全文获取类型
收费全文 | 170701篇 |
免费 | 10269篇 |
国内免费 | 417篇 |
专业分类
耳鼻咽喉 | 2241篇 |
儿科学 | 5545篇 |
妇产科学 | 3578篇 |
基础医学 | 23228篇 |
口腔科学 | 7514篇 |
临床医学 | 12479篇 |
内科学 | 38408篇 |
皮肤病学 | 4363篇 |
神经病学 | 14219篇 |
特种医学 | 5285篇 |
外国民族医学 | 26篇 |
外科学 | 21069篇 |
综合类 | 1389篇 |
现状与发展 | 1篇 |
一般理论 | 60篇 |
预防医学 | 17921篇 |
眼科学 | 3170篇 |
药学 | 10360篇 |
中国医学 | 688篇 |
肿瘤学 | 9843篇 |
出版年
2023年 | 885篇 |
2022年 | 1937篇 |
2021年 | 3623篇 |
2020年 | 2437篇 |
2019年 | 3434篇 |
2018年 | 4847篇 |
2017年 | 3634篇 |
2016年 | 3363篇 |
2015年 | 3937篇 |
2014年 | 5408篇 |
2013年 | 6836篇 |
2012年 | 10663篇 |
2011年 | 11143篇 |
2010年 | 5625篇 |
2009年 | 5073篇 |
2008年 | 8613篇 |
2007年 | 9227篇 |
2006年 | 8561篇 |
2005年 | 8856篇 |
2004年 | 8346篇 |
2003年 | 7625篇 |
2002年 | 5685篇 |
2001年 | 4984篇 |
2000年 | 4985篇 |
1999年 | 4373篇 |
1998年 | 1547篇 |
1997年 | 1290篇 |
1996年 | 1287篇 |
1995年 | 1096篇 |
1994年 | 1080篇 |
1993年 | 984篇 |
1992年 | 2676篇 |
1991年 | 2590篇 |
1990年 | 2357篇 |
1989年 | 2351篇 |
1988年 | 2123篇 |
1987年 | 1961篇 |
1986年 | 1841篇 |
1985年 | 1762篇 |
1984年 | 1263篇 |
1983年 | 1014篇 |
1982年 | 572篇 |
1981年 | 519篇 |
1980年 | 501篇 |
1979年 | 924篇 |
1978年 | 611篇 |
1977年 | 479篇 |
1975年 | 545篇 |
1974年 | 546篇 |
1973年 | 544篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dai Z Weichenhan D Wu YZ Hall JL Rush LJ Smith LT Raval A Yu L Kroll D Muehlisch J Frühwald MC de Jong P Catanese J Davuluri RV Smiraglia DJ Plass C 《Genome research》2002,12(10):1591-1598
Knudson's two-hit hypothesis postulates that genetic alterations in both alleles are required for the inactivation of tumor-suppressor genes. Genetic alterations include small or large deletions and mutations. Over the past years, it has become clear that epigenetic alterations such as DNA methylation are additional mechanisms for gene silencing. Restriction Landmark Genomic Scanning (RLGS) is a two-dimensional gel electrophoresis that assesses the methylation status of thousands of CpG islands. RLGS has been applied successfully to scan cancer genomes for aberrant DNA methylation patterns. So far, the majority of this work was done using NotI as the restriction landmark site. Here, we describe the development of RLGS using AscI as the restriction landmark site for genome-wide scans of cancer genomes. The availability of AscI as a restriction landmark for RLGS allows for scanning almost twice as many CpG islands in the human genome compared with using NotI only. We describe the development of an AscI-EcoRV boundary library that supports the cloning of novel methylated genes. Feasibility of this system is shown in three tumor types, medulloblastomas, lung cancers, and head and neck cancers. We report the cloning of 178 AscI RLGS fragments via two methods by use of this library. 相似文献
992.
cagA Status and eradication treatment outcome of anti-Helicobacter pylori triple therapies in patients with nonulcer dyspepsia
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Broutet N Marais A Lamouliatte H de Mascarel A Samoyeau R Salamon R Mégraud F 《Journal of clinical microbiology》2001,39(4):1319-1322
The differences in eradication rates reported in clinical trials aiming to cure Helicobacter pylori infection cannot be entirely explained by the type of regimen, bacterial resistance, or lack of compliance. Using data from a clinical trial, a logistic regression model was constructed to determine whether cagA status, assessed by PCR, affects the outcome of eradication. Resistance to clarithromycin (10% of the strains) predicted failure perfectly. In the model (n = 156), a cagA-lacking strain (odds ratio [OR] = 2.2; 95% confidence interval [CI], (1.1 to 4.7), tobacco smoking OR = 3.1; 95% CI, 1.3 to 7.0), and a double dose of proton pump inhibitor in the treatment regimen (OR = 0.3; 95% CI, 0.2 to 0.7) were associated with the treatment outcome. The exact role of cagA in the outcome of H. pylori eradication therapy has not been explored. However, the type of histological lesions which it causes in the gastric mucosa may be implicated. Regardless of the mechanism involved, cagA status is a good predictive marker of eradication outcome. 相似文献
993.
