全文获取类型
收费全文 | 26414篇 |
免费 | 1345篇 |
国内免费 | 251篇 |
专业分类
耳鼻咽喉 | 213篇 |
儿科学 | 513篇 |
妇产科学 | 621篇 |
基础医学 | 2786篇 |
口腔科学 | 523篇 |
临床医学 | 2283篇 |
内科学 | 7728篇 |
皮肤病学 | 565篇 |
神经病学 | 2317篇 |
特种医学 | 918篇 |
外科学 | 4333篇 |
综合类 | 62篇 |
一般理论 | 5篇 |
预防医学 | 952篇 |
眼科学 | 346篇 |
药学 | 1373篇 |
中国医学 | 43篇 |
肿瘤学 | 2429篇 |
出版年
2024年 | 27篇 |
2023年 | 224篇 |
2022年 | 461篇 |
2021年 | 773篇 |
2020年 | 487篇 |
2019年 | 642篇 |
2018年 | 763篇 |
2017年 | 588篇 |
2016年 | 724篇 |
2015年 | 784篇 |
2014年 | 1003篇 |
2013年 | 1376篇 |
2012年 | 2124篇 |
2011年 | 2079篇 |
2010年 | 1225篇 |
2009年 | 1096篇 |
2008年 | 1911篇 |
2007年 | 1811篇 |
2006年 | 1654篇 |
2005年 | 1664篇 |
2004年 | 1527篇 |
2003年 | 1347篇 |
2002年 | 1244篇 |
2001年 | 158篇 |
2000年 | 111篇 |
1999年 | 162篇 |
1998年 | 219篇 |
1997年 | 200篇 |
1996年 | 155篇 |
1995年 | 183篇 |
1994年 | 150篇 |
1993年 | 142篇 |
1992年 | 92篇 |
1991年 | 80篇 |
1990年 | 93篇 |
1989年 | 56篇 |
1988年 | 51篇 |
1987年 | 42篇 |
1986年 | 54篇 |
1985年 | 57篇 |
1984年 | 58篇 |
1983年 | 43篇 |
1982年 | 53篇 |
1981年 | 32篇 |
1980年 | 43篇 |
1979年 | 27篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1975年 | 19篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
O'Brien SG Guilhot F Larson RA Gathmann I Baccarani M Cervantes F Cornelissen JJ Fischer T Hochhaus A Hughes T Lechner K Nielsen JL Rousselot P Reiffers J Saglio G Shepherd J Simonsson B Gratwohl A Goldman JM Kantarjian H Taylor K Verhoef G Bolton AE Capdeville R Druker BJ;IRIS Investigators 《The New England journal of medicine》2003,348(11):994-1004
102.
Ferdinando Iellamo Jacopo Maria Legramante Filippo Castrucci Michele Massaro Gianfranco Raimondi Giuseppe Peruzzi Giuseppe Tallarida 《European journal of applied physiology》1993,66(5):381-387
Summary In recent studies in humans the role of cardiopulmonary baroreflexes in modulating the cardiovascular responses to isometric exercise (somatic pressor reflex) has been investigated by performing static hand-grip exercise during deactivation of cardiopulmonary receptors produced by low levels of lower body negative pressure; however, findings from these studies have not been consistent. The purpose of this study was to investigate whether a more physiological unloading stimulus of cardiopulmonary baroreceptors, obtained by sequentially changing posture, could influence the pressor response to somatic afferent stimulation induced by isometric, exercise. To accomplish this, ten healthy subjects performed a 2-min isometric handgrip (IHG) at 30% maximal voluntary contraction after 10 min of supine rest and, in rapid sequence, after 10 min of sitting and 10 min of standing, at the time when, owing to their transitory nature, the cardiovascular effects, due to arterial baroreceptor intervention should have been minimal. During IHG arterial pressure (BPa) was continuously and noninvasively measured to quantify accurately the blood pressure response to IHG both in magnitude and time course. Results showed that the pressor response to IHG was not significantly influenced by change in posture, either in magnitude or in time course. The mean arterial pressure increased by 17.4 (SEM 2.5), 18.6 (SEM 1.2) and 17.0 (SEM 1.3) mmHg in supine, sitting and standing [2.3 (SEM 0.3), 2.5 (SEM 0.2) and 2.3 (SEM 0.2) kPa] positions, respectively. Also the heart rate response to IHG was unaffected by change in posture. Most important, the sum of the separate BPa responses induced by supine IHG and by posture change from supine to sitting (summation of reflexes) was not significantly different from the pressor response observed during sitting IHG (interaction of reflexes). Likewise, the sum of the separate BPa. responses induced by sitting IHG and by changing postures from sitting to standing was not significantly different from the pressor response to standing IHG. These data indicate that, under physiological conditions, cardiopulmonary baroreflexes do not exert a significant role in modulating the reflex pressor drive from muscles during isometric exercise in healthy humans. 相似文献
103.
