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   492篇
  免费   22篇
  国内免费   20篇
儿科学   24篇
基础医学   43篇
口腔科学   9篇
临床医学   48篇
内科学   141篇
皮肤病学   4篇
神经病学   7篇
特种医学   157篇
外科学   19篇
综合类   11篇
预防医学   14篇
眼科学   2篇
药学   26篇
  2篇
肿瘤学   27篇
  2023年   2篇
  2021年   1篇
  2020年   1篇
  2018年   4篇
  2017年   1篇
  2016年   1篇
  2015年   3篇
  2014年   2篇
  2013年   5篇
  2012年   4篇
  2011年   4篇
  2010年   6篇
  2009年   9篇
  2008年   5篇
  2007年   21篇
  2006年   8篇
  2005年   9篇
  2004年   5篇
  2003年   8篇
  2002年   14篇
  2001年   4篇
  2000年   17篇
  1999年   14篇
  1998年   29篇
  1997年   27篇
  1996年   28篇
  1995年   25篇
  1994年   22篇
  1993年   25篇
  1992年   10篇
  1991年   8篇
  1990年   10篇
  1989年   33篇
  1988年   17篇
  1987年   26篇
  1986年   16篇
  1985年   28篇
  1984年   13篇
  1983年   13篇
  1982年   7篇
  1981年   8篇
  1980年   11篇
  1979年   5篇
  1978年   3篇
  1977年   12篇
  1976年   7篇
  1974年   1篇
  1966年   1篇
  1965年   1篇
排序方式: 共有534条查询结果,搜索用时 15 毫秒
81.
Because of the variable clinical course of multiple myeloma, the identification of prognostic parameters is of clinical interest. Therefore, we analyzed the clinical significance of serum levels of soluble human leukocyte antigen class I molecules (sHLA-I), carboxy-terminal telopeptide of type-I collagen (ICTP), and receptor activator of nuclear factor kappa B ligand (RANKL). Compared with controls, sHLA-I were threefold (p < 0.001) elevated in multiple myeloma. Increased levels of ICTP and RANKL were demonstrated in 50 and 43% of patients, respectively. sHLA-I correlated significantly with stage of disease. Serial determination of sHLA-I in 11 patients revealed significantly higher sHLA-I levels (median [range] mug/l) during active disease than during remission (700 [250-2090] versus 380 [130-920]). ICTP demonstrated an association with stages of disease and the presence of osteolytic lesions, whereas there were no differences with respect to active/remittent disease. Importantly, levels of sHLA-I > or = 1000 microg/l and ICTP > or = 5 microg/l were significantly associated with a poor overall survival. For RANKL, no significant associations were observed with disease stages, disease status, osteolytic lesions, and survival. In conclusion, sHLA-I and ICTP serum levels seem to be of prognostic significance in multiple myeloma and might be helpful to identify patients of poor prognosis.  相似文献   
82.

Background

The purpose of the project was to delineate a series of contiguous neighbourhood-based "Data Zones" within the Region of Peel (Ontario) for the purpose of health data analysis and dissemination. Zones were to be built on Census Tracts (N = 205) and obey a series of requirements defined by the Region of Peel. This paper explores a method that combines statistical analysis with ground-truthing, consultation, and the use of a decision tree.

Data

Census Tract data for Peel were derived from the 2006 Canadian Census Master file.

Methods

Following correlation analysis to reduce the data set, Principal Component Analysis was applied to the data set to reduce the complexity and derive an index. The Getis-Ord Gi*statistic was then applied to look for statistically significant clusters of like Census Tracts. A detailed decision tree for the amalgamation of remaining zones and ground-truthing with Peel staff verified the resulting zones.

Results

A total of 15 Data Zones that are similar with respect to socioeconomic and sociodemographic attributes and that met criteria defined by Peel were derived for the region.

