全文获取类型
收费全文 | 1096篇 |
免费 | 66篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 37篇 |
2020年 | 29篇 |
2019年 | 30篇 |
2018年 | 47篇 |
2017年 | 31篇 |
2016年 | 39篇 |
2015年 | 55篇 |
2014年 | 57篇 |
2013年 | 73篇 |
2012年 | 92篇 |
2011年 | 107篇 |
2010年 | 58篇 |
2009年 | 38篇 |
2008年 | 59篇 |
2007年 | 62篇 |
2006年 | 34篇 |
2005年 | 34篇 |
2004年 | 42篇 |
2003年 | 26篇 |
2002年 | 22篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 14篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1967年 | 2篇 |
1961年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有1162条查询结果,搜索用时 31 毫秒
71.
Deepak Singh Archana Kumari S. Ramaswamy Gurunath Ramanathan 《Biochemical and biophysical research communications》2014
3-Nitotoluene dioxygenase (3-NTDO) is the first enzyme in the degradation pathway of 3-nitrotoluene (3-NT) by Diaphorobacter sp. strain DS2. The complete gene sequences of 3-NTDO were PCR amplified from genomic DNA of Diaphorobacter sp., cloned, sequenced and expressed. The 3-NTDO gene revealed a multi component structure having a reductase, a ferredoxin and two oxygenase subunits. Clones expressing the different subunits were constructed in pET21a expression vector system and overexpressed in E. coli BL21(DE3) host. Each subunit was individually purified separately to homogeneity. The active recombinant enzyme was reconstituted in vitro by mixing all three purified subunits. The reconstituted recombinant enzyme could catalyse biotransformations on a variety of organic aromatics. 相似文献
72.
Genetic engineering of fluorescent pseudomonads for various industrially, agriculturally and environmentally important bioprocesses
often involves the use of suitable plasmids. Plasmid-mediated alterations in host physiology and metabolism are poorly understood
for this group of organisms. Thus, we investigated the metabolic perturbations in Pseudomonas fluorescens 13525 due to the independent and combined presence of broad-host-range plasmids, pBBR1MCS-2 (copy number 30) and pUCPM18
derived pAB4 and pAB8 (copy number 14-16). Presence of pAB4 and pAB8 not only significantly increased the growth rate and
glucose utilization of P. fluorescens 13525, but also increased glucose dehydrogenase activity and gluconic acid production indicating enhanced direct oxidative
pathway for glucose catabolism. Additionally, increased secretion of pyruvic, acetic, and citric acids caused faster media
acidification in presence of pAB4 and pAB8. Simultaneous presence of pAB4/pAB8 in Pf (pAB48) and pAB4/pBBR1MCS-2 in Pf (pAB4BBR1MCS-2) reduced their respective copy numbers to nearly half. Pf (pAB48) demonstrated further increase in direct oxidation pathway without altering growth and glucose depletion rates, as
compared with single transformants. Conversely, pBBR1MCS-2 plasmid did not greatly alter P. fluorescens 13525 metabolism when present independently but masked the effects imposed by pAB4 when present in its combination. In conclusion,
P. fluorescens 13525 redesigns its metabolism in response to the presence of plasmids irrespective of their nature, by enhancing anaplerosis
with a simultaneous reduction in catabolism as indicated by increased pyruvate carboxylase and decreased citrate synthase
activities, respectively. Such information will be helpful for vector designing during genetic engineering of fluorescent
pseudomonads. 相似文献
73.
Archana Aggarwal Man Mohan Misro Ankur Maheshwari Neeta Sehgal Deoki Nandan 《Molecular reproduction and development》2010,77(10):900-909
We have earlier reported that following persistent stimulation with hCG, oxidative stress‐induced apoptosis in rat Leydig cells was mainly achieved through the extrinsic pathway. In the present study, the role of N‐acetylcysteine (NAC) in counteracting the oxidative stress and the mechanisms of inhibition of apoptosis under such conditions were investigated. NAC (1 mM) intervention with repeated hCG stimulation (50 ng/ml, four times, each with 30 min challenge) prevented the decline in Leydig cell viability and the rise in lipid peroxidation and reactive oxygen species. Simultaneously, the activities of the enzymes glutathione‐S‐transferase, catalase, superoxide dismutase and the intracellular glutathione and antioxidant capacity of the treated cells improved significantly. Apoptotic markers Fas, FasL, and caspase‐8, up‐regulated following repeated hCG exposure, were significantly down‐regulated following NAC co‐incubation. While Bcl‐2 expression was fully restored, Bax and caspase‐9 remained unchanged. NAC treatment induced down‐regulation of upstream JNK/pJNK and down‐stream caspase‐3 in the target cells. Taken together, the above findings indicate that NAC counteracted the oxidative stress in Leydig cells induced as a result of repeated hCG stimulation, and inhibited apoptosis by mainly regulating the extrinsic and JNK pathways of metazoan apoptosis. Mol. Reprod. Dev. 77:900–909, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
74.
