全文获取类型
收费全文 | 4068篇 |
免费 | 13篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 10篇 |
综合类 | 6篇 |
化学工业 | 78篇 |
金属工艺 | 16篇 |
机械仪表 | 9篇 |
建筑科学 | 50篇 |
能源动力 | 13篇 |
轻工业 | 26篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 58篇 |
一般工业技术 | 112篇 |
冶金工业 | 3642篇 |
原子能技术 | 3篇 |
自动化技术 | 56篇 |
出版年
2023年 | 4篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 23篇 |
2012年 | 10篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 12篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 20篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 110篇 |
1998年 | 1104篇 |
1997年 | 600篇 |
1996年 | 440篇 |
1995年 | 237篇 |
1994年 | 220篇 |
1993年 | 230篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 59篇 |
1989年 | 56篇 |
1988年 | 61篇 |
1987年 | 54篇 |
1986年 | 54篇 |
1985年 | 37篇 |
1984年 | 12篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 24篇 |
1980年 | 34篇 |
1979年 | 4篇 |
1978年 | 14篇 |
1977年 | 88篇 |
1976年 | 193篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1970年 | 5篇 |
排序方式: 共有4087条查询结果,搜索用时 15 毫秒
131.
Gill Lawson 《Landscape Research》2013,38(2):217-223
An understanding of the complex problems of land-use competition requires an appreciation of natural processes, cultural values, economic imperatives and political agendas. This integrated understanding is an important component of the study programme for higher education students seeking a professional qualification in landscape architecture. A repertoire of game templates is introduced as an initial step in formulating a conceptual framework for the curriculum/games designer to explore the potential of play in ecological landscape planning. The concepts of social action space, permissible action space and motivational action space are used to investigate the qualities of each template for further game design development. The abstraction of these concepts may assist the designer to move beyond the usability of games into viewing their value as a learning method. 相似文献
132.
正Ground control is the science of studying and controlling the behavior of rock strata in response to mining operations.Ground-control-related research has seen significant advancements over the last 40 years, and these accomplishments are well documented in the proceedings of the annual International Conference on Ground Control in Mining (ICGCM)[1]. 相似文献
133.
Rapid fabrication of poly(ε‐caprolactone) nanofibers using needleless alternating current electrospinning
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Caitlin Lawson Andrei Stanishevsky Manikandan Sivan Pavel Pokorny David Lukáš 《应用聚合物科学杂志》2016,133(13)
Poly(ε‐caprolactone) ( PCL) biopolymer nanofibers and micro‐fibers have been fabricated for the first time at the rates up to 14.0 g per hour using a needleless and collectorless alternating current electrospinning technique. By combining the ac‐voltage, “green” low toxicity glacial acetic acid (AA) as the solvent and sodium acetate (NaAc) as an additive, beadless PCL fibers with diameters tunable from 150 nm to 2000 nm, varying surface morphology and degree of self‐bundling are obtained. In this new approach, the addition of NaAc plays a crucial role in improving the spinnability of PCL solution and fiber morphology. NaAc reveals the concentration‐dependent effect on charge transfer and rheological properties of the PCL/AA precursor, which results in broader ranges of spinnable PCL concentrations and ac‐voltages suitable for rapid manufacturing of PCL‐based fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43232. 相似文献
134.
Multimerization behaviour of single chain Fv variants for the tumour-binding antibody B72.3 总被引:2,自引:0,他引:2
Desplancq Dominique; King David J.; Lawson Alastair D.G.; Mountain Andrew 《Protein engineering, design & selection : PEDS》1994,7(8):1027-1033
A systematic study has been performed on the relationship betweenlinker length, relative orientation of variable domains, multimerizationbehaviour and antigen binding activity for single chain Fvs(scFvs) of the tumour-binding antibody B72.3. Thirteen scFvvariants with linkers comprising up to six repeats of the motifGly-Gly-Gry-Gly-Ser were studied. All these scFvs showed a tendencyto form dimers or higher molecular weight species, and thistendency decreased with increasing linker length. The dimersand higher molecular weight forms may arise from head to tailintermolecular association of VH and VL domains. For each linkerlength, scFvs with the organization VL-linker-VH showed greaterbinding activity than those with the organization VH-linker-VL.In fact, for the latter organization only the variant with a30 amino acid linker showed good binding activity, suggestingthat (0 for B72.3 the C-tenninus of VH or the N-tenninus ofVL makes a structural contribution to antigen binding, and (ii)shorter linkers interfere with this contribution. Antigen bindingstudies on scFvs should be interpreted with caution becauseof their tendency to multlmerize. Such multimerization can beminimized by using linkers longer than those in common use 相似文献
135.
