全文获取类型
收费全文 | 12402篇 |
免费 | 510篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 125篇 |
综合类 | 4篇 |
化学工业 | 2362篇 |
金属工艺 | 254篇 |
机械仪表 | 257篇 |
建筑科学 | 710篇 |
矿业工程 | 25篇 |
能源动力 | 382篇 |
轻工业 | 1107篇 |
水利工程 | 126篇 |
石油天然气 | 35篇 |
无线电 | 931篇 |
一般工业技术 | 2367篇 |
冶金工业 | 2096篇 |
原子能技术 | 72篇 |
自动化技术 | 2085篇 |
出版年
2023年 | 79篇 |
2022年 | 147篇 |
2021年 | 231篇 |
2020年 | 191篇 |
2019年 | 235篇 |
2018年 | 260篇 |
2017年 | 255篇 |
2016年 | 280篇 |
2015年 | 251篇 |
2014年 | 369篇 |
2013年 | 796篇 |
2012年 | 602篇 |
2011年 | 871篇 |
2010年 | 575篇 |
2009年 | 545篇 |
2008年 | 667篇 |
2007年 | 586篇 |
2006年 | 499篇 |
2005年 | 434篇 |
2004年 | 394篇 |
2003年 | 365篇 |
2002年 | 333篇 |
2001年 | 199篇 |
2000年 | 207篇 |
1999年 | 188篇 |
1998年 | 367篇 |
1997年 | 283篇 |
1996年 | 238篇 |
1995年 | 191篇 |
1994年 | 164篇 |
1993年 | 167篇 |
1992年 | 119篇 |
1991年 | 104篇 |
1990年 | 117篇 |
1989年 | 85篇 |
1988年 | 72篇 |
1987年 | 93篇 |
1986年 | 87篇 |
1985年 | 104篇 |
1984年 | 98篇 |
1983年 | 110篇 |
1982年 | 94篇 |
1981年 | 90篇 |
1980年 | 106篇 |
1979年 | 95篇 |
1978年 | 78篇 |
1977年 | 84篇 |
1976年 | 85篇 |
1975年 | 61篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Laura K. Finnegan Naomi Chadderton Paul F. Kenna Arpad Palfi Michael Carty Andrew G. Bowie Sophia Millington-Ward G. Jane Farrar 《International journal of molecular sciences》2022,23(3)
The challenge of developing gene therapies for genetic forms of blindness is heightened by the heterogeneity of these conditions. However, mechanistic commonalities indicate key pathways that may be targeted in a gene-independent approach. Mitochondrial dysfunction and axon degeneration are common features of many neurodegenerative conditions including retinal degenerations. Here we explore the neuroprotective effect afforded by the absence of sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1), a prodegenerative NADase, in a rotenone-induced mouse model of retinal ganglion cell loss and visual dysfunction. Sarm1 knockout mice retain visual function after rotenone insult, displaying preservation of photopic negative response following rotenone treatment in addition to significantly higher optokinetic response measurements than wild type mice following rotenone. Protection of spatial vision is sustained over time in both sexes and is accompanied by increased RGC survival and additionally preservation of axonal density in optic nerves of Sarm1−/− mice insulted with rotenone. Primary fibroblasts extracted from Sarm1−/− mice demonstrate an increased oxygen consumption rate relative to those from wild type mice, with significantly higher basal, maximal and spare respiratory capacity. Collectively, our data indicate that Sarm1 ablation increases mitochondrial bioenergetics and confers histological and functional protection in vivo in the mouse retina against mitochondrial dysfunction, a hallmark of many neurodegenerative conditions including a variety of ocular disorders. 相似文献
992.
Kendall Richard Carver Jeffrey C. Fisher David Henderson Dale Mark Andrew Post Douglass Rhoades Jr. Clifford E. Squires Susan 《Software, IEEE》2008,25(4):59-65
Computational science is increasingly supporting advances in scientific and engineering knowledge. The unique constraints of these types of projects result in a development process that differs from the process more traditional information technology projects use. This article reports the results of the sixth case study conducted under the support of the Darpa High Productivity Computing Systems Program. The case study aimed to investigate the technical challenges of code development in this environment, understand the use of development tools, and document the findings as concrete lessons learned for other developers' benefit. The project studied here is a major component of a weather forecasting system of systems. It includes complex behavior and interaction of several individual physical systems (such as the atmosphere and the ocean). This article describes the development of the code and presents important lessons learned. 相似文献
993.
