全文获取类型
收费全文 | 14037篇 |
免费 | 1247篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 536篇 |
妇产科学 | 275篇 |
基础医学 | 1726篇 |
口腔科学 | 274篇 |
临床医学 | 1560篇 |
内科学 | 2734篇 |
皮肤病学 | 163篇 |
神经病学 | 1335篇 |
特种医学 | 682篇 |
外科学 | 1962篇 |
综合类 | 347篇 |
一般理论 | 18篇 |
预防医学 | 1347篇 |
眼科学 | 366篇 |
药学 | 1049篇 |
中国医学 | 10篇 |
肿瘤学 | 814篇 |
出版年
2022年 | 133篇 |
2021年 | 237篇 |
2020年 | 145篇 |
2019年 | 246篇 |
2018年 | 302篇 |
2017年 | 222篇 |
2016年 | 244篇 |
2015年 | 293篇 |
2014年 | 375篇 |
2013年 | 527篇 |
2012年 | 797篇 |
2011年 | 794篇 |
2010年 | 450篇 |
2009年 | 378篇 |
2008年 | 698篇 |
2007年 | 708篇 |
2006年 | 705篇 |
2005年 | 663篇 |
2004年 | 690篇 |
2003年 | 572篇 |
2002年 | 589篇 |
2001年 | 360篇 |
2000年 | 343篇 |
1999年 | 315篇 |
1998年 | 195篇 |
1997年 | 180篇 |
1996年 | 180篇 |
1995年 | 131篇 |
1994年 | 137篇 |
1993年 | 150篇 |
1992年 | 287篇 |
1991年 | 253篇 |
1990年 | 209篇 |
1989年 | 210篇 |
1988年 | 211篇 |
1987年 | 202篇 |
1986年 | 194篇 |
1985年 | 167篇 |
1984年 | 124篇 |
1983年 | 102篇 |
1982年 | 85篇 |
1981年 | 93篇 |
1980年 | 98篇 |
1979年 | 90篇 |
1978年 | 89篇 |
1977年 | 85篇 |
1976年 | 91篇 |
1974年 | 76篇 |
1973年 | 94篇 |
1972年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Evaluation of renal transplant dysfunction by duplex Doppler sonography: a prospective study and review of the literature 总被引:5,自引:0,他引:5
R R Perrella A J Duerinckx F N Tessler G M Danovitch A Wilkinson S Gonzalez A H Cohen E G Grant 《American journal of kidney diseases》1990,15(6):544-550
A disconcertingly wide variation exists in the literature as to the accuracy of duplex Doppler sonography in the detection of acute renal transplant rejection. Sensitivities range from 9% to 76%. In an attempt to explain the disparity of results, we undertook a double-blind prospective study of the accuracy of duplex Doppler ultrasound in the detection of acute rejection in renal transplants. We scanned 49 consecutive patients with a total of 65 biopsies; 46 biopsies in 33 consecutive patients were included in our study. In our population, the prevalence of acute rejection was 61% (28/46). Using a resistive index (RI) cutoff of greater than 0.90 based on the main renal artery flow pattern, the sensitivity of our test was 43%, with a 67% specificity. The positive predictive value was 67%. Our results are contrasted and compared with the published data from other groups in a critical survey of the literature. We conclude that duplex Doppler sonography alone is inadequate to evaluate acute rejection in renal transplants. 相似文献
22.
23.
24.
Effect of the beta-adrenoceptor agonist clenbuterol and phytohaemagglutinin on growth, protein synthesis and polyamine metabolism of tissues of the rat. 下载免费PDF全文
S. Bardocz D. S. Brown G. Grant A. Pusztai J. C. Stewart R. M. Palmer 《British journal of pharmacology》1992,106(2):476-482
1. The kidney bean lectin, phytohaemagglutinin (PHA), induced a marked atrophy of skeletal muscle which was evident from the changes in tissue composition (protein, RNA, DNA and polyamine content) and from the reduction in weight and protein synthesis of hind leg muscles of rats fed on kidney bean-diets for four days. The beta-adrenoceptor agonist, clenbuterol, induced skeletal muscle hypertrophy by transiently stimulating protein synthesis. As a consequence, the muscle loss caused by a short exposure to PHA was, in part, ameliorated by clenbuterol treatment. 2. Cardiac muscle was affected to a lesser extent than skeletal muscle by both clenbuterol and the lectin. However, there was evidence that protein synthesis in heart was reduced by PHA. 3. PHA had opposite effects on the gut, the lectin-induced hyperplasia of the jejunum was accompanied by a large increase in protein synthesis. Clenbuterol alone had no effect on the jejunum whereas a combination of PHA and clenbuterol appeared to exacerbate the effect of the lectin on gut. 4. Both the lectin-induced gut growth and the hypertrophy of skeletal muscle caused by clenbuterol were preceded by the accumulation of polyamines in the respective tissues. Of particular note was the observation that a significant increase in the proportion of the intraperitoneally injected 14C-labelled spermidine or putrescine taken up by the growing tissues could be detected by the second day. Therefore, the measurement of uptake of labelled polyamines may be used as a sensitive indicator of early alterations in tissue metabolism. 相似文献
25.
