全文获取类型
收费全文 | 18037篇 |
免费 | 1242篇 |
国内免费 | 346篇 |
专业分类
耳鼻咽喉 | 130篇 |
儿科学 | 506篇 |
妇产科学 | 333篇 |
基础医学 | 1202篇 |
口腔科学 | 279篇 |
临床医学 | 1966篇 |
内科学 | 5011篇 |
皮肤病学 | 265篇 |
神经病学 | 871篇 |
特种医学 | 864篇 |
外科学 | 1631篇 |
综合类 | 1387篇 |
预防医学 | 1954篇 |
眼科学 | 520篇 |
药学 | 1522篇 |
2篇 | |
中国医学 | 264篇 |
肿瘤学 | 918篇 |
出版年
2024年 | 50篇 |
2023年 | 745篇 |
2022年 | 1253篇 |
2021年 | 1677篇 |
2020年 | 1263篇 |
2019年 | 1471篇 |
2018年 | 1310篇 |
2017年 | 785篇 |
2016年 | 515篇 |
2015年 | 510篇 |
2014年 | 1279篇 |
2013年 | 1045篇 |
2012年 | 674篇 |
2011年 | 796篇 |
2010年 | 637篇 |
2009年 | 617篇 |
2008年 | 685篇 |
2007年 | 636篇 |
2006年 | 448篇 |
2005年 | 412篇 |
2004年 | 322篇 |
2003年 | 282篇 |
2002年 | 225篇 |
2001年 | 158篇 |
2000年 | 151篇 |
1999年 | 139篇 |
1998年 | 123篇 |
1997年 | 115篇 |
1996年 | 120篇 |
1995年 | 110篇 |
1994年 | 91篇 |
1993年 | 89篇 |
1992年 | 101篇 |
1991年 | 75篇 |
1990年 | 85篇 |
1989年 | 77篇 |
1988年 | 75篇 |
1987年 | 43篇 |
1986年 | 52篇 |
1985年 | 68篇 |
1984年 | 62篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 37篇 |
1980年 | 35篇 |
1979年 | 29篇 |
1978年 | 18篇 |
1977年 | 23篇 |
1976年 | 12篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
William J. Turner M. D. 《Archives of sexual behavior》1995,24(2):109-134
Despite the absence of phenotypic manifestations in alternating generations characteristic of X-linked disorders, a thesis is presented that a major type of Kinsey grades 5 and 6 male homosexuality is determined by a gene in the Xq28 region. A total of 133 families in 78 kinships of male and female homosexual probands, in addition to 116 families (including those of 40 famous homosexuals) from the literature, revealed an unbalanced secondary sex ratio in the maternal generation of male, but not of female, homosexuals. On the maternal side, in this study, the ratio of all uncles to all aunts of 90 males homosexuals was 132/209, 2 = 8.52, p = 0.004. On the maternal side for the total of all sources, the ratio of uncles to aunts of male homosexuals was 241/367, 2 = 13.20; p < 0.0001. The male/female ratio of the total number of maternal sibships bearing homosexuals (310/628: 0.491) was a measure of fetal wastage of the mothers' male sibs: 49%. This ratio was very close to that of the total number of children born to fathers affected with any one of nine Xq28-linked male semilethal conditions (255/508: ratio 0.556); for the difference between the two populations 2 = 0.859, p = 0.354. The male/female ratio of the total number of children born to female carriers of any one of these same conditions (1,232/1,062: ratio 1.16), 2 = 13.8 p 0.0001, is close to that of the total number of children in homosexual sibships: 511/413, 2 = 10.4, p = 0.005. Between the number of children born to Xq28 mothers and to those born of mothers of homosexuals 2 = 0.581, p = 0.446. One may readily surmise that the maternal influence so often related to homosexuality may lie in the mother being a genetic carrier, with traits thereto associated. In this study, 65% of the mothers of homosexuals had no or only one live-born brother. Additional support for a genetic hypothesis is found in the occurrence of multiple instances—almost exclusively among maternal relatives—of infertility, spontaneous abortions, miscarriages, stillbirths, remaining single past age 30, and suicide. Of 109 male and 43 female homosexual index cases in the present series there were 6 instances of brother/sister homosexual sibships. Instances of homosexual parent-to-homosexual child transmission occurred as follows: one father-to-son; one father-to-daughter; one bisexual father-son; one father/mother-to-2 sons; one of mother-to-son, and one of father-to-son and father-to-bisexual daughter. There were 16 instances of presumptive transmissions from heterosexual father-to-homosexual son and 5 of heterosexual father-to-homosexual daughter. A hypothesis is proposed: Homosexuality is due to a gene at Xq28 characterized by (i) elongated cytosine-containing trinucleotide repeats upstream to translation of a gene, (ii) elongated CpG islands upstream of the trinucleotides, and (iii) cytosine methylation of CpG islands and of the cytosine-containing trinucleotides.A limited number of long tables of data, and pedigree charts, which provide the details from which this paper was developed, may be obtained on paper or on disc from the author or, for a modest fee, from the Librarian, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, New York 11794. 相似文献
33.
