全文获取类型
收费全文 | 746篇 |
免费 | 60篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 12篇 |
综合类 | 9篇 |
化学工业 | 172篇 |
金属工艺 | 10篇 |
机械仪表 | 15篇 |
建筑科学 | 23篇 |
矿业工程 | 15篇 |
能源动力 | 19篇 |
轻工业 | 62篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
武器工业 | 3篇 |
无线电 | 163篇 |
一般工业技术 | 123篇 |
冶金工业 | 69篇 |
原子能技术 | 5篇 |
自动化技术 | 99篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 19篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 18篇 |
2013年 | 36篇 |
2012年 | 26篇 |
2011年 | 46篇 |
2010年 | 39篇 |
2009年 | 25篇 |
2008年 | 38篇 |
2007年 | 35篇 |
2006年 | 22篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 29篇 |
2001年 | 40篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 32篇 |
1997年 | 19篇 |
1996年 | 21篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有813条查询结果,搜索用时 0 毫秒
101.
A room-based diagnostic x-ray imaging system for routine measurement of radiotherapy patient orientation has been developed. The system consists of a pair of room-mounted x-ray tubes and a portable imager consisting of an orthogonal pair of phosphor screens, a mirror/lens system, a CCD camera, and computer software for comparing images of the patient to reference images. Orthogonal pairs of images can be acquired quickly and with relatively little exposure, allowing correction of patient setup on a daily basis. This could limit patient setup error to the uncertainty in the measurement and repositioning processes, a potentially significant improvement over the present standard. 相似文献
102.
A modified approach is presented for the design of Lyapunov model reference adaptive systems. The approach introduces the use of a function of the parameter misalignment, which can be generated with minor demands for additional hardware. Simulation confirms the acceleration in convergence of the system error compared to previous design procedures. 相似文献
103.
The influence of horn length on the radiation pattern of an oblique-flare-angle corrugated horn is described. Two experiments with a 110° horn are reported. These show that a horn with three slots has a radiation pattern which is essentially the same as that of a horn with five slots. It is also demonstrated that the innermost slot has a dominant effect on the pattern. 相似文献
104.
I Schipper FF Rommerts PM Ten Hacken BC Fauser 《Canadian Metallurgical Quarterly》1997,82(5):1325-1331
In patients with normogonadotropic anovulation, either with or without polycystic ovary syndrome (PCOS), factors interfering with FSH action may be involved in arrested follicle development. The aim of this study is to assess whether factors inhibiting FSH receptor activation are elevated in serum or follicular fluid from anovulatory patients, as compared with regularly cycling women. For this purpose, a Chinese hamster ovary cell line, stably transfected with the human FSH receptor, has been applied. FSH-stimulated cAMP secretion in culture medium was measured in the presence of serum or follicular fluid. Chinese hamster ovary cells were stimulated with a fixed concentration of FSH (3 or 6 mIU/mL) to mimic FSH levels in serum or follicular fluid. Samples were added in concentrations ranging from 3-90% vol/vol to approach protein concentrations occurring in serum or follicular fluid. In the presence of 10% vol/vol serum from regularly cycling women (n = 8), FSH-stimulated cAMP production was inhibited to 42 +/- 2% (mean +/- SEM of 2 experiments, each performed in duplicate) of cAMP production in the absence of serum, whereas a similar cAMP level (up to 38 +/- 4% of the serum-free level) was observed at higher concentrations of serum (30-90% vol/vol). The inhibition of FSH-stimulated cAMP production in the presence of serum samples from normogonadotropic anovulatory patients, without (n = 13) or with (n = 16) PCOS, was similar to controls. Follicular fluid samples (n = 57) obtained during the follicular phase in 25 regularly cycling women and follicular fluid samples (n = 25) from 5 PCOS patients were tested in a slightly modified assay system. In the presence of 10 or 30% (vol/vol) follicular fluid, FSH-stimulated cAMP levels were decreased to 68 +/- 2% and 55 +/- 2% (mean +/- SEM of a single experiment in triplicate) of the cAMP levels in the absence of follicular fluid, respectively. There was no correlation between the degree of cAMP inhibition and follicle size, steroid content (androstenedione or estradiol concentrations), or menstrual cycle phase. Furthermore, no differences in inhibition were found, comparing PCOS follicles with size- and steroid content-matched follicles obtained during the normal follicular phase. It is concluded that inhibition of FSH receptor activation by proteins present in serum or follicular fluid is constant (60 and 40%, respectively) and independent from the developmental stage of the follicle, either during the normal follicular phase or in patients with normogonadotropic anovulation. Inhibition of FSH receptor activation may be of limited significance for normal and arrested follicle development. 相似文献
105.
