1812篇 |
免费 | 147篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 99篇 |
综合类 | 4篇 |
化学工业 | 490篇 |
金属工艺 | 29篇 |
机械仪表 | 36篇 |
建筑科学 | 67篇 |
矿业工程 | 7篇 |
能源动力 | 51篇 |
轻工业 | 153篇 |
水利工程 | 9篇 |
石油天然气 | 3篇 |
无线电 | 157篇 |
一般工业技术 | 339篇 |
冶金工业 | 177篇 |
原子能技术 | 7篇 |
自动化技术 | 333篇 |
出版年
2023年 | 45篇 |
2022年 | 69篇 |
2021年 | 102篇 |
2020年 | 81篇 |
2019年 | 70篇 |
2018年 | 71篇 |
2017年 | 67篇 |
2016年 | 68篇 |
2015年 | 54篇 |
2014年 | 96篇 |
2013年 | 132篇 |
2012年 | 91篇 |
2011年 | 120篇 |
2010年 | 77篇 |
2009年 | 79篇 |
2008年 | 78篇 |
2007年 | 68篇 |
2006年 | 67篇 |
2005年 | 42篇 |
2004年 | 33篇 |
2003年 | 41篇 |
2002年 | 32篇 |
2001年 | 18篇 |
2000年 | 9篇 |
1999年 | 22篇 |
1998年 | 60篇 |
1997年 | 48篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 25篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 10篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 12篇 |
1972年 | 4篇 |
1943年 | 4篇 |
1942年 | 3篇 |
1940年 | 3篇 |
排序方式: 共有1961条查询结果,搜索用时 31 毫秒
991.
Sanchez E.N. Loukianov A.G. Felix R.A. 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2002,32(1):24-30
We present a novel neural controller for a stepper motor. This controller is developed as follows. Modifying published results for nonlinear identification using dynamic neural networks (NNs), an NN identifier of triangular form is implemented. Then, based on this mode, a control law using sliding modes is derived. This neural identifier and the proposed control law allow trajectory tracking for stepping motors. Applicability of the approach is tested via simulations 相似文献
992.
We provide an estimation of the additional need for underground storage facilities in northwestern Europe until 2030. 相似文献
993.
N Hosten N Bornfeld AJ Lemke B Sander R Wassmuth R Felix 《Canadian Metallurgical Quarterly》1997,18(9):1788-1790
MR imaging with retrobulbar anesthesia was performed in eight patients with uveal melanoma. Injection of 2 mL prilocain hydrochloride in 2% epinephrin into the eye muscle cone resulted in improved image quality in seven patients, without side effects. Ocular MR imaging can be indicated to clarify indeterminate sonographic findings in cases of extrascleral growth or to exclude optic nerve invasion in patients with tumors located at the posterior pole of the globe. 相似文献
994.
SPROUT is a new computer program for constrained structure generation that is designed to generate molecules for a range of applications in molecular recognition. It uses artificial intelligence techniques to moderate the combinatorial explosion that is inherent in structure generation. The program is presented here for the design of enzyme inhibitors. Structure generation is divided into two phases: (i) primary structure generation to produce molecular graphs to fit the steric constraints; and (ii) secondary structure generation which is the process of introducing appropriate functionality to the graphs to produce molecules that satisfy the secondary constraints, e.g., electrostatics and hydrophobicity. Primary structure generation has been tested on two enzyme receptor sites; the p-amidino-phenyl-pyruvate binding site of trypsin and the acetyl pepstatin binding site of HIV-1 protease. The program successfully generates structures that resemble known substrates and, more importantly, the predictive power of the program has been demonstrated by its ability to suggest novel structures. 相似文献
995.
CT examinations of the liver in HIV-infected patients show more frequent pathological findings. The extended spectrum of differential diagnosis and atypical manifestations of disorders in immunodeficient patients needs to be considered in the interpretation of CT scans. Difficulties in the differential diagnosis of focal hepatic lesions in HIV-infected patients are demonstrated in the following. Besides the relatively common findings in HIV-infection such as hepato-or hepatosplenomegalia, lymphoma, and inflammatory changes of the bowel an infection with Cryptococcus neoformans, hepatitis, and local steatosis of the liver are discussed as the rare causes for suspect computertomographic findings in the live of HIV-infected patients. The examinations were obtained consecutively in 76 HIV-infected patients during abdominal CT staging. 相似文献
996.
Werner H?hnel Ibrahim Jussofie Felix Müller 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,200(4):244-246
High-resolution infrared (IR) spectra of emulsifiers for yeast-leavened bread were measured together with those of the individual components of wheat flour. Using the IR reflection technique, the entire dough was also investigated to give an insight into the development of structures in dough. The emulsifiers react with different components of wheat flour in a specific way. Using IR spectroscopy exact data for the strength of bonding and the kind of bonding between emulsifier and dough component can be obtained.
