全文获取类型
收费全文 | 31835篇 |
免费 | 1955篇 |
国内免费 | 158篇 |
专业分类
耳鼻咽喉 | 268篇 |
儿科学 | 497篇 |
妇产科学 | 348篇 |
基础医学 | 4714篇 |
口腔科学 | 945篇 |
临床医学 | 3076篇 |
内科学 | 7555篇 |
皮肤病学 | 507篇 |
神经病学 | 3562篇 |
特种医学 | 1912篇 |
外科学 | 4261篇 |
综合类 | 184篇 |
一般理论 | 11篇 |
预防医学 | 1371篇 |
眼科学 | 644篇 |
药学 | 1794篇 |
中国医学 | 52篇 |
肿瘤学 | 2247篇 |
出版年
2024年 | 28篇 |
2023年 | 268篇 |
2022年 | 448篇 |
2021年 | 830篇 |
2020年 | 512篇 |
2019年 | 716篇 |
2018年 | 801篇 |
2017年 | 625篇 |
2016年 | 893篇 |
2015年 | 1020篇 |
2014年 | 1262篇 |
2013年 | 1560篇 |
2012年 | 2542篇 |
2011年 | 2557篇 |
2010年 | 1531篇 |
2009年 | 1376篇 |
2008年 | 2242篇 |
2007年 | 2263篇 |
2006年 | 2186篇 |
2005年 | 2042篇 |
2004年 | 1776篇 |
2003年 | 1666篇 |
2002年 | 1574篇 |
2001年 | 282篇 |
2000年 | 236篇 |
1999年 | 309篇 |
1998年 | 312篇 |
1997年 | 234篇 |
1996年 | 173篇 |
1995年 | 159篇 |
1994年 | 131篇 |
1993年 | 94篇 |
1992年 | 91篇 |
1991年 | 85篇 |
1990年 | 63篇 |
1989年 | 83篇 |
1988年 | 58篇 |
1987年 | 47篇 |
1986年 | 48篇 |
1985年 | 45篇 |
1984年 | 43篇 |
1983年 | 46篇 |
1982年 | 42篇 |
1981年 | 38篇 |
1980年 | 39篇 |
1978年 | 31篇 |
1975年 | 29篇 |
1937年 | 31篇 |
1936年 | 28篇 |
1935年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Dudel J Hallermann S Heckmann M 《Pflügers Archiv : European journal of physiology》2000,441(2-3):175-180
Quartz glass electrodes are superior to conventional glass electrodes for low-noise recording. They have better electrical characteristics and hydrophobic surfaces which resist creeping of salt solutions. We used oxy-hydrogen heating with program-controlled gas pressure to melt quartz glass capillaries. Usually, the relative wall thickness (the quotient of the outer and inner diameters do/di) of capillaries is, at best, maintained up to the electrode tip. If tips with thicker walls can be produced, coating and other surface treatments can be avoided. We found that programmed heating periods without pull allowed an fivefold increase of do/di in the tip region. Since do/di is inversely proportional to input capacity, the recording noise was minimized and became insignificant relative to amplifier and holder noise. A sample patch-clamp recording is shown. 相似文献
103.
104.
105.
Connective tissue growth factor expression and Smad signaling during mouse heart development and myocardial infarction. 总被引:5,自引:0,他引:5
Susana M Chuva de Sousa Lopes Alie Feijen Jeroen Korving Olexander Korchynskyi Jonas Larsson Stefan Karlsson Peter ten Dijke Karen M Lyons Roel Goldschmeding Pieter Doevendans Christine L Mummery 《Developmental dynamics》2004,231(3):542-550
Connective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor beta (TGFbeta) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFbeta signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFbeta expression as well as activated forms of TGFbeta but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFbeta during the pathological fibrotic response. 相似文献
106.
107.
Peptide motifs of closely related HLA class I molecules encompass substantial differences. 总被引:11,自引:0,他引:11
Olaf Rtzschke Kirsten Falk Stefan Stevanovi Günther Jung Hans-Georg Rammensee 《European journal of immunology》1992,22(9):2453-2456
The peptides presented by major histocompatibility complex class I molecules adhere to strict rules concerning peptide length and occupancy by certain amino acid residues at anchor positions. Peptides presented by HLA-A*0201 molecules, for example, are generally nonapeptides requiring Leu or Met at position 2 and an aliphatic residue, predominantly Val, at position 9. A closely related molecule, HLA-A*0205, differing from the former at four amino acid residues, has a related but substantially different peptide motif. A*0205-presented peptides are still nonapeptides, and position 9 is still aliphatic, although it is preferentially occupied by Leu instead of Val. Position 2 not only allows aliphatic residues but also polar ones. Occupancy at position 6, considered as an auxiliary anchor in A*0201, as well as non-anchor residues at positions 3, 4, and 8 are relatively well conserved between the two peptide motifs. Thus, although a number of the T cell epitopes presented by the two HLA-A2 forms is expected to be identical, a considerable number of epitopes should be different. 相似文献
108.
