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   1138篇
  免费   78篇
  国内免费   4篇
耳鼻咽喉   7篇
儿科学   7篇
妇产科学   17篇
基础医学   129篇
口腔科学   6篇
临床医学   123篇
内科学   317篇
皮肤病学   7篇
神经病学   137篇
特种医学   22篇
外科学   115篇
综合类   6篇
预防医学   60篇
眼科学   13篇
药学   162篇
中国医学   2篇
肿瘤学   90篇
  2023年   15篇
  2022年   20篇
  2021年   43篇
  2020年   33篇
  2019年   34篇
  2018年   36篇
  2017年   33篇
  2016年   27篇
  2015年   39篇
  2014年   34篇
  2013年   51篇
  2012年   72篇
  2011年   96篇
  2010年   35篇
  2009年   27篇
  2008年   45篇
  2007年   59篇
  2006年   37篇
  2005年   37篇
  2004年   37篇
  2003年   23篇
  2002年   24篇
  2001年   15篇
  2000年   18篇
  1999年   9篇
  1998年   7篇
  1997年   8篇
  1996年   8篇
  1994年   8篇
  1993年   9篇
  1992年   24篇
  1991年   21篇
  1990年   22篇
  1989年   14篇
  1988年   14篇
  1987年   6篇
  1986年   15篇
  1985年   22篇
  1984年   15篇
  1983年   11篇
  1982年   14篇
  1981年   7篇
  1979年   11篇
  1978年   6篇
  1977年   10篇
  1975年   5篇
  1974年   5篇
  1973年   5篇
  1972年   6篇
  1971年   6篇
排序方式: 共有1220条查询结果,搜索用时 31 毫秒
71.
72.
Objective. Pregnancy‐associated plasma protein A (PAPP‐A) is expressed in eroded and ruptured atheromatous plaques, and circulating levels are elevated in acute coronary syndromes (ACS). Our objective was to investigate release patterns of PAPP‐A in ACS and whether they differ among different types of ACS. Methods. In 40 patients, PAPP‐A concentrations were measured in serially collected samples assessed by a novel ELISA technique. The patients were grouped according to type of ACS. Results. Release patterns for ST elevation myocardial infarction (STEMI) patients who underwent primary percutaneous coronary intervention (pPCI) showed a single substantial PAPP‐A increase shortly after pPCI, followed by an abrupt return to normal levels without secondary peaks. STEMI, high‐risk and low‐risk non‐ST elevation myocardial infarction/unstable angina pectoris (NSTEMI/UAP) patients without pPCI showed highly variable patterns with primary peaks followed by secondary PAPP‐A increases. All patients with elevated PAPP‐A levels reached the upper reference level within 24?h. There was a significant difference in median peak levels between STEMI (23.2?mIU/L) and low‐risk ACS patients (6.35?mIU/L) (p = 0.004) and between high‐risk (median = 15.3?mIU/L) and low‐risk ACS patients (p = 0.01). Among high‐risk ACS patients, NSTEMI patients had significantly higher peak levels than UAP patients (p = 0.003). Conclusion. PAPP‐A serum levels increase above normal values within 24?h after onset of symptoms in ACS. There are significant differences in PAPP‐A peak levels and release patterns across the spectrum of ACS patients.  相似文献   
73.
74.
75.
76.
A method for obtaining strongly polarized nuclear spins in solution has been developed. The method uses low temperature, high magnetic field, and dynamic nuclear polarization (DNP) to strongly polarize nuclear spins in the solid state. The solid sample is subsequently dissolved rapidly in a suitable solvent to create a solution of molecules with hyperpolarized nuclear spins. The polarization is performed in a DNP polarizer, consisting of a super-conducting magnet (3.35 T) and a liquid-helium cooled sample space. The sample is irradiated with microwaves at approximately 94 GHz. Subsequent to polarization, the sample is dissolved by an injection system inside the DNP magnet. The dissolution process effectively preserves the nuclear polarization. The resulting hyperpolarized liquid sample can be transferred to a high-resolution NMR spectrometer, where an enhanced NMR signal can be acquired, or it may be used as an agent for in vivo imaging or spectroscopy. In this article we describe the use of the method on aqueous solutions of [13C]urea. Polarizations of 37% for 13C and 7.8% for 15N, respectively, were obtained after the dissolution. These polarizations correspond to an enhancement of 44,400 for 13C and 23,500 for 15N, respectively, compared with thermal equilibrium at 9.4 T and room temperature. The method can be used generally for signal enhancement and reduction of measurement time in liquid-state NMR and opens up for a variety of in vitro and in vivo applications of DNP-enhanced NMR.  相似文献   
77.
