全文获取类型
收费全文 | 5604篇 |
免费 | 289篇 |
国内免费 | 59篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 70篇 |
妇产科学 | 99篇 |
基础医学 | 699篇 |
口腔科学 | 95篇 |
临床医学 | 616篇 |
内科学 | 435篇 |
皮肤病学 | 13篇 |
神经病学 | 358篇 |
特种医学 | 692篇 |
外科学 | 690篇 |
综合类 | 784篇 |
预防医学 | 584篇 |
眼科学 | 53篇 |
药学 | 463篇 |
3篇 | |
中国医学 | 114篇 |
肿瘤学 | 145篇 |
出版年
2024年 | 12篇 |
2023年 | 87篇 |
2022年 | 177篇 |
2021年 | 257篇 |
2020年 | 164篇 |
2019年 | 139篇 |
2018年 | 146篇 |
2017年 | 191篇 |
2016年 | 201篇 |
2015年 | 217篇 |
2014年 | 447篇 |
2013年 | 450篇 |
2012年 | 360篇 |
2011年 | 385篇 |
2010年 | 289篇 |
2009年 | 273篇 |
2008年 | 231篇 |
2007年 | 269篇 |
2006年 | 247篇 |
2005年 | 185篇 |
2004年 | 184篇 |
2003年 | 113篇 |
2002年 | 99篇 |
2001年 | 99篇 |
2000年 | 74篇 |
1999年 | 71篇 |
1998年 | 65篇 |
1997年 | 68篇 |
1996年 | 43篇 |
1995年 | 54篇 |
1994年 | 51篇 |
1993年 | 26篇 |
1992年 | 36篇 |
1991年 | 21篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 27篇 |
1987年 | 13篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 23篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有5952条查询结果,搜索用时 15 毫秒
51.
B超心脏图象轮廓的自动检测 总被引:6,自引:1,他引:6
本文提出若干应用横向决策过程的动态规划及序贯模式识别的新方法,充分利用帧间心脏轮廓的动态信息,从超声图象中自动检测、分离心脏的内壁和外壁。 相似文献
52.
53.
Zheng-Lin Jiang Hisao Yamaguchi Akira Takahashi Shingo Tanabe Noboru Utsuyama Toshitaka Ikehara Keiko Hosokawa Hiroyuki Tanaka Yohsuke Kinouchi Hiroshi Miyamoto 《European journal of applied physiology》1995,70(3):234-239
Cerebral blood volume flow and flow velocity have been reported to increase during dynamic exercise, but whether the two increase in parallel and whether both increases occur as functions of exercise intensity remain unsettled. In this study, blood flow velocity in the common carotid artery was measured using the Doppler ultrasound method in eight healthy male students during graded treadmill exercise. The exercise consisted of stepwise progressive increases and decreases in exercise intensity. The peak intensity corresponded to approximately 85% of maximal oxygen consumption. During this exercise, the heart rate (f
c), mean blood pressure (BP) in the brachial artery and mean blood flow velocity (cc) in the common carotid artery increased as functions of exercise intensity. At the peak exercise intensity, (f
c), BP and cc increased by 134.5%, 20.5% and 51.8% over the control levels before exercise (P < 0.01), respectively. The resistance index (RI) and pulsatility index (PI) were determined from the velocity profile and were expected to reflect the distal cerebral blood flow resistance. The RI and PI increased during the graded exercise, but tended to decrease at the highest levels of exercise intensity. As cc increased with increases in exercise intensity it would be expected that cerebral blood flow would also increase at these higher intensities. It is also suggested that blood flow velocity in the cerebral artery does not proportionately reflect the cerebral blood flow during dynamic exercise, since the cerebral blood flow resistance changes. 相似文献
54.
Summary This study investigated whether isokinetic strength training might induce changes in static and dynamic power already achieved as a result of isometric strength training. The subjects were twelve males. The isometric strength and dynamic power of elbow flexors were tested by means of an electric dynamometer and fly-wheel every two weeks. During the first 8 weeks all subjects trained the elbow flexors isometrically at four different positions of elbow joints. This training produced 27–36% gains in isometric strength and 34–46% in power. Thereafter the subjects were divided into two groups: the FG group who trained isokinetically at a fast velocity of 157·s–1, and the SG group at slow velocity of 73·s–1. After 6 weeks of training, the FG group produced a significant gain in power with light equivalent masses and the SG group did so with heavy equivalent masses. Neither group showed change in isometric strength. 相似文献
55.
