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   4310篇
  免费   215篇
  国内免费   11篇
耳鼻咽喉   25篇
儿科学   94篇
妇产科学   54篇
基础医学   592篇
口腔科学   111篇
临床医学   259篇
内科学   1158篇
皮肤病学   29篇
神经病学   329篇
特种医学   121篇
外科学   850篇
综合类   6篇
一般理论   1篇
预防医学   143篇
眼科学   41篇
药学   319篇
中国医学   4篇
肿瘤学   400篇
  2023年   14篇
  2022年   30篇
  2021年   57篇
  2020年   33篇
  2019年   64篇
  2018年   64篇
  2017年   60篇
  2016年   47篇
  2015年   70篇
  2014年   89篇
  2013年   126篇
  2012年   163篇
  2011年   168篇
  2010年   91篇
  2009年   86篇
  2008年   166篇
  2007年   182篇
  2006年   187篇
  2005年   198篇
  2004年   202篇
  2003年   218篇
  2002年   218篇
  2001年   156篇
  2000年   161篇
  1999年   202篇
  1998年   65篇
  1997年   61篇
  1996年   83篇
  1995年   64篇
  1994年   59篇
  1993年   40篇
  1992年   141篇
  1991年   132篇
  1990年   127篇
  1989年   118篇
  1988年   138篇
  1987年   86篇
  1986年   80篇
  1985年   71篇
  1984年   66篇
  1983年   30篇
  1982年   13篇
  1981年   12篇
  1980年   11篇
  1979年   28篇
  1978年   10篇
  1977年   19篇
  1976年   5篇
  1975年   7篇
  1968年   3篇
排序方式: 共有4536条查询结果,搜索用时 13 毫秒
41.
42.
2-O-methylisohemigossylic acid lactone, a sesquiterpene, was purified from roots of mokumen (Gossampinus malabarica) and identified by Mass, and (1)H- and (13)-NMR. This sesquiterpene displayed strong growth inhibitory effect against human promyelotic leukemia HL-60 cells. Apoptotic morphological change of the nucleus, including chromatin condensation was induced in the HL-60 cells treated with the sesquiterpene. The fragmentation of DNA by the sesquiterpene to oligonucleosomal-sized fragments, a characteristic of apoptosis, was observed to be dose- and time-dependent in the HL-60 cells. Inhibitors of caspases suppressed the DNA fragmentation induced by the sesquiterpene. These findings suggest that growth inhibition by the sesquiterpene of HL-60 cells results from the induction of apoptosis by the sesqui-terpene, and that caspase cascade is involved in the induction of apoptosis by the compound in the HL-60 cells.  相似文献   
43.
The present study was designed to clarify the mechanism of adrenergic modulation of pancreatic glucagon secretion in rats under physiological conditions by 1) epinephrine infusion alone or together with adrenergic blockers and 2) administration of adrenergic agonists. Intravenous infusion of epinephrine alone (1 microgram/kg/min, equal to 0.7 nmol/kg/min) caused a significant increase in glucagon secretion. Phentolamine (an alpha blocker) or yohimbine (an alpha 2 blocker) administration completely inhibited the increase of glucagon secretion caused by epinephrine infusion, but neither the administration of bunazosin (an alpha 1 blocker) nor beta blockers inhibited it. Infusion of clonidine (an alpha 2 agonist) caused significant increase of glucagon secretion even at a low dose of 0.5 nmol/kg/min, although infusion of neither an alpha 1 nor a beta 2 agonist caused it even at the high dose of 40.0 nmol/kg/min. It is concluded that the alpha 2 receptor mechanism plays the most important role in the adrenergic modulation of glucagon secretion in rats under physiological conditions.  相似文献   
44.
