全文获取类型
收费全文 | 2437篇 |
免费 | 87篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 2525篇 |
出版年
2022年 | 18篇 |
2021年 | 26篇 |
2020年 | 24篇 |
2019年 | 30篇 |
2018年 | 34篇 |
2017年 | 41篇 |
2016年 | 40篇 |
2015年 | 49篇 |
2014年 | 61篇 |
2013年 | 189篇 |
2012年 | 86篇 |
2011年 | 112篇 |
2010年 | 98篇 |
2009年 | 77篇 |
2008年 | 100篇 |
2007年 | 96篇 |
2006年 | 97篇 |
2005年 | 76篇 |
2004年 | 87篇 |
2003年 | 84篇 |
2002年 | 57篇 |
2001年 | 41篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 42篇 |
1997年 | 33篇 |
1996年 | 38篇 |
1995年 | 25篇 |
1994年 | 31篇 |
1993年 | 39篇 |
1992年 | 33篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 33篇 |
1984年 | 35篇 |
1983年 | 23篇 |
1982年 | 21篇 |
1981年 | 33篇 |
1980年 | 19篇 |
1979年 | 20篇 |
1978年 | 25篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1975年 | 21篇 |
1974年 | 25篇 |
1972年 | 18篇 |
排序方式: 共有2525条查询结果,搜索用时 15 毫秒
991.
Ababneh ZQ Ababneh R Maier SE Winalski CS Oshio K Ababneh AM Mulkern RV 《Magma (New York, N.Y.)》2008,21(4):273-278
PURPOSE: To assess the transverse relaxation time T(2) and diffusion coefficient D before and following exercise in the tibialis anterior muscle and determine whether T(2) and D values were correlated. METHODS: Measurements of T(2) and D were performed at 3 T within axial slices through the calf muscles of six healthy volunteers at 95 s intervals before and for 10-12 min after a dorsiflexion exercise to exhaustion. RESULTS: The mean +/- standard deviation (SD) of T(2) and D before exercise were 32 +/- 1.55 ms and 1.52 +/- 0.15 mum(2)/ms, and after exercise were 43 +/- 2.5 ms and 1.72 +/- 0.13 mum(2)/ms, respectively. The mean +/- SD inter-individual recovery times of the % change in T(2) and D after exercise were 7.9 +/- 4.2 and 10.9 +/- 7.0 min, respectively. The T(2) and D values showed a significant correlation throughout the experiments (r (2) = 0.45). CONCLUSIONS: The increase in T(2) of skeletal muscle after exercise is correlated with the increase of the diffusion coefficient D and the recovery times appear similar, indicating that any model used to explain T(2) increases with exercise must also account for increased diffusion coefficients. 相似文献
992.
Kazdin (see record 2008-03389-001) pointed out that the requirement for evidence-based practice (EBP) has made the long-standing gap between research and practice in clinical psychology even more salient. He offered several strategies for bridging this gap: investigating mechanisms and moderators of therapeutic change, and qualitative research. We agree that qualitative research can be useful in bridging the gap between research and clinical practice (Silverstein & Auerbach, 2007; Silverstein, Auerbach, & Levant, 2006). In this comment we discuss using qualitative research to develop EBP that is culturally competent. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Mia J. Cunicelli Hem S. Bhandari Pengyin Chen Carl E. Sams M. A. Rouf Mian Leandro A. Mozzoni Christopher J. Smallwood Vincent R. Pantalone 《Journal of the American Oil Chemists' Society》2019,96(8):927-935
There is a known negative correlation between soybean [Glycine max [L.] Merr.] seed protein and oil and between protein and yield. This challenges breeders to increase protein concentration while maintaining oil concentration and yield. The objective of this study was to determine if marker-assisted selection for the Danbaekkong (Dan) protein allele on chromosome 20 influences seed yield and quality traits in near isogenic genetic backgrounds. A population of 24 F7-derived near isogenic lines (NIL) of soybean was created by crossing G03-3101 × LD00-2817P. The 24 NIL consisted of 12 wild type (WT) and 12 mutant Dan type lines. These NIL were grown in 2016 and 2017 field seasons in replicated field trials in nine environments, with six in Tennessee and one each in Arkansas, Missouri, and North Carolina. There were significant (P < 0.05) differences in yield, protein, and oil concentrations between the two experimental groups. The Dan group had significantly (P < 0.05) more protein (421 g kg−1), less oil (192 g kg−1), and lower yield (3143 kg ha−1) than the WT group (390 g kg−1 protein, 210 g kg−1 oil, and 3281 kg ha−1 yield). These results support previous research and corroborate the overall negative genetic correlations. Nevertheless, seed yield of several higher-protein Dan lines MC-13, MC-16, MC-19, and MC-24 exceeded seed yield of lower protein WT lines MC-2, MC-3, MC-6, and MC-10. The higher-protein lines represent genetic resources for reducing the negative correlation between protein and yield. 相似文献
994.