BACKGROUND: Nitric oxide [NOexp] is present in exhaled air in many species. During experiments on pressure-controlled inverse ratio ventilation (PCIRV) in rabbits, increased [NOexp] was observed during PCIRV. The present study was undertaken to clarify which component of PCIRV increased [NOexp]. METHODS: Three groups of six New Zealand White rabbits were anaesthetised and mechanically ventilated. Exhaled nitric oxide, lung mechanics and gas exchange were measured using an experimental protocol designed to assess the effects of variations in 1) flow profile, 2) inspiratory time and 3) time-weighted tidal volume. Ventilator settings used were volume and pressure control ventilation at I:E ratios of 1:2 and 4:1. RESULTS: Constant and decelerating flow gave comparable [NOexp] levels (20.0 +/- 6.4 vs. 21.9 +/- 7.7 ppb, n.s.) when time-weighted tidal volume was kept constant. Using conventional (I:E 1:2) or inverted (I:E 4:1) I:E ratios in combination with decelerating flow and constant time-weighted tidal volumes did not alter [NOexp] (26.0 +/- 3.6 vs. 24.0 +/- 5.8 ppb, n.s.). An increased time-weighted tidal volume produced by pressure control with an I:E ratio of 4:1 increased [NOexp] (29.6 +/- 7.4) in comparison to constant (19.3 +/- 4.1, P < 0.05) and decelerating flow ventilation (19.6 +/- 3.6, P < 0.05) with I:E ratios of 1:2. CONCLUSION: The exhaled NO concentration was affected by ventilator setting. Increased levels of [NOexp] were observed with increases in time-weighted tidal volume, whereas changes in flow pattern and inspiratory time did not seem to influence airway NO production or release. 相似文献
34.
Kudo T Kawase M Kawada S Kurosawa H Koyanagi H Takeuchi Y Hosoda Y Wanibuchi Y 《Artificial organs》1999,23(2):199-203
Anticoagulant therapy after cardiac valve replacement was evaluated retrospectively in 1,200 patients attending 8 cardiac surgery clinics in the Tokyo area as part of the Tokyo Area Study on Anticoagulation After Cardiac Valve Replacement Using PT-INR (TAS). A prospective trial is also in progress and will be reported later. The prothrombin time international normalized ratio (PT-INR) was determined at the time of thromboembolic and bleeding complications in 1,200 patients. During the 5 year study period, thromboembolisms occurred in 21 patients, and bleeding complications occurred in 15 patients. In 71% of patients with thromboembolism and 47% of those with bleeding complications, the PT-INR was within the range of 1.6 to 2.8, which is the accepted therapeutic range in Japan. Therefore, the correct PT-INR therapeutic range for Japanese patients with mechanical heart valves needs to be reexamined, and data from the prospective TAS trial that is currently underway will be used for this purpose. 相似文献
35.
