全文获取类型
收费全文 | 24145篇 |
免费 | 2255篇 |
国内免费 | 174篇 |
专业分类
耳鼻咽喉 | 208篇 |
儿科学 | 586篇 |
妇产科学 | 587篇 |
基础医学 | 3339篇 |
口腔科学 | 641篇 |
临床医学 | 2601篇 |
内科学 | 5002篇 |
皮肤病学 | 310篇 |
神经病学 | 2530篇 |
特种医学 | 1028篇 |
外国民族医学 | 1篇 |
外科学 | 3095篇 |
综合类 | 702篇 |
一般理论 | 25篇 |
预防医学 | 2164篇 |
眼科学 | 647篇 |
药学 | 1761篇 |
2篇 | |
中国医学 | 38篇 |
肿瘤学 | 1307篇 |
出版年
2021年 | 267篇 |
2020年 | 182篇 |
2019年 | 290篇 |
2018年 | 374篇 |
2017年 | 297篇 |
2016年 | 293篇 |
2015年 | 343篇 |
2014年 | 481篇 |
2013年 | 870篇 |
2012年 | 1130篇 |
2011年 | 1227篇 |
2010年 | 627篇 |
2009年 | 632篇 |
2008年 | 1125篇 |
2007年 | 1274篇 |
2006年 | 1252篇 |
2005年 | 1287篇 |
2004年 | 1231篇 |
2003年 | 1148篇 |
2002年 | 1176篇 |
2001年 | 540篇 |
2000年 | 509篇 |
1999年 | 483篇 |
1998年 | 301篇 |
1997年 | 254篇 |
1996年 | 255篇 |
1995年 | 266篇 |
1994年 | 237篇 |
1993年 | 228篇 |
1992年 | 411篇 |
1991年 | 461篇 |
1990年 | 422篇 |
1989年 | 348篇 |
1988年 | 403篇 |
1987年 | 346篇 |
1986年 | 339篇 |
1985年 | 356篇 |
1984年 | 325篇 |
1983年 | 252篇 |
1982年 | 206篇 |
1981年 | 226篇 |
1980年 | 207篇 |
1979年 | 278篇 |
1978年 | 222篇 |
1977年 | 215篇 |
1976年 | 193篇 |
1975年 | 195篇 |
1974年 | 218篇 |
1973年 | 169篇 |
1972年 | 186篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Gordon C. Nagayama Hall 《Clinical psychology》2006,13(3):258-262
Clinical psychology is not as diverse as society, and the generalizability of clinical psychology to diverse groups has largely been untested. Some progress has been made in increasing the number of ethnic minorities receiving PhD degrees in clinical psychology and in increasing ethnic minority representation in clinical trials. Nevertheless, clinical psychologists and clinical psychology research are not diverse. A stages of change model may be useful in motivating clinical psychologists to diversify. A future scenario involving inertia and a second involving change are offered. 相似文献
92.
OBJECTIVE: The corrosion potential of a dental amalgam restoration is generally determined using a single measurement, even though environmental factors and abrasion can continuously alter the surface state and reactivity of this alloy. It was, therefore, the purpose of this study to determine the maximum variability of the corrosion potential of aged dental amalgam restorations, for 28 days. METHODS: The corrosion potentials of 148 aged dental amalgam restorations in 12 human subjects were measured at t = 0 and 4 h, and 4, 7, 14, 21 and 28 days. Measurements were made with a high impedance voltmeter and a Ag/AgCl micro-reference electrode. The subjects were instructed not to alter their usual eating and oral hygiene routines. RESULTS: Corrosion potential changes occurred throughout the 28 days. They were both positive and negative for the same restoration, and were sometimes very large. Only 4 h after the initial measurement, the absolute value of the corrosion potential changes ranged between 18 and 287 mV for 50% of the restorations. The largest maximum absolute corrosion potential change for each subject's restorations ranged between 85 and 329 mV. Statistical analysis showed that the overall mean maximum absolute corrosion potential change for the subjects' restorations was 74 mV. SIGNIFICANCE: It was shown that the corrosion potential of aged dental amalgam restorations varies substantially over time, and that a single measurement is not representative of short- or long-term electrochemical behavior. This finding has implications regarding the corrosion rate of dental amalgam restorations, particularly those that are part of a galvanic couple. 相似文献
93.
