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   1952篇
  免费   170篇
  国内免费   1篇
  2123篇
  2023年   18篇
  2022年   27篇
  2021年   46篇
  2020年   37篇
  2019年   36篇
  2018年   50篇
  2017年   33篇
  2016年   60篇
  2015年   88篇
  2014年   94篇
  2013年   115篇
  2012年   161篇
  2011年   140篇
  2010年   69篇
  2009年   70篇
  2008年   94篇
  2007年   102篇
  2006年   91篇
  2005年   66篇
  2004年   112篇
  2003年   66篇
  2002年   52篇
  2001年   39篇
  2000年   37篇
  1999年   24篇
  1998年   18篇
  1997年   12篇
  1996年   11篇
  1995年   8篇
  1994年   8篇
  1993年   14篇
  1992年   16篇
  1991年   28篇
  1990年   22篇
  1989年   19篇
  1988年   19篇
  1987年   13篇
  1986年   16篇
  1985年   8篇
  1984年   22篇
  1983年   8篇
  1982年   12篇
  1981年   9篇
  1979年   12篇
  1978年   11篇
  1977年   14篇
  1975年   11篇
  1972年   9篇
  1970年   13篇
  1966年   9篇
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
101.
102.
A series of cationic lipo-benzamide compounds with varying lengths of hydrocarbon chains (C2MC18M) were evaluated for anti-Candida activity. Four compounds harbouring 8–11 hydrocarbon chains demonstrated concentration-dependent inhibition of fungal cell growth with Minimum Inhibitory Concentration (MIC) of ≤6.2?µg?ml?1. The most active compound (C9M) inhibited growth of both Candida albicans and non-albicans strains and is equally active against pairs of azole sensitive and resistant clinical isolates of C. albicans. Compound C9M also inhibited different stages of Candida biofilms. Scanning Electron Microscopy (SEM) of Candida cells after C9M treatment was also done and no significant cell lysis was observed. Hemolysis assay was performed and only 2.5% haemolysis was observed at MIC concentration.  相似文献   
103.

Cervical cancer (CC) is one of the leading causes of death in women due to cancer and a major concern in the developing world. Persistent human papilloma virus (HPV) infection is the major causative agent for CC. Besides HPV infection, genetic and epigenetic factors including microRNA (miRNA) also contribute to the malignant transformation. Earlier studies have revealed that miRNAs participate in cell proliferation, invasion and metastasis, angiogenesis, and chemoresistance processes by binding and inversely regulating the target oncogenes or tumor suppressor genes. Based on functions and mechanistic insights, miRNAs have been identified as cellular modulators that have an enormous role in diagnosis, prognosis, and cancer therapy. Signatures of miRNA could be used as diagnostic markers which are necessary for early diagnosis and management of CC. The therapeutic potential of miRNAs has been shown in CC; however, more comprehensive clinical trials are required for the clinical translation of miRNA-based diagnostics and therapeutics. Understanding the molecular mechanism of miRNAs and their target genes has been useful to develop miRNA-based therapeutic strategies for CC and overcome chemoresistance. In this review, we summarize the role of miRNAs in the development, progression, and metastasis of CC as well as chemoresistance. Further, we discuss the diagnostic and therapeutic potential of miRNAs to overcome chemoresistance and treatment of CC.

  相似文献   
104.
105.
A plasmid marker rescue system based on restoration of the nptII gene was established in Streptococcus gordonii to study the transfer of bacterial and transgenic plant DNA by transformation. In vitro studies revealed that the marker rescue efficiency depends on the type of donor DNA. Plasmid and chromosomal DNA of bacteria as well as DNA of transgenic potatoes were transferred with efficiencies ranging from 8.1 x 10(-6) to 5.8 x 10(-7) transformants per nptII gene. Using a 792-bp amplification product of nptII the efficiency was strongly decreased (9.8 x 10(-9)). In blood sausage, marker rescue using plasmid DNA was detectable (7.9 x 10(-10)), whereas in milk heat-inactivated horse serum (HHS) had to be added to obtain an efficiency of 2.7 x 10(-11). No marker rescue was detected in extracts of transgenic potatoes despite addition of HHS. In vivo transformation of S. gordonii LTH 5597 was studied in monoassociated rats by using plasmid DNA. No marker rescue could be detected in vivo, although transformation was detected in the presence of saliva and fecal samples supplemented with HHS. It was also shown that plasmid DNA persists in rat saliva permitting transformation for up to 6 h of incubation. It is suggested that the lack of marker rescue is due to the absence of competence-stimulating factors such as serum proteins in rat saliva.  相似文献   
106.
Epoxide hydrolases (EHs) of fungal origin have the ability to catalyze the enantioselective hydrolysis of epoxides to their corresponding diols. However, wild type fungal EHs are limited in substrate range and enantioselectivity. Additionally, the production of fungal epoxide hydrolase (EH) by wild-type strains is typically very low. In the present study, the EH-encoding gene from Rhodotorula araucariae was functionally expressed in Yarrowia lipolytica, under the control of a growth phase inducible hp4d promoter, in a multi-copy expression cassette. The transformation experiments yielded a positive transformant, with a final EH activity of 220 U/g dw in shake-flask cultures. Evaluation of this transformant in batch fermentations resulted in ~ 7-fold improvement in EH activity over the flask scale. Different constant specific feed rates were tested in fed-batch fermentations, resulting in an EH activity of 1,750 U/g dw at a specific feed rate of ~ 0.1 g/g/h, in comparison to enzyme production levels of 0.3 U/g dw for the wild type R. araucariae and 52 U/g dw for an Escherichia coli recombinant strain expressing the same gene. The expression of EH in Y. lipolytica using a multi-copy cassette demonstrates potential for commercial application.  相似文献   
107.
Data on 60-Hz electric field (EF) induced reduction in growth rate of plant roots have strongly supported the hypothesis that the effect is related to an EF-induced transmembrane potential (V i m). An investigation was undertaken to determine if this hypothesis is also applicable to 60-Hz EF-induced reductions in growth rate of mammalian cells in vitro. Human lymphoblastic (RPMI 1788) and human carcinoma (HeLa) cells were selected for study, the former having a relatively small diameter (11.2 m), and the latter having a relatively large diameter (15.4 tm). The 60-Hz EFs ranged from 430–1200 V/m in the culture medium. The growth rate of RPMI 1788 cells after 4-days was depressed by about 42% at a 60-Hz EF of 1000–1200 V/m with a response threshold occurring at 950 V/m; theV i m at the response threshold was 8 mV There was no 60-Hz EF-induced effect on HeLa cell growth rate of aV i m of 8 mV (60-Hz EF=700 V/m); a statistically significant effect was achieved atV i m of 11 mV (950 V/m). The data support the hypothesis that above a threshold 60-Hz EF,V i m acts as the initial signal leading to growth rate reductions.  相似文献   
108.
109.
The conversion of both parental- and progeny-nascent open circular M13 RF DNA into covalently closed RF I is drastically reduced in an E. coli mutant deficient in the 5′ → 3′ exonuclease associated with DNA polymerase I. The nascent progeny RF DNA also contains a significant proportion of fragments of smaller than unit length.  相似文献   
110.
Three phase partitioning for extraction of oil from soybean   总被引:4,自引:0,他引:4  
Three phase partitioning, a method generally used for protein separation, has been evaluated for extraction of oil from soybean. 82% oil was extracted within 1 h using this process which required simultaneous addition of t-butanol (1:1, v/v) and 30% ammonium sulphate to the soybean slurry.  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