全文获取类型
收费全文 | 9463篇 |
免费 | 796篇 |
国内免费 | 7篇 |
专业分类
10266篇 |
出版年
2023年 | 33篇 |
2022年 | 105篇 |
2021年 | 162篇 |
2020年 | 92篇 |
2019年 | 165篇 |
2018年 | 207篇 |
2017年 | 158篇 |
2016年 | 323篇 |
2015年 | 485篇 |
2014年 | 525篇 |
2013年 | 549篇 |
2012年 | 720篇 |
2011年 | 728篇 |
2010年 | 458篇 |
2009年 | 407篇 |
2008年 | 545篇 |
2007年 | 523篇 |
2006年 | 476篇 |
2005年 | 474篇 |
2004年 | 450篇 |
2003年 | 409篇 |
2002年 | 352篇 |
2001年 | 314篇 |
2000年 | 249篇 |
1999年 | 224篇 |
1998年 | 84篇 |
1997年 | 82篇 |
1996年 | 59篇 |
1995年 | 63篇 |
1994年 | 39篇 |
1993年 | 28篇 |
1992年 | 79篇 |
1991年 | 83篇 |
1990年 | 50篇 |
1989年 | 54篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1979年 | 19篇 |
1978年 | 22篇 |
1977年 | 23篇 |
1976年 | 24篇 |
1974年 | 24篇 |
1973年 | 19篇 |
1971年 | 20篇 |
1970年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
961.
Yang HJ Jin KN Park YK Hong SC Bae JM Lee SH Choi HS Hwang HS Chung YB Lee NS Nam HW 《The Korean journal of parasitology》2000,38(2):91-93
This study was performed to evaluate the epidemiological status of toxoplasmosis among the residents of Cheju island. The sera of local students from 18 high schools (boys 2110, girls 2460) and those of adults (474 admitted to Cheju Chungang General Hospital) were collected and checked for the IgG antibody titers against Toxoplasma gondii. Serum samples collected from both the students and adults showed sero-positive rate of 5.5% and 12.9%, respectively. Although the rates were not significantly different between the sexes (5.4% for the boys and 5.5% for the girls attending school), the geographical difference showed a significant difference between the urban (4.6-6.9%) and rural areas (5.6-8.8%) (p < 0.05). Based on the high positive rates, it should be necessary to control toxoplasmosis in Cheju island. 相似文献
962.
Ren-Hua Chung Wei-Yun Tsai Chen-Yu Kang Po-Ju Yao Hui-Ju Tsai Chia-Hsiang Chen 《PLoS computational biology》2016,12(6)
In disease studies, family-based designs have become an attractive approach to analyzing next-generation sequencing (NGS) data for the identification of rare mutations enriched in families. Substantial research effort has been devoted to developing pipelines for automating sequence alignment, variant calling, and annotation. However, fewer pipelines have been designed specifically for disease studies. Most of the current analysis pipelines for family-based disease studies using NGS data focus on a specific function, such as identifying variants with Mendelian inheritance or identifying shared chromosomal regions among affected family members. Consequently, some other useful family-based analysis tools, such as imputation, linkage, and association tools, have yet to be integrated and automated. We developed FamPipe, a comprehensive analysis pipeline, which includes several family-specific analysis modules, including the identification of shared chromosomal regions among affected family members, prioritizing variants assuming a disease model, imputation of untyped variants, and linkage and association tests. We used simulation studies to compare properties of some modules implemented in FamPipe, and based on the results, we provided suggestions for the selection of modules to achieve an optimal analysis strategy. The pipeline is under the GNU GPL License and can be downloaded for free at http://fampipe.sourceforge.net.
This is a PLOS Computational Biology Software article.相似文献
963.
Burdge GC Slater-Jefferies JL Grant RA Chung WS West AL Lillycrop KA Hanson MA Calder PC 《Prostaglandins, leukotrienes, and essential fatty acids》2008,78(1):73-79
The aim of the study was to investigate whether the protein and folic acid content of the maternal diet and the sex of the offspring alter the polyunsaturated fatty acid content of hepatic phospholipids and triacylglycerol (TAG). Pregnant rats were fed diets containing 18% or 9% protein with either 1 or 5mg/kg folic acid. Maternal diet did not alter hepatic lipid composition in the adult offspring. Data from each maternal dietary group were combined and reanalysed. The proportion of 18:0, 20:4n-6 and 22:6n-3 in liver phospholipids was higher in females than in males, while hepatic TAG composition did not differ between sexes. Delta5 Desaturase expression was higher in females than in males. Neither Delta5 nor Delta6 desaturase expression was related to polyunsaturated fatty acid concentrations. These results suggest that sex differences in liver phospholipid fatty acid composition may reflect primary differences in the specificity of phospholipid biosynthesis. 相似文献
964.