Stefan Schneider Gunnar Folprecht Georg Krohne Hans Oberleithner 《Pflügers Archiv : European journal of physiology》1995,430(5):795-801
The nuclear envelope functions as a selective barrier separating the nuclear from the cytosolic compartment. Nuclear pore complexes (NPCs) mediate nuclear import and export of macromolecules and, therefore, are potential regulators of gene expression. In this study we applied atomic force microscopy (AFM) to visualize the three dimensional (3D) structure of individual NPCs in the absence and presence of two different antibodies, one directed against a pore protein (gp62) and another directed against Xenopus lamin LIII, a component of the nuclear lamina, a filament meshwork localized on the nucleoplasmic side of the nuclear envelope (NE) adjacent to and interacting with NPCs. Using 12-nm gold-labelled secondary antibodies and transmission electron microscopy we could clearly localize the primary single anti-gp62 antibody on NPCs and the primary single anti-LIII antibody between NPCs. Using AFM, the secondary antibodies against anti-gp62 could be detected as particles 7 nm in height on the nucleoplasmic face of NPCs. The secondary antibodies against anti-LIII could be clearly identified between NPCs. The secondary antibodies, attached to a 12-nm colloidal gold particle and visualized on glass, revealed similar shapes and heights as found on NEs. According to the 3D images, the volume of a single gold particle conjugated with secondary antibodies was 10 203 nm3. This volume is equivalent to the volume of 38 IgG molecules associated with one individual gold particle. A similar volume of 11 987 nm3 was calculated from a model assuming that the 150-kDa IgG molecules perfectly cover the spherical gold particle. We conclude that AFM can be used for identifying antibodies or other macromolecules associated with biomembranes. 相似文献
109.
Hans Oberleithner Barbara Schuricht Stefan Wünsch Stefan Schneider Bernd Püschel 《Pflügers Archiv : European journal of physiology》1993,423(1-2):88-96
Condensation of chromatin depends upon the ion composition in the cell nucleus. We tested in isolated nuclei of Madin-Darby canine kidney cells the influence of various ions on nuclear volume (i. e. DNA packing) and intranuclear voltage. After isolation, nuclei were superfused with cytosolic solutions in which Na+, K+, Ca2+ and H+ ions were varied. With video-imaging and microelectrode techniques nuclear volume and intranuclear potential were measured in response to the various ions. In control cytosolic solution, isolated nuclei exhibited an intranuclear electrical potential of –6.5±0.5 mV (relative to a reference electrode in the cytosolic solution) corresponding to a nuclear volume of 250±10 fl (n=104). Changing the Na+, K+ or free Ca2+ concentration in the superfusate in the physiological range resulted in minor changes of volume and intranuclear potential whereas pH altered both parameters dramatically. Nuclear swelling and intranuclear negative voltage increased with alkalinization and decreased when pH was reduced. An intact nuclear envelope was found to be no prerequisite for maintaining intranuclear negativity, indicating that the composition and functional state of nuclear chromatin rather than specific ion permeabilities of the nuclear envelope determine nuclear electrical potential. We present a model that explains nuclear volume and voltage on the basis of interaction between negatively charged DNA and positively charged histones of the nuclear chromatin. 相似文献
110.
Panizzutti R Rausch M Zurbrügg S Baumann D Beckmann N Rudin M 《Neuroscience letters》2005,380(1-2):111-115
d-Serine has been proposed as an endogenous modulator at the co-agonist glycine-binding site of N-methyl-d-aspartate (NMDA) receptors. There is still some debate as to whether this site is saturated in vivo, but it seems likely that this depends on regional differences in local glycine or d-serine concentrations. In order to identify areas where the co-agonist site was not fully activated in vivo, we studied the effect of intraperitoneal d-serine administration in the rat brain using functional magnetic resonance imaging (fMRI). Using contrast agent injection, the variations in the relative cerebral blood volume (CBVrel) in several regions of interest were evaluated. d-Serine (50 mg/kg) elicited a significant statistical increase in the CBVrel in the hippocampus. This effect was inhibited by the specific full antagonist of the co-agonist glycine site L-701,324 indicating that the hippocampal activation occurred through the binding of the agonist d-serine to the glycine-binding site of NMDA receptors. This result demonstrates that in the hippocampus, the co-agonist sites of NMDA receptors are not endogenously saturated under our experimental conditions, suggesting an important role of d-serine in the modulation of receptor function in the hippocampus. 相似文献