全文获取类型
收费全文 | 1082489篇 |
免费 | 72129篇 |
国内免费 | 1421篇 |
专业分类
耳鼻咽喉 | 15179篇 |
儿科学 | 34711篇 |
妇产科学 | 28800篇 |
基础医学 | 154451篇 |
口腔科学 | 29754篇 |
临床医学 | 95432篇 |
内科学 | 205531篇 |
皮肤病学 | 24488篇 |
神经病学 | 82130篇 |
特种医学 | 43262篇 |
外国民族医学 | 202篇 |
外科学 | 164324篇 |
综合类 | 21740篇 |
现状与发展 | 1篇 |
一般理论 | 264篇 |
预防医学 | 74844篇 |
眼科学 | 24635篇 |
药学 | 86637篇 |
7篇 | |
中国医学 | 2826篇 |
肿瘤学 | 66821篇 |
出版年
2019年 | 7851篇 |
2018年 | 11419篇 |
2017年 | 8994篇 |
2016年 | 10185篇 |
2015年 | 11370篇 |
2014年 | 15445篇 |
2013年 | 22380篇 |
2012年 | 30929篇 |
2011年 | 32728篇 |
2010年 | 19212篇 |
2009年 | 18062篇 |
2008年 | 30350篇 |
2007年 | 32502篇 |
2006年 | 33130篇 |
2005年 | 31449篇 |
2004年 | 30177篇 |
2003年 | 28943篇 |
2002年 | 27972篇 |
2001年 | 60227篇 |
2000年 | 61677篇 |
1999年 | 51098篇 |
1998年 | 12549篇 |
1997年 | 11082篇 |
1996年 | 11100篇 |
1995年 | 10382篇 |
1994年 | 9392篇 |
1993年 | 8923篇 |
1992年 | 37939篇 |
1991年 | 36393篇 |
1990年 | 35879篇 |
1989年 | 34419篇 |
1988年 | 30975篇 |
1987年 | 30091篇 |
1986年 | 28307篇 |
1985年 | 26538篇 |
1984年 | 19260篇 |
1983年 | 16164篇 |
1982年 | 8855篇 |
1979年 | 17066篇 |
1978年 | 11434篇 |
1977年 | 10269篇 |
1976年 | 8854篇 |
1975年 | 10103篇 |
1974年 | 11687篇 |
1973年 | 11303篇 |
1972年 | 10792篇 |
1971年 | 10107篇 |
1970年 | 9277篇 |
1969年 | 8968篇 |
1968年 | 7950篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
71.
72.
M M Smith J E Thompson D Thomas M Castillo D Carrier S K Mukherji D Gilliam 《AJNR. American journal of neuroradiology》1997,18(2):327
Choristomas, masses of normal tissues in aberrant locations, contain smooth muscle fibers and fibrous tissues. We describe the MR imaging features of two choristomas located in the internal auditory canals and arising from the facial and vestibulocochlear nerves. Both lesions enhanced with contrast material. In one case, enhancement was seen in the geniculate ganglion and greater superficial petrosal nerve. In the other, a medial component enhanced less than the lateral component did. 相似文献
73.
The ability of three Porphyromonas spp., seven Prevotella spp., seven Fusobacterium spp. and two related Bacteroides spp. (B. levii and B. macacae) to degrade an extensive range of synthetic endo-, amino- and diamino peptidase substrates linked to the fluorescent leaving group 7-amido-4-methylcoumarin (NHMec) was investigated. Many more species than was previously recognized exhibited peptidase activities, albeit at lower levels than those already described for Porphyromonas gingivalis. Detection of chymotrypsin-like activity was dependent on which of three NHMec-linked substrates was used, but all species exhibited degradative activity with at least one of these substrates. Elastase-like activity was detected in all species though not all species reacted with each of the elastase substrates. Glycylprolyl peptidase activity was detected in all of the species tested with the exception of F. mortiferum, F. gonidiaformans, F. naviforme and F. necrophorum. While the detection of peptidase activities does not appear to be useful for the differentiation of species within the genera Bacteroides and Prevotella, its ability to differentiate species of the genus Porphyromonas or Fosobacterium further investigation. 相似文献
74.
K. Sjölund S. Fasth R. Ekman L. Hultén H. Jiborn S. Nordgren & F. Sundler 《Neurogastroenterology and motility》1997,9(3):143-150
Tissue specimens from the large bowel of 18 patients with long-standing slow transit constipation were investigated to determine the distribution and density of several neuropeptides and amines in the enteric nerve system, and also of endocrine cells in comparison to normal individuals. CGRP (calcitonin gene-related peptide), galanin, glucagon, GRP (gastrin-releasing peptide), metenkephalin, motilin, neuropeptide Y (NPY), PACAP, peptide YY (PYY), serotonin, somatostatin, substance P and VIP were studied by immunohistochemistry. Tissue concentrations of VIP, substance P and galanin were also measured by radioimmunoassay. Significantly increased VIP, SP and galanin contents were found in specimens from the ascending colon. Levels of VIP and galanin were also increased in the transverse colon. Immunohistochemistry revealed only marginal changes with an increased density of PACAP nerve fibres in the smooth muscle and of VIP and PACAP nerves in the myenteric plexus of the transverse colon. In the descending colon substance P and NPY immunoreactivity were also increased in the myenteric plexus while the density of VIP nerve fibres was reduced in the mucosa/submucosa. The frequency of PYY-containing cells and the 5-HT-containing cells in the ascending colon was significantly increased in the constipated patients. 相似文献
75.