Most flame‐retarded polymer products need to be highly durable throughout their service lifetime in many demanding applications areas such as construction, transportation, electric equipment, and textiles, where low flammability in combination with high resistance toward oxidative deterioration triggered by the action of light, heat, and/or mechanical stress is a mandatory quality. To achieve this, it is essential to better understand the overall interplay (both physical and chemical processes) between different components such as different flame retardant structures in their respective polymers and in the presence of coadditives such as processing stabilizers, antioxidants, light stabilizers, metal deactivators, filler deactivators, ultraviolet absorbers, and so on, in the flame‐retarded polymer product. In this article, the key difficulties in improving weathering resistance of flame‐retarded polymers are reviewed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
995.
996.
997.
998.
999.
This study examines the ability of chemometrics methods, namely multivariate image analysis (MIA) and Grey Level Co-occurrence Matrix analysis (GLCM), to extract meaningful information from visible and near-infrared spectral images of extruded wood/plastic composite materials for predicting spatio-temporal variations in their properties. The samples were produced under varying process and feed conditions according to designed experiments. Mechanical properties of the samples were measured using standard analytical methods both during steady-state and dynamic transition periods. A Bootstrap-PLS regression technique was first used for selecting the spectral bands (i.e. wavelengths) that were the most highly correlated with the material properties. In a second step, a more parsimonious PLS regression model was built between the spectral and textural features extracted from the lower dimensional spectral images and the corresponding quality properties of each sample. The imaging sensor was able to simultaneously monitor 7 properties in both steady-state operation and during transitions. 相似文献
1000.
A combined discrete element method (DEM)–Monte Carlo simulation algorithm is used to investigate intra-tablet coating thickness variability for six pharmaceutical tablet shapes. The DEM simulations are used to collect tablet orientations when the tablets enter a specified spray zone. The Monte Carlo simulations are used to “coat” the tablets assuming a uniform spray and orientations chosen randomly from the distribution generated by the DEM simulations. The simulations demonstrate that for the non-spherical tablet shapes investigated here, the coating thickness variability, defined using a coefficient of variation, decreases with the square root of the number of coating trials, then approaches an asymptotic value. The greater the degree of a tablet's preferred orientation, the larger the asymptotic coefficient of variation. In addition, the number of trials required to reach this asymptote decreases for larger asymptotic values. These findings are consistent with theoretical analyses. For the range of parameters investigated, increasing the pan speed decreases the asymptotic coefficient of variation, but increasing the fill level had no consistent effect. The asymptotic coefficients of variation did not correlate with tablet sphericity, aspect ratio, or band-to-tablet area ratio, but the results suggest that a measure of a tablet's symmetry may provide better results. Modifying the angle of the coating spray so that a larger portion of the band is coated during each coating trial results in smaller asymptotic coefficients of variation than when the spray is oriented normal to the tablet bed surface. In addition, the relative order of the tablets with the smallest asymptotic coefficients of variation changes when the spray orientation is changed. 相似文献