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   1164篇
  免费   40篇
  国内免费   1篇
  1205篇
  2023年   17篇
  2022年   40篇
  2021年   50篇
  2020年   26篇
  2019年   35篇
  2018年   53篇
  2017年   40篇
  2016年   51篇
  2015年   61篇
  2014年   68篇
  2013年   91篇
  2012年   101篇
  2011年   71篇
  2010年   34篇
  2009年   38篇
  2008年   37篇
  2007年   32篇
  2006年   24篇
  2005年   20篇
  2004年   15篇
  2003年   21篇
  2002年   18篇
  2001年   20篇
  2000年   11篇
  1999年   8篇
  1998年   10篇
  1997年   7篇
  1994年   4篇
  1993年   5篇
  1992年   6篇
  1991年   8篇
  1990年   14篇
  1989年   10篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   4篇
  1978年   4篇
  1977年   5篇
  1960年   4篇
  1953年   3篇
  1938年   5篇
  1936年   9篇
  1935年   5篇
  1933年   8篇
  1932年   9篇
  1931年   9篇
  1929年   7篇
  1923年   3篇
  1918年   3篇
排序方式: 共有1205条查询结果,搜索用时 0 毫秒
51.
52.
An in vitro propagation system for Artemisia vulgaris L., a traditional medicinal plant, has been developed. The best organogenic response, including adventitious shoot number and elongation, was obtained when hypocotyl segments were cultured onto MS medium supplemented with 4.54 μM TDZ (N-phenyl-N′-(1,2,3-thidiazol-yl) urea). Up to 28 shoots formed per explant for an optimal duration of exposure of 48 days. Regenerated shoots formed roots when subcultured onto a medium containing 8.56 μM IAA (indole-3-acetic acid). Healthy plantlets were transferred to a garden soil:farmyard soil:sand (2:1:1) mixture for acclimatization, which was successful, and subsequent maturity was achieved under greenhouse conditions over a six-month period. The survival rate of the plantlets varied under acclimatization. The regeneration protocol developed in this study provides a basis for germplasm conservation and for further investigation of medicinally active constituents of A. vulgaris. This optimized protocol has been successfully employed for genetic transformation studies in A. vulgaris, which are currently underway in our laboratory.  相似文献   
53.
54.
55.
In order to identify a high carbon-sequestering microalgal strain, the physiological effect of different concentrations of carbon sources on microalgae growth was investigated. Five indigenous strains (I-1, I-2, I-3, I-4 and I-5) and a reference strain (I-0: Coccolithus pelagicus 913/3) were subjected to CO2 concentrations of 0.03–15% and NaHCO3 of 0.05–2 g CO2 l–1. The logistic model was applied for data fitting, as well as for estimation of the maximum growth rate (μmax) and the biomass carrying capacity (Bmax). Amongst the five indigenous strains, I-3 was similar to the reference strain with regards to biomass production values. The Bmax of I-3 significantly increased from 214 to 828 mg l–1 when CO2 concentration was increased from 0.03 to 15% (r = 0.955, P = 0.012). Additionally, the Bmax of I-3 increased with increasing NaHCO3 (r = 0.885, P = 0.046) and was recorded at 153 mg l–1 (at 0.05 g CO2 l–1) and 774 mg l–1 at (2 g CO2 l–1). Relative electron transport rate (rETR) and maximum quantum yield (Fv/Fm) were also applied to assess the impact of elevated carbon sources on the microalgal cells at the physiological level. Isolate I-3 displayed the highest rETR confirming its tolerance to higher quantities of carbon. Additionally, the decline in Fv/Fm with increasing carbon was similar for strains I-3 and the reference strain. Based on partial 28s ribosomal RNA gene sequencing, strain I-3 was homologous to the ribosomal genes of Chlorella sp.  相似文献   
56.
57.
The continuous advancements in cancer research have contributed to the overwhelming evidence of the presence of telomerase in primary and secondary tumours together with hsp90 and c-Myc. This review will discuss the important role of telomerase together with hsp90 and c-Myc within the initiation and progression of gliomas. Also it will review the differential expression of these genes in the different grades of gliomas and the possibility of new treatments targeting these specific genes.  相似文献   
58.
A survey of faba bean and chickpea for virus infection, conducted during February 1994 in the Sudan, showed that bean yellow mosaic potyvirus and broad bean mottle bromovirus occurred commonly in both crops. Chickpea chlorotic dwarf geminivirus (CCDV) was detected for the first time in naturally infected chickpeas and faba beans. This is the first report of natural CCDV infection of chickpeas outside India and the first record of chickpea and faba bean infection in West Asia and North Africa (WANA).  相似文献   
59.
Mesenchymal stromal cells (MSCs) show promise in cell-based transplantations and regenerative medicine applications. MSCs from Wharton’s jelly (WJ) of umbilical cord can be easily harvested and exhibit greater proliferative activity than bone marrow MSCs. It is important to develop a practical cryopreservation technique to effectively store umbilical cord for potential future applications. Successful cryopreservation would allow access to umbilical cord from the same donor for repeated WJ MSC-based transplantations. For therapeutic applications, one should be able to obtain clinically-relevant quality and quantity of MSCs from cryopreserved tissues. In this study, we optimised a serum-free formulation of 10% dimethyl sulfoxide (DMSO) and 0.2 M sucrose for cryopreservation of umbilical cord tissue. Slow freezing and rapid thawing were adopted. MSCs harvested from WJ of cryopreserved umbilical cord could undergo robust expansion, differentiate to mesodermal lineages and express MSC-characteristic surface antigens. The cumulative cell yield, however, was less compared to corresponding fresh cord tissue.  相似文献   
60.

Objectives

Betulin (BT) is an abundant triterpene found predominantly in the bark of Himalayan birch. It is difficult to deliver it in vivo because of its low aqueous solubility. We have therefore developed novel formulations of BT for improving its solubility, bioavailability and therapeutic efficacy.

Results

Poly-d,l-lactide nanovectors (PLA NVs) were synthesized using poly(vinyl alcohol) and Lonicera japonica leaf extract (LE) as a stabiliser and named as PLA-1 NVs and PLA-2 NVs. PLA-1 NVs and PLA-2 NVs were used for the encapsulation of betulin (BT) and named as BT-En-1 and BT-En-2 NVs. The encapsulation efficiency of BT-En-1 and BT-En-2 NVs were 99.3 and 100 % respectively. Prepared nanoformulations were physically stable. An in vitro study revealed 45 % BT was released over 24 h. BT had a prolonged release from BT-En-2 NVs as compared to BT-En-1 NVs. BT-En-2 NVs had better anticancerous activity against SiHa cells than BT-En-1 NVs.

Conclusions

Developed BT-EN-2 NVs had better biocompatibility, excellent stability and enhanced release characteristics than BT-En-1 NVs.
  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