全文获取类型
收费全文 | 1264篇 |
免费 | 124篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 7篇 |
儿科学 | 7篇 |
妇产科学 | 4篇 |
基础医学 | 294篇 |
口腔科学 | 54篇 |
临床医学 | 79篇 |
内科学 | 107篇 |
皮肤病学 | 5篇 |
神经病学 | 98篇 |
特种医学 | 106篇 |
外科学 | 82篇 |
综合类 | 120篇 |
预防医学 | 216篇 |
眼科学 | 13篇 |
药学 | 119篇 |
1篇 | |
中国医学 | 83篇 |
肿瘤学 | 12篇 |
出版年
2024年 | 7篇 |
2023年 | 25篇 |
2022年 | 77篇 |
2021年 | 74篇 |
2020年 | 72篇 |
2019年 | 57篇 |
2018年 | 54篇 |
2017年 | 45篇 |
2016年 | 38篇 |
2015年 | 44篇 |
2014年 | 92篇 |
2013年 | 78篇 |
2012年 | 72篇 |
2011年 | 65篇 |
2010年 | 35篇 |
2009年 | 62篇 |
2008年 | 53篇 |
2007年 | 49篇 |
2006年 | 54篇 |
2005年 | 41篇 |
2004年 | 41篇 |
2003年 | 37篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 21篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1407条查询结果,搜索用时 0 毫秒
1.
Circulating antisperm antibodies (AsAb) and immunosuppressive material in seminal plasma (SPIM)were determined by solid-phase enzyme staining assay and anticomplement test respectively in 686 patients with abortion (including 285 couples) . 241 fertile couple served as control. It's found that the positive rate of AsAb in infertile patients was significantly higher than that in fertile control,being 36.6% vs 3.3% (P<0.001). AsAb was even more offen detected in recurrent aborting patients. Male patients whose spouses aborted 2-6 fetuses had significantly less SPIM than control, sperm count and sperm motility were also significantly decreased. But the incidence of pyospermia was significantly greater than that in control. It is concluded that AsAb and SPIM have played an important role in the development of recurrent abortions. 相似文献
2.
3.
预防艾滋病健康教育媒体材料效果评价比较研究 总被引:6,自引:2,他引:4
目的评价4种预防艾滋病健康教育媒体材料的信息传播效果和材料效果。该材料由课题组于2003-2005年间设计制作,包括“艾滋病知识”折页、“了解艾滋病”海报、“预防艾滋病健康教育手册”和“认识艾滋病”宣教片等4种。方法2005年12月在珠海市选取小学以上文化程度的18~60岁外来工为测试对象,随机分组对4种材料分别进行评价,各调查了251、248、257和252人,共1008人。通过问卷调查了解受访者的一般情况和对材料信息的可接受性、通俗性和材料形式的生动性等8项指标的评价,采用分级定量赋分的方法进行量化评分,采用SPSS10.1统计软件进行统计分析、比较。结果4种材料的信息传播效果和材料效果总得分平均值分别为74.2±15.0、77.7±13.5、73.0±13.8和77.2±13.6,得分最高的是海报,为77.7±13.5分,最低的是手册,为73.0±13.8分,差异有统计学意义,这种差异主要体现在信息传播效果的差异,而材料效果的差异无统计学意义。通俗性、简明性、生动性和可接受性是影响得分高低的主要因素。结论海报是最适合用于城市外来工进行预防艾滋病健康教育的传播材料,其次是宣教片。 相似文献
4.
5.
Zhiqiang Li Arthur F Gmitro Ali Bilgin Maria I Altbach 《Magnetic resonance in medicine》2007,57(6):1047-1057
Three-point Dixon techniques achieve good lipid-water separation by estimating the phase due to field inhomogeneities. Recently it was demonstrated that the combination of an iterative algorithm (iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL)) with a fast spin-echo (FSE) three-point Dixon method yielded robust lipid-water decomposition. As an alternative to FSE, the gradient- and spin-echo (GRASE) technique has been developed for efficient data collection. In this work we present a method for lipid-water separation by combining IDEAL with the GRASE technique. An approach to correct for errors in the lipid-water decomposition caused by phase distortions due to the switching of the readout gradient polarities inherent to GRASE is presented. The IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications, including pelvic, musculoskeletal, and (breath-hold) cardiac imaging. 相似文献
6.
