全文获取类型
收费全文 | 2557篇 |
免费 | 167篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 19篇 |
儿科学 | 74篇 |
妇产科学 | 169篇 |
基础医学 | 292篇 |
口腔科学 | 69篇 |
临床医学 | 292篇 |
内科学 | 425篇 |
皮肤病学 | 99篇 |
神经病学 | 113篇 |
特种医学 | 129篇 |
外科学 | 220篇 |
综合类 | 49篇 |
一般理论 | 3篇 |
预防医学 | 269篇 |
眼科学 | 73篇 |
药学 | 206篇 |
中国医学 | 1篇 |
肿瘤学 | 234篇 |
出版年
2021年 | 31篇 |
2020年 | 20篇 |
2019年 | 35篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 26篇 |
2015年 | 26篇 |
2014年 | 53篇 |
2013年 | 71篇 |
2012年 | 93篇 |
2011年 | 119篇 |
2010年 | 59篇 |
2009年 | 69篇 |
2008年 | 78篇 |
2007年 | 112篇 |
2006年 | 104篇 |
2005年 | 98篇 |
2004年 | 106篇 |
2003年 | 95篇 |
2002年 | 69篇 |
2001年 | 47篇 |
2000年 | 41篇 |
1999年 | 57篇 |
1998年 | 52篇 |
1997年 | 48篇 |
1996年 | 54篇 |
1995年 | 46篇 |
1994年 | 44篇 |
1993年 | 33篇 |
1992年 | 36篇 |
1991年 | 53篇 |
1990年 | 41篇 |
1989年 | 61篇 |
1988年 | 47篇 |
1987年 | 60篇 |
1986年 | 42篇 |
1985年 | 40篇 |
1984年 | 35篇 |
1983年 | 32篇 |
1982年 | 32篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 34篇 |
1978年 | 27篇 |
1977年 | 26篇 |
1976年 | 37篇 |
1975年 | 32篇 |
1974年 | 29篇 |
1973年 | 21篇 |
1970年 | 21篇 |
排序方式: 共有2736条查询结果,搜索用时 15 毫秒
1.
2.
Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight. 相似文献
3.
4.
P.F. MORSE D.F. HORROBIN M.S. MANKU J.C.M. STEWART R. ALLEN S. LITTLEWOOD S. WRIGHT† J. BURTON† D.J. GOULD‡ P.J. HOLT§ C.T. JANSEN¶ L. MATTILA¶ W. MEIGEL TH. DETTKE D. WEXLER†† L. GUENTHER†† A. BORDONI‡‡ A. PATRIZI‡‡ 《The British journal of dermatology》1989,121(1):75-90
Gamma-linolenic acid in the form of a particular variety of evening primrose oil (Epogam) has been reported of value in the treatment of atopic eczema. Nine controlled trials of evening primrose oil were performed in eight centres. Four of the trials were parallel and five cross-over. Doctors and patients assessed the severity of eczema by scoring measures of inflammation, dryness, scaliness, pruritus and overall skin involvement. Individual symptom scores were combined to give a single global score at each assessment point. In the analysis of the parallel studies, both patient and doctor scores showed a highly significant improvement over baseline (P less than 0.0001) due to Epogam: for both scores the effect of Epogam was significantly better than placebo. Similar results were obtained on analysis of the cross-over trials, but in this case the difference between Epogam and placebo in the doctors' global score, although in favour of Epogam, failed to reach significance. The effects on itch were particularly striking. There was no placebo response to this symptom, whereas there was a substantial and highly significant response to Epogam (P less than 0.0001). When the improvements, or otherwise, in clinical condition were related to changes in plasma levels of dihomogammalinolenic and arachidoni acids, it was found that there was a positive correlation between an improvement in clinical score and a rise in the fatty acid levels. 相似文献
5.
