全文获取类型
收费全文 | 20073篇 |
免费 | 1000篇 |
国内免费 | 29篇 |
专业分类
21102篇 |
出版年
2023年 | 173篇 |
2022年 | 396篇 |
2021年 | 752篇 |
2020年 | 436篇 |
2019年 | 469篇 |
2018年 | 687篇 |
2017年 | 637篇 |
2016年 | 829篇 |
2015年 | 949篇 |
2014年 | 1200篇 |
2013年 | 1648篇 |
2012年 | 1756篇 |
2011年 | 1594篇 |
2010年 | 901篇 |
2009年 | 795篇 |
2008年 | 919篇 |
2007年 | 906篇 |
2006年 | 752篇 |
2005年 | 679篇 |
2004年 | 567篇 |
2003年 | 477篇 |
2002年 | 422篇 |
2001年 | 341篇 |
2000年 | 298篇 |
1999年 | 278篇 |
1998年 | 107篇 |
1997年 | 81篇 |
1996年 | 89篇 |
1995年 | 83篇 |
1994年 | 66篇 |
1993年 | 68篇 |
1992年 | 165篇 |
1991年 | 150篇 |
1990年 | 121篇 |
1989年 | 92篇 |
1988年 | 139篇 |
1987年 | 106篇 |
1986年 | 89篇 |
1985年 | 95篇 |
1984年 | 89篇 |
1983年 | 49篇 |
1982年 | 49篇 |
1981年 | 54篇 |
1980年 | 52篇 |
1979年 | 67篇 |
1978年 | 39篇 |
1977年 | 44篇 |
1976年 | 36篇 |
1973年 | 31篇 |
1972年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
61.
62.
Sudheer Kumar M Sridhar Reddy B Kiran Babu S Bhilegaonkar PM Shirwaikar A Unnikrishnan MK 《Indian journal of experimental biology》2004,42(2):179-185
Maximum antiinflammatory activity of phytic acid (PA) was seen at an oral dose of 150 mg/kg in the carrageenan induced rat paw edema model. Although PA showed ability to prevent denaturation of proteins, it showed less antiinflammatory activity than ibuprofen. Ability of PA to bring down thermal denaturation of proteins might be a contributing factor in the mechanism of action against inflammation. PA, at all the doses tested, showed significant protection from ulcers induced by ibuprofen, ethanol and cold stress, with a maximum activity at 150 mg/kg. There was a significant increase in gastric tissue malondialdehyde levels in ethanol treated rats but these levels decreased following PA pretreatment. Moreover, pretreatment with PA significantly inhibited various effects of ethanol on gastric mucosa, such as, reduction in the concentration of nonprotein sulfhydryl groups, necrosis, erosions, congestion and hemorrhage. These results suggested that gastro-protective effect of PA could be mediated by its antioxidant activity and cytoprotection of gastric mucosa. 相似文献
63.
Treatment of low strength complex wastewater using an anaerobic baffled reactor (ABR) 总被引:2,自引:0,他引:2
Treatment of a low strength complex wastewater of chemical oxygen demand (COD) around 500mg/L was studied in a 10L capacity laboratory scale anaerobic baffled reactor (ABR). It was operated at hydraulic retention times (HRTs) of 20, 15, 10, 8 and 6h. Corresponding organic loading rates (OLRs) were 0.6, 0.8, 1.2, 1.5 and 2kg COD/m(3)d. At every HRT (or OLR), pseudo steady state (PSS) was achieved. Even at maximum OLR of 2kg COD/m(3)d, COD and biochemical oxygen demand (BOD) removals exceeded 88%. Removal of particulate fraction of organics was found to be greater than soluble fraction. Compartment-wise studies of various parameters revealed that if the OLR was larger, the number of initial compartments played significant role in the removal of organics. The values of volatile fatty acids (VFA) demonstrated that hydrolysis and acidogenesis were the main biochemical activities in the initial few compartments. Based on the tracer studies, dead space in the ABR was found to range from 23% to 34%. The flow pattern in the ABR was classified as intermediate between plug flow and perfectly mixed flows. Observations from scanning electron micrographs (SEM) also suggested that distinct phase separation takes place in an ABR. Study of organic and hydraulic shock loads revealed that ABR was capable of sustaining the type of shock loads generally experienced at a sewage treatment plant (STP). 相似文献
64.
