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   927篇
  免费   67篇
  2024年   1篇
  2023年   11篇
  2022年   24篇
  2021年   41篇
  2020年   20篇
  2019年   31篇
  2018年   37篇
  2017年   45篇
  2016年   51篇
  2015年   49篇
  2014年   69篇
  2013年   85篇
  2012年   76篇
  2011年   84篇
  2010年   38篇
  2009年   37篇
  2008年   42篇
  2007年   45篇
  2006年   37篇
  2005年   22篇
  2004年   30篇
  2003年   27篇
  2002年   25篇
  2001年   17篇
  2000年   5篇
  1999年   5篇
  1998年   1篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1991年   1篇
  1990年   1篇
  1989年   4篇
  1987年   1篇
  1986年   2篇
  1985年   2篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1978年   1篇
  1976年   1篇
  1973年   2篇
  1968年   1篇
  1965年   1篇
  1944年   1篇
排序方式: 共有994条查询结果,搜索用时 31 毫秒
1.
International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body...  相似文献   
2.
3.
4.
The rat optic nerve is a useful model for stem cell regeneration research. Direct injection into the rat optic nerve allows delivery into the central nervous system in a minimally-invasive surgery without bone removal. This technique describes an approach to visualization and direct injection of the optic nerve following minor fascial dissection from the orbital ridge, using a conjunctival traction suture to gently pull the eye down and out. Representative examples of an injected optic nerve show successful injection of dyed beads.  相似文献   
5.
The seroprevalence of human T cell leukemia virus type 1 (HTLV-1) infection was investigated in Brazilians (570): native inhabitants (298) and descendants from Japanese (272) living in Recife and its neighborhoods—North-east of Brazil. Furthermore, polytransfused renal transplanted patients (54) were also examined for the serological status to this virus. The seropositivity to HTLV-1, screened by enzyme-linked immunosorbent assay (ELISA), was low: 1.34% for the local population and 0.73% for the descendants from Japanese. However, the seropositivity for the renal transplanted patients was found to be 11.1%. This higher value suggests that this retrovirus infection seems to be of importance in this clinical condition.  相似文献   
6.
This article describes the phytochemical study of Cannabis sativa roots from northeastern Brazil. The dried plant material was pulverized and subjected to exhaustive maceration with ethanol at room temperature, obtaining the crude ethanolic extract (Cs-EEBR). The volatile compounds were analyzed by gas chromatography coupled with mass spectrometry (GC/MS), which allowed to identify 22 compounds by comparing the linear retention index (LRI), the similarity index (SI) and the fragmentation pattern of the constituents with the literature. By this technique the major compounds identified were: friedelan-3-one and β-sitosterol. In addition, two fractions were obtained from Cs-EEBR by classical column chromatography and preparative thin layer chromatography. These fractions were analyzed by NMR and IR and together with the mass spectrometry data allowed to identify the compounds: epifriedelanol, friedelan-3-one, β-sitosterol and stigmasterol. The study contributed to the phytochemical knowledge of Cannabis sativa, specifically the roots, as there are few reports on the chemical constituents of this part of the plant.  相似文献   
7.
Summary A study of the ammonium transport system of Zygosaccharomyces bailii was carried out using methylammonium as a non-metabolizable analogue. Benzoic acid in the growth medium decreased the capacity of the transport system from 1.46 ± 0.11 mmol.g–1.h–1 to 0.41±0.04 mmol.g–1.h–1, while the affinity for ammonium was not significatively affected. Although ammonium uptake was inhibited by benzoic acid, the ammonium transport system was still active at preservative concentrations which fully inhibited growth suggesting that inhibition of growth was not governed by the uptake of this nutrient.  相似文献   
8.
9.
Summary Four siblings with the autosomal recessive Roberts syndrome are reported, and we discuss the phenotypic overlap of this syndrome with other similar radial, aplasia syndromes.  相似文献   
10.
Ascorbate oxidase is present in homogenates of the flesh of Cucurbita maxima fruits. Its activity is independent of ascorbate concentration over th  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