全文获取类型
收费全文 | 12024篇 |
免费 | 860篇 |
国内免费 | 456篇 |
专业分类
耳鼻咽喉 | 228篇 |
儿科学 | 147篇 |
妇产科学 | 32篇 |
基础医学 | 2374篇 |
口腔科学 | 157篇 |
临床医学 | 840篇 |
内科学 | 774篇 |
皮肤病学 | 94篇 |
神经病学 | 2115篇 |
特种医学 | 1015篇 |
外科学 | 448篇 |
综合类 | 1236篇 |
预防医学 | 978篇 |
眼科学 | 253篇 |
药学 | 730篇 |
3篇 | |
中国医学 | 1738篇 |
肿瘤学 | 178篇 |
出版年
2024年 | 62篇 |
2023年 | 189篇 |
2022年 | 377篇 |
2021年 | 490篇 |
2020年 | 381篇 |
2019年 | 324篇 |
2018年 | 321篇 |
2017年 | 384篇 |
2016年 | 395篇 |
2015年 | 410篇 |
2014年 | 666篇 |
2013年 | 973篇 |
2012年 | 665篇 |
2011年 | 783篇 |
2010年 | 591篇 |
2009年 | 584篇 |
2008年 | 649篇 |
2007年 | 571篇 |
2006年 | 553篇 |
2005年 | 484篇 |
2004年 | 415篇 |
2003年 | 340篇 |
2002年 | 329篇 |
2001年 | 255篇 |
2000年 | 230篇 |
1999年 | 188篇 |
1998年 | 173篇 |
1997年 | 170篇 |
1996年 | 149篇 |
1995年 | 164篇 |
1994年 | 155篇 |
1993年 | 150篇 |
1992年 | 102篇 |
1991年 | 115篇 |
1990年 | 68篇 |
1989年 | 77篇 |
1988年 | 61篇 |
1987年 | 49篇 |
1986年 | 39篇 |
1985年 | 50篇 |
1984年 | 37篇 |
1983年 | 32篇 |
1982年 | 27篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
Electrodermal Lability and Visual Information Processing 总被引:1,自引:0,他引:1
Individual differences in electrodermal lability have been related to performance in vigilance and reaction time tasks. The goal of the present study was to employ an "additive factors" approach to identify the stages of information processing that might underlie these effects. Nineteen labile and 17 stabile subjects performed a choice reaction time task in which a visual imperative stimulus was presented under two conditions of intensity (presumed to affect the speed of pre-processing operations) X three conditions of degradation (which influences later encoding processes related to feature extraction). Measures of both reaction time and movement time were obtained. The major findings were: (a) labile subjects had faster reaction times than stabiles, and (b) lability interacted significantly with stimulus degradation. Labiles also tended (p less than .10) to have faster movement times. This pattern indicates that labiles and stabiles differ in the performance of later encoding operations, and possibly in the speed of motor processes as well. However, they do not appear to differ in the early pre-processing of the simple physical attributes of a stimulus. 相似文献
92.
股骨CT图像轮廓跟踪方法 总被引:3,自引:0,他引:3
目的 为重建和测量股骨的解剖结构,需要大量地读取CT图像的信息,以获得股骨轮廓的坐标值。方法本研究采用直方图阈值图像分割、Kirsh边缘提取法获得股骨的二值化轮廓图像。结果轮廓坐标的提取应用了“迷宫”边缘跟踪算法。结论本方法可大量、快捷、正确地提取图像轮廓信息。 相似文献
93.
A new algorithmic-based digital filter processing system for real-time continuous blood pressure (BP) measurement and analysis in freely-moving conscious rats has been developed. Real-time recognition of BP waveforms, real-time noise rejection and determination of representative waveform indexes (WIs) at indicated time points using digital filters and Smirnov's rejection test were realized with this system. Digital filters were applied for two different purposes: waveform segmentation and smoothing the calculations of representative WIs. Smirnov's rejection test was used for real-time noise rejection and yielded an accurate rejection rate of 99.99%. The result was that the digital filter processing and Smirnov's rejection test realized accurate real-time BP measurement and analysis in freely-moving conscious rats using a personal computer. 相似文献
94.
Mansy HA Hoxie SJ Patel NH Sandler RH 《Medical & biological engineering & computing》2005,43(1):56-62
Vascular access for renal dialysis is a lifeline for about 120 000 individuals in the United States. Stethoscope auscultation
of vascular sounds has some utility in the assessment of access patency, yet can be highly skill-dependent. The objective
of the study was to identify acoustic parameters that are related to changes in vascular access patency. The underlying hypothesis
is that stenoses of haemodialysis access vessels or grafts cause vascular sound changes that are detectable using computerised
data acquisition and analysis. Eleven patients participated in the study. Their vascular sounds were recorded before and after
angiography, which was accompanied by angioplasty in most patients. The sounds were acquired using two electronic stethoscopes
and then digitised and analysed on a personal computer. Vessel stenosis changes were found to be associated with changes in
acoustic amplitude and/or spectral energy distribution. Certain acoustic parameters correlated well (correlation coefficient=0.98,
p<0.0001) with the change in the degree of stenosis, suggesting that stenosis severity may be predictable from these parameters.
Parameters also appeared to be sensitive to modest diameter changes (>20%), (p<0.005, Wilcoxon rank sum test). These results
suggest that computerised analysis of vascular sounds may be useful in vessel patency surveillance. Further testing using
longitudinal studies may be warranted. 相似文献
95.
