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   36003篇
  免费   1838篇
  国内免费   150篇
耳鼻咽喉   486篇
儿科学   653篇
妇产科学   437篇
基础医学   4491篇
口腔科学   1183篇
临床医学   2493篇
内科学   8075篇
皮肤病学   790篇
神经病学   3372篇
特种医学   1871篇
外国民族医学   1篇
外科学   5668篇
综合类   130篇
一般理论   6篇
预防医学   1086篇
眼科学   762篇
药学   2388篇
中国医学   78篇
肿瘤学   4021篇
  2023年   167篇
  2021年   606篇
  2020年   356篇
  2019年   462篇
  2018年   594篇
  2017年   494篇
  2016年   640篇
  2015年   598篇
  2014年   790篇
  2013年   967篇
  2012年   1602篇
  2011年   1653篇
  2010年   1016篇
  2009年   838篇
  2008年   1470篇
  2007年   1732篇
  2006年   1593篇
  2005年   1532篇
  2004年   1567篇
  2003年   1460篇
  2002年   1526篇
  2001年   1326篇
  2000年   1430篇
  1999年   1293篇
  1998年   485篇
  1997年   401篇
  1996年   375篇
  1995年   310篇
  1994年   314篇
  1993年   285篇
  1992年   994篇
  1991年   854篇
  1990年   824篇
  1989年   811篇
  1988年   769篇
  1987年   764篇
  1986年   669篇
  1985年   626篇
  1984年   433篇
  1983年   350篇
  1979年   302篇
  1978年   205篇
  1977年   178篇
  1974年   196篇
  1973年   163篇
  1972年   162篇
  1971年   181篇
  1970年   155篇
  1969年   176篇
  1968年   147篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Although the presence of renal cysts has been reported to be associated with aortic aneurysm or dissection by imaging studies, an autopsy study has not been performed. Therefore, in our institute, recent consecutive adult autopsy cases (n = 108, 64 males and 44 females) were reviewed. The circumferences and atherosclerosis ratios of both thoracic and abdominal aorta were individually measured and graded. The number of renal cysts was scored and graded. Age of subjects along with histories of smoking, hypertension, and diabetes mellitus were confirmed. Multiple linear regression analyses demonstrated that severity of atherosclerosis and the number of renal cysts were correlated with thoracic aortic circumference, while only the number of renal cysts was correlated with abdominal aortic circumference (p < 0.05), which was more predominant in female subjects (p < 0.05). Microscopically, significantly more dilated renal tubules (by Student's t-test, p < 0.05) along with decreased stainability of basement membrane by Periodic acid-Schiff staining and immunostaining of type IV collagen were noted in background renal tissues in cases with numerous renal cysts than in age- and sex-matched controls without renal cysts (n = 10 vs. 10). The present study suggests that a syndrome that affects both aorta and renal tubules may exist.  相似文献   
992.
Clinical Autonomic Research - Patients with neurogenic orthostatic hypotension in the setting of Lewy body diseases (LBnOH) typically have baroreflex failure and peripheral noradrenergic...  相似文献   
993.
Sessile serrated adenoma/polyps (SSA/Ps) of the colon are thought to be precursors of sporadic carcinomas. Although it is suggested that SSA/P may grow rapidly from the early stage, its cell kinetics remains obscure. To solve this problem, we analyzed the mitotic and apoptotic activity of normal crypts, microvesicular hyperplastic polyps (MVHPs), and tubular adenomas (TAs), using phospho-histone H3 and cleaved caspase 3 immunohistochemistry. The mitotic index for SSA/Ps (mean, 5.63) and TAs (6.98) was significantly higher than those for normal crypts (2.72) and MVHPs (2.86). Of all tested lesions, the apoptotic index was lowest for SSA/Ps (0.96; normal, 2.71; MVHPs, 2.62; TAs, 6.01) with statistically significant differences. The net growth ratio was close to 1.0 in normal crypts (1.07) while remaining low in MVHPs (1.06) and TAs (1.38), but was markedly elevated in SSA/Ps (7.32, P?<?0.01) due to the large imbalance between mitosis and apoptosis. As to apoptosis regulatory proteins, expression of anti-apoptotic Bcl-2 was significantly reduced or undetectable in MVHPs and SSA/Ps, while TAs showed stronger staining than normal crypts. Expression of pro-apoptotic Bax and its activators, Bim and Bad, was significantly reduced in MVHPs and SSA/Ps. We suggest that other complex mechanisms may act synergistically with Bax, Bim, or Bad deficiency to regulate apoptosis suppression in SSA/Ps.  相似文献   
994.
995.
Tendons transmit force from muscle to bone for joint movement. Tenocytes are a specialized type of fibroblast that produces collagen fibrils in tendons. Their cytoplasmic processes form a network surrounding collagen fibrils to define a collagen fibre. Glycosaminoglycan (GAG) chains link collagen fibrils and adhere at the D-band of the collagen fibril. In this study, we used array and scanning transmission electron microscope (STEM) tomographies to reconstruct the three-dimensional ultrastructure of tenocytes, collagen fibres, collagen fibrils and GAG chains at the bifurcation of the bovine hindlimb superficial digital flexor tendon (SDFT). Collagen fibrils comprising a collagen fibre were not aligned uniformly and had at least two running directions. Spindle-shaped tenocytes were arranged along the long axis of a plurality of collagen fibres, where two groups of collagen fibrils with oblique directions to each other exhibited an oblique overlap of the two collagen fibril layers. Collagen fibrils with different running directions were observed in separating layers of about 300 nm in thickness and had diameters of 0–200 nm. About 40% of all collagen fibrils had a peak in the range of 20–40 nm. STEM analysis of the same site where the crossing of collagen fibres was observed by transmission electron microscopy demonstrated the outline of collagen fibrils with a clear D-banding pattern at a regular interval. Collagen fibrils were reconstructed three-dimensionally using continuous images acquired by STEM tomography, which confirmed that the collagen fibrils at the crossing sites did not orientate in layers, but were woven one by one. Higher magnification observation of GAG chains attached between the crossing collagen fibrils revealed numerous GAG chains arranged either vertically or obliquely on collagen fibrils. Furthermore, GAG chains at the cross of collagen fibrils connected the closest D-bands. GAG chains are thought to be universally present between collagen fibrils of the tendon. These observations by array and STEM tomographies increase our knowledge of the anatomy in the bifurcation of the bovine hindlimb SDFT and demonstrate the utility of these new imaging technologies.  相似文献   
996.
