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   2653篇
  免费   216篇
  国内免费   2篇
  2023年   24篇
  2022年   40篇
  2021年   141篇
  2020年   97篇
  2019年   174篇
  2018年   146篇
  2017年   110篇
  2016年   95篇
  2015年   140篇
  2014年   140篇
  2013年   177篇
  2012年   227篇
  2011年   201篇
  2010年   131篇
  2009年   93篇
  2008年   118篇
  2007年   131篇
  2006年   90篇
  2005年   86篇
  2004年   77篇
  2003年   70篇
  2002年   69篇
  2001年   13篇
  2000年   18篇
  1999年   16篇
  1998年   13篇
  1997年   14篇
  1996年   10篇
  1995年   7篇
  1994年   8篇
  1993年   6篇
  1992年   8篇
  1990年   7篇
  1989年   9篇
  1988年   6篇
  1987年   7篇
  1986年   7篇
  1985年   5篇
  1984年   10篇
  1983年   12篇
  1982年   12篇
  1981年   13篇
  1979年   8篇
  1978年   4篇
  1976年   6篇
  1975年   4篇
  1974年   6篇
  1973年   8篇
  1967年   4篇
  1964年   3篇
排序方式: 共有2871条查询结果,搜索用时 15 毫秒
1.
2.
Islet transplantation has become a promising treatment in the therapy of type 1 diabetes. Its function improvement, after isolation and before transplantation, is crucial because of their loss both in number and function of islets after isolation procedures. Trace elements sodium orthovanadate (SOV) and sodium molybdate (SM), as well as medicinal plant Teucrium polium L. (TP), showed and possessed high beneficial antioxidative potential and even hypoglycemic properties via their effect on islets. We evaluated the effect of these components in combination on cultured islet function in order to improve pancreatic islet transplantation. Rat pancreatic islets were cultured for 24 h then incubated with different concentrations of TP (0.01 and 0.1 mg/mL) alone and in combination with SOV (1 mM) or SM (1 mM). Insulin concentration in buffer media was measured as islet secretory function. Administration of TP (0.01 mg/mL), SM, and SOV alone or in combination with each other significantly increased insulin secretion at high glucose concentration (16.7 mM); insulin secretion was significantly greater in the group containing both TP and SM than other treated groups (p < 0.05). The combination of the mentioned trace elements especially molybdate with TP could improve islet cells function before transplantation.  相似文献   
3.
In this study, the chemical features of dendritic mesoporous silica nanoparticles (DMSNs) provided the opportunity to design a nanostructure with the capability to intelligently transport the payload to the tumor cells. In this regard, doxorubicin (DOX)-encapsulated DMSNs was electrostatically surface-coated with polycarboxylic acid dextran (PCAD) to provide biocompatible dextran-capped DMSNs (PCAD-DMSN@DOX) with controlled pH-dependent drug release. Moreover, a RNA aptamer against a cancer stem cell (CSC) marker, CD133 was covalently attached to the carboxyl groups of DEX to produce a CD133-PCAD-DMSN@DOX. Then, the fabricated nanosystem was utilized to efficiently deliver DOX to CD133+ colorectal cancer cells (HT29). The in vitro evaluation in terms of cellular uptake and cytotoxicity demonstrated that the CD133-PCAD-DMSN@DOX specifically targets HT29 as a CD133 overexpressed cancer cells confirmed by flow cytometry and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay. The potentially promising intelligent-targeted platform suggests that targeted dextran-capped DMSNs may find impressive application in cancer therapy.  相似文献   
4.
5.
6.
7.

Plant nutrition management is known as an efficient strategy to control environmental constraints. This experiment was conducted in a climate control greenhouse with a hydroponic system. The high temperature (36 °C?±?1) was imposed on the pots after fruit formation. The studied factors were silicon in 2 concentrations (0 and 4 parts per thousand (ppt)) and salicylic acid in 3 concentrations (0, 0.5, and 1 mM). They were sprayed on cucumber plants 3 times and under high-temperature conditions to evaluate if they can regulate and improve the yield and quality of cucumber fruit under high-temperature conditions or not. The results showed that all treatments significantly improved the nutritional status, total yield, and fruit quality (including marketable yield (i.e., fruits that can be sold due to their good shape) and nitrate content). Under high-temperature conditions, foliar application of silicon had the highest effect on the increase of total yield and marketable fruit yield (respectively, 36.14% and 40.29% increase compared to the control treatment). Micro-nutrients concentrations in the leaf were significantly increased by Si but a reverse status happened for salicylic acid. Under high temperatures, both treatments also significantly decreased the nitrate content of the fresh matter of fruit but silicon was the superior treatment. Silicon and salicylic acid, respectively, had positive effects on mitigation of adverse effects of high temperature on cucumber plants. These findings suggest the use of these treatments under high-temperature conditions in greenhouse cucumber production.

Graphical Abstract

N–No3 content in dry matter of leaf (left) and fresh matter of fruit (right) affected by different treatments. *SaA0–SiA4: 4 ppt Si; SaA0.5–SiA0: 0.5 mM SA; SaA0.5–SiA4: 0.5 mM SA?+?4 ppt Si; SaA1–SiA0: 1 mM SA; SaA1–SiA4: 1 mM SA?+?4 ppt Si; control: without any SA and Si applications. Means in the same column followed by the same letter are not significantly different according to DMRT at (P?≤?0.05)

  相似文献   
8.
9.
Four genomic arrangements of the maize mitochondrial atpA gene (encoding the α subunit of the F1 ATPase), have been characterized. Most N (fertile) and S (male-sterile) cytoplasms contain two atpA arrangements of equal abundance. Prolonged exposure of blots of maize mitochondrial DNA probed with atpA-specific sequences show that cytoplasms previously reported to lack one of the atpA arrangements do contain the second arrangement but at low levels. Similarly, restriction fragments containing the atpA gene previously thought unique to male-sterile S and T cytoplasms are present in low abundance in fertile cytoplasms. These observations suggest that fertile and male-sterile cytoplasms of maize may be more closely related than previously thought, and suggest possible mechanisms to explain the observed mitochondrial genome diversity.  相似文献   
10.
Summary Axillary bud expiants from South Pacific (Solomon Islands) taro, Colocasia esculenta var. esculenta cv. Akalomamale (Araceae) cultured on a modified Murashige-Skoog medium containing 1 mg NAA 1–1 and TE formed callus and produced multiple plantlets. Explants died if NAA was present at levels lower than 0.1 mg 1–1. BA was not required and may have been inhibitory. Plantlets developed faster and became larger following transfer to a hormone-free medium two weeks after the start of culture. Fully grown plants were established in a potting mix and are growing well in a greenhouse.Abbreviations BA benzyladenine - BM basal medium - Ca Colocasia esculenta var. antiquorum - Ce Colocasia esculenta var. esculenta - Ck cytokinin(s) - CW coconut water - HSMSM half strength Murashige Skoog macroelements - HSMS half strength Murashige and Skoog medium - IM initial medium(ia) - MS Murashige and Skoog medium - NAA naphthaleneacetic acid - SM second medium - TE taro corm extract - UCI University of California, Irvine  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