全文获取类型
收费全文 | 16440篇 |
免费 | 942篇 |
国内免费 | 478篇 |
专业分类
耳鼻咽喉 | 205篇 |
儿科学 | 94篇 |
妇产科学 | 63篇 |
基础医学 | 3249篇 |
口腔科学 | 798篇 |
临床医学 | 784篇 |
内科学 | 2346篇 |
皮肤病学 | 187篇 |
神经病学 | 1444篇 |
特种医学 | 412篇 |
外科学 | 811篇 |
综合类 | 2222篇 |
预防医学 | 1116篇 |
眼科学 | 361篇 |
药学 | 2555篇 |
9篇 | |
中国医学 | 818篇 |
肿瘤学 | 386篇 |
出版年
2023年 | 153篇 |
2022年 | 536篇 |
2021年 | 690篇 |
2020年 | 379篇 |
2019年 | 352篇 |
2018年 | 327篇 |
2017年 | 365篇 |
2016年 | 420篇 |
2015年 | 471篇 |
2014年 | 753篇 |
2013年 | 1025篇 |
2012年 | 775篇 |
2011年 | 847篇 |
2010年 | 715篇 |
2009年 | 731篇 |
2008年 | 786篇 |
2007年 | 741篇 |
2006年 | 654篇 |
2005年 | 646篇 |
2004年 | 549篇 |
2003年 | 519篇 |
2002年 | 390篇 |
2001年 | 386篇 |
2000年 | 344篇 |
1999年 | 341篇 |
1998年 | 300篇 |
1997年 | 240篇 |
1996年 | 243篇 |
1995年 | 197篇 |
1994年 | 237篇 |
1993年 | 194篇 |
1992年 | 202篇 |
1991年 | 205篇 |
1990年 | 197篇 |
1989年 | 184篇 |
1988年 | 210篇 |
1987年 | 152篇 |
1986年 | 111篇 |
1985年 | 161篇 |
1984年 | 125篇 |
1983年 | 88篇 |
1982年 | 107篇 |
1981年 | 94篇 |
1980年 | 100篇 |
1979年 | 90篇 |
1978年 | 104篇 |
1977年 | 81篇 |
1976年 | 50篇 |
1973年 | 51篇 |
1972年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
81.
Microcystin-LR is the most frequently studied cyclic heptapeptide produced by different genera of cyanobacteria and is hepatotoxic to livestock and human populations. The adverse effects of microcystin-LR on morphology and cytoskeletal elements in different stages of early embryonal development have been studied in vitro. Embryos and whole embryo cultures have been exposed to microcystin-LR (10–100 μM). Actin filaments were visualized by fluorescence staining and the microtubular network labelled by immunostaining. Growth, development and cytoskeleton organization of the embryos embedded in zona pellucida are not affected by microcystin-LR in concentrations up to 100 μM, while whole embryo cell cultures are affected by the presence of microcystin-LR in the culture medium. High microcystin-LR concentrations (100 μM) cause cells to be detached and destroyed, while lower concentrations (10–20 μM) profoundly affect actin and microtubule organization. These effects are confirmed also by the presence of transformed microcystin-LR in all the media at the lowest concentrations. It seems that the changes to the cells are far more serious than that expressed in cell morphology. From our experiments we conclude that the presence of zona pellucida is an effective way of embryo protection against xenobiotics like microcystin-LR. 相似文献
82.
F. Luther J. D. Kindelan D. P. Roberts-Harry J. M. H. Dibbets 《European journal of dental education》1998,2(4):165-171
A questionnaire was used to compare undergraduate student satisfaction with orthodontic teaching in two units; one in Leeds, UK, the other in Marburg, Germany. Whilst the methods of teaching differed between the units, the aim was to highlight aspects of both courses which students might wish to see improved. Statistical analysis suggested that students appreciate clarity of course structure and means of assessment and that use of a course manual is helpful in achieving this. Recommended texts to back-up course work are also appreciated whilst students from both locations, want to see more patients. Alternatives, such as patient case folders, computer-assisted learning packages and use of videos showing treatment progression, seem to be acceptable alternatives should there be difficulty in supplying “real” patients. The relevance of laboratory courses needs to be reviewed. Overall, the use of student questionnaires is seen as a useful tool in monitoring standards of teaching. 相似文献
83.
Hirotsugu Kojima Syunji Sasaki Tetsuya Tamaki Hiroshi Kameda Satoru Yamasaki Michio Kimura 《Medical Electron Microscopy》1994,27(2):149-158
An ultrastructural study was undertaken concerning morphological changes within the autografted patellar tendon (PT) after
being transplanted to the anterior cruciate ligament (ACL) in mongrel dogs. After 4 weeks, the arrangements of both large
and small collagen fibrils in the PT graft became disordered, and the number of inflammatory cells increased. However, the
same PT grafts revealed postsurgical signs of newly-produced collagen fibrils around activated fibroblasts at 12 to 24 weeks.
At 52 weeks after the transplantation, small collagen fibrils increased in both number and density, showing a remarkable morphological
similarity to the collagen fibrils of normal ACL. These data indicate that the characteristics of the PT graft eventually
resemble those of a normal ACL.