N19 polyepitope as a carrier for enhanced immunogenicity and protective efficacy of meningococcal conjugate vaccines 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Baraldo K Mori E Bartoloni A Petracca R Giannozzi A Norelli F Rappuoli R Grandi G Del Giudice G 《Infection and immunity》2004,72(8):4884-4887
N19, a string of human universal CD4 T-cell epitopes from various pathogen-derived antigens, was shown to exert a stronger carrier effect than CRM197 for the induction of anti-group C Neisseria meningitidis capsular polysaccharide (MenC), after immunization of mice with various dosages of N19-MenC or CRM-MenC conjugate vaccines. After two immunizations, the N19-based construct induced anti-MenC antibody and protective bactericidal antibody titers higher than those induced by three doses of the CRM-MenC conjugate and required lower amounts of conjugate. N19-based conjugates are superior to CRM-based conjugates to induce protective immune responses to MenC conjugates. 相似文献
104.
Genes and translocations involved in POF 总被引:14,自引:0,他引:14
105.
Giuliano M Bellavia G Lauricella M D'Anneo A Vassallo B Vento R Tesoriere G 《International journal of molecular medicine》2004,13(4):565-571
A potent inhibitor of serine/threonine kinases, staurosporine exerts antiproliferative and apoptotic effects in many cancer cells, although the exact mechanism of its action is still unclear. This study examines the effects of staurosporine on Chang liver cells, an immortalized non-tumor cell line, in comparison with those caused in HuH-6 and HepG2 cells, two human hepatoma cell lines. Our results provide evidence that staurosporine promotes apoptosis in Chang liver cells as observed by flow cytometric analysis and acridine orange/ethidium bromide staining. The effect appeared already after 8 h of treatment and increased with treatment time and dose. After 48 h of exposure to 200 nM staurosporine clear apoptotic signs were observed in about 50% of the cells. Western blotting analysis showed that in Chang liver cells staurosporine induced a marked decrease in the levels of the antiapoptotic factors Bcl-2 (-75%) and Bcl-XL (-50%). Staurosporine also caused loss of mitochondrial transmembrane potential, release of cytochrome c from mitochondria and activation of caspase-3. The involvement of caspases in staurosporine-induced cell death was also suggested by the observation that the addition of z-VAD-fmk, a general inhibitor of caspases, suppressed apoptosis. In HuH-6 and HepG2 cells treatment with staurosporine induced the arrest of cells in G2/M phase of cell cycle. This effect was not modified by z-VAD-fmk and was not accompanied by the appearance of biochemical signs of apoptosis. We conclude that staurosporine induced apoptosis in Chang liver cells by a mitochondria-caspase-dependent pathway which was closely correlated with a decrease in Bcl-2 and Bcl-XL levels, while in HuH-6 and HepG2 hepatoma cells the drug caused only an antiproliferative effect. 相似文献
106.
Rolla G Nebiolo F Marsico P Guida G Bigo P Riva G Zanotta S 《International archives of allergy and immunology》2004,135(4):293-295
BACKGROUND: The European tick, Argas reflexus, is an urban pest parasitizing urban pigeons and may cause a wide range of allergic reactions. METHODS: Specific IgE to A. reflexus, SDS-PAGE and IgE immunoblotting, performed with tick extract, were carried out in the sera of 6 patients who reported allergic reactions after tick bite. RESULTS: Specific IgE to A. reflexus (RAST class ranging from 1 to 3) were detected in the sera of 6 patients who reported allergic reactions (urticaria and angioedema in 2 and anaphylaxis in the other 4 patients) after tick bite. IgE reactivity to two bands of 22 and 40 kDa were identified in the patient sera. CONCLUSIONS: Allergy to A. reflexus has to be considered in allergic patients living in buildings where pigeons have their nests. The powerful sensitizing property of tick allergen is underlined by the observation that none of our patients was atopic. 相似文献
107.
Comparison of LCx with other current viral load assays for detecting and quantifying human immunodeficiency virus type 1 RNA in patients infected with the circulating recombinant form A/G (CRF02)
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)
Amendola A Bordi L Angeletti C Girardi E Ippolito G Capobianchi MR 《Journal of clinical microbiology》2004,42(2):811-815
LCx was compared to other assays in measuring human immunodeficiency virus type 1 (HIV-1) CRF02 viremia. LCx showed significant but low correlation with the other methods. Values of <2.60 log(10) cp/ml were observed in 29.6% of specimens with LCx and in only 14.8% with bDNA and PCR, suggesting suboptimal performance of LCx with CRF02. 相似文献
108.
