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   40638篇
  免费   1914篇
  国内免费   229篇
耳鼻咽喉   486篇
儿科学   717篇
妇产科学   635篇
基础医学   5179篇
口腔科学   1285篇
临床医学   2971篇
内科学   10085篇
皮肤病学   918篇
神经病学   2994篇
特种医学   1633篇
外科学   6803篇
综合类   261篇
一般理论   2篇
预防医学   1231篇
眼科学   643篇
药学   2691篇
中国医学   56篇
肿瘤学   4191篇
  2023年   211篇
  2022年   449篇
  2021年   826篇
  2020年   401篇
  2019年   580篇
  2018年   796篇
  2017年   596篇
  2016年   677篇
  2015年   779篇
  2014年   1012篇
  2013年   1137篇
  2012年   1817篇
  2011年   1947篇
  2010年   1065篇
  2009年   1039篇
  2008年   1818篇
  2007年   1933篇
  2006年   1950篇
  2005年   1972篇
  2004年   1917篇
  2003年   1829篇
  2002年   1829篇
  2001年   1292篇
  2000年   1444篇
  1999年   1279篇
  1998年   516篇
  1997年   370篇
  1996年   370篇
  1995年   353篇
  1994年   300篇
  1993年   262篇
  1992年   842篇
  1991年   791篇
  1990年   707篇
  1989年   717篇
  1988年   696篇
  1987年   681篇
  1986年   683篇
  1985年   604篇
  1984年   438篇
  1983年   362篇
  1979年   344篇
  1978年   237篇
  1977年   202篇
  1975年   201篇
  1974年   229篇
  1973年   211篇
  1971年   212篇
  1970年   203篇
  1969年   226篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
The primed status of T cells is markedly different among liver transplant recipients, due to a lifetime of antigen exposure and reduced thymopoiesis by aging, and diseases. This study aims to characterize the preoperative immunological status of CD8+ T cell subpopulations and relate it to the outcome for liver transplant recipients. We classified 112 liver transplant recipients into 5 groups, based on hierarchical clustering of the CD8+CD45 isoform proportion of T cells. In Groups I and II (pediatric), the naive T cell proportion was more than 50%. In adult recipients, Group III was characterized by a naive T cell proportion of 50%, Group IV had the greatest effector/memory T cells (EM), and Group V had the greatest proportion of effector T cells. In Groups IV and V, the effector T cell proportion was considerably higher, and was accompanied by marked downregulation of the CD27+CD28+ subsets and upregulation of interferon gamma (IFN)-gamma, tumor necrosis factor-alpha, and perforin expression. Group V recipients tended to be complicated postoperatively, with a significantly reduced survival rate (1 yr, 66.8%) and markedly reduced Eastern Cooperative Oncology Group performance status.  相似文献   
93.
Electrogastrograms (EGGs) were recorded in patients both before and after receiving proximal gastrectomy plus jejunal interposition (PGJI) or just after receiving total gastrectomy plus jejunal interposition (TGJI). Intraluminal pressure was also recorded in some postoperative patients. The EGG 3 cpm component (2.5-4.9 cpm) remained after PGJI, but subsequently decreased with a significant reduction in the preoperative to postoperative ratio of the 3 cpm components (P<0.05). The mean frequency of the 3 cpm components increased significantly after PGJI (P<0.05) and its instability factor increased. The EGG 10 cpm components became relatively dominant compared to other frequency components in 2 out of 8 of patients having PGJI but the mean amplitude of 10 cpm decreased. In TGJI patients, only the 10 cpm component was conspicuous in EGG as in the case of total gastrectomy and Roux en Y anastomosis procedures. The spectral frequencies of intraluminal pressure in the interposed jejunum were similar to the EGG of 10 cpm components both in the case of PGJI and TGJI patients. In conclusion, surface EGG could record the electrical activities of the interposed jejunum more easily in patients having had TGJI than in PGJI.  相似文献   
94.
Serial DWIs were performed in a patient with CJD who developed symptoms acutely and progressed rapidly. DWI discloed an increased signal in the frontal and parietal inner cortical areas, and in the caudate nuclei and putamina 20 days after the onset of symptoms. T2-weighted images showed only signal abnormality in the caudate nuclei and putamina, but not in the cerebral cortex. In the CSF obtained 15 days after the onset of symptoms, total tau protein was markedly elevated and 14-3-3 protein was positive. Measurement of these proteins are highly specific and sensitive for the diagnosis of CJD, but not available as a rapid routine examination at present. DWI is not specific, but useful for making the diagnosis of CJD in the early stage of the disease.  相似文献   
95.
