全文获取类型
收费全文 | 8679篇 |
免费 | 529篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 114篇 |
综合类 | 24篇 |
化学工业 | 2194篇 |
金属工艺 | 245篇 |
机械仪表 | 153篇 |
建筑科学 | 653篇 |
矿业工程 | 98篇 |
能源动力 | 286篇 |
轻工业 | 622篇 |
水利工程 | 50篇 |
石油天然气 | 21篇 |
武器工业 | 1篇 |
无线电 | 689篇 |
一般工业技术 | 1785篇 |
冶金工业 | 579篇 |
原子能技术 | 53篇 |
自动化技术 | 1648篇 |
出版年
2023年 | 107篇 |
2022年 | 164篇 |
2021年 | 335篇 |
2020年 | 201篇 |
2019年 | 214篇 |
2018年 | 240篇 |
2017年 | 268篇 |
2016年 | 354篇 |
2015年 | 303篇 |
2014年 | 387篇 |
2013年 | 609篇 |
2012年 | 543篇 |
2011年 | 734篇 |
2010年 | 524篇 |
2009年 | 492篇 |
2008年 | 511篇 |
2007年 | 450篇 |
2006年 | 401篇 |
2005年 | 312篇 |
2004年 | 267篇 |
2003年 | 199篇 |
2002年 | 174篇 |
2001年 | 109篇 |
2000年 | 104篇 |
1999年 | 121篇 |
1998年 | 149篇 |
1997年 | 111篇 |
1996年 | 99篇 |
1995年 | 68篇 |
1994年 | 68篇 |
1993年 | 48篇 |
1992年 | 55篇 |
1991年 | 31篇 |
1990年 | 41篇 |
1989年 | 29篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 31篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 23篇 |
1978年 | 13篇 |
1977年 | 16篇 |
1976年 | 28篇 |
1975年 | 15篇 |
1973年 | 11篇 |
1969年 | 11篇 |
排序方式: 共有9215条查询结果,搜索用时 15 毫秒
991.
Vincent Larivière Etienne Vignola-Gagné Christian Villeneuve Pascal Gélinas Yves Gingras 《Scientometrics》2011,87(3):483-498
Using the entire population of professors at universities in the province of Quebec (Canada), this article analyzes the relationship
between sex and research funding, publication rates, and scientific impact. Since age is an important factor in research and
the population pyramids of men and women are different, the role of age is also analyzed. The article shows that, after they
have passed the age of about 38, women receive, on average, less funding for research than men, are generally less productive
in terms of publications, and are at a slight disadvantage in terms of the scientific impact (measured by citations) of their
publications. Various explanations for these differences are suggested, such as the more restricted collaboration networks
of women, motherhood and the accompanying division of labour, women’s rank within the hierarchy of the scientific community
and access to resources as well as their choice of research topics and level of specialization. 相似文献
992.
Christopher J. Stapels Erik B. JohnsonXiao J. Chen Thomas H. PrettymanEric R. Benton James F. Christian 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):342-346
The compact, robust nature of the CMOS solid-state photomultiplier (SSPM) allows the creation of small, low-power scintillation-based radiation measurement devices. Monitoring space radiation including solar protons and secondary neutrons generated from high-energy protons impinging on spacecraft is required to determine the dose to astronauts. Small size and highly integrated design are desired to minimize consumption of payload resources.RMD is developing prototype radiation measurement and personal dosimeter devices using emerging scintillation materials coupled to CMOS SSPM’s for multiple applications. Spectroscopic measurements of high-energy protons and gamma-rays using tissue-equivalent, inorganic scintillators coupled to SSPM devices demonstrate the ability of an SSPM device to monitor the dose from proton and heavy ion particles, providing real time feedback to astronauts. Measurement of the dose from secondary neutrons introduces additional challenges due to the need to discriminate neutrons from other particle types and to accurately determine their energy deposition. We present strategies for measuring neutron signatures and assessing neutron dose including simulations of relevant environments and detector materials. 相似文献
993.
Mickel McClish Purushottam DokhaleJames Christian Christopher StapelsErik Johnson Frank AugustineKanai S. Shah 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):264-267
We have designed a 5×5 mm2 position sensitive solid-state photomultiplier (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process that provides imaging capability on the micro-pixel level. The PS-SSPM has 11,664 micro-pixels total, with each having an active area and micro-pixel pitch of 30×30 μm2 and 44.3 μm, respectively. The PS-SSPM was then examined for its performance characteristics such as its energy and spatial resolution, and LYSO scintillator array imaging capabilities. When coupled to 5×5×3 mm3 LYSO, the energy resolution at 511 keV (22Na) was measured as a function of bias, and corrected for the PS-SSPM non-linear output. The resolution is 14% (FWHM) at 511 keV with 30 V bias. The LYSO coincidence timing resolution was 9.4 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (∼30 μm beam spot diameter) pulsed 635 nm diode laser. Scintillator array imaging studies were conducted at 511 keV using a 6×6 LYSO array, having 500 μm pixels (530 μm pitch) and 5 mm tall. 相似文献
994.
