全文获取类型
收费全文 | 1417篇 |
免费 | 65篇 |
专业分类
1482篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 29篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 39篇 |
2017年 | 33篇 |
2016年 | 27篇 |
2015年 | 59篇 |
2014年 | 71篇 |
2013年 | 85篇 |
2012年 | 116篇 |
2011年 | 81篇 |
2010年 | 61篇 |
2009年 | 64篇 |
2008年 | 88篇 |
2007年 | 56篇 |
2006年 | 65篇 |
2005年 | 65篇 |
2004年 | 52篇 |
2003年 | 48篇 |
2002年 | 44篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 23篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1482条查询结果,搜索用时 0 毫秒
991.
Sengupta K Alluri KV Satish AR Mishra S Golakoti T Sarma KV Dey D Raychaudhuri SP 《Arthritis research & therapy》2008,10(4):R85
Introduction
5-Loxin® is a novel Boswellia serrata extract enriched with 30% 3-O-acetyl-11-keto-beta-boswellic acid (AKBA), which exhibits potential anti-inflammatory properties by inhibiting the 5-lipoxygenase enzyme. A 90-day, double-blind, randomized, placebo-controlled study was conducted to evaluate the efficacy and safety of 5-Loxin® in the treatment of osteoarthritis (OA) of the knee.Methods
Seventy-five OA patients were included in the study. The patients received either 100 mg (n = 25) or 250 mg (n = 25) of 5-Loxin® daily or a placebo (n = 25) for 90 days. Each patient was evaluated for pain and physical functions by using the standard tools (visual analog scale, Lequesne''s Functional Index, and Western Ontario and McMaster Universities Osteoarthritis Index) at the baseline (day 0), and at days 7, 30, 60 and 90. Additionally, the cartilage degrading enzyme matrix metalloproteinase-3 was also evaluated in synovial fluid from OA patients. Measurement of a battery of biochemical parameters in serum and haematological parameters, and urine analysis were performed to evaluate the safety of 5-Loxin® in OA patients.Results
Seventy patients completed the study. At the end of the study, both doses of 5-Loxin® conferred clinically and statistically significant improvements in pain scores and physical function scores in OA patients. Interestingly, significant improvements in pain score and functional ability were recorded in the treatment group supplemented with 250 mg 5-Loxin® as early as 7 days after the start of treatment. Corroborating the improvements in pain scores in treatment groups, we also noted significant reduction in synovial fluid matrix metalloproteinase-3. In comparison with placebo, the safety parameters were almost unchanged in the treatment groups.Conclusion
5-Loxin® reduces pain and improves physical functioning significantly in OA patients; and it is safe for human consumption. 5-Loxin® may exert its beneficial effects by controlling inflammatory responses through reducing proinflammatory modulators, and it may improve joint health by reducing the enzymatic degradation of cartilage in OA patients.Trail Registration
(Clinical trial registration number: ISRCTN05212803.) 相似文献992.
Villa H Otero Marcos AR Reguera RM Balaña-Fouce R García-Estrada C Pérez-Pertejo Y Tekwani BL Myler PJ Stuart KD Bjornsti MA Ordóñez D 《The Journal of biological chemistry》2003,278(6):3521-3526
A common feature shared by type I DNA topoisomerases is the presence of a "serine, lysine, X, X, tyrosine" motif as conventional enzyme active site. Preliminary data have shown that Leishmania donovani DNA topoisomerase I gene (LdTOP1A) lacked this conserved motif, giving rise to different theories about the reconstitution of an active DNA topoisomerase I in this parasite. We, herein, describe the molecular cloning of a new DNA topoisomerase I gene from L. donovani (LdTOP1B) containing the highly conserved serine, lysine, X, X, tyrosine motif. DNA topoisomerase I activity was detected only when both genes (LdTOP1A and LdTOP1B) were co-expressed in a yeast expression system, suggesting the existence of a dimeric DNA topoisomerase I in Leishmania parasites. 相似文献
993.
