全文获取类型
收费全文 | 57861篇 |
免费 | 4593篇 |
国内免费 | 4493篇 |
专业分类
66947篇 |
出版年
2024年 | 142篇 |
2023年 | 789篇 |
2022年 | 1851篇 |
2021年 | 3044篇 |
2020年 | 2080篇 |
2019年 | 2501篇 |
2018年 | 2344篇 |
2017年 | 1805篇 |
2016年 | 2544篇 |
2015年 | 3627篇 |
2014年 | 4380篇 |
2013年 | 4436篇 |
2012年 | 5286篇 |
2011年 | 4762篇 |
2010年 | 2883篇 |
2009年 | 2598篇 |
2008年 | 2937篇 |
2007年 | 2634篇 |
2006年 | 2261篇 |
2005年 | 1887篇 |
2004年 | 1509篇 |
2003年 | 1420篇 |
2002年 | 1072篇 |
2001年 | 909篇 |
2000年 | 889篇 |
1999年 | 810篇 |
1998年 | 499篇 |
1997年 | 454篇 |
1996年 | 477篇 |
1995年 | 422篇 |
1994年 | 413篇 |
1993年 | 325篇 |
1992年 | 446篇 |
1991年 | 324篇 |
1990年 | 284篇 |
1989年 | 260篇 |
1988年 | 210篇 |
1987年 | 194篇 |
1986年 | 176篇 |
1985年 | 154篇 |
1984年 | 115篇 |
1983年 | 122篇 |
1982年 | 81篇 |
1981年 | 45篇 |
1980年 | 51篇 |
1979年 | 63篇 |
1976年 | 46篇 |
1974年 | 54篇 |
1973年 | 45篇 |
1972年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The inhibitory effect of two chemokine decoy receptors (CDRs), DARC and D6, on breast cancer metastasis is mainly due to their ability to sequester pro-malignant chemokines. We hypothesized that genetic variants in the DARC and CCBP2 (encoding D6) genes may be associated with breast cancer progression. In the present study, we evaluated the genetic contributions of DARC and CCBP2 to metastatic potential, indicated by lymph node metastasis (LNM). Ten single-nucleotide polymorphisms (SNPs) (potentially functional SNPs and block-based tagging SNPs) in DARC and CCBP2 were genotyped in 785 breast cancer patients who had negative lymph nodes and 678 patients with positive lymph nodes. Two non-synonymous SNPs, rs12075 (G42D) in DARC and rs2228468 (S373Y) in CCBP2, were observed to be associated with LNM in univariate analysis and remained significant after adjustment for conventional clinical risk factors, with odds ratios (ORs) of 0.54 (95% confidence interval [CI], 0.37 to 0.79) and 0.78 (95% CI, 0.62 to 0.98), respectively. Additional functional experiments revealed that both of these significant SNPs could affect metastasis of breast cancer in xenograft models by differentially altering the chemokine sequestration ability of their corresponding proteins. Furthermore, heterozygous GD genotype of G42D on human erythrocytes had a significantly stronger chemokine sequestration ability than homozygous GG of G42D ex vivo. Our data suggest that the genetic variants in the CDR genes are probably associated with the varied metastatic potential of breast cancer. The underlying mechanism, though it needs to be further investigated, may be that CDR variants could affect the chemokine sequestration ability of CDR proteins. 相似文献
992.
C H Yang J N Brown K D Kopple 《International journal of peptide and protein research》1979,14(1):12-20
The structures of 37 peptide crystals, containing 78 water-peptide hydrogen bonds and 77 other hydrogen bonds involving water, were surveyed to identify the geometry of peptide backbone hydration. In the sample, hydration of peptide carbonyl occurred more frequently than hydration of peptide N--H. The most probable value of the C'=O ... O water angle was near 138 degrees, considerably greater than the 120 degrees to the axis of a lone electron pair on the carbonyl oxygen. Associated water oxygens tended to be in the plane of the peptide bond, bui--H and Ci+1=O atoms, was common in glycine-containing cyclic hexapeptides. The distribution of angles between two hydrogen bonds at a single water molecule, as defined by the three nonhydrogen atoms involved, was centered near the tetrahedral angle. 相似文献
993.
