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   1655篇
  免费   89篇
  国内免费   5篇
耳鼻咽喉   7篇
儿科学   6篇
妇产科学   78篇
基础医学   278篇
口腔科学   9篇
临床医学   142篇
内科学   309篇
皮肤病学   9篇
神经病学   173篇
特种医学   178篇
外科学   187篇
综合类   66篇
预防医学   87篇
眼科学   4篇
药学   116篇
中国医学   26篇
肿瘤学   74篇
  2023年   5篇
  2022年   9篇
  2021年   37篇
  2020年   10篇
  2019年   26篇
  2018年   32篇
  2017年   24篇
  2016年   34篇
  2015年   52篇
  2014年   65篇
  2013年   94篇
  2012年   124篇
  2011年   126篇
  2010年   69篇
  2009年   54篇
  2008年   97篇
  2007年   88篇
  2006年   106篇
  2005年   113篇
  2004年   103篇
  2003年   103篇
  2002年   91篇
  2001年   32篇
  2000年   22篇
  1999年   20篇
  1998年   19篇
  1997年   17篇
  1996年   15篇
  1995年   10篇
  1994年   4篇
  1993年   9篇
  1992年   11篇
  1991年   10篇
  1990年   10篇
  1989年   6篇
  1988年   5篇
  1987年   6篇
  1986年   4篇
  1985年   6篇
  1982年   5篇
  1981年   6篇
  1980年   5篇
  1979年   8篇
  1978年   6篇
  1977年   12篇
  1976年   4篇
  1974年   4篇
  1972年   6篇
  1971年   4篇
  1963年   3篇
排序方式: 共有1749条查询结果,搜索用时 15 毫秒
51.
Molecular Imaging and Biology - Radiotherapy is a frequently applied treatment modality for brain tumors. Concomitant irradiation of normal brain tissue can induce various physiological responses....  相似文献   
52.
The modified Allen's test (A.T.) is used to prove the adequacy of the blood supply through the ulnar artery to the hand. The test is considered normal if, after compression of both the ulnar and radial arteries followed by repeated clenching of the fingers to squeeze out the blood, the normal or a slightly more pronounced red color of the palm of the hands returns within < 10 sec after release of only the ulnar artery. It is important to perform the test whenever intravascular access to the radial artery is planned. The objective of this study was to determine the percentage of patients presenting a clearly positive (< 5 sec), a moderately positive (between 5–9 sec), or a negative A.T. (10 sec and more). We performed an A.T. on 1,000 consecutive and different patients undergoing cardiac catheterization, on the right wrist, two times, each time by a different examinator trained in this test. An A.T. was performed on 1,000 patients: 640 men, 360 women, mean age 62,3 yr (range 28–90 yr). In our population of patients, the relative percentages of a clearly positive (< 5 sec), moderately positive (between 5–9 sec), or negative modified Allen's test (10 sec and more) is 49%, 24%, and 27%, respectively. © 1996 Wiley-Liss, Inc.  相似文献   
53.
54.
55.
56.
A rapid, sensitive and automated assay procedure was developed for the in vitro evaluation of anti-HIV agents. An HTLV-I transformed T4-cell line, MT-4, which was previously shown by Koyanagi et al. (1985) to be highly susceptible to, and permissive for, HIV infection, served as the target cell line. Inhibition of the HIV-induced cytopathic effect was used as the end point. The viability of both HIV-and mock-infected cells was assessed spectrophotometrically via the in situ reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The procedure was optimized as to make optimal use of multichannel pipettes, microprocessor-controlled dispensing and optical density reading. The absorbance ratio of the mock-infected control to the HIV-infected samples was about 20. This allowed an accurate determination of the 50% effective doses, as demonstrated for 3'-azido-2',3'-dideoxythymidine (AZT), 2',3'-dideoxycytidine (ddCyd), dextran sulfate and heparin. The technique significantly reduced labor time as compared to the trypan blue exclusion method, and permits the evaluation of large numbers of compounds for their anti-HIV activity.  相似文献   
57.
In this prospective, randomized, open controlled study we compared the effects on net red blood cell loss of 6% hydroxyethyl starch 130/0.4 (HES: n = 64) and 3% modified fluid gelatin (GEL: n = 68) administered for intravascular volume management in patients undergoing coronary surgery. Blood losses were calculated from determination of circulating blood volume and measurement of preoperative and postoperative hematocrit. Amount of colloids that could be administered was limited to 50 mL/kg. If additional fluids were required, balanced crystalloid solution was used. Anesthetic and surgical techniques were standardized. Both groups were similar with regard to demographic and intraoperative variables. Total study drug was 48.9 +/- 17.2 mL/kg in the HES group and 48.9 +/- 14.6 mL/kg in the GEL group. Total red blood cell loss was 544 +/- 305 mL in the HES group and 504 +/- 327 mL the GEL group. Measured blood losses were also similar in both groups (HES, 19.4 +/- 12.3 mL/kg; GEL, 19.2 +/- 14.5 mL/kg). Exposure to allogeneic blood product was comparable in both groups. In the conditions of the present study, HES 130/0.4 up to 50 mL/kg is a valuable alternative to modified fluid gelatin for plasma volume expansion during and after cardiac surgery.  相似文献   
58.