Genotype-phenotype relationship in human ATP6i-dependent autosomal recessive osteopetrosis 总被引:5,自引:0,他引:5
下载免费PDF全文
![点击此处可从《The American journal of pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Taranta A Migliaccio S Recchia I Caniglia M Luciani M De Rossi G Dionisi-Vici C Pinto RM Francalanci P Boldrini R Lanino E Dini G Morreale G Ralston SH Villa A Vezzoni P Del Principe D Cassiani F Palumbo G Teti A 《The American journal of pathology》2003,162(1):57-68
Autosomal-recessive osteopetrosis is a severe genetic disease caused by osteoclast failure. Approximately 50% of the patients harbor mutations of the ATP6i gene, encoding for the osteoclast-specific a3 subunit of V-ATPase. We found inactivating ATP6i mutations in four patients, and three of these were novel. Patients shared macrocephaly, growth retardation and optic nerve alteration, osteosclerotic and endobone patterns, and high alkaline phosphatase and parathyroid hormone levels. Bone biopsies revealed primary spongiosa lined with active osteoblasts and high numbers of tartrate-resistant acid phosphatase (TRAP)-positive, a3 subunit-negative, morphologically unremarkable osteoclasts, some of which located in shallow Howship lacunae. Scarce hematopoietic cells and abundant fibrous tissue containing TRAP-positive putative osteoclast precursors were noted. In vitro osteoclasts were a3-negative, morphologically normal, with prominent clear zones and actin rings, and TRAP activity more elevated than in control patients. Podosomes, alphaVbeta3 receptor, c-Src, and PYK2 were unremarkable. Consistent with the finding in the bone biopsies, these cells excavated pits faintly stained with toluidine blue, indicating inefficient bone resorption. Bone marrow transplantation was successful in all patients, and posttransplant osteoclasts showed rescue of a3 subunit immunoreactivity. 相似文献
109.
A Raman microprobe spectroscopy characterization of microscopic fracture mechanisms is presented for a natural hydroxyapatite material (cortical bovine femur) and two synthetic hydroxyapatite-based materials with biomimetic structures-a hydroxyapatite skeleton interpenetrated with a metallic (silver) or a polymeric (nylon-6) phase. In both the natural and synthetic materials, a conspicuous amount of toughening arose from a microscopic crack-bridging mechanism operated by elasto-plastic stretching of unbroken second-phase ligaments along the crack wake. This mechanism led to a rising R-curve behavior. An additional micromechanism, responsible for stress relaxation at the crack tip, was recognized in the natural bone material and was partly mimicked in the hydroxyapatite/silver composite. This crack-tip mechanism conspicuously enhanced the cortical bone material resistance to fracture initiation. A piezo-spectroscopic technique, based on a microprobe measurement of 980 cm(-1) Raman line of hydroxyapatite, enabled us to quantitatively assess in situ the microscopic stress fields developed during fracture both at the crack tip and along the crack wake. Using the Raman piezo-spectroscopy technique, toughening mechanisms were assessed quantitatively and rationally related to the macroscopic fracture characteristics of hydroxyapatite-based materials. 相似文献
110.
Human Cytomegalovirus and Human Umbilical Vein Endothelial Cells: Restriction of Primary Isolation to Blood Samples and Susceptibilities of Clinical Isolates from Other Sources to Adaptation
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)
Giuseppe Gerna Elena Percivalle Antonella Sarasini M. Grazia Revello 《Journal of clinical microbiology》2002,40(1):233-238
In immunocompromised patients with disseminated infection, human cytomegalovirus (HCMV) is widespread in the microvascular endothelium of multiple organs. Human umbilical vein endothelial cells (HUVEC) were used in parallel to human embryonic lung fibroblasts (HELF) to recover HCMV from blood samples of immunocompromised patients. Using the shell vial technique, comparable median numbers of p72-positive HUVEC and HELF cells were found with the 26 HCMV-positive buffy coat samples out of 150 examined. Analysis of other clinical samples inoculated as controls revealed, in the presence of highly infected HELF monolayers, either the presence of very few infected HUVEC with urine specimens (n = 10 samples) or the lack of infected HUVEC with throat washes (n = 3) or amniotic fluid samples (n = 2). Thus, peripheral blood leukocytes (PBL) appear essential for primary isolation of HCMV in HUVEC. In this respect, HCMV strains, recovered from clinical samples other than buffy coats in HELF only, could be readily adapted to growth in HUVEC by coculturing PBL from healthy blood donors with infected HELF and then inoculating infected PBL onto HUVEC. Recently elucidated mechanisms of interaction of leukocytes and HUVEC with bidirectional transfer of virus seem to provide the basis for the restriction of HCMV primary isolation in HUVEC to blood samples. However, virus strains recovered from only HELF could be adapted to growth in HUVEC when inoculated with HELF-derived (either cell-associated or cell-free) HCMV strains upon primary isolation. In conclusion, due to the in vitro selection of virus variants provided with both PBL tropism and HUVEC tropism, HCMV recovery in HUVEC is PBL mediated and substantially restricted to blood samples. Lack of HCMV recovery in HUVEC from clinical samples other than blood leads to the assumption that epithelial cells, such as urinary, amniotic, or pharyngeal cells, do not possess adequate adhesion molecules to establish close contacts with HUVEC. 相似文献