全文获取类型
收费全文 | 1654篇 |
免费 | 92篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 75篇 |
2020年 | 42篇 |
2019年 | 42篇 |
2018年 | 81篇 |
2017年 | 48篇 |
2016年 | 64篇 |
2015年 | 91篇 |
2014年 | 110篇 |
2013年 | 101篇 |
2012年 | 115篇 |
2011年 | 93篇 |
2010年 | 56篇 |
2009年 | 64篇 |
2008年 | 85篇 |
2007年 | 85篇 |
2006年 | 59篇 |
2005年 | 58篇 |
2004年 | 61篇 |
2003年 | 46篇 |
2002年 | 32篇 |
2001年 | 26篇 |
2000年 | 37篇 |
1999年 | 18篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1748条查询结果,搜索用时 15 毫秒
991.
992.
Jun Xu Shuichi Nakamura Md. Shafiqul Islam Yijie Guo Kohei Ihara Rintaro Tomioka Mizuki Masuda Hiroshi Yoneyama Emiko Isogai 《PloS one》2016,11(4)
Mannose-binding lectin (MBL) is a key pattern recognition molecule in the lectin pathway of the complement system, an important component of innate immunity. MBL functions as an opsonin which enhances the sequential immune process such as phagocytosis. We here report an inhibitory effect of MBL on the motility of pathogenic bacteria, which occurs by affecting the energy source required for motility and the signaling pathway of chemotaxis. When Salmonella cells were treated with a physiological concentration of MBL, their motile fraction and free-swimming speed decreased. Rotation assays of a single flagellum showed that the flagellar rotation rate was significantly reduced by the addition of MBL. Measurements of the intracellular pH and membrane potential revealed that MBL affected a driving force for the Salmonella flagellum, the electrochemical potential difference of protons. We also found that MBL treatment increased the reversal frequency of Salmonella flagellar rotation, which interfered with the relative positive chemotaxis toward an attractive substrate. We thus propose that the motility inhibition effect of MBL may be secondarily involved in the attack against pathogens, potentially facilitating the primary role of MBL in the complement system. 相似文献
993.
Farzana Islam Rume Alessia Affuso Luigina Serrecchia Valeria Rondinone Viviana Manzulli Emanuele Campese Pietro Di Taranto Paritosh Kumar Biswas Chowdhury Rafiqul Ahsan Mahmuda Yasmin Antonio Fasanella Martin Hugh-Jones 《PloS one》2016,11(4)
In Bangladesh, anthrax, caused by the bacterium Bacillus anthracis, is considered an endemic disease affecting ruminants with sporadic zoonotic occurrences in humans. Due to the lack of knowledge about risks from an incorrect removal of infected carcasses, the disease is not properly monitored, and because of the socio-economic conditions, the situation is under-reported and under-diagnosed. For sensitive species, anthrax represents a fatal outcome with sudden death and sometimes bleeding from natural orifices. The most common source of infection for ruminants is ingestion of spores during grazing in contaminated pastures or through grass and water contaminated with anthrax spores. Domestic cattle, sheep and goats can also become infected through contaminated bone meal (used as feed) originating from anthrax-infected carcasses. The present investigation was conducted to isolate B. anthracis organisms from 169 samples (73 soil, 1 tissue, 4 bone and 91 bone meal samples) collected from 12 different districts of Bangladesh. The sampling was carried out from 2012 to 2015. Twelve samples resulted positive for B. anthracis. Biomolecular analyses were conducted starting from the Canonical Single Nucleotide Polymorphism (CanSNP) to analyze the phylogenetic origin of strains. The analysis of genotype, obtained through the Multiple Locus Variable Number Tandem Repeat Analysis (MLVA) with the analysis of 15 Variable Number Tandem Repeats (VNTR), demonstrated four different genotypes: two of them were previously identified in the district of Sirajganj. The sub-genotyping, conducted with Single Nucleotide Repeats analysis, revealed the presence of eight subgenotypes. The data of the present study concluded that there was no observed correlation between imported cattle feed and anthrax occurrence in Bangladesh and that the remarkable genetic variations of B. anthracis were found in the soil of numerous outbreaks in this country. 相似文献
994.