Part I: Ref. [4] 相似文献
Infrarotspektroskopische Untersuchungen zur Wirkung von Emulgatoren in Hefebackwaren. II. Versuche zur Wirkung von Emulgatoren auf Stärke, Mehl und im Teig
Zusammenfassung Emulgatoren, Weizenmehlinhaltsstoffe und Hefeteig wurden mit FT-IR-Spektroskopie in Transmission bzw. Reflexion gemessen. Es konnte anhand der Verschiebung der Carbonylabsorption gezeigt werden, wie verschiedene Emulgatoren mit unterschiedlichen Substraten in Wechselwirkung treten, so daß ihre Wirkung spezifisch ist. Die Wirksamkeit einzelner Emulgatoren kann mittels IR-Spektroskopie parametrisiert werden.
Part I: Ref. [4] 相似文献
997.
998.
A.T. Mata C. Proença A.R. Ferreira M.L.M. Serralheiro J.M.F. Nogueira M.E.M. Araújo 《Food chemistry》2007,103(3):778-786
In the present work, we report the results of a study aimed at evaluating the antiradical activity, the antioxidant activity and the acetylcholinesterase (E.C. 3.1.1.7.) inhibitory capacity of essential oils, ethanol and boiling water extracts from five aromatic herbs growing wild in Portugal and used in traditional food preparations: fennel (Foeniculum vulgare), mint (Mentha spicata), pennyroyal (Mentha pulegium), rosemary (Rosmarinus officinalis) and wild thyme (Thymus serpyllum). The water extracts of M. spicata and M. pulegium showed the highest radical-scavenging activity (DPPH test) values (IC50 = 5.7 ± 0.4 and 8.9 ± 0.2 μg ml−1 respectively). This activity was higher than that found with the standard antioxidant BHT. The ethanol extracts of M. spicata, T. serpyllum and F. vulgare showed the highest antioxidant activities measured by the β-carotene/linoleic acid assay, IC50 = 36.9 ± 0.1, 41.2 ± 0.1 and 68.7 ± 0.1 μg ml−1, respectively. The inhibition of AChE was higher in the essential oil fraction. The highest activity was found for R. officinalis with an IC50 = 69.8 ± 0.1 μg ml−1. 相似文献
999.
Supporting Fair Exchange in Mobile Environments 总被引:1,自引:0,他引:1
Mobile commerce over the Internet always includes the exchange of electronic goods. Fair exchange protocols establish fairness and ensure that both participants can engage in the exchange without the risk of suffering a disadvantage (e.g., losing their money without receiving anything for it). In general, fair exchange protocols require the continuous availability of an external trusted third party (TTP), a dedicated site which is trusted by both participants. Implementations of TTPs for fair exchange have been proposed to be based on carefully secured Internet hosts in order to establish trust. In this paper we present solutions to the fair exchange problem in mobile environments, where customers frequently disconnect from the network and thus continuous availability of the external TTP is not given. Our approach utilizes tamper-poof hardware on the customer's side partly taking over the duties of the TTP. Besides supporting disconnected operations our approach also allows the proper handling of time-sensitive items (i.e., items which lose value over time), a feature which previous protocols lack. 相似文献
1000.
Hoerger CC Wettstein FE Bachmann HJ Hungerbühler K Bucheli TD 《Environmental science & technology》2011,45(16):6752-6760
Isoflavones and coumestrol (COU) are estrogenic compounds that are naturally produced by plants (e.g., red clover, soybeans). Although these compounds have been extensively studied in food and feed, only little is known about their environmental fate. Therefore, we investigated the occurrence of isoflavones (formononetin, daidzein, equol, biochanin A, and genistein) and COU over 3.5 years in red clover, manure, and soil of a grassland field with and without manure application, as well as their emission via drainage water. Isoflavones were regularly quantified in plant (≤ 15 × 10(6) ng/g(dry weight (dw))), manure (≤ 230 × 10(3) ng/g(dw)), soil (≤ 3.4 × 10(3) ng/g(dw)), and drainage water samples (≤ 3.6 × 10(3) ng/L). In contrast, COU was observed only in manure and soil. Cumulative isoflavone loads emitted via drainage water were around 0.2 × 10(-3) kg/ha/y, which is very little compared to the amounts present in red clover (105-220 kg/ha/y), manure (0.5-1.0 kg/ha/y), and soil (0.1-5.1 kg/ha/y). Under good agricultural practice, no additional emission of isoflavones into drainage water was observed after manure application. With calculated 17β-estradiol equivalents up to 0.46 ng/L in drainage water, isoflavones can constitute a dominant and ecotoxicological relevant portion of the total estrogenicity in small rural river catchments. 相似文献