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   7413篇
  免费   350篇
  国内免费   127篇
耳鼻咽喉   350篇
儿科学   653篇
妇产科学   181篇
基础医学   696篇
口腔科学   182篇
临床医学   739篇
内科学   445篇
皮肤病学   134篇
神经病学   901篇
特种医学   639篇
外科学   1432篇
综合类   851篇
现状与发展   1篇
预防医学   198篇
眼科学   54篇
药学   286篇
  4篇
中国医学   24篇
肿瘤学   120篇
  2024年   6篇
  2023年   139篇
  2022年   146篇
  2021年   211篇
  2020年   240篇
  2019年   224篇
  2018年   239篇
  2017年   178篇
  2016年   227篇
  2015年   255篇
  2014年   456篇
  2013年   382篇
  2012年   351篇
  2011年   431篇
  2010年   340篇
  2009年   384篇
  2008年   349篇
  2007年   341篇
  2006年   326篇
  2005年   307篇
  2004年   266篇
  2003年   173篇
  2002年   168篇
  2001年   133篇
  2000年   142篇
  1999年   126篇
  1998年   107篇
  1997年   119篇
  1996年   112篇
  1995年   86篇
  1994年   109篇
  1993年   100篇
  1992年   76篇
  1991年   74篇
  1990年   60篇
  1989年   53篇
  1988年   51篇
  1987年   51篇
  1986年   33篇
  1985年   52篇
  1984年   63篇
  1983年   22篇
  1982年   42篇
  1981年   37篇
  1980年   29篇
  1979年   25篇
  1978年   19篇
  1977年   13篇
  1976年   4篇
  1974年   3篇
排序方式: 共有7890条查询结果,搜索用时 359 毫秒
81.
The effects of increases in cellular adenosine 3′5′-cyclic monophosphate (cAMP) on 5-hydroxytryptamine-(5-HT-) induced generation of inositol phosphates (IPs) and increases in intracellular Ca2+ ([Ca2+]i) were investigated using canine cultured tracheal smooth muscle cells (TSMCs). Cholera toxin and forskolin induced concentration- and time-dependent cAMP formation with half-maximal effects (−logEC50) produced at concentrations of 7.0 ± 0.5 and 4.9 ± 0.4  respectively. Pretreatment of TSMCs with either forskolin or dibutyryl cAMP inhibited 5-HT-stimulated responses. Even after treatment for 24h, these agents still inhibited the 5-HT-induced Ca2+ mobilization. The inhibitory effects of these agents produced both depression of the maximal response and a shift to the right of the concentration response curves of 5-HT. The water-soluble forskolin analogue L-858051 [7-deacetyl-7β-(γ-N-methylpiperazino)-butyryl forskolin] significantly inhibited the 5-HT-stimulated accumulation of IPs. In contrast, the addition of 1,9-dideoxy forskolin, an inactive forskolin analogue, had little effect on this response. Moreover, SQ-22536 [9-(tetrahydro-2-furanyl)-9-H-purin-6-amine], an inhibitor of adenylate cyclase, and both H-89 [N-(2-aminoethyl)-5-isoquinolinesulphonamide] and HA-1004[N-(2-guanidinoethyl)-5-isoquinolinesulphonamide], inhibitors of cAMP-dependent protein kinase (PKA), attenuated the ability of forskolin to inhibit the 5-HT-stimulated accumulation of IPs. These results suggest that activation of cAMP/PKA was involved in these inhibitory effects of forskolin. The AlF4 -induced accumulation of IPs was inhibited by forskolin, suggesting that G protein(s) are directly activated by AlF4 - and uncoupled from phospholipase C by forskolin treatment. These results suggest that activation of cAMP/PKA might inhibit the 5-HT-stimulated phosphoinositide breakdown and consequently reduce the [Ca2+]i increase or inhibit both responses independently. Received: 14 March 1996/Accepted: 10 April 1996  相似文献   
82.
氟尿嘧啶引起大鼠气管损伤修复过程中干细胞的定位   总被引:10,自引:2,他引:10  
丁强  贾心善 《解剖学报》2004,35(3):328-330
目的 气管干细胞的原位观察。方法 使用5-氟尿嘧啶(5-FU)造成大鼠离体气管环的严重损伤,采用光镜、PCNA免疫组织化学,以及Hoechst33342染色观察气管黏膜的修复过程。结果 5-Fu作用12h后,气管上皮脱落,可见少量间隔分布的类似裸核的细胞呈钉状位于基底膜上,PCNA染色阴性(Go期细胞),其中少数细胞Hoechst33342染色阴性。去除5-FU6h后,气管黏膜由扁平上皮覆盖;48h后,气管环恢复假复层纤毛柱状上皮。结论 5-Fu能杀死处于细胞周期的气管上皮细胞,对Go期细胞作用很小,残留于基底膜上的裸核样的Go期细胞中含有干细胞,其Hoechst33342染色阴性,并具有排出荧光染料的能力,正是这些细胞的增殖分化,修复了损伤的气管环。  相似文献   
83.
A case of a rare vascular tumor, intravenous tufted angioma, is described. A 51-year-old Japanese man presented with a 12x8 mm solitary reddish nodule on the right foot, which had been found at birth. Histologically, the tumor was confined to a malformed vein and was characterized by nodular aggregates of plump cells. The aggregates showed a compact proliferation of round cells, including capillary-forming cells. Venous angiomatous areas were also observed. No multinucleated giant cells were seen. Immunohistochemically, the capillary-forming cells in the aggregates and the endothelial cells in the angiomatous areas were positive for endothelial markers (factor VIII-related antigen, CD31, CD34). Pericyte-like cells expressing alpha-smooth muscle actin and muscle actin, and macrophage-like cells, which stained for factor XIIIa, were intermingled in the cellular aggregates. Flow cytometric analysis showed diploidy. The tumor may be a hamartomatous lesion modified by secondary reactive changes, and it may represent a distinctive clinicopathological entity that is closely related histogenetically and perhaps pathologically to tufted angioma and the recently described "giant cell angioblastoma".  相似文献   
84.