Christian Thaulow Stella V. Schieffer Inga R. Vatne Dipanjan Sen Erling Østby 《Computational Materials Science》2011,50(9):2621-2627
We analyze the fracture of single crystal silicon simulated by atomistic modeling with ReaxFF first principles based reactive force field. The simulations are performed at three temperatures: 500 K, 800 K and 1200 K, capturing both brittle and ductile behavior for the selected crystallographic orientation with (1 0 0) as the fracture plane. Three failure mechanisms are observed: bond breaking, amorphization and emission of dislocations. We demonstrate that the Crack Tip Opening Displacement (CTOD) gives a realistic estimate of the fracture toughness of brittle fracture, linking continuum mechanics fracture theory with the direct crack tip atomistic approach. We discuss the physics based mechanisms of failure in silicon in view of the CTOD measurements. 相似文献
995.
996.
997.
998.
Melanie?Wieschebrock Marion?Seitter Christian?HertelEmail author 《European Food Research and Technology》2011,233(4):617-624
A real-time PCR system with 16S rRNA gene-targeted group-specific primers was developed to quantitatively detect lactic acid
bacteria (LAB) of the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella in different types of commercially available dried sourdoughs. Despite a high degree of degradation in the DNA isolated from
the doughs, the 341-bp 16S rRNA gene fragment of the sourdough LAB biota could specifically be amplified. For dried sourdoughs,
the resulting calculated LAB cell counts were determined to be up to 3.7 × 107 cells/g fresh dough, whereas in non-fermented dough acidifiers, used as a control, the calculated LAB cell counts did not
exceed 3.6 × 104 cells/g fresh dough. Moreover, the effect of low pH and/or high lactic acid concentrations prevailing in the doughs on the
detectability of LAB cells in spray- and roller-dried sourdoughs by PCR was investigated. Drying of non-acidified sourdoughs
still permitted to detect the LAB cells by PCR, whereas drying of acidified doughs reduced the detectable cell counts by approximately
5 (spray dried) and 2 (roller dried) orders of magnitudes. Incubation of acidified doughs for 24 h did not affect the detectability
of LAB cells in spray-dried doughs but further reduced the detectable cell counts in roller-dried doughs by additional 2 orders
of magnitude. 相似文献
999.
McKinney MA Letcher RJ Aars J Born EW Branigan M Dietz R Evans TJ Gabrielsen GW Muir DC Peacock E Sonne C 《Environmental science & technology》2011,45(3):896-902
The relative contribution of regional contamination versus dietary differences to geographic variation in polar bear (Ursus maritimus) contaminant levels is unknown. Dietary variation between Alaska, Canada, East Greenland, and Svalbard subpopulations was assessed by muscle nitrogen and carbon stable isotope (δ(15)N, δ(13)C) and adipose fatty acid (FA) signatures relative to their main prey (ringed seals). Western and southern Hudson Bay signatures were characterized by depleted δ(15)N and δ(13)C, lower proportions of C(20) and C(22) monounsaturated FAs and higher proportions of C(18) and longer chain polyunsaturated FAs. East Greenland and Svalbard signatures were reversed relative to Hudson Bay. Alaskan and Canadian Arctic signatures were intermediate. Between-subpopulation dietary differences predominated over interannual, seasonal, sex, or age variation. Among various brominated and chlorinated contaminants, diet signatures significantly explained variation in adipose levels of polybrominated diphenyl ether (PBDE) flame retardants (14-15%) and legacy PCBs (18-21%). However, dietary influence was contaminant class-specific, since only low or nonsignificant proportions of variation in organochlorine pesticide (e.g., chlordane) levels were explained by diet. Hudson Bay diet signatures were associated with lower PCB and PBDE levels, whereas East Greenland and Svalbard signatures were associated with higher levels. Understanding diet/food web factors is important to accurately interpret contaminant trends, particularly in a changing Arctic. 相似文献
1000.
The aim of this study was to apply an edible coating containing prebiotics such as oligofructose and inulin to fresh-cut apple wedges. An assessment of the quality, sensory, polyphenol, and volatile attributes of coated and uncoated fresh-cut apple wedges was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14-d storage period and an intake of 100 g of apple supplies 1 to 3 g of prebiotics. Browning index, firmness, acidity remained stable throughout the 14 d compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory and visual assessment indicated acceptable quality of apple wedges coated with prebiotics. HPLC analysis showed that levels of polyphenolic compounds were more stable in coated apple wedges (without prebiotic inclusions) than in uncoated control apples. No difference was found between O(2) and CO(2) headspace concentration of coated and uncoated samples. Significant differences (P < 0.001) were found for headspace volatile production between the samples. Most coated samples showed lower volatile production in the headspace than uncoated samples. 相似文献