全文获取类型
收费全文 | 714篇 |
免费 | 30篇 |
国内免费 | 14篇 |
专业分类
儿科学 | 46篇 |
妇产科学 | 4篇 |
基础医学 | 60篇 |
口腔科学 | 17篇 |
临床医学 | 109篇 |
内科学 | 132篇 |
皮肤病学 | 10篇 |
神经病学 | 14篇 |
特种医学 | 191篇 |
外科学 | 31篇 |
综合类 | 32篇 |
预防医学 | 52篇 |
眼科学 | 2篇 |
药学 | 46篇 |
肿瘤学 | 12篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 17篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 21篇 |
2010年 | 13篇 |
2009年 | 23篇 |
2008年 | 14篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 15篇 |
2004年 | 7篇 |
2003年 | 13篇 |
2002年 | 4篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 23篇 |
1998年 | 43篇 |
1997年 | 48篇 |
1996年 | 38篇 |
1995年 | 39篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 14篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 18篇 |
1981年 | 12篇 |
1980年 | 22篇 |
1979年 | 4篇 |
1978年 | 12篇 |
1977年 | 22篇 |
1976年 | 12篇 |
1975年 | 8篇 |
1963年 | 2篇 |
排序方式: 共有758条查询结果,搜索用时 15 毫秒
161.
The mechanism of thrombin-induced platelet factor 4 secretion 总被引:15,自引:1,他引:15
We have measured thrombin-induced secretion of platelet factor 4 antigen (PF4) and simultaneously followed its intracellular translocation by immunofluorescence. In permeable resting platelets, speckled intracellular immunofluorescent staining for PF4 was observed. Addition of thrombin to washed platelets at 22 degrees C resulted in secretion of PF4 and formation of large (approximately 0.5 micrometer) immunofluorescent masses. These masses moved to the cell periphery during secretion and were virtually absent at the conclusion of secretion. Ultrastructural examination of thrombin-treated platelets revealed vacuoles corresponding in size, shape, and time of occurrence to the large immunofluorescent masses of PF4. These vacuoles contained PF4 by immunoferritin staining of frozen thin sections; they therefore appear to represent the ultrastructural counterpart of the large PF4 masses. When intact cells were stained for PF4 after thrombin addition, only 5.6% of the large masses stained. Thus, during secretion, PF4 antigen is consolidated into large closed pools that appear as vacuoles in the electron microscope. 相似文献
162.
Hemoglobin variants having electrophoretic mobility more rapid than that of HbA were identified in combination with sickle hemoglobin in two patients at the Cook County Hospital. Neither individual had symptomatic hematologic disease. In one patient, the rapidly migrating hemoglobin had the amino acid substitution characteristic of Hb Tacoma (beta-40 arg leads to ser), a mildly unstable variant. In the other patient, Hb Camden (beta-131 gln leads to glu) was identified, and the hematologic findings also indicated that he has alpha-thalassemia trait. In the patient with HbS-Camden--alpha-thalassemia, globin synthesis was unbalanced (alpha/beta 0.66), and HbS represented only 19.5% of the total hemoglobin. The latter finding suggests that under conditions of limited alpha-chain availability beta Camden may combine with alpha subunits at least as efficiently as does betaA. HbS represented 56% of the hemoglobin of the patient with HbS Tacoma, although the rate of synthesis of beta Tacoma by her reticulocytes was consistently greater than that of betaS. A time-course synthesis study demonstrated a progressive increase in the specific activity of beta Tacoma in relation to that of betaS, suggesting that the unstable beta- chains of Hb Tacoma underwent selective intracellular degradation. This process appears to explain the disparity between the rates of synthesis of the two beta chains and the relative representation of HbS and Hb Tacoma in the patient's erythrocytes. 相似文献
163.
Brashem-Stein C; Flowers DA; Smith FO; Staats SJ; Andrews RG; Bernstein ID 《Blood》1993,82(3):792-799
We have identified a molecule expressed by human marrow granulocyte/monocyte colony-forming cells (CFU-GM), erythroid colony- forming cells (CFU-E), and erythroid burst-forming units (BFU-E), but not their precursors detectable in long-term bone marrow culture. This antigen, detected by flow microfluorimetry using monoclonal antibody 7B9, is coexpressed with CD33 on many CD34+ CFCs, although only the 7B9 antigen was detected on a portion of BFU-E and CFU-E, whereas only CD33 was found on a portion of CFU-GM. Antibody 7B9 appears to be useful for isolating subsets of progenitors based on their common or selective expression of 7B9 antigen and CD33. 相似文献
164.