This paper describes an 8-year-old girl with Klippel-Feil syndrome (KFS) associated with frontonasal dysplasia, Sprengel deformity and postaxial polydactyly. These findings are tentatively explained on the basis of a single mutant gene for KFS with broad action in the morphogenesis of the skeletal system.  相似文献   
85.
A diagnosis of the Neu-Laxova syndrome (NLS) was made by ultrasonography at 32 wks of gestation. Ultrasonographic examination showed intrauterine growth retardation (IUGR), Dandy-Walker anomaly, choroid plexus cysts, receding forehead and microcephaly, bilateral cataract without prominent eyes, scalp edema with no generalized edema, retrognathia, curved penis, and flexion deformities of limbs. The findings in this case are consistent with NLS; however, they did not fit any of Curry's [1982] groups. Massive swelling of hands and feet were among the main manifestations in classic NLS cases. In the case presented herein, edema was noted only in the scalp. This might shed further light on the question of variability vs. heterogeneity in the NLS. This case shows the existing possibility of an early diagnosis of NLS and adds Dandy-Walker anomaly and choroid plexus cysts as new findings to this syndrome. © 1992 Wiley-Liss, Inc.  相似文献   
86.
Split‐hand/foot malformation (SHFM) is a genetically heterogeneous congenital limb malformation typically limited to a defect of the central rays of the autopod, presenting as a median cleft of hands and feet. It can be associated with long bone deficiency or included in more complex syndromes. Among the numerous genetic causes, WNT10B homozygous variants have been recently identified in consanguineous families, but remain still rarely described (SHFM6; MIM225300). We report on three novel SHFM families harboring WNT10B variants and review the literature, allowing us to highlight some clinical findings. The feet are more severely affected than the hands and there is a frequent asymmetry without obvious side‐bias. Syndactyly of third–fourth fingers was a frequent finding (62%). Polydactyly, which was classically described in SHFM6, was only present in 27% of patients. No genotype–phenotype correlation is delineated but heterozygous individuals might have mild features of SHFM, suggesting a dose‐effect of the WNT10B loss‐of‐function.  相似文献   
87.
气管组织工程的研究策略及其展望   总被引:1,自引:0,他引:1  
气管组织工程是近10年来国内外研究的热点和难点问题,取得了一些进展.但如何更好地遴选基质材料、实现种子细胞共培养、上皮化以及再血管化来构建组织工程化气管仍需要不断寻求新的研究思路和策略.本文从气管重建和理想化气管替代物的角度,回顾了近年来在组织工程气管方面的研究进展,并对未来的研究作出展望.  相似文献   
88.
The clinical and radiological spectrum of spondylocostal dysostosis syndromes encompasses distinctive costo‐vertebral anomalies. RIPPLY2 biallelic pathogenic variants were described in two distinct cervical spine malformation syndromes: Klippel–Feil syndrome and posterior cervical spine malformation. RIPPLY2 is involved in the determination of rostro‐caudal polarity and somite patterning during development. To date, only four cases have been reported. The current report aims at further delineating the posterior malformation in three new patients. Three patients from two unrelated families underwent clinical and radiological examination through X‐ray, 3D computed tomography and brain magnetic resonance imaging. After informed consent was obtained, family‐based whole exome sequencing (WES) was performed. Complex vertebral segmentation defects in the cervico‐thoracic spine were observed in all patients. WES led to the identification of the homozygous splicing variant c.240‐4T>G in all subjects. This variant is predicted to result in aberrant splicing of Exon 4. The current report highlights a subtype of cervical spine malformation with major atlo‐axoidal malformation compromising spinal cord integrity. This distinctive mutation‐specific pattern of malformation differs from Klippel–Feil syndrome and broadens the current classification, defining a sub‐type of RIPPLY2‐related skeletal disorder. Of note, the phenotype of one patient overlaps with oculo‐auriculo‐vertebral spectrum disorder.  相似文献   
89.
A family with cardiac malformation, cleft lip-palate, short stature, microcephaly, distally placed thumbs, short 2nd and 5th fingers, long and broad 1st toes, broad distance between 1st and 2nd toes and mediodorsal curvature of the 4th toes with syndactyly of the 2nd and 3rd toes has been described as having a new syndrome. While some members of the family had full signs of the syndrome, others had similar but fewer and less severe anomalies of the same structures. The presence of common findings in three generations, its variable expressivity and pleiotropism, and the non-consanguineous history in the parents suggest that the inheritance is autosomal dominant.  相似文献   
90.
Lymphangioma is a disfiguring malformation of early childhood. A mouse lymphangioma model has been established by injecting Freund's incomplete adjuvant (FIA) intraperitoneally, but has not been compared with the human disease. We show that, in accordance with studies from the 1960s, the mouse model represents an oil-granuloma, made up of CD45-positive leukocytes and invaded by blood and lymph vessels. Several markers of lymphatic endothelial cells are expressed in both mouse and human, like CD31, Prox1, podoplanin, and Lyve-1. However, the human disease affects all parts of the lymphovascular tree. We observed convolutes of lymphatic capillaries, irregularly formed collectors with signs of disintegration, and large lymph cysts. We observed VEGFR-2 and -3 expression in both blood vessels and lymphatics of the patients, whereas in mouse VEGFR-2 was confined to activated blood vessels. The experimental mouse FIA model represents a vascularized oil-granuloma rather than a lymphangioma and reflects the complexity of human lymphangioma only partially.  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