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   168294篇
  免费   15291篇
  国内免费   7869篇
耳鼻咽喉   2286篇
儿科学   3808篇
妇产科学   1817篇
基础医学   30794篇
口腔科学   5329篇
临床医学   12911篇
内科学   23002篇
皮肤病学   4432篇
神经病学   9449篇
特种医学   3724篇
外国民族医学   118篇
外科学   14582篇
综合类   25774篇
现状与发展   48篇
预防医学   4609篇
眼科学   3499篇
药学   12880篇
  30篇
中国医学   5080篇
肿瘤学   27282篇
  2024年   363篇
  2023年   2442篇
  2022年   4282篇
  2021年   6073篇
  2020年   5373篇
  2019年   5237篇
  2018年   5419篇
  2017年   5710篇
  2016年   5967篇
  2015年   6810篇
  2014年   9849篇
  2013年   10901篇
  2012年   9455篇
  2011年   10619篇
  2010年   8812篇
  2009年   8458篇
  2008年   8918篇
  2007年   9114篇
  2006年   8297篇
  2005年   7615篇
  2004年   6756篇
  2003年   5852篇
  2002年   4823篇
  2001年   4132篇
  2000年   3421篇
  1999年   3082篇
  1998年   2921篇
  1997年   2673篇
  1996年   2387篇
  1995年   2092篇
  1994年   1844篇
  1993年   1533篇
  1992年   1237篇
  1991年   1171篇
  1990年   903篇
  1989年   844篇
  1988年   794篇
  1987年   632篇
  1986年   588篇
  1985年   777篇
  1984年   689篇
  1983年   484篇
  1982年   508篇
  1981年   405篇
  1980年   342篇
  1979年   256篇
  1978年   179篇
  1977年   139篇
  1976年   103篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
重症肌无力患者胸腺肥大细胞的形态数量和超微结构研究   总被引:2,自引:1,他引:1  
为探讨研究重症肌无力(MG)患者胸腺内肥大细胞的形态数量和其超微结构变化与MG发病的关系。方法对28例MG患者作胸腺肥大细胞的形态半定量分析和光镜观察,其中16例的胸腺进行电镜检查。结果MG胸腺不仅表现组织学异常,且肥大细胞数量明显增多,尤其是在非增生胸腺内出现大量肥大细胞,而在增生的髓质和生发中心区几乎见不到。电镜观察提示肥大细胞与上皮细胞、T淋巴细胞和毛细血管关系密切,且含多种形态的分泌颗粒。结论肥大细胞对胸腺细胞的分化成熟、胸腺屏障和胸腺功能,以及MG发病均起到一定的重要作用。  相似文献   
72.
73.
This study examined the mitogenic response to keratinocyte growth factor (KGF) of normal and tumour-derived human oral keratinocytes in which the degree of cellular differentiation was known and in contiguous fibroblast cultures derived from the malignant epithelial cultures. Keratinocytes, but not fibroblasts, were stimulated by KGF. There by demonstrating epithelial target cell specificity of the ligand. KGF-induced stimulation of the tumour-derived keratinocytes cultured in the absence of the 3T3 fibroblast support broadly correlated with the degree of cellular differentiation; well-differentiated keratinocytes were stimulated more by KGF than their less differentiated counterparts. Malignant oral keratinocytes expressed KGF cell surface receptors (KD 451-709 pM; receptors/cell 2306-413645), but KGF receptor mRNA did not correlate with either KGF-induced mitogenesis or the degree of epithelial cell differentiation. When the tumour-derived keratinocytes were cultured in the presence of 3T3 fibroblasts, the mitogenic response to KGF was comparable to normal epithelial cells. The results suggest that KGF-mediated growth stimulation may not be significant in providing a selective advantage for the growth of malignant keratinocytes.  相似文献   
74.