Sung Eun Sim Yoon Hee Chung Ji Hoon Jeong Sin Weon Yun Hyoun-Sub Lim Daejin Kim Sung Su Kim Won Bok Lee Choong Ik Cha 《Journal of molecular histology》2009,40(2):157-163
In the present study, we performed immunohistochemical studies to investigate the changes of insulin-like growth factor binding
protein 2 (IGFBP2) in the central nervous system of SOD1G93A mutant transgenic mice as an in vivo model of amyotrophic lateral sclerosis (ALS). Decreased immunoreactivity for IGFBP2
was observed in the cerebral cortex, hippocampus and brainstem of SOD1G93A transgenic mice. In the cerebral cortex, the number of IGFBP2-positive cells was decreased in the somatomotor area, somatosensory
area, auditory area, visual area, entorhinal area, piriform area and prefrontal area. In the hippocampal formation, IGFBP2
immunoreactivity was significantly decreased in the CA1-3 areas and the dentate gyrus. In the brainstem, few IGFBP2-immunoreactive
cells were observed in the medullary and pontine reticular formation, vestibular nucleus, trigeminal motor nucleus, facial
nucleus, hypoglossal nucleus and raphe nucleus. In the spinal cord, IGFBP2 immunoreactivity was not significantly decreased
in SOD1G93A transgenic mice. This study showing decreased IGFBP2 in different brain regions of SOD1G93A transgenic mice may provide clues for understanding differential susceptibility of neural structures in ALS.
S. E. Sim and Y. H. Chung have contributed equally to this work. 相似文献
965.
Hsin-Wei Chen Hui-Mei Hu Szu-Hsien Wu Chen-Yi Chiang Yu-Ju Hsiao Chia-Kai Wu Chun-Hsiang Hsieh Han-Hsuan Chung Pele Chong Chih-Hsiang Leng Chien-Hsiung Pan 《PloS one》2015,10(12)
Dengue is the leading cause of mosquito-borne viral infections and no vaccine is available now. Envelope protein domain III (ED3) is the major target for the binding of dengue virus neutralizing antibodies; however, the ED3-specifc T-cell response is less well understood. To investigate the T-cell responses to four serotypes of dengue virus (DENV-1 to 4), we immunized mice using either a tetravalent ED3-based DNA or protein vaccine, or combined both as a DNA prime-protein boost strategy (prime-boost). A significant serotype-dependent IFN-γ or IL-4 response was observed in mice immunized with either the DNA or protein vaccine. The IFN-γ response was dominant to DENV-1 to 3, whereas the IL-4 response was dominant to DENV-4. Although the similar IgG titers for the four serotypes were observed in mice immunized with the tetravalent vaccines, the neutralizing antibody titers varied and followed the order of 2 = 3>1>4. Interestingly, the lower IFN-γ response to DENV-4 is attributable to the immunodominance change between two CD4+ T-cell epitopes; one T-cell epitope located at E349-363 of DENV-1 to 3 was more immunogenic than the DENV-4 epitope E313-327. Despite DENV-4 specific IFN-γ responses were suppressed by immunodominance change, either DENV-4-specific IFN-γ or neutralizing antibody responses were still recalled after DENV-4 challenge and contributed to virus clearance. Immunization with the prime-boost elicited both IFN-γ and neutralizing antibody responses and provided better protection than either DNA or protein immunization. Our findings shed light on how ED3-based tetravalent dengue vaccines sharpen host CD4 T-cell responses and contribute to protection against dengue virus. 相似文献
966.
Endy Chung R.Kent Rhodes Edward J. Miller 《Biochemical and biophysical research communications》1976,71(4):1167-1174
Fractionation of pepsin-solubilized collagens from several human tissues has shown that substantial quantities of collagen-like protein remain in solution under conditions leading to the precipitation of Type I, II, and III collagens. Characterization of the more soluble collagens has led to the isolation of three unique collagenous components each of which exhibit compositional features indicative of their origin from basement membranes. One of these has an apparent molecular weight of 55,000 daltons and appears to originate in endothelial basement membranes. The other two components (A chain and B chain) are somewhat larger than collagen α chains and appear to be derived from the collagen of epithelial and smooth muscle basement membranes, respectively. 相似文献
967.
Siu Keung Tse Shein Chung Chow Qingshu Lu Dennis Cosmatos 《Biometrical journal. Biometrische Zeitschrift》2009,51(1):159-170
The problem of testing treatment difference in the occurrence of a safety parameter in a randomized parallel‐group comparative clinical trial under the assumption that the number of occurrence follows a zero‐inflated Poisson (ZIP) distribution is considered. Likelihood ratio tests (LRT) for homogeneity of two ZIP populations are derived under the hypotheses that (i) there is no difference in inflation parameters, (ii) there is no difference in non‐zero means; and (iii) there is no difference in both inflation parameters and non‐zero means. Approximate formulas for sample size calculation are also obtained for achieving a desired power for detecting a clinically meaningful difference under the corresponding alternative hypotheses. An example concerning the assessment of the gastrointestinal (GI) safety in terms of the number of erosion counts of a newly developed compound for the treatment of osteoarthritis and rheumatoid arthritis is given for illustration purpose (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
968.