Kamrul Islam Md. Abu Sayeed Emran Hossen Farhana Khanam Richelle C. Charles Jason Andrews Edward T. Ryan Firdausi Qadri 《PLoS neglected tropical diseases》2016,10(4)
Background
There is an urgent need for an improved diagnostic assay for typhoid fever. In this current study, we compared the recently developed TPTest (Typhoid and Paratyphoid Test) with the Widal test, blood culture, and two commonly used commercially available kits, Tubex and Typhidot.Methodology
For analysis, we categorized 92 Bangladeshi patients with suspected enteric fever into four groups: S. Typhi bacteremic patients (n = 28); patients with a fourfold change in Widal test from day 0 to convalescent period (n = 7); patients with Widal titer ≥1:320 (n = 13) at either acute or convalescent stage of disease; and patients suspected with enteric fever, but with a negative blood culture and Widal titer (n = 44). We also tested healthy endemic zone controls (n = 20) and Bangladeshi patients with other febrile illnesses (n = 15). Sample size was based on convenience to facilitate preliminary analysis.Principle findings
Of 28 S. Typhi bacteremic patients, 28 (100%), 21 (75%) and 18 (64%) patients were positive by TPTest, Tubex and Typhidot, respectively. In healthy endemic zone controls, the TPTest method was negative in all, whereas Tubex and Typhidot were positive in 3 (15%) and 5 (25%), respectively. We then estimated sensitivity and specificity of all diagnostic tests using Bayesian latent class modeling. The sensitivity of TPTest, Tubex and Typhidot were estimated at 96.0% (95% CI: 87.1%-99.8%), 60.2% (95% CI: 49.3%-71.2%), and 59.6% (95% CI: 50.1%-69.3%), respectively. Specificity was estimated at 96.6% (90.7%-99.2%) for TPTest, 89.9% (79.6%-96.8%) for Tubex, and 80.0% (67.7%-89.7%) for Typhidot.Conclusion
These results suggest that the TPTest is highly sensitive and specific in diagnosing individuals with typhoid fever in a typhoid endemic setting, outperforming currently available and commonly used alternatives. 相似文献995.
Abdulbari Bener Muzeyyen Dogan Ahmed M. Almehdi Mohammed R. Islam Mahfoodh A. Darbool 《Aerobiologia》1999,15(1):57-63
This study aims at predicting Carbon monoxide (CO) emission rate as well as carboxyhaemoglobin (HbCO) levelsin Al-Ain City, United Arab Emirates (UAE). Also, several mathematical models are proposed for estimating both CO emission and HbCO levels. These models yield excellent agreements between observed and predicted data and can be easily coupled with atmospheric models. Carbon monoxide exposure from motor vehicles were measured over a 3-month period from September to December 1995 at three locations in the UAE. The study is based on a sample of 148 cars. The data revealed that the major characteristics of the cars surveyed were as follows: 69.5% of the cars were Japanese, 74.3% of the cars were 5 years old; 41% of the car was range rover or four-wheel-drive car, which indicates a higher proportion of powerful cars; 58.8% was used special fuel; 51.4% had regular maintenance for their cars and 52% of the cars had 4 cylinder engine capacity. Carboxyhaemoglobin (HbCO) levels in the UAE were predicted for 1-hour (1.720 ppm) and 8-hour (8.106 ppm) exposure times. Also, on an average driving of 80 km hr–1 per day, the CO emission rate was found to be 8.729 ppm. These findings indicate that the mean 1-hour and 8-hour Carboxyhaemoglobin (HbCO) levels do not exceed the permissible standards recommended by the WHO. Additionally, the results of stepwise multiple regression analyses revealed that the factors, such as, type of car, size of cylinder, size of car, and maintaining service of the car exerted the greatest influence on the amount and concentration of pollutant emission produced by car exhaust. 相似文献
996.
Mycelium of Arbuscular Mycorrhizal fungi (AMF) from different genera: form, function and detection 总被引:13,自引:2,他引:11
John C. Dodd Claire L. Boddington Alia Rodriguez Carmen Gonzalez-Chavez Irdika Mansur 《Plant and Soil》2000,226(2):131-151
It is often assumed that all species of arbuscular mycorrhizal fungi (AMF) have the same function because of the ubiquity
of the arbuscular mycorrhizal symbiosis and the fact that all AMF occupy the same plant/soil niche. Despite apparent differences
in the timing of evolutionary divergence and the morphological characteristics of AMF from the different genera, the majority
of studies on these fungi use only species of Glomus. There is increasing evidence, however, that the mechanisms involved in the establishment of a mycorrhiza may differ for
species and genera of AMF and influence their subsequent function. The aim of this paper is to highlight the diversity in
the form and function of AMF from different genera, knowledge of which is vital in understanding their ecological roles. Potential
use of biochemical and molecular approaches to detect AMF in planta and ex planta is also discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
997.
