全文获取类型
收费全文 | 35792篇 |
免费 | 3217篇 |
国内免费 | 70篇 |
专业分类
耳鼻咽喉 | 271篇 |
儿科学 | 1171篇 |
妇产科学 | 844篇 |
基础医学 | 4966篇 |
口腔科学 | 598篇 |
临床医学 | 4165篇 |
内科学 | 7144篇 |
皮肤病学 | 733篇 |
神经病学 | 3398篇 |
特种医学 | 765篇 |
外国民族医学 | 5篇 |
外科学 | 4966篇 |
综合类 | 543篇 |
一般理论 | 76篇 |
预防医学 | 4276篇 |
眼科学 | 514篇 |
药学 | 2360篇 |
1篇 | |
中国医学 | 48篇 |
肿瘤学 | 2235篇 |
出版年
2023年 | 343篇 |
2022年 | 571篇 |
2021年 | 1117篇 |
2020年 | 711篇 |
2019年 | 1008篇 |
2018年 | 1097篇 |
2017年 | 842篇 |
2016年 | 874篇 |
2015年 | 954篇 |
2014年 | 1273篇 |
2013年 | 1675篇 |
2012年 | 2443篇 |
2011年 | 2396篇 |
2010年 | 1248篇 |
2009年 | 1099篇 |
2008年 | 1862篇 |
2007年 | 1986篇 |
2006年 | 1740篇 |
2005年 | 1683篇 |
2004年 | 1544篇 |
2003年 | 1430篇 |
2002年 | 1190篇 |
2001年 | 628篇 |
2000年 | 717篇 |
1999年 | 585篇 |
1998年 | 337篇 |
1997年 | 281篇 |
1996年 | 232篇 |
1995年 | 210篇 |
1994年 | 198篇 |
1993年 | 205篇 |
1992年 | 513篇 |
1991年 | 479篇 |
1990年 | 417篇 |
1989年 | 417篇 |
1988年 | 393篇 |
1987年 | 374篇 |
1986年 | 370篇 |
1985年 | 339篇 |
1984年 | 333篇 |
1983年 | 229篇 |
1982年 | 151篇 |
1981年 | 156篇 |
1980年 | 144篇 |
1979年 | 263篇 |
1978年 | 165篇 |
1976年 | 141篇 |
1974年 | 174篇 |
1973年 | 165篇 |
1972年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Adenosine receptor-induced cyclic AMP generation and inhibition of 5-hydroxytryptamine release in human platelets. 总被引:1,自引:0,他引:1 下载免费PDF全文
J A Cooper S J Hill S P Alexander P C Rubin E H Horn 《British journal of clinical pharmacology》1995,40(1):43-50
1. We have assessed the effects of adenosine receptor agonists and antagonists on collagen-induced 5-hydroxytryptamine (5-HT) release and cyclic AMP generation in human platelets. 2. 5'-N-ethylcarboxamidoadenosine (NECA) and CGS 21680 elicited accumulations of cyclic AMP with mean EC50 values of 2678 and 980 nM, respectively. The maximal response to CGS 21680 was approximately half that of the response to 10 microM NECA. 3. NECA and CGS 21680 inhibited collagen-induced 5-hydroxytryptamine release with mean EC50 values of 960 and 210 nM, respectively. The maximal response to CGS 21680 was approximately 25% of the response to 10 microM NECA. 4. The A1/A2a-selective adenosine receptor antagonist PD 115,199 was more potent as an inhibitor of NECA-elicited responses than the A1-selective antagonist DPCPX with calculated Ki values of 22-32 nM and > 10 microM, respectively. 5. In the presence of a cyclic AMP phosphodiesterase inhibitor, the effects of CGS 21680 on cyclic AMP accumulation and 5-HT release were enhanced to levels similar to those elicited by 10 microM NECA. In the absence of phosphodiesterase inhibition, CGS 21680 did not antagonise the effects of NECA. Furthermore, endogenous adenosine did not contribute to the effects of CGS 21680 when phosphodiesterase was inhibited. 6. We conclude that an A2a adenosine receptor appears to be involved in the NECA-elicited increases in cyclic AMP levels and inhibition of 5-HT release in human platelets.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
94.
95.
