全文获取类型
收费全文 | 3788篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 31篇 |
综合类 | 1篇 |
化学工业 | 319篇 |
金属工艺 | 41篇 |
机械仪表 | 34篇 |
建筑科学 | 70篇 |
矿业工程 | 3篇 |
能源动力 | 32篇 |
轻工业 | 257篇 |
水利工程 | 16篇 |
石油天然气 | 5篇 |
无线电 | 173篇 |
一般工业技术 | 290篇 |
冶金工业 | 2219篇 |
原子能技术 | 9篇 |
自动化技术 | 331篇 |
出版年
2024年 | 11篇 |
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 27篇 |
2016年 | 32篇 |
2015年 | 29篇 |
2014年 | 39篇 |
2013年 | 95篇 |
2012年 | 63篇 |
2011年 | 81篇 |
2010年 | 65篇 |
2009年 | 62篇 |
2008年 | 82篇 |
2007年 | 90篇 |
2006年 | 75篇 |
2005年 | 51篇 |
2004年 | 52篇 |
2003年 | 59篇 |
2002年 | 58篇 |
2001年 | 35篇 |
2000年 | 43篇 |
1999年 | 115篇 |
1998年 | 682篇 |
1997年 | 395篇 |
1996年 | 226篇 |
1995年 | 142篇 |
1994年 | 112篇 |
1993年 | 166篇 |
1992年 | 41篇 |
1991年 | 31篇 |
1990年 | 30篇 |
1989年 | 45篇 |
1988年 | 27篇 |
1987年 | 31篇 |
1986年 | 27篇 |
1985年 | 30篇 |
1984年 | 21篇 |
1983年 | 30篇 |
1982年 | 41篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 19篇 |
1978年 | 23篇 |
1977年 | 34篇 |
1976年 | 101篇 |
1975年 | 21篇 |
1963年 | 11篇 |
排序方式: 共有3831条查询结果,搜索用时 0 毫秒
121.
Lionel K. Arnold Orland R. Sweeney Ross F. Russell 《Journal of the American Oil Chemists' Society》1953,30(10):393-396
Summary Specific gravity-concentration data have been determined for wheat germ oil, milkweed seed oil, and cottonseed oil miscellas
where trichloroethylene is used as a solvent. Extraction rate data at two temperatures and pilot plant runs on wheat germs,
cottonseed, cottonseed meats, and milkweed seeds indicate increasing extraction time in the order given. 相似文献
122.
A new type of ion implantation technique is used to create a non-equilibrium Pt-Sn(IMP) near-surface alloy with ca. 8.6 at%
Sn. The surface composition was determined by low-energy ion-scattering (LEIS). The kinetics of the electrooxidation of CO
and 2% CO/H2 mixtures on Pt-Sn(IMP) is essentially identical to that of Pt3Sn(110). The fact that any non-equilibrium composition can be easily prepared by this implantation method opens an interesting
practical opportunity to create a new Pt-Sn alloy fuel cell catalyst having an otherwise unobtainable surface composition
of Sn. This method also appears to have general utility in alloy catalysis as a means of exploring compositions in thermodynamically
unfavorable regions of the bulk phase diagram.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
123.
124.
Amy A. Ross 《Microscopy research and technique》1987,5(1):81-90
A postembedding immunocytochemical technique is described that allows ultrastructural localization of glial fibrillary acidic protein and neuron-specific enolase on tissues originally processed only for routine light and electron microscopy. Use of the oxidizing agent sodium metaperiodate prior to incubation with the primary antiserum sufficiently removes osmium tetroxide (OsO4) from potential antigen—antibody combining sites to allow specific localization of these neural antigens by colloidal gold immunolabelling. Both human and monkey neural tissues, prepared for routine ultrastructural examination with aldehyde fixatives and OsO4 postfixation, show excellent ultrastructural morphology and antigen localization. In addition, formalin-fixed, paraffin-embedded pathological human brain tissues, obtained at autopsy up to 22 years previously, show good ultrastructural immunolocalization of glial fibrillary acidic protein when re-embedded for electron microscopy. Thus, ultrastructural immunolocalization of certain neural antigens is easily achieved in tissues originally processed for routine light and electron microscopy. This allows re-examination of archival tissues using current immunocy-tochemical advances, including that of selected pathological tissues previously prepared solely for light microscopy. 相似文献
125.
Jan-Bernd Hövener Eduard Y. Chekmenev Kent C. Harris William H. Perman Thao T. Tran Brian D. Ross Pratip Bhattacharya 《Magma (New York, N.Y.)》2009,22(2):123-134
Object Define MR quality assurance procedures for maximal PASADENA hyperpolarization of a biological 13C molecular imaging reagent.
Materials and methods An automated PASADENA polarizer and a parahydrogen generator were installed. 13C enriched hydroxyethyl acrylate, 1-13C, 2,3,3-d3 (HEA), was converted to hyperpolarized hydroxyethyl propionate, 1-13C, 2,3,3-d3 (HEP) and fumaric acid, 1-13C, 2,3-d2 (FUM) to hyperpolarized succinic acid, 1-13C, 2,3-d2 (SUC), by reaction with parahydrogen and norbornadiene rhodium catalyst. Incremental optimization of successive steps in
PASADENA was implemented. MR spectra and in vivo images of hyperpolarized 13C imaging agents were acquired at 1.5 and 4.7 T.
