全文获取类型
收费全文 | 60298篇 |
免费 | 5559篇 |
国内免费 | 4296篇 |
专业分类
耳鼻咽喉 | 614篇 |
儿科学 | 565篇 |
妇产科学 | 577篇 |
基础医学 | 6914篇 |
口腔科学 | 1210篇 |
临床医学 | 7876篇 |
内科学 | 8636篇 |
皮肤病学 | 680篇 |
神经病学 | 2638篇 |
特种医学 | 2092篇 |
外国民族医学 | 41篇 |
外科学 | 6057篇 |
综合类 | 10745篇 |
现状与发展 | 19篇 |
一般理论 | 14篇 |
预防医学 | 4590篇 |
眼科学 | 1683篇 |
药学 | 6406篇 |
66篇 | |
中国医学 | 3497篇 |
肿瘤学 | 5233篇 |
出版年
2024年 | 238篇 |
2023年 | 936篇 |
2022年 | 2370篇 |
2021年 | 3185篇 |
2020年 | 2357篇 |
2019年 | 1946篇 |
2018年 | 2078篇 |
2017年 | 1837篇 |
2016年 | 1699篇 |
2015年 | 2849篇 |
2014年 | 3416篇 |
2013年 | 2973篇 |
2012年 | 4288篇 |
2011年 | 4761篇 |
2010年 | 3311篇 |
2009年 | 2703篇 |
2008年 | 3204篇 |
2007年 | 3211篇 |
2006年 | 3194篇 |
2005年 | 3079篇 |
2004年 | 2264篇 |
2003年 | 2103篇 |
2002年 | 1719篇 |
2001年 | 1468篇 |
2000年 | 1349篇 |
1999年 | 1382篇 |
1998年 | 944篇 |
1997年 | 898篇 |
1996年 | 656篇 |
1995年 | 678篇 |
1994年 | 565篇 |
1993年 | 339篇 |
1992年 | 374篇 |
1991年 | 335篇 |
1990年 | 295篇 |
1989年 | 261篇 |
1988年 | 221篇 |
1987年 | 205篇 |
1986年 | 141篇 |
1985年 | 118篇 |
1984年 | 66篇 |
1983年 | 39篇 |
1982年 | 24篇 |
1981年 | 32篇 |
1980年 | 8篇 |
1979年 | 24篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
膳食纤维分析方法的简化 总被引:14,自引:0,他引:14
对SelvendranRR等人的冷中性洗涤剂纤维提取分析法(CNDF)进行简化,改变了各溶剂的处理时间,省去了湿球研磨与超声波处理步骤。将原法中SLS-PAW-DWSO处理时间15h,30min和16h分别延长为22h,40min与22h,化学分析与透射电镜观察结果表明,简化法对膳食纤维的提取分析效果与原推荐法相同,更加方便与实用。 相似文献
52.
不能切除肿瘤的恶性梗阻性黄疸的外科姑息治疗方法繁多,本文介绍自1989年以来,采取开腹经不同途径的带支撑导管胆肠内引流的方法治疗30例,减黄确切,尚对7例高位胆管癌在解除胆道梗阻的基础上行术后(192)Ir和(60)Co联合放疗,提高了病人生存质量及延长了生命。 相似文献
53.
Effect of fathers'' age and birth order on occurrence of congenital heart disease. 总被引:3,自引:1,他引:2 下载免费PDF全文
STUDY OBJECTIVE--The aim was to examine if there is an effect of fathers' age and of birth order on the occurrence of congenital heart disease. DESIGN--This was a hospital based case-referent study including use of birth defects surveillance data. SUBJECTS--Subjects were 497 cases of congenital heart disease aged between 3 months and 5 years, born in Beijing and Hebei Province, China; 6222 children without congenital heart disease serve as reference baseline. MEASUREMENTS AND MAIN RESULTS--With stratified analysis and logistic regression analyses, congenital heart disease was found to be associated with fathers' age less than 25 years (odds ratio 2.63), independent of mothers' age and of birth order. There was also evidence to show a higher birth order effect on the occurrence of congenital heart disease independent of parental ages. CONCLUSION--Higher birth order and fathers aged less than 25 years were both independently associated with some categories of congenital heart disease and with congenital heart disease overall. 相似文献
54.
法乐四联症右室心肌超微结构定量测量与临床的对比研究 总被引:3,自引:0,他引:3
为探讨法乐四联症(F_4)右室心肌超微结构的不同表现与F_4术前各项临床检查及术后心功能的关系,作者对室间隔缺损组(Ⅰ组,11例),儿童F_4组(Ⅱ组,13例)和成人F_4组(Ⅲ组,13例)进行比较,用Systat计算机统计软件作多因素方差分析和Pearson相关研究。结果见Ⅱ、Ⅲ组病人的PO_2仅和核浆比有关,P_(RV)与细胞的核体密度、横径、核浆比及肥大肌细胞比率明显有关,肥大肌细胞比率与病人年龄及PaO_2明显相关。作者认为F_4病人右室心肌超微结构改变主要系右室压力增高所致,这种改变与年龄有关。 相似文献
55.
