全文获取类型
收费全文 | 22900篇 |
免费 | 1650篇 |
国内免费 | 663篇 |
专业分类
耳鼻咽喉 | 556篇 |
儿科学 | 194篇 |
妇产科学 | 134篇 |
基础医学 | 4438篇 |
口腔科学 | 311篇 |
临床医学 | 1459篇 |
内科学 | 2097篇 |
皮肤病学 | 161篇 |
神经病学 | 4768篇 |
特种医学 | 1488篇 |
外国民族医学 | 1篇 |
外科学 | 949篇 |
综合类 | 2230篇 |
预防医学 | 1420篇 |
眼科学 | 1570篇 |
药学 | 2289篇 |
3篇 | |
中国医学 | 584篇 |
肿瘤学 | 561篇 |
出版年
2023年 | 210篇 |
2022年 | 323篇 |
2021年 | 686篇 |
2020年 | 584篇 |
2019年 | 540篇 |
2018年 | 599篇 |
2017年 | 594篇 |
2016年 | 637篇 |
2015年 | 619篇 |
2014年 | 1022篇 |
2013年 | 1377篇 |
2012年 | 1183篇 |
2011年 | 1211篇 |
2010年 | 1108篇 |
2009年 | 1090篇 |
2008年 | 1190篇 |
2007年 | 1102篇 |
2006年 | 1019篇 |
2005年 | 864篇 |
2004年 | 808篇 |
2003年 | 669篇 |
2002年 | 589篇 |
2001年 | 540篇 |
2000年 | 475篇 |
1999年 | 428篇 |
1998年 | 471篇 |
1997年 | 440篇 |
1996年 | 331篇 |
1995年 | 349篇 |
1994年 | 286篇 |
1993年 | 265篇 |
1992年 | 271篇 |
1991年 | 269篇 |
1990年 | 221篇 |
1989年 | 207篇 |
1988年 | 211篇 |
1987年 | 193篇 |
1986年 | 199篇 |
1985年 | 356篇 |
1984年 | 280篇 |
1983年 | 210篇 |
1982年 | 231篇 |
1981年 | 213篇 |
1980年 | 180篇 |
1979年 | 137篇 |
1978年 | 98篇 |
1977年 | 76篇 |
1976年 | 77篇 |
1975年 | 35篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
51.
Receiver operating characteristic curves and accuracy parameters were computed for traditional sperm characteristics (concentration, motility, morphology) and the number of peroxidase negative cells, and the concentration of adenosine triphosphate (ATP) in semen from populations of fertile and infertile men, and men who achieved a pregnancy after varicocele treatment. The percentage and concentration per millilitre of spermatozoa with rapid linear progressive motility, and the ATP concentration, provided the best discrimination between fertile and treated fertile from infertile men. The misclassification rate was higher for sperm morphology, total progressive motility and viability, whereas sperm concentration and the total sperm count per ejaculate had the worst discriminating power. The number of peroxidase negative cells per 100 spermatozoa was highly specific in identifying men who achieved pregnancy after varicocele treatment. The lower limit of normality of sperm characteristics was remarkably different between fertile men and men achieving pregnancy after treatment or during infertility work-up. 相似文献
52.
53.
用视诱发电位和富里叶变换作视力客观估计 总被引:2,自引:0,他引:2
目的:研究用图形视觉诱发电位(PVEP)和离散富里叶变换(DFT)作视力客观估计的方法。方法:检测对象为33只正常眼。用翻转频率为10次/秒,条纹张角分别为30、20、18、12、10、6、4和2弧分的垂直方波光栅图形刺激,记录相应的稳态图形视诱发电位。用离散富里叶交换提取WEP频谱中10Hz成分的幅值。以光栅条纹张角为横坐标、相应的VEP频谱幅值为纵坐标作关系曲线,取阈值附近的近似线性部分的数据点作直线回归,用外推法求得阈值和视力。结果:比较VEP所测之视力与用国际标准视力表所测之视力,可见在本研究中70%的受检眼VEP视力估计较准确。结论:用本研究中的VEP技术客观地测量视力可靠性较高。眼科学报1997;13:59~61。 相似文献
54.
