全文获取类型
收费全文 | 3655篇 |
免费 | 82篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 27篇 |
综合类 | 5篇 |
化学工业 | 660篇 |
金属工艺 | 56篇 |
机械仪表 | 80篇 |
建筑科学 | 174篇 |
矿业工程 | 10篇 |
能源动力 | 118篇 |
轻工业 | 383篇 |
水利工程 | 31篇 |
石油天然气 | 17篇 |
武器工业 | 1篇 |
无线电 | 331篇 |
一般工业技术 | 509篇 |
冶金工业 | 916篇 |
原子能技术 | 35篇 |
自动化技术 | 386篇 |
出版年
2023年 | 11篇 |
2022年 | 18篇 |
2021年 | 20篇 |
2020年 | 27篇 |
2019年 | 24篇 |
2018年 | 40篇 |
2017年 | 43篇 |
2016年 | 50篇 |
2015年 | 38篇 |
2014年 | 79篇 |
2013年 | 214篇 |
2012年 | 131篇 |
2011年 | 189篇 |
2010年 | 160篇 |
2009年 | 157篇 |
2008年 | 188篇 |
2007年 | 211篇 |
2006年 | 175篇 |
2005年 | 135篇 |
2004年 | 110篇 |
2003年 | 97篇 |
2002年 | 95篇 |
2001年 | 69篇 |
2000年 | 69篇 |
1999年 | 107篇 |
1998年 | 123篇 |
1997年 | 95篇 |
1996年 | 71篇 |
1995年 | 76篇 |
1994年 | 77篇 |
1993年 | 70篇 |
1992年 | 60篇 |
1991年 | 37篇 |
1990年 | 55篇 |
1989年 | 57篇 |
1988年 | 40篇 |
1987年 | 49篇 |
1986年 | 37篇 |
1985年 | 53篇 |
1984年 | 52篇 |
1983年 | 52篇 |
1982年 | 32篇 |
1981年 | 37篇 |
1980年 | 10篇 |
1979年 | 31篇 |
1978年 | 18篇 |
1977年 | 24篇 |
1976年 | 23篇 |
1975年 | 15篇 |
1973年 | 12篇 |
排序方式: 共有3739条查询结果,搜索用时 15 毫秒
991.
Marvin KA Johnson JA Rodenbusch SE Gong L Vanden Bout DA Stevenson KJ 《Analytical chemistry》2012,84(11):5154-5158
Spectrophotometric titration and a binding isotherm were used to accurately assess the loading capacity of generation four polyamido(amine) (PAMAM) dendrimer templates with terminal alcohol groups (G4-OH). Preparation of bimetallic G4-OH dendrimer-encapsulated metal nanoclusters (DENs) necessitates knowledge of the precise metal-ion binding capacity. The binding of metal ions such as Pt(2+) and Pd(2+) has proven difficult to assess via UV-vis spectroscopy because the absorbance shifts associated with metal-ion binding within the dendrimer template are masked by the absorbance of the PAMAM dendrimer itself. In contrast, the binding of Cu(2+) to G4-OH PAMAM dendrimer results in a strong, distinct absorption band at 300 nm, making UV-vis spectrophotometric titration with copper straightforward. Here we use copper binding as a means to assess the number of binding sites remaining within the PAMAM G4-OH dendrimer after the complexation of a specified molar excess of Pd(2+) or Pt(2+). In addition, we use a binding isotherm to mathematically estimate the loading capacity of the dendrimer in each case. The loading capacities for M(2+) in the G4-OH dendrimer were found to be ~16 for copper alone, ~21 for copper combined with palladium, and ~25 for copper combined with platinum. 相似文献
992.