Douglas M. Howarth Martin T. Epstein Paul A. Thomas Leonard W. Allen Rachel Akerman Linda Lan 《European journal of nuclear medicine and molecular imaging》1997,24(12):1465-1469
The efficacy of fractionated out-patient radioiodine therapy in 38 patients with compressive symptoms due to long-standing
large multinodular goitres was assessed. The diagnosis was established by clinical assessment in addition to technetium-99m
pertechnetate thyroid scan or computed tomography scan of the thyroid and mediastinum. Oral iodine-131 therapy was administered
as a 2.22 GBq (60 mCi) cumulative dose over 4 months (555 MBq per month). All patients were monitored with serum thyroid-stimulating
hormone and free thyroxine (± free tri-iodothyronine) assays before the treatment and after each dose fraction. Clinical and
biochemical follow-up was performed on all patients and ranged from 6 to 45 months after therapy. The patients consisted of
35 female and three male patients with a median age of 59 years (range 37–87 years). Prior to treatment 20 patients were biochemically
hyperthyroid and 18 were euthyroid. Overall, 71% of patients reported a subjective improvement in compressive symptoms and
29% reported no change. Clinically assessed reduction in goitre size occurred in 92% of patients while there was no change
in 8%. At 3 months of follow-up, 31% of patients had become hypothyroid and at 18 months 66% were hypothyroid. Seven hyperthyroid
patients (35%) became euthyroid and 13 hyperthyroid patients (65%) became hypothyroid. Three patients who became hypothyroid
experienced neck soreness (transient in one patient, persistent in two patients). There were no differences in outcome between
patients who were hyperthyroid and those who were euthyroid prior to treatment. Fractionated out-patient radioiodine therapy
showed excellent short- and medium-term safety, was very well tolerated and offered a satisfactory alternative treatment to
surgery.
Received 23 May and in revised form 11 August 1997 相似文献
96.
Geraldo F. Busatto Lyn S. Pilowsky Durval C. Costa John Mertehs Dirk Terriere Peter J. Ell Rachel Mulligan Michael J. Travis Josée E. Leysen Dominic Lui Sveto Gacinovic Wendy Waddington Anne Lingford-Hughes Robert W. Kerwin 《European journal of nuclear medicine and molecular imaging》1997,24(2):119-124
The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands.
Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately
2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice
multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free
from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately
100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100
min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic
data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET. 相似文献
97.
Tony Hope Kathleen M. Tilling Kathy Gedling Janet M. Keene Sandra D. Cooper Christopher G. Fairburn 《International journal of geriatric psychiatry》1994,9(2):149-155
‘Wandering’ is one of the most troublesome of behavioural problems in dementia. The term ‘wandering’ covers many different types of behaviour. We examined the hypothesis that the different types of wandering behaviour seen in dementia from a scale using data collected on 83 elderly subjects suffering from either Alzheimer's disease or multiinfarct dementia. We reject the scaling hypothesis. Our data suggest that there are three main categories of wandering behaviour, and that one of these categories is usefully divided into four subcategories. 相似文献
98.
99.
R L Cooper M L Mole G L Rehnberg J M Goldman W K McElroy J Hein T E Stoker 《Toxicology》1992,71(1-2):69-81
Two experiments were conducted in which the acute effects of inhaled methanol on serum hormones associated with reproductive function in the male rat were evaluated. In the first experiment, rats exposed to methanol (0, 200, 5000 and 10,000 ppm) for 6 h were killed at the end of the exposure period (6 h) or the following morning (24 h). Also, because the process of exposure itself could modify neuroendocrine function, the effect of the handling associated with placing the rat in the exposure chamber was evaluated further by dividing the exposed animals into acclimated (2 weeks of prior handling) and non-acclimated groups. At 6 h, an effect of prior handling was noted in the sham-exposed rats, with serum luteinizing hormone (LH) of the non-acclimated group being greater than that of the acclimated group. Serum LH concentrations were altered by methanol exposure, but the direction of change and the exposure level at which an effect was noted differed between the acclimated and non-acclimated rats. Methanol (5000 ppm) reduced serum LH in the non-acclimated animals, while 10,000 ppm increased LH in the acclimated rats. Follicle stimulating hormone (FSH) and testosterone were unchanged by methanol in rats killed at 6 h. Thus, this experiment did not confirm earlier reports that exposure to 200 ppm for 6 h reduced serum testosterone. At 24 h, an effect of prior handling was still present in the hormonal measures, with serum and interstitial fluid testosterone concentrations being greater in the non-acclimated rats. Also, there was a dose x handling interaction with methanol exposure inducing an increase in serum testosterone in the non-acclimated rats (up to 5000 ppm) and a decrease in the acclimated rats (up to 10,000 ppm). In the second experiment, groups of acclimated and non-acclimated rats were exposed to 0 or 5000 ppm methanol for 1, 2 and 6 h and killed immediately after removal from the chamber. Serum LH, testosterone and FSH values were not different in sham- vs methanol-exposed rats at any time point. As in experiment 1, an effect of prior handling was noted. In general, the concentrations of these hormones and serum prolactin in the non-acclimated rats were greater than those observed for acclimated rats. Methanol exposure resulted in increased prolactin concentrations under both handling conditions.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
100.