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   34717篇
  免费   2157篇
  国内免费   284篇
耳鼻咽喉   446篇
儿科学   618篇
妇产科学   510篇
基础医学   4271篇
口腔科学   1577篇
临床医学   2831篇
内科学   9203篇
皮肤病学   446篇
神经病学   3520篇
特种医学   1394篇
外科学   5714篇
综合类   100篇
一般理论   6篇
预防医学   1458篇
眼科学   594篇
药学   1809篇
中国医学   74篇
肿瘤学   2587篇
  2024年   34篇
  2023年   365篇
  2022年   687篇
  2021年   1272篇
  2020年   757篇
  2019年   1036篇
  2018年   1220篇
  2017年   985篇
  2016年   1086篇
  2015年   1153篇
  2014年   1495篇
  2013年   1830篇
  2012年   2828篇
  2011年   2745篇
  2010年   1528篇
  2009年   1406篇
  2008年   2216篇
  2007年   2312篇
  2006年   2090篇
  2005年   1914篇
  2004年   1700篇
  2003年   1586篇
  2002年   1381篇
  2001年   338篇
  2000年   313篇
  1999年   304篇
  1998年   261篇
  1997年   220篇
  1996年   168篇
  1995年   150篇
  1994年   135篇
  1993年   112篇
  1992年   144篇
  1991年   127篇
  1990年   109篇
  1989年   92篇
  1988年   115篇
  1987年   98篇
  1986年   71篇
  1985年   81篇
  1984年   65篇
  1983年   72篇
  1982年   54篇
  1981年   45篇
  1980年   34篇
  1979年   56篇
  1978年   48篇
  1977年   34篇
  1975年   36篇
  1973年   45篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Introduction Postoperative treatment for colorectal cancer depends on tumor stage as defined by the International Union Against Cancer (UICC). Adjuvant chemotherapy is not recommended in patients without lymph node involvement (UICC stages I and II). As many as 20–30% of these patients, however, will develop recurrence. Aims and objectives We conducted this study to determine the presence of disseminated tumor cells in the lymph nodes by quantitative real-time polymerase chain reaction (QRT-PCR) for cytokeratin 20 (CK20) in an attempt to provide supplementary information compared to histopathological findings. Materials and methods Using a standard QRT-PCR assay, we examined primary tumors and 391 lymph nodes from 31 patients with completely resected colorectal cancer. Results Of the 31 primary tumors, 29 were positive for CK20 by QRT-PCR. Discussion An examination of the lymph nodes from the 29 patients with CK20-positive primary tumors revealed that 35 (92.1% sensitivity) of the 38 histopathologically positive lymph nodes and 54 (16.7%) of the 324 histopathologically negative lymph nodes were positive by molecular analysis. CK20 expression was detected in 10 (100%) of 10 patients with a histopathologically positive lymph node status (pN1). In 9 (47.4%) of 19 patients with negative histopathological results (pN0), we detected a CK20 mRNA signal in at least one lymph node. Whereas eight patients with histopathologically negative lymph nodes could be upstaged on the basis of the molecular findings, no patient would be downstaged. Conclusion Our results suggest that QRT-PCR for CK20 is a useful tool for the quantitative detection of micrometastases in the regional lymph nodes. We introduce a standardized procedure that integrates a molecular diagnostic technique in the clinical staging.  相似文献   
102.
103.
104.
105.
106.
To analyse the effect of concomitant cognitive or motor task performance on balance control in Parkinson's disease (PD), we performed a posturographic study in 24 PD patients and in 20 sex- and age-matched control subjects. Postural sway was measured with eyes open (EO) and eyes closed (EC) during quiet stance and during performance of calculation or motor sequence of thumb opposition to the other fingers. No difference of centre of foot pressure (COP) parameters was observed during quiet standing (either EO or EC) between patients and controls, but visual deprivation induced in both groups a worsening of postural stability. COP area was significantly increased in PD patients during dual task performance, whereas no difference of COP path and x-y axes was observed. The effects induced by the performance of cognitive or motor task were significantly more evident in PD patients with clinical evidence of postural instability (presence of prior falls in the history). This study demonstrates that dual task interference on postural control can be observed in PD patients during performance of cognitive as well as motor tasks. The balance deterioration during dual task performance was significantly enhanced in patients with history of prior falls. These findings have some implications for the strategies to be used in reducing the risk of fall in PD.  相似文献   
107.
