全文获取类型
收费全文 | 35645篇 |
免费 | 3064篇 |
国内免费 | 19篇 |
专业分类
38728篇 |
出版年
2023年 | 112篇 |
2022年 | 317篇 |
2021年 | 593篇 |
2020年 | 359篇 |
2019年 | 475篇 |
2018年 | 595篇 |
2017年 | 523篇 |
2016年 | 924篇 |
2015年 | 1563篇 |
2014年 | 1695篇 |
2013年 | 2068篇 |
2012年 | 2805篇 |
2011年 | 2870篇 |
2010年 | 1783篇 |
2009年 | 1675篇 |
2008年 | 2357篇 |
2007年 | 2415篇 |
2006年 | 2256篇 |
2005年 | 2102篇 |
2004年 | 2084篇 |
2003年 | 1925篇 |
2002年 | 1868篇 |
2001年 | 405篇 |
2000年 | 272篇 |
1999年 | 404篇 |
1998年 | 474篇 |
1997年 | 340篇 |
1996年 | 305篇 |
1995年 | 272篇 |
1994年 | 238篇 |
1993年 | 257篇 |
1992年 | 231篇 |
1991年 | 175篇 |
1990年 | 155篇 |
1989年 | 171篇 |
1988年 | 139篇 |
1987年 | 125篇 |
1986年 | 100篇 |
1985年 | 136篇 |
1984年 | 162篇 |
1983年 | 111篇 |
1982年 | 127篇 |
1981年 | 114篇 |
1980年 | 96篇 |
1979年 | 61篇 |
1978年 | 74篇 |
1977年 | 65篇 |
1976年 | 45篇 |
1974年 | 37篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Elise P. Salerno Sofia M. Shea Walter C. Olson Gina R. Petroni Mark E. Smolkin Chantel McSkimming Kimberly A. Chianese-Bullock Craig L. Slingluff Jr. 《Cancer immunology, immunotherapy : CII》2013,62(7):1149-1159
We conducted a randomized clinical trial in 45 patients with resected AJCC stage IIB-IV melanoma to characterize cellular and molecular events at sites of immunization with incomplete Freund’s adjuvant (IFA) alone, or a melanoma vaccine in IFA. At a primary vaccine site, all patients received a multi-peptide melanoma vaccine in IFA. At a replicate vaccine site, which was biopsied, group 1 received IFA only; group 2 received vaccine in IFA. Lymphocytes isolated from replicate vaccine site microenvironments (VSME) were compared to time-matched peripheral blood mononuclear cells (PBMC) in ELISpot and flow cytometry assays. Compared to PBMC, the VSME had fewer naïve and greater proportions of effector memory CD8+ T cells (TCD8). The vast majority of TCD8 within the VSME were activated (CD69+), with a concentration of antigen-specific (tetramerpos) cells in the VSME, particularly in vaccine sites with peptide (group 2). CXCR3+ lymphocytes were concentrated in the VSME of all patients, suggesting IFA-induced chemokine recruitment. TCD8 expression of retention integrins αEβ7 and α1β1 was elevated in VSME, with the highest levels observed in antigen-specific cells in VSME containing peptide (group 2). TCD8 retained in the VSME of both groups were strikingly dysfunctional, with minimal IFN-γ production in response to peptide stimulation and few tetramerpos cells producing IFN-γ. These data suggest that vaccine-induced selective retention and dysfunction of antigen-specific TCD8 within VSME may represent a significant mechanism underlying transient immune responses and low clinical response rates to peptide vaccines administered in IFA. 相似文献
932.
Noushin Niknafs Dewey Kim RyangGuk Kim Mark Diekhans Michael Ryan Peter D. Stenson David N. Cooper Rachel Karchin 《Human genetics》2013,132(11):1235-1243
Mutation position imaging toolbox (MuPIT) interactive is a browser-based application for single-nucleotide variants (SNVs), which automatically maps the genomic coordinates of SNVs onto the coordinates of available three-dimensional (3D) protein structures. The application is designed for interactive browser-based visualization of the putative functional relevance of SNVs by biologists who are not necessarily experts either in bioinformatics or protein structure. Users may submit batches of several thousand SNVs and review all protein structures that cover the SNVs, including available functional annotations such as binding sites, mutagenesis experiments, and common polymorphisms. Multiple SNVs may be mapped onto each structure, enabling 3D visualization of SNV clusters and their relationship to functionally annotated positions. We illustrate the utility of MuPIT interactive in rationalizing the impact of selected polymorphisms in the PharmGKB database, somatic mutations identified in the Cancer Genome Atlas study of invasive breast carcinomas, and rare variants identified in the exome sequencing project. MuPIT interactive is freely available for non-profit use at http://mupit.icm.jhu.edu. 相似文献
933.
