全文获取类型
收费全文 | 4965篇 |
免费 | 312篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 66篇 |
儿科学 | 152篇 |
妇产科学 | 135篇 |
基础医学 | 767篇 |
口腔科学 | 77篇 |
临床医学 | 492篇 |
内科学 | 715篇 |
皮肤病学 | 183篇 |
神经病学 | 515篇 |
特种医学 | 199篇 |
外科学 | 638篇 |
综合类 | 59篇 |
预防医学 | 519篇 |
眼科学 | 168篇 |
药学 | 348篇 |
中国医学 | 1篇 |
肿瘤学 | 273篇 |
出版年
2022年 | 43篇 |
2021年 | 56篇 |
2020年 | 42篇 |
2019年 | 65篇 |
2018年 | 83篇 |
2017年 | 69篇 |
2016年 | 77篇 |
2015年 | 97篇 |
2014年 | 116篇 |
2013年 | 161篇 |
2012年 | 204篇 |
2011年 | 224篇 |
2010年 | 164篇 |
2009年 | 150篇 |
2008年 | 207篇 |
2007年 | 220篇 |
2006年 | 202篇 |
2005年 | 230篇 |
2004年 | 194篇 |
2003年 | 151篇 |
2002年 | 155篇 |
2001年 | 187篇 |
2000年 | 142篇 |
1999年 | 121篇 |
1998年 | 95篇 |
1997年 | 60篇 |
1996年 | 52篇 |
1995年 | 43篇 |
1994年 | 44篇 |
1993年 | 37篇 |
1992年 | 105篇 |
1991年 | 109篇 |
1990年 | 107篇 |
1989年 | 94篇 |
1988年 | 99篇 |
1987年 | 83篇 |
1986年 | 87篇 |
1985年 | 82篇 |
1984年 | 68篇 |
1983年 | 52篇 |
1982年 | 36篇 |
1980年 | 43篇 |
1979年 | 59篇 |
1978年 | 42篇 |
1977年 | 36篇 |
1975年 | 39篇 |
1974年 | 46篇 |
1973年 | 35篇 |
1972年 | 39篇 |
1971年 | 43篇 |
排序方式: 共有5307条查询结果,搜索用时 0 毫秒
21.
Learning and memory: regional changes in N-methyl-D-aspartate receptors in the chick brain after imprinting. 总被引:3,自引:2,他引:1 下载免费PDF全文
B J McCabe G Horn 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(8):2849-2853
An extensive series of experiments has implicated a restricted region of the chick forebrain in the learning process of imprinting. The region is the intermediate and medial part of the hyperstriatum ventrale (IMHV). Previous studies have shown that training is associated with an increase in the area of the postsynaptic density of axospinous synapses in the left but not the right IMHV. The postsynaptic density is a site of high receptor density, and at least some axospinous synapses are excitatory. We found that imprinting is associated with a 59% increase in N-methyl-D-aspartate-sensitive binding of the excitatory amino acid L-[3H]glutamic acid in the left IMHV. The increase is probably due to an increased number of binding sites. The profile of sensitivity of the sites to a series of amino-, phosphono-substituted carboxylic acids (2-amino-3-phosphonopropionate to 2-amino-8-phosphonooctanoate) is characteristic of N-methyl-D-aspartate-type receptors. There were no significant effects of training on binding in the right IMHV. The effect of training on left IMHV binding could not be attributed to light exposure, arousal, or motor activity per se but was a function of how much the chicks learned. The changes in the left IMHV could increase the effectiveness of synaptic transmission in a region crucial for information storage and so form a neural basis for recognition memory. 相似文献
22.
