全文获取类型
收费全文 | 11521篇 |
免费 | 945篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 147篇 |
儿科学 | 351篇 |
妇产科学 | 298篇 |
基础医学 | 1444篇 |
口腔科学 | 252篇 |
临床医学 | 1514篇 |
内科学 | 2054篇 |
皮肤病学 | 162篇 |
神经病学 | 1090篇 |
特种医学 | 247篇 |
外科学 | 1193篇 |
综合类 | 165篇 |
一般理论 | 17篇 |
预防医学 | 1567篇 |
眼科学 | 172篇 |
药学 | 897篇 |
中国医学 | 22篇 |
肿瘤学 | 896篇 |
出版年
2023年 | 122篇 |
2022年 | 128篇 |
2021年 | 287篇 |
2020年 | 236篇 |
2019年 | 293篇 |
2018年 | 310篇 |
2017年 | 253篇 |
2016年 | 308篇 |
2015年 | 305篇 |
2014年 | 368篇 |
2013年 | 575篇 |
2012年 | 821篇 |
2011年 | 909篇 |
2010年 | 440篇 |
2009年 | 375篇 |
2008年 | 684篇 |
2007年 | 663篇 |
2006年 | 710篇 |
2005年 | 649篇 |
2004年 | 523篇 |
2003年 | 524篇 |
2002年 | 512篇 |
2001年 | 205篇 |
2000年 | 176篇 |
1999年 | 168篇 |
1998年 | 107篇 |
1997年 | 81篇 |
1996年 | 72篇 |
1995年 | 59篇 |
1994年 | 56篇 |
1993年 | 51篇 |
1992年 | 113篇 |
1991年 | 104篇 |
1990年 | 121篇 |
1989年 | 96篇 |
1988年 | 92篇 |
1987年 | 81篇 |
1986年 | 77篇 |
1985年 | 69篇 |
1984年 | 50篇 |
1983年 | 48篇 |
1982年 | 33篇 |
1981年 | 35篇 |
1979年 | 64篇 |
1978年 | 53篇 |
1977年 | 33篇 |
1975年 | 35篇 |
1974年 | 48篇 |
1973年 | 39篇 |
1971年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Gunilla Caisander Hannah Park Katarina Frej Jenny Lindqvist Christina Bergh Kersti Lundin Charles Hanson 《Chromosome research》2006,14(2):131-137
There have been recent reports of human embryonic stem cell (hESC) lines developing chromosomal aberrations after long-term
culture, indicating an unstable genomic status due to the in vitro milieu. This raises concern, since it would limit their use in therapeutics. In this study the chromosomal status of five
well-characterized hESC lines, SA002, SA002.5, AS034.1.1, SA121 and SA461, was monitored during long-term in vitro culture. The criteria of defined hESCs were met by all of the five hESC lines (four diploid and one trisomic for chromosome
13). The genomes were screened for chromosomal aberrations and rearrangements using comparative genomic hybridization (CGH),
interphase fluorescence in situ hybridization (FISH) and traditional karyotyping on several occasions while in culture. The genomic integrity was shown to
be maintained after repeated freeze-thaw procedures and continuous culture in vitro for up to 22 months (148 passages). We discuss the most common de novo chromosomal aberrations reported in hESCs, as well as their possible origin. 相似文献
82.
High expression of MDR1, MRP1, and MRP3 in the hepatic progenitor cell compartment and hepatocytes in severe human liver disease 总被引:8,自引:0,他引:8
An increase in bile ductular structures is observed in diverse human liver diseases. These structures harbour the progenitor cell compartment of the liver. Since ATP-binding cassette (ABC) transporters may have a cytoprotective role in liver disease, an immunohistochemical study was performed on human liver specimens from patients with primary biliary cirrhosis (PBC), chronic hepatitis C virus (HCV) infection, submassive cell necrosis, and normal liver. The expression of MDR1, MDR3, BSEP, MRP1, MRP2, and MRP3 was determined using specific antibodies. Dilution series were constructed to determine the critical staining level in order to estimate the factor of up-regulation. In normal liver, hepatocytes showed canalicular staining for MDR3, BSEP, and MRP2. MDR1 stained the canalicular membrane of hepatocytes as well as that of cholangiocytes. MRP3 showed low immunoreactivity of bile duct epithelial cells and centrilobular hepatocytes only. Normal liver showed no immunoreactivity for MRP1. In diseased liver, the expression of MDR3, BSEP, and MRP2 was relatively stable. In PBC, HCV, and submassive necrosis, the expression levels of MDR1, MRP1, and MRP3 were increased. The strongest immunoreactivity was seen after submassive necrosis, where remaining islands of hepatocytes showed strong canalicular staining for MDR1 and MRP3. Regenerating bile ductules at the interface of portal tracts and necrotic areas stained intensely for MDR1, MRP1, and MRP3. In conclusion, MDR1, MRP1, and MRP3 are up-regulated in hepatocytes in severe human liver disease. Strong MDR1, MRP1, and MRP3 reactivity is seen in regenerating human bile ductules. 相似文献
83.
Receptor types in cat hairy skin supplied by myelinated fibers 总被引:9,自引:0,他引:9
84.
This paper describes the outcomes of episodes of care for adults in public sector mental health services across Australia, with a view to informing the debate on service quality. Health of the Nation Outcome Scales (HoNOS) change scores and effect sizes were calculated for 14,659 acute inpatient episodes and 23,692 community episodes. The results showed that people in contact with public sector mental health services generally do get better, although the magnitude of improvement depends on the setting and episode type. This confirmatory finding is particularly positive, given current community concerns about the quality and effectiveness of mental health services. 相似文献
85.
