全文获取类型
收费全文 | 4000篇 |
免费 | 204篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 76篇 |
综合类 | 6篇 |
化学工业 | 1100篇 |
金属工艺 | 102篇 |
机械仪表 | 82篇 |
建筑科学 | 190篇 |
矿业工程 | 3篇 |
能源动力 | 74篇 |
轻工业 | 388篇 |
水利工程 | 15篇 |
石油天然气 | 6篇 |
无线电 | 332篇 |
一般工业技术 | 743篇 |
冶金工业 | 546篇 |
原子能技术 | 36篇 |
自动化技术 | 511篇 |
出版年
2023年 | 22篇 |
2022年 | 58篇 |
2021年 | 79篇 |
2020年 | 54篇 |
2019年 | 62篇 |
2018年 | 76篇 |
2017年 | 81篇 |
2016年 | 96篇 |
2015年 | 94篇 |
2014年 | 123篇 |
2013年 | 181篇 |
2012年 | 159篇 |
2011年 | 232篇 |
2010年 | 146篇 |
2009年 | 151篇 |
2008年 | 185篇 |
2007年 | 164篇 |
2006年 | 147篇 |
2005年 | 120篇 |
2004年 | 106篇 |
2003年 | 117篇 |
2002年 | 92篇 |
2001年 | 78篇 |
2000年 | 74篇 |
1999年 | 78篇 |
1998年 | 154篇 |
1997年 | 103篇 |
1996年 | 100篇 |
1995年 | 70篇 |
1994年 | 52篇 |
1993年 | 63篇 |
1992年 | 45篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 38篇 |
1988年 | 48篇 |
1987年 | 32篇 |
1986年 | 50篇 |
1985年 | 45篇 |
1984年 | 41篇 |
1983年 | 35篇 |
1982年 | 34篇 |
1981年 | 38篇 |
1980年 | 29篇 |
1979年 | 28篇 |
1978年 | 34篇 |
1977年 | 38篇 |
1976年 | 49篇 |
1974年 | 29篇 |
1973年 | 21篇 |
排序方式: 共有4210条查询结果,搜索用时 15 毫秒
1.
Knaust Thiemo Felnhofer Anna Kothgassner Oswald D. Hllmer Helge Gorzka Robert-Jacek Schulz Holger 《Virtual Reality》2022,26(3):925-938
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,... 相似文献
2.
3.
Pavel Strunz Debashis Mukherji Přemysl Beran Ralph Gilles Lukas Karge Michael Hofmann Markus Hoelzel Joachim Rösler Gergely Farkas 《Metals and Materials International》2018,24(5):934-944
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content. 相似文献
4.
A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules. 相似文献
5.
M. Ganschow C. Hellriegel E. Kneuper M. Wark C. Thiel G. Schulz‐Ekloff C. Bruchle D. Whrle 《Advanced functional materials》2004,14(3):269-276
Dye‐loaded AlPO4‐5 single crystals were prepared by microwave‐assisted hydrothermal synthesis from a batch, containing a mixture of three chromophores (Coumarin 40, Rhodamine BE50, and Oxazine 1) differing in their absorption range, molecular dimensions, and solubilities. Confocal fluorescence images reveal a spatial separation effect of the dye molecules, where the slimmer, more‐soluble dye molecule (Coumarin 40) is uniformly distributed in the body of the single crystal, and the bulky and/or less‐soluble ones (Rhodamine BE50, Oxazine 1) are situated in distinct domains. Visible spectra show good panchromatic absorption of visible light. Fluorescence lifetime measurements indicate the presence of an energy transfer cascade of the entirely fixed dye molecules from Coumarin 40 to Oxazine 1. The transfer mechanism is predominantly radiative. 相似文献
6.
7.