Sonal Dalvi Sei Azetsu Marianna A. Patrauchan Deniz F. Aktas Babu Z. Fathepure 《Applied and environmental microbiology》2012,78(20):7309-7316
Lately, there has been a special interest in understanding the role of halophilic and halotolerant organisms for their ability to degrade hydrocarbons. The focus of this study was to investigate the genes and enzymes involved in the initial steps of the benzene degradation pathway in halophiles. The extremely halophilic bacteria Arhodomonas sp. strain Seminole and Arhodomonas sp. strain Rozel, which degrade benzene and toluene as the sole carbon source at high salinity (0.5 to 4 M NaCl), were isolated from enrichments developed from contaminated hypersaline environments. To obtain insights into the physiology of this novel group of organisms, a draft genome sequence of the Seminole strain was obtained. A cluster of 13 genes predicted to be functional in the hydrocarbon degradation pathway was identified from the sequence. Two-dimensional (2D) gel electrophoresis and liquid chromatography-mass spectrometry were used to corroborate the role of the predicted open reading frames (ORFs). ORFs 1080 and 1082 were identified as components of a multicomponent phenol hydroxylase complex, and ORF 1086 was identified as catechol 2,3-dioxygenase (2,3-CAT). Based on this analysis, it was hypothesized that benzene is converted to phenol and then to catechol by phenol hydroxylase components. The resulting catechol undergoes ring cleavage via the meta pathway by 2,3-CAT to form 2-hydroxymuconic semialdehyde, which enters the tricarboxylic acid cycle. To substantiate these findings, the Rozel strain was grown on deuterated benzene, and gas chromatography-mass spectrometry detected deuterated phenol as the initial intermediate of benzene degradation. These studies establish the initial steps of the benzene degradation pathway in halophiles. 相似文献
994.
George?M?WarimweEmail author Gema?Lorenzo Elena?Lopez-Gil Arturo?Reyes-Sandoval Matthew?G?Cottingham Alexandra?J?Spencer Katharine?A?Collins Matthew?DJ?Dicks Anita?Milicic Amar?Lall Julie?Furze Alison?V?Turner Adrian?VS?Hill Alejandro?Brun Sarah?C?Gilbert 《Virology journal》2013,10(1):349
Background
Rift Valley Fever (RVF) is a viral zoonosis that historically affects livestock production and human health in sub-Saharan Africa, though epizootics have also occurred in the Arabian Peninsula. Whilst an effective live-attenuated vaccine is available for livestock, there is currently no licensed human RVF vaccine. Replication-deficient chimpanzee adenovirus (ChAd) vectors are an ideal platform for development of a human RVF vaccine, given the low prevalence of neutralizing antibodies against them in the human population, and their excellent safety and immunogenicity profile in human clinical trials of vaccines against a wide range of pathogens.Methods
Here, in BALB/c mice, we evaluated the immunogenicity and efficacy of a replication-deficient chimpanzee adenovirus vector, ChAdOx1, encoding the RVF virus envelope glycoproteins, Gn and Gc, which are targets of virus neutralizing antibodies. The ChAdOx1-GnGc vaccine was assessed in comparison to a replication-deficient human adenovirus type 5 vector encoding Gn and Gc (HAdV5-GnGc), a strategy previously shown to confer protective immunity against RVF in mice.Results
A single immunization with either of the vaccines conferred protection against RVF virus challenge eight weeks post-immunization. Both vaccines elicited RVF virus neutralizing antibody and a robust CD8+ T cell response.Conclusions
Together the results support further development of RVF vaccines based on replication-deficient adenovirus vectors, with ChAdOx1-GnGc being a potential candidate for use in future human clinical trials.995.
Olaf Kunert Gandhe Sreekanth Gummadi Sreedhar Babu Belvotagi Venkat Rao Adavi Rao Marupaka Radhakishan Bobbala Ravi Kumar Robert Saf Achanta Venkata Narasimha Appa Rao Wolfgang Schühly 《化学与生物多样性》2009,6(8):1185-1192
We report on the chemical investigation of dikamali gum, which is the resin of Gardenia gummifera and G. lucida (Rubiaceae). Six new cycloartane triterpenes, dikamaliartanes A–F ( 1 – 6 , resp.), together with a known flavonoid ( 7 ), were isolated and identified by NMR spectroscopy. All six cycloartanes are characterized by an open A‐ring with a free COOH group at C(3). In four of them, the C‐atoms C(23)–C(27) form a 4‐methylfuran‐2‐yl moiety. Bacterial assays using Staphylococcus aureus, Candida albicans, and Mycobacteria have been carried out but did not reveal significant activity. 相似文献
996.
