全文获取类型
收费全文 | 9032篇 |
免费 | 316篇 |
国内免费 | 40篇 |
专业分类
电工技术 | 123篇 |
综合类 | 22篇 |
化学工业 | 2109篇 |
金属工艺 | 167篇 |
机械仪表 | 230篇 |
建筑科学 | 573篇 |
矿业工程 | 31篇 |
能源动力 | 171篇 |
轻工业 | 776篇 |
水利工程 | 54篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 596篇 |
一般工业技术 | 1449篇 |
冶金工业 | 1526篇 |
原子能技术 | 70篇 |
自动化技术 | 1479篇 |
出版年
2023年 | 59篇 |
2022年 | 122篇 |
2021年 | 146篇 |
2020年 | 105篇 |
2019年 | 119篇 |
2018年 | 168篇 |
2017年 | 111篇 |
2016年 | 192篇 |
2015年 | 191篇 |
2014年 | 250篇 |
2013年 | 563篇 |
2012年 | 398篇 |
2011年 | 547篇 |
2010年 | 411篇 |
2009年 | 389篇 |
2008年 | 432篇 |
2007年 | 422篇 |
2006年 | 363篇 |
2005年 | 313篇 |
2004年 | 292篇 |
2003年 | 222篇 |
2002年 | 227篇 |
2001年 | 173篇 |
2000年 | 165篇 |
1999年 | 157篇 |
1998年 | 261篇 |
1997年 | 196篇 |
1996年 | 161篇 |
1995年 | 141篇 |
1994年 | 122篇 |
1993年 | 136篇 |
1992年 | 131篇 |
1991年 | 75篇 |
1990年 | 93篇 |
1989年 | 82篇 |
1988年 | 94篇 |
1987年 | 66篇 |
1986年 | 54篇 |
1985年 | 80篇 |
1984年 | 94篇 |
1983年 | 62篇 |
1982年 | 66篇 |
1981年 | 83篇 |
1980年 | 68篇 |
1979年 | 85篇 |
1978年 | 69篇 |
1977年 | 67篇 |
1976年 | 56篇 |
1975年 | 58篇 |
1973年 | 47篇 |
排序方式: 共有9388条查询结果,搜索用时 15 毫秒
31.
In the course of the past few years, sonography has become firmly established in clinical practice. The accuracy of the investigations does not only depend on the quality of the equipment used but also to a considerable degree on the standards of investigator training. To reduce the discrepancy between the number and quality of the investigations in the German Federal Republic, the "Kassen?rztliche Vereinigung" has released guidelines requiring the users of sonographic equipment to undergo theoretical and practical training. These guidelines are reviewed and commented. 相似文献
32.
JA Frank RE Hoffman JM Mann JD Crowe AR Hinman 《Canadian Metallurgical Quarterly》1981,245(3):264-266
From Dec 23, 1978, through Jan 31, 1979, an outbreak of five laboratory-confirmed cases and four clinical cases of measles occurred in a Vietnamese refugee population living in a single housing complex in Albuquerque, NM. The index cases were in two refugee siblings in whom measles was incubating on arrival in the United States. Despite spread through three subsequent generations of disease transmission within the Vietnamese population, there was no additional spread into the general Albuquerque population. Responsible factors included the age distribution of susceptible persons, the social isolation of the refugee population, and the physical structure of the housing complex. There is a need to identify the problem of imported measles in "ethnic islands" in need of vaccination. 相似文献
33.
The emergence of worldwide communications networks and powerful computer technologies has redefined the concept of distance learning and the delivery of engineering education content. This article discusses the Sloan Consortium's quest for quality, scale, and breadth in online learning, the impact on both continuing education of graduate engineers as well as degree‐seeking engineering students, and the future of engineering colleges and schools as worldwide providers of engineering education. 相似文献
34.