在不断增长的液晶显示(LCD)优势中,电润湿的新技术正试图在较好的光线利用和简化制造方面,占据一席之地。 相似文献
994.
Hutchinson JP Zakaria P Bowie AR Macka M Avdalovic N Haddad PR 《Analytical chemistry》2005,77(2):407-416
A sulfonated methacrylate monolithic polymer has been synthesized inside fused-silica capillaries of diameters 50-533-microm i.d. and coated with 65-nm-diameter fully functionalized quaternary ammonium latex particles (AS18, Dionex Corp.) to form an anion-exchange stationary phase. This stationary phase was used for ion-exchange capillary electrochromatography of inorganic anions in a 75-microm-i.d. capillary with Tris/perchlorate electrolyte and direct UV detection at 195 nm. Seven inorganic anions (bromide, nitrate, iodide, iodate, bromate, thiocyanate, chromate) could be separated over a period of 90 s, and the elution order indicated that both ion exchange and electrophoresis contributed to the separation mechanism. Separation efficiencies of up to 1.66 x 10(5) plates m(-1) were achieved, and the monoliths were stable under pressures of up to 62 MPa. Another latex-coated monolith in a 250-microm-i.d. capillary was used for in-line preconcentration by coupling it to a separation capillary in which the EOF had been reversed using a coating of either a cationic polymer or cationic latex particles. Several capillary volumes of sample were loaded onto the preconcentration monolith, and the analytes (inorganic anions) were then eluted from the monolith with a transient isotachophoretic gradient before being separated by electrophoresis in the separation capillary. Linear calibration curves were obtained for aqueous mixtures of bromide, nitrite, nitrate, and iodide. Recoveries of all analytes except iodide were reduced significantly when the sample matrix contained high levels of chloride. The preconcentration method was applied to the determination of iodide in open ocean water and provided a limit of detection of 75 pM (9.5 ng/L) calculated at a signal-to-noise ratio of 3. The relative standard deviation for migration time and peak area for iodide were 1.1 and 2.7%, respectively (n = 6). Iodide was eluted as an efficient peak, yielding a separation efficiency of 5.13 x 10(7) plates m(-1). This focusing was reproducible for repeated analyses of seawater. 相似文献
995.
Vanessa Sanchez Kausalya Mahadevan Gabrielle Ohlson Moritz A. Graule Michelle C. Yuen Clark B. Teeple James C. Weaver James McCann Katia Bertoldi Robert J. Wood 《Advanced functional materials》2023,33(26):2212541
Soft robots adapt passively to complex environments due to their inherent compliance, allowing them to interact safely with fragile or irregular objects and traverse uneven terrain. The vast tunability and ubiquity of textiles has enabled new soft robotic capabilities, especially in the field of wearable robots, but existing textile processing techniques (e.g., cut-and-sew, thermal bonding) are limited in terms of rapid, additive, accessible, and waste-free manufacturing. While 3D knitting has the potential to address these limitations, an incomplete understanding of the impact of structure and material on knit-scale mechanical properties and macro-scale device performance has precluded the widespread adoption of knitted robots. In this work, the roles of knit structure and yarn material properties on textile mechanics spanning three regimes–unfolding, geometric rearrangement, and yarn stretching–are elucidated and shown to be tailorable across unique knit architectures and yarn materials. Based on this understanding, 3D knit soft actuators for extension, contraction, and bending are constructed. Combining these actuation primitives enables the monolithic fabrication of entire soft grippers and robots in a single-step additive manufacturing procedure suitable for a variety of applications. This approach represents a first step in seamlessly “printing” conformal, low-cost, customizable textile-based soft robots on-demand. 相似文献
996.
