全文获取类型
收费全文 | 20456篇 |
免费 | 2170篇 |
国内免费 | 54篇 |
专业分类
耳鼻咽喉 | 170篇 |
儿科学 | 664篇 |
妇产科学 | 524篇 |
基础医学 | 2779篇 |
口腔科学 | 450篇 |
临床医学 | 2271篇 |
内科学 | 4108篇 |
皮肤病学 | 234篇 |
神经病学 | 2070篇 |
特种医学 | 879篇 |
外科学 | 3006篇 |
综合类 | 399篇 |
一般理论 | 14篇 |
预防医学 | 1938篇 |
眼科学 | 318篇 |
药学 | 1231篇 |
中国医学 | 7篇 |
肿瘤学 | 1618篇 |
出版年
2021年 | 275篇 |
2020年 | 179篇 |
2019年 | 276篇 |
2018年 | 344篇 |
2017年 | 281篇 |
2016年 | 303篇 |
2015年 | 337篇 |
2014年 | 463篇 |
2013年 | 770篇 |
2012年 | 902篇 |
2011年 | 959篇 |
2010年 | 569篇 |
2009年 | 638篇 |
2008年 | 843篇 |
2007年 | 914篇 |
2006年 | 884篇 |
2005年 | 934篇 |
2004年 | 869篇 |
2003年 | 799篇 |
2002年 | 781篇 |
2001年 | 638篇 |
2000年 | 656篇 |
1999年 | 621篇 |
1998年 | 348篇 |
1997年 | 299篇 |
1996年 | 317篇 |
1995年 | 247篇 |
1994年 | 269篇 |
1993年 | 220篇 |
1992年 | 443篇 |
1991年 | 440篇 |
1990年 | 421篇 |
1989年 | 457篇 |
1988年 | 370篇 |
1987年 | 375篇 |
1986年 | 363篇 |
1985年 | 332篇 |
1984年 | 264篇 |
1983年 | 215篇 |
1982年 | 185篇 |
1981年 | 159篇 |
1980年 | 143篇 |
1979年 | 216篇 |
1978年 | 180篇 |
1977年 | 149篇 |
1976年 | 150篇 |
1974年 | 176篇 |
1973年 | 140篇 |
1972年 | 152篇 |
1971年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Two colorectal (HT29, LoVo) and one gastric (MKN45) human tumour cell lines were examined for their in vitro trophic response to human gastrin-17. MKN45 and HT29 responded by increased 75Se selenomethionine uptake to exogenous gastrin (139 +/- 5.5% and 123 +/- 3% of control values respectively) whereas LoVo showed no significant response to this hormone. When these same cell lines were grown as xenografts in nude mice, similar responses were seen to exogenously administered human gastrin-17 (10 micrograms mouse-1 day-1, subcutaneous injection). MKN45 xenografts showed a greater response to continuously administered gastrin (osmotic mini-pumps, (10 micrograms mouse-1 day-1) when compared to the same dose given via a subcutaneous bolus injection. The hormone-treated xenografts had a two-fold increase in tumour cross-sectional area and growth rate when compared to saline-treated controls. Dose-response studies revealed that 0.4 micrograms gastrin mouse-1 day-1 appeared to be the minimally effective dose. As gastric and colorectal tumour cells show a trophic response to gastrin, antagonists of the gastrin receptor may prevent this effect causing tumour stasis. The gastric tumour cell line, MKN45, is gastrin-responsive and would be an ideal model for screening potent receptor antagonists. 相似文献
72.
DQ beta restriction fragment patterns have been obtained from five DRw8 cell lines homozygous for the null DQ allele, DQWa. The enzymes Bgl II, Bam HI and Pvu II generate DQ beta patterns which are indistinguishable from those obtained from cell lines homozygous for DQw3.2. 相似文献
73.
AIMS: To determine if leucocyte volume distribution analysis (LVDA), obtained using a Coulter Counter Model S Plus IV, can be used to aid differentiation of chronic lymphoproliferative disorder (CLPD) subtypes. METHODS: Mean lymphocyte volume and lymphocyte distribution width were measured on each patient (n = 90) using a hard copy of an amplified LVDA histogram. The mean lymphocyte volume was taken as the mean of the values on either side of the peak at half maximum height. The lymphocyte distribution width was taken as the range of cell values between the two values used to calibrate the mean lymphocyte volume. A template showing typical histograms from commonly occurring CLPD was also produced on an acetate sheet. This was used to examine the histogram from each new patient to evaluate its usefulness as an alternative to the calculation of mean lymphocyte volume and lymphocyte distribution width. RESULTS: Mean lymphocyte volume and lymphocyte distribution width were significantly higher in B cell lymphocytic leukaemia of mixed cell type (B CLL/PL), B cell non-Hodgkin's lymphoma with peripheral blood spill, hairy cell leukaemia and T cell prolymphocytic leukaemia than in B cell chronic lymphocytic leukaemia (B CLL). The mean lymphocyte volume, but not the lymphocyte distribution width, was also significantly higher in T cell chronic lymphocytic leukaemia than in B CLL. The template gave an immediate preliminary indication of possible subtype(s) of disorder and could be used as an alternative to measurement of mean lymphocyte volume and lymphocyte distribution width. CONCLUSIONS: Electronic haematology analysers producing an LVDA provide a useful, cost effective cell sizing analysis which can aid the differentiation of subtypes of CLPD. 相似文献
74.
