首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   17676篇
  免费   3864篇
  国内免费   111篇
林业   1214篇
农学   897篇
基础科学   100篇
  4272篇
综合类   538篇
农作物   728篇
水产渔业   3337篇
畜牧兽医   8143篇
园艺   240篇
植物保护   2182篇
  2023年   97篇
  2022年   148篇
  2021年   442篇
  2020年   761篇
  2019年   1251篇
  2018年   1322篇
  2017年   1366篇
  2016年   1355篇
  2015年   1130篇
  2014年   1215篇
  2013年   1626篇
  2012年   1366篇
  2011年   1325篇
  2010年   1097篇
  2009年   690篇
  2008年   875篇
  2007年   739篇
  2006年   657篇
  2005年   643篇
  2004年   568篇
  2003年   522篇
  2002年   445篇
  2001年   298篇
  2000年   327篇
  1999年   211篇
  1998年   55篇
  1997年   70篇
  1996年   42篇
  1995年   42篇
  1994年   29篇
  1993年   31篇
  1992年   63篇
  1991年   47篇
  1990年   57篇
  1989年   58篇
  1988年   43篇
  1987年   46篇
  1986年   51篇
  1985年   54篇
  1984年   42篇
  1983年   37篇
  1982年   23篇
  1981年   17篇
  1979年   37篇
  1978年   37篇
  1977年   33篇
  1974年   29篇
  1973年   47篇
  1972年   34篇
  1971年   27篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Lupinus albus seeds contain conglutin gamma (Cγ) protein, which exerts a hypoglycemic effect and positively modifies proteins involved in glucose homeostasis. Cγ could potentially be used to manage patients with impaired glucose metabolism, but there remains a need to evaluate its effects on hepatic glucose production. The present study aimed to analyze G6pc, Fbp1, and Pck1 gene expressions in two experimental animal models of impaired glucose metabolism. We also evaluated hepatic and renal tissue integrity following Cγ treatment. To generate an insulin resistance model, male Wistar rats were provided 30% sucrose solution ad libitum for 20 weeks. To generate a type 2 diabetes model (STZ), five-day-old rats were intraperitoneally injected with streptozotocin (150 mg/kg). Each animal model was randomized into three subgroups that received the following oral treatments daily for one week: 0.9% w/v NaCl (vehicle; IR-Ctrl and STZ-Ctrl); metformin 300 mg/kg (IR-Met and STZ-Met); and Cγ 150 mg/kg (IR-Cγ and STZ-Cγ). Biochemical parameters were assessed pre- and post-treatment using colorimetric or enzymatic methods. We also performed histological analysis of hepatic and renal tissue. G6pc, Fbp1, and Pck1 gene expressions were quantified using real-time PCR. No histological changes were observed in any group. Post-treatment G6pc gene expression was decreased in the IR-Cγ and STZ-Cγ groups. Post-treatment Fbp1 and Pck1 gene expressions were reduced in the IR-Cγ group but increased in STZ-Cγ animals. Overall, these findings suggest that Cγ is involved in reducing hepatic glucose production, mainly through G6pc inhibition in impaired glucose metabolism disorders.  相似文献   
2.
3.
4.
The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm3) and RMD (132.7 μg/cm3) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm3) and RMD (138.7 μg/cm3) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.  相似文献   
5.
6.
New Forests - Native trees from the Caribbean were tested for seed desiccation responses, by adapting the “100-seed test” protocol. Ninety-seven seed lots of 91 species were collected...  相似文献   
7.
Journal of Crop Science and Biotechnology - The cultivation of sweet corn is expanding in Brazil, but there are serious constraints about the availability of commercial cultivars. The selection of...  相似文献   
8.
Phytophthora pluvialis and Phytophthora kernoviae are the causal agents of important needle diseases on Pinus radiata in New Zealand. Little is known about the epidemiology of the diseases, making the development of control strategies challenging. To investigate the seasonality and climatic drivers of sporulation, inoculum traps, consisting of pine fascicles floating on water in plastic containers, were exchanged fortnightly at five sites in P. radiata plantations between February 2012 and December 2014. Sections of needle baits were plated onto selective media and growth of Phytophthora pluvialis and P. kernoviae recorded. To explore the generalizability of these data, they were compared to detection data for both pathogens from the New Zealand Forest Health Database (NZFHDB). Further, equivalent analyses on infection of Rhododendron ponticum by P. kernoviae in Cornwall, UK allowed the comparison of the epidemiology of P. kernoviae across different host systems and environments. In New Zealand, inoculum of P. pluvialis and P. kernoviae was detected between January–December and March–November, respectively. Inoculum of both species peaked in abundance in late winter. The probability of detecting P. pluvialis and P. kernoviae was greater at lower temperatures, while the probability of detecting P. pluvialis also increased during periods of wet weather. Similar patterns were observed in NZFHDB data. However, the seasonal pattern of infection by P. kernoviae in the UK was the opposite of that seen for sporulation in New Zealand. Phytophthora kernoviae was likely limited by warmer and drier summers in New Zealand, but by colder winter weather in the UK. These results emphasize the importance of considering both environmental drivers and thresholds in improving our understanding of pathogen epidemiology.  相似文献   
9.
Not all economically disadvantaged—“less developed” or “lagging”—regions are the same. They are, however, often bundled together for the purposes of innovation policy design and implementation. This paper attempts to determine whether such bundling is warranted by conducting a regional level investigation for Canada, the United States, on the one hand, and Europe, on the other, to (a) identify the structural and socioeconomic factors that drive patenting in the less developed regions of North America and Europe, respectively; and (b) explore how these factors differ between the two contexts. The empirical analysis, estimated using a mixed‐model approach, reveals that, while there are similarities between the drivers of innovation in North America's and Europe's lagging regions, a number of important differences between the two continents prevail. The analysis also indicates that the territorial processes of innovation in North America's and Europe's less developed regions are more similar to those of their more developed counterparts than to one another.  相似文献   
10.
Increasingly, economies that have traditionally benefited from offshoring are losing some of their strategical advantages, with a consequent increase in backshoring by developed economies. This paper describes the phenomenon and tries to shed light on the current challenges, trends, and debates in the area, and on the main determinants of backshoring. A new phenomenon known as nearshoring is also analysed—this consists of relocating some previously offshored manufacturing activities so that they are now close to previous core locations, but not so close as to suffer from disagglomeration effects. This combines the advantages of offshoring and backshoring.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号