全文获取类型
收费全文 | 1338篇 |
免费 | 82篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 110篇 |
妇产科学 | 56篇 |
基础医学 | 127篇 |
口腔科学 | 40篇 |
临床医学 | 151篇 |
内科学 | 263篇 |
皮肤病学 | 19篇 |
神经病学 | 31篇 |
特种医学 | 327篇 |
外科学 | 118篇 |
综合类 | 13篇 |
一般理论 | 1篇 |
预防医学 | 55篇 |
眼科学 | 10篇 |
药学 | 31篇 |
肿瘤学 | 75篇 |
出版年
2023年 | 4篇 |
2021年 | 17篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 26篇 |
2017年 | 12篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 27篇 |
2013年 | 30篇 |
2012年 | 24篇 |
2011年 | 25篇 |
2010年 | 33篇 |
2009年 | 28篇 |
2008年 | 21篇 |
2007年 | 32篇 |
2006年 | 26篇 |
2005年 | 30篇 |
2004年 | 33篇 |
2003年 | 20篇 |
2002年 | 18篇 |
2001年 | 14篇 |
2000年 | 15篇 |
1999年 | 25篇 |
1998年 | 95篇 |
1997年 | 69篇 |
1996年 | 77篇 |
1995年 | 53篇 |
1994年 | 55篇 |
1993年 | 62篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 21篇 |
1989年 | 47篇 |
1988年 | 28篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 34篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 27篇 |
1980年 | 34篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 22篇 |
1975年 | 14篇 |
1930年 | 3篇 |
1926年 | 3篇 |
排序方式: 共有1431条查询结果,搜索用时 15 毫秒
1.
D P Derman D Ballot T H Bothwell B J MacFarlane R D Baynes A P MacPhail M Gillooly J E Bothwell W R Bezwoda F Mayet 《The British journal of nutrition》1987,57(3):345-353
The absorption of iron from soya-bean (Glycine hispida)-based and milk-based infant formulas was assessed in 138 multiparous Indian women, using the erythrocyte utilization of radioactive Fe method. Fe absorption was significantly greater from the basal milk formula (1.5 g protein) than it was from the basal soya-bean formula (2.3 g protein), with geometric mean values of 0.083 and 0.044 respectively. Ascorbic acid markedly increased Fe absorption from the milk-based formula in a dose-dependent fashion. The increase was fivefold when the ascorbic acid:Fe ratio on a weight-for-weight basis was 6:1 and over tenfold when it was 20:1. In contrast, ascorbic acid had a less-marked effect on the absorption of Fe from the soya-bean-based formula, with only a two- to threefold increase at an ascorbic acid:Fe ratio of 20:1. The geometric mean Fe absorption from the soya-bean formula (1.27 mg Fe, 2.3 g isolated soya-bean protein (ISP] was somewhat less than that from the same amounts of ISP and ascorbic acid made up in milk (0.075 and 0.113 respectively). However, a direct comparison between the soya-bean formula in milk and in water showed no significant difference (0.043 and 0.060 respectively). Fe absorption from a drink containing 10 g ISP and 30 mg ascorbic acid was significantly better than that from a similar drink containing the soya-bean flour from which ISP is extracted (0.044 and 0.027 respectively). Heating ISP to 200 degrees for 2 h before its use had no effect on Fe availability.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
2.
3.
4.
5.
6.
Competitive control of the self-renewing T cell repertoire 总被引:1,自引:0,他引:1
We develop a mathematical model for the self-renewing part of the T cell
repertoire. Assuming that self-renewing T cells have to be stimulated by
immunogenic MHC-peptide complexes presented on the surfaces of
antigen-presenting cells, we derive a model of T cell growth in which
competition for MHC-peptide complexes limits T cell clone sizes and
regulates the total number of self-renewing T cells in the animal. We show
that for a sufficient diversity and/or degree of cross-reactivity, the
total T cell number hardly depends upon the diversity of the T cell
repertoire or the diversity of the set of presented peptides. Conversely,
for repertoires of lower diversity and/or cross-reactivity, steady-state
total T cell numbers may be limited by the diversity of the T cells. This
provides a possible explanation for the limited repertoire expansion in
some, but not all, mouse T cell re-constitution experiments. We suggest
that the competitive interactions described by our model underlie the
normal T cells numbers observed in transgenic mice, germ-free mice and
various knockout mice.
相似文献
7.
Localization of a gene for otosclerosis to chromosome 15q25-q26 总被引:5,自引:0,他引:5
Tomek MS; Brown MR; Mani SR; Ramesh A; Srisailapathy CR; Coucke P; Zbar RI; Bell AM; McGuirt WT; Fukushima K; Willems PJ; Van Camp G; Smith RJ 《Human molecular genetics》1998,7(2):285-290
Among white adults otosclerosis is the single most common cause of hearing
impairment. Although the genetics of this disease are controversial, the
majority of studies indicate autosomal dominant inheritance with reduced
penetrance. We studied a large multi- generational family in which
otosclerosis has been inherited in an autosomal dominant pattern. Five of16
affected persons have surgically confirmed otosclerosis; the remaining nine
have a conductive hearing loss but have not undergone corrective surgery.
