首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   291367篇
  免费   24327篇
  国内免费   10606篇
耳鼻咽喉   2308篇
儿科学   4416篇
妇产科学   4438篇
基础医学   52959篇
口腔科学   6738篇
临床医学   20804篇
内科学   39234篇
皮肤病学   4306篇
神经病学   20797篇
特种医学   8653篇
外国民族医学   28篇
外科学   24163篇
综合类   40669篇
现状与发展   50篇
一般理论   10篇
预防医学   17663篇
眼科学   5416篇
药学   35218篇
  71篇
中国医学   15680篇
肿瘤学   22679篇
  2024年   476篇
  2023年   3471篇
  2022年   6823篇
  2021年   10797篇
  2020年   9353篇
  2019年   9044篇
  2018年   9247篇
  2017年   10324篇
  2016年   10870篇
  2015年   11008篇
  2014年   14382篇
  2013年   19955篇
  2012年   15766篇
  2011年   18814篇
  2010年   13373篇
  2009年   13211篇
  2008年   14888篇
  2007年   15884篇
  2006年   14828篇
  2005年   13347篇
  2004年   11340篇
  2003年   9838篇
  2002年   7659篇
  2001年   6742篇
  2000年   5689篇
  1999年   4774篇
  1998年   3986篇
  1997年   3985篇
  1996年   3638篇
  1995年   3355篇
  1994年   3168篇
  1993年   2676篇
  1992年   2363篇
  1991年   2229篇
  1990年   1937篇
  1989年   1687篇
  1988年   1547篇
  1987年   1401篇
  1986年   1278篇
  1985年   1864篇
  1984年   1556篇
  1983年   1142篇
  1982年   1300篇
  1981年   1033篇
  1980年   967篇
  1979年   791篇
  1978年   512篇
  1977年   427篇
  1976年   404篇
  1975年   240篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Data on the prevalence of antibody to hepatitis C virus among 278 subjects in an institution for the mentally handicapped were analysed by risk factors. A prevalence of 4% was found, higher than blood donors belonging to the same area (1.4%). No differences in prevalence with regard the length of residence, age, sex, degree of retardation or for presence of HBV markers were observed.  相似文献   
992.
Sry监测体外扩增造血细胞植入效果的实验研究   总被引:2,自引:0,他引:2  
目的:探讨Y染色体性别决定基因(Sry)作为评价和追踪造血细胞移植后植入状态检测指标的可行性。方法:根据Sry DNA序列设计引物及制备探针,然后进行PCR检测、斑点杂交和原位杂交.动态追踪经不同条件下体外扩增的纯系雄性小鼠BMMNC回输至雌性小鼠后的植入状态。结果:PCR结果显示在各移植组小鼠的骨髓有核细胞、脾细胞及外周血白细胞中均有Y染色体特异性序列的存在;斑点杂交结果显示在各回输组间并无明显差别,但用脾脏组织作原位杂交的结果则发现基质细胞支持扩增回输组的阳性颗粒数目与输注新鲜细胞组相似,但略少于雄性小鼠;而输注细胞因子扩增细胞实验组小鼠则明显少于雄性动物的阳性对照标本和基质细胞支持扩增回输组。结论:(1)经重复检测表明上述方法的重复性好,结果可信.可作为检测性别不同时造血干细胞移植效果的一种检测手段;(2)证实基质细胞支持下的体外扩增的造血细胞具有较好的植入能力。  相似文献   
993.
为探讨急性心肌梗死和疑为心梗病人血中 c Tn I的敏感性和特异性 ,采用金标法对 5 2例就诊病人测定其血中 c Tn- 和酶学法测定 CK- MB两个指标 ,结果发现急性心肌梗死组病人血中的 c Tn- 敏感度高于 CK- MB,但二者无显著性差异 ;而疑为心梗病人血中的 c Tn- 敏感度高于 CK- MB且具有显著的特异性。c Tn- 的测定对急性心肌梗死病人的诊断和治疗具有特别重要的意义  相似文献   
994.
