全文获取类型
收费全文 | 40025篇 |
免费 | 3318篇 |
国内免费 | 165篇 |
专业分类
耳鼻咽喉 | 639篇 |
儿科学 | 956篇 |
妇产科学 | 692篇 |
基础医学 | 4917篇 |
口腔科学 | 912篇 |
临床医学 | 3890篇 |
内科学 | 9028篇 |
皮肤病学 | 472篇 |
神经病学 | 3309篇 |
特种医学 | 1328篇 |
外科学 | 6677篇 |
综合类 | 746篇 |
一般理论 | 25篇 |
预防医学 | 3120篇 |
眼科学 | 1031篇 |
药学 | 2888篇 |
中国医学 | 127篇 |
肿瘤学 | 2751篇 |
出版年
2023年 | 204篇 |
2022年 | 410篇 |
2021年 | 916篇 |
2020年 | 514篇 |
2019年 | 806篇 |
2018年 | 931篇 |
2017年 | 727篇 |
2016年 | 722篇 |
2015年 | 800篇 |
2014年 | 1259篇 |
2013年 | 1755篇 |
2012年 | 2613篇 |
2011年 | 2602篇 |
2010年 | 1440篇 |
2009年 | 1369篇 |
2008年 | 2368篇 |
2007年 | 2519篇 |
2006年 | 2638篇 |
2005年 | 2627篇 |
2004年 | 2412篇 |
2003年 | 2447篇 |
2002年 | 2275篇 |
2001年 | 549篇 |
2000年 | 538篇 |
1999年 | 581篇 |
1998年 | 561篇 |
1997年 | 448篇 |
1996年 | 407篇 |
1995年 | 325篇 |
1994年 | 295篇 |
1993年 | 254篇 |
1992年 | 349篇 |
1991年 | 314篇 |
1990年 | 310篇 |
1989年 | 272篇 |
1988年 | 244篇 |
1987年 | 225篇 |
1986年 | 225篇 |
1985年 | 217篇 |
1984年 | 248篇 |
1983年 | 201篇 |
1982年 | 220篇 |
1981年 | 209篇 |
1980年 | 163篇 |
1979年 | 152篇 |
1978年 | 160篇 |
1977年 | 143篇 |
1976年 | 111篇 |
1974年 | 125篇 |
1973年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Estrogen receptor beta polymorphisms are associated with bone mass in women and men: the Framingham Study. 总被引:5,自引:0,他引:5
Amanda M Shearman David Karasik Kristen M Gruenthal Serkalem Demissie L Adrienne Cupples David E Housman Douglas P Kiel 《Journal of bone and mineral research》2004,19(5):773-781
ESR2 is expressed in bone cells, yet few studies have tested its variation for association with BMD, an important determinant of osteoporotic fractures. This was investigated in 723 men and 795 women from the Framingham study. Results show association of variation in this gene with BMD in both women and men. INTRODUCTION: Osteoporotic fracture risk is highly dependent on bone density, a quantitative multifactorial trait with a substantial genetic component. In contrast to the growing body of evidence that estrogen receptor alpha (ESR1) plays a role in bone metabolism, few studies have examined the estrogen receptor beta (ESR2) gene for association with BMD. An ESR2 CA repeat polymorphism, D14S1026, was associated with BMD in two small studies, each with <200 women. MATERIALS AND METHODS: The objective of this investigation was to assess whether D14S1026 or four other intronic polymorphisms were associated with BMD in 723 men and 795 women (mean age, 60 years) from the offspring cohort of the population-based Framingham Study. BMD was measured at the femur (neck, trochanter, and Ward's area) and the lumbar spine (L(2)-L(4)). RESULTS: In both women and men, there was significant association of D14S1026 genotype with measures of femoral but not spinal BMD. In addition, genotypes of two common single nucleotide polymorphisms, rs1256031 and rs1256059, in strong linkage disequilibrium with one another but not with D14S1026, were associated with measures of femoral BMD in men. The rs1256031 genotypes had up to a 4.0% difference in mean femoral BMD. An inferred rs1256031-D14S1026-rs1256059 haplotype C-23CA-T was significantly associated with reduced femoral BMD in women (p = 0.03, 0.003, and 0.01 for neck, trochanter, and Ward's area, respectively). Haplotype-based BMD differences ranged from 3.0% to 4.3%. CONCLUSIONS: We have observed significant association of common ESR2 variants with measures of femoral BMD in both men and women. 相似文献
52.
53.
54.
55.