Reactivity differences among human T cells from blood and lymphoid organs, analysed by limiting dilution: correlation with specific gravity and binding of peanut lectin.
下载免费PDF全文
![点击此处可从《Clinical and experimental immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R J Van de Griend R Van Doorn L Stricker W P Zeijlemaker D Roos 《Clinical and experimental immunology》1981,45(2):376-385
Human T cells from peripheral blood, cord blood, thymus, spleen and lymph node were analysed for their proliferative response capacity to mitogens, for their specific gravity and size, and for their binding capacity of peanut agglutinin. A close correlation was found between these parameters: thymocytes and T cells from spleen were consistently heavier and smaller, and showed a lower proliferative response capacity, than T cells from blood or lymph node. Similarly, within each cell population, the small, heavy cells were least reactive. The limiting-dilution analysis revealed that heavy T cells from peripheral blood contain a lower number of reactive cells than the light peripheral T lymphocytes. Because heavy T cells from the thymus bound more peanut lectin than did light cells, it is speculated that the differences between T cells of high and low specific gravity might reflect differences in maturation level. 相似文献
994.
H. Arabi H. Vandewalle P. Pitor J. de Lattre H. Monod 《European journal of applied physiology》1997,76(2):122-127
The present experiment was designed to study the importance of strength and muscle mass as factors limiting maximal oxygen uptake (V˙O2 max ) in wheelchair subjects. Thirteen paraplegic subjects [mean age 29.8 (8.7) years] were studied during continuous incremental exercises until exhaustion on an arm-cranking ergometer (AC), a wheelchair ergometer (WE) and motor-driven treadmill (TM). Lean arm volume (LAV) was estimated using an anthropometric method based upon the measurement of various circumferences of the arm and forearm. Maximal strength (MVF) was measured while pushing on the rim of the wheelchair for three positions of the hand on the rim (?30°, 0° and +30°). The results indicate that paraplegic subjects reached a similar V˙O2 max [1.23 (0.34) l?·?min?1, 1.25 (0.38) l?·?min?1, 1.22?(0.18) l?·?min?1 for AC, TM and WE, respectively] and V˙O2 max /body mass [19.7?(5.2)?ml?·?min?1?·?kg?1, 19.5 (6.14) ml?·?min?1?·?kg?1, 19.18 (4.27) ml?·?min?1?·?kg?1 for AC, TM and WE, respectively on the three ergometers. Maximal heart rate f c max during the last minute of AC (173 (17) beats?·?min?1], TM [168 (14) beats?·?min?1], and WE [165 (16) beats?·?min?1], were correlated, but f c max was significantly higher for AC than for TM (P<0.03). There were significant correlations between MVF and LAV (P<0.001) and between the MVF data obtained at different angles of the hand on the rim [311.9 (90.1) N, 313.2 (81.2) N, 257.1 (71) N, at ?30°, 0° and +30°, respectively]. There was no correlation between V˙O2 max and LAV or MVF. The relatively low values of f c max suggest that V˙O2 max was, at least in part, limited by local aerobic factors instead of central cardiovascular factors. On the other hand, the lack of a significant correlation between V˙O2 max and MVF or muscle mass was not in favour of muscle strength being the main factor limiting V˙O2 max in our subjects. 相似文献
995.
Increased [Met]enkephalin and decreased substance P in spinal cord following thermal injury to one limb. 总被引:1,自引:0,他引:1
Thermal injury to one hind limb of rats was induced by immersion into water at 62 degrees C. Both a mild (15 s) or severe (30 s) lesion caused inflammation of the limb when observed 24 h later; but at this time the animals used the injured limb when they walked. Animals with a severe lesion of the injured limb subsequently withdrew it from use when walking. Limb withdrawal did not occur following a mild lesion. At 24 h following the lesion, lumbar spinal cord levels of [Met]enkephalin, as measured by radioimmunoassay, were elevated (70%) bilaterally in both hemisegments, ipsi- and contralateral to the lesion. At seven days following either mild or severe hind limb lesion [Met]enkephalin levels were elevated only in the ipsilateral lumbar hemisegment. At that time no changes in thoracic [Met]enkephalin levels were observed. Substance P levels were decreased (20-25%) bilaterally in the lumbar cord 24 h following a severe limb lesion, but no change was observed at seven days in any cord segment following a mild or severe lesion. Changes in spinal cord [Met]enkephalin content occur in response to thermal injury to one hind limb. However, the changes do not appear to be related to the withdrawal of the damaged limb from use following a severe lesion. Peptide changes in the spinal cord may reflect pain or injury to the damaged limb following a thermal lesion. In contrast, limb withdrawal may be a physiological rest mechanism related to altered basal ganglia peptide function. 相似文献
996.