目的 :探讨内皮素 (ET)、在新生儿缺氧缺血性脑病 (HIE)中的作用及与肺功能关系。方法 :将 4 2例 HIE患儿按病情分为轻、中、重三组 ,各组均在入院后第 2天采用婴儿体描箱进行潮气呼吸分析、有效气道阻力及功能残气量等肺功能测定同时用放射免疫法测定血浆 ET水平。结果 :中、重度 HIE组血浆 ET水平均高于轻度组及对照组 ;中、重度HIE组肺功能测定提示 TPTEF/ TE、VPEF/ VE、PEF的下降。重度 HIE组潮气量下降 ,有效气道阻力增高。结论 :血浆ET水平增高与 HIE病情的严重程度相一致 ,肺功能检测指标可以解释血浆 ET水平的增高在新生儿中、重度 HIE发生肺动脉高压及急性肺损伤中起的作用 ,对 HIE临床治疗有一定的指导作用  相似文献   
995.
Summary In a nationwide incident case-referent study stepwise univariate analysis has revealed several risk determinants for childhood diabetes mellitus. In a multivariate analysis we have determined the set of risk determinants that would independently predict childhood Type 1 (insulin-dependent) diabetes. Possible interactions between the risk determinants and differences in risk profiles with different ages at onset were also examined. Reported familial insulin-treated and non-insulin-treated diabetes were significant risk factors in all age groups, as was also a low frequency of milk intake. The frequency of infections and a high intake of foods rich in nitrosamine tended to interact (OR 11.8, p=0.053) indicating a synergistic effect. A Cox regression analysis revealed that stressful life events during the last year was the only variable that tended to affect the age at onset (p=0.055). This indicated that psychological stress may rather precipitate than induce Type 1 diabetes. A short breast-feeding duration (OR=3.81), and an increased body height (OR=3.82) contributed significantly to the predictive model in only the youngest age group (0–4 years). An increased frequency of infections in the year preceding onset (OR=2.15) and no vaccination against measles (OR=3.33) contributed significantly to the model only in the age group 5–9 years. Various nutrients had different impacts on the risk of developing Type 1 diabetes in different age groups. It is concluded that in the genetically susceptible child, risk factors which are associated with eating habits, frequency of infections, vaccination status, growth pattern and severe psychological stress affect the risk of developing diabetes independently of each other. The set of risk determinants varies with the age at onset. A high frequency of infections and a high frequency of nitrosamine-rich food intake seem to have a synergistic effect on the risk of developing diabetes in childhood.  相似文献   
996.
培养Wistar大鼠乳鼠的心室肌细胞,向培养基中分别加入浓度为1.56μg/ml至50μg/ml的大豆皂甙,可使心肌细胞群落的自发性搏动呈剂量依赖性抑制。洗脱大豆皂甙或向培养基中再加入10μg/ml肾上腺素均能使自发性搏动恢复。向培养基中加入大豆皂甙5μg/ml使心肌细胞动作电位的波幅、波宽、超射、最大舒张电位、阈电位、最大除极速度等各电参数立即减小。Ca~(2+)80μg/ml能使动作电位的抑制逆转。上述结果表明大豆皂甙对培养的鼠心肌细胞具有钙通道阻滞用。  相似文献   
997.