Heat shock protein 70 (Hsp70) is an antiapoptotic chaperone protein highly expressed in human tumors. Here we demonstrate that locoregional application of adenovirus expressing antisense Hsp70 cDNA (Ad.asHsp70) eradicates orthotopic xenografts of glioblastoma and breast carcinoma, as well as s.c. xenografts of colon carcinoma in immunodeficient mice. Ad.asHsp70-treated tumors showed massive apoptosis-like cell death and recruitment of macrophages. Human monocyte-derived macrophages effectively removed the corpses of Ad.asHsp70-treated tumor cells in vitro. Interestingly, both tumor cell death and phagocytosis were caspase-independent. Thus, Hsp70 appears as a promising target for the treatment of cancers resistant to classic caspase-mediated apoptosis.  相似文献   
78.
Paroxetine kinetics and cardiovascular effects were studied in 4 healthy male subjects after single oral doses of 45 mg and after slow intravenous infusion of 23-28 mg. The plasma concentration/time curves could be described by a two-compartment open model, but the estimates of the model parameters were relatively inaccurate after the oral test. Plasma half-lives were longer after oral (19.8 hrs. S.D. 1.3 hrs) than after intravenous test (12.3 hrs. S.D. 3.8 hrs). Different methods of calculation of the systemic availability resulted in different values, most probably due to dose dependent kinetics. This is possibly related to saturated elimination kinetics during the first pass metabolism. Systolic time interval measurements showed that paroxetine causes a shortening of the electromechanical systole (QS2 corrected for heart rate) indicating a positive inotropic effect of the compound. Paroxetine also caused a reduction in heart rate and a moderate rise in systolic and diastolic blood pressure. After the intravenous dose some subjects experienced nausea and one subject a quite pronounced anxiety.  相似文献   
79.
The kinetics of nortriptyline in four patients were investigated before and during treatment with perphenazine (24-36 mg/day) by administering 57 mg nortriptyline hydrochloride as an intravenous infusion and evaluating the resulting plasma concentration data according to a two compartment open model. In all patients an increased biological half-life as well as a decreased systemic clearance and rate of metabolism were found in the perphenazine-period, thus confirming the inhibitory effect of perphenazine on the metabolism of nortriptyline found in earlier studies. Some interaction with distribution parameters was also indicated, but on the whole the model parameters did not provide much further information about the interaction. Although the most pronounced changes were found with the patient getting the highest dose of perphenazine, the dose-effect relationship remains obscure.  相似文献   
80.
d-Propoxyphene kinetics was studied in 8 healthy male subjects after single oral doses of d-propoxyphene at 65, 130, and 190 mg and after slow intravenous infusion of 65 mg. Total urinary excretion (7 days) indicated complete oral absorption but systemic availability was reduced corresponding to fist-pass elimination of 30% to 70%. There was linearity between oral dose and the corresponding area under the plasma concentration/time curve of d-propoxyphene and the metabolite norpropoxyphene. The kinetic measurements showed 2- to 3-fold interindividual variations: oral clearance, 1.3 to 3.6 1/min; systemic clearance, 0.6 to 1.2 1/min; apparent volume of distribution, 700 to 1,800 1; d-propoxyphene half-life (t1/2), 8 to 24 hr; and norpropoxyphene t1/2, 18 to 29 hr. There were pronounced intraindividual dose-dependent variations in oral clearance in some subjects. The intravenous concentration curves indicated a 3-compartment distribution model.  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