全文获取类型
收费全文 | 248165篇 |
免费 | 23417篇 |
国内免费 | 15074篇 |
专业分类
耳鼻咽喉 | 2549篇 |
儿科学 | 3849篇 |
妇产科学 | 1494篇 |
基础医学 | 18606篇 |
口腔科学 | 4411篇 |
临床医学 | 29020篇 |
内科学 | 27594篇 |
皮肤病学 | 2859篇 |
神经病学 | 8581篇 |
特种医学 | 10402篇 |
外国民族医学 | 26篇 |
外科学 | 25532篇 |
综合类 | 60044篇 |
现状与发展 | 67篇 |
一般理论 | 10篇 |
预防医学 | 25605篇 |
眼科学 | 3568篇 |
药学 | 28297篇 |
300篇 | |
中国医学 | 19851篇 |
肿瘤学 | 13991篇 |
出版年
2024年 | 884篇 |
2023年 | 2691篇 |
2022年 | 6948篇 |
2021年 | 9667篇 |
2020年 | 8076篇 |
2019年 | 5231篇 |
2018年 | 5570篇 |
2017年 | 6930篇 |
2016年 | 5882篇 |
2015年 | 9949篇 |
2014年 | 12960篇 |
2013年 | 15098篇 |
2012年 | 22091篇 |
2011年 | 23739篇 |
2010年 | 20423篇 |
2009年 | 18083篇 |
2008年 | 19333篇 |
2007年 | 18873篇 |
2006年 | 16767篇 |
2005年 | 13848篇 |
2004年 | 10190篇 |
2003年 | 8950篇 |
2002年 | 7266篇 |
2001年 | 5625篇 |
2000年 | 4274篇 |
1999年 | 2014篇 |
1998年 | 901篇 |
1997年 | 858篇 |
1996年 | 632篇 |
1995年 | 562篇 |
1994年 | 495篇 |
1993年 | 321篇 |
1992年 | 260篇 |
1991年 | 221篇 |
1990年 | 160篇 |
1989年 | 136篇 |
1988年 | 114篇 |
1987年 | 102篇 |
1986年 | 112篇 |
1985年 | 61篇 |
1984年 | 65篇 |
1983年 | 39篇 |
1982年 | 52篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 19篇 |
1975年 | 16篇 |
1973年 | 16篇 |
1972年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Masafumi Ogawa Yasuhiro Magata Yasuomi Ouchi Hidenao Fukuyama Hiroshi Yamauchi Jun Kimura Yoshiharu Yonekura Junji Konishi 《Brain research》1994,650(2):249-252
The effect of the cholinergic blocker, scopolamine on the cerebral blood flow (CBF) response to vibrotactile stimulation of a fore paw was studied using high-resolution positron emission tomography and H215O in 5 pentobarbital-anesthetized cats. Before scopolamine injection, the CBF response to the stimulation was found in the contralateral somatosensory cortex (mean ratio (contralateral/ipsilateral) control: stimulated1.02 ± 0.02: 1.17 ± 0.05; P < 0.01). After intravenous injection of scopolamine (0.35 mg/kg), the CBF response was abolished. However, the cerebral metabolic rate of glucose (CMRGlu) response to the same stimulation was unchanged after scopolamine injection in the same cats. We concluded that scopolamine abolishes the CBF response but not neuronal response to stimulation. We suggest that cholinergic mechanisms may play an important role for mediating CBF coupling to neuronal activity during physiological stimulation. 相似文献
992.
乳腺囊性增生病癌变过程中部分因素变化的意义 总被引:3,自引:0,他引:3
检测乳腺囊性增生病(FCD)经不典型增生到癌变部分因素的变化。结果提示:从因明显FCD症状活检至癌变为2~10年;从Ⅱ级以上不典型增生到临床癌变需2~7年;癌变率为3.1%。FCD患者存在性激素分泌调控失常,血浆雌激素和催乳素含量增加,导致上皮细胞增生。乳腺一般性增生细胞的DNA含量和超微结构与正常乳腺上皮细胞相似;无肿瘤相关抗原及异常基因产物表达。而发生在一般性增生基础上的不典型增生则呈现细胞基因物质DNA含量增加,部分为超4C的多倍体细胞;同时出现细胞膜和细胞核超微结构异常;雌激素受体含量增加,对性激素的依赖性和敏感性增强;部分不典型增生细胞出现胚胎性肿瘤相关抗原和异常基因产物表达。随不典型增生程度加重至乳腺癌,上述诸因素的变化趋势具有明显规律性。提示FCD上皮细胞从一般性增生经不典型增生至乳腺癌为细胞生物学连续逐渐变化的过程。部分不典型增生细胞中具有癌倾向的细胞生物学行为异常和表型变化与乳腺癌发生密切相关。细胞核DNA含量等异常变化及程度可作为乳腺癌前病变发展程度的客观标志 相似文献
993.
