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   1188篇
  免费   120篇
  国内免费   24篇
耳鼻咽喉   40篇
儿科学   22篇
妇产科学   11篇
基础医学   109篇
口腔科学   4篇
临床医学   191篇
内科学   301篇
皮肤病学   5篇
神经病学   104篇
特种医学   48篇
外科学   237篇
综合类   55篇
一般理论   1篇
预防医学   63篇
眼科学   18篇
药学   36篇
中国医学   5篇
肿瘤学   82篇
  2021年   11篇
  2020年   5篇
  2019年   6篇
  2018年   9篇
  2017年   10篇
  2016年   12篇
  2015年   18篇
  2014年   16篇
  2013年   19篇
  2012年   33篇
  2011年   33篇
  2010年   39篇
  2009年   29篇
  2008年   41篇
  2007年   68篇
  2006年   49篇
  2005年   41篇
  2004年   44篇
  2003年   46篇
  2002年   54篇
  2001年   38篇
  2000年   38篇
  1999年   34篇
  1998年   26篇
  1997年   23篇
  1996年   28篇
  1995年   13篇
  1994年   33篇
  1993年   18篇
  1992年   46篇
  1991年   31篇
  1990年   41篇
  1989年   54篇
  1988年   32篇
  1987年   27篇
  1986年   26篇
  1985年   20篇
  1984年   12篇
  1983年   19篇
  1982年   20篇
  1981年   16篇
  1980年   16篇
  1979年   24篇
  1978年   18篇
  1977年   19篇
  1976年   13篇
  1975年   11篇
  1974年   10篇
  1973年   13篇
  1972年   7篇
排序方式: 共有1332条查询结果,搜索用时 0 毫秒
71.
72.
73.
Initial work has shown that clonal B cells from B-chronic lymphocytic leukemia (B-CLL) are able to synthesize pro-angiogenic molecules. In this study, our goal was to study the spectrum of angiogenic factors and receptors expressed in the CLL B cell. We used ELISA assays to determine the levels of basic fibroblast growth factors (bFGF), vascular endothelial growth factor (VEGF), endostatin, interferon-alpha (IFN-alpha) and thrombospondin-1 (TSP-1) secreted into culture medium by purified CLL B cells. These data demonstrated that CLL B cells spontaneously secrete a variety of pro- and anti-angiogenic factors, including bFGF (23.9 pg/ml +/- 7.9; mean +/- s.e.m.), VEGF (12.5 pg/ml +/- 2.3) and TSP-1 (1.9 ng/ml +/- 0.3). Out of these three factors, CLL B cells consistently secreted bFGF and TSP-1, while VEGF was expressed in approximately two-thirds of CLL patients. Of interest, hypoxic conditions dramatically upregulated VEGF expression at both the mRNA and protein levels. We also employed ribonuclease protection assays to assay CLL B cell expression of a variety of other angiogenesis-related molecules. These analyses revealed that CLL B cells consistently express mRNA for VEGF receptor 1 (VEGFR1), thrombin receptor, endoglin, and angiopoietin. Further analysis of VEGFR expression by RT-PCR revealed that CLL B cells expressed both VEGFR1 mRNA and VEGFR2 mRNA. In summary, these data collectively indicate that CLL B cells express both pro- and anti-angiogenic molecules and several vascular factor receptors. Because of the co-expression of angiogenic molecules and receptors for some of these molecules, these data suggest that the biology of the leukemic cells may also be directly impacted by angiogenic factors as a result of autocrine pathways of stimulation.  相似文献   
74.
75.
Tomographic imaging of the myocardium was performed using a gamma camera and a 30-degree rotating slant-hole collimator to register 64 projections from a restricted-view angle. Section images were reconstructed with a two-dimensional filtered backprojection technique. Performance in terms of resolution, effects of misalignment, and three-dimensional activity distribution was evaluated in phantom studies. In a limited clinical study, ten consecutive patients were imaged both with single-photon emission computed tomography (SPECT) and the method described. In the new method, the camera was orientated in the 30 degrees left anterior oblique position with 15 degrees cranial tilt. Due to the short distance from the myocardium to the camera, resolution within reconstructed section images was high, the noise level was comparatively low, and the mean activity level in the posterior wall was significantly higher (p less than 0.005) than in SPECT.  相似文献   
76.