A problem in the earth sciences is to reduce a sequence of observation vectors X1, X2, …, XN to a set of internally homogeneous segments or zones. This paper uses the model that the observation vectors in the ith zone are a random sample from the multivariate normal N(ξi, Σi) distribution. It is demonstrated that the maximum likelihood estimates of the boundaries between zones may be determined by dynamic programming, and a FORTRAN algorithm to perform this estimation is given. 相似文献
106.
KG Ten Hagen FK Hagen MM Balys TM Beres B Van Wuyckhuyse LA Tabak 《Canadian Metallurgical Quarterly》1998,273(42):27749-27754
We report the cloning and expression of the fifth member of the mammalian UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (ppGaNTase) family. Degenerate polymerase chain reaction amplification and hybridization screening of a rat sublingual gland (RSLG) cDNA library were used to identify a novel isoform termed ppGaNTase-T5. Conceptual translation of the cDNA reveals a uniquely long stem region not observed for other members of this enzyme family. Recombinant proteins expressed transiently in COS7 cells displayed transferase activity in vitro. Relative activity and substrate preferences of ppGaNTase-T5 were compared with previously identified isoforms (ppGaNTase-T1, -T3, and -T4); ppGaNTase-T5 and -T4 glycosylated a restricted subset of peptides whereas ppGaNTase-T1 and -T3 glycosylated a broader range of substrates. Northern blot analysis revealed that ppGaNTase-T5 is expressed in a highly tissue-specific manner; abundant expression was seen in the RSLG, with lesser amounts of message in the stomach, small intestine, and colon. Therefore, the pattern of expression of ppGaNTase-T5 is the most restricted of all isoforms examined thus far. The identification of this novel isoform underscores the diversity and complexity of the family of genes controlling O-linked glycosylation. 相似文献
107.
Richard P. Ten Dyke 《Information Systems Management》1984,1(4):10-16
Expert systems, a form of artificial intelligence (Al), are emerging as a practical use of computers and data bases in a range of applications. The use of Al potentially can improve the accuracy, timeliness, and quality of decision making in those jobs that are performed by several persons, that involve repetitive tasks requiring human judgment, and that can be done best by an expert. Like any tool, however, expert systems have limitations that must be considered before a project is undertaken. 相似文献
108.
Seng?Wai?LokeEmail author Shonali?Krishnaswamy Thin?Thin?Naing 《Mobile Networks and Applications》2005,10(4):395-404
We investigate ambient services, which we define as services that are related to the surrounding physical environment of the user, are locally useful and can be considered a form of location-based services. We introduce the notion of service domain which refers to the geographical area of relevance and utility for ambient services. We also consider a stereotypical case where a user might be within multiple service domains at the same time (when the service domains containing the user overlap) and so, can utilize a collection of services comprising services selected from each of the service domains containing the user. A language of operators is given for defining such a collection of services in terms of constituent services from the overlapping service-domains. Moreover, we describe and evaluate a prototype system that shows how to compute the services for a user in multiple service domains. The result is a framework for reasoning about ambient services for filtering or proactively suggesting mobile services based on geographical boundaries.
Seng Wai Loke is a Faculty of Information Technology Research Fellow at Monash University. He is author and co-author of more than 90 research papers published in journals, books, conferences, and workshops. His research interests are intelligent and mobile agents, service-oriented computing, and pervasive computing including device ecologies, context-aware systems, mobile services, and ubiquitous e-commerce. He has been on the program committee of more than ten conferences and workshops in the area of mobile computing and agents.
Shonali Krishnaswamy received a PhD in Computer Science from Monash University (Australia) in 2003. She currently holds the position of a Research Fellow in the School of Computer Science and Software Engineering at Monash University. Her research interests include Service Oriented Systems, Software Agents and Distributed/Ubiquitous Data Mining. She is a member of ACM and IEEE Computer Societies.
Thin Thin Naing has completed her Masters by Information Technology (MIT by Minor Thesis) from the School of Computer Science and Software Engineering at Monash University, Australia. Her research interests include Mobile Services, Location-based Services and Ambient services.This revised version was published online in August 2005 with a corrected cover date. 相似文献
109.
Beng Tan Swan Seng Yang Kin Choo Loy Wei 《Bulletin of Engineering Geology and the Environment》1982,26(1):321-326
Bulletin of Engineering Geology and the Environment - Geophysical methods of site investigation have been used in civil engineering for many years. Of these methods, seismic refraction survey is... 相似文献
110.
Wende Un C. Seng 《Journal of the American Oil Chemists' Society》1980,57(12):926A-928A
Systems and practices for successful treatment of edible oil refinery wastewater are reviewed, including: total plant good
housekeeping, conservation of water usage, integrated system design, by-product handling, and process control and operation. 相似文献