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   925篇
  免费   63篇
  2023年   8篇
  2022年   4篇
  2021年   31篇
  2020年   21篇
  2019年   17篇
  2018年   29篇
  2017年   35篇
  2016年   47篇
  2015年   37篇
  2014年   60篇
  2013年   58篇
  2012年   58篇
  2011年   50篇
  2010年   42篇
  2009年   29篇
  2008年   30篇
  2007年   45篇
  2006年   23篇
  2005年   24篇
  2004年   35篇
  2003年   39篇
  2002年   27篇
  2001年   22篇
  2000年   17篇
  1999年   15篇
  1998年   7篇
  1995年   5篇
  1994年   8篇
  1992年   9篇
  1991年   11篇
  1990年   5篇
  1989年   4篇
  1988年   11篇
  1987年   7篇
  1986年   12篇
  1985年   7篇
  1984年   5篇
  1983年   5篇
  1982年   9篇
  1981年   8篇
  1980年   7篇
  1979年   10篇
  1978年   4篇
  1976年   4篇
  1975年   4篇
  1974年   7篇
  1973年   4篇
  1969年   4篇
  1968年   6篇
  1966年   5篇
排序方式: 共有988条查询结果,搜索用时 15 毫秒
41.
Plant and Soil - Phytoextraction is an in situ technique that can be applied to minerals and mining wastes using hyperaccumulator plants to purposely bio-concentrate high levels of metals or...  相似文献   
42.
43.
This work was based on field screening procedure to detect the population density of Aphis craccivora for two successive seasons (2004–2005) and (2005–2006) to emphasis the relation between the economic injury level (EIL) and yield loss.

Results obtained showed that the equilibrium position (steady point) during the first and second season was 9.06 and 3.32 individuals/five leaflets, respectively, while the injury level was 3.4 and 1.16 individuals/leaflets. When the bean plant was subjected to three successive insecticidal applications during the early growing, season is sufficient to decrease the yield loss significantly (yield capacity 21.43 Ard./fed.) with comparing to untreated plant (14.98 Ard./fed.), while the plants exposure for one treatment was 17.36 Ard./fed. The EIL was 8.6 individual of aphids/plant depending on the market price of bean and control cost during the season.  相似文献   
44.

Objectives

Donor specific antibodies (DSA) and a positive cross‐match are contraindications for kidney transplantation. Trials of allograft transplantation across the HLA barrier have employed desensitization strategies, including the use of plasmapheresis, intravenous immunoglobulins, anti‐B‐cell monoclonal antibodies and splenectomy, associated with high‐intensity immunosuppressive regimens. Our case 1 report suffered from repeatedly positive lymphocyte cross match after 1st renal transplantation. Graft nephrectomy could not correct the state of sensitization. Splenectomy was done in a trial to get rid of the antibody producing clone. Furthermore plasmapheresis with low dose IVIG could not as well revert the state of sensitization for the patient.

Material and methods

About 50 millions donor specific MSCs were injected to the patient.

Results

MSCs transfusion proved to be the only procedure which could achieve successful desensitization before performing the second transplantation owing to their immunosuppressive properties.