Rula A. Deeb Jonathan O. Sharp Andrew Stocking Shane McDonald Kimberlee A. West Maryline Laugier Pedro J. J. Alvarez Michael C. Kavanaugh Lisa Alvarez-Cohen 《Canadian Metallurgical Quarterly》2002,128(9):868-875
Recent legislation in several states has called for the removal of methyl tert-butyl ether (MTBE) from gasoline. In order to comply with Federal Clean Air Act requirements for carbon monoxide and ozone attainment, ethanol is being considered as a replacement for MTBE. The objective of this study is to evaluate the potential impact of ethanol on benzene plume lengths in subsurface environments following accidental spills of ethanol-blended gasoline. Two types of studies were conducted here. First, laboratory studies were performed using a pure culture indigenous to a gasoline-contaminated aquifer to evaluate the effect of ethanol on the rate of benzene biodegradation under aerobic conditions. Results from microbial studies showed that the biodegradation of 25 mg/L benzene was severely inhibited in the presence of 25 mg/L ethanol. While the enzymes responsible for benzene biodegradation by the culture were inducible, ethanol degradation appeared to be constitutive. Second, a two-dimensional model was developed to quantify the impact of ethanol on benzene plume lengths using weighted-average aerobic and anaerobic biodegradation rates for benzene in the presence and absence of ethanol. Model simulations indicated that benzene plume lengths are likely to increase by 16–34% in the presence of ethanol. 相似文献
997.
安利路位于阿德莱德大城市地区南部近郊,它是澳大利亚大城市中相当常见的“中心大街”的一个缩影。本文通过南澳大利亚大学规划专业学生在社区调查基础上进行的项目研究,反映了安利路作为中心大街商业区的主要特征、对安利路形成竞争的因素、对安利路产生影响的问题,并探讨了从社区愿望出发对安利路进行改善的方法和管理战略。 相似文献
998.
Thomas Hilker Forrest G. Hall Nicholas C. Coops Yujie Wang Zoran Nesic T. Andrew Black Natascha Kljun Laura Chasmer 《Remote sensing of environment》2010,114(12):2863-3435
Eddy covariance (EC) measurements have greatly advanced our knowledge of carbon exchange in terrestrial ecosystems. However, appropriate techniques are required to upscale these spatially discrete findings globally. Satellite remote sensing provides unique opportunities in this respect, but remote sensing of the photosynthetic light-use efficiency (ε), one of the key components of Gross Primary Production, is challenging. Some progress has been made in recent years using the photochemical reflectance index, a narrow waveband index centered at 531 and 570 nm. The high sensitivity of this index to various extraneous effects such as canopy structure, and the view observer geometry has so far prevented its use at landscape and global scales. One critical aspect of upscaling PRI is the development of generic algorithms to account for structural differences in vegetation. Building on previous work, this study compares the differences in the PRI: ? relationship between a coastal Douglas-fir forest located on Vancouver Island, British Columbia, and a mature Aspen stand located in central Saskatchewan, Canada. Using continuous, tower-based observations acquired from an automated multi-angular spectro-radiometer (AMSPEC II) installed at each site, we demonstrate that PRI can be used to measure ? throughout the vegetation season at the DF-49 stand (r2 = 0.91, p < 0.00) as well as the deciduous site (r2 = 0.88, p < 0.00). It is further shown that this PRI signal can be also observed from space at both sites using daily observations from the Moderate Resolution Imaging Spectro-radiometer (MODIS) and a multi-angular implementation of atmospheric correction (MAIAC) (r2 = 0.54 DF-49; r2 = 0.63 SOA; p < 0.00). By implementing a simple hillshade model derived from airborne light detection and ranging (LiDAR) to approximate canopy shadow fractions (αs), it is further demonstrated that the differences observed in the relationship between PRI and ε at DF-49 and SOA can be attributed largely to differences in αs. The findings of this study suggest that algorithms used to separate physiological from extraneous effects in PRI reflectance may be more broadly applicable and portable across these two climatically and structurally different biome types, when the differences in canopy structure are known. 相似文献
999.
Adsorption of lutein from crude soybean oil miscella on dispersed silicic acid resulted in three different Freundlich type
isotherms, depending on the amount of adsorbent used. Normally, changing the amount of adsorbent gives a new point on the
same isotherm. Further investigation of the lutein adsorption revealed that addition of 1% isopropanol to the hexane solvent
and deactivation of the silica acid with water decreased lutein adsorption. Purification of the lutein resulted in increased
adsorption, indicating that triglyceride was competing for adsorption sites. The triglyceride competition was confirmed by
calculating an adsorption isotherm for triglyceride from crude soybean oil miscella. Use of silicic acid as a column rather
than dispersed yielded multiple isotherms for lutein adsorption based on the amount of adsorbent used. Also, lutein adsorption
on columns was concentrated at the entrance to the column. Experiments showed that lutein adsorption was not due to partitioning
between bound triglyceride and hexane solvent. 相似文献
1000.
