全文获取类型
收费全文 | 4775篇 |
免费 | 434篇 |
国内免费 | 6篇 |
专业分类
5215篇 |
出版年
2022年 | 42篇 |
2021年 | 75篇 |
2020年 | 26篇 |
2019年 | 39篇 |
2018年 | 64篇 |
2017年 | 48篇 |
2016年 | 113篇 |
2015年 | 242篇 |
2014年 | 252篇 |
2013年 | 312篇 |
2012年 | 435篇 |
2011年 | 380篇 |
2010年 | 202篇 |
2009年 | 176篇 |
2008年 | 235篇 |
2007年 | 245篇 |
2006年 | 233篇 |
2005年 | 212篇 |
2004年 | 198篇 |
2003年 | 171篇 |
2002年 | 162篇 |
2001年 | 148篇 |
2000年 | 136篇 |
1999年 | 106篇 |
1998年 | 50篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 30篇 |
1993年 | 31篇 |
1992年 | 70篇 |
1991年 | 70篇 |
1990年 | 59篇 |
1989年 | 61篇 |
1988年 | 59篇 |
1987年 | 60篇 |
1986年 | 37篇 |
1985年 | 20篇 |
1984年 | 31篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1979年 | 26篇 |
1978年 | 23篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1974年 | 23篇 |
1973年 | 22篇 |
1972年 | 11篇 |
排序方式: 共有5215条查询结果,搜索用时 15 毫秒
961.
Ching-Yi Lin Chi-Han Li Nu-Man Tsai Wei-Tung Hsu Fang-Hsing Chiang Chia-Ching Chang 《Biochemical and biophysical research communications》2009,388(2):283-289
Helicobacter pylori heat shock protein 60 (HpHsp60) was first identified as an adhesion molecule associated with H. pylori infection. Here we have analyzed the structure of HpHsp60 via amino acid BLAST, circular dichroism, and electrophoresis and the results indicate that most recombinant HpHsp60 molecules exist as dimers or tetramers, which is quite different from Escherichia coli Hsp60. Treatment of human monocytic cells THP-1 with HpHsp60 was found to up-regulate a panel of cytokines including IL-1α, IL-8, IL-10, IFN-γ, TNF-α, TGF-β, GRO, and RANTES. Carboxymethylated HpHsp60 molecules with a switched oligomeric status were able to further enhance NF-κB-mediated IL-8 and TNF-α secretion in THP-1 cells compared to unmodified HpHsp60 molecules. These results indicated that the oligomeric status of HpHsp60s might have an important role in regulating host inflammation and thus help facilitate H. pylori persistent infection. 相似文献
962.
Shih-Wei Yang Yun-Shien Lee Tai-An Chen Chang-Jer Wu Chi-Neu Tsai 《Cancer epidemiology》2009,33(2):118-122
Background: Oral leukoplakia is considered as a premalignant lesion for the development of oral squamous cell carcinoma (OSCC); several risks factors have been reported to contribute to this step-wise carcinogenesis; including human papillomavirus (HPV). Nevertheless, few reports have analyzed both the HPV status and the genotype in a single individual who develops OSCC from pre-existing oral leukoplakia. In this study, we surveyed the HPV status, genotype and clinicopathological risk factors in cases of malignant transformation from pre-existing oral leukoplakia. Methods: HPV genomic DNA was detected by PCR (MY09/MY11 in conjugation with nested primer-GP05+/GP06+) from paraffin sections, and the genotype was determined by direct DNA sequencing. Fisher's exact test and logistic regression were used to analyze risk factors for malignant transformation of oral cavity leukoplakia. Results: One hundred and sixty-seven patients with oral leukoplakia were enrolled; including 12 who had malignant transformation from the pre-existing oral leukoplakia. HPV prevalence was 22.8% in cases with oral leukoplakia. The risk factor associated with malignant transformation was recurrence of leukoplakia after treatment (p = 0.03), nevertheless, HPV status was not statistically significant by logistic regression analysis. Among these 12 patients with malignant transformation from pre-existing oral leukoplakia, the status or genotype of HPV was chaotic; the oral habits of these patients might contribute to malignant transformation. Conclusions: Our data suggest that HPV in oral leukoplakia is no prognostic indicator of malignant transformation. 相似文献
963.
964.
Extension of the core map of common bean with EST-SSR,RGA, AFLP,and putative functional markers 总被引:1,自引:0,他引:1
Luiz Ricardo Hanai Luciane Santini Luis Eduardo Aranha Camargo Maria Helena Pelegrinelli Fungaro Paul Gepts Siu Mui Tsai Maria Lucia Carneiro Vieira 《Molecular breeding : new strategies in plant improvement》2010,25(1):25-45
Microsatellites and gene-derived markers are still underrepresented in the core molecular linkage map of common bean compared
to other types of markers. In order to increase the density of the core map, a set of new markers were developed and mapped
onto the RIL population derived from the ‘BAT93’ × ‘Jalo EEP558’ cross. The EST-SSR markers were first characterized using
a set of 24 bean inbred lines. On average, the polymorphism information content was 0.40 and the mean number of alleles per
locus was 2.7. In addition, AFLP and RGA markers based on the NBS-profiling method were developed and a subset of the mapped
RGA was sequenced. With the integration of 282 new markers into the common bean core map, we were able to place markers with
putative known function in some existing gaps including regions with QTL for resistance to anthracnose and rust. The distribution
of the markers over 11 linkage groups is discussed and a newer version of the common bean core linkage map is proposed. 相似文献
965.
