全文获取类型
收费全文 | 24223篇 |
免费 | 1481篇 |
国内免费 | 161篇 |
专业分类
耳鼻咽喉 | 293篇 |
儿科学 | 754篇 |
妇产科学 | 709篇 |
基础医学 | 2423篇 |
口腔科学 | 707篇 |
临床医学 | 2029篇 |
内科学 | 5296篇 |
皮肤病学 | 507篇 |
神经病学 | 1108篇 |
特种医学 | 821篇 |
外国民族医学 | 9篇 |
外科学 | 4310篇 |
综合类 | 707篇 |
现状与发展 | 1篇 |
一般理论 | 21篇 |
预防医学 | 1677篇 |
眼科学 | 711篇 |
药学 | 2125篇 |
中国医学 | 156篇 |
肿瘤学 | 1501篇 |
出版年
2023年 | 342篇 |
2022年 | 1004篇 |
2021年 | 1404篇 |
2020年 | 739篇 |
2019年 | 940篇 |
2018年 | 1248篇 |
2017年 | 753篇 |
2016年 | 777篇 |
2015年 | 865篇 |
2014年 | 1076篇 |
2013年 | 1323篇 |
2012年 | 1819篇 |
2011年 | 1865篇 |
2010年 | 960篇 |
2009年 | 790篇 |
2008年 | 1168篇 |
2007年 | 1259篇 |
2006年 | 1094篇 |
2005年 | 946篇 |
2004年 | 897篇 |
2003年 | 755篇 |
2002年 | 696篇 |
2001年 | 329篇 |
2000年 | 317篇 |
1999年 | 292篇 |
1998年 | 157篇 |
1997年 | 116篇 |
1996年 | 102篇 |
1995年 | 106篇 |
1994年 | 70篇 |
1993年 | 54篇 |
1992年 | 130篇 |
1991年 | 121篇 |
1990年 | 114篇 |
1989年 | 103篇 |
1988年 | 98篇 |
1987年 | 94篇 |
1986年 | 99篇 |
1985年 | 85篇 |
1984年 | 71篇 |
1983年 | 87篇 |
1982年 | 35篇 |
1981年 | 45篇 |
1980年 | 32篇 |
1979年 | 78篇 |
1978年 | 44篇 |
1977年 | 52篇 |
1976年 | 41篇 |
1975年 | 44篇 |
1974年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A case of urinary tract infection and bacteremia caused by CDC group Vd biovar 2 in a 23-year-old woman with Hodgkin's disease is described. This is the first report of CDC group Vd biovar 2 isolated from a clinical specimen and considered as a pathogen. Detailed antimicrobial susceptibility data are presented. 相似文献
102.
Inherited prothrombotic defects in Budd-Chiari syndrome and portal vein thrombosis: a study from North India 总被引:5,自引:0,他引:5
Bhattacharyya M Makharia G Kannan M Ahmed RP Gupta PK Saxena R 《American journal of clinical pathology》2004,121(6):844-847
We studied 57 patients with Budd-Chiari syndrome (BCS) and 48 with portal vein thrombosis (PVT) for underlying inherited prothrombotic defects such as protein C, protein S, and antithrombin III deficiencies. Genetic mutations for factor V Leiden, prothrombin gene 20210A, and methyltetrahydrofolate reductase (MTHFR) C677T were studied in 29 patients in each group. Inherited prothrombotic defects were detected in 16 (28%) of 57 patients with BCS and 7 (15%) of 48 patients with PVT. Factor V Leiden mutation was the most common prothrombotic defect in BCS (5/29 [17%]) followed by protein C deficiency (7/57 [12%]) and protein S deficiency (4/57 [7%]), whereas in PVT, protein C deficiency was the most common inherited prothrombotic defect (4/48 [8%]) followed by protein S deficiency (2/48 [4%]). The factor V Leiden mutation was detected in only 1 (3%) of 29 cases of PVT. The heterozygous MTHFR C677T mutation was detected in 7 (24%) of 29 patients with BCS and 6 (21%) of 29 patients with PVT. Antithrombin III deficiency, homozygous MTHFR C677T mutation, and prothrombin G20210A mutation were not detected in any patients. 相似文献
103.
Elaine Tierney Irena Bukelis Richard E Thompson Khalid Ahmed Alka Aneja Lisa Kratz Richard I Kelley 《American journal of medical genetics. Part B, Neuropsychiatric genetics》2006,(6):666-668
Although Smith-Lemli-Opitz Syndrome (SLOS), a genetic condition of impaired cholesterol biosynthesis, is associated with autism [Tierney et al., 2001; Am J Med Genet 98:191-200.], the incidence of SLOS and other sterol disorders among individuals with autism spectrum disorders (ASD) is unknown. This study investigated (1) the incidence of biochemically diagnosed SLOS in blood samples from a cohort of subjects with ASD from families in which more than one individual had ASD and (2) the type and incidence of other sterol disorders in the same group. Using gas chromatography/mass spectrometry, cholesterol, and its precursor sterols were quantified in 100 samples from subjects with ASD obtained from the Autism Genetic Resource Exchange (AGRE) specimen repository. Although no sample had sterol levels consistent with SLOS, 19 samples had total cholesterol levels lower than 100 mg/dl, which is below the 5th centile for children over age 2 years. These findings suggest that, in addition to SLOS, there may be other disorders of sterol metabolism or homeostasis associated with ASD. 相似文献
104.
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
105.
106.