Burgess A 《Medical physics》2004,31(7):1987-1995
A recent paper by Cooper et al. [Med. Phys. 30, 2614-2621 (2003)] contains some apparently anomalous results concerning the relationship between pixel variance and x-ray exposure for a digital mammography system. They found an unexpected peak in a display domain pixel variance plot as a function of 1/mAs (their Fig. 5) with a decrease in the range corresponding to high display data values, corresponding to low x-ray exposures. As they pointed out, if the detector response is linear in exposure and the transformation from raw to display data scales is logarithmic, then pixel variance should be a monotonically increasing function in the figure. They concluded that the total system transfer curve, between input exposure and display image data values, is not logarithmic over the full exposure range. They separated data analysis into two regions and plotted the logarithm of display image pixel variance as a function of the logarithm of the mAs used to produce the phantom images. They found a slope of minus one for high mAs values and concluded that the transfer function is logarithmic in this region. They found a slope of 0.6 for the low mAs region and concluded that the transfer curve was neither linear nor logarithmic for low exposure values. It is known that the digital mammography system investigated by Cooper et al. has a linear relationship between exposure and raw data values [Vedantham et al., Med. Phys. 27, 558-567 (2000)]. The purpose of this paper is to show that the variance effect found by Cooper et al. (their Fig. 5) arises because the transformation from the raw data scale (14 bits) to the display scale (12 bits), for the digital mammography system they investigated, is not logarithmic for raw data values less than about 300 (display data values greater than about 3300). At low raw data values the transformation is linear and prevents over-ranging of the display data scale. Parametric models for the two transformations will be presented. Results of pixel variance measurements made on raw data images will be presented. The experimental data are in good agreement with those of Cooper et al. It will be shown that the slope of 0.6 found by Cooper et al. for the log-log plot at low exposure is not due to transfer function nonlinearity, it occurs because of an additive variance term-possibly due to electronic noise. It will also be shown, using population statistics from clinical images, that raw data values below 300 are rare in tissue areas. Those tissue areas with very low raw data values are within about a millimeter of the chest wall or in very dense muscle at comers of images. 相似文献
86.
H. Ping Ting-Beall Florence M. Burgess Laszlo Dux Anthony Martonosi 《Journal of muscle research and cell motility》1987,8(3):252-259
Summary Two distinct forms of Ca2+-ATPase crystals have been analysed in sarcoplasmic reticulum (SR) membranes. The E1-type crystals, induced by Ca2+ or lanthanide ions, consist of single chains of ATPase monomers, and the E2-type crystals, induced by vanadate ions, consist of dimer chains. Using improved freeze-fracture techniques we have obtained high-resolution images of complementary surface replicas of SR membranes containing these crystal forms. In E1 crystals, the concave fracture (P) faces display obliquely oriented rows of intramembrane particles (IMPs) spaced at - 6–7 nm along both crystal axes, while the convex fracture (E) faces show corresponding rows of pits. In E2 crystals, regular arrays of oblique parallel ridges with spacing of - 10.5–11 nm appear on the P-faces and complementary grooves or furrows on the E-faces. In many instances the ridges break up into elongated particles repeating every 5.5 nm. When the direction of the shadow is almost parallel to the axis of the ridges, these 9.5 nm particles can be resolved into two domains, which represent intramembranous contacts between the two monomers of the two adjacent dimer chains. Complementary grooves on the E-faces can also be resolved into rows of pits complementary to the particles of the ridges on the P-faces. In the control SR membranes, randomly dispersed IMPs and corresponding pits are observed on the P- and E-faces, respectively. The data suggest that transport of Ca2+ involves significant structural changes of the enzyme molecule, reflected in the ATPase-ATPase interactions both on the cytoplasmic surface and in the lipid bilayer. 相似文献
87.
In the present study we compared genetically selected aggressive (TA) and nonaggressive (TNA) male mice, as well as males from an unselected control line (SW), in three tests of anxiety: the elevated plus-maze, the light-dark box, and the staircase test. Males were tested repeatedly for 3 days. In all three tests TA males were found to be more active and less anxious than TNA males, with SW males showing more or less intermediate scores. Furthermore, repeated plus-maze testing induced anxiety-like behavior in both TA and TNA mice, whereas repeated testing in the light-dark and staircase paradigms resulted in different responses. Whereas TNA animals were found to be stable, TA animals showed habituation on the second and third day of testing. The obtained data support the conclusion that a higher-level offensive aggression entails lower level of anxiety. 相似文献
88.
Although hemagglutination by Staphylococcus aureus has been associated with the pathogenesis of bovine mastitis, this trait has not been characterized with regard to human disease. In this study, the prevalence of hemagglutination in 100 strains of S. aureus responsible for bovine mastitis or human bacteremia, was characterized. Under optimum conditions hemagglutination was noted in 23% of the bovine strains, but only 13% of human strains, leading us to conclude that this trait is not a significant virulence determinant in human systemic infection. Additional studies indicate the hemagglutinin of S. aureus strains responsible for human bacteremia is proteinaceous in character. 相似文献
89.
90.
T J Merimee D Rabinowitz L Riggs J A Burgess D L Rimoin V A McKusick 《The New England journal of medicine》1967,276(8):434-439