To locate the disease- causing gene we completed genetic linkage analysis
using short tandem repeat polymorphisms (STRPs) distributed over the entire
genome. Multipoint linkage analysis showed that only one genomic region, on
chromosome 15q, generated a lod score >2.0. Additional STRPs were typed
in this area, resulting in a lod score of 3.4. STRPs FES (centromeric) and
D15S657 (telomeric) flank the 14. 5 cM region that contains an otosclerosis
gene.
相似文献
8.
IMPT1, an imprinted gene similar to polyspecific transporter and multi- drug resistance genes 总被引:5,自引:1,他引:5
Dao D; Frank D; Qian N; O'Keefe D; Vosatka RJ; Walsh CP; Tycko B 《Human molecular genetics》1998,7(4):597-608
Human chromosome 11p15.5 and distal mouse chromosome 7 include a
megabase-scale chromosomal domain with multiple genes subject to parental
imprinting. Here we describe mouse and human versions of a novel imprinted
gene, IMPT1 , which lies between IPL and p57 KIP2 and which encodes a
predicted multi-membrane-spanning protein similar to bacterial and
eukaryotic polyspecific metabolite transporter and multi- drug resistance
pumps. Mouse Impt1 and human IMPT1 mRNAs are highly expressed in tissues
with metabolite transport functions, including liver, kidney, intestine,
extra-embryonic membranes and placenta, and there is strongly preferential
expression of the maternal allele in various mouse tissues at fetal stages.
In post-natal tissues there is persistent expression, but the allelic bias
attenuates. An allelic expression bias is also observed in human fetal and
post-natal tissues, but there is significant interindividual variation and
rare somatic allele switching. The fact that Impt1 is relatively repressed
on the paternal allele, together with data from other imprinted genes,
allows a statistical conclusion that the primary effect of human chromosome
11p15.5/mouse distal chromosome 7 imprinting is domain-wide relative
repression of genes on the paternal homolog. Dosage regulation of the
metabolite transporter gene(s) by imprinting might regulate placental and
fetal growth.
相似文献
9.
Kevin D. Derman John A. Hawley Timothy D. Noakes Steven C. Dennis 《European journal of applied physiology》1996,74(1-2):36-43
On two occasions, six well-trained, male competitive triathletes performed, in random order, two experimental trials consisting of either a timed ride to exhaustion on a cycle ergometer or a run to exhaustion on a motor-driven treadmill at 80% of their respective peak cycling and peak running oxygen (VO2max) uptakes. At the start of exercise, subjects drank 250 ml of a 15 g·100 ml–1 w/v [U-14C]glucose solution and, thereafter, 150 ml of the same solution every 15 min. Despite identical metabolic rates [VO2 3.51 (0.06) vs 3.51 (0.10) 1·min–1; values are mean (SEM) for the cycling and running trials, respectively], exercise times to exhaustion were significantly longer during cycling than running [96 (14) vs 63 (11) min; P < 0.05]. The superior cycling than running endurance was not associated with any differences in either the rate of blood glucose oxidation [3.8 (0.1) vs 3.9 (0.4) mmol· min–1], or the rate of ingested glucose oxidation [2.0 (0.1) vs 1.7 (0.2) mmol· min–1] at the last common time point (40 min) before exhaustion, despite higher blood glucose concentrations at exhaustion during running than cycling [7.0 (0.9) vs 5.8 (0.5) mmol·1–1; P < 0.05]. However, the final rate of total carbohydrate (CHO) oxidation was significantly greater during cycling than running [24.0 (0.8) vs 21.7 (1.4) mmol C6·min–1; P < 0.01]. At exhaustion, the estimated contribution to energy production from muscle glycogen had declined to similar extents in both cycling and running [68 (3) vs 65 (5)%]. These differences between the rates of total CHO oxidation and blood glucose oxidation suggest that the direct and/or indirect (via lactate) oxidation of muscle glycogen was greater in cycling than running. 相似文献
10.
Role of nitric oxide in the biology, physiology and pathophysiology of reproduction 总被引:13,自引:0,他引:13
Following its benchmark discovery, nitric oxide (NO) is nowknown to play important functional roles in a variety of physiologicalsystems. Within the vasculature, NO induces vasodilation, inhibitsplatelet aggregation, prevents neutrophil/platelet adhesionto endothelial cells, inhibits smooth muscle cell proliferationand migration, regulates programmed cell death (apoptosis) andmaintains endothelial cell barrier function. NO generated byneurons acts as a neurotransmitter, whereas NO generated bymacrophages in response to invading microbes acts as an antimicrobialagent. Because neurons, blood vessels and cells of the immunesystem are integral parts of the reproductive organs, and inview of the important functional role that NO plays in thosesystems, it is likely that NO is an important regulator of thebiology and physiology of the reproductive system. Indeed, inthe past 10 years, NO has established itself as a polyvalentmolecule which plays a decisive role in regulating multiplefunctions within the female as well as the male reproductivesystem. This review provides an overview of the role of NO invarious reproductive organs under physiological and pathologicalconditions. 相似文献