Rosenberg ZS; Jahss MH; Noto AM; Shereff MJ; Cheung Y; Frey CC; Norman A 《Radiology》1988,167(2):489-493
Computed tomography (CT) was performed in 42 patients with 49 clinically suspected tears of the posterior tibial tendon. Twenty-eight of the 49 suspected tears were subsequently surgically explored and repaired. Three patterns of tendon abnormalities were recognized on CT scans: type I-intact, hypertrophied, heterogeneous tendon; type II-attenuated tendon; and type III-absence of a portion of a tendon. Types I and II correlated with partial rupture seen during surgery, and type III correlated with complete rupture of the tendon. CT findings were accurate in 96% of the patients who underwent surgery. In four cases (14%), tendon rupture was seen on CT scans, but the extent of the injury was underestimated and the rupture was misclassified. Reactive periostitis of the distal tibia was seen in 71% of diseased tendons and may represent an important factor in the diagnosis of tendon rupture. 相似文献
75.
Cortical potentials related to voluntary and passive finger movements recorded from subdural electrodes in humans 总被引:2,自引:0,他引:2
Movement-related potentials were recorded from subdural electrodes placed on the precentral and postcentral cortex in 3 patients undergoing operation for intractable epilepsy. With self-initiated index finger movement, a negative potential of 25 to 50 microvolts in amplitude, preceding onset of the electromyographic activity by 60 to 95 ms (or onset of movement by 150 to 230 ms), was recorded from the hand somatosensory postrolandic area in all 3 patients. A similar potential preceding the movement was recorded from the precentral hand motor area in one subject who was the only patient in whom the precentral electrodes were placed on the hand motor area. Following active and passive movements, a clearly defined positivity (18 to 32 ms after a photometer trigger) that reversed phase across the central fissure was recorded. The premovement potentials are most probably generated by pyramidal tract neurons and motor-function-related neurons located in the post- and prerolandic areas. The postmovement positivity is most probably due to short-latency kinesthetic reafferent activation of the posterior bank of the central fissure (equivalent to P2 of the somatosensory evoked potentials). 相似文献
76.
L Morris 《Morbidity and mortality weekly report. Surveillance summaries (Washington, D.C. : 2002)》1992,41(4):27-40
Although a formal public health surveillance system has not yet been established in Latin America to document the attitudes of young people toward sex education, sexual activity, and contraception and their behaviors in these areas, representative data are available from 12 household-based Young Adult Reproductive Health Surveys conducted in seven countries since 1985. The surveys indicate that the rate of sexual experience before marriage or consensual union for males is much higher than that for females, and first sexual experience occurs at a younger age for males than for females. However, from 34% to 90% of females 20-24 years of age report having had premarital sexual relations. No more than 41% of females and 31% of males report that they or their partner used contraception at first sexual experience. Less than one-third of both young men and young women could identify the most fertile period during the menstrual cycle. The results of such surveys have provided program officials and policymakers with data to plan, implement, and evaluate interventions targeted for young adults. 相似文献
77.
Blinded clinical evaluation of positron emission tomography for diagnosis of probable Alzheimer's disease. 总被引:5,自引:0,他引:5
W J Powers J S Perlmutter T O Videen P Herscovitch L K Griffeth H D Royal B A Siegel J C Morris L Berg 《Neurology》1992,42(4):765-770
We evaluated the sensitivity and specificity of positron emission tomography for diagnosis of probable Alzheimer's disease under conditions similar to those encountered in the routine clinical practice of nuclear medicine. We obtained tomographic images of regional cerebral blood flow from three groups of subjects: (1) 13 subjects, ages 69 to 84, who had probable Alzheimer's disease diagnosed by validated clinical criteria; (2) 15 subjects, ages 57 to 77, who had Parkinson's disease without dementia; and (3) 11 subjects, ages 65 to 83, who were normal. Three blinded reviewers, who had not previously seen the images, categorized them as normal, bilateral temporoparietal flow defects typical of Alzheimer's disease, or other abnormality. Consensus interpretation demonstrated sensitivity of 0.38 (5/13) and specificity of 0.88 (23/26) for identifying patients with probable Alzheimer's disease. Thus, the criterion of bilateral temporoparietal reduction in cerebral blood flow used in this study did not have sufficient sensitivity to be of clinical value. While other criteria may be developed to improve diagnostic accuracy, clinical utility can be established only by testing for validity in patients with a full spectrum of complicating neurologic and psychiatric conditions for whom diagnosis is uncertain and who are then followed longitudinally to determine clinical outcome or pathologic findings. 相似文献
78.
Physical activity and quality of life in older adults: Influence of health status and self-efficacy 总被引:2,自引:1,他引:1
Edward McAuley Ph.D. James F. Konopack Ed.M. Robert W. Motl Ph.D. Katherine S. Morris B.A. Shawna E. Doerksen M.S. Karl R. Rosengren Ph.D. 《Annals of behavioral medicine》2006,31(1):99-103
Background: Physical activity has been positively linked to quality of life (QOL) in older adults. Measures of health status and global
well-being represent common methods of assessing QOL outcomes, yet little has been done to determine the nature of the relationship
of these outcomes with physical activity.Purpose: We examined the roles played by physical activity, health status, and self-efficacy in global QOL (satisfaction with life)
in a sample of older Black and White women.Method: Participants (N = 249, M age = 68.12 years) completed multiple indicators of physical activity, self-efficacy, health status,
and QOL at baseline of a 24-month prospective trial. Structural equation modeling examined the fit of 3 models of the physical
activity and QOL relationship.Results: Analyses indicated that relationships between physical activity and QOL, self-efficacy and QOL were all indirect. Specifically,
physical activity influenced self-efficacy and QOL through physical and mental health status, which in turn influenced global
QOL.Conclusions: Our findings support a social cognitives model of physical activity’s relationship with QOL. Subsequent tests of hypothesized
relationships across time are recommended.
Funding for this study was provided by the National Institute on Aging (Grant AG 20118). We extend our sincere appreciation
to April Bell for all of her efforts on this project. 相似文献
79.
80.