Auke J. S. Renard Ren P. H. Veth Maciej Pruszczynksi Jaap Hoogenhout Jos Bkkerink Frans J. M. Van Der Staak Theo Wobbes Josef A. M. Lemmens Ren van Hoesel Jim R. Van Horn 《Journal of surgical oncology》1995,60(4):250-256
This paper describes 29 patients with Ewing's sarcoma of bone treated between 1975 and 1990 at the University of Nijmegen Hospital, Nijmegen, The Netherlands. Osteomyelitis was the primary diagnosis in 24%. Treatment consisted of chemotherapy in combination with surgery and/or radiotherapy. Nine patients received radiotherapy only; five of them died of disease. Five patients underwent an intralesional excision; four of them died of disease. Twelve patients underwent a wide excision; there is no evidence of disease in any of them. Three patients underwent a radical disarticulation; all died of disease. The disease-free survival at 1.5 years was 66%. This figure at 5 years was 55%. After wide excision and reconstruction in tumors of expendable, femoral or radial bones good functional results were obtained in all cases. © 1995 Wiley-Liss, Inc. 相似文献
23.
A myelodysplastic syndrome (MDS), type 5 (RAEB-t), and systemic mastocytosis affecting the spleen, the splenic lymph nodes, the bone marrow and the liver were diagnosed in a 38-year-old woman. The clinical course was complicated by splenic vein thromboses and iliac artery embolism. The thrombotic episodes might be secondary to mast cell mediator release. A complete remission of the MDS was obtained by allogeneic bone marrow transplantation, but the mastocytosis persisted. Thus, the possibility that the mast cell originates from a common myeloid precursor cell may be questioned. 相似文献
24.
Argon laser stapedectomy using an endo-otoprobe system 总被引:3,自引:0,他引:3
In summary, we believe that the endo-otoprobe system offers several advantages to the otologist. The system is safe and relatively inexpensive. The probes are designed to provide tactile feedback similar to that of standard otologic instruments and avoid the use of a cumbersome micromanipulator. There are currently shapes that are similar to a Rosen needle, Shea pick, and bayonet. We hope most otologists will find that one of the endo-otoprobes fits their particular style of surgery. 相似文献
25.
Nordihydroguaiaretic acid inhibits voltage-activated Ca2+ currents independently of lipoxygenase inhibition 总被引:7,自引:0,他引:7
The effects of nordihydroguaiaretic acid (NDGA), a widely used lipoxygenase inhibitor, were examined on voltage-activated Ca2+ channel currents in GH3 and AtT-20 pituitary cells. NDGA (10-100 microM) produced a reversible, dose-dependent inhibition of Ca2+ channel currents, with half-maximal inhibition occurring at 18.6 microM. Inhibition by NDGA developed relatively slowly, did not exhibit use dependence or voltage dependence, and did not require access of NDGA to the extracellular domain of the Ca2+ channel. The maximum inhibition of macroscopic currents by 30 microM NDGA was equivalent in the presence of 5 and 50 mM extracellular Ca2+ and 5 mM Ba2+. NDGA inhibited Ca2+ channel currents in excised, outside-out patches, in the absence of intra- and extracellular Ca2+ (with Ba2+ as the charge carrier), and following preincubation of the cells with the phospholipase A2 inhibitor 4-bromophenacylbromide. Of five other lipoxygenase inhibitors tested, only one inhibited Ca2+ currents. These results suggest that NDGA inhibits Ca2+ channel currents by a mechanism distinct from that of other known Ca2+ channel antagonists and that, when influx of Ca2+ through voltage-gated channels is involved, inhibition of Ca2(+)-dependent cell functions by NDGA (greater than 10 microM) may be independent of effects on arachidonic acid metabolism. 相似文献
26.
27.
Modulation of cyclic nucleotide levels in peripheral nerve without effect on resting or compound action potentials. 下载免费PDF全文
1. Cyclic nucleotide levels and compound action potential magnitudes were measured in frog sciatic nerves following exposure to carbachol, isoprenaline and cyclic nucleotide related substances. 2. The resting cyclic AMP level was 2-4 p-mole/mg protein and the cyclic GMP level was 0-27 p-mole/mg protein in desheathed nerves. 3. Isoprenaline (100 micrometer) caused a twofold increase in cyclic AMP without affecting cyclic GMP levels. Carbachol (100 micrometer) caused a twofold increase in cyclic GMP without affecting cyclic AMP levels. 4. The phosphodiesterase inhibitor theophylline (5 mM) augmented both cyclic AMP and cyclic GMP. 5. The magnitude of the resting or compound action potential was not affected by isoprenaline, carbachol, or phosphodiesterase inhibitors. 6. The cyclic nucleotides and their butyryl derivatives did not affect the magnitude of the resting or compound action potential, either when applied alone or in the presence of a phosphodiesterase inhibitor. 7. In contrast to sympatic tissue we conclude that hormone mediated cyclic nucleotide metabolism in peripheral nerve is unrelated to control of axonal excitability. 相似文献
28.