Precise and limited decompression for lumbar spinal stenosis 总被引:3,自引:0,他引:3
Summary Fifty-eight consecutive patients with lumbosacral nerve root entrapment due to spinal stenosis were treated with modified microsurgical decompression. Only the clinically relevant sides and levels were decompressed while the spinous processes, the interspinous ligaments, the medial portion of ligamentum flavum and the functionally important parts of the facet joints were preserved. The reviewers rated recovery as good or excellent in 71% of patients while patient self-assessment indicated 76% good or excellent outcome. These data suggest that microsurgical decompression of spondyloarthritic changes can effectively relieve the signs and symptoms of nerve root compression and that with careful evaluation of all available data the number of nerve roots requiring decomperession is often fewer than what is suggested by diagnositic images alone. 相似文献
76.
C Schmitt J Brachmann W Saggau T Beyer B Waldecker K Scharowski T Hilbel M Montero B Offner W Sch?ls 《Zeitschrift für Kardiologie》1991,80(11):665-672
In 41 patients with recurrent sustained ventricular tachycardia and/or ventricular fibrillation an integrated pacemaker-defibrillator-system (PCD, Medtronic, model 7216 A or 7217 B) was implanted. In 21 out of 24 (88%) patients a new transvenous implantation technique in combination with a subcutaneous patch electrode was used. The implanted devices comprise antibradycardiac pacemaker functions, two different forms of antitachycardiac pacemaker functions (ramp and burst pacing), and internal cardioversion or defibrillation capabilities. During a mean follow-up of 8 months 147 episodes of ventricular tachycardia were detected, 131 of them were terminated successfully by antitachycardiac pacing; in 13 episodes internal cardioversion was applied to revert ventricular tachycardia. Twenty-seven episodes of ventricular fibrillation or rapid ventricular tachycardia (greater than 200/min) were detected and successfully terminated by internal defibrillation. In six patients with intermittent rapid atrial fibrillation, change of antiarrhythmic therapy was required to avoid activation of the device. The new integrated pacemaker-defibrillator systems improve therapy in patients with life-threatening tachyarrhythmias by reducing the number of internal cardioversions/defibrillations; the non-thoracotomy approach reduces the post operative risk. 相似文献
77.
L Lehtola H Lehv?slaiho P Koskinen K Alitalo 《Acta oncologica (Stockholm, Sweden)》1992,31(2):147-150
As the factor binding to the neu protein has been unknown, it has not been possible to confirm experimentally the proposed growth-factor receptor like functions of the neu protein. To approach this problem we constructed a recombinant receptor which enabled ligand regulation of the neu tyrosine kinase. The hybrid receptor consisted of the extracellular ligand binding, transmembrane and protein kinase C-substrate domains joined to the intracellular tyrosine kinase and carboxyl-terminal domains of the neu protein. Several properties of NIH3T3 cells carrying this construct were tested. We obtained the first experimental evidence that the neu proto-oncogene has mitogenic and transforming activities only in the presence of a ligand stimulating its tyrosine kinase activity. Various cellular and molecular biological parameters indicated that the chimeric receptor behaved very similarly to the EGFR. Also, this chimeric receptor has allowed us to compare the constitutive oncogenic and the ligand-activated non-oncogenic activities of the neu tyrosine kinase. In the future we plan to focus on characterization of possible differences between EGFR and neu signalling in more differentiated cellular backgrounds. 相似文献
78.
A Moberg Wing K Wing K Tholin R Sj?str?m B Sandstr?m G Hallmans 《European journal of clinical nutrition》1992,46(8):585-595
Exposure to cadmium via the diet is known to depend to a large extent on the intake of cereal grains, particularly the high-fibre fractions of wheat. Subjects with low iron status absorb more cadmium than those with better iron status. The purpose of the present study was to determine to what extent cadmium accumulation in human placenta is affected by the intake of grain fibre and maternal iron status during pregnancy. Thirty-nine pregnant women participated in the study. In each trimester the women were requested to complete a dietary history and to allow blood samples to be taken for haemoglobin, serum ferritin and serum thiocyanate determinations, the latter as a marker for smoking. At delivery the whole placenta was taken for the determination of the cadmium concentration. The 32 women who had serum thiocyanate levels less than 70 mumol/l, who had completed at least one dietary history and from whom a blood sample was obtained in the third trimester, were included in the final statistical analyses. In the group of women who consumed less than the median intake of grain fibre and had more than 15 micrograms ferritin/l serum in the third trimester, the placenta cadmium concentration was nearly half that in the placentae of women who had consumed more grain fibre or had lower iron status in late pregnancy. 相似文献
79.
80.