Dynamic particle image velocimetry (PIV) was applied to the study of the flow field associated with prosthetic heart valves.
The results were compared with those of laser Doppler anemometry (LDA). Anatomically and antianatomically oriented Jyros (JR)
and St. Jude Medical (SJM) valves were compared in the mitral position to study the effects of valve design on the downstream
flow field. The experimental program used a dynamic PIV system utilizing high-speed, high-resolution video to map the true
time-resolved velocity field inside the simulated ventricle. This system was complemented by a study using the more traditional
LDA system for comparison. Based on the experimental data, the following general conclusions can be made. High-resolution
dynamic PIV can capture true chronological changes in the velocity and turbulence fields. It also produces very detailed velocity
and turbulence information comparable to the LDA results. In the vertical measuring plane that passes both the center of the
aortic and mitral valves (A-A section), the two valves (the SJM and the JR) show distinct circulatory flow patterns when the
valve is installed in the antianatomical orientation. Small differences in valve design can generate noticeable differences,
particularly during the accelerating flow phase. The SJM valve maintains a relatively high velocity through the central orifice;
the curved leaflets of the JR valve generate higher velocities with a divergent flow during the accelerating and peak flow
phases. In the velocity field directly below the mitral valve and normal to the previous measuring plane (B-B section), where
characteristic differences in valve design will be visible, symmetrical twin circulations were observed because of the divergent
nature of the flow generated by the two inclined half-disks installed in the antianatomical orientation. The SJM valve, with
a central downward flow near the valve, is contrasted with the JR valve, which has a peripheral downward circulation with
higher, turbulent stresses. 相似文献
56.
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
57.
在动态模拟体液中致密CaP陶瓷表面形貌对类骨磷灰石层形成的影响研究 总被引:7,自引:2,他引:7
磷酸钙陶瓷植入体内后其表面类骨磷灰石层的形成是诱导成骨的先决条件。本实验在模拟体液 (Simu-lated body fluid,SBF)以人体骨骼肌组织的正常生理流率 (2 ml/ 10 0 m l· min)下 ,研究在动态 SBF中致密磷酸钙陶瓷表面形貌对类骨磷灰石层形成的影响。结果表明 :在生理流速条件下 ,材料的粗糙表面有利于类骨磷灰石层的形成 ,加大 SBF中 Ca2 +、HPO4 2 -离子浓度 ,类骨磷灰石层的形成速度加快。本研究进一步证实了材料的几何形貌对类骨磷灰石形成的影响 ,加深了对磷酸钙陶瓷在体内诱导成骨机理的理解 相似文献
58.
ESWL实际焦点位置的理论和数值分析 总被引:6,自引:1,他引:6
从理论和数值模拟两个方面分析了ESWL中的非线性的动力学焦点和实际焦点的位置 ,给出三种典型的动力学焦点的数值结果 ,说明非线性动力学焦点和实际焦点一般不是几何焦点 ,指出正确确定实际焦点在ESWL技术中的重要性。 相似文献
59.
A nonlinear dynamic morphometric model of breathing mechanics during artificial ventilation is described. On the basis of the Weibel symmetrical representation of the tracheobronchial tree, the model accurately accounts for the geometrical and mechanical characteristics of the conductive zone and packs the respiratory zone into a viscoelastic Voigt body. The model also accounts for the main mechanisms limiting expiratory flow (wave speed limitation and viscous flow limitation), in order to reproduce satisfactorily, under dynamic conditions, the expiratory flow limitation phenomenon occurring in normal subjects when the difference between alveolar pressure and tracheal pressure (driving pressure) is high. Several expirations characterized by different levels of driving pressure are simulated and expiratory flow limitation is detected by plotting the isovolume pressure–flow curves. The model is used to study the time course of resistance and total cross-sectional area as well as the ratio of fluid velocity to wave speed (speed index), in conductive airway generations. The results highlight that the coupling between dissipative pressure losses and airway compliance leads to onset of expiratory flow limitation in normal lungs when driving pressure is increased significantly by applying a subatmospheric pressure to the outlet of the ventilator expiratory channel; wave speed limitation becomes predominant at still higher driving pressures. 相似文献
60.
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