Menkes X linked disease: heterozygous phenotype in uncloned fibroblast cultures. 总被引:1,自引:1,他引:1 下载免费PDF全文
N Horn 《Journal of medical genetics》1980,17(4):257-261
The 64Cu incorporation into uncloned fibroblast cultures from 16 Menkes disease mothers and 19 first and second degree female relatives was examined. The mean incorporation for the Menkes disease mothers (36.2 +/- 3.6 SEM) differed significantly from that of 25 normal subjects (21.7 +/- 0.9 SEM) suggesting the presence of a significant proportion of mutant cells. In addition, the results suggested a heterozygous state in a number of the female relatives. Uncloned fibroblast cultures from four Menkes disease heterozygotes showed increasingly abnormal copper uptake values after repeated freezing procedures. Manipulation of tissue cultures may help to identify a number of female carriers. 相似文献
29.
Mark S. Sothmann Thelma S. Horn Barbara A. Hart Anthony B. Gustafson 《Psychophysiology》1987,24(1):47-54
Discrete cardiovascular fitness groups consisting of high-fit (n=10) and low-fit (n=9) men performed a well-learned vigilance task and their self-report, performance, and plasma catecholamine responses were compared. No significant differences were observed between the fitness groups on self-report or psychomotor performance responses to the vigilance task. However, the low-fit group took significantly longer than high-fit subjects to complete the first of three sets of anagrams administered immediately after the vigilance task. Plasma norepinephrine but not epinephrine response was greater in the low-fit group compared to their high-fit counterparts. The findings indicate that enhanced cardiovascular fitness may be characterized by an attenuated plasma norepinephrine response to a vigilance task with sustained cognitive performance subsequent to the task. 相似文献
30.
Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability 总被引:1,自引:15,他引:1
La Spada AR; Peterson KR; Meadows SA; McClain ME; Jeng G; Chmelar RS; Haugen HA; Chen K; Singer MJ; Moore D; Trask BJ; Fischbeck KH; Clegg CH; McKnight GS 《Human molecular genetics》1998,7(6):959-967
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG
repeat expansion in the first exon of the androgen receptor (AR) gene.
Disease-associated alleles (37-66 CAGs) change in length when transmitted
from parents to offspring, with a significantly greater tendency to shift
size when inherited paternally. As transgenic mice carrying human AR cDNAs
with 45 and 66 CAG repeats do not display repeat instability, we attempted
to model trinucleotide repeat instability by generating transgenic mice
with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions
in their genomic context. Studies of independent lines of AR YAC transgenic
mice with CAG 45 alleles reveal intergenerational instability at an overall
rate of approximately 10%. We also find that the 45 CAG repeat tracts are
significantly more unstable with maternal transmission and as the
transmitting mother ages. Of all the CAG/CTG repeat transgenic mice
produced to date the AR YAC CAG 45 mice are unstable with the smallest
trinucleotide repeat mutations, suggesting that the length threshold for
repeat instability in the mouse may be lowered by including the appropriate
flanking human DNA sequences. By sequence-tagged site content analysis and
long range mapping we determined that one unstable transgenic line has
integrated an approximately 70 kb segment of the AR locus due to
fragmentation of the AR YAC. Identification of the cis - acting elements
that permit CAG tract instability and the trans -acting factors that
modulate repeat instability in the AR YAC CAG 45 mice may provide insights
into the molecular basis of trinucleotide repeat instability in humans.
相似文献