P F Piguet  C Vesin  J Guo  Y Donati    C Barazzone 《Immunology》1998,95(1):111-116
We explored the thrombocytopaenia elicited by the i.v. injection of mouse recombinant tumour necrosis factor (TNF) in mice. Injection of 10 micrograms of TNF led to a thrombocytopaenia (evident after 0.5 hr) which was caused by decreased platelet survival, as seen by the injection of labelled platelets. TNF-induced thrombocytopaenia was not prevented by heparin, nor by depletion of either fibrinogen or C'. TNF-induced thrombocytopaenia was markedly attenuated in mice treated with reserpine, an agent that depletes monoamines from mast cells and other cells, and in the mast-cell-deficient WWv mice. In vitro, TNF elicited a modest release of monoamine from peritoneal mast cells and from a mast cell line. When mice are injected with 3H-serotonin (3H-5HT) before TNF, TNF injection increased the plasma 3H-5HT content 1 hr later, modifications absent in reserpine pretreated or mast-cell-deficient mice. 3H-5HT content of the small intestine was markedly depleted in TNF-injected mice, suggesting that this organ is the source of the plasma 3H-5HT. Drop in body temperature and mortality induced by TNF were also attenuated in mast-cell-deficient, and in reserpine pretreated mice. These results indicate that TNF can induce a release of monoamines from mast cells, mainly from those of the small intestine, a process that contributes to TNF-induced thrombocytopaenia and mortality.  相似文献   
108.
The specific humoral immune response against Epstein-Barr virus (EBV) antigens in patients with nasopharyngeal carcinoma (NPC) was compared to that of patients with infectious mononucleosis (IM) and other EBV-seropositive subjects using immunoblotting technique. Almost all sera from E,BV serologically associated NPC reacted reproducibly with a major group of polypeptides (four to six) of early antigen (EA) complex with molecular weights ranging from 50 kD to 58 kD, and with some additional polypeptides. Sera from IM-patients reproducibly recognized only one polypeptide of 50 kD belonging to the major group of polypeptides of EA-complex. Sera from patients with other types of head and neck cancer and relatively high levels of IgG antibody against viral capsid antigen (VCA) and EA did not react reproducibly with any of the EBV-associated proteins.  相似文献   
109.
In children, several neurological disorders are characterised by spongiform leukoencephalopathy. MRI of the brain typically shows white matter swelling, but does not enable differentiation of the various underlying disorders. The aim of this article is optimisation of the diagnostic value of MRI in leukoencephalopathy accompanied by swelling. MRI-based inclusion criteria were met by 20 patients in our database. The images were analysed using a detailed scoring list. In 13 of the 20 patients the clinical diagnosis was known (11 definite and 2 probable diagnoses). Characteristic MRI abnormalities could be defined in these patients. Of the 7 patients without a diagnosis, 5 had identical MRI abnormalities: difuse hemisphere swelling and typical cysts in frontoparietal subcortical white matter and the tips of the temporal lobes. The clinical picture was also similar in these patients, suggesting a similar disease.  相似文献   
110.
Serum immunoglobulins and the activity of natural killer (NK) cells of 50 epileptic patients (eight with idiopathic generalized epilepsy and 42 with cryptogenic partial epilepsy) and 28 controls have been studied. The values of IgA, IgG and IgM were the same-in patients and controls. The NK activity in controls was linearly related to the effector-to-target ratio, but this linear relationship was not observed in epileptic patients. The cytotoxic activity of NK cells at the lowest effector-to-target ratio was significantly greater in patients than in controls. This increase was observed in each therapy group. Our results seem to confirm a disturbance of the immune system in epileptic patients and suggest that this modification of cellular immunity is not a drug effect but is related to the illness itself.  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