107.
Reactive oxygen species (ROS), represented by superoxide, hydrogen peroxide and hydroxyl radicals, have been implicated in many diseases including cancer. ROS have been known to play an important role in the initiation and promotion of multistep carcinogenesis. The cellular antioxidants play a crucial role in protection against neoplastic disease. However, very little is known about the antioxidant defense in cervical carcinoma. This is addressed in the present study. Lipid peroxides, glutathione content and the activities of antioxidant enzymes, together with vitamin C and E content, were estimated in patients who had carcinoma of the cervix, and the values were compared with those of normal women. The results showed a remarkable reduction in the content of glutathione, vitamin E and C. Activities of glutathione peroxidase and superoxide dismutase were also reduced in cervical cancer compared to normal controls (P < 0.001). This reduction was more marked in late stages (III, IV) than in early stages (I, II) (P < 0.001). Glutathione was reduced more in poorly differentiated tumors (grade III) than in well and moderately differentiated ones (grade I, II) (P < 0.05). Levels of lipid peroxides were found to be significantly higher in malignant than in normal tissue samples and their levels were correlated with advanced clinical stage (P < 0.001). Our results suggest impaired antioxidant status in carcinoma of the cervix. This impairment is related to tumor progression. 相似文献
108.
Khaliq A Dunk C Jiang J Shams M Li XF Acevedo C Weich H Whittle M Ahmed A 《Laboratory investigation; a journal of technical methods and pathology》1999,79(2):151-170
Early placental development occurs in an environment of relative hypoxia. Hypoxia promotes angiogenesis and up-regulates vascular endothelial growth factor (VEGF) expression while it down-regulates placenta growth factor (PIGF) that possess 53% homology with VEGF. Morphological studies show poor placental vascular development and an increase in the mitotic index of cytotrophoblasts in intrauterine growth restriction (IUGR). We hypothesized that the reported relatively high oxygen level in the intervillous space in contact with IUGR placental villi will limit angiogenesis by changes in VEGF and PIGF expression and function. Western immunoblot analysis demonstrates a diametric expression of PIGF and VEGF proteins throughout pregnancy with PIGF levels increasing and VEGF levels decreasing, consistent with placental oxygenation. In IUGR placentae, the ratio of PIGF/GAPDH mRNA was increased by 2.3-fold (p < 0.03) and PIGF protein levels were also increased, (p < 0.05) as compared with gestationally-matched normal placentae. PIGF mRNA and protein were localized to the trophoblast bilayer and villous mesenchyme of the human placenta throughout gestation. In vitro studies demonstrated that increasing oxygen tension (hyperoxia) up-regulated PIGF protein in term placental villous explants, whereas hypoxic culture of a term trophoblast choriocarcinoma cell line (BeWo) down-regulated PIGF mRNA and protein and VEGFR-1 (Flt-1) autophosphorylation. The addition of PIGF-1 to a spontaneously transformed first trimester cytotrophoblast cell line stimulated DNA synthesis while PIGF-2 had little effect. VEGF and PIGF exert their biological actions by means of a common receptor VEGFR-1. In the first trimester trophoblast cells, PIGF-1 increased the association of phosphorylated extracellular signal-related kinase (ERK) with VEGFR-1 immunoprecipitates while both PIGF-1 and PIGF-2 also potentiated endogenous VEGF mediated association of phosphorylated extracellular related kinase (ERK) with VEGFR-2 (KDR). More importantly, the addition of PIGF-1 had little effect while PIGF-2 inhibited cell growth in cultured endothelial cells derived from human umbilical vein. Nitric oxide (NO) is reported to promote angiogenesis and PIGF-2 inhibited the basal release of NO from the first trimester trophoblast. The tissue expression and functional studies support the hypothesis of "placental hyperoxia" in early-onset IUGR because hypoxia down-regulates trophoblast PIGF levels, PIGF expression is increased in IUGR, and PIGF-2 inhibits endothelial cell growth. Taken together, these changes provide a cellular explanation for the observed poor angiogenesis in the pathogenesis of IUGR and show that the two PIGF isoforms may modulate trophoblast and endothelial cell function differently, possibly through potentiation of VEGF mediated activation of VEGF-2. 相似文献
109.
Chromosomal aberrations and micronucleus frequency in nurses occupationally exposed to cytotoxic drugs 总被引:4,自引:1,他引:4
Anwar Wagida A.; Salama Somaia I.; Serafy Mostafa M.EI; Hemida Samia A.; Hafez Ahmed S. 《Mutagenesis》1994,9(4):315-317
In this study, we evaluated the effect of low level occupationalexposure of nurses in a medical oncology unit in Cairo, Egypt,to anticancer drugs. Twenty nurses who constantly handled thesedrugs and 20 controls, matched according to age and sex, wereexamined. Metaphase chromosomes were studied. Percentages ofmetaphases with chromosomal aberrations were significantly higher(P < 0.001) in the exposed group (6.1 ± 2.7) versusthe controls (2.6 ± 1.6). The detected chromosomal aberrationswere in the form of chromatid gaps, chromatid breaks and acentricfragments. Micronucleated peripheral blood lymphocytes werealso analyzed in cytochalasin B treated binucleated lymphocytes.There was significant increase in cells with micronuclei (P< 0.001) in nurses (10.05 ± 4.71) in comparison tothe matched control (5.42 ± 2.22) (P < 0.001). Nursesexposed to the cytotoxic drugs for 相似文献
110.