Conclusion

The approach used in this analysis, which was bolstered by a series of checks and balances throughout the process, gives statistical validity to the defined zones and resulted in a robust series of Data Zones for use by Peel Public Health. We conclude by offering insight into alternative uses of the methodology, and limitations.  相似文献   
83.
前列腺特异抗原研究进展与挑战(摘要)   总被引:1,自引:0,他引:1  
前列腺特异抗原(PSA)发现四分之一世纪以来,已成为诊断前列腺癌最有价值的肿瘤标志物。前列腺癌在男性癌症发病中占首位。自从80年代中期第一代检测PSA的方法问世以来,前列腺癌的发病率有了显著改变。这部分归功于PSA检测的增加,从而使前列腺癌得到早期诊断,这有利于将癌症控制在发病早期,增加治愈的可能性。虽然PSA是一个有效的肿瘤标志物,并具有器官特异性,但其癌症特异性不高。PSA升高也可见于其他良性前列腺疾病,尤其当PSA浓度在4~10μg/L时。这个浓度范围被称为“诊断灰色区域”。对PSA分子结构的研究主要集中…  相似文献   
84.
The combination of high-dose busulfan (16 mg/kg) and 200 mg/kg cyclophosphamide is gaining increasing significance as a preparative regimen prior to autologous, syngeneic, or allogeneic marrow transplantation. A new regimen of high-dose busulfan in conjunction with a reduced dose of 120 mg/kg cyclophosphamide has recently been described as a preparative regimen prior to allogeneic transplantation. To determine the drug-related nonhematologic toxic effects of this new regimen without confounding factors associated with allogeneic transplantation, we conducted a pilot study using this new regimen in 20 patients with acute myeloid leukemia (AML) in first remission prior to autologous unpurged marrow transplantation. All patients experienced transient non-life-threatening acute drug-related toxicity with skin reactions in 20 (100%), nausea and vomiting in 20 (100%), oral mucositis in 18 (90%), hepatic functional impairment in 17 (85%), hemorrhagic cystitis in three (15%), and generalized seizures in two (10%) of these patients, respectively. Two procedural, fatal complications resulted from infectious causes that were not directly related to the speed of hematopoietic reconstitution or the toxicity of the preparative regimen. The 3-year event-free survival estimate (55% +/- 11%) and probability of leukemic recurrence (38% +/- 11%) attained with this new regimen in recipients of autografts in first remission of AML are promising and challenge comparisons with preparative regimens employing combinations of cytotoxic agents or total body irradiation (TBI).  相似文献   
85.
Baldwin  GC; Golde  DW; Widhopf  GF; Economou  J; Gasson  JC 《Blood》1991,78(3):609-615
Hematopoietic growth factor receptors are present on cells of normal nonhematopoietic tissues such as endothelium and placenta. We previously demonstrated functional human granulocyte-macrophage colony- stimulating factor (GM-CSF) receptors on small cell carcinoma of the lung cell lines, and others have reported that certain solid tumor cell lines respond to GM-CSF in clonogenic assays. In the current study, we examine human melanoma cell lines and fresh specimens of melanoma to determine whether they have functional GM-CSF receptors. Scatchard analyses of 125I-GM-CSF equilibrium binding to melanoma cell lines showed a mean of 542 +/- 67 sites per cell with a kd of 0.72 +/- 0.14 nmol/L. Cross-linking studies in the melanoma cell line, M14, showed a major GM-CSF receptor species of 84,000 daltons. Under the conditions tested, the M14 cells did not have a proliferative response to GM-CSF in vitro, nor was any induction of primary response genes detected by Northern analysis in response to GM-CSF. Studies to determine internal translocation of the receptor-ligand complex indicated less than 10% of the 125I-GM-CSF internalized was specifically bound to receptors. Primary melanoma cells from five surgical specimens had GM-CSF receptors; Scatchard analysis was performed on one sample, showing 555 sites/cell with a kd of 0.23 nmol/L. These results indicate that human tumor cells may express a low-affinity GM-CSF receptor protein that localizes to the cell surface and binds ligand, but lacks functional components or accessory factors needed to transduce a signal.  相似文献   
86.
Although arachidonic acid causes rabbit platelet aggregation and the release of granule contents in suspensions of washed platelets when used in concentrations of approximately 50-300 microM, higher concentrations (500 microM) cause neither aggregation nor release. Suspensions of platelets from rabbits wee exposed to arachidonic acid (250 microM) for 15 min, allowed to recover in the presence of PGE1 for 30 min, washed, and resuspended; in some experiments, the platelets were treated with aspirin before being exposed to arachidonic acid. Aggregation of platelets pretreated with arachidonic acid was inhibited in response to ADP; this effect was greater with the non-aspirin- treated platelets and persisted for at least 4 hr after resuspension. The association of 125I-fibrinogen with the platelets as a result of ADP stimulation was also inhibited. Aggregation and release of granule contents in response to collagen and low concentrations of thrombin was inhibited, but the inhibition could be overcome by higher concentrations. Thrombin induced further release of granule contents from platelets exposed to arachidonic acid without pretreatment