The depolymerization of coals using phenol and p-toluenesulphonic acid, was studied.In this reaction the acid ‘catalyst’ is destroyed, its rate of destruction being different for different coals. A kinetic study of the depolymerization of Bruceton coal under conditions of gradually declining acid concentration has been carried out. Parameters which were monitored include the weight increase of the products, the solubility of the products in benzene-ethanol, the extractability of the products into pyridine, the amount of colloidal material present in the pyridine-extractables, and the molecular weight distribution of the pyridine-soluble products. Under the conditions used, the reaction produces primarily polymeric products from coal. The molecular weight distribution of the pyridine-soluble material seems to undergo no major changes with reaction time. 相似文献
136.
Discovery of a Short‐Chain Dehydrogenase from Catharanthus roseus that Produces a New Monoterpene Indole Alkaloid
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Anna K. Stavrinides Dr. Evangelos C. Tatsis Dr. Thu‐Thuy Dang Dr. Lorenzo Caputi Dr. Clare E. M. Stevenson Dr. David M. Lawson Dr. Bernd Schneider Prof. Sarah E. O'Connor 《Chembiochem : a European journal of chemical biology》2018,19(9):940-948
Plant monoterpene indole alkaloids, a large class of natural products, derive from the biosynthetic intermediate strictosidine aglycone. Strictosidine aglycone, which can exist as a variety of isomers, can be reduced to form numerous different structures. We have discovered a short‐chain alcohol dehydrogenase (SDR) from plant producers of monoterpene indole alkaloids (Catharanthus roseus and Rauvolfia serpentina) that reduce strictosidine aglycone and produce an alkaloid that does not correspond to any previously reported compound. Here we report the structural characterization of this product, which we have named vitrosamine, as well as the crystal structure of the SDR. This discovery highlights the structural versatility of the strictosidine aglycone biosynthetic intermediate and expands the range of enzymatic reactions that SDRs can catalyse. This discovery further highlights how a sequence‐based gene mining discovery approach in plants can reveal cryptic chemistry that would not be uncovered by classical natural product chemistry approaches. 相似文献
137.
刘淳 《腐蚀科学与防护技术》1994,6(2):115-122
局部腐蚀,包括点腐蚀、应力腐蚀开裂和腐蚀疲劳是导致电厂发电装置损伤的重要原因,它们诱发50%以上的意外停机事故。迄今,腐蚀破坏的预测一直沿用经验和统计的方法,但是,由于已证实该方法的适用性和其结果的准确性欠佳,故不宜作为例行检修规程的基础。本文提出了预测局部腐蚀损伤的决定论方法,并使用这个方法说明点腐蚀如何引发低压蒸汽轮机涡轮盘Wilson线下游部位的应力腐蚀开裂(SCC),我们的计算表明SCC的萌发与扩展对蒸汽小氧含量、冷凝液膜的环境和涡轮盘所承受的应力这三个因素敏感。 相似文献
138.
A range of point process models which are commonly used in spatial epidemiology applications for the increased incidence of disease are compared. The models considered vary from approximate methods to an exact method. The approximate methods include the Poisson process model and methods that are based on discretization of the study window. The exact method includes a marked point process model, i.e., the conditional logistic model. Apart from analyzing a real dataset (Lancashire larynx cancer data), a small simulation study is also carried out to examine the ability of these methods to recover known parameter values. The main results are as follows. In estimating the distance effect of larynx cancer incidences from the incinerator, the conditional logistic model and the binomial model for the discretized window perform relatively well. In explaining the spatial heterogeneity, the Poisson model (or the log Gaussian Cox process model) for the discretized window produces the best estimate. 相似文献
139.
Energy cultures: A framework for understanding energy behaviours 总被引:1,自引:0,他引:1
Janet Stephenson Barry Barton Gerry Carrington Daniel Gnoth Rob Lawson Paul Thorsnes 《Energy Policy》2010
Achieving a ‘step-change’ in energy efficiency behaviours will require enhanced knowledge of behavioural drivers, and translation of this knowledge into successful intervention programmes. The ‘Energy Cultures’ conceptual framework aims to assist in understanding the factors that influence energy consumption behaviour, and to help identify opportunities for behaviour change. Building on a history of attempts to offer multi-disciplinary integrating models of energy behaviour, we take a culture-based approach to behaviour, while drawing also from lifestyles and systems thinking. The framework provides a structure for addressing the problem of multiple interpretations of ‘behaviour’ by suggesting that it is influenced by the interactions between cognitive norms, energy practices and material culture. 相似文献
140.
Murray S. Daw John W. Lawson Charles W. Bauschlicher 《Computational Materials Science》2011,50(10):2828-2835
We report on the first interatomic potentials for Zirconium Diboride and Hafnium Diboride. The potentials are of the Tersoff form, and are obtained by fitting to a first-principles database of basic properties of elemental Zr, Hf, B, and the compounds ZrB2 and HfB2. Two variants of the Zr–B potentials have been obtained, and one for Hf–B. The potentials have been tested against a variety of properties of the compound, with the conclusion that they are stable and provide a reasonable representation of the desired properties of the two diborides. 相似文献