Kazuhisa Mitsuda Richard L. Kelley Kevin R. Boyce Gregory V. Brown Elisa Costantini Michael J. DiPirro Yuichiro Ezoe Ryuichi Fujimoto Keith C. Gendreau Jan-Willem den Herder Akio Hoshino Yoshitaka Ishisaki Caroline A. Kilbourne Shunji Kitamoto Dan McCammon Masahide Murakami Hiroshi Murakami Mina Ogawa Takaya Ohashi Atsushi Okamoto Stéphane Paltani Martin Pohl F. Scott Porter Yoichi Sato Keisuke Shinozaki Peter J. Shirron Gary A. Sneiderman Hiroyuki Sugita Andrew Szymkowiak Yoh Takei Toru Tamagawa Makoto Tashiro Yukikatsu Terada Masahiro Tsujimoto Cor de Vries Noriko Y. Yamasaki 《Journal of Low Temperature Physics》2012,167(5-6):795-802
The science and an overview of the Soft X-ray Spectrometer onboard the STRO-H mission are presented. The SXS consists of X-ray focusing mirrors and a microcalorimeter array and is developed by international collaboration lead by JAXA and NASA with European participation. The detector is a 6×6 format microcalorimeter array operated at a cryogenic temperature of 50 mK and covers a 3′×3′ field of view of the X-ray telescope of 5.6 m focal length. We expect an energy resolution better than 7 eV (FWHM, requirement) with a goal of 4 eV. The effective area of the instrument will be 225 cm2 at 7 keV; by a factor of about two larger than that of the X-ray microcalorimeter on board Suzaku. One of the main scientific objectives of the SXS is to investigate turbulent and/or macroscopic motions of hot gas in clusters of galaxies. 相似文献
993.
The performance of a single platinum (Pt) nanowire for detecting H(2) in air is reported. A Pt nanowire shows no resistance change upon exposure to H(2) in N(2), but H(2) exposure in air causes a reversible resistance decrease for H(2) concentrations above 10 ppm. The amplitude of the resistance change induced by H(2) exposure and the time rate of change of the nanowire resistance both increased with increasing temperature from 298 to 550 K. This resistance decrease of the Pt nanowire in the presence of H(2) results from reduced electron diffuse scattering at hydrogen-covered Pt surfaces as compared with oxygen-covered platinum surfaces, we hypothesize. The properties for the detection of H(2) in air of single Pt and Pd nanowires of similar size are compared in this study. Pt nanowires have a limit-of-detection for H(2) (LOD(H(2))) of 10 ppm; 3 orders of magnitude lower than for Pd nanowires of the same size, as well as a response time that is 1/100th of Pd for [H(2)] ≈ 1%. 相似文献
994.
Intrinsically disordered proteins are highly abundant in various proteomes. They are different from ordered proteins at many levels, and their structural and functional characterization requires special experimental and computational tools. 相似文献
995.
Campuzano I Bush MF Robinson CV Beaumont C Richardson K Kim H Kim HI 《Analytical chemistry》2012,84(2):1026-1033
We present the use of drug-like molecules as a traveling wave (T-wave) ion mobility (IM) calibration sample set, covering the m/z range of 122.1-609.3, the nitrogen collision cross-section (Ω(N(2))) range of 124.5-254.3 ?(2) and the helium collision cross-section (Ω(He)) range of 63.0-178.8 ?(2). Absolute Ω(N(2)) and Ω(He) values for the drug-like calibrants and two diastereomers were measured using a drift-tube instrument with radio frequency (RF) ion confinement. T-wave drift-times for the protonated diastereomers betamethasone and dexamethasone are reproducibly different. Calibration of these drift-times yields T-wave Ω(N(2)) values of 189.4 and 190.4 ?(2), respectively. These results demonstrate the ability of T-wave IM spectrometry to differentiate diastereomers differing in Ω(N(2)) value by only 1 ?(2), even though the resolution of these IM experiments were ~40 (Ω/ΔΩ). Demonstrated through density functional theory optimized geometries and ionic electrostatic surface potential analysis, the small but measurable mobility difference between the two diastereomers is mainly due to short-range van der Waals interactions with the neutral buffer gas and not long-range charge-induced dipole interactions. The experimental RF-confining drift-tube and T-wave Ω(N(2)) values were also evaluated using a nitrogen based trajectory method, optimized for T-wave operating temperature and pressures, incorporating additional scaling factors to the Lennard-Jones potentials. Experimental Ω(He) values were also compared to the original and optimized helium based trajectory methods. 相似文献
996.