with aspirin. Platelets that had been exposed to arachidonic acid, either with or without pretreatment with aspirin, did not aggregate or undergo further release upon stimulation with arachidonic acid after they were washed and resuspended. Inhibition of the lipoxygenase pathway with eicosatetraynoic acid (ETYA) or nordihydroguaiaretic acid (NDGA) did not affect the inhibition caused by arachidonic acid, so it is unlikely that a product of this pathway is responsible for the inhibition. Mixing experiments indicated that the pretreated platelets did not form a thromboxane-A2-like activity, and that they were unresponsive to aggregation and release induced by products formed from arachidonic acid. Experiments with 3H-arachidonic acid showed that after 45 min of incubation with platelets, only 1.1% of the 3H-arachidonic acid remained as free arachidonic acid in the platelets. Although cyclic-AMP was slightly increased 1 min after the addition of arachidonic acid, the cyclic-AMP concentration was the same as that of control platelets after the platelets were washed and resuspended, indicating that increased cyclic-AMP is not likely to be responsible for the persistent inhibitory effect. Thus, the inhibitory effect of pretreatment with arachidonic acid is a general effect on responses to a variety of aggregating agents that act through different mechanisms, and the inhibition is not related to thromboxane-A2 formation. The possibility of membrane perturbation resulting in the unavailability of receptors may explain the persistent inhibitory effect, but the responsible reactions have not been identified.  相似文献   
87.
Datta  R; Banach  D; Kojima  H; Talanian  RV; Alnemri  ES; Wong  WW; Kufe  DW 《Blood》1996,88(6):1936-1943
The response of human myeloid leukemia cells to treatment with 1-beta- arabinofuranosylcytosine (ara-C) includes the induction of apoptosis. Ara-C induced apoptosis is associated with proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) and protein kinase C (PKC) delta. However, the signals involved in this response are unknown. The present studies show that ara-C treatment of U-937 cells is associated with induction of a protease activity that cleaves the tetrapeptides Ac-DEVD- pNA and Ac-DMOD-pNA found at the cleavage sites of PARP and PKC delta, respectively. The ara-C-induced protease activity was sensitive to overexpression of the anti-apoptotic protein Bcl-xL and the baculovirus protein p35. By contrast, overexpression of the cowpox virus protein CrmA blocked apoptosis induced by engagement of the Fas receptor but not that induced by ara-C. CrmA overexpression also had no detectable effect on ara-C-induced cleavage of PKC delta. The results further show that ara-C induces activation of the CPP32 protease by a CrmA- insensitive and p35-sensitive mechanism. Similar results were obtained with cisplatinum, etoposide, and camptothecin. These findings indicate that ara-C and other DNA-damaging agents activate a CrmA-insensitive apoptotic pathway involving CPP32 and that these signals differ from those associated with apoptosis induced by the Fas receptor.  相似文献   
88.
89.
Accuracy of the detailed per-oral small bowel series and enteroclysis was compared in 134 patients known to have (or not have) disease of the small bowel. Overall sensitivity of the per-oral examination was 92% and specificity 94%, compared to 94% and 89%, respectively, for enteroclysis. There was no difference between the two in Crohn disease, adhesions, and metastatic disease; however, enteroclysis was thought to be more effective in delineating peritoneal adhesions in patients with obstruction. The authors conclude that while the per-oral study and enteroclysis are equally valid methods of examining the small bowel, the per-oral study is preferable as a screening examination because it requires less time, has fewer side effects, and involves a lower radiation exposure.  相似文献   
90.
MacEwan  DW 《Radiology》1987,163(2):559-563
Eleven radiologists appointed by the major radiological societies participated for the past 5 years in the development of the Health Policy Agenda for the American People. The Agenda is an action plan to address a wide variety of serious problems in medicine. The first phase involved establishment of 159 principles, broad value statements that were the foundation of the project. Phase 2 involved the development of policy proposals on 38 urgent issues for action in medical science; education; health resources; delivery mechanisms; evaluation, assessment, and control; and payment for services. These proposals are summarized in this report. The activities and recommendations of representatives for the field of radiology are described. The Agenda has been released, and an implementation phase has begun. It will likely be of great importance to the practice of radiology over the next decade. Important issues can be addressed by acting with the coalitions that are being formed from among the more than 150 participating organizations.  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