随着工业贮存期的延长,啤酒酵母细胞的存活率及对葡萄糖连续磷酸化的速率迅速下降,1,6-二磷酸果糖在发酵液中的浓度由贮存前的75g/L降至贮存2个星期时的30g/L。 相似文献
994.
包裹胰岛微囊的物理性能研究 总被引:2,自引:0,他引:2
用3%海藻酸钠及2.2%CaCl_2所制备的微囊在高流速及高浓度的蔗糖溶液冲击下未见破裂,且微囊包裹活细胞经过二小时的剧烈搅拌,亦无损漏。改进法所制备的微囊具有良好的机械强度,其物理性能已达到临床进行包膜胰岛移植治疗糖尿病的要求。 相似文献
995.
Masahiko Kawaguchi Masakazu Kuro Hisatoshi Ohsumi Toshito Nakajima Yoshihiro Kuriyama Jun Karasawa 《Journal of anesthesia》1994,8(1):60-63
We assessed the local cerebral blood flow (LCBF) in 40 patients under fentanyl-diazepam anesthesia. The measurement of LCBF
was made using 50%–70% stable xenon with 20 min of inhalation interval and a shuttle method for computed tomography imaging.
All patients were anesthetized with 5.95±1.76 μg·kg−1 fentanyl and 0.22±0.07 mg·kg−1 diazepam under mechanical ventilation during CBF measurement. The values and distribution of LCBF on non-affected hemisphere
appeared to be unaltered by fentanyldiazepam anesthesia. We also assessed the cerebral carbon dioxide reactivity in 6 patients.
The cerebral carbon dioxide reactivity, expressed as percentage change in LCBF per unit change in arterial carbon dioxide
partial pressure, was 5.39±1.07, and there were no significant differences of reactivity among regions studied. In conclusion,
we showed reference values of LCBF and carbon dioxide reactivity, measured by stable xenon-enhanced computed tomography, in
patients under fentanyl-diazepam anesthesia. Carbon dioxide reactivity was preserved in all regions including gray matter,
white matter, and basal ganglia. 相似文献
996.
Ikuo Saiki Jun Murataxd Junya Yoneda Hideo Kobayashi Ichiro Azuma 《International journal of cancer. Journal international du cancer》1994,56(6):867-873
We have examined the influence of fibroblasts on the invasive and migratory potential of highly metastatic melanoma B16-BL6 and weakly metastatic B16-FI cells in vitro. Co-culture of B16-BL6 cells with a fibroblast monolayer without cellular contact in a Transwell chamber more effectively induced tumor-cell invasion into Matrigel basement membrane than co-culture of B16-FI cells with a fibroblast monolayer. The activity was closely correlated with the chemotactic migration of tumor cells toward the fibroblast monolayer. We also found that the conditioned medium (CM) from the co-culture of fibroblasts with B16-BL6 cells without cellular contact, i.e., CM (B16-BL6/fibroblast), rather than from co-culture with B16-FI cells, could potentially promote the migration of tumor cells of both types. Tumor cells did not chemotactically migrate to the CM (B16-BL6), CM (B16-FI) or CM (fibroblast). Antibodies against TGF-β1 or FN almost completely abolished the chemotactic migration of B16-BL6 cells to the CM (B16-BL6/fibroblast) or CM (TGF-β1 -treated fibroblast) when these antibodies were c-incubated with fibroblasts and either B16-BL6 or TGF-β1. In contrast, the anti-EGF antibody did not show any inhibitory effects. Analysis of amounts of TGF-β1 or FN in various CM using ELISA plates, and using their specific antibodies, revealed that the concentration of TGF-β1 in the CM (B16-BL6) was slightly higher than in the CM (B16-FI), and the amount of FN in the CM (B16-BL6/fibroblast) was twice as high as in the CM (B16-FI /fibroblast). These results suggest that TGF-β1 released from B16-BL6 cells can stimulate fibroblasts to produce FN; consequently, the tumor cells were able to chemotactically migrate toward the released FN, and the differences in invasive and migratory activities towards fibroblasts in B16-BL6 and B16-FI cells may in part be due to the amounts of TGF-β1 from tumor cells and of FN from TGF-β1 -stimulated fibroblasts. 相似文献
997.