26.
R. Grant Steen Suzanne A. Gronemeyer Peter B. Kingsley Wilbum E. Reddick James S. Langston June S. Taylor 《Journal of magnetic resonance imaging : JMRI》1994,4(5):681-691
Precise and accurate inversion-recovery (PAIR) magnetic resonance (MR) measurements of T1 were obtained in eight brain regions and cerebrospinal fluid of 26 healthy volunteers. Accuracy of the technique was assessed by measuring T1 in small fluid volumes with the PAIR technique and with two independent spectroscopic techniques. The mean difference between T1 measured with PAIR and with the two spectroscopic techniques was 3.1% ± 1.3. The precision (reproducibility) of measurements with the PAIR technique was excellent. The coefficient of variation (CV) across 16 measurements in a head phantom was 2.0%, compared with a CV of 2.7% across 45 separate measurements in a single subject. The within-subject CV was 1.8% ± 0.6 in white matter and 1.4% ± 1.0 in basal ganglia. The between-subject CV in 26 healthy volunteers was 3.6% ± 0.6 in white matter and 4.1% ± 1.9 in basal ganglia. Comparison between a patient with an active recurrent brain tumor and an agematched patient with an inactive brain tumor showed that T1 was significantly elevated throughout the brain of the active-tumor patient, especially in white matter tracts, even though no tumor or edema was detected in the white matter on standard MR images. Comparisons between five brain tumor patients and four healthy volunteers of similar age showed that T1 was significantly and substantially elevated throughout the white matter tracts and in the caudate nucleus, putamen, and thalamus. These results are consistent with the hypothesis that white matter tracts are selectively vulnerable to edema and that T1 increases in white matter are a sensitive indicator of patient status or tumor aggressiveness. 相似文献
27.
28.
M. Grant B. Ferrell G. M. Schmidt P. Fonbuena J. C. Niland S. J. Forman 《Quality of life research》1992,1(6):375-384
This study was designed to assess the reliability and validity of a Quality of Life (QOL) instrument on a sample of 179 allogeneic Bone Marrow Transplant (BMT) survivors. The QOL-BMT tool was developed specifically for this population and was based on the investigators' prior research and a conceptual model of Quality of Life. Patients who were at least 100 days post BMT completed the 30 item visual analogue questionnaire. The instrument measured physical symptoms (e.g., weight loss, frequent colds, skin changes, cataracts, sexual problems), psychological to illness, social concerns (e.g., relationship adjustment, return to work), and spiritual well-being (e.g., sense of control, future goals). Psychometric analysis of the instrument included measures of reliability and validity. The study findings demonstrate the unique aspects of QOL dimensions in BMT survivors and the value of QOL assessment in clinical practice and research.This study was supported by the City of Hope National Medical Center, NCI Cancer Center Core Grant, R30 CA 33572 and the City of Hope BRSG Grant Support. 相似文献
29.
Given current clinical use of phospholipid bilayer structures (liposomes/vesicles) as nontoxic drug delivery vehicles, we have addressed the possibility of employing the phospholipids themselves as MRI contrast agents. To this end we have synthesized phosphatidylcholine with a nitroxide spin label replacing one methyl residue of the choline headgroup. This material was mixed with natural phosphatidylcholine in mole ratios from 1:50 to 1:1 and used to prepare sonicated unilamellar vesicles in saline. Expected structural features of these vesicles were verified by freeze-fracture electron microscopy. Proton T1 values of saline were readily decreased to less than 0.3 s by such preparations, yielding a net relaxivity of 0.6 M-1 s-1. The approach seems to be a realistic way of firmly associating a contrast agent of minimal toxicity with ordinary liposomes/vesicles in a manner that is not subject to leakage. 相似文献
30.
K Grant S R Huntington 《Physician assistant (American Academy of Physician Assistants)》1989,13(7):76-86
The traditional, informal approach to making medical decisions for incapacitated patients is often inappropriate today. Guidelines are needed in two major areas: assessing incapacity and seeking surrogate decision makers. Judicially declared incompetency does not necessarily imply incapacity to make medical choices. Proposed standards for determining incapacity require a multistep evaluation of the patient's abilities to understand, reason, and communicate. When decisions must be made for an incapacitated patient, priority is given to the patient's previously stated preferences. An advance directive--living will or durable power of attorney--simplifies the process. If no advance directive was prepared, a surrogate decision maker may be designated according to applicable state statutes. Standards are still evolving for protecting the autonomy and best interests of vulnerable, incapacitated patients. 相似文献