Abstract We previously demonstrated that epidermal growth factor (EGF) induces a several-fold increase in ornithine decarboxylase (ODC) activity and the steady-state level of ODC mRNA in cultured SV40-transformed human keratinocytes (1). Pretreatment of cell cultures with ultraviolet B (UVB) radiation resulted in a reduction of EGF-induced ODC activity. To determine whether UVB inhibits the accumulation of ODC mRNA by EGF, cells were pretreated with 20 mJ/cm2 UVB or sham-irradiated and then incubated with 100 ng/ml EGF. Northern blot analysis revealed that UVB irradiation entirely blocked the EGF induction of ODC mRNA. Since the binding of EGF to its plasma membrane receptor is the first step in initiating a biological response, the effect of UVB on EGF binding was evaluated. UVB treatment of cultured keratinocytes resulted in an immediate and dose-dependent reduction of EGF binding. Scatchard analysis revealed thai the reduction of EGF binding was due to a 52% decrease in the number of available receptors, from 6.2 × 104/cell to 3.0 × 104/cell. However, UVB decreased the EGF-binding affinity very little (Kd = 0.60 nM in control and Kd=0.75 nM in UVB-treated Z114 cells). In addition, UVB did not alter the rate of EGF internalization. These data suggest that UVB blocks the signal transduction pathway of EGF that is involved in regulation of ODC gene expression. Immunoblot analysis of extracts from irradiated cells showed that UVB induced tyro-sine phosphorylation of EGFR and that the quantity of EGFR protein was unaffected by UVB treatment. Phosphorylation of EGFR may be responsible for decreased binding of EGF to its receptor. 相似文献
56.
57.
吡那地尔对高血压心脏结构和功能重构的影响 总被引:5,自引:0,他引:5
在等降压剂量下吡那地尔和赖诺普利可使4月龄自发性高血压大鼠的血压下降6.0 ̄8.0kPa,并接近同种属正常血压大刀瓣血压水平。 相似文献
58.
Fan Xiao-Guang Zheng Zhen-Qun FAN XIAO-GUANG ZHENG ZHEN-QUN 《American journal of reproductive immunology (New York, N.Y. : 1989)》1997,37(5):359-364
PROBLEM and METHOD: Early pregnancy factor (EPF), an Immunosuppressive substance, which appears in pregnant women's sera 48 h after fertilization, is a kind of pregnancy-specific protein. To determine whether the EPF activity could be a super early indicator of pregnancy, we used rosette inhibition assay to detect EPF activity in the sera, collected from 70 women 2–7 days after ovulation intending to conceive monitored by ultrasonography. Simultaneously we selected 40 non-pregnant sera and 12 early-pregnant sera as negative control and positive control, respectively. RESULTS: The results of this study demonstrated that EPF activity is detected in 35 women's sera out of 70 women within 2–7 days after ovulation, and 28 women out of the 35 were pregnant, which was known by follow-up, and 7 were not pregnant, possibly due to either false positive results or embryo loss because of preimplantation failure, thus causing no pregnancy. The other 35 out of 70 had no EPF activity and 34 of them were not pregnant, which was known by follow-up, but one case became pregnant, which was false negative result. Our study showed that diagnosis of the super early pregnancy could be made by detecting EPF activity in maternal serum within the time of preimplantation. The accuracy of pregnancy diagnosis by this method is 88.6%, with a false negative rate of 3.4% and a false positive rate of 17.1%. The β-HCG level was measured from the above 70 women's sera in order to contrast EPF activity. All of the sera collected 2–6 days following ovulation indicated that there were lower β-HCG values in very early pregnancy (≥a5 mIU/ml). On the seventh day after ovulation, EPF activity was detected in 11 out of 15 sera with only 2 of them with a b-HCG level that reached or slightly surpassed that of the early pregnancy diagnosis (5 mIU/ml and 5.4 mIU/ml, respectively). This demonstrated that β-HCG is not the earliest signal of pregnancy; otherwise the EPF activity is one that appears 2–6 days earlier than β-HCG appears. We measured the progesterone level of the 48 sera from the 70 collected above within 2–7 days postovulation and found most of them reached the level of progesterone in the luteal phase (7.5–98.3 nmol/L). This indicated that ovulation had taken place in these women, which was in accordance with observations by ultrasonography. CONCLUSIONS: Our study showed that diagnosis (of 88.6%) of super early pregnancy could be made with an accuracy of 88.6% by detecting EPF activity in maternal serum within 2-days after ovulation. This offers a basis for pregnancy diagnosis for the women who attempt to terminate their pregnancy safely or who conceive unexpectedly, and it contributes to family-planning. 相似文献
59.
用细胞内HRP染色的方法显示该神经元位于猫运动皮层十字沟后,在第Ⅱ/Ⅲ层之间(软膜以下438μm处),胞体截面积为15.6×28.1μm~2,呈多极形,树突呈串珠状,向四周扩展,无侧棘,轴突由胞体下方伸出,返折向上,包绕胞体周围,以软膜平行的吻尾方向行走为主,有一分枝向白质方向延伸.从立体重构图的不同角度观察,其形态不对称,如沿X轴方向旋转60°后,其形态呈扁平形,用胶体金免疫电镜观察,该神经元的递质性质为GABA能的.胞体及树突上分布有非对称型和对称型的突触,对称型的突触中有的是GABA能的,有的是非GABA能的.其轴突有髓鞘包绕,末梢与其它神经元的胞体形成一处以上相连或不相连的对称型突触,也可与其它树突形成对称型的突触.根据该神经元的形态,递质性质及突触分布的特征,可确认它是篮状细胞. 相似文献
60.