We previously analysed the fragments of fibrin/fibrinogen degradation products (FDP) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with immunoblotting. In this report, we studied the semi-quantitative analysis of fibrinolysis (degradation of cross-linked fibrin) and fibrinogenolysis (degradation of fibrinogen and/or unstable fibrin) of patients' samples by our method. In vitro study of FDP made it clear that an appearance of D fragment confirmed fibrinogenolysis and an appearance of DD fragment and/or high molecular weight fragments which have higher molecular weight than DY or X fragment confirmed fibrinolysis. In addition, a study with mixtures of various concentrations of fibrin degradation products (FbDP) and fibrinogen degradation products (FgDP) demonstrated a dose dependent intensity of band by immunoblot method. These results show that our method is favorable for the semi-quantitative analysis of fibrinolysis and fibrinogenolysis. We applied the method to 6 samples from patients with disseminated intravascular coagulation (DIC). Consequently, fibrinogenolysis was observed in all of 6 samples, in which fibrinogenolysis was more enhanced than fibrinolysis in one sample, and an equivalent degree of fibrinolysis and fibrinogenolysis were observed in 3 of 6 samples. Although our method was probably devoid of the ability to distinguish FgDP from degradation products of unstable fibrin, these findings indicate that fibrinogenolysis is, at any rate, enhanced in the majority of patients with DIC, besides fibrinolysis.  相似文献   
45.
Two cases of long thoracic nerve palsy associated with thoracic outlet syndrome are reported. Both patients had abnormal posture, with low-set shoulders and winged scapulae. Clinically there was weakness of the serratus anterior muscle with partial denervotion on electromyography. The diagnosis of thoracic outlet syndrome was based on positive vascular tests and brachial plexus nerve compression symptoms induced by the vascular testing positions. An orthosis that held the shoulder in an elevated position was used in both cases. Complete recovery of shoulder function and relief of the symptoms was achieved in both cases at 8 and 13 months, respectively, after application of the orthosis.  相似文献   
46.
We performed a clinical phase III study with a galactosebased ecoo contrast agent, SH/TA-508, to evaluate its efficacy, safety, and usefulness for mass lesions in urology. SH/TA-508 was prepared as a suspension containing stabilized micro-air bubbles by adding water for injection just before use. SH/TA-508 was administered into the antecubital vein at an initial dose of 300 mg/ml × 5 ml followed by higher doses of 400 mg/ml × 4 ml, 300 mg/ ml × 10 ml or 400 mg/ml × 8 ml when a sufficient effect was not obtained. Efficacy was evaluated by color Doppler signal enhancement, the duration of blood flow signal enhancement, and improvement of diagnostic capacity. Fifty-nine patients with mass lesions in the kidney, prostate, testis, adrenal gland, and bladder were enrolled in the study. Up to the third dose the cumulative efficacy rates (≥2+) of color Doppler signal enhancement and duration of blood flow signal enhancement were 92% and 87%, respectively. Consequently, diagnostic capacity in 76% of the patients was remarkably improved. A light transient angialgia occurred in one patient but no other clinically significant changes were observed. It was confirmed that SH/TA-508 is a safe echo contrast agent that offers satisfactory color Doppler signal enhancement in the urologic organs mentioned above.  相似文献   
47.
We examined a major organ function during 3 h biventricular assisted circulation after acute myocardial infarction model in the pig. In left ventricular circulation, the outflow cannula was placed in the ascending aorta and an inflow cannula through the mitral valve in the left ventricle. A pump (pulsatile group, Zeon Medical, Inc., Tokyo, Japan and nonpulsatile group, Nikkiso HPM-15, Nikkiso, Inc., Tokyo, Japan) was connected to each cannula. In right ventricular circulation, the outflow cannula was placed in the pulmonary artery and an inflow cannula in the right ventricle. The right ventricular circulation was supported by a nonpulsatile pump (Nikkiso HPM-15). The items measured were the regional blood flows of the cortex and medulla in the kidney, white matter and gray mater in brain, and liver; renal arterial flow; carotid arterial flow; portal vein flow; common hepatic arterial flow; arterial ketone body ratio (AKBR); and lactate/pyrubic acid (L/P). In the pulsatile group, the renal cortical blood flow increased, and the medulla blood flow decreased. On the other hand, in the nonpulsatile group, both regional blood flows decreased. That means that in the pulsatile assisted group intrarenal redistribution improved rather than in the nonpulsatile assisted group. In addition the liver regional blood flow, AKBR, and L/P showed significant differences between the pulsatile and nonpulsatile groups. On the other hand, the white matter and gray matter regional blood flows and carotid arterial flow did not show significant differences between the groups. The results of our study indicated that pulsatile circulation produced superior circulation in the kidney and liver, and microcirculation on the cell level was superior as well in early treatment of acute heart failure.  相似文献   
48.