Tips for learners of evidence-based medicine: 4. Assessing heterogeneity of primary studies in systematic reviews and whether to combine their results 总被引:2,自引:0,他引:2 下载免费PDF全文
94.
F. F. Isik T. O. McDonald M. Ferguson E. Yamanaka D. Gordon 《The American journal of pathology》1992,141(5):1139-1149
Transplant arteriosclerosis (TA) has emerged as an obstacle to the long-term survival of transplanted organs, especially cardiac transplants. The animal models that have been used to study TA have not been fully characterized with regard to features such as the time course of cell proliferation and the sequence of cell types arriving in the developing intimal lesion. We present a model of TA based on a transplanted segment of abdominal aorta that helps address these questions. Two strains of rats (PVG x DA) underwent orthotopic aortic transplantation without immunosuppression and were killed at 14, 20, 40, and 60 days after transplantation. The within-strain control group displayed minimal evidence of cellular rejection with minimal to absent intimal lesions. In contrast, the allograft group showed a linearly increasing intimal lesion, up through 60 days after transplantation. The mechanism of intimal thickening was by an increase in cell number at the earlier time points with the later deposition of extracellular matrix. The early intimal lesion consisted mostly of mononuclear inflammatory cells (45%) with gradually increasing presence of smooth muscle cells (SMC) in the intima between 20 and 60 days. Conversely, the media showed gradual infiltration by macrophage-type cells with virtual loss of all SMC from the media by 40 days. The proliferative index showed a peak of 6% and 8% at 20 days in both the intima and media, respectively, and was preceded by the presence of macrophages. In fact, most of the proliferating cells at the earlier time points were either monocytes/macrophages, or were immediately adjacent to monocyte-/macrophage-rich regions. This straight artery segment model of transplant arteriosclerosis provides an easily quantifiable system in which the effects of different interventions (e.g., immunosuppressive regimens) can be tested. 相似文献
95.
An enzymatic mutant of Shiga-like toxin II variant is a vaccine candidate for edema disease of swine. 总被引:5,自引:0,他引:5 下载免费PDF全文
Edema disease (ED) of weanling pigs is caused by an infection with Escherichia coli that produces Shiga-like toxin II variant (SLT-IIv). Pathology identical to that caused by ED can be duplicated in pigs that are injected with less than 10 ng of purified SLT-IIv per kg of body weight. Therefore, SLT-IIv was mutated to create an immunoreactive form of the toxin that was significantly reduced in enzymatic activity. Initially, purified SLT-IIv was treated with formaldehyde which abrogated cytotoxic activity. Pigs were vaccinated with the toxoid (100 micrograms) to determine whether a toxoid was a viable vaccine candidate and whether young pigs were capable of mounting an immune response. Although the pigs developed a neutralizing antibody titer (1:128 to 1:512) 28 days postinjection, they also lost weight and developed ED lesions. The deleterious effect of the toxoid appeared to result from residual enzymatic activity or a reversion to a toxic form. An alternative method, site-directed mutagenesis, was employed to consistently reduce the enzymatic activity of SLT-IIv. Glutamate at position 167 of the mature A subunit was replaced by aspartate (E167D), and arginine at position 170 was replaced by lysine (R170K). These mutations reduced cytotoxic activity 10(4)-fold and 10-fold, respectively, while the enzymatic activities were decreased 400-fold and 5-fold, respectively. The activity of a toxin that contained both mutations (SLT-IIvE167D/R170K) closely resembled that of SLT-IIvE167D. When position 167 was replaced by glutamine (E167Q), the cytotoxic activity decreased 10(6)-fold and the enzymatic activity decreased approximately 1,500-fold. Pigs that were vaccinated with purified, mutant toxin designated SLT-IIvE167Q developed a neutralizing antibody titer of 1:512 21 days postinjection, and their tissues were free of ED lesions. These data suggest that SLT-IIvE167Q may represent an effective vaccine against ED. 相似文献
96.
