全文获取类型
收费全文 | 55249篇 |
免费 | 3460篇 |
国内免费 | 1508篇 |
专业分类
耳鼻咽喉 | 242篇 |
儿科学 | 1030篇 |
妇产科学 | 690篇 |
基础医学 | 5118篇 |
口腔科学 | 455篇 |
临床医学 | 6629篇 |
内科学 | 6919篇 |
皮肤病学 | 224篇 |
神经病学 | 2273篇 |
特种医学 | 2506篇 |
外国民族医学 | 1篇 |
外科学 | 4964篇 |
综合类 | 8367篇 |
一般理论 | 1篇 |
预防医学 | 4151篇 |
眼科学 | 245篇 |
药学 | 10695篇 |
26篇 | |
中国医学 | 4282篇 |
肿瘤学 | 1399篇 |
出版年
2024年 | 134篇 |
2023年 | 696篇 |
2022年 | 1333篇 |
2021年 | 1930篇 |
2020年 | 1850篇 |
2019年 | 1473篇 |
2018年 | 1529篇 |
2017年 | 1517篇 |
2016年 | 1582篇 |
2015年 | 1658篇 |
2014年 | 3678篇 |
2013年 | 3656篇 |
2012年 | 3488篇 |
2011年 | 3836篇 |
2010年 | 2975篇 |
2009年 | 2801篇 |
2008年 | 2740篇 |
2007年 | 2780篇 |
2006年 | 2502篇 |
2005年 | 2084篇 |
2004年 | 1701篇 |
2003年 | 1491篇 |
2002年 | 1227篇 |
2001年 | 1061篇 |
2000年 | 988篇 |
1999年 | 845篇 |
1998年 | 733篇 |
1997年 | 709篇 |
1996年 | 645篇 |
1995年 | 607篇 |
1994年 | 549篇 |
1993年 | 505篇 |
1992年 | 457篇 |
1991年 | 371篇 |
1990年 | 376篇 |
1989年 | 362篇 |
1988年 | 364篇 |
1987年 | 281篇 |
1986年 | 256篇 |
1985年 | 286篇 |
1984年 | 319篇 |
1983年 | 206篇 |
1982年 | 266篇 |
1981年 | 208篇 |
1980年 | 180篇 |
1979年 | 153篇 |
1978年 | 149篇 |
1977年 | 127篇 |
1976年 | 105篇 |
1973年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Takashi Hineno M.D. Mutsuhiko Mizobuchi M.D. Oh-ichi Nishimatsu M.D. Jun Horiguchi M.D. Yasuo Kakimoto M.D. 《Psychiatry and clinical neurosciences》1994,48(3):583-587
Abstract: Studies on the circadian rhythm of urine excretion in healthy men have demonstrated that the maximal urine flow occurs in the early afternoon and the minimal around midnight. In this study, an abnormality in the variation of urine volume was found in parkinsonian patients. Urine samples were collected during daytime (9:00–21:00) and nighttime (21:00–9:00). Fifteen healthy control subjects were examined and found to excrete 60% during the daytime and 40% during the nighttime of the total urine volume. Sixteen parkinsonian patients excreted 43% during the daytime and 57% during the nighttime. In contrast to the control subjects, the parkinsonian patients excreted a smaller volume of their urine during the daytime than during the nighttime. This finding might be related to the degeneration of dopaminergic and/or nondopaminergic neurons in the brain which control urinary excretion. 相似文献
23.
Summary: We studied the effect of antiepileptic drugs (AEDs) on internal carotid artery (ICA) blood flow velocity, as an index of total cerebral blood flow (CBF). The subjects were 45 newly diagnosed children with febrile convulsion or epilepsy who were seizure-free for a period long enough not to affect the results. They had no neurologic deficit, received fixed monotherapy, and were examined by a noninvasive Doppler ultrasound method, in comparisonwith 13 age-matched normal volunteers with no AED. In 30 patients, the measurements were performed before and after AED administration [10 with phenobarbital (PB), 10 with carbamazepine (CBZ), and 10 with valproate (VPA)], and performed before and after AED discontinuation in the remaining 15 patients (all with PB). Normal volunteers underwent the two consecutive examinations with a mean interval equal to that of the entire patient group, and there was no difference in velocity values between the measurements. In patients receiving CBZ or VPA, a significant reduction was noted in blood flow velocity after drug administration. Although velocity values in the patients receiving PB did not change after drug administration, they were significantly increased after complete discontinuation. In the present study, a slight but significant reduction in CBF caused by AED administration at therapeutic doses in children was suggested. 相似文献
24.