人尿中几种雄激素及蛋白同化激素的HPLC测定   总被引:3,自引:0,他引:3  
毕红钢  周同惠 《药学学报》1989,24(3):207-211
对HPLC分离及定量测定人尿中雄激素及蛋白同化激素的方法进行了初步研究。确定了六种甾体激素的分离条件及内标定量方法。固定相为C8键合硅胶,甲醇—乙腈—水(4:5:6)恒溶剂洗脱,程序流速。紫外检测器波长254 nm。检测限可至1 ng以下。本法采用Sep-Pak C18小柱进行尿样净化,回收率高而且稳定。操作简便快速。对尿样中甾体葡萄糖醛酸甙结合物的酶促水解条件也进行了初步探索。  相似文献   
77.
78.
79.
The effect of pulse intravenous methylprednisolone therapy followed by oral immunosuppression was evaluated in ten patients with idiopathic membranous glomerulonephritis who had developed progressive renal failure--a group generally considered to have a poor prognosis. The patients (six male, four female, mean age 50 years) were monitored over 9-30 months during which time creatinine clearance reduced from (mean +/- SEM) 83 +/- 10 to 29 +/- 6 ml/min, and plasma creatinine increased from 135 +/- 22 to 297 +/- 35 mumol/l. All patient were nephrotic with mean 24-h urinary protein excretion ranging from 5.8 to 19.6 g. Treatment administered was pulse intravenous methyl-prednisolone 1 g X 3 then oral prednisolone 30 mg and azathioprine 50 mg (nine patients) or cyclophosphamide 50 mg (one patient). Mean prednisolone dosage was 25 mg at 3 months, 16 mg at 6, and 10 mg at 12 months. Patients have been followed up for between 12 and 57 months on therapy. Creatinine clearance increased to 39 +/- 6, 47 +/- 5 and 48 +/- 18 ml/min after 3, 6 and 12 months treatment with a fall in proteinuria to 6.2 +/- 1.7, 5.7 +/- 1.4, and 3.1 +/- 1.1 g/24h. The deterioration of renal function was reversed in six patients (associated with a reduction in proteinuria to less than 1 g/24 hours in five), slowed in three (with a significant reduction in proteinuria in two), and only one patient with more advanced renal failure before treatment progressed to end-stage failure without any retardation of the rate of deterioration or change in proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
80.
1. Aprotinin (Trasylol) is a cationic 6500 Da polypeptide that inhibits proteolytic enzymes, and when labelled with 99mTc it is a reproducible marker for the renal tubular turnover of small filtered proteins in man. Lysine potently inhibits tubular peptide uptake, and may thus depress the uptake and metabolism of aprotinin. This was investigated in 14 glomerulonephritic patients with normal renal function and variable proteinuria and in one healthy subject. 2. 99mTc-labelled aprotinin was given intravenously alone, and again 3 days later, immediately after the intravenous administration of 3-6 g of lysine, followed by an infusion over 1 h of 0.3-1.9 g of lysine/kg in individual patients. Activity over kidneys and in urine was measured over 24 h and chromatography was used to separate the undegraded peptide from free isotope. 3. At the low dosage of lysine (< 0.8 g/kg) given to six patients, kidney activity (representing tubular uptake) was unchanged, but early urine samples contained some undegraded aprotinin. Urinary excretion of free isotope, representing tubular metabolism, fell from 1.6 +/- 0.2% of dose/h with no lysine to 0.9 +/- 0.1% of dose/h in the 24 h after lysine, suggesting suppression of tubular aprotinin degradation. Corrected fractional degradation was calculated from the mean urinary excretion of free isotope over a given interval, determined by chromatography, divided by the mean cumulative kidney counts over this same interval, and this also fell after lysine from 0.06 +/- 0.006 to 0.03 +/- 0.006 h-1 (P < 0.005) between 3.75 and 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)  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