In addition to estrogen widely used all over the world for the prevention of postmenopausal osteoporosis, calcitonin and vitamin D derivatives are commonly employed to treat established osteoporosis at higher age in Japan. In order to critically assess the usefulness of vitamin D derivatives and calcitonin alone or in combination on the advancement of vertebral deformity at higher age, 32 osteoporotic patients with vertebral deformity with the mean age of 79 were randomly divided into 4 groups with indistinguishable age and severity of the vertebral deformity. Group 1 served as the control without specific medications for osteoporosis. Group 2 was treated with 10 units elcatonin (eel calcitonin derivative) injected intramuscularly twice a week. Group 3 was given 0.75 to 1.5μg/day 1α (OH) vitamin D3 orally. Group 4 was given a combination of treatments used in Groups 2 and 3. In the lateral X-ray film of the spine taken prior to the test and every 6 months thereafter, the shape of the vertebral body T8 through L4 was monitored by measuring the anterior, central and posterior heights. Decrease of the vertebral height ratio; anterior or middle height/posterior or adjacent intact posterior height, by more than 20% of the original value or from above to below 0.80 both appeared to be inhibited during administration of 1α (OH) vitamin D3. Such effect seems to be augmented by simultaneous administration of elcatonin. Actual decrease of vertebral height ratio values and the per cent fall from the original value significantly less in Groups 3 and 4 than in Group 1. Development of vertebral deformity assessed by the changes of the vertebral height thus appears to decrease during treatment with 1α (OH) vitamin D3 especially together with calcitonin in established osteoporosis.  相似文献   
998.
利用胸导管引流治疗哮喘病的机会,研究了PHA在rIL-2诱导胸导管淋巴细胞成为LAK细胞中的作用。结果表明:PHA和rIL-2共同诱导TDL2周,细胞数量扩增约34倍。同时明显促进了DL的~3H-TdR和~3H-Leucine的参入,较对照组有明显差异(P<0.01)。其中rIL-2 100~1000U/ml和PHA组作用最佳,但PHA和rIL-2的协同作用持续时间短,第6d即开始下降,而且PHA参与诱导的TDL-LAK细胞的杀伤活性有所下降。  相似文献   
999.
Shih  Chung 《Pharmaceutical research》1995,12(12):2041-2048
Purpose. To obtained rate constants from weight-averaged (Mw) or z-averaged (Mz) molecular weights for polymers of Schule-Flory distribution and undergoing random scission. These constants were compared with those obtained by parallel 1HNMR studies. Methods. The hydrolysis of two poly(ortho ester)s were followed by 1HNMR and gel permeation chromatography (GPC). Results. Equations to convert number-averaged (Mn), Mw and Mz into fraction of backbone remaining (fc) were derived. First-order hydrolytic rate constants of two poly(ortho ester)s; DETOSU-HD and DETOSU-CDM were calculated using these relationships. The rate constants calculated from 1HNMR, Mz and Mw were 0.215, 0.218 and 0.182 hr–1, respectively, for DETOSU-CDM and 0.152, 0.086 and 0.038 hr–l for DETOSU-HD. The large discrepancy in the rates determined by 1HNMR and GPC in the latter case was attributed to that the detector response (refractive index) of the monomers was lower than that of the high molecular weight polymer. The difference is small in the case of DETOSU-CDM, and the rates calculated from GPC data were comparable or nearly identical to that obtained from 1HNMR data. Conclusions. Although GPC can yield rapid and valuable kinetic data for the degradation of biodegradable polymers, the system, however, must be carefully calibrated to account for the variations in Mark-Houwink coefficients and in the response of the mass detector between the high and low MW polymers.  相似文献   
1000.
菏泽市城区1008名学龄儿童感觉统合失调调查分析   总被引:5,自引:0,他引:5  
目的:为了解本市的学龄儿童感觉统合失调的发生率及造成感觉统合失调的有关因素。方法:采用北京感觉统合失调评定表,对6-10岁1008名在校儿童进行整群抽样调查,所获数据经χ^2检验。结果:感觉统合失调发生率为35.52%,其中轻率23.4%,重度12.1%,男童发生率为43.08%,女童发生率为27.89%,男高于女(P<0.05)。结论:儿童感觉统合失调发生率与父母文化程度、儿童自身智力、学习成绩、出生时缺氧缺血性脑病有关,有关部门要迅速组建机构对感觉统合失调进行训练。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号