全文获取类型
收费全文 | 9060篇 |
免费 | 810篇 |
国内免费 | 239篇 |
专业分类
耳鼻咽喉 | 37篇 |
儿科学 | 124篇 |
妇产科学 | 42篇 |
基础医学 | 1290篇 |
口腔科学 | 418篇 |
临床医学 | 617篇 |
内科学 | 1061篇 |
皮肤病学 | 756篇 |
神经病学 | 788篇 |
特种医学 | 213篇 |
外科学 | 910篇 |
综合类 | 849篇 |
现状与发展 | 1篇 |
预防医学 | 377篇 |
眼科学 | 735篇 |
药学 | 1059篇 |
7篇 | |
中国医学 | 585篇 |
肿瘤学 | 240篇 |
出版年
2024年 | 29篇 |
2023年 | 220篇 |
2022年 | 188篇 |
2021年 | 434篇 |
2020年 | 358篇 |
2019年 | 346篇 |
2018年 | 342篇 |
2017年 | 347篇 |
2016年 | 310篇 |
2015年 | 371篇 |
2014年 | 584篇 |
2013年 | 701篇 |
2012年 | 528篇 |
2011年 | 594篇 |
2010年 | 419篇 |
2009年 | 379篇 |
2008年 | 377篇 |
2007年 | 385篇 |
2006年 | 303篇 |
2005年 | 268篇 |
2004年 | 252篇 |
2003年 | 232篇 |
2002年 | 176篇 |
2001年 | 154篇 |
2000年 | 136篇 |
1999年 | 112篇 |
1998年 | 123篇 |
1997年 | 127篇 |
1996年 | 109篇 |
1995年 | 104篇 |
1994年 | 82篇 |
1993年 | 77篇 |
1992年 | 71篇 |
1991年 | 83篇 |
1990年 | 75篇 |
1989年 | 53篇 |
1988年 | 66篇 |
1987年 | 61篇 |
1986年 | 53篇 |
1985年 | 86篇 |
1984年 | 74篇 |
1983年 | 57篇 |
1982年 | 69篇 |
1981年 | 49篇 |
1980年 | 44篇 |
1979年 | 30篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The interaction between myosin and F-actin requires the enzyme, myosin light chain kinase (MLCK), as well as Ca2+-calmodulin and the calmodulin binding protein, caldesmon, which also binds to F-actin. Using immunofluorescence staining, we have demonstrated that in human fetal astroglia as in mouse astroglia (Abd-El-Basset et al., 1991) the stress fibers contain these contractile elements: F-actin, myosin, tropomyosin and caldesmon. F-actin extends continuously along the stress fibers, whereas myosin, tropomyosin and caldesmon are localized discontinuously in a periodic pattern. In addition, we have demonstrated that fetal human astroglia have the enzyme MLCK and calmodulin. The association of the contractile elements listed above together with calmodulin and MLCK constitutes what may be termed ‘contractile units’, suggesting that the stress fibers in astroglia may be contractile. Contractile stress fibers would enable astroglia to exert tension on the matrix surrounding them, thus facilitating rapid changes in cell shape. 相似文献
82.
Functional characterization of the human atrial essential myosin light chain (hALC-1) in a transgenic rat model 总被引:1,自引:0,他引:1
Abdelaziz AI Segaric J Bartsch H Petzhold D Schlegel WP Kott M Seefeldt I Klose J Bader M Haase H Morano I 《Journal of molecular medicine (Berlin, Germany)》2004,82(4):265-274
Most patients with hypertrophic cardiomyopathy and congenital heart diseases express the atrial essential myosin light chains (ALC-1) in their ventricles, partially replacing the ventricular essential light chains (VLC-1). This VLC-1/ALC-1 isoform shift is correlated with an increase in cross-bridge cycling kinetics as measured using skinned fibers from the hypertrophied ventricles of human hearts.To study the functional importance of hALC-1 in the intact perfused heart, we generated a transgenic rat model (TGR) overexpressing hALC-1 in the heart. Twelve-week-old TGR rats expressed 17±4 g hALC-1 per mg of whole SDS-soluble protein. Their perfused heart contractility parameters were evaluated using the Langendorff preparation. Expression of hALC-1 was accompanied by statistically significant improvements (P<0.001) in the contractile parameters of the hearts of the TGR compared to the age matched control (WKY) animals, represented by increases from 20.8±2.3 to 45.1±3.6 mmHg/g heart weight in the developed left ventricular pressure, 1,035.7±89.8 to 2,181±135.4 mmHg/s in the contraction rate, and 713±60.2 to 1,364±137.4 mmHg/s in the relaxation rate in the WKY and the TGR groups respectively. Characterizing the functional effects of hALC-1 at the whole organ level represents a step towards gene therapy of heart failure. 相似文献
83.