The in vitro proliferation of peripheral blood lymphocytes (PBLs) without any mitogenic stimulation is one of the hallmarks of human T lymphotropic virus type I (HTLV-I) infection. Recent evidence suggests a difference in the degree of the phenomenon between HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and asymptomatic HTLV-I carriers (AC). In this article, we demonstrated several alterations in the features of the in vitro transformed lymphocytes between patients with HAM/TSP (n = 16) and AC (n = 8). The percentages of total CD8+ and CD8+CD28+ cells were significantly increased in the in vitro proliferating T lymphocytes derived from the patients with HAM/TSP when compared to those from AC. HAM/TSP was segregated from AC by the high degree of the proliferation of CD8+CD28+ cells. The expression of HTLV-I-specific antigens on the cultured PBLs was detected only in the subjects which showed low CD8+CD28+/CD4+ ratio of the in vitro proliferating lymphocytes. These findings suggest that this phenomenon distinguishes HAM/TSP from AC, not only in quantity but also in quality.  相似文献   
75.
Endocrine tumor of the pancreas is potentially malignant. A multicenter analysis of these tumors was conducted to clarity the present status of their surgical management and the subsequent long-term surgical results. The Japan pancreatoduodenectomy (JPD) study group carried out the study; 368 patients were enrolled and variables related to tumor characteristics, surgery, and survival were retrospectively analyzed. There were 222 patients with functioning tumor and 143 patients with nonfunctioning tumor. Malignant tumor was found in 140 of 368 (38%) of the patients, and 63/140 (45%) of these patients had metastatic lesion; the most common site of the metastasis was liver 34/136 (25%), followed by regional lymph nodes 26/136 (19%). Pancreatic resection was performed in 91% of patients with nonfunctional tumor and in 83% of those with malignant tumor, and 73% of the pancreatic resections were done with lymph node dissection. The overall 5-year actuarial survival rate was 76% in patients with malignant tumor. The actuarial 5-year survival rate was 93% in the patients without metastasis and 83% in patients who received curative resection. Multivariate analysis showed that the presence or absence of synchronous metastasis was the sole significant prognostic factor. The results suggest that: (i) malignant endocrine tumor of the pancreas is a curable malignancy when pancreatic resection with lymph node dissection is adopted and (ii) that synchronous metastasis is the dominant prognostic factor. This study was carried out as a group project. The authors' institutions are as follows  相似文献   
76.
We have developed a sensitive enzymatic-immunoassay to quantify the level of gamma-enolase (a specific neuronal enzyme) which is released from cultured cells after exposure to various toxins. We show that this method can estimate selectively neuronal cell death without significantly interfering with glial cell death. Indeed, no gamma-enolase is released when glial cells are killed with free-radical producing agents. Experiments comparing the levels of neuronal cell death induced by NMDA or free-radical producing drugs, performed either by measuring gamma-enolase release or using the classical fluorescein diacetate method, yielded similar results. In addition to selectively follow neuronal death in a mixed population of neurons and glial cells, this method provides a way of determining the cell death kinetics from a single culture dish, since enolase can be measured on small samples taken from the culture medium. Finally, we propose these two methods as being complementary and useful neuronal and other cellular death indexes and also to understand the complex problem of glial influence on neuronal survival or death.  相似文献   
77.
 The case of a 49-year-old man with Maffucci’s syndrome, who developed multiple spindle cell hemangioendotheliomas, is presented. The case provides support for recent reports suggesting an association between this peculiar vascular lesion and skeletal enchondromatosis.  相似文献   
78.
79.
Azathioprine, a well-known immunosuppressive agent, is used extensively in renal transplantation. There have been several case reports of pure red cell aplasia induced by this drug following a successful kidney transplant. Previous management of azathioprine-induced red cell aplasia included reduction of azathioprine dose, or treatment with cyclophosphamide. We propose the substitution of cyclosporine for azathioprine, in this clinical setting. Not only does cyclosporine allow recovery of bone marrow function, but it maintains a level of immunosuppression which stabilizes renal function in the post-transplant patient.  相似文献   
80.
The aim of this study was to investigate markers of serotonin and immune function in suicidal patients. Cytotoxic activity of natural killer cells (NK) and CD16 lymphocytes were studied in 28 suicide attempters and 26 healthy controls, and related in patients to 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF). Patients with CSF 5-HIAA below the median had significantly lower NK cell activity than other patients. CD16 cell frequency was significantly lower in patients than in controls, and patients also tended to have lower NK cell cytotoxicity than healthy controls. There were no statistically significant correlations between 4-hydroxy-3methoxyphenyl glycol (HMPG), homovanillic acid (HVA), CSF cortisol and NK cell activity. The results support the hypothesis of compromised immune function in suicidal patients with evidence of disordered serotonin function.  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