The aim of this study was to investigate the effects of multicomponent training on baroreflex sensitivity (BRS) and heart rate (HR) complexity of prefrail older adults. Twenty-one prefrail community-dwelling older adults were randomized and divided into multicomponent training intervention group (MulTI) and control group (CG). MulTI performed multicomponent exercise training over 16 weeks and CG was oriented to follow their own daily activities. The RR interval (RRi) and blood pressure (BP) series were recorded for 15 min in supine and 15 min in orthostatic positions, and calculation of BRS (phase, coherence, and gain) and HR complexity (sample entropy) were performed. A linear mixed model was applied for group, assessments, and their interaction effects in supine position. The same test was used to assess the active postural maneuver and it was applied separately to each group considering assessments (baseline and post-intervention) and positions (supine and orthostatic). The significance level established was 5%. Cardiovascular control was impaired in prefrail older adults in supine position. Significant interactions were not observed between groups or assessments in terms of cardiovascular parameters. A 16-week multicomponent exercise training did not improve HR complexity or BRS in supine rest or in active postural maneuver in prefrail older adults.  相似文献   
997.
998.
Micronodular thymoma with lymphoid stroma (MNT) is a rare thymic epithelial neoplasm subtype characterized by a micronodular tumor cell growth pattern and abundant lymphoid stroma. Micronodular thymic carcinoma with lymphoid stroma (MNCA) is considered as a malignant counterpart of MNT and exhibits a growth pattern similar to that of MNT but has histologic features reminiscent of thymic squamous cell carcinoma, such as cytologic atypia and CD5 and CD117 immunoexpression. Although both MNT and MNCA are characterized by abundant lymphoid stroma, it remains unknown whether there are differences in infiltrating lymphocytes between MNT and MNCA. We analyzed the immune microenvironment profile in eight MNT and three MNCA cases. The cell density of CD8-positive T cells was significantly higher in MNT than in MNCA, whereas that of FOXP3-positive T cells was significantly higher in MNCA than in MNT. There was no significant difference in the cell density of programmed death protein 1-positive T cells and programmed death ligand 1 expression between the MNT and MNCA cases. Our findings indicated that the immune microenvironment of MNCA differed from that of MNT and, compared with the T-cell profile of MNT, that of MNCA was more suppressive to patients′ antitumor immune response.  相似文献   
999.
The Notch signaling pathway plays a key role in the morphogenesis of the biliary tree, but its involvement in cystic biliary diseases, such as Caroli disease (CD) and polycystic liver disease (PLD), has yet to be determined. Immunostaining was performed using liver sections of CD and PLD, and the results were compared with those of congenital hepatic fibrosis (CHF) and von Meyenburg complex (VMC). The expression of Notch receptor 1 (Notch1) was increased in the nuclei of biliary epithelial cells in all cases of CD and PLD, whereas it remained at a low level in CHF and VMC. In addition, Notch2 and Notch3 were preferably expressed in the nuclei of biliary epithelial cells of PLD. Accordingly, the Notch effector Hes1 was highly expressed in biliary epithelial cells of CD and PLD, and the cell proliferative activity was significantly higher in CD and PLD. The expression of the Notch ligand Delta-like 1 was significantly increased in biliary epithelial cells of CD and PLD, which may be causally associated with the nuclear overexpression of Notch1 and Hes1. These results indicate that aberrant activation of the Notch-Hes1 signaling pathway may be responsible for the progression of biliary cystogenesis in CD and PLD.  相似文献   
1000.
Monoclonal antibodies (mAbs) are widely utilized as therapeutic drugs for various diseases, such as cancer, autoimmune diseases, and infectious diseases. Using the avian-derived B cell line DT40, we previously developed an antibody display technology, namely, the ADLib system, which rapidly generates antigen-specific mAbs. Here, we report the development of a human version of the ADLib system and showcase the streamlined generation and optimization of functional human mAbs. Tailored libraries were first constructed by replacing endogenous immunoglobulin genes with designed human counterparts. From these libraries, clones producing full-length human IgGs against distinct antigens can be isolated, as exemplified by the selection of antagonistic mAbs. Taking advantage of avian biology, effective affinity maturation was achieved in a straightforward manner by seamless diversification of the parental clones into secondary libraries followed by single-cell sorting, quickly affording mAbs with improved affinities and functionalities. Collectively, we demonstrate that the human ADLib system could serve as an integrative platform with unique diversity for rapid de novo generation and optimization of therapeutic or diagnostic antibody leads. Furthermore, our results suggest that libraries can be constructed by introducing exogenous genes into DT40 cells, indicating that the ADLib system has the potential to be applied for the rapid and effective directed evolution and optimization of proteins in various fields beyond biomedicine.  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