全文获取类型
收费全文 | 9354篇 |
免费 | 733篇 |
国内免费 | 90篇 |
专业分类
耳鼻咽喉 | 91篇 |
儿科学 | 348篇 |
妇产科学 | 322篇 |
基础医学 | 1279篇 |
口腔科学 | 86篇 |
临床医学 | 822篇 |
内科学 | 2383篇 |
皮肤病学 | 69篇 |
神经病学 | 470篇 |
特种医学 | 213篇 |
外科学 | 1601篇 |
综合类 | 251篇 |
一般理论 | 2篇 |
预防医学 | 620篇 |
眼科学 | 108篇 |
药学 | 710篇 |
中国医学 | 88篇 |
肿瘤学 | 714篇 |
出版年
2023年 | 62篇 |
2022年 | 74篇 |
2021年 | 201篇 |
2020年 | 131篇 |
2019年 | 195篇 |
2018年 | 253篇 |
2017年 | 177篇 |
2016年 | 192篇 |
2015年 | 231篇 |
2014年 | 302篇 |
2013年 | 351篇 |
2012年 | 543篇 |
2011年 | 586篇 |
2010年 | 330篇 |
2009年 | 311篇 |
2008年 | 472篇 |
2007年 | 551篇 |
2006年 | 506篇 |
2005年 | 498篇 |
2004年 | 474篇 |
2003年 | 392篇 |
2002年 | 364篇 |
2001年 | 367篇 |
2000年 | 329篇 |
1999年 | 298篇 |
1998年 | 101篇 |
1997年 | 139篇 |
1996年 | 107篇 |
1995年 | 86篇 |
1994年 | 74篇 |
1993年 | 37篇 |
1992年 | 165篇 |
1991年 | 141篇 |
1990年 | 130篇 |
1989年 | 111篇 |
1988年 | 110篇 |
1987年 | 105篇 |
1986年 | 90篇 |
1985年 | 59篇 |
1984年 | 48篇 |
1983年 | 58篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1979年 | 65篇 |
1978年 | 29篇 |
1977年 | 29篇 |
1976年 | 27篇 |
1974年 | 27篇 |
1973年 | 31篇 |
1972年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
To examine the prevalence of Internet sex networking among men who have sex with men (MSM) in Hong Kong and risk behaviors associated with the behavior, a telephone survey of 15,230 Hong Kong Chinese men aged 18-60 was conducted. Of the 283 active MSM (having engaged in some MSM behaviors in the last 6 months) identified, 17.7% had networked for MSM partners via the Internet in the last 6 months. Younger age (odds ratio [OR] for age < or = 25 vs. age >25 = 4.67, 95% confidence interval [CI] = 2.35-9.28) and being an anal-sex MSM (OR = 4.72, 95% CI=2.36-9.44) were independent predictors of Internet sex networking. Being an Internet sex networker was associated with some risk behaviors such as having contracted a sexually transmitted disease (adjusted OR = 4.79, 95% CI = 1.34-17.11), having had > or = 3 MSM partners (adjusted OR = 4.74, 95% CI = 2.20-10.23), and having engaged in anal sex (adjusted OR = 3.95, 95% CI = 1.89-8.23). HIV prevention programs for MSM should thereby include Internet-based interventions. 相似文献
3.
Monolayer cultures of normal human bone cells contain multiple subpopulations of alkaline phosphatase positive cells 总被引:5,自引:0,他引:5
Toshikatsu Matsuyama K. -H. William Lau Jon E. Wergedal 《Calcified tissue international》1990,47(5):276-283
Summary Cytochemical staining of normal human bone cells in monolayer cultures for alkaline phosphatase (ALP) indicated that the cultures
contained mixed-cell populations. Time course evaluations of the cytochemical staining revealed, in addition to the ALP-negative
cell population, at least two subpopulations of ALP-positive human bone cells with different levels of ALP. A cytochemical
method has been developed which separates the ALP-positive cells into high and intermediate ALP subpopulations. In this method,
human bone cells were stained for ALP using an azo-dye method and incubating at 4°C for 10 and 30 minutes, respectively. We
defined the cell population that stained positively for ALP at 10 minutes as strong ALP-positive cells, and both strong and
intermediate cells were stained at 30 minutes. The intermediate cells were determined from the difference between the values
at the two time points. The intra- and interassay variations of the assay, with the same investigator in blinded investigations,
were both less than 10% and the interobserver variation was approximately 25%. Analysis of the distribution of ALP levels
in cells with a laser densitometer confirmed the presence of at least three cell subpopulations. 1,25(OH)2D3 treatment increased the proportions of both ALP-positive cell populations, whereas TGF-beta treatment increased only the
intermediate ALP-positive cell population. On the contrary, fluoride increased the proportion of the strong ALP cells, and
IGF-1 had no effect on the proportions of either ALP-positive subpopulation. When the ALP-specific activity was compared with
the percentage of each ALP-positive subpopulations for the cells treated with effectors, the ALP-specific activity correlated
with the total ALP-positive and with the strong ALP-positive populations but not with the intermediate ALP-positive subpopulation.