Background
Understanding how individual genes contribute towards the fitness of an organism is a fundamental problem in biology. Although recent genome-wide screens have generated abundant data on quantitative fitness for single gene knockouts, very few studies have systematically integrated other types of biological information to understand how and why deletion of specific genes give rise to a particular fitness effect. In this study, we combine quantitative fitness data for single gene knock-outs in yeast with large-scale interaction discovery experiments to understand the effect of gene deletion on the modular architecture of protein complexes, under different growth conditions. 相似文献997.
998.
Das A Sujith PP Mourya BS Biche SU LokaBharathi PA 《Extremophiles : life under extreme conditions》2011,15(2):177-189
It is hypothesized that in the deep-sea, under psychrophilic, barophilic and oligotrophic conditions, microbial community
of Central Indian Basin (CIB) sediments could be chemosynthetic. In the dark, at near ambient temperature, 4 ± 2°C, 500 atm
pressure, pelagic red clay could fix carbon at rates ranging from 100 to 500 nmol C g−1 dry wt day−1. These clays accumulate in the deepest and the most remote areas of the ocean and contain <30% biogenic material. These clays
with volcanic signatures fixed 230–9,401 nmol C g−1 dry wt day−1 while siliceous radiolarian oozes of the basin fixed only 5–45 nmol C g−1 dry wt day−1. These rates are comparable to those of white smoker waters and are 1–4 orders of magnitude less than those of bacterial
mats and active vents recorded at other localities worldwide. The experimental ratios of carbon fixation to metal oxidation
in the sediments were 0–1 order of magnitude higher than the corresponding average theoretical ratio of 0.0215 (0.0218, 0.0222,
0.0207 and 0.0211 for Fe, Mn, Co and Ni, respectively) in the siliceous ooze. In case of pelagic red clay it was 0–2 orders
higher than theoretical ratio. Thus, chemosynthetic activity could be more widespread, albeit at low rates, than previously
considered for abyssal basins. These environments may be dependent partially or even wholly on in situ microbial primary production
for their carbon requirements rather than on photosynthetically derived detritus from surface waters. 相似文献
999.
Bajsa J McCluskey A Gordon CP Stewart SG Hill TA Sahu R Duke SO Tekwani BL 《Bioorganic & medicinal chemistry letters》2010,20(22):6688-6695
The antiplasmodial activities of sixty norcantharidin analogs were tested in vitro against a chloroquine sensitive (D6, Sierra Leone) and chloroquine resistant (W2) strains of Plasmodium falciparum. Forty analogs returned IC(50) values <500 μM against at least one of the P. falciparum strains examined. The ring open compound 24 ((1S,4R)-3-(allylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid) is the most active aliphatic analog (D6 IC(50)=3.0±0.0 and W2 IC(50)=3.0±0.8 μM) with a 20-fold enhancement relative to norcantharidin. Surprisingly, seven norcantharimides also displayed good antiplasmodial activity with the most potent, 5 returning D6=8.9±0.9 and W2 IC(50)=12.5±2.2 μM, representing a fivefold enhancement over norcantharidin. 相似文献
1000.
Katayoun Omidi Mohsen Hooshyar Matthew Jessulat Bahram Samanfar Megan Sanders Daniel Burnside Sylvain Pitre Andrew Schoenrock Jianhua Xu Mohan Babu Ashkan Golshani 《PloS one》2014,9(1)
One of the main mechanisms for double stranded DNA break (DSB) repair is through the non-homologous end-joining (NHEJ) pathway. Using plasmid and chromosomal repair assays, we showed that deletion mutant strains for interacting proteins Pph3p and Psy2p had reduced efficiencies in NHEJ. We further observed that this activity of Pph3p and Psy2p appeared linked to cell cycle Rad53p and Chk1p checkpoint proteins. Pph3/Psy2 is a phosphatase complex, which regulates recovery from the Rad53p DNA damage checkpoint. Overexpression of Chk1p checkpoint protein in a parallel pathway to Rad53p compensated for the deletion of PPH3 or PSY2 in a chromosomal repair assay. Double mutant strains Δpph3/Δchk1 and Δpsy2/Δchk1 showed additional reductions in the efficiency of plasmid repair, compared to both single deletions which is in agreement with the activity of Pph3p and Psy2p in a parallel pathway to Chk1p. Genetic interaction analyses also supported a role for Pph3p and Psy2p in DNA damage repair, the NHEJ pathway, as well as cell cycle progression. Collectively, we report that the activity of Pph3p and Psy2p further connects NHEJ repair to cell cycle progression. 相似文献