We have previously shown that mice induced to overexpress thrombopoietin (TPO) by retroviral-mediated gene transfer into bone marrow (BM) cells develop myelofibrosis and osteosclerosis. It was speculated that these effects were secondary to TPO, resulting from high levels of megakaryocytes and platelets. Also, it was proposed that these mice represent a model for myelofibrosis and osteosclerosis. In this report, we show that levels of both transforming growth factor- beta 1 and platelet-derived growth factor are increased twofold to fivefold in the platelet-poor plasma of TPO overexpressing mice compared with control mice. These data suggest that the increased megakaryocytes produce elevated levels of these cytokines that lead to the pathogenesis of disease. Further, we retransplanted TPO overexpressing mice, at 40 to 42 weeks after primary transplantation, with normal BM cells. After the secondary transplantation, megakaryocytes and platelets returned to normal levels and the myelofibrosis and osteosclerosis were completely corrected. These data extend our initial studies of the effects of overexpression of TPO and show the potential use of this model to explore the underlying cause of myelofibrosis and osteosclerosis and potential treatments for these diseases. 相似文献
165.
166.
Dipyridamole, an inhibitor of platelet aggregation, has been shown to have beneficial effects in disorders characterized by extravascular fibrin deposition. Mononuclear phagocytes are present in extravascular sites and are capable of expressing both plasminogen activator and procoagulant activities, which suggests these cells play a central role in extravascular fibrin turnover. We therefore sought to determine whether dipyridamole affects the expression of plasminogen activator and procoagulant activities by rabbit alveolar macrophages cultured in vitro. We found that dipyridamole (10 to 100 mumol/L) caused increases in both cell-associated and released plasminogen activator activity, which reached levels of 240% (P less than .05) and 543% (P less than .01) of controls, respectively. In contrast, dipyridamole decreased the cell-associated procoagulant activity of alveolar macrophages to as little as 21.3% of controls (P less than .01). Similar effects were seen in cells cotreated with lymphokines. The procoagulant activity expressed by these cells functioned as a tissue thromboplastin. The plasminogen activator of control and treated cells was a urokinase as determined by molecular weight characteristics (50 kilodaltons) and by antibody neutralization profiles using polyclonal antibodies against human urokinase and tissue plasminogen activator. These effects of dipyridamole could not be duplicated by structurally dissimilar agents sharing some of the pharmacological actions of dipyridamole; however, two pyrimidopyrimidine compounds structurally similar to dipyridamole effectively mimicked the effects on both procoagulant and plasminogen activator activities. We conclude that dipyridamole may have antithrombotic effects by directly modulating the role of mononuclear phagocytes in fibrin turnover. Thus, dipyridamole may be useful in situations where extravascular fibrin deposition is important to the pathogenesis of tissue injury and repair. 相似文献
167.
RS McLeod BG Wolff AH Steinhart PW Carryer K O'Rourke DF Andrews JE Blair JR Cangemi Z Cohen JB Cullen RG Chaytor GR Greenberg NM Jaffer KN Jeejeebhoy RL MacCarty RL Ready LH Weiland 《Gastroenterology》1997,113(6):1823-1827
BACKGROUND & AIMS: The aim of this study was to determine the risk of endoscopic/radiological recurrence of Crohn's disease postoperatively and the long-term outcome. METHODS: A randomized placebo-controlled trial was performed to determine the effectiveness of mesalamine in preventing recurrent Crohn's disease postoperatively. Patients in the control group were examined endoscopically/radiologically before entry into and annually during the trial. Findings were classified as minimal or severe. RESULTS: There were 76 patients (49 men and 37 women; mean age, 37.1 +/- 13.2 years). Fifty (61.7%) had terminal ileal resections. Overall, 55 endoscopic/radiological recurrences were observed in 51 patients (67.1%). Expressed actuarially, the recurrence rate was 27.5% at 1 year (95% confidence interval [CI], 15.8%-37.6%), 60.8% at 2 years (95% CI, 46%-71.3%), and 77.3% at 3 years (95% CI, 62.7%-86.3%). Nineteen (37%) were symptomatic and 12 (24%) were initially asymptomatic but later became symptomatic (mean, 13.0 +/- 8.8 months), whereas 20 (39%) remained asymptomatic (mean, 16.9 +/- 17.4 months). Patients with severe endoscopic/radiological disease were significantly more likely to be or become symptomatic than those with minimal disease (23 of 32 vs. 8 of 19, respectively; P = 0.0437). CONCLUSIONS: This study suggests that postoperative endoscopic/radiological recurrences occur later than previously reported. Furthermore, many of these patients, especially with minimal disease, will remain asymptomatic. (Gastroenterology 1997 Dec;113(6):1823-7) 相似文献
168.
169.
170.
T Pézier P Stimpson RG Kanegaonkar DA Bowdler 《Annals of the Royal College of Surgeons of England》2009,91(2):147-151