全文获取类型
收费全文 | 71092篇 |
免费 | 15822篇 |
国内免费 | 34篇 |
学科分类
工业技术 | 86948篇 |
出版年
2024年 | 67篇 |
2023年 | 317篇 |
2022年 | 338篇 |
2021年 | 1087篇 |
2020年 | 2158篇 |
2019年 | 3979篇 |
2018年 | 4245篇 |
2017年 | 4502篇 |
2016年 | 5064篇 |
2015年 | 4788篇 |
2014年 | 4972篇 |
2013年 | 7472篇 |
2012年 | 4628篇 |
2011年 | 4142篇 |
2010年 | 4047篇 |
2009年 | 3816篇 |
2008年 | 3310篇 |
2007年 | 3097篇 |
2006年 | 2520篇 |
2005年 | 2140篇 |
2004年 | 2046篇 |
2003年 | 1944篇 |
2002年 | 1865篇 |
2001年 | 1547篇 |
2000年 | 1476篇 |
1999年 | 909篇 |
1998年 | 2449篇 |
1997年 | 1693篇 |
1996年 | 1069篇 |
1995年 | 650篇 |
1994年 | 499篇 |
1993年 | 579篇 |
1992年 | 233篇 |
1991年 | 228篇 |
1990年 | 165篇 |
1989年 | 172篇 |
1988年 | 171篇 |
1987年 | 146篇 |
1986年 | 133篇 |
1985年 | 153篇 |
1984年 | 131篇 |
1983年 | 103篇 |
1982年 | 136篇 |
1981年 | 153篇 |
1980年 | 159篇 |
1979年 | 81篇 |
1978年 | 81篇 |
1977年 | 289篇 |
1976年 | 624篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
61.
62.
Joon‐Young Jun Sosuke Nakajima Koji Yamazaki Yuji Kawai Hajime Yasui Yasuyuki Konishi 《International Journal of Food Science & Technology》2015,50(4):871-877
Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria. 相似文献
63.
64.
65.
66.
67.
Machine Learning - We propose a data-driven approach to quantify the uncertainty of models constructed by kernel methods. Our approach minimizes the needed distributional assumptions, hence,... 相似文献
68.
Maria A. Ospina Monica Pizarro Thierry Tran Julien Ricci John Belalcazar Jorge L. Luna Luis F. Londoño Sandra Salazar Hernan Ceballos Dominique Dufour Luis A. Becerra Lopez-Lavalle 《International Journal of Food Science & Technology》2021,56(3):1343-1353
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes. 相似文献
69.
70.
Matthew O'Sullivan Daire
hUallachin Patrícia Oliveira Antunes Eleanor Jennings Mary Kelly‐Quinn 《河流研究与利用》2019,35(2):146-158
Cattle access to streams has been linked globally with degradation of stream water quality, driven largely by bank erosion and resultant instream, fine sediment deposition. The majority of evidence on such effects is however based in arid and semiarid regions of the United States and Australia, with few studies relating to cool temperate climates such as Northwest Europe. In this study, “Quorer” resuspendable sediment samples were taken from riffle geomorphic units upstream (control) and at two points downstream (pressure and recovery) of cattle access points in headwater streams in agricultural catchments in Ireland to assess levels of deposited stream sediment. Samples were taken in April/May (2016) prior to the grazing season and in October (2016) at the end of the grazing season. Sites in good‐high ecological status catchments and less than good ecological status catchments were included in the study. Higher levels of sediment were found downstream of cattle access points in both good‐high status and less than good status catchments; however, the impacts of access points were spatially confined to, in most cases, the area immediately downstream of the point of access. There was a strong correlation between deposited sediment mass and organic matter (OM) mass, with levels of OM increasing linearly with deposited sediment mass. Levels of measured sediment were negatively correlated with riparian habitat health (measured using a qualitative habitat assessment). The results of this study highlight the need for measures to prevent cattle access to headwater streams where access points can be many in order to manage local habitat quality and downstream water quality issues. 相似文献