We examined anti-gelatin IgG in sera of children who suffered from systemic adverse reactions upon immunization with gelatin-containing live virus vaccines. In the group of 30 children who had immediate-type reactions and anti-gelatin IgE, 30 (100%) had anti-gelatin IgG and 29 (96%) had anti-gelatin IgG4. In another group of 75 children who had nonimmediate-type reactions and no anti-gelatin IgE, 22 (29%) had anti-gelatin IgG and six (8%) had IgG4. The IgG positivity well correlated with the lymphocyte proliferation assay positivity. In contrast, as a negative control, all 24 children who had no allergic reaction to live virus vaccines had no anti-gelatin IgG and IgG4. The results suggest that immune-response to gelatin may play a role in the pathogenesis of systemic nonimmediate-type reactions to the live virus vaccines.  相似文献   
49.
To clarify the pharmacological properties of (+)2-Methyl-4aalpha-(3-hydroxyphenyl)-1, 2, 3, 4, 4a, 5, 12, 12aalpha-octahydro-quinolino[2, 3, 3-g]isoquinoline ((+)-TAN-67), the effect of (+)-TAN-67 on the antinociception induced by the intrathecal (i.t.) administration of nociceptin/orphanin FQ was studied in mice using the tail-flick test and the formalin test. I.t. administration of (+)-TAN-67, at doses of 1 to 10 ng, facilitated the tail-flick response in a dose-dependent manner in mice. In addition, i.t. administration of (+)-TAN-67 (1 to 10 ng) in mice produced a marked pain-like aversive responses. I.t. pretreatment with D-Pro(9)-[spiro-gamma-lactam]-Leu(10)-Trp(11)-physalaemin(1-11) (GR82334, 0.1-1.0 nmol), a potent and selective tachykinin NK(1) receptor antagonist, dose-dependently blocked the reduction of the tail-flick response induced by (+)-TAN-67. Furthermore, (+)-TAN-67-induced facilitation of the tail-flick response was abolished in capsaicin-treated mice. On the other hand, (+)-TAN-67-induced flinching responses were dose-dependently and significantly reduced by i.t. pretreatment with GR82334 (0.1-1.0 nmol). The duration of i.t. (+)-TAN-67-induced flinching responses was significantly reduced in capsaicin-treated mice as compared with naive mice. I.t. administration of nociceptin/orphanin FQ (1-10 nmol) dose-dependently increased the tail-flick latency. I.t. administration of nociceptin/orphanin FQ (0.1-1.0 nmol) significantly and dose-dependently reduced the first-phase nociceptive response, but not the second-phase nociceptive response. I.t. pretreatment with (+)-TAN-67 (0.3-3.0 microg) for 30 min dose-dependently attenuated the antinociception induced by i.t. nociceptin (10 nmol) in the tail-flick test. Furthermore, the antinociceptive effect of nociceptin/orphanin FQ (1 nmol, i.t.) on the first-phase response in the formalin test was dose-dependently attenuated by s.c. pretreatment with (+)-TAN-67 (0.3-3.0 microg). (+)-TAN-67 (0.3-3.0 microg, i.t.), by itself, did not facilitate the tail-flick response or produce apparent behavioral changes. It is possible that (+)-TAN-67 has an antagonistic effect on nociceptin/orphanin FQ-induced antinociception.  相似文献   
50.
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