Dingfang Liu Zheng Teng John J. Sansalone Frank K. Cartledge 《Canadian Metallurgical Quarterly》2001,127(10):879-888
Most current control strategies for storm water treatment utilize fixed or filter-bed media with specific gravity (ρs) greater than 1.0. In contrast to Part I, Part II focuses on such higher density (ρs > 1.0) manganese-oxide-coated media that can be used in combined unit operations and processes for in-situ treatment of storm water. Methods were developed to coat manganese oxides onto sand and cementitious media for storm water treatment. With respect to manganese, coatings of ramsdellite produced a point of zero charge (PZC) of 5.2, while mixtures of birnessite and cryptomelane produced a PZC of 2.6 Manganese oxide increased the specific surface area (SSA) of sand and cementitious media. Manganese-oxide-coated sand (MOCS) produced a larger SSA (2.48-m2∕g), as compared with birnessite-coated media (BCM) (1.51 m2∕g), while the two have a similar surface charge (PZC = 6.4). Manganese-oxide-coated cementitious media (MOCM) produced a significantly larger SSA (19.49 m2∕g), as compared with coated sand, and SEM analyses indicated the surface contained manganese oxide and calcite of thickness 10–30 μm. Based on the results, coated cementitious media provided surface characteristics that can significantly enhance filtration and adsorption of heavy metal in storm water, in comparison to sand. 相似文献
35.
Monroe Scott M.; Roberts John E.; Kupfer David J.; Frank Ellen 《Canadian Metallurgical Quarterly》1996,105(3):313
Life stress was studied in relation to postrecovery attrition, symptom course, and recurrence of depression over 3 yrs. Participants were 67 individuals with recurrent depression who had responded to treatment. Life stress was assessed for the prior 12 wks at acute treatment entry (T1), initial recovery (T2), and after 17 wks of sustained recovery (T3). Severe life events at T1 predicted greater attrition, a more favorable postrecovery symptom course, and a lower likelihood of recurrence over 3 yrs. Life stress at T2 was not predictive of outcomes. Finally, undesirable life events at T3 tended to predict a worse symptom course and a higher likelihood of recurrence, particularly for individuals on medication. The findings are discussed in terms of (a) different processes influenced by life stress over time and (b) limitations of existing longitudinal research for studying the effects of life stress over prolonged intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
Feng Wang Frank Stappenbeck Liu-Ya Tang Ying E. Zhang Simon T. Hui Aldons J. Lusis Farhad Parhami 《International journal of molecular sciences》2022,23(10)
Inflammatory responses by the innate and adaptive immune systems protect against infections and are essential to health and survival. Many diseases including atherosclerosis, osteoarthritis, rheumatoid arthritis, psoriasis, and obesity involve persistent chronic inflammation. Currently available anti-inflammatory agents, including non-steroidal anti-inflammatory drugs, steroids, and biologics, are often unsafe for chronic use due to adverse effects. The development of effective non-toxic anti-inflammatory agents for chronic use remains an important research arena. We previously reported that oral administration of Oxy210, a semi-synthetic oxysterol, ameliorates non-alcoholic steatohepatitis (NASH) induced by a high-fat diet in APOE*3-Leiden.CETP humanized mouse model of NASH and inhibits expression of hepatic and circulating levels of inflammatory cytokines. Here, we show that Oxy210 also inhibits diet-induced white adipose tissue inflammation in APOE*3-Leiden.CETP mice, evidenced by the inhibition of adipose tissue expression of IL-6, MCP-1, and CD68 macrophage marker. Oxy210 and related analogs exhibit anti-inflammatory effects in macrophages treated with lipopolysaccharide in vitro, mediated through inhibition of toll-like receptor 4 (TLR4), TLR2, and AP-1 signaling, independent of cyclooxygenase enzymes or steroid receptors. The anti-inflammatory effects of Oxy210 are correlated with the inhibition of macrophage polarization. We propose that Oxy210 and its structural analogs may be attractive candidates for future therapeutic development for targeting inflammatory diseases. 相似文献
37.