Archana Mathur Ajay Kumar Mathur Anita Gangwar Sharawan Yadav Priyanka Verma Rajender Singh Sangwan 《In vitro cellular & developmental biology. Plant》2010,46(1):13-21
A root-derived callus line of Panax sikkimensis that stably accumulates anthocyanins was established by small cell aggregate selection method. The selected line showed a
growth index of 221.36 and an anthocyanin content of 2.76 mg/g fw (7.076% dw) in 50–60 d of growth on a modified MS medium
containing 4.5 μM 2,4-dichlorophenoxy acetic acid and 1.2 μM kinetin under 16-h light and 8-h dark photoperiodic conditions.
Incubation under continuous light increased the growth index to 435.57 but led to a marginal dilution of anthocyanin content
to 2.192 mg/g fw (6.928% dw). The purple-red pigment had absorption maximum at 528 nm. The selected callus line has shown
sustained growth and productivity for more than 6 yr now. Interestingly, pigment accumulation in the selected line did not
hinder the ginsenoside production in the callus tissue (0.9–1.2% fw). 相似文献
75.
Soma Roy Kiranmayee Rao Ch. Bhuvaneswari Archana Giri Lakshmi Narasu Mangamoori 《World journal of microbiology & biotechnology》2010,26(1):85-91
The present study describes the phytochemical profile and antimicrobial activity of Andrographis paniculata. For the present investigation, two samples of A. paniculata extracts, obtained by extraction in chloroform and chloroform + HCl, respectively, were compared for their antimicrobial
activity and further subjected to GC-MS analysis to find out the nature of the compounds responsible for the antimicrobial
activity. The antibacterial activities were assessed by measuring the diameter of the inhibition zones, MIC and MBC values.
Compared to the chloroform + HCl extract, the chloroform extract showed better antimicrobial activity against all the nine
pathogenic bacterial strains tested. The chloroform extract was observed to be active against the opportunistic and pathogenic
gram-negative bacteria, indicating its potential application related to noscomial infections. GC-MS results revealed phenols,
aromatic carboxylic acids and esters in the chloroform extract to be the molecules responsible for the antimicrobial activity
of A. paniculata. This is the first report on analysis of antimicrobial components from A. paniculata, and our results confer the utility of this plant extract in developing a novel broad spectrum antimicrobial agent. 相似文献
76.
The “marine world” is endowed with diverse life forms. The life under the oceans is bestowed with a unique gene pool and characteristics
owing to extreme conditions such as high salt concentration and temperature variations. The marine biodiversity is an extremely
rich resource for the development of a wide array of applications in food, pharmaceuticals, cosmetics. Various forms of traditional
knowledge, including traditional medicinal knowledge, have been silently developing over the centuries, with the coastal tribes
in nations across the globe. Unfortunately, marine traditional knowledge has been underestimated both commercially and legally.
It has still not gained its due importance at the international platform for sustainable use and development. An attempt has
been made in the present study to collate information on marine traditional knowledge based medicine. Recent trends of marine
bioprospecting by various nations including India have been discussed, followed by the study of legal provisions dealing with
marine bioprospecting that aim at conservation and sustainable use of marine biodiversity and associated traditional knowledge.
Convention of Biological Diversity, United Nations Convention on the Law of the Seas and World Intellectual Property Organization
are the major international legal instruments that discuss the concepts of Prior Informed Consent, access and benefit sharing
with regard to biopiracy and provide guidelines and limits for conducting marine scientific research. 相似文献
77.