Conclusion

This case indicates that DS‐MSCs is a potential option for anti‐HLA desensitization. In cases 2 and 3 IV DS‐MSCs transfusion was selected from the start as a successful line of treatment for pre renal transplantation desensitization to save other unnecessary lines of treatment that were tried in case 1.
  相似文献   
45.
The molecular phylogeny of the genus Odontobuthus Vachon, 1950 (Scorpiones: Buthidae) in Iran was evaluated using two mitochondrial DNA genes, cytochrome c oxidase, subunit I (COI) and 16S ribosomal RNA (16S rRNA). The molecular phylogenetic analyses were performed using Maximum Parsimony, Maximum Likelihood and Bayesian inference methods. The resulting topologies supported two main clades: the clade comprising Odontobuthus doriae, O. bidentatus, and O. tavighiae, and another one which is the O. tirgari clade. The results clearly presented additional support for the taxonomic validity of the recently described species, O. tirgari and O. tavighiae. In addition, the monophyly of two previously described species O. doriae and O. bidentatus was confirmed. According to the data presented here, three taxonomically valid species belonging to the genus Odontobuthus occur in Iran.  相似文献   
46.
47.
48.
We designed and synthesized new series of diverse triazoles, isoxazoles, isoxazolines, and aziridines linked 4-methylumbelliferone 1 using intermolecular 1,3-dipolar cycloaddition reactions. Structures of these compounds were established on the basis of 1H NMR, 13C NMR, and ESI-HRMS. All prepared compounds were evaluated for their antimicrobial, anticoagulant, and anticholinesterase activities. Interestingly, among the tested molecules, some of the analogs displayed better activities than the parent 4-methylumbelliferone 1 such as 6a and 6d for their antifungal properties. Moreover, compounds 4, 5, 6, and 7 showed the importance of the added fragments to 4-methylumbelliferone 1 via the linker methylene to have good activity.  相似文献   
49.
In response to environmental changes, Pseudomonas aeruginosa is able to switch from a planktonic (free swimming) to a sessile (biofilm) lifestyle. The two-component system (TCS) GacS/GacA activates the production of two small non-coding RNAs, RsmY and RsmZ, but four histidine kinases (HKs), RetS, GacS, LadS and PA1611, are instrumental in this process. RetS hybrid HK blocks GacS unorthodox HK autophosphorylation through the formation of a heterodimer. PA1611 hybrid HK, which is structurally related to GacS, interacts with RetS in P. aeruginosa in a very similar manner to GacS. LadS hybrid HK phenotypically antagonizes the function of RetS by a mechanism that has never been investigated. The four sensors are found in most Pseudomonas species but their characteristics and mode of signaling may differ from one species to another. Here, we demonstrated in P. aeruginosa that LadS controls both rsmY and rsmZ gene expression and that this regulation occurs through the GacS/GacA TCS. We additionally evidenced that in contrast to RetS, LadS signals through GacS/GacA without forming heterodimers, either with GacS or with RetS. Instead, we demonstrated that LadS is involved in a genuine phosphorelay, which requires both transmitter and receiver LadS domains. LadS signaling ultimately requires the alternative histidine-phosphotransfer domain of GacS, which is here used as an Hpt relay by the hybrid kinase. LadS HK thus forms, with the GacS/GacA TCS, a multicomponent signal transduction system with an original phosphorelay cascade, i.e. H1LadS→D1LadS→H2GacS→D2GacA. This highlights an original strategy in which a unique output, i.e. the modulation of sRNA levels, is controlled by a complex multi-sensing network to fine-tune an adapted biofilm and virulence response.  相似文献   
50.
A new caryophyllene, named pulicaryenne A ( 1 ), along with four other known caryophyllene derivatives ( 2 , 3 , 4 and 5 ) were isolated from the ethyl acetate extract of aerial parts of Pulicaria vulgaris Gaertn . (Asteraceae). All compounds were isolated for the first time from this species. Compound 2 was identified as a new epimer of a known caryophyllene derivative isolated previously from P. dysenterica. Their structures were established by spectroscopic means including NMR analysis (1D‐ and 2D‐NMR) and ESI‐TOF‐MS. All compounds were evaluated for their anticholinesterase, antityrosinase and cytotoxic activities against two human cell lines (A549 and HeLa). Results showed that compound 5 exhibited the highest cytotoxic effect against A549 and anticholinesterase activity with IC50 values of 8.50±0.75 and 6.45±0.09 μg/mL, respectively. Furthermore, compound 5 showed also an interesting antityrosinase activity with percent inhibition value of 79.0±2.5 % at 50 μg/mL. The bioactivity and drug likeness scores of the isolated compounds 1–5 were calculated using Molinspiration software and discussed. These results may suggest that the five caryophyllene derivatives endowed with good biological properties, which could be used as bioactive alternatives in pharmaceutical preparations.  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