Shafiq Murad Susanne Michen Alexander Becker Monika Füssel Gabriele Schackert Torsten Tonn Frank Momburg Achim Temme 《International journal of molecular sciences》2022,23(10)
In glioblastoma, non-classical human leucocyte antigen E (HLA-E) and HLA-G are frequently overexpressed. HLA-E loaded with peptides derived from HLA class I and from HLA-G contributes to inhibition of natural killer (NK) cells with expression of the inhibitory receptor CD94/NKG2A. We investigated whether NK cells expressing the activating CD94/NKG2C receptor counterpart were able to exert anti-glioma effects. NKG2C+ subsets were preferentially expanded by a feeder cell line engineered to express an artificial disulfide-stabilized trimeric HLA-E ligand (HLA-E*spG). NK cells expanded by a feeder cell line, which facilitates outgrowth of conventional NKG2A+, and fresh NK cells, were included for comparison. Expansion via the HLA-E*spG feeder cells selectively increased the fraction of NKG2C+ NK cells, which displayed a higher frequency of KIR2DL2/L3/S2 and CD16 when compared to expanded NKG2A+ NK cells. NKG2C+ NK cells exhibited increased cytotoxicity against K562 and KIR:HLA-matched and -mismatched primary glioblastoma multiforme (GBM) cells when compared to NKG2A+ NK cells and corresponding fresh NK cells. Cytotoxic responses of NKG2C+ NK cells were even more pronounced when utilizing target cells engineered with HLA-E*spG. These findings support the notion that NKG2C+ NK cells have potential therapeutic value for treating gliomas. 相似文献
38.
Florian Turbant Jehan Waeytens Camille Campidelli Marianne Bombled Denis Martinez Axelle Grlard Birgit Habenstein Vincent Raussens Marisela Velez Frank Wien Vronique Arluison 《International journal of molecular sciences》2022,23(15)
Hfq is a pleiotropic regulator that mediates several aspects of bacterial RNA metabolism. The protein notably regulates translation efficiency and RNA decay in Gram-negative bacteria, usually via its interaction with small regulatory RNAs. Previously, we showed that the Hfq C-terminal region forms an amyloid-like structure and that these fibrils interact with membranes. The immediate consequence of this interaction is a disruption of the membrane, but the effect on Hfq structure was unknown. To investigate details of the mechanism of interaction, the present work uses different in vitro biophysical approaches. We show that the Hfq C-terminal region influences membrane integrity and, conversely, that the membrane specifically affects the amyloid assembly. The reported effect of this bacterial master regulator on membrane integrity is discussed in light of the possible consequence on small regulatory RNA-based regulation. 相似文献
39.
The primary intent of this work is to present a method for sequentially associating three-dimensional surface measurements acquired by an autonomous exploration agent with models that describe those surfaces. Traditional multiple-viewpoint registration approaches are concerned only with finding the transformation that maps data points to a chosen global frame. Given a parts-based object representation, and assuming that the view correspondence can be found, the problem of associating the registered data with the correct part models still needs to be solved. While traditional approaches are content to group segmented data sets that geometrically overlap one another with the same part, there are cases where this causes ambiguous situations. This paper addresses the model-data association problem as it applies to three-dimensional dynamic object modeling. By tracking the state of part models across subsequent views, we wish to identify possible events that explain model-data association ambiguities and represent them in a Bayesian framework. The model-data association problem is therefore relaxed to allow multiple interpretations of the object's structure, each being assigned a probability. Rather than making a decision at every iteration about an ambiguous mapping, we look to the future for the information needed to disambiguate it. Experimental results are presented to illustrate the effectiveness of the approach. 相似文献
40.
Ulrich Münz Antonis Papachristodoulou Frank Allgöwer 《International journal of control》2013,86(5):953-969
An important task for multi-agent systems (MAS) is to reach a consensus, e.g. to align their velocity vectors. Recent results propose appropriate consensus protocols to achieve such tasks, but most of them do not consider the effect of communication constraints such as the presence of time-delays in the exchange of information between the agents. In this article, we provide conditions for a non-linear, locally passive MAS of arbitrary size to reach a consensus, when the agents communicate over a packet-switched network that is characterised by a given topology. Both the cases of constant and switching topologies are considered. The nature of the communication channel imposes constraints that are modelled using stochastic delays of arbitrary distribution. We first embed this model in another, distributed but deterministic delay model and provide conditions for the error introduced by this simplification. In our main result, we provide conditions for the locally passive MAS with distributed delays to reach a consensus. In the case of a fixed topology, the underlying directed graph has to contain a spanning tree. In the case of a switching topology, only the union graph of all graphs that persist over time is required to contain a spanning tree. These conditions are independent of the distribution and the size of the packet delays. To show attractivity of the consensus set, we use an invariance principle for systems described by functional differential equations based on an appropriate Lyapunov–Razumikhin function. This methodological approach is the main contribution of this work and can also be applied to other consensus problems with delays. We illustrate our results by numerical simulations showing synchronisation of non-linear Kuramoto oscillators over a digital network. 相似文献