L. Ya. Karachinsky T. Kettler N. Yu. Gordeev I. I. Novikov M. V. Maximov Yu. M. Shernyakov N. V. Kryzhanovskaya A. E. Zhukov E. S. Semenova A. P. Vasil’ev V. M. Ustinov N. N. Ledentsov A. R. Kovsh V. A. Shchukin S. S. Mikhrin A. Lochmann O. Schulz L. Reissmann D. Bimberg 《Semiconductors》2005,39(12):1415-1419
Lasers based on InAs/InGaAs quantum dots grown on metamorphic (In,Ga,Al)As layers deposited by MBE on GaAs substrates exhibited emission near 1.5 μm with a differential quantum efficiency of about 50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm?2 without significant degradation. A maximum continuous-wave output power of 220 mW is obtained. Neither current nor beam filamentation was observed up to the highest pumping levels. 相似文献
8.
9.
Matthias Zobel Joachim Denzler Benno Heigl Elmar Nöth Dietrich Paulus Jochen Schmidt Georg Stemmer 《Machine Vision and Applications》2003,14(1):26-34
Abstract. This contribution introduces MOBSY, a fully integrated, autonomous mobile service robot system. It acts as an automatic dialogue-based
receptionist for visitors to our institute. MOBSY incorporates many techniques from different research areas into one working
stand-alone system. The techniques involved range from computer vision over speech understanding to classical robotics.
Along with the two main aspects of vision and speech, we also focus on the integration aspect, both on the methodological
and on the technical level. We describe the task and the techniques involved. Finally, we discuss the experiences that we
gained with MOBSY during a live performance at our institute. 相似文献
10.
T Koperna S Vogl U Satzinger F Schulz 《Canadian Metallurgical Quarterly》1997,21(8):850-4; discussion 854-5
Nonparasitic cysts of the liver (NPHC) are highly variable in respect to appearance and therapeutic approach. The treatment of these cysts varies according to the nature and appearance of the disease. Based on the variable nature of disease and the various therapeutic options, all of which were attempted in our patients, the most suitable mode of treatment for different forms of NPHC are discussed. Ninety-one patients with NPHC who had been treated surgically from 1977 through 1995 were examined retrospectively. Asymptomatic peripheral cysts measuring up to 10 cm do not require further treatment. Computed tomography (CT)-guided aspiration (n = 9) should be regarded as a palliative measure. Within a short period, CT-guided aspiration led to recurrence of symptoms in seven of our patients. Standard treatment of NPHC is fenestration with widest possible excision of the cystic wall, which can be performed laparoscopically (n = 10) or by the conventional surgical mode (n = 54). One patient was initially operated by the laparoscopic technique but developed bleeding, which necessitated conversion to the open mode. Three patients underwent synchronous laparoscopic cholecystectomy. Recurrence rates were similar: 11% in the laparoscopically treated group and 13% in the group that underwent conventional open surgery. Conventional surgical treatment was always successful in cases of solitary cysts. However, in cases of multiple cysts measuring more than 5 cm, conventional surgery was followed by recurrence of symptoms in 26% of patients (7/27), who then had to undergo a second operation. Partial resection of the liver (n = 9) was successfully performed in cases of polycystic disease (n = 5) with concomitant enlargement of the organ as well as in cases of large solitary cysts of the left lobe of the liver (n = 4). In patients in whom we found that the cysts communicated with the ductal system (n = 3), we performed a cystojejunostomy to drain the bile. The complication rate was low. In addition to frequent postoperative ascites, which necessitated no further intervention, we observed infectious complications in four patients. Twenty patients (22%) expired during a mean follow-up period of 6.2 years. Interestingly, deaths were frequently associated with malignancy (11/20). After fenestration of multiple cysts measuring > 5 cm, the patients are at high risk for recurrence. Hence partial resection of the liver is an excellent therapeutic alternative in selected patients with polycystic disease and massive enlargement of the organ in whom the disease could not be controlled by simple fenestration. The results of this study show that laparoscopic fenestration should replace the conventional surgical technique as the gold standard in cases of NPHC because the laparoscopic technique is less stressful for the patient and is associated with a rate of success similar to that of the conventional technique. 相似文献