Dispersed from a dry film into buffer (5 mM phosphate, 0.15 M NaCl, pH 7.4), the liponucleotide 1-β-d-arabinofuranosylcytosine 5′-diphosphate l-1,2-diacylglycerol (ara-CDPdiacylglycerol) spontaneously forms vesicles which are several microns in diameter and probably unilamellar. Their average size immediately begins to decrease, and after 2 h none can be seen in the light microscope. During 1–2 days in unstirred solutions at 25°C, the vesicles are transformed to spherical or nearly spherical micelles having an apparent partial specific volume of 0.835 ml·g?1, a maximum possible aggregation number of about 150, and an anhydrous radius of about 37 Å. The critical micelle concentration (CMC) is about 10 μM in buffer and 20 μM in distilled water, but micelle-monomer equilibration requires at least 1 week at a total concentration of 66 μM. This exceedingly slow equilibration is unique among reported detergents. The standard enthalpy and entropy of micellization are ?13 kJ·mol?1 and 87 J·mol?1·K?1, respectively. These values are within the range reported for other detergents. Sonication accelerates the vesicle-micelle transformation to 30 min. 相似文献
994.
Information structure facilitates communication between interlocutors by highlighting relevant information. It has previously been shown that information structure modulates the depth of semantic processing. Here we used event-related potentials to investigate whether information structure can modulate the depth of syntactic processing. In question-answer pairs, subtle (number agreement) or salient (phrase structure) syntactic violations were placed either in focus or out of focus through information structure marking. P600 effects to these violations reflect the depth of syntactic processing. For subtle violations, a P600 effect was observed in the focus condition, but not in the non-focus condition. For salient violations, comparable P600 effects were found in both conditions. These results indicate that information structure can modulate the depth of syntactic processing, but that this effect depends on the salience of the information. When subtle violations are not in focus, they are processed less elaborately. We label this phenomenon the Chomsky illusion. 相似文献
995.
996.
997.
998.
999.
The micropore structure is prerequisite for fast and durable endothelialization of artificial small diameter blood vessels (ASDBVs). Although some methods, such as salt leaching, coagulation, and electrospinning, have been developed to construct micropores for ASDBVs, the uncontrollability of the structure and the complicated procedures of the process are still the issues to be concerned about. In this study, a compact device based on the principle of centrifugal force is established and used to prepare polyurethane (PU) ASDBVs with micropore structures by blasting different porogens. It is found that the glass beads could construct micropores with regular round shape, uniform distribution, and controllable size (60–350 µm), which significantly improves the endothelialization of PU‐based ASDBVs, especially when the pore size is about 60 µm. This method is easy‐accessible and wide‐applicable, which provides a new pathway for the research and development of ASDBVs. 相似文献
1000.
Guocai Yao Wenliang Zhang Minglei Yang Huan Yang Jianbo Wang Haiyue Zhang Lai Wei Zhi Xie Weizhong Li 《基因组蛋白质组与生物信息学报(英文版)》2020,18(6):760-772
Microbes play important roles in human health and disease. The interaction between microbes and hosts is a reciprocal relationship, which remains largely under-explored. Current computational resources lack manually and consistently curated data to connect metagenomic data to pathogenic microbes, microbial core genes, and disease phenotypes. We developed the MicroPhenoDB database by manually curating and consistently integrating microbe-disease association data. MicroPhenoDB provides 5677 non-redundant associations between 1781 microbes and 542 human disease phenotypes across more than 22 human body sites. MicroPhenoDB also provides 696,934 relationships between 27,277 unique clade-specific core genes and 685 microbes. Disease phenotypes are classified and described using the Experimental Factor Ontology (EFO). A refined score model was developed to prioritize the associations based on evidential metrics. The sequence search option in MicroPhenoDB enables rapid identification of existing pathogenic microbes in samples without running the usual metagenomic data processing and assembly. MicroPhenoDB offers data browsing, searching, and visualization through user-friendly web interfaces and web service application programming interfaces. MicroPhenoDB is the first database platform to detail the relationships between pathogenic microbes, core genes, and disease phenotypes. It will accelerate metagenomic data analysis and assist studies in decoding microbes related to human diseases. MicroPhenoDB is available through http://www.liwzlab.cn/microphenodb and http://lilab2.sysu.edu.cn/microphenodb. 相似文献