7.
本研究提出利用经验模式分解(EMD)算法分解混叠有管壁成分的超声多普勒血流信号来实现管壁搏动和血流信号的分离。该方法首先将混叠有管壁搏动的超声多普勒血流信号分解为少量有限的分量,即内模函数(IMFs),然后根据管壁搏动信号与血流信号的功率比变化曲线,用比值法自动确定并去除低频管壁博动成分。在仿真实验中用提出的方法处理模拟的多普勒信号,对于靠近管腔内壁的血流信号其在频域功率谱上的相对误差为50%,在时域幅度的相对误差为45%,与高通滤波器方法的相对误差95%相比,准确性得到提高。基于个人计算机用C语言编程实现提出的算法,对实际采集的人体颈动脉多普勒信号可实现实时分离处理。结果表明:基于经验模式分解的滤波方法能有效客观地滤除管壁搏动信号,更准确地保留低频血流信号成分。 相似文献
8.
The paper studies a surface electromyogram (SEMG) decomposition technique suitable for identification of complete motor unit
(MU) firing patterns and their motor unit action potentials (MUAPs) during low-level isometric voluntary muscle contractions.
The algorithm was based on a correlation matrix of measurements, assumed unsynchronised (uncorrelated) MU firings, exhibited
a very low computational complexity and resolved the superimposition of MUAPs. A separation index was defined that identified
the time instants of an MU's activation and was eventually used for reconstruction of a complete MU innervation pulse train.
In contrast with other decomposition techniques, the proposed approach worked well also when the number of active MUs was
slightly underestimated, if the MU firing patterns partly overlapped and if the measurements were noisy. The results on synthetic
SEMG show 100% accuracy in the detection of innervation pulses down to a signal-to-noise ratio (SNR) of 10 dB, and 93±4.6%
(mean± standard deviation) accuracy with 0 dB additive noise. In the case of real SEMG, recorded with an array of 61 electrodes
from biceps brachii of five subjects at 10% maximum voluntary contraction, seven active MUs with a mean firing rate of 14.1
Hz were identified on average. 相似文献
9.
An adaptive algorithm is described that groups motor unit action potentials (MUAPs), detected in a composite EMG signal during
signal decomposition, and creates partial motor unit action potential trains (MUAPTs). Data-driven MUAP shape and motor unit
firing-pattern based criteria are used to form the clusters. An algorithm for estimating MUAPT temporal parameter, which provides
accurate estimates even for partially defined trains, is used to obtain firing-pattern information. No a priori knowledge
is required regarding the number of clusters or the distribution of their template shapes. The clustering algorithm when applied
to real concentric-needle detected MUAP data provides accurate and useful clustering results. Compared to a classical leader-based
algorithm, it provides more robust performance, is better able to estimate the true number of motor units represented in a
set of detected MUAPs, and obtains more complete and accurate MUAPTs. 相似文献
10.
目的 分析2010—2019年我国居民4类主要慢性病(恶性肿瘤、糖尿病、心血管疾病和呼吸系统疾病)的死亡率变化趋势及影响其变化的因素。方法 数据来自全国疾病监测系统死亡数据资料,运用Joinpoint模型计算死亡率的年度平均变化百分比(AAPC)和年度变化百分比(APC),并用死亡率差别分解法解释该趋势变化的影响因素。结果 2010—2019年我国居民四种慢性病的粗死亡率由456.22/10万上升至556.00/10万,标化死亡率由541.40/10万降至419.83/10万。死亡率变化是人口构成和其它危险因素共同作用的结果,其中人口构成因素促进了恶性肿瘤、糖尿病、心血管疾病和呼吸系统疾病死亡率的上升,贡献值分别48.52/10万、5.12/10万、135.28/10万、38.39/10万;其它危险因素促进糖尿病死亡率上升,而驱使另3种慢性病死亡率下降,贡献值分别- 23.11/10万、1.27/10万、- 55.87/10万、- 49.83/10万。结论 我国综合防控重大慢性病造成的死亡取得一定成效,但与此同时随着老龄化加剧,上述疾病依然是引发死亡的主要原因,卫生健康事业发展面临严峻挑战。 相似文献