Lithium‐Ion Batteries: Excellent Compatibility of Solvate Ionic Liquids with Sulfide Solid Electrolytes: Toward Favorable Ionic Contacts in Bulk‐Type All‐Solid‐State Lithium‐Ion Batteries (Adv. Energy Mater. 22/2015) 下载免费PDF全文
969.
Hack-Lyoung Kim Kwang Nam Jin Jae-Bin Seo Young Ho Choi Woo-Young Chung Sang-Hyun Kim Myung-A Kim Joo-Hee Zo 《PloS one》2015,10(4)
The aim of this study was to investigate whether brachial-ankle pulse wave velocity (baPWV) is associated with the severity of coronary artery disease (CAD) assessed by coronary computed tomography angiography (CCTA), and to evaluate baPWV as a predictor of obstructive CAD on CCTA. A total of 470 patients who underwent both baPWV and CCTA were included. We evaluated stenosis degree and plaque characteristics on CCTA. To estimate the severity of CAD, we calculated the number of segment with plaque (segment involvement score; SIS), stenosis degree-weighted plaque score (segment stenosis score; SSS), and coronary artery calcium score (CACS). The mean baPWV was 1,485 ± 315 cm/s (range, 935-3,175 cm/s). Non-obstructive (stenosis < 50%) and obstructive (stenosis ≥ 50%) CAD was found in 129 patients (27.4%) and 144 (30.6%), respectively. baPWV in patients with obstructive CAD was higher than that of patients with non-obstructive (1,680 ± 396 cm/s versus 1,477 ± 244 cm/s, P < 0.001) or no CAD (1,680 ± 396 cm/s versus ± 196 1,389 cm/s, P < 0.001). baPWV showed significant correlation with SSS (r = 0.429, P < 0.001), SIS (r = 0.395, P < 0.001), CACS (r 0.346, P < 0.001), and the number of segment with non-calcified plaque (r 0.092, P = 0.047), mixed plaque (r = 0.267, P < 0.001), and calcified plaque (r = 0.348, P < 0.001), respectively. The optimal baPWV cut-off value for the detection of obstructive CAD was 1,547 cm/s. baPWV ≥ 1,547 cm/s was independent predictor for the obstructive CAD. In conclusion, baPWV is well correlated with the severity of CAD evaluated by CCTA. baPWV has the potential to predict severity of coronary artery atherosclerosis. 相似文献
970.
MethodsThis is a cohort study of patients who were diagnosed with genotype-confirmed R544C-mutation CADASIL. Primary neurologic symptoms were recorded. Symptomatic strokes were defined as transient ischemic attack, ischemic strokes and hemorrhagic strokes. CMBs were defined as focal areas of round signal loss on T2*-weighted gradient echo planar images with a diameter of less than 10 mm. The locations of CMBs were divided into lobar, basal ganglia, thalamus, brain stem and cerebellum. Multiple logistic regressions were performed to identify the epidemiologic or vascular risk factors associated with symptomatic stroke in patients with CADASIL.ResultsAmong total of 51 subjects in this cohort, CMBs were present in 20 of 32 patients (64.5%) in the symptomatic stroke-group and in 8 of 19 patients (42.1%) in the non-stroke group (p = 0.16). CMBs were observed more frequently in the basal ganglia (p<0.001) and the cerebellum (p<0.018) in the symptomatic stoke group compared to the non-stroke group. The mean number of CMBs was significantly higher in the symptomatic stroke group (15.4±18.0 lesions per patients with CMBs) versus those without symptomatic stroke (3.3±3.0 lesions per patients with CMBs) (p = 0.003). Hypertension was an independent risk factor for symptomatic stroke in CADASIL (p = 0.014). It was independently associated with CMBs locations as basal ganglia (p = 0.016), thalamus (p = 0.010), brainstem (p = 0.044), and cerebellum (p = 0.049). However, It was not independently associated with CMBs on lobar lesion (p = 0.152).ConclusionsIn this study hypertension was an independent predictor of CMBs presence in specific brain locations, as well as symptomatic stroke in the CADASIL patients. The distribution and burden of CMBs might be a clinically useful marker for the risk of symptomatic stroke. However, further prospective studies on the relationship between CMBs distribution and symptomatic stroke are required in order to support these preliminary findings. 相似文献