M Ishizaki Y Yamada Y Morikawa Y Noborisaka M Ishida K Miura H Nakagawa 《Occupational medicine (Oxford, England)》1999,49(3):177-182
As a marker of body fat distribution and therefore level of obesity, the waist-to-hip ratio (W:H) is a good indicator of coronary heart disease risk status. The present study investigated the association between occupational status and life-style factors, and W:H of middle-aged Japanese male (n = 2,550) and female (n = 1,283) workers in a metal-products factory. A higher W:H was observed in the management level males as compared with the other male workers and we suggest this was promoted by the sedentary aspect of their work, as well as their higher levels of alcohol consumption and lower levels of leisure-time physical activity. In contrast, a higher W:H was recorded in female labourers, whose work was typically less sedentary as compared with female managers. Life-style factors included in the study were not related to this observation. We conclude that other unmeasured psychosocial factors may be important in promoting higher W:H in female labourers. 相似文献
36.
目的;观察三级肝硬化患者血浆中支链氨基酸与芳香氨基酸数值的变化情况。方法:使用氨基酸分析仪检测三级肝硬化患者氨基酸数值。结果:随肝病加重,支/芳比值逐渐减低,各组间的差异具有显著性。结论:支/芳比值可作为了解肝硬化病情严重程度和判断预后的指标。 相似文献
37.
The a- and b-wave latencies as a prognostic indicator of neovascularisation in central retinal vein occlusion 总被引:1,自引:0,他引:1
Moschos M Brouzas D Moschou M Theodossiadis G 《Documenta ophthalmologica. Advances in ophthalmology》1999,99(2):123-133
To evaluate the prognostic value of ERG in cases of central retinal vein occlusion (CRVO) regarding the development of neovascularisation
(NV), we studied 20 patients with unilateral CRVO. Half of them were allocated in the perfused group and the other 10 finally
developed NV and were allocated in the non-perfused group. Flash ERG was recorded from all patients. Our findings suggest
that b-wave latency is the most reliable parameter in predicting NV, followed by the a-wave latency. The b/a wave amplitude of ERG ratio does not seem to be suitable for clinical use.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
Suppose that part of the prosecution's evidence in some crime case is analysis of a blood stain, and that the traits E discovered in the stain suggest multiple donors. Then the prosecution will probably allege some specific inculpatory hypothesis H0 about the sources of the stain, and P {E | H0} can be calculated. It is desirable to use this as the numerator of a likelihood ratio. However, in general the obvious denominator P {E | H0} cannot be calculated, so unless the defense is sufficiently obliging as to stipulate to a specific choice among the potentially infinite number of more or less exculpatory alternative hypotheses, the desired likelihood ratio can't be evaluated. We show that nonetheless, in most cases there is an adequate inequality. 相似文献
39.
Cocaine, diethylpropion, chlorphentermine, and fenfluramine were compared on a drug-maintained progressive-ratio procedure in baboons. Intravenous infusions of drug were contingent on completion of a fixed-ratio response requirement (fixed number of lever-press responses) with a 3-h time-out period following each infusion. Prior to testing each dose of drug, stable self-infusion performance was first established with 0.4 mg/kg cocaine when the fixed-ratio requirement was 160. Subsequently, a test dose of drug was substituted for the standard dose of cocaine. If the dose of drug maintained a criterion level of self-infusion performance (six or more infusions per day for 2 days), the ratio requirement was systematically increased every day until the breaking point at which the self-infusion performance fell below a criterion level (one or zero infusionsper day). Fenfluramine did not maintain criterion self-infusion performance at any dose tested (0.02–5.0 mg/kg). The dose ranges of the other drugs that maintained maximum breaking points were 1.0–5.6 mg/kg for chlorphentermine, 1.0–3.0 mg/kg for diethylpropion, and 0.1–0.4 mg/kg for cocaine. Within-animal comparison of the maximum breaking points indicated that cocaine maintained the highest breaking points, followed in order by diethylpropion, chlorphentermine, and fenfluramine. The rank ordering of these drugs with the breaking point measure corresponds well with both the results of other animal experiments on measurement of reinforcing efficacy of these drugs and with the clinical information about the human subjective effects and abuse of these drugs. 相似文献
40.