André H. Eriksson Manthena V.S. Varma Everett J. Perkins Cheryl L. Zimmerman 《Journal of pharmaceutical sciences》2010,99(3):1574-1581
LY354740 is a potent mGlu2/3 agonist with a limited oral bioavailability. Its alanyl prodrug, LY544344, showed high affinity to the intestinal peptide transporter PEPT1, and improved the oral bioavailability of LY354740 in various animal models. The aim of the present study was to investigate the mechanism of in vivo absorption of the dipeptidic prodrug LY544344. The permeabilities of LY544344 and LY354740 were examined in the rat in situ single‐pass intestinal perfusion model. The intestinal absorptive flux of LY354740 was shown to be very low in comparison with LY544344. The absorptive flux of LY544344 could best be described by a Michaelis–Menten process in parallel with a linear process. The estimated parameters were: Jmax = 26.7 × 10?5 µmol/(cm2‐s), Km = 2.6 mM. The absorptive permeability of LY544344 was reduced to approximately 5% of control in the presence of excess Gly‐Sar, a known PEPT1 substrate. Intracellular accumulation of LY354740 and LY544344, estimated postperfusion, showed high levels of LY354740 over LY544344 at all perfusate concentrations studied. However, there was a decline in the intracellular ratio of LY354740 to LY544344 at higher concentrations, suggesting that the metabolic activation to release LY354740 is saturable. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1574–1581, 2010 相似文献
6.
Over a period of years the ventilation system of a community hospital progressively deteriorated until it no longer met regulatory guidelines. The hospital, a publicly funded military facility, requested funding to repair the ventilation system, but funds were not forthcoming because of budget austerity. When an increase in infections was documented, high-risk operations were curtailed and funding was expedited. With the new improved ventilation system the operating rooms once again met regulatory guidelines and infections returned to baseline rates. Throughout the period infections remained below recognized national levels. 相似文献
7.
Ittel TH; Steinhausen C; Kislinger G; Kinzel S; Nolte E; Sieberth HG 《Nephrology, dialysis, transplantation》1997,12(7):1369-1375
BACKGROUND: Developments in accelerator mass spectrometry (AMS) now permit
the determination of femtogram amounts of 26Al in blood and in various
tissues with good precision and free of external contamination. METHODS: In
the present study we used trace quantities of 26Al to investigate the
intestinal absorption and compartmentalization of aluminium in rats with
renal failure (Nx, 5/6 nephrectomy) and in pair- fed controls (C). Single
oral doses of 20 ng 26Al were administered to six animals in each group
and, subsequently, 24-h post-load 26Al was analysed in serum, urine, bone,
liver, and spleen by means of AMS. RESULTS: Serum concentrations of 26Al
were significantly lower in uraemic rats compared to controls, whereas
urinary excretion was comparable (Nx, 7.11 +/- 5.78 pg/day vs C, 9.46 +/-
6.10 pg/day), suggesting a higher fraction of ultrafiltrable serum 26Al in
uraemia. The target tissues of cellular transferrin-mediated 26Al uptake,
liver and spleen, tended to show a larger degree of aluminium accumulation
in controls (0.26 +/- 0.31 pg/g vs Nx, 0.14 +/- 0.10 pg/g and 0.37 +/- 0.27
pg/g vs Nx, 0.25 +/- 0.27 pg/g respectively). In contrast, in bone, a site
of extracellular aluminium deposition, 26Al concentrations were more
elevated in uraemia (1.22 +/- 0.59 pg/g vs C: 0.68 +/- 0.30 pg/g).
Estimated total 26Al accumulation in all measured target tissues was
significantly higher in uraemic rats (28.15 +/- 9.90 pg vs C: 17.03 +/-
7.03 pg) and total recovery of 26Al from tissue and urine was 26.58 +/-
6.74 pg in controls and 35.75 +/- 7.03 pg in uraemic animals, suggesting a
fractional absorption of 0.133% and 0.175% respectively. CONCLUSIONS: Our
data suggest that fractional absorption from a dietary level dose of 26Al
is about 0.13%. Compartmentalization occurs in transferrin-dependent target
tissues such as liver and spleen; however, in quantitative terms
extracellular deposition in bone is more important. Uraemia has a
significant effect on the intestinal absorption and compartmentalization of
aluminium. It enhances fractional absorption and increases subsequent
extracellular deposition of aluminium in bone. However, at the same time
uraemia does not increase transferrin-dependent cellular accumulation of
aluminium in liver and spleen.
相似文献
8.
9.
10.