In summary, this study represents the first evidence that normal human bone cells in monolayer cultures contained at least
two subpopulations of ALP-positive cells, and that bone cell effectors could have differential effects on each cell population. 相似文献
4.
OBJECTIVE: Cancer Care Ontario has recommended a population-based colorectal cancer (CRC) screening program using fecal occult blood testing. Patients who test positive should undergo further investigation, preferably colonoscopy. So far, no studies have been performed to quantify the costs or demands on the health care system at the community level. The number of consultations, colonoscopies and polypectomies, and the corresponding direct medical costs generated by the CRC screening program, between 2006 and 2015 in London, Ontario, were estimated using a decision analysis model in comparison with the population health model. METHODS: A faxed survey study was conducted to examine the current CRC screening practice among family physicians in London. Data from the survey and randomized studies were applied to a decision analysis model, which simulated the steps involved in population-based biennial and annual CRC screening between 2006 and 2015. The number of consultations, colonoscopies and polypectomies, and their associated costs were calculated. RESULTS: For a cohort population of 140,000, between 50 and 74 years of age, in 2006 to 2015, it is estimated that an average of 412 consultations, 463 colonoscopies and 174 polypectomies will be performed per 100,000 screen eligible population per year in biennial screening, and double in annual screening, reflecting an average of 8.7% or 17.6% increase annually in outpatient colonoscopies, respectively, compared with 2003. A mean of $285,000 or $562,000 per year would be required to support the extra consultation and endoscopic procedures generated by the biennial or annual screening. CONCLUSION: Population-based fecal occult blood testing screening for CRC appears to be a manageable strategy if a modest increase in endoscopic resources is allocated. 相似文献
5.
6.
Rats were exposed to daily 3-hr schedule-induced polydipsia sessions (fixed-time 1-min food-pellet delivery) with two drinking fluids available: cocaine solution and water. Fluid position was alternated daily. Polydipsia occurred mostly from a preferred-side spout (position preference) until cocaine solution concentration was increased to between 0.52 and 1.04 mg/ml and animals drank mostly water. Within a lower concentration range (0.28-0.6 mg/ml) maximum session cocaine intakes ranged from 54.3 to 120.1 mg/kg. Postsession serum cocaine levels were about 200 ng/ml. At individually chosen cocaine solution concentrations, the addition of saccharin to the solution did not increase cocaine intake, but a compound solution (saccharin plus glucose) did. With progressive dilution of the compound vehicle, an almost complete preference for cocaine solution was maintained. But with a return to water as the vehicle, animals reverted to a position preference after a few sessions, although one maintained a clear cocaine preference. Schedule-induced polydipsia produced chronic, oral self-administration of cocaine resulting in pharmacologically significant intakes and serum levels. 相似文献
7.
Efficacy of radical neck dissection for the control of cervical metastasis after radiotherapy for nasopharyngeal carcinoma 总被引:5,自引:0,他引:5
Fifty-one patients who had persistent or recurrent neck disease from nasopharyngeal carcinoma after radiotherapy underwent radical neck dissection. The follow-up period ranged from 0.5 to 9 years (median: 2 years). Multiple cervical lymph node involvement was present in 51% of the patients (26 of 51). Malignant cells were detected in 88% of the resected specimens (45 of 51). The clinical sign of fixation of lymph node is the only factor that affects the successful control of neck disease (p = 0.04). Extracapsular extension of the nodal disease was present, and 35% of the lymph nodes were adherent to surrounding structures at operation (18 of 51). There was one hospital mortality and the overall morbidity was minimal. The actuarial survival at 5 years was 38%, and the probability of control of neck disease was 66%. Radical neck dissection is effective in controlling post-irradiation cervical metastasis from nasopharyngeal carcinoma. 相似文献
8.
Benjamin H. S. Lau Sharon K. Riesen Kim P. Truong Esther W. Lau Peter Rohdewald Ray A. Barreta 《The Journal of asthma》2004,41(8):825-832
A randomized, placebo-controlled, double-blind study involving 60 subjects, aged 6-18 years old, was conducted over a period of 3 months to determine the effect of Pycnogenol® (a proprietary mixture of water-soluble bioflavonoids extracted from French maritime pine) on mild-to-moderate asthma. After baseline evaluation, subjects were randomized into two groups to receive either Pycnogenol® or placebo. Subjects were instructed to record their peak expiratory flow with an Assess® Peak Flow Meter each evening. At the same time, symptoms, daily use of rescue inhalers (albuterol), and any changes in oral medications were also recorded. Urine samples were obtained from the subjects at the end of the run-in period, and at 1-, 2-, and 3-month visits. Urinary leukotriene C4/D4/E4 was measured by an enzyme immunoassay. Compared with subjects taking placebo, the group who took Pycnogenol® had significantly more improvement in pulmonary functions and asthma symptoms. The Pycnogenol® group was able to reduce or discontinue their use of rescue inhalers more often than the placebo group. There was also a significant reduction of urinary leukotrienes in the Pycnogenol® group. The results of this study demonstrate the efficacy of Pycnogenol® as an adjunct in the management of mild-to-moderate childhood asthma. 相似文献
9.
10.