l-Carnitine is a naturally occurring substance required in mammalian energy metabolism that functions by facilitating long-chain fatty acid entry into cellular mitochondria, thereby delivering substrate for oxidation and subsequent energy production. It has been purposed that l-carnitine may improve and preserve cognitive performance, and may lead to better cognitive aging through the life span, and several controlled human clinical trials with l-carnitine support the hypothesis that this substance has the ability to improve cognitive function. We further hypothesized that, since l-carnitine is an important co-factor of mammalian mitochondrial energy metabolism, acute administration of l-carnitine to human tissue culture cells should result in detectable increases in mitochondrial function. Cultures of SH-SY-5Y human neuroblastoma and 1321N1 human astrocytoma cells grown in 96-well cell culture plates were acutely administered l-carnitine hydrochloride, and then, mitochondrial function was assayed using the colorimetric 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt cell assay kit in a VERSAmax tunable microplate reader. Significant increases in mitochondrial function were observed when human neuroblastoma or human astrocytoma cells were exposed to 100 nM (20 μg l-carnitine hydrochloride/L) to 100 μM (20 mg l-carnitine hydrochloride/L) concentrations of l-carnitine hydrochloride in comparison to unexposed cells, whereas no significant positive effects were observed at lower or higher concentrations of l-carnitine hydrochloride. The results of the present study provide insights for how l-carnitine therapy may significantly improve human neuronal function, but we recommend that future studies further explore different derivatives of l-carnitine compounds in different in vitro cell-based systems using different markers of mitochondrial function. 相似文献
934.
935.
Molecular and Cellular Biochemistry - Skeletal muscle contains various myofiber types closely associated with satellite stem cells, vasculature, and neurons, thus making it difficult to perform... 相似文献
936.
Kenneth W. Able Mark J. Wuenschel Thomas M. Grothues James M. Vasslides Peter M. Rowe 《Environmental Biology of Fishes》2013,96(5):661-675
The fishes of the energetic surf zone of exposed ocean beaches are poorly known, especially along the U.S. east coast. We investigated the role that surf zones in southern New Jersey have as habitat by describing the young-of-the-year fishes caught by seines within the surf zone from May through October in 1998, 1999, 2005 and 2006. In addition, we investigated the nursery role of these surf zones by examining abundance, growth, and inferred survival during the summer for the dominant locally (New Jersey) and southern (south of Cape Hatteras) spawned species. At least three southern species, i.e. bluefish Pomatomus saltatrix (Cohort I), white mullet Mugil curema, and Florida pompano Trachinotus carolinus successfully use New Jersey surf zones as nurseries during the summer. It is clear that bluefish (Cohort I) contributes to the adult population and it is likely for the other southern species. Ultimately, the nursery contribution of surf zones and other habitats at the northern limits of the range of southern species depends on whether surviving juveniles can successfully emigrate to overwinter habitats and complete their life history. 相似文献
937.
Mark Q. Martindale 《Invertebrate reproduction & development.》2013,57(2):229-242
Summary In the spiralian embryos studied which display unequal-cleavage at the first two cleavages (either by a polar lobe or an asymmetric cleavage mechanism) the D quadrant is determined at the four cell stage by an unequal segregation of cytoplasmic stuffs. The normal formation of eyes, foot, and shell by overlying micromeres in these forms requires the inductive interaction with the D quadrant before the formation of the third quartet of micromeres. In equal-cleaving spiralians the D quadrant (3D macromere) becomes determined as a result of inductive interactions with first quartet derivatives (animal-vegetal interaction) sometime after the production of the third quartet of micromeres. This paper investigates the exact timing of D quadrant determination and the inductive role of third-order macromeres on the development of micromere derived structures in an equal-cleaving spiralian. Deletions of third-order macromeres, and their derivatives, were performed without rupturing the egg capsule membrane of the Lymnaea embryo with a UV laser microbeam. Virtually normal snails were produced when the 3A, 3B, 3C, or 4D macromere was irradiated. Juvenile snails lacking all mesodermal structures but possessing eyes, foot, and shell were obtained when the mesentoblast (4d) or its progenitor (3D) were deleted. Furthermore, ‘mesoderm-less’ snails were produced by deleting one of the two possible 3D candidates (cross furrow macromeres) as early as 20 min after third quartet formation. These results indicate that the 3D macromere begins to become determined at, or soon after, animal-vegetal interaction; before the 3D macromere becomes visibly distinguishable from the 3B macromere. The results also demonstrate that normal pattern formation in the overlying micromeres does not require the ‘prolonged’ interaction with an asymmetrically positioned 3D macromere. Possible adhesive differences between the 3D macromere and the remaining three macromeres are also revealed. 相似文献
938.
939.
940.
A Pseudomonas aeruginosa biofilm was produced in a model system using the bacterial strain NCIMB 8295, grown on silicone tubing (bore size 0.75 cm). Destruction of the biofilm was attempted using either ampicillin or a combination of white light (light dose=7.2 J cmm 2) and the phenothiazinium photosensitiser new methylene blue, and damage, both to extra-cellular polymeric substance (EPS) and to the organism, was monitored. It was found that although little damage to the EPS occurred with ampicillin, NMB caused both cell death and breakdown of the EPS, suggesting the use of photodynamic antimicrobial chemotherapy (PACT) in the disinfection of pathogenic biofilms, e.g. at external catheter surfaces. 相似文献