Release fluoroimmunoassay (RFIA), a new method of enzyme immunoassay (ELISA), was employed for the detection of specific IgE antibody in patients allergic to Japanese cedar pollen. RFIA clearly discriminated between allergic patients and healthy subjects. Further, RFIA was able to detect the minute IgE antibody at the dilution range of 1/32 of patient's serum. Correlation between the relative fluorescent unit values and the RAST values of sera from 17 patients and seven healthy subjects was very high. The correlation coefficient was 0.87. These findings show that the RFIA has an advantage over the other procedures for the diagnosis of immediate-type hypersensitivity as well as the diagnosis of Japanese cedar pollen.  相似文献   
96.
97.
A case of atrial septal aneurysm associated with combined valvular disease and coronary-pulmonary fistula (C-PA fistula) was presented. The patient successfully underwent mitral valve replacement, excision and closure of the aneurysm, tricuspid annuloplasty and closure of C-PA fistula. Atrial septal aneurysm is a rare anomaly and its natural course is thought to be generally good without significant clinical symptoms. However, complications such as cerebral and pulmonary embolism, or occlusion of the atrioventricular vales by the prolapsed aneurysm were reported to occur in small number of cases. In this case, diagnosis of the aneurysm was made by 2-D and Doppler echocardiography and further confirmed by cineangiography. Routine echocardiographic examinations will serve as useful noninvasive method for detection and follow up study of this anomaly.  相似文献   
98.
To determine the relative superiority of a prosthesis in the mitral position, in vivo hemodynamics were examined by Doppler echocardiography, and the results were compared with other types of mechanical mitral valves including 63 Bj?rk-Shiley convexo-concave (BS) values, 30 Duromedics (DM) valves, and 58 Medtronic Hall (MH) valves. For this comparison, the following indices were evaluated: peak velocity of mitral flow (PV), mitral valve orifice area (MVA), mitral valvular regurgitation, New York Heart Association (NYHA) classification, pulmonary capillary wedge pressure (PC), cardiac index (CI) and valve-related complications. On Doppler echocardiograms, PV ranged from 1.2 to 2.0 m/sec with a mean of 1.6 m/sec. There was no evident relationship between the PV and the valve size in each type of prosthesis, and no significant difference in the PVs among the valves. The mean MVA was 2.6 cm2 (25 mm DM, 25 mm MH), which was regarded satisfactory from a clinical standpoint. MVA increased with the increase in the valve size in all types of valves, and of all sizes, MVA was larger in the DM and MH groups than in the BS group. Similarly, the incidence of valvular regurgitation was relatively low in all groups, and the degree of regurgitation proved to be grade II or less in all cases. As for the clinical results, clinical symptoms (NYHA) and hemodynamic states (PC, CI) improved postoperatively, with the differences among the types of prosthetic valves being insignificant. The incidences of thromboembolism, valvular thrombosis, valve failure and prosthetic endocarditis were relatively low in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
99.
The risk of cerebral infarction (CI) in an individual is dependent on the interplay between genetic risk factors and environmental influences. Binding of thromboxane A2 (TXA2) to its receptor (TP) modulates thrombosis/hemostasis and plays a significant role in the pathogenesis of CI. The aim of the present study was to investigate the relationship between human TP gene single nucleotide polymorphisms (SNPs) and haplotypes and CI in a Japanese population. A genetic association study was performed in 194 CI patients and 365 non-CI subjects by specifically characterizing 6 SNPs in the human TP gene (rs2271875, rs768963, rs2238634, rs11085026, rs4523 and rs4806942). Analysis demonstrated that there were significant differences in the overall distribution of genotypes and dominant or recessive models of rs2271875 and rs768963 between the CI and the non-CI groups. Multiple logistic regression analysis revealed that the C allele of rs768963 was significantly associated with CI (p = 0.029), even after adjusting for confounding factors (odds ratio: 2.41). Further, the C-T-C haplotype of rs768963-rs2238634-rs4806942 was significantly more frequent in the CI group (23.0%) than in the non-CI group (17.7%). These results suggest that specific SNPs and haplotypes may have utility as genetic markers for the risk of CI and that TP or a neighboring gene is associated with the increased susceptibility to CI.  相似文献   
100.
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