Background and objectives

Kidney disease progression, assessed by change in eGFR on the basis of creatinine, is an independent risk factor for cardiovascular disease and death. This study aimed to evaluate whether changes in multiple filtration markers, individually and combined, were associated with cardiovascular disease and death.

Design, setting, participants, & measurements

Creatinine, cystatin C, and β2-microglobulin were measured among 9716 Atherosclerosis Risk in Communities Study participants in 1990–1992 and 1996–1998. Percentage change in three filtration markers (eGFR on the basis of creatinine, eGFR on the basis of cystatin C, and 1/β2-microglobulin) individually and the average of percentage change across all three filtration markers were calculated. Cardiovascular events and deaths were ascertained from 1996 to 2011. Cox regression models were adjusted for established risk factors for cardiovascular disease and mortality and first measurement of eGFR on the basis of creatinine.

Results

During a median follow-up of 14 years, there were 1922 cardiovascular events and 2285 deaths from any cause. Decline of >30% in each filtration marker was significantly associated with higher risk of mortality compared with stable kidney function (−9.9% to +9.9% change in the filtration marker) with hazard ratios (95% confidence intervals) of 1.91 (1.67 to 2.18) for eGFR on the basis of creatinine, 2.29 (1.99 to 2.63) for eGFR on the basis of cystatin C, and 2.48 (2.15 to 2.86) for 1/β2-microglobulin, with similar associations for cardiovascular disease. An average decline of >30% across the three markers was strongly associated with higher risk of all-cause mortality (hazard ratio, 2.82; 95% confidence interval, 2.42 to 3.29).

Conclusions

Kidney disease progression was assessed using >30% decline in eGFR on the basis of creatinine, eGFR on the basis of cystatin C, and 1/β2-microglobulin and average decline of >30% across the three filtration markers is strongly associated with risk of cardiovascular disease and death.  相似文献   
59.
Our goal was to determine whether genetic variation at genes affecting statin metabolism or targets of statin therapy would influence low density lipoprotein (LDL) cholesterol lowering with pravastatin, baseline heart disease, or cardiac endpoints on trial. We examined associations of single nucleotide polymorphisms (SNPs) at the liver X receptor alpha (LXRA, rs12221497), and the solute carrier organic anion transporter (SLCO1B1, rs4149056 and rs2306283) gene loci with these variables. We studied 5411 participants in PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) (mean age 75.3 years), who had been randomized to pravastatin 40 mg/day or placebo and were followed for a mean of 3.2 years. No relationships between genetic variation at the LXRA gene locus with statin induced LDL lowering response or other parameters were noted. Both the SLCO1B1 rs4149056 (valine for alanine at 174) and the rs2306283 (asparagine for aspartic acid at 130) SNPs affect the amino acid sequence of the SLCO1B1 gene product. No effect of the rs2306283 SNP on any of the variables was noted. However the presence of the rs4149056 SNP was associated with significantly less LDL cholesterol lowering response to pravastatin (wildtype, 71.5% of the population, -37.0%; heterozygotes, 25.8% of the population, -36.0%; and homozygotes, 2.7% of the population, -31.8%, p=0.003 at 6 months, and p=0.022 at 12 months). Our data indicate that the presence of the rs4149056 non-synonymous SNP at the SLCO1B1 gene locus can significantly decrease the pravastatin induced LDL cholesterol lowering response.  相似文献   
60.
Seventy-five retired baseball players participated in a survey (37.8% response rate) in order to establish the long-term consequences of injuries sustained during their playing careers. Respondents had a mean age of 55.8 (+/-11.4) years with a mean age of 41.3 (+/-11.4) years at retirement from play. The mean overall rate of injury suffered per player/playing career was 5.6 (+/-7.1). 54.7% of respondents experienced a major injury (i.e. injury resulting in 5 or more consecutive weeks absence from training and play) with a mean major injury per player/playing career of 1.5 (+/-2.2). The rate for significant injuries (i.e. injury resulting in more than 1 week but less than 5 weeks absence from training and play) was 4.1 (+/-6.5) per player/playing career. Catchers had significantly less injuries than all other positions (p=0.027). 18.7% of all respondents reported suffering from arthritis, 24% from restricted joint mobility and 4% from chronically stiff fingers; all of these conditions were associated with their participation in baseball based on medical examination by their GP or medical specialist. 29.3% of respondents indicated that they had incurred additional medical costs and 12% reported significant loss of income associated with their injuries. Some injuries were severe enough that they resulted in extended stays in hospital producing costs carried by the health care system.  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