全文获取类型
收费全文 | 10224篇 |
免费 | 863篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 100篇 |
儿科学 | 321篇 |
妇产科学 | 184篇 |
基础医学 | 1276篇 |
口腔科学 | 183篇 |
临床医学 | 1258篇 |
内科学 | 2206篇 |
皮肤病学 | 145篇 |
神经病学 | 921篇 |
特种医学 | 348篇 |
外科学 | 1296篇 |
综合类 | 138篇 |
一般理论 | 7篇 |
预防医学 | 1238篇 |
眼科学 | 318篇 |
药学 | 633篇 |
中国医学 | 4篇 |
肿瘤学 | 538篇 |
出版年
2022年 | 79篇 |
2021年 | 207篇 |
2020年 | 110篇 |
2019年 | 180篇 |
2018年 | 205篇 |
2017年 | 156篇 |
2016年 | 163篇 |
2015年 | 175篇 |
2014年 | 253篇 |
2013年 | 389篇 |
2012年 | 586篇 |
2011年 | 676篇 |
2010年 | 283篇 |
2009年 | 288篇 |
2008年 | 516篇 |
2007年 | 535篇 |
2006年 | 555篇 |
2005年 | 484篇 |
2004年 | 507篇 |
2003年 | 447篇 |
2002年 | 436篇 |
2001年 | 267篇 |
2000年 | 273篇 |
1999年 | 218篇 |
1998年 | 92篇 |
1997年 | 81篇 |
1996年 | 71篇 |
1995年 | 82篇 |
1994年 | 67篇 |
1993年 | 83篇 |
1992年 | 182篇 |
1991年 | 178篇 |
1990年 | 189篇 |
1989年 | 156篇 |
1988年 | 168篇 |
1987年 | 151篇 |
1986年 | 153篇 |
1985年 | 132篇 |
1984年 | 95篇 |
1983年 | 97篇 |
1982年 | 81篇 |
1981年 | 54篇 |
1979年 | 66篇 |
1978年 | 82篇 |
1977年 | 71篇 |
1976年 | 59篇 |
1974年 | 63篇 |
1973年 | 62篇 |
1972年 | 53篇 |
1971年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Nicotine discrimination and self-administration in humans as a function of smoking status 总被引:2,自引:2,他引:0
Nicotine’s discriminative stimulus effects may be critical to understanding reinforcement of tobacco smoking. It is not known
whether regular nicotine exposure produces tolerance or sensitivity to these effects. In this study, male and female smokers
(n = 11) and never-smokers (n = 10) were trained to discriminate 20 μg/kg nicotine by nasal spray from placebo (0) on day 1. On day 2, both groups were
tested on generalization of this discrimination across intermittent presentations of 0, 3, 6, 12, and 20 μg/kg nicotine in
random order. Quantitative and quantal behavioral discrimination tasks, used in previous research, were employed. On day 3,
subjects were instructed to self-administer sprays from the 20 μg/kg nicotine versus 0 bottles in a concurrent-choice procedure.
All but one subject (female smoker) learned reliably to discriminate 20 μg/kg nicotine from placebo (≥ 80% correct) on day 1. Nicotine-appropriate responding on day 2 was attenuated in smokers versus never-smokers at 20 μg/kg
on the quantitative task and at 12 μg/kg on the quantal task, suggesting tolerance. There was no difference in responding
at other doses. Smokers also showed attenuated responses on the subjective measure of “head rush”, which was associated with
discrimination responding in both groups. Nicotine self-administration was significantly greater in smokers versus never-smokers,
who self-administered nicotine below chance levels, and was inversely related to discrimination behavior in never-smokers
but unrelated in smokers. Women smokers showed less change in nicotine-appropriate responding across generalization doses,
reported less confidence in discriminating training doses during acquisition on day 1, and tended to self-administer less
nicotine on day 3. These results indicate that smokers may become tolerant to the discriminative stimulus effects of nicotine,
perhaps promoting increased use.
Received: 1 October 1996/Final version: 28 January 1997 相似文献
52.
J H Sanders 《North Carolina medical journal》1989,50(10):584-585
53.
J E Sanders 《Paediatrician》1991,18(1):76-81
As increasing numbers of children are surviving beyond the 1st decade after marrow transplantation and increasing numbers of children are receiving marrow transplants each year, the delayed effects related to the transplant procedure itself, the original disease, and/or the transplant preparative regimen are becoming apparent. Late effects related to the transplant procedure include those of engraftment stability, the chronic immunosuppression of chronic graft-versus-host disease and delayed immunologic recovery. Recurrent disease is the major late effect related to the patient's original disease. The late effects which may be related to previous therapy administered and/or the transplant preparative regimen include abnormalities of neuroendocrine function, ocular problems, dental developmental abnormalities in young children, central nervous system dysfunction and the development of secondary malignancies. To improve the quality of life of marrow transplant recipients and to prevent some of the growth and development abnormalities which may occur, an awareness of the problems encountered to date is needed. 相似文献
54.
Malanda Nsuami Migel Elie Bridget N Brooks Ladatra S Sanders Theresa D Nash Feseha Makonnen Stephanie N Taylor Deborah A Cohen 《The Journal of adolescent health》2003,32(5):336-339
In an urban school district, 636 students in grades 9-12 were tested for Chlamydia trachomatis and Neisseria gonorrhoeae by ligase chain reaction assays using specimens collected for routine urinalyses during sports physical examinations. Chlamydia and gonorrhea prevalences were 2.8% and 0.7% among males, and 6.5% and 2.0% among females, respectively. Among athletes infected with either sexually transmitted disease (STD), 93.1% reported no symptoms, and treatment was documented for 75.9%. Sports physicals offered a unique opportunity to screen and treat adolescents for STDs and to provide STD-prevention counseling. 相似文献
55.