Ronald G. Pratt Jie Zheng Brent K. Stewart Yoseph Shiferaw Anthony J. McGoron Ranasinghage C. Samaratunga Stephen R. Thomas 《Magnetic resonance in medicine》1997,37(2):307-313
A limited flip angle gradient-echo 3D volume acquisition imaging protocol for mapping partial pressure of oxygen (pO2) in perfluorocarbon compounds (PFCs) at low field (0.14 T) is presented. The pO2 measurement method is based on the paramagnetic effect of dissolved molecular oxygen (O2) which reduces the PFC 19F T1? Specific objectives related to imaging of PFCs through use of the protocol include improved image signal-to-noise characteristics and elimination of 19F chemical shift artifacts. A parametric Wiener deconvolution filtering algorithm is used for suppression of 19F chemical shift artifacts. Application of the protocol is illustrated in a series of calculated pO2 maps of a gas equilibrated, multi-chamber phantom containing perfluorotributylamine (FC-43). The utility of the protocol is demonstrated in vivo through images of a commercially available perfluorocarbon based blood substitute emulsion containing FC-43 sequestered in the liver and spleen of a rat. 相似文献
25.
用放射免疫法测定产后40天和60天乳母血清泌乳素基础水平和吸吮后泌乳素最大反应性增值,发现其与乳母泌乳量、婴儿吸吮频率、吸吮时间之间均不存在正相关关系,推测引起泌乳素分泌除吸吮外,还存在其他机理。 相似文献
26.
These studies demonstrate the presence of pontomedullary areas in the rat brainstem which, when stimulated electrically, serve to set postural muscle tone in the hindlimbs. Low amplitude stimulation of the dorsal tegmental field (DTF) was found to inhibit postural muscle tone and, in some rats, was found to decrease mean arterial pressure. Low amplitude stimulation of the ventral tegmental field (VTF) was found to increase postural muscle tone and, in all cases tested, was found to increase mean arterial pressure. 相似文献
27.
Plasma volume estimation using indocyanine green with biexponential regression analysis of the decay curves 总被引:2,自引:0,他引:2
We studied seven analytical methods of estimating the plasma volume from the decay curves of indocyanine green. Fifteen volunteers received 1.0 mgkg−1 of the dye by intravenous injection and the plasma concentration was measured continuously using spectrophotometry. Plasma volumes were calculated using three single-regression methods (1-a, 1-b, 1-c) and four biexponential regression methods (2-a, 2-b, 2-c, 2-d). The means (SD) of 1-a, 1-b and 1-c were 39 (5.0), 44 (5.7) and 54 (11.5) mlkg−1 , respectively, and these were significantly different from each other (p < 0.05). The values for methods 2-b, 2-c and 2-d were similar to each other: 39 (4.6), 40 (4.1) and 40 (4.0) mlkg−1 , respectively. These required more than 3 min circulation or mixing time. When the time allowed for mixing was less than 3 min (method 2-a) the plasma volume was underestimated. We conclude that plasma volume estimation using indocyanine green and spectrophotometry is most accurate when the mixing time is adequate (3–5 min) and the decay curves are analysed using biexponential regression. 相似文献
28.
Summary. The aim of the present study was to establish a more differentiating indicator of plasma membrane integrity of spermatozoa than the classic version of the hypoosmotic swelling test according to Jeyendraan. Spermatozoa were prepared by density gradient centrifugation (90% Percoll) to select 'fertilization competent' spermatozoa only. After a second washing procedure sufficiently pure sperm cell suspensions were obtained. The volume distributions of these sperm cells were measured with a Coulter Counter at 25 °C after adaptation in 300 mosmolar NaCl solution resp. 150 mosmolar NaCl solution for 5 min. These volume distributions showed significantly different patterns for the isotonic and hypotonic stress situation in the simple salt solution. Moreover, the comparison of the response to hypoosmotic stress showed more than four reproducible characteristic patterns, promising well differentiated results for different sperm populations. The new method for the detection of hypoosmotic swelling effect might be a real and valuable functional parameter. 相似文献
29.
Takehisa Akiyama M.D. Nobutaka Osawa M.D. Kaoru Shimanuki M.D. Kimio Yashiro M.D Tadashi Oyake Ph.D. 《Pediatrics international》1991,33(1):20-26
As a model system for mucocutaneous lymph node syndrome (MCLS), we have advocated and used mice which had been rendered tolerant to Streptococcus pyogenes-associated antigens by neonatal infection with group A fteta-hemolytic streptococci, because these mice have shown a variety of peculiar bioimmunological characteristics bearing a striking resemblance to those of MCLS patients. The results of our current investigations reaffirmed the reliability of the animal model by indicating that mice subjected to neonatal infection with 5. pyogenes , or inoculation with streptococcal pyrogenic exotoxin (SPE) in Freund's adjuvant, were perfect counterparts of patients with MCLS on account of their platelet activation and hyperaggregability in response to provocative treatment, which are familiar findings in this disease. 相似文献
30.