Mita Varghese Cameron Griffin Simin Abrishami Leila Eter Nicholas Lanzetta Layla Hak Jeremy Clemente Devyani Agarwal Arianna Lerner Maria Westerhoff Ravi Patel Emily Bowers Mohammed Islam Perla Subbaiah Kanakadurga Singer 《The Journal of biological chemistry》2021,297(5)
Men have a statistically higher risk of metabolic and cardiovascular disease than premenopausal women, but the mechanisms mediating these differences are elusive. Chronic inflammation during obesity contributes to disease risk and is significantly more robust in males. Prior work demonstrated that compared with obese males, obese females have reduced proinflammatory adipose tissue macrophages (ATMs). Given the paucity of data on how sex hormones contribute to macrophage responses in obesity, we sought to understand the role of sex hormones in promoting obesity-induced myeloid inflammation. We used gonadectomy, estrogen receptor–deficient alpha chimeras, and androgen-insensitive mice to model sex hormone deficiency. These models were evaluated in diet-induced obesity conditions (high-fat diet [HFD]) and in vitro myeloid assays. We found that ovariectomy increased weight gain and adiposity. Ovariectomized females had increased ATMs and bone marrow myeloid colonies compared with sham-gonadectomized females. In addition, castrated males exposed to HFD had improved glucose tolerance, insulin sensitivity, and adiposity with fewer Ly6chi monocytes and bone marrow myeloid colonies compared with sham-gonadectomized males, although local adipose inflammation was enhanced. Similar findings were observed in androgen-insensitive mice; however, these mice had fewer CD11c+ ATMs, implying a developmental role for androgens in myelopoiesis and adipose inflammation. We concluded that gonadectomy results in convergence of metabolic and inflammatory responses to HFD between the sexes, and that myeloid estrogen receptor alpha contributes minimally to diet-induced inflammatory responses, whereas loss of androgen-receptor signaling improves metabolic and inflammatory outcomes. These studies demonstrate that sex hormones play a critical role in sex differences in obesity, metabolic dysfunction, and myeloid inflammation. 相似文献
998.
Margarita Elvira-Recuenco Eugenia Iturritxa Juan Majada Ricardo Alia Rosa Raposo 《PloS one》2014,9(12)
There is a concern on how emerging pests and diseases will affect the distribution range and adaptability of their host species, especially due to different conditions derived from climate change and growing globalization. Fusarium circinatum, which causes pitch canker disease in Pinus species, is an exotic pathogen of recent introduction in Spain that threatens its maritime pine (P. pinaster) stands. To predict the impact this disease will have on the species, we examine host resistance traits and their genetic architecture. Resistance phenotyping was done in a clonal provenance/progeny trial, using three-year-old cuttings artificially inoculated with the pathogen and maintained under controlled environmental conditions. A total number of 670 ramets were assessed, distributed in 10 populations, with a total of 47 families, 2 to 5 half-sibs per family, and 3–7 ramets per clone. High genetic variation was found at the three hierarchical levels studied: population, family and clone, being both additive and non-additive effects important. Narrow-sense and broad-sense heritability estimates were relatively high, with respective values of 0.43–0.58 and 0.51–0.8, depending on the resistance traits measured (lesion length, lesion length rate, time to wilting, and survival). These values suggest the species'' high capacity of evolutionary response to the F. circinatum pathogen. A population originated in Northern Spain was the most resistant, while another from Morocco was the most susceptible. The total number of plants that did not show lesion development or presented a small lesion (length<30 mm) was 224 out of 670, indicating a high proportion of resistant trees in the offspring within the analyzed populations. We found large differences among populations and considerable genetic variation within populations, which should allow, through natural or artificial selection, the successful adaptation of maritime pine to pitch canker disease. 相似文献
999.
A metamaterial-embedded planar inverted-F antenna (PIFA) is proposed in this study for cellular phone applications. A dual-band PIFA is designed to operate both GSM 900 MHz and DCS 1800 MHz. The ground plane of a conventional PIFA is modified using a planar one-dimensional metamaterial array. The investigation is performed using the Finite Integration Technique (FIT) of CST Microwave Studio. The performance of the developed antenna was measured in an anechoic chamber. The specific absorption rate (SAR) values are calculated considering two different holding positions: cheek and tilt. The SAR values are measured using COMOSAR measurement system. Good agreement is observed between the simulated and measured data. The results indicate that the proposed metamaterial-embedded antenna produces significantly lower SAR in the human head compared to the conventional PIFA. Moreover, the modified antenna substrate leads to slight improvement of the antenna performances. 相似文献
1000.
Humanization of fibroblast growth factor 1 single‐chain antibody and validation for its antitumorigenic efficacy in breast cancer and glioma cells 下载免费PDF全文
Xiao‐Xiao He Shuang Du Shi‐Qian Gao Jing‐Ying Chen Ran‐Juan Cao Zhen‐Kai Xing Alia Rizvi Syeda Kazim Hua‐Li Yu Qing‐Chuan Zheng Xiao‐Juan Zhu 《Journal of cellular and molecular medicine》2018,22(6):3259-3263
Single‐chain variable fragment (scFv) antibodies are the smallest immunoglobulins with high antigen‐binding affinity. We have previously reported that fibroblast growth factor 1 played pivotal roles in cancer development and generated a mouse scFv (mscFv1C9) could effectively prohibit cancer cell proliferation in vitro and in vivo. Here, we further humanized this scFv (hscFv1C9) using a structure‐guided complementarity determining region grafting strategy. The purified hscFv1C9 maintained similar antigen‐binding affinity and specificity as mscFv1C9, and it was capable of inhibiting growth of different tumours in vitro and in vivo. These data strongly suggested that hscFv1C9 has antitumour potentials. 相似文献