C. C. Sanders W. E. Sanders Jr. 《European journal of clinical microbiology & infectious diseases》1987,6(4):435-438
The clinical problems caused by inducible beta-lactamases in certain gram-negative bacteria are being recognized with increasing frequency. These problems include the rapid emergence of multiple beta-lactam resistance during therapy with many of the newer beta-lactam antibiotics. Such multiply resistant organisms are now spreading within the hospital and have become important nosocomial pathogens. This has been a particularly difficult problem for intensive care units, cystic fibrosis centers and burn units where there are clusters of patients who are highly susceptible to infections with organisms likeEnterobacter spp.,Serratia spp. andPseudomonas aeruginosa, which possess inducible beta-lactamases. Only through an awareness of these problems, their cause, and restriction of the use of certain newer betalactam antibiotics can these problems be controlled. 相似文献
56.
Melinda Braskett MD Robert L. Roberts MD PhD 《Clinical Pediatric Emergency Medicine》2007,8(2):96-103
The potential for morbidity and mortality in patients who have PID with febrile and nonfebrile illness is extremely high. Familiarity with the clinical manifestations of PID and collaboration with a pediatric immunologist are prerequisites for optimal short-term care of these complex patients. Conservative management with empiric broad-spectrum antimicrobials, early and aggressive surgical debridement of abscesses, and admission at a tertiary pediatric care center are often indicated. 相似文献
57.
Polyacrylamide gel electrophoresis of acid phosphatase from prostatic tissue reveals one more band than seminal plasma. It was attempted to ascertain which subcellular fraction was responsible for that intracellularly localized enzyme. Prostatic epithelium from patients with prostatic hyperplasia was homogenized, and a lysosomal and microsomal fraction were prepared by differential centrifugation. These two fractions were further centrifuged on an isopycnic Percoll gradient. The intracellularly localized form of acid phosphatase was associated with the lysosomal as well as with the microsomal fraction. In a fused rocket electrophoresis experiment these acid phosphatases cross-reacted with antiserum from seminal plasma. After neuraminidase treatment of the acid phosphatase of lysosomal and microsomal origin, only one activity band was found in polyacrylamide gels. It is concluded that only one acid phosphatase protein exists in prostatic epithelium; differences in electrophoretic mobility are caused mainly by different amounts of sialic acid residues, coupled to the same protein backbone. 相似文献
58.
Rajiv Tandon Robert Goldman John R. DeQuardo Mona Goldman Melinda Perez Michael Jibson 《Journal of psychiatric research》1993,27(4):341-347
Although negative symptoms were traditionally considered to be unresponsive to neuroleptic medication, recent studies have demonstrated that negative symptoms do improve during neuroleptic treatment and that such improvement tends to occur concurrently with improvement in positive symptoms. Clozapine is an atypical neuroleptic that is effective in a significant proportion of otherwise neuroleptic-nonresponsive schizophrenic patients; in contrast to conventional neuroleptics, clozapine is also purported to possess unique efficacy in the amelioration of negative symptoms. How clozapine-associated reduction in negative symptoms relates to change in positive symptoms is not clear. To study the relationship between change in positive and negative symptoms during clozapine treatment, we monitored symptomatology in 40 DSM-III-R schizophrenic patients before and about 8 weeks after a trial of clozapine. Both positive and negative symptoms improved significantly. There was a significant correlation (r = .63,p <.01) between change in positive symptoms and change in negative symptoms; as with conventional neuroleptics, negative symptoms improved concomitantly with positive symptoms during clozapine treatment. Clozapine's apparent greater efficacy on negative symptoms may be related to its greater efficacy on positive symptoms in otherwise neuroleptic-refractory patients and its lesser propensity to cause extrapyramidal side-effects. 相似文献
59.
Coexistence of Neoplasia and Cortical Dysplasia in Patients Presenting with Seizures 总被引:16,自引:10,他引:6
Summary: Tumors and cortical dysplasia are associated with epilepsy, but few studies have examined the coexistence of neoplasia and dysplasia in these patients. We studied 13 patients (age 4–29 years) with recurrent seizures of 1 month to 21-year' duration (median 72 months). Ten patients were aged <21 years. Imaging studies localized the lesion to the temporal lobe (10 patients), parietal lobe (2 patients), and frontal lobe (1 patient). Tumors included ganglioglioma (8 patients), dysembryoplastic neuroepithelial tumor (DNT) (3 patients), and low-grade as- trocytoma (2 patients). Cortical dysplasia, including atypical aggregates of neurons (6 patients), multifocal loss of the cortical laminar architecture (7 patients), and neurons in the molecular layer of the cortex (3 patients) were observed near but separate from the tumor. Coexistence of certain tumors with cortical dysplasia, most frequently observed in the pediatric population, suggests a hamar-tomatous/dysplastic nature of the neoplasms. 相似文献
60.
The authors completed a retrospective chart review of the records of all patients identified with diagnoses of mania and schizoaffective disorder, manic type, who underwent electroconvulsive therapy between the years 1973 and 1986 at McLean Hospital. Ten of 18 manic patients (56%) and 3 of 9 schizoaffective patients (33%) experienced meaningful clinical benefit. The authors report the correlation of treatment and patient factors with outcome and review the literature on the convulsive therapy of mania. 相似文献