Results Application of quality assurance (QA) criteria resulted in incremental optimization of the individual steps in PASADENA implementation.
Optimal hyperpolarization of HEP of P = 20% was achieved by calibration of the NMR unit of the polarizer (B
0 field strength ± 0.002 mT). Mean hyperpolarization of SUC, P = [15.3 ± 1.9]% (N = 16) in D
2O, and P = [12.8 ± 3.1]% (N = 12) in H
2O, was achieved every 5–8 min (range 13–20%). An in vivo 13C succinate image of a rat was produced.
Conclusion PASADENA spin hyperpolarization of SUC to 15.3% in average was demonstrated (37,400 fold signal enhancement at 4.7 T). The
biological fate of 13C succinate, a normally occurring cellular intermediate, might be monitored with enhanced sensitivity. 相似文献
126.
Yingping Huang Ross McMurran Mark Amor-Segan Gunwant Dhadyalla R. Peter Jones Peter Bennett Alexandros Mouzakitis Jan Kieloch 《The International Journal of Advanced Manufacturing Technology》2010,51(1-4):233-246
A current premium vehicle is implemented with a variety of information, entertainment, and communication functions, which are generally referred as an infotainment system. During vehicle development, testing of the infotainment system at an overall level is conventionally carried out manually by an expert who can observe at a customer level. This approach has significant limitations with regard to test coverage and effectiveness due to the complexity of the system functions and human’s capability. Hence, it is highly demanded by car manufacturers for an automated infotainment testing system, which replicates a human expert encompassing relevant sensory modalities relating to control (i.e., touch) and observation (i.e., sight and sound) of the system under test. This paper describes the design, development, and evaluation of such a system that consists of simulation of vehicle network, vision-based inspection, automated navigation of features, random cranking waveform generation, sound detection, and test automation. The system developed is able to: stimulate a vehicle system across a wide variety of initialisation conditions, exercise each function, check for system responses, and record failure situations for post-testing analysis. 相似文献
127.
Adrian K. Clear Thomas Holland Simon Dobson Aaron Quigley Ross Shannon Paddy Nixon 《Pervasive and Mobile Computing》2010,6(5):575-589
Pervasive systems are large-scale systems consisting of many sensors capturing numerous types of information. As this data is highly voluminous and dimensional, data analysis tasks can be extremely cumbersome and time-consuming. Enabling computers to recognise real-world situations is an even more difficult problem, involving not only data analysis, but also consistency checking. Here we present Situvis, an interactive visualisation tool for representing sensor data and creating higher-level abstractions from the data. This paper builds on previous work, Clear et al. (2009) [8] through evolved tool functionality and an evaluation of Situvis. A user-trial consisting of 10 participants shows that Situvis can be used to complete the key tasks in the development process of situation specifications in over 50% less time than an improvised alternative toolset. 相似文献
128.
129.
Three-dimensional models, or pharmacophores, describing Euclidean constraints on the location on small molecules of functional
groups (like hydrophobic groups, hydrogen acceptors and donors, etc.), are often used in drug design to describe the medicinal
activity of potential drugs (or ‘ligands’). This medicinal activity is produced by interaction of the functional groups on
the ligand with a binding site on a target protein. In identifying structure-activity relations of this kind there are three
principal issues: (1) It is often difficult to “align” the ligands in order to identify common structural properties that
may be responsible for activity; (2) Ligands in solution can adopt different shapes (or `conformations’) arising from torsional
rotations about bonds. The 3-D molecular substructure is typically sought on one or more low-energy conformers; and (3) Pharmacophore
models must, ideally, predict medicinal activity on some quantitative scale. It has been shown that the logical representation
adopted by Inductive Logic Programming (ILP) naturally resolves many of the difficulties associated with the alignment and
multi-conformation issues. However, the predictions of models constructed by ILP have hitherto only been nominal, predicting
medicinal activity to be present or absent. In this paper, we investigate the construction of two kinds of quantitative pharmacophoric
models with ILP: (a) Models that predict the probability that a ligand is “active”; and (b) Models that predict the actual
medicinal activity of a ligand. Quantitative predictions are obtained by the utilising the following statistical procedures
as background knowledge: logistic regression and naive Bayes, for probability prediction; linear and kernel regression, for
activity prediction. The multi-conformation issue and, more generally, the relational representation used by ILP results in
some special difficulties in the use of any statistical procedure. We present the principal issues and some solutions. Specifically,
using data on the inhibition of the protease Thermolysin, we demonstrate that it is possible for an ILP program to construct
good quantitative structure-activity models. We also comment on the relationship of this work to other recent developments
in statistical relational learning.
Editors: Tamás Horváth and Akihiro Yamamoto 相似文献
130.
Andrew?J.?MayEmail author Tracy?Ross Steven?H.?Bayer Mikko?J.?Tarkiainen 《Personal and Ubiquitous Computing》2003,7(6):331-338
Recent years have seen an increased interest in navigational services for pedestrians. To ensure that these services are successful, it is necessary to understand the information requirements of pedestrians when navigating, and in particular, what information they need and how it is used. A requirements study was undertaken to identify these information requirements within an urban navigation context. Results show that landmarks were by far the most predominant navigation cue, that distance information and street names were infrequently used, and that information is used to enable navigation decisions, but also to enhance the pedestrians confidence and trust. The implications for the design of pedestrian navigation aids are highlighted. 相似文献