Secretion of a platelet-derived growth factor homologue by rat alveolar macrophages exposed to particulates in vitro 总被引:2,自引:0,他引:2
M D Bauman A M Jetten J C Bonner R K Kumar R A Bennett A R Brody 《European journal of cell biology》1990,51(2):327-334
Lung macrophages secrete a homologue of platelet-derived growth factor (PDGF) which induces the proliferation of fibroblasts in vitro. In previous studies, we showed that such a PDGF homologue is produced by rat alveolar macrophages and that rat lung fibroblasts have specific receptors for the macrophage-derived PDGF. In this study, we demonstrate the biological and physicochemical properties of the growth factor, as well as the time-related production of this factor following macrophage activation in vitro by organic and inorganic particles. Alveolar macrophages (AMs) collected by saline lavage from the lungs of rats were cultured in serum-free Dulbecco's modified Eagle's medium (SF-DMEM) for varying periods of time up to 72 h. The SF-DMEM "conditioned" by the AMs was used to treat early passage rat lung fibroblasts (RLFs), which were rendered quiescent by culturing in 2% platelet-poor plasma (PPP). Alveolar macrophage conditioned media (AMCM) in the presence of PPP caused increases in the number of fibroblasts, the percent of labeled fibroblast nuclei and tritiated [3H]thymidine incorporation. AMCM alone caused no detectable changes in fibroblast growth rate. These results indicate that AMs release a "competence-like" growth factor. The AMs were left untreated or were exposed to opsonized zymosan, carbonyl iron spheres or chrysotile asbestos fibers. Macrophages attached to a plastic substrate spontaneously produced the factor, and subsequent addition of the organic and inorganic particles to the macrophage cultures significantly increased the fibroblast-stimulating activity of the AMCM. The growth factor was stable after concentration (100-fold), lyophilization and reconstitution.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
65.
Jyotirmay Mathur Narendra Kumar Bansal 《The International Journal of Life Cycle Assessment》1999,4(2):113-116
This analysis can be called energy accounting of solar water heating systems. Five types of solar water heating systems have
been considered. With the help of material balance, energy content has been found in these systems. Yearly output of systems
has been found by conducting transient simulations using hourly data of radiation and ambient temperature. Such analysis has
been done separately for one representative city of each of six climatic zones of India. The energy payback for India ranges
from 0.73 to 4.16 years for the thirty cases considered here. 相似文献
66.
Background
Bacteriocins are antimicrobial peptides that are produced by bacteria as a defense mechanism in complex environments. Identification and characterization of novel bacteriocins in novel strains of bacteria is one of the important fields in bacteriology.Methodology/Findings
The strain GI-9 was identified as Brevibacillus sp. by 16 S rRNA gene sequence analysis. The bacteriocin produced by strain GI-9, namely, laterosporulin was purified from supernatant of the culture grown under optimal conditions using hydrophobic interaction chromatography and reverse-phase HPLC. The bacteriocin was active against a wide range of Gram-positive and Gram-negative bacteria. MALDI-TOF experiments determined the precise molecular mass of the peptide to be of 5.6 kDa and N-terminal sequencing of the thermo-stable peptide revealed low similarity with existing antimicrobial peptides. The putative open reading frame (ORF) encoding laterosporulin and its surrounding genomic region was fished out from the draft genome sequence of GI-9. Sequence analysis of the putative bacteriocin gene did not show significant similarity to any reported bacteriocin producing genes in database.Conclusions
We have identified a bacteriocin producing strain GI-9, belonging to the genus Brevibacillus sp. Biochemical and genomic characterization of laterosporulin suggests it as a novel bacteriocin with broad spectrum antibacterial activity. 相似文献67.
68.
Satish Kumar Rajasekharan Tali Paz-Aviram Shmuel Galili Zipi Berkovich Ram Reifen Moshe Shemesh 《Microbial biotechnology》2021,14(4):1839-1846
Beneficial biofilms may confer effective adaptation to food matrices that assist bacteria in enduring hostile environmental conditions. The matrices, for instance, dietary fibres of various food products, might serve as a natural scaffold for bacterial cells to adhere and grow as biofilms. Here, we report on a unique interaction of Bacillus subtilis cells with the resistant starch fibresof chickpea milk (CPM), herein CPM fibres, along with the production of a reddish-pink pigment. Genetic analysis identified the pigment as pulcherrimin, and also revealed the involvement of Spo0A/SinI pathway in modulating the observed phenotypes. Besides, through successful colonization of the CPM fibres, the wild-type cells of B. subtilis displayed enhanced survivability and resilience to environmental stress, such as heat and in vitro gastrointestinal treatments. In total, we infer that the biofilm formation on CPM fibres is an adaptation response of B. subtilis for strategic survival. 相似文献
69.
Clinical decision is often difficult with chlorhexidine mouthwash. The use of antioxidant mouthwashes for the treatment of periodontal disease is in practise. Therefore, it is of interest to collect gleaned information on Antioxidant mouthwashes as periodontal therapy from known literature. Improvement in treatment using antioxidant mouthwashes is reported in several studies. The mouthwash with antioxidants has similar anti-gingivitis, antiplaque and antimicrobial effects as that of chlorhexidine mouthwash. 相似文献
70.
Singh Awtar Bali Aradhana Kumar Ashwani Yadav Rajender Kumar Minhas Paramjit Singh 《Journal of Plant Growth Regulation》2022,41(5):1989-1998
Journal of Plant Growth Regulation - Exogenous applications of plant growth regulators (PGRs) were evaluated for their effects on growth, physiological attributes, and yield of sodicity stressed... 相似文献