Pierre man John Gordon Hkan Mellstedt Peter Biberfeld George Klein 《European journal of haematology》1988,40(2):142-148
Leukemic cells from a series of patients with chronic B-lymphocytic leukemia (CLL) were analyzed for their buoyant density on discontinuous Percoll gradients. The density profile varied markedly between different patients and also between samples from different body compartments within the same patient. A good correlation was observed between buoyant density and maturation stage of the leukemic clones as judged by Ig-expression and their reactivity with a panel of monoclonal antibodies. Phorbol-ester-induced changes in the leukemic cells were found to be accompanied by a general decrease in their buoyant density. No correlation between density and clinical parameters such as cell counts, clinical stage and survival could be noted. Buoyant density characterization of leukemic B-cell populations is seen as a useful, rapid and simple marker of compartmentalization within the B-lymphocyte maturation spectrum but its clinical relevance remains to be established. 相似文献
97.
98.
99.
Sher Geoffrey; Feinman Michael; Zouves Christo; Kuttner Gordon; Maassarani Ghanima; Salem Rifaat; Matzner William; Ching Wendell; Chong Penny 《Human reproduction (Oxford, England)》1994,9(12):2278-2283
This study was undertaken to explore whether intervention withheparin and aspirin (H/A) in selected patients undergoing in-vitrofertilization (TVF) and embryo transfer could improve fecundityrates. Specifically, it explored the possibility that womendiagnosed with organic pelvic disease who demonstrated antiphospholipidantibodies (APA) could benefit from H/A administration in asimilar manner to that used in patients with recurrent pregnancyloss. We used an enzymelinked immunosorbent assay forsix different phospholipids to identify patients who expressedAPA before they underwent IVF/embryo transfer. This study wasconfined to the first IVF/embryo transfer cycle that followedassessment of APA status and accordingly, the number of IVF/embryotransfer cycles corresponds with the number of patients treated.APA seropositive patients were treated with aspirin, 81 mg orallyq.d., and heparin 5000 IU s.c. b.i.d., beginning on day 1 ofcontrolled ovarian stimulation. The endpoint for success wasa live birth or an ultrasound confirming fetal cardiac activity(a viable pregnancy). The prevalence of APA in patients diagnosedwith organic pelvic disease (53%) was much higher than in thosewithout female pathology (14%). The administration of H/A toAPA seropositive patients significantly (P < 0.05) improvedthe viable pregnancy rate (49%) compared to the untreated APAseropositive group (16%). The viable pregnancy rate for APAseropositive women treated with H/A was also significantly (P< 0.001) higher than for untreated APA seronegative patients(27%). We conclude that all women undergoing IVF/embryo transfershould be tested for APA prior to initiating ovarian stimulation,and those with APA seropositivity should be treated with H/A. 相似文献
100.
Christine Liddell Gordon Rae Tom R M Brown David Johnston Vivien Coates John Mallett 《The British journal of general practice》2004,54(506):667-672
BACKGROUND: Providing patients with an audiotape of their medical consultation has been a relatively common practice in oncology clinics for some years. However, broader generalisability of the technique has yet to be examined. AIMS: To investigate the efficacy of providing patients with an audiotape of their consultation in a general practice setting. DESIGN OF STUDY: Randomised controlled trial: 95 experimental participants, 85 controls. SETTING: Routine surgeries run by two general practitioners (GPs) in two different health centres. METHOD: All patients attending GP appointments were eligible for inclusion. Patients were followed up by telephone 7-10 days later. RESULTS: More than half (61%) of the patients who received a tape listened to it. Among listeners, 64% rated the tape useful or very useful; 24% noticed information not heard in the consultation. Half of listeners (46%) said that their understanding of the consultation improved after listening to the tape. Half of the listeners (48%) shared the tape with others, of whom 71% found sharing helpful or very helpful. However, 21% of those who shared the information with others found this unhelpful or very unhelpful, suggesting that patients may need to be briefed on the potential risks of sharing. At follow-up a week later, it emerged that being given a tape had no effect on adherence with GPs' advice, nor on anxiety about conditions. CONCLUSION: Providing patients with an audiotape of their GP consultation was positively rated by many patients. Although there were no detectable clinical effects at follow-up, the technique merits further evaluation in general practice. 相似文献