A. N. Chalazonitis MD Ph.D D. Koumarianos RT J. Tzovara MD P. Chronopoulos MD 《Journal of digital imaging》2003,16(2):216-229
Over the past decade, the technology that permits images to be digitized and the reduction in the cost of digital equipment allows quick digital transfer of any conventional radiological film. Images then can be transferred to a personal computer, and several software programs are available that can manipulate their digital appearance. In this article, the fundamentals of digital imaging are discussed, as well as the wide variety of optional adjustments that the Adobe Photoshop 6.0 (Adobe Systems, San Jose, CA) program can offer to present radiological images with satisfactory digital imaging quality. 相似文献
96.
A brief introduction to the Danish Cytogenetic Central Register (DCCR) is given, and possibilities, principles and problems concerning the establishment and maintenance of a national cytogenetic register are presented.
Various data carrier media for registers in general are discussed, of which the magnetic disc is considered most appropriate. General principles for programs capable of performing insertions, deletions and other modifications in the data base are outlined as well as the principles for the programs in the DCCR.
The individual records should preferably be identified by aid of a central person registration number (CPR) rather than by name. The data should be stored and sorted by this identification in order to facilitate retrieval of a desired record. The structure of the records is discussed with regard to prevention of the occurrence of certain errors as well as the optimization of processing.
Flexibility and economy of space are achieved by using programs able to handle records of unequal length, and problems occurring in connection with this are discussed. The question of how to protect sensitive data is dealt with, and two different methods used in the DCCR are outlined. Programs capable of analyzing karyotypes with the purpose of recognizing various cytogenetic syndromes have been developed for use in the DCCR. Various examples of computing times of typical program runs are presented. 相似文献
Various data carrier media for registers in general are discussed, of which the magnetic disc is considered most appropriate. General principles for programs capable of performing insertions, deletions and other modifications in the data base are outlined as well as the principles for the programs in the DCCR.
The individual records should preferably be identified by aid of a central person registration number (CPR) rather than by name. The data should be stored and sorted by this identification in order to facilitate retrieval of a desired record. The structure of the records is discussed with regard to prevention of the occurrence of certain errors as well as the optimization of processing.
Flexibility and economy of space are achieved by using programs able to handle records of unequal length, and problems occurring in connection with this are discussed. The question of how to protect sensitive data is dealt with, and two different methods used in the DCCR are outlined. Programs capable of analyzing karyotypes with the purpose of recognizing various cytogenetic syndromes have been developed for use in the DCCR. Various examples of computing times of typical program runs are presented. 相似文献
97.
Professor K. M. Patil M. S. Srinath 《Medical & biological engineering & computing》1990,28(5):416-422
A new image-processing system, using a video digitiser with an IBM-compatible PC/AT, is developed for acquisition and processing
of low-contrast, lowintensity barographic images of both feet for assessment of pressure distribution during standing and
walking. Data displays, in the form of centres of pressures, isopressures contours, perspective views of pressures, grey scale
image and walking pressure patterns, combined image of walking pressures, paths of centres of pressures and pressure variations
with time, are developed. These have provided very useful and early information regarding the internal structural changes
in the bones of the foot and sites at risk of ulcer development in leprosy subjects and enable suitable corrective orthopaedic
procedures to be adopted.
unitl the end of November 1990, and will then return to the Indian Institute of Technology. 相似文献
98.
Turnquist HR Vargas SE Schenk EL McIlhaney MM Reber AJ Solheim JC 《Immunologic research》2002,25(3):261-269
Prior to the binding of antigenic peptide, a complex of chaperone proteins associates with the Major Histocompatibility Complex
(MHC) class I heavy chain/β2m heterodimer. Although each dornain of the MHC class I heavy chain contains amino acid resid uses that influence chaperone
binding, there are several pieces of evidence that point to an interaction between the MHC clas 1α2/α3 domains and tapasin.
In egard to the site on tapasin involved in the tapasin/MHC interface, we have found that a particular region of tapasin (containing
amino acid residues 334–342) is necessary for the binding of tapasin to the MHC class I heavy chain. Our results also indicate
that amino acids in this region of tapasin also affect the proportion of MHC class I open forms expressed at the cell surface
and MHC class I egress from the endoplasmic reticulurn. Based on these results and those obtained by other laboratories, a
model for MHC class I/tapasin interaction is proposed. 相似文献
99.
Dr Y. X. Yang B. S. Xie Z. X. Zhou J. N. Liu Y. Y. Xue G. L. Lv 《Medical & biological engineering & computing》1998,36(3):355-358
An experimental animal hypoxia model has been developed. It consists of two sensors (an in vitro and in vivo model), an experimental
device and a computer signal processing system. This method can easily be applied to determine and analyse blood oxygen saturation
at various hypoxia levels. It can also be used to evaluate the accuracy of pulse oximetry over a wide range of oxyhemoglobin
desaturation levels. The DC and AC components of recorded red and infra-red signals, the dual-wavelength ratio R12 and the reading of a pulse oximeter (SpO2) can be automatically calculated and displayed on a computer screen. Preliminary results of the animal hypoxia test indicate
that the measurements made by the instrument correlate well with the oxygen saturation readings of the automatic blood gas
analyser AVL945. The computer analysis system is suitable for repeated estimations in the animal model. 相似文献
100.
A PC-AT based program for conversion of magnetic resonance imaging (MRI) scans into coordinate input for finite element mesh generation is presented. The program is written in Borland C + +3.1 and is compatible with every general-use personal computer, permitting the use of MS-DOS 3.0 or higher with a Microsoft mouse. The program is menu driven and does not demand specialised knowledge from the user. The system and memory requirements are minimal -- 640 kB RAM -- and it runs as a stand-alone program. A second program allows the construction of a three-dimensional representation of the limb sub-structure and generation of the FE mesh from the converted cross-sectional scans. The capabilities of the program are demonstrated using cross-sectional scans of the upper arm; the fat, muscle and bone contours were obtained to a very high level of precision (0.4 mm). 相似文献