John S. Witte Giske Ursin Jack Siemiatycki W. Douglas Thompson Annali Paganini-Hill Robert W. Haile 《Breast cancer research and treatment》1997,42(3):243-251
We investigated associations between diet and premenopausal bilateral breast cancer in a familial matched case-control study. We studied 140 cases from population-based registries in Los Angeles County (California) and Connecticut, and from the major hospitals in the southern parts of the Province of Quebec. Unaffected sisters of the cases served as matched controls (222 total). Dietary intake were assessed with a food frequency questionnaire. Total fat, monounsaturated fat, polyunsaturated fat, oleic acid, and linoleic acid intake was inversely associated with premenopausal bilateral breast cancer risk. Consumption of carbohydrates (and sweetened beverages) was associated with an increased risk. We observed no associations for dietary fiber, antioxidants, or major food groupings, but we did observe inverse associations for intake of low fat dairy products and tofu. These findings suggest that monounsaturated and polyunsaturated fats, as well as soy foods, might reduce the risk of premenopausal bilateral breast cancer. 相似文献
56.
57.
A J Waring C M Housworth R M Voorhies J R Douglas C F Walker S E Connolly 《Surgical neurology》1990,34(3):139-143
The authors have developed and patented a neurosurgical retractor system incorporating an infrared emitter and detector that allows detection of cerebral pulsations. Gentle contact with the surface of cat brains shows cerebral pulsations that correlate with arterial pulse as well as mechanical ventilation. The amplitude of cerebral pulsations decreases with higher retraction pressure and disappears at approximately 20 mmHg. The pressure on the surface of the brain decreased 50% in 5 minutes even though the position of the retractor was maintained constant. The authors postulate that monitoring cerebral pulsation may prove useful in clinical neurosurgery with respect to avoiding excessive retraction, which causes brain damage. 相似文献
58.
We report a case of Fusarium solani keratitis which highlights the difficulties often associated with management of fungal corneal infections. This case demonstrates several unusual and interesting features: the occurrence of deep fungal pathology after superficial injury, the difficulties encountered in attempting to isolate and identify the causative organism, and the protracted course taken by an organism often noted to be rapidly destructive. These features necessitated an individual approach to therapy, employing unconventional medical and surgical techniques to achieve a satisfactory outcome 相似文献
59.
Lisa Garnsey Ensign Edmund A. Gehan Douglas S. Kamen Peter F. Thall 《Statistics in medicine》1994,13(17):1727-1736
A phase II clinical trial in cancer therapeutics is usually a single-arm study to determine whether an experimental treatment (E) holds sufficient promise to warrant further testing. When the criterion of treatment efficacy is a binary endpoint (response/no response) with probability of response p, we propose a three-stage optimal design for testing H0: p ≤ p0 versus H1: p ≥ p1, where p1 and p0 are response rates such that E does or does not merit further testing at given levels of statistical significance (α) and power (1 ? β). The proposed design is essentially a combination of earlier proposals by Gehan and Simon. The design stops with rejection of H1 at stage 1 when there is an initial moderately long run of consecutive treatment failures; otherwise there is continuation to stage 2 and (possibly) stage 3 which have decision rules analogous to those in stages 1 and 2 of Simon's design. Thus, rejection of H1 is possible at any stage, but acceptance only at the final stage. The design is optimal in the sense that expected sample size is minimized when p = p0, subject to the practical constraint that the minimum stage 1 sample size is at least 5. The proposed design has greatest utility when the true response rate of E is small, it is desirable to stop early if there is a moderately long run of early treatment failures, and it is practical to implement a three-stage design. Compared to Simon's optimal two-stage design, the optimal three-stage design has the following features: stage 1 is the same size or smaller and has the possibility of stopping earlier when 0 successes are observed; the expected sample size under the null hypothesis is smaller; stages 1 and 2 generally have more patients than stage 1 of the two-stage design, but a higher probability of early termination under H0; and the total sample size and criteria for rejection of H1 at stage 3 are similar to the corresponding values at the end of stage 2 in the two-stage optimal design. 相似文献
60.
Pantin Hilda Coatsworth J. Douglas Feaster Daniel J. Newman Frederick L. Briones Ervin Prado Guillermo Schwartz Seth J. Szapocznik José 《Prevention science》2003,4(3):189-201
This paper reports a test of the efficacy of Familias Unidas, a Hispanic-specific, ecologically focused, parent-centered preventive intervention, in promoting protection against and reducing risk for adolescent behavior problems. Specifically, the intervention was designed to foster parental investment, reduce adolescent behavior problems, and promote adolescent school bonding/academic achievement, all protective factors against drug abuse and delinquency. One-hundred sixty seven Hispanic families of 6th and 7th grade students from three South Florida public schools were stratified by grade within school and randomly assigned to intervention and no-intervention control conditions. Results indicated that Familias Unidas was efficacious in increasing parental investment and decreasing adolescent behavior problems, but that it did not significantly impact adolescent school bonding/academic achievement. Summer-vacation rates of adolescent behavior problems were six times higher in the control condition than in the intervention condition. Furthermore, change in parental investment during the intervention was predictive of subsequent levels of adolescent behavior problems. The findings suggest that Familias Unidas is efficacious in promoting protection and reducing risk for adolescent problem behaviors in poor immigrant Hispanic families. 相似文献