Li Li Xiangdong Yao Chenghua Sun Aijun Du Lina Cheng Zhonghua Zhu Chengzhong Yu Jin Zou Sean C. Smith Ping Wang Hui‐Ming Cheng Ray L. Frost Gao Qing Lu 《Advanced functional materials》2009,19(2):265-271
Ammonia borane (AB) has attracted tremendous interest for on‐board hydrogen storage due to its low molecular weight and high gravimetric hydrogen capacity below a moderate temperature. However, the slow kinetics, irreversibility, and formation of volatile materials (trace borazine and ammonia) limit its practical application. In this paper, a new catalytic strategy involved lithium (Li) catalysis and nanostructure confinement in mesoporous carbon (CMK‐3) for the thermal decomposition of AB is developed. AB loaded on the 5% Li/CMK‐3 framework releases ~7 wt % of hydrogen at a very low temperature (around 60 °C) and entirely suppresses borazine and ammonia emissions that are harmful for proton exchange membrane fuel cells. The possible mechanism for enhanced hydrogen release via catalyzed thermal decomposition of AB is discussed. 相似文献
997.
998.
Oleksandr A. Byelashov Jeremy M. Adler Ifigenia Geornaras Kyung Yuk Ko Keith E. Belk Gary C. Smith John N. Sofos 《Journal of food science》2010,75(4):M209-M217
ABSTRACT: Escherichia coli O157:H7 may become internalized during brine injection of meat. This study evaluated the effect of brining ingredients on E. coli O157:H7 in a meat model system after simulated brining, storage, and cooking. Fresh knuckles (5.3 ± 2.4% fat) or beef shoulder (15.3 ± 2.2% fat) were ground individually, mixed with an 8-strain composite of rifampicin-resistant E. coli O157:H7 (7 log CFU/g) and brining solutions. Treatments included no brining, distilled water, sodium chloride (NaCl, 0.5%), sodium tripolyphosphate (STP, 0.25%), sodium pyrophosphate (SPP, 0.25%), NaCl + STP, NaCl + SPP, NaCl + STP + potassium lactate (PL, 2%), NaCl + STP + sodium diacetate (SD, 0.15%), NaCl + STP + PL + SD, NaCl + STP + lactic acid (0.3%), NaCl + STP + acetic acid (0.3%), NaCl + STP + citric acid (0.3%), NaCl + STP + EDTA (20 mM) + nisin (0.0015%) or pediocin (1000 AU/g), NaCl + STP + sodium metasilicate (0.2%), NaCl + STP + cetylpyridinium chloride (CPC; 0.5%), and NaCl + STP + hops beta acids (0.00055%). Samples (30 g) were analyzed for pH, and total microbial and rifampicin-resistant E. coli O157:H7 (inoculum) populations immediately after mixing, storage (24 h at 4 °C), and cooking to 65 °C. Fat and moisture contents and water activity were measured after storage and cooking only; cooking losses also were determined. The effect of beef type on microbial counts, pH, and water activity was negligible. No reductions in microbial counts were obtained by the brining solutions immediately or after storage, except for samples treated with CPC, which reduced (P < 0.05) pathogen counts after storage by approximately 1 log cycle. Cooking reduced pathogen counts by 1.5 to 2.5 logs, while CPC-treated samples had the lowest (P < 0.05) counts compared to any other treatment. These data may be useful in developing/improving brining recipes for control of E. coli O157:H7 in moisture-enhanced beef products. 相似文献
999.
Sunan Wang Weikang Zhao Asad Raza Robert Friendship Roger Johnson Magdalena Kostrzynska Keith Warriner 《Journal of the science of food and agriculture》2010,90(13):2318-2325
BACKGROUND: There is interest in applying bacteriophages to control Salmonella in pig production and pork processing. The following reports on the prevalence of Salmonella infecting bacteriophages within Ontario pig farms and associated with the holding area of a pork slaughterhouse. RESULTS: Salmonella infecting bacteriophages were present in 30 and 28 of the effluent manure samples collected from 36 farms using S. Typhimurium DT104 or S. Heidelberg as host cell respectively. Bacteriophages were recovered in 95–100% of the 48 samples taken from holding pens within a high capacity slaughterhouse over a 12 month period. Bacteriophages isolated from farms exhibited similar host ranges which differed to that of slaughterhouse isolates. Salmonella (n = 21) from the slaughterhouse were susceptible to the endogenous bacteriophages. Despite being susceptible to the resident phages, the Salmonella populations were found to be genetically stable with the same genotypes being recovered over successive visits. Salmonella isolated from the farms were frequently resistant to the endogenous phages. CONCLUSIONS: Bacteriophages are prevalent in the pig slaughterhouse environment although they do not have a significant impact on the genetic structure of Salmonella populations. However, there was evidence that the Salmonella population structure on farms is influenced by the presence of infecting phages. Copyright © 2010 Society of Chemical Industry 相似文献
1000.