Noninvasive measurement of human forearm oxygen consumption by near infrared spectroscopy 总被引:5,自引:0,他引:5
Roberto A. De Blasi Mark Cope Clare Elwell Fauzia Safoue Marco Ferrari 《European journal of applied physiology》1993,67(1):20-25
Summary This study reported on the application of near infrared spectroscopy (NIRS) to noninvasive measurements of forearm brachio-radial muscle oxygen consumption (
O2) and recovery time (t
r) in untrained volunteers. Seven healthy subjects were submitted to four consecutive protocols involving measurements made at rest, the induction of an ischaemia, and during a maximal increase of metabolic demand achieved with and without vascular occlusion. Two isometric maximal voluntary contractions (MVC) of 30-s duration were executed with and without vascular occlusion and a 50% MVC lasting 125 s was also performed. The protocols were repeated on 2 different days. The results showed that, during vascular occlusion at rest, the time to 95% of the final haemoglobin (Hb) + myoglobin (Mb) desaturation value was independent of
O2. The MVC, performed during vascular occlusion, caused complete Hb + Mb desaturation in 15–20 s, which was not followed by any further desaturation when the second contraction was performed. No difference was found between
O2during MVC with and without vascular occlusion. A consistent difference was seen between
O2measured during occlusion at rest and
O2measured during MVC with and without occlusion. During prolonged exercise (125 s) Hb + Mb desaturation was maintained for the whole contraction period. The results of this study show that
O2can be measured noninvasively by NIRS. The
O2during MVC was very similar both in the presence and absence of blood flow limitation in most of the subjects tested. This would suggest that muscle
O2might be accurately evaluated dynamically without cuff occlusion. 相似文献
84.
高精度红外光点位置检测分析系统是基于光电位置敏感器件、立体测量学研制而成的运动物体分析系统。它能快速、准确地测出运动物体各特征点的瞬时位置,并在此基础上进行分析计算,给出三维坐标及针对具体应用领域的特征曲线和参数。该系统可应用于人体运动检测、外科手术定位等领域。 相似文献
85.
Chemical catalysis, an effector mechanism utilized by fully assembled antibodies, can also be mediated by the isolated antibody subunits. Because trace amounts of free light chains (L chains) are present in IgG preparations, a detailed study was undertaken to identify the constituents responsible for the polyreactive proteolytic activity of IgG purified from human sera, determined as the extent of cleavage of the model peptide substrate Pro-Phe-Arg-methylcoumarinamide. Two proteolytic species with approximate mass of 50 kD and 150 kD were separated by repetitive gel filtration in a denaturing solvent (6 M guanidine hydrochloride). The activity of the renatured 50-kD fraction (in fluorescence units/microg protein) was more than 45-fold greater than of the 150-kD fraction. Both fractions lost the activity following immunoadsorption on immobilized anti-IgG antibody. Fab fragments prepared from the 150-kD IgG fraction retained the activity. Reducing and non-reducing SDS-electrophoresis suggested the 50-kD fraction isolated from the IgG preparations to be a mixture of heavy chain (H chain) monomers and disulphide bonded L chain dimers. Electrophoretically homogeneous monomers of 50-kD H chains and 25-kD L chains were prepared by gel filtration of reduced and alkylated IgG from seven human subjects. Each of the alkylated L chain preparations displayed the proteolytic activity. The activity in alkylated H chains was undetectable or only marginally greater than the background values. L chain dimers appear to be the major species responsible for the polyreactive proteolytic activity of serum IgG preparations, with a smaller contribution furnished by tetrameric IgG. 相似文献
86.
87.
88.
89.
Characterization of idiotopes on MOPC 315 IgA using monoclonal antiidiotypic antibodies 总被引:1,自引:0,他引:1
Terresa Nusair Reuben Baumal Robert Rosenstein Trond Jørgensen Alexander Marks 《Molecular immunology》1983,20(5):537-547
The isologous antiidiotypic response in BALB/c mice to immunization with the DNP-binding IgA myeloma protein, MOPC 315, alters the expression of the anti-DNP antibody repertoire and confers immunity against MOPC 315 myeloma tumors. In order to characterize the idiotopes on MOPC 315 IgA which elicit this response we have isolated four monoclonal antiidiotypic antibodies (AIA), D10 (IgG2a), A2(IgG1), G3 (IgG2b) and F1 (IgG2a), produced by splenocytes of BALB/c mice immunized with MOPC 315 IgA in three independent fusion experiments. These AIA react with MOPC 315 IgA. reassociated H315 L315 and F315V but not with free H315, L315, V315H or V3152. In addition the AIA do not react with the closely related DNP-binding IgA myeloma protein, MOPC 460, suggesting that they are directed against private idiotopes on MOPC 315 IgA. These idiotopes can be divided into two groups. Group I, defined by D10, A2 and G3 consists of two overlapping idiotopes, one of which is related to the hapten-binding site. The two idiotopes are formed by an interaction of amino acids in H315 and L315. Group II defined by F1 consists of one idiotope which is related to the hapten-binding site. This idiotope is comprised of an aminoacid sequence on H315 which requires an interaction with either L315 or L460 for expression. A2 and G3 react identically with the same idiotope but were derived from two independent fusion experiments. This indicates an identity of AIA clonotypes among individual mice and suggests that the isologous AIA response to MOPC 315 IgA is restricted. 相似文献
90.