全文获取类型
收费全文 | 7672篇 |
免费 | 523篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 72篇 |
儿科学 | 236篇 |
妇产科学 | 171篇 |
基础医学 | 1320篇 |
口腔科学 | 69篇 |
临床医学 | 920篇 |
内科学 | 1569篇 |
皮肤病学 | 178篇 |
神经病学 | 853篇 |
特种医学 | 144篇 |
外国民族医学 | 5篇 |
外科学 | 763篇 |
综合类 | 18篇 |
一般理论 | 2篇 |
预防医学 | 578篇 |
眼科学 | 92篇 |
药学 | 477篇 |
中国医学 | 11篇 |
肿瘤学 | 729篇 |
出版年
2023年 | 33篇 |
2022年 | 54篇 |
2021年 | 150篇 |
2020年 | 108篇 |
2019年 | 134篇 |
2018年 | 166篇 |
2017年 | 124篇 |
2016年 | 142篇 |
2015年 | 191篇 |
2014年 | 252篇 |
2013年 | 346篇 |
2012年 | 568篇 |
2011年 | 569篇 |
2010年 | 304篇 |
2009年 | 303篇 |
2008年 | 487篇 |
2007年 | 509篇 |
2006年 | 485篇 |
2005年 | 512篇 |
2004年 | 462篇 |
2003年 | 480篇 |
2002年 | 456篇 |
2001年 | 103篇 |
2000年 | 95篇 |
1999年 | 118篇 |
1998年 | 105篇 |
1997年 | 80篇 |
1996年 | 56篇 |
1995年 | 73篇 |
1994年 | 52篇 |
1993年 | 40篇 |
1992年 | 54篇 |
1991年 | 62篇 |
1990年 | 58篇 |
1989年 | 52篇 |
1988年 | 38篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 41篇 |
1983年 | 23篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 26篇 |
1977年 | 13篇 |
1974年 | 14篇 |
1973年 | 10篇 |
1972年 | 19篇 |
1970年 | 16篇 |
排序方式: 共有8207条查询结果,搜索用时 328 毫秒
1.
2.
Angela J. Jacques-Tiura Deborah A. Ellis April Idalski Carcone Sylvie Naar Kathryn Brogan Hartlieb Elizabeth K. Towner Thomas N. Templin K.-L. Catherine Jen 《The Journal of adolescent health》2019,64(3):355-361
Objective
Successful weight loss interventions for African-Americans adolescents are lacking. Cognitive-behavioral interventions seek to develop weight loss skills (e.g., counting calories, goal setting, managing one's environment). Little is known about how well adolescents implement such skills in their daily lives. Study aims were to (1) examine weight loss skills utilization at midpoint and end of a 6-month cognitive-behavioral/motivational interviewing weight loss sequential multiple assignment randomized trial (SMART), and (2) determine if greater skill utilization predicted weight loss at treatment end and 3 months post-treatment.Method
One hundred and eighty six African-Americans adolescents with obesity and their caregiver were first randomly assigned to complete 3 months of cognitive-behavioral and motivational interviewing family-based weight loss treatment in their home or in the research office (Phase 1). Nonresponders (i.e., those who lost < 3% of initial weight, n?=?161) were rerandomized to 3 months of continued skills training (n?=?83) or contingency management (n?=?78) for Phase 2; responders were allocated to 3 months of relapse prevention (n?=?20). Adolescents’ frequency of weight loss skills utilization was assessed via questionnaire at treatment midpoint and end.Results
Higher treatment attendance was associated with better skill utilization. Higher skill utilization was associated with more weight loss at treatment end, whereas higher baseline confidence was associated with more weight loss at follow-up.Conclusions
This study indicates the importance of attending weight loss intervention sessions to develop and strengthen weight loss skills in African-American adolescents with obesity, and strengthening confidence to use such skills for continued weight loss. 相似文献3.
Adeline Tarantini Sylvie Huet Gérard Jarry Rachelle Lanceleur Martine Poul Ana Tavares Nádia Vital Henriqueta Louro Maria João Silva Valérie Fessard 《Environmental and molecular mutagenesis》2015,56(2):218-227
Synthetic amorphous silica (SAS) in its nanosized form is now used in food applications although the potential risks for human health have not been evaluated. In this study, genotoxicity and oxidative DNA damage of two pyrogenic (NM‐202 and 203) and two precipitated (NM‐200 and ‐201) nanosized SAS were investigated in vivo in rats following oral exposure. Male Sprague Dawley rats were exposed to 5, 10, or 20 mg/kg b.w./day for three days by gavage. DNA strand breaks and oxidative DNA damage were investigated in seven tissues (blood, bone marrow from femur, liver, spleen, kidney, duodenum, and colon) with the alkaline and the (Fpg)‐modified comet assays, respectively. Concomitantly, chromosomal damage was investigated in bone marrow and in colon with the micronucleus assay. Additionally, malondialdehyde (MDA), a lipid peroxidation marker, was measured in plasma. When required, a histopathological examination was also conducted. The results showed neither obvious DNA strand breaks nor oxidative damage with the comet assay, irrespective of the dose and the organ investigated. Similarly, no increases in chromosome damage in bone marrow or lipid peroxidation in plasma were detected. However, although the response was not dose‐dependent, a weak increase in the percentