全文获取类型
收费全文 | 9365篇 |
免费 | 925篇 |
国内免费 | 38篇 |
专业分类
耳鼻咽喉 | 43篇 |
儿科学 | 259篇 |
妇产科学 | 151篇 |
基础医学 | 1200篇 |
口腔科学 | 207篇 |
临床医学 | 1193篇 |
内科学 | 1647篇 |
皮肤病学 | 98篇 |
神经病学 | 663篇 |
特种医学 | 520篇 |
外科学 | 1104篇 |
综合类 | 180篇 |
一般理论 | 4篇 |
预防医学 | 896篇 |
眼科学 | 827篇 |
药学 | 835篇 |
中国医学 | 9篇 |
肿瘤学 | 492篇 |
出版年
2021年 | 120篇 |
2020年 | 89篇 |
2019年 | 152篇 |
2018年 | 151篇 |
2017年 | 118篇 |
2016年 | 146篇 |
2015年 | 162篇 |
2014年 | 216篇 |
2013年 | 356篇 |
2012年 | 423篇 |
2011年 | 389篇 |
2010年 | 274篇 |
2009年 | 231篇 |
2008年 | 448篇 |
2007年 | 448篇 |
2006年 | 414篇 |
2005年 | 442篇 |
2004年 | 397篇 |
2003年 | 329篇 |
2002年 | 321篇 |
2001年 | 296篇 |
2000年 | 327篇 |
1999年 | 264篇 |
1998年 | 135篇 |
1997年 | 130篇 |
1996年 | 128篇 |
1995年 | 121篇 |
1994年 | 119篇 |
1993年 | 101篇 |
1992年 | 237篇 |
1991年 | 207篇 |
1990年 | 194篇 |
1989年 | 188篇 |
1988年 | 202篇 |
1987年 | 188篇 |
1986年 | 154篇 |
1985年 | 188篇 |
1984年 | 129篇 |
1983年 | 92篇 |
1982年 | 74篇 |
1981年 | 58篇 |
1979年 | 90篇 |
1978年 | 82篇 |
1977年 | 75篇 |
1976年 | 69篇 |
1975年 | 56篇 |
1974年 | 69篇 |
1973年 | 63篇 |
1972年 | 58篇 |
1971年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
21.
22.
23.
24.
Kinnison ML; Perler BA; Kaufman SL; Mitchell SE; Kadir S; Williams GM; White RI Jr 《Radiology》1986,160(3):727-730
In situ saphenous vein grafts are being used with increasing frequency for bypass procedures involving the femoral and popliteal arteries. Complications of these procedures include anastomotic stenoses and persistent arteriovenous fistulae that may result in failure of the graft. Balloon angioplasty and embolotherapy with detachable balloons were employed successfully in three or four recent cases of patients with complications from in situ grafts. Tailored angiography is essential for evaluating in situ grafts, and interventional techniques are extremely useful for managing complications. 相似文献
25.
26.
Two fast magnetic resonance (MR) imaging techniques, advanced Fourier and partial-flip imaging, were used at 0.35 T to examine 21 patients with suspected intracranial lesions; the results were quantitatively compared with a conventional spin-echo study. Both of the fast MR techniques yielded a fourfold reduction in imaging time per section. The advanced Fourier sequence showed contrast that was identical to the conventional spin-echo study with signal-to-noise ratios of 58% and 57% for the first and second echoes, respectively. The partial-flip sequence showed a contrast of 109% and 57% for lesions versus substantia alba, and 107% and 78% for substantia grisea versus substantia alba relative to the first and second echoes of the conventional spin-echo study. The partial-flip sequence was particularly sensitive to magnetic susceptibility; this produced artifacts that may undermine the usefulness of partial flip for routine screening in certain parts of the brain. However, this susceptibility significantly improved the detection of intracranial hemorrhage when compared with the spin-echo sequence, particularly when combined with phase mapping of the partial-flip study. 相似文献
27.
28.
M P Haggard J R Trinder J R Foster A C Lindblad 《Journal of rehabilitation research and development》1987,24(4):193-206
A psychoacoustic rationale was developed for a hearing aid design in which compression of spectral tilt was incorporated without any instantaneous nonlinear distortion. This involved switching between a 'flat' and a 'rising' frequency response; the switching was done slowly to avoid audible transients and was controlled by feedback derived from comparison of output levels in low- and high-frequency channels, approximating voiced/unvoiced detection. The effect of this switching process was to narrow the distribution of spectral tilt values compared with the input. Asynchrony between the switching and the triggering speech structures was avoided by also delaying the signal path. Unfortunately, hearing-impaired listeners performed more poorly on the switching system than on either of the control 'flat' or 'rising' frequency-responses. An explanation is offered (on the basis of growing evidence from perceptual experiments) of the perceptual importance of temporal envelope contours within individual frequency bands. It was possible, in part, to predict individuals' results in the switching condition from age and audiometric or psychoacoustic characteristics. The results suggest a modification to the switching design, and they point to an intrinsic limit to the ability of all hearing aids of the compression type to enhance intelligibility. 相似文献
29.
R. C. Small J. P. Boyle K. R. Elliott R. W. Foster A. J. Watt 《British journal of pharmacology》1989,97(4):1174-1181
1. AH 21-132 is being investigated as a potential chemotherapeutic agent for bronchial asthma. The present experiments were designed to determine whether AH 21-132 shares the activity of theophylline as an antagonist at adenosine A1 receptors and to assess its potency as a relaxant in intestinal smooth muscle. 2. In the transmurally-stimulated guinea-pig ileum, theophylline (1 mM), but not AH 21-132 (1 and 10 microM), antagonized twitch depression induced by adenosine. Higher concentrations (100 microM and 1 mM) of AH 21-132 themselves had a depressant effect. Neither theophylline (1 mM) nor AH 21-132 (1 and 10 microM) antagonized twitch depression induced by noradrenaline. 3. AH 21-132 (100 microM and 1 mM) depressed maximum contractions of ileum induced by both acetylcholine (ACh) and histamine. 4. In ileum treated with hyoscine (1 microM), AH 21-132 (greater than 10 microM) caused a concentration-dependent depression of the log concentration-effect curve for potassium chloride. 5. Simultaneous extracellular electrophysiological and mechanical recording from taenia caeci showed that AH 21-132 (100 microM-1 mM) inhibited spontaneous tension waves and their associated bursts of electrical spike activity. 6. Intracellular electrophysiological recording from taenia caeci showed that the mechano-inhibitory effect of 1 mM AH 21-132 was accompanied by abolition of spontaneous spike activity. Following spike abolition, the membrane potential assumed a value very close to that observed during periods of electrical quiescence prior to drug exposure. 7. AH 21-132 inhibited the activity of cyclic AMP-dependent and cyclic GMP-dependent phosphodiesterases derived from homogenates of ileal smooth muscle.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
30.