Analysis of reflex activity in cardiac sympathetic nerve induced by myelinated phrenic nerve afferents 总被引:2,自引:0,他引:2
Electrical stimulation of the phrenic nerve afferents evoked excitatory responses in the right inferior cardiac sympathetic nerve in chloralose-anaesthetized cats. The reflex was recorded in intact and spinal cats. The latency and threshold of the volley recorded from the phrenic nerve as well as of the cord dorsum potentials evoked by electrical stimulation of the phrenic nerve indicated that group III afferents were responsible for this reflex. The phrenicocardiac sympathetic reflex recorded in intact cats was followed by a silent period. The maximum amplitude of the reflex discharges was 800 microV, the latency was 83 ms and the central transmission time 53 ms. Duration of the silent period lasted up to 0.83 s. In spinal cats the reflex was recorded 5.5-8 h after spinalization. The maximum amplitude of the spinal reflex discharges ranged from 22 to 91 microV and the latency from 36 to 66 ms. 相似文献
55.
56.
Purpose. To estimate disease activity in patients with systemic sclerosis using contrast-enhanced MRI of the skin.
Material and Methods. In a pre-study, sequences of a low-field (0.2 T) scanner (Artoscan, Esaote, Genova, Italy) were optimized for detection of
intravenous contrast (0.1 mmol/l Gd-DTPA) in six patients with the autoimmune disease systemic scleroderma. Based on the results
of the pre-study, 17 patients with scleroderma (7 sclerotic/10 active inflammatory disease) were scanned using gradient-spoiled
3D GRE sequences (FA 90 °, TR 100 ms, TE 18 ms), which had been established as most sensitive for intravenous contrast. Contrast
enhancement of the skin was determined quantitatively by contrast-to-noise ratios (CNR), comparing post- to pre-contrast and
dynamic scans (for 6 min, 1 acquisition/min). Patients in the chronic state with sclerodactylia and active inflammation of
the hands were considered separately and compared to a control group (n = 10) matched according to age.
Results. CNR increase after intravenous contrast was significantly higher in patients with active disease (86 ± 16 % increase) than
sclerosing disease (29 ± 3 %, p < 0.05) and the control group (4 ± 2 %, p < 0.05). The dynamic examination showed a significantly slower decrease after the peak rise in the first minute in patients
with active disease (CNR 15.4 ± 0.7 to 14.2 ± 1.4) than in those with chronic disease (14.1 ± 0.5 to 11.3 ± 0.9, p < 0.05).
Discussion. Capillary leakage is the most likely explanation for the increased enhancement in patients with active scleroderma. Using
sequences optimized for contrast detection, disease activity in the course of scleroderma and response to therapy can be determined
by MRI in the future.
相似文献
57.
Cesare M.N. Terracciano David Tweedie Kenneth T. MacLeod 《Pflügers Archiv : European journal of physiology》1997,433(4):540-542
. We have estimated sarcoplasmic reticulum calcium content using rapid application of caffeine on voltage clamped, isolated
guinea-pig ventricular myocytes. Caffeine induces the release of calcium from the sarcoplasmic reticulum and this calcium
is extruded from the cells by the sarcolemmal Na/Ca exchange. Integrating the inward Na/Ca exchange current thus allows estimations
of sarcoplasmic reticulum calcium content. Ventricular myocytes were stimulated to reach new steady-states by action potential
voltage clamps of varying duration. Once contractile steady-state had been reached caffeine was rapidly applied in place of
the next action potential and sarcoplasmic reticulum calcium content measured. Prolonging the action potential duration increased
sarcoplasmic reticulum calcium content and vice-versa. This calcium loading may underlie the positive inotropic effect of
increased action potential duration.
Received: 11 July 1996 / Received after revision: 15 October 1996 / Accepted: 26 November 1996 相似文献
58.
Ureteropelvic junction obstruction was noted in a newborn male infant with acro-pectoro-renal field defect. To our knowledge, this association has not previously been reported. Ultrasonography of the urinary tract should be performed on all children with aplasia of the pectoralis major muscle. 相似文献
59.
60.
本文参考X-衍射数据,采用MNDO程序计算了不同构型、构象PAM类的生成热,结合核磁共振数据讨论了PAM类构象等问题.结果表明,PAM类在水溶液中:顺式体肟基可以自由旋转,任何一种构象都可能成为药效构象;反式体肟基本不可能存在稳定的平面构象,其药效构象只能是优势构象.用MNDO程序中反应途径的计算法,还计算了顺、反式肟基构型相互转变的势垒,为探讨PAM类重活化机理提供了一定的参考. 相似文献