雷公藤氯内酯醇对大鼠异位心脏移植免疫抑制作用的实验研究 总被引:2,自引:0,他引:2
本研究应用纯系大鼠(Lou→F344)心脏移植模型,比较分析了CsA和不同剂量T4治疗组的移植心脏存活时间、病理损害计分以及移植受体大鼠脾单个核细胞IL-2生成活性和血清sIL-2R水平,证实T4可明显延长移植心脏存活时间和减少移植排异反应程度。此研究结果表明T4具有较强的抗移植排异作用。 相似文献
998.
高效液相色谱法测定微量耳血中头孢他定的浓度 总被引:2,自引:0,他引:2
本文介绍采取微量耳血以高效液相色谱法测定头孢他定(Ceftazidime)的血药浓度。血样经6%高氯酸沉淀蛋白,流动相为含25%甲醇的0.05mol/L醋酸铵溶液,以冰醋酸调节pH值至4~5,检测波长为254nm,内标物为头孢唑啉(Cefazolin)。经对家兔采取微量耳血测定其血药浓度,可知头孢他定为二室模型,T_1/2α为0.18±0.05h,T_1/2β为1.75±0.07h。并对3名住院病人静脉注射1g头孢他定后定时分别取微量耳血进行分析,所得结果与文献基本一致。本文方法简便、快速,结果令人满意。 相似文献
999.
人PD-L2基因克隆及其在大肠杆菌中的表达 总被引:1,自引:1,他引:0
目的 克隆人PD-L2基因并构建PD-L2胞外区的原核表达载体,在大肠杆菌中进行表达。方法 以RT-PCR方法从活化的人外周血单个核细胞总RNA中克隆PD-L2基因的cDNA,构建PD-L2胞外区的原核表达载体,在大肠杆菌BL21(ED3)中进行表达并鉴定。结果 克隆到PD-L2基因cDNA编码区全长序列,经DNA测序证明其与已报道的序列一致。进而构建了PD-L2胞外区的原核表达载体,并在大肠杆菌表达,免疫印迹分析表明在IPTG诱导后表达PD-L2胞外区蛋白,相对分子质量Mr为22000,与理论值大小相符。结论 成功克隆PD-L2基因,其胞外区蛋白在大肠杆菌中获得表达,为进一步研究PD-L2功能提供了条件。 相似文献
1000.
Jun Gu Yang O Huh Feng Jiang Nancy P Caraway Jorge E Romaguera Tanweer M Zaidi Ricardo L Fernandez Huazhong Zhang Issa F Khouri Ruth L Katz 《Modern pathology》2004,17(5):553-560
Mantle cell lymphoma is non-Hodgkin's B-cell lymphoma characterized by the t(11;14)(q13;q32) translocation. Peripheral blood involvement of mantle cell lymphoma is usually associated with a poor prognosis and therefore, its identification is clinically important. In this study, we performed cyclin D1/IgH-probe fusion fluorescence in situ hybridization analysis on 223 peripheral blood samples: 185 from 125 mantle cell lymphoma patients, and 38 normal controls. The cutoff values for the test were established using normal controls. Flow cytometry on peripheral blood and corresponding bone marrow samples was used to evaluate this test. In all, 26% of the 185 peripheral blood samples and 27% of the 161 corresponding bone marrow samples were flow cytometry positive for mantle cell lymphoma. The mean numbers of single and- double-fusion signals and the mean number of CD5/CD19-positive cells, absolute blood lymphocyte count, and white blood cell count were significantly higher in peripheral blood and corresponding bone marrow samples with mantle cell lymphoma-positive flow cytometry. Double-fusion signals were more specific than single-fusion ones. Fluorescence in situ hybridization was far more likely to be positive for mantle cell lymphoma when the peripheral blood and the corresponding bone marrow samples had positive flow cytometry results or morphology (P<0.01). Our study indicates that cyclin D1/IgH-fusion fluorescence in situ hybridization analysis could be used to determine the presence and character of circulating mantle cell lymphoma cells in peripheral blood, thus enhancing our ability to evaluate leukemic mantle cell lymphoma and minimum residual disease. 相似文献