Farel Bradbury Theresa Anderson Bruce Wood M. Pugh‐Thomas B. J. Thomas Ronald Hughes 《The International journal of environmental studies》2013,70(3-4):245-254
RESOURCE TRENDS AND POPULATION POLICY: A TIME FOR REASSESSMENT, by Lester R. Brown. Worldwatch Institute, Washington, D.C., May 1979; Worldwatch Paper 29. (Paperback $2.00) THE NEXT SEVENTY YEARS: POPULATION, FOOD AND RESOURCES, by B. Gil‐land. Abacus Press, London, 1979. 133 pp. (£9.50) POPULATION POLICY ANALYSIS, edited by M. E. Kraft and M. Schneider. D. C. Heath, London, 1979. (£0.00) ENVIRONMENTAL IMPACT ASSESSMENT, by Brian B. Clark, Ronald Bisset and Peter Wath‐ern. Manssell, London and Bowker, New York, 1980. 516 pp. (£0.00) ADVANCES IN ECOLOGICAL RESEARCH, Vol. 11, edited by Amyan MacFadyen. Academic Press, London, 1980. 428 pp. (£25.00) MICROBIAL GROWTH AND SURVIVAL IN EXTREMES OF ENVIRONMENT, edited by G. W. Gould and Janet E. Cory. Academic Press, London, 1980. 244 pp. (£16.00) UNDER NEW MANAGEMENT: Port Growth and Emerging Coastal Management Programs, by Marc Hershman, Robert Goodwin, Andrew Ruot‐sala, Maureen McCrea and Yehuda Hayuth. A Washington Sea Grant Publication, 1978. 212 pp. ($12.50) HANDBOOK OF INDUSTRIAL ENERGY ANALYSIS, by J. Boustead and G. F. Hancock. Ellis‐Harwood, Chichester, U.K., 1979. (£25.00) TREE GROWTH AND ENVIRONMENTAL STRESSES, by T. T. Kozlowski. University of Washington Press, Seattle and London, 1979. vii + 192 pp. (£12.50) ALL GOOD THINGS AROUND US, by Pamela Michael. Illustrated by Christabel King. Ernest Benn Ltd., London, 1980. 240 pp. (£12.95) HUMAN GEOGRAPHY (2nd Edition), by A. V. Perpillou. Longman Group, London, U.K., 1977. xviii + 570 pp. 37 pls., 27 maps and diagrams, Index. (Paperback £5.50) INDUSTRIAL AND HAZARDOUS WASTES IMPOUNDMENT, by N. P. Cheremisinoff, P. N. Cheremisinoff, F. Ellerbeck and A. J. Perna. Ann Arbor Science, Michigan, 1979. ix + 475 pp. Index. (£16.25) PHOSPHORUS IN THE ENVIRONMENT: ITS CHEMISTRY AND BIOCHEMISTRY. (Ciba Foundation No. 57, New Series), by Ruth Porter and David W. Fitzsimons. Elsevier, 1978. (£18.15) TOXIC AND HAZARDOUS WASTE DISPOSAL. Vol. II, edited by R. B. Pojasek (Options for Sterilization Solidifications). Ann Arbor Science, Michigan, U.S.A., 1979, 259 pp. (£19.80) SON OF THE WILDERNESS (The Life of John Muir), by Linnie Marsh Wolfe. The University of Wisconsin Press, Madison, 1978. 364 pp. (Paperback £4.90) NATURE'S PRICE, by W. van Dieren and M. G. W. Hummelinck. Marion Boyars, London, Boston, 1979. (Paperback £3.50) PERMACULTURE ONE, by Bill (B. C.) Molli‐son and David Holmgren. Corgi Books, Trans‐world Publishers Ltd., Melbourne, Australia. 128 pp. (A $4.95) ENVIRONMENTAL AERODYNAMICS, by R. S. Scorer. Ellis Horwood, Chichester, U.K., 1978. 488 pp. (Hardback £20.00; paperback £7.50) 相似文献