You Fu Pan Ing-Marie Viklund Heng Hang Tsai Sven Pettersson Ichiro N. Maruyama 《International journal of biological sciences》2010,6(2):163-171
Ulcerative colitis (UC) is one of the major forms of inflammatory bowel disease with unknown cause. A molecular marker, WAFL, has recently been found to be up-regulated in the inflamed colonic mucosa of UC patients. Towards understanding biological function of WAFL, we analyzed proteins interacting with WAFL in HEK-293 cells by immunoprecipitation and mass spectrometry. Among four proteins found to specifically interact with WAFL, both KIAA0196 and KIAA1033 bind to α-appendage of the adaptor protein complex 2 (AP2), which acts as an interaction hub for accessory proteins in endocytosis mediated by clathrin-coated vesicle (CCV). The specific interaction between WAFL and KIAA0196 was also confirmed in human colorectal carcinoma HCT-116 cells by co-immunoprecipitation with specific antibodies. Meta-analyses of the databases of expressed genes suggest that the three genes are co-expressed in many tissues and cell types, and that their molecular function may be classified in the category of ''membrane traffic protein''. Therefore, these results suggest that WAFL may play an important role in endocytosis and subsequent membrane trafficking by interacting with AP2 through KIAA0196 and KIAA1033. 相似文献
966.
Dawn M Simon Larry W Tsai Edward P Ingenito Barry C Starcher Thomas J Mariani 《Respiratory research》2010,11(1):69
Background
Peroxisome proliferator-activated receptor (PPAR)-γ is a nuclear hormone receptor that regulates gene expression, cell proliferation and differentiation. We previously described airway epithelial cell PPARγ deficient mice that develop airspace enlargement with decreased tissue resistance and increased lung volumes. We sought to understand the impact of airspace enlargement in conditionally targeted mice upon the physio-mechanical properties of the lung.Methods
We measured elastic recoil and its determinants, including tissue structure and surface forces. We measured alveolar number using radial alveolar counts, and airspace sizes and their distribution using computer-assisted morphometry.Results
Air vs. saline-filled pressure volume profiles demonstrated loss of lung elastic recoil in targeted mice that was contributed by both tissue components and surface tension, but was proportional to lung volume. There were no significant differences in surfactant quantity/function nor in elastin and collagen content between targeted animals and littermate controls. Importantly, radial alveolar counts were significantly reduced in the targeted animals and at 8 weeks of age there were 18% fewer alveoli with 32% more alveolar ducts. Additionally, the alveolar ducts were 19% larger in the targeted animals.Conclusions
Our data suggest that the functional abnormalities, including loss of recoil are secondary to altered force transmission due to differences in the structure of alveolar ducts, rather than changes in surfactant function or elastin or collagen content. These data further define the nature of abnormal lung maturation in the absence of airway epithelial cell PPARγ and identify a putative genetic determinant of dysanapsis, which may serve as a precursor to chronic lung disease. 相似文献967.
968.
The objective of this work was to study the chemical and physical characterization of eggshell and eggshell membrane particles prepared from the hen eggshell waste. Under the characterization measurements investigated, it was found that the pore structures of the two biomaterials belong to a typical Type II, indicating that they should be basically characteristic of nonporous materials or materials with macropores or open voids. Further, the chemical composition of the resulting eggshell particle was strongly associated with the presence of carbonate minerals from the Fourier transform infrared (FTIR) spectra. In contrast to the resulting eggshell membrane particle, the presence of functional groups of amines and amides was observable because of its chemical composition of fibrous proteins. From the isotherm data of methylene blue at 25 degrees C, the Freundlich model yielded a somewhat better fit than the Langmuir model. The adsorption isotherms revealed the eggshell biosorbents could only uptake the basic dye of less than 1.0mg/g in aqueous medium, which was attributed to their poor pore properties. 相似文献
969.
Thermophilic composting of food waste 总被引:3,自引:0,他引:3
A laboratory reactor was designed to study the effects of operating parameters (air suction rate, seeding and agitation) on the composting process of a synthetic food waste made of dog food. Experimental results showed that the synthetic food waste could be composted within 4 days and the final compost passed the maturity tests. In most cases except those with 32% of seeding, the process involved two major stages of composting. The two peak temperatures between 50 and 60 degrees C occurred at 8-12th hour and 50-65th hour, respectively. Operating parameters that converted the most volatile solids and carbons in the feedstock were as follows: 1.6 l air/kg dry solid-min of air suction rate, 32% of seeding and 50% of agitation time. 相似文献
970.
Tsai YM Chou SW Lin YC Hou CW Hung KC Kung HW Lin TW Chen SM Lin CY Kuo CH 《Life sciences》2006,79(13):1281-1286
Serum dehydroepiandrosterone sulfate (DHEA-S) concentration is known to be associated with the whole-body insulin sensitivity. The main purpose of the study was to investigate the effect of resistance exercise on DHEA-S concentration during a 72 h post-exercise recovery, and its relation to glucose tolerance and insulin sensitivity. Morning fasted serum samples was obtained from 19 male volunteers (aged 21.1+/-0.4 years) 24 h before the onset of exercise and 24 h, 48 h, and 72 h following exercise for measurements of DHEA-S, cortisol, and TNF-alpha. Oral glucose tolerance test (OGTT) and insulin response were determined 24 h before and 48 h after exercise. We found that resistance exercise causes a delayed suppression in serum DHEA-S levels during recovery (48 h and 72 h). This exercise challenge did not affect glucose tolerance, but insulin response during OGTT was significantly elevated. The increased insulin level was not associated with serum levels of cortisol and TNF-alpha. In conclusion, the present study found that resistance exercise has a DHEA-S lowering effect that persisted for 72 h. This change could be related to the elevated insulin concentrations during OGTT. 相似文献