Pankaj Partani Sanjay Gurule Arshad Khuroo Tausif Monif Sandeep Bhardwaj 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(3-4):428-434
A rapid, selective and sensitive high performance liquid chromatography–tandem mass spectrometry method (LC–MS/MS) was developed and validated for the determination and pharmacokinetic investigation of cefuroxime in human plasma. Cefuroxime and the internal standard (IS), cefoxitin, were extracted from plasma samples using solid phase extraction with Oasis HLB cartridges. Chromatographic separation was performed on a LiChrospher® 60 RP Select B column (125 mm × 4 mm i.d., 5 μm particle size) using acetonitrile:5 ± 0.2 mM ammonium acetate solution:glacial acetic acid (70:30:0.020, v/v/v) as the mobile phase at a flow rate of 0.8 mL/min. Detection of cefuroxime and cefoxitin was achieved by tandem mass spectrometry with an electrospray ionization (ESI) interface in negative ion mode. The calibration curves were linear over the range of 81.0–15976.2 ng/mL with the lower limit of quantitation validated at 81.0 ng/mL. The intra- and inter-day precisions were within 7.6%, while the accuracy was within ±6.3% of nominal values. No matrix effect was observed in this method. The validated LC–MS/MS method was successfully applied for the evaluation of pharmacokinetic and bioequivalence parameters of cefuroxime after an oral administration of 500 mg cefuroxime tablet to 36 healthy male volunteers. 相似文献
78.
H. Gupta R. K. Malik A. Bhardwaj G. Kaur S. De J. K. Kaushik 《Indian journal of microbiology》2010,50(2):145-155
Enterococcus faecium FH 99 was isolated from human faeces and selected because of its broad spectrum of inhibitory activity against several Gram-positive
foodborne spoilage and pathogenic bacteria. Ent. faecium FH 99 accumulates enterocin in large number in early stationary phase of the growth. The enterocin FH 99 was stable over
a wide pH range (2–10) and recovered activity even after treatment at high temperatures (10 min at 100°C). The enterocin was
subjected to different purification techniques viz., gel filteration, cation exchange chromatography and reverse-phase high-performance liquid chromatography. The activity was
eluted as one individual active fraction. SDSPAGE revealed a molecular weight of less than 6.5 kDa. Studies carried out to
identify the genetic determinants for bacteriocin production showed that this trait may be plasmid encoded as loss in both
of the plasmids (size>chromosomal DNA) led to loss in bacteriocin production by Ent. faecium FH 99. Ent. faecium strain FH 99 is a newly discovered high bacteriocin producer with Activity Units 1.8 × 105 AU ml−1 and its characteristics indicate that it may have strong potential for application as a protective agent against pathogens
and spoilage bacteria in foods. 相似文献
79.
Archana Mathur Anita Gangwar Ajay K. Mathur Priyanka Verma Girish C. Uniyal Raj K. Lal 《Biotechnology letters》2010,32(3):457-461
A thin, profusely branched, fast growing hairy root line of Panax quinquefolium (American ginseng) was established by co-culturing epicotyl explants with a wild type strain of Agrobacterium rhizogenes. The transformed roots grew by over 10-fold from the initial inoculum within 8 weeks. The crude ginsenosides content in the roots was about 0.2 g/g dry wt level up to the 10th week of culture. Ginsenosides Rb2, Rd, Re, Rf and Rg1 constituted 47–49% of the crude saponin fraction between 6 and 8 weeks of growth whereas, Rc ginsenoside was accumulated only after 9th weeks when the biomass started receding. PCR amplification analysis of the hairy roots confirmed their transgenic nature by showing the presence of Ri-TL DNA with rolA, rolB and rolC genes in their genome. 相似文献
80.
R. K. Sharma M. S. Negi S. Sharma P. Bhardwaj R. Kumar E. Bhattachrya S. B. Tripathi D. Vijayan A. R. Baruah S. C. Das B. Bera R. Rajkumar J. Thomas R. K. Sud N. Muraleedharan M. Hazarika M. Lakshmikumaran S. N. Raina P. S. Ahuja 《Biochemical genetics》2010,48(7-8):549-564
India has a large repository of important tea accessions and, therefore, plays a major role in improving production and quality of tea across the world. Using seven AFLP primer combinations, we analyzed 123 commercially important tea accessions representing major populations in India. The overall genetic similarity recorded was 51%. No significant differences were recorded in average genetic similarity among tea populations cultivated in various geographic regions (northwest 0.60, northeast and south both 0.59). UPGMA cluster analysis grouped the tea accessions according to geographic locations, with a bias toward China or Assam/Cambod types. Cluster analysis results were congruent with principal component analysis. Further, analysis of molecular variance detected a high level of genetic variation (85%) within and limited genetic variation (15%) among the populations, suggesting their origin from a similar genetic pool. 相似文献