Ezio Martuscelli Clara Silvestre Maurizio Canetti Claudia de Lalla Anna Bonfatti Alberto Seves 《Macromolecular chemistry and physics.》1989,190(10):2615-2625
The crystallization and the thermal behaviour of thin films of isotactic polypropylene/hydrogenated oligo(cyclopentadiene) of low molecular weight (iPP/HOCP) are studied using optical microscopy and differential scanning calorimetry (DSC). The spherulite growth rate, the overall crystallization rate and the equilibrium melting temperature of iPP are decreased by the addition of HOCP to iPP. This leads to the hypothesis that iPP and HOCP form a miscible blend in the amorphous phase. This hypothesis is also supported by the detection of a single blend-composition-dependent glass transition temperature of each blend as determined by DSC. 相似文献
997.
A glycoprotein (gp-88) secreted by pseudorabies virus (PRV) infected cells was isolated and purified. Anti gp-88 antibodies were used to screen an expression library constructed in Escherichia coli using genomic PRV DNA. Two positive clones were identified and the cloned genetic information was used to localize the corresponding gene in the unique short region of the PRV genome. Antibodies to the glycoprotein were also used to identify the unglycosylated precursor as synthesized in an in vitro translation system. A major precursor of 65 kDa was detected. Although the glycoprotein described here was not found as a major structural glycoprotein of the virion, antibodies to gp-88 are able to neutralise viral activity in vitro. The possible relationship with known glycoproteins of PRV is discussed. 相似文献
998.
N. Frejre-Maia J. Felizau A. C. de Figueiredo John M. Opitz Marisa Parreira Néria A. Maia 《Clinical genetics》1976,10(5):303-306
Hypertrichosis lanuginosa (without gingival hyperplasia) is described in a mother and son; the latter also had photophobia, infantile genitalia, growth retardation, hypotension, low IQ and dental abnormalities (hyperdontia, permanence of deciduous and delayed eruption of permanent teeth). Both have normal dermatoglyphics. Some clinical findings are discussed. The presence of this syndrome in a mother and son supports an autosomal mode of inheritance (with variable expressivity). Hypertrichosis lanuginosa is a pure monomultidysplasia and may be classified with the tricho-odontic sub-group of the ectodermal dysplasias. 相似文献
999.
1000.
Haupt SS Spengler F Husemann R Dinse HR 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2004,155(4):485-499
We recorded neurons extracellularly in layers II/III, IV, and V of the hindpaw representation of primary somatosensory cortex in anesthetized rats and studied laminar features of receptive fields (RFs) and representational maps. On average, RFs were smallest in layer IV and largest in layer V; however, for individual penetrations we found substantial deviations from this rule. Within the hindpaw representation, a distinct rostrocaudal gradient of RF size was present in all layers. While layer V RFs were generally largest independent of this gradient, layer IV RFs recorded caudally representing the proximal portions of the paw were larger than layer II/III RFs recorded rostrally representing the digits. The individual scatter of the locations of RFs across laminar groups was in the range of several millimeters, corresponding to about 25% of the average RF diameter. The cutaneous representations of the hindpaw in extragranular layers were confined to the areal extent defined by responsive sites in layer IV. Comparison between RFs determined quantitatively and by handplotting showed a reliable correspondence. Repeated measurements of RFs revealed spontaneous fluctuations of RF size of no more than 5% of the initial condition over an observation period of several hours. The topography and variability of cortical maps of the hindpaw representation were studied with a quantitative interpolation method taking into account the geometric centers of RFs and the corresponding cortical recording sites. On average, the overall topography in terms of preservation of neighborhood relations was present in all layers, although some individual maps showed severe distortions of topography. Factors contributing to map variability were overall position of the representation on the cortical surface, internal topography and spatial extent. Interindividual variability of map layout was always highest in the digit representations. Local topographic orderliness was lowest in layer V, but comparable in layers II/III and IV. Within layer IV, the lowest orderliness was observed in the digit representations. Our data emphasize a substantial variability of RF size, overlap and position across layers and within layers. At the level of representational maps, we found a similar degree of variability that often co-varied across layers, with little evidence for significant layer specificity. Laminar differences are likely to arise from the specific input-output pattern, layer-specific cell types and the connectivity between different layers. Our findings emphasizing similarities in the variability across layers support the notion of tightly coupled columnar interactions between different layers. 相似文献