This paper was presented in part at the Combined Meeting of the Orthopedic Research Societies of the USA, Japan and Canada
in Banff, Alberta, Canada, October, 1991. 相似文献
84.
枸杞多糖对高温损伤小鼠睾丸曲细精管影响的电镜观察 总被引:2,自引:0,他引:2
为研究枸杞多糖对小鼠睾丸生细红胞的作用,本次以热吹风器对小鼠双侧睾丸透热(B组),另取正常不透热小鼠为空白对照(A组),蒸馏水灌胃对照(C组)和透热后灌鼠枸杞多糖(D组),进行实验观察,待B、C、D各组于透热结束后即刻、3天、1周、2周,5周处死动物,取双侧睾丸,常规作光镜和电镜观察。实验结果表明,B组各期生精细胞进行性受损,属肿胀溶解性细胞变性坏死过程,D组则在1周时受损部位和程度未见进行性加重,5周对基本恢复正常,提示枸杞多糖有明显的抗高温,保护生精细胞作用。 相似文献
85.
86.
富铬酵母抗动脉粥样硬化的研究 总被引:1,自引:0,他引:1
本文观察了富铬酵母对早期动脉粥样硬化大鼠的预防及治疗作用。病理结果表明:在大鼠高脂饲料中接重量比加入0.1%的甲基硫氧嘧啶,在透射电镜下,大鼠主动脉内皮细胞可见大少;模型鼠改食普通饲料40天,内皮下仍可见不典型泡沫细胞,内有空泡,而改食基础饲料并给富铬酵母治疗(0.25g/KgBw/d),内皮下可见泡沫细胞,但空泡消失。在扫描电镜下,模型鼠主动脉内皮细胞肿胀、萎缩、排列紊乱,出现斑块状病变;给予富 相似文献
87.
本实验采用 SD 大鼠,在孕后期行孕鼠一侧子宫动脉中段完全结扎,另一侧作对照.23只孕鼠(150只胎仔)分成未结扎上、下(CU 和 CL)与结扎上、下(LU、LL)四组.结果表明,LU 组宫内胎仔体重、胎盘重、脑肝重均较其它三组有显著下降(P<0.01);LU 组脑/肝重比值及脑/体重比值较其它三组有显著增加(P<0.01).其胎仔呈不均称性宫内生长迟缓(IUGR)。52只胎盘作了光镜观察,12只胎盘作了电镜观察。在已知子宫胎盘血流不足,且胎仔发生 IUGR 的情况下,其胎盘的改变与以往报道的人类 IUGR 胎盘病理改变相一致,从而证实了子宫胎盘血流量下降是 IUGR 发病的重要原因之一。 相似文献
88.
A longitudinal model based on the simplex model is presented to analyze simultaneously means and covariance structure using univariate longitudinal twin data. The objective of the model is to decompose the mean trend into components which can be attributed to those genetic and environmental factors which give rise to phenotypic individual differences and a component of unknown constitution which does not involve individual differences. Illustrations are given using simulated data and repeatedly measured weight obtained in a sample of 82 female twin pairs on six occasions. 相似文献
89.
This report describes an experimental model of chronic tonsillar herniation and its effects on the spinal cord. In ten rats, a small piece of chemically induced mammary cancer was transplanted to the supraoccipital bone. In all cases, the transplanted cancers grew into the posterior fossa, destroying the supraoccipital bone and compressing the cerebellum extradurally. In six of the ten rats, tonsillar herniation was observed at 8–14 weeks after transplantation. Transdural infiltration of the tumor cells was not apparent in any animal. In those rats with tonsillar herniation (n=6), the spinal cord from the C5 to the T8 segments showed enlargement of the central canal without exception. Histological examination revealed the following changes: stretching and thinning of the ependymal cells; swelling of the astrocytic processes; and extracellular edema, predominantly in the dorsal gray matter, but also in the ventral inner portion of the dorsal column. In the control group (n=4) and those rats without tonsillar herniation (n=4), such histological changes of the spinal cord were not observed. Although the lesions can not be regarded as representing mature syringomyelia, they most likely constitute an earlier evolutionary stage. 相似文献
90.
Improving Femoral Bone Density Measurements 总被引:1,自引:0,他引:1
Kenneth G. Faulkner 《Journal of clinical densitometry》2003,6(4):353-358
Femoral bone density measurements are clinically important because of their strong relationship with hip fracture. However, current densitometers have not improved upon femoral densitometry since the introduction of dual-energy X-ray absorptiometry (DXA) systems. Recently, several advances in DXA measurement of the proximal femur have been proposed by various published studies. These advances can be added to existing DXA systems, while maintaining the conventional femoral regions of interest. Both upper neck bone mineral density (BMD) and hip axis length have been reported to be associated with hip fractures. With newer technology that enables a rapid assessment of both hips, bilateral femur measurements are now clinically practical and are of importance in those with T-scores approaching, yet not reaching, diagnostic or therapeutic thresholds. Bilateral femur measurements also reduce precision error compared to a single femur measurement, yielding precision errors less than observed at the spine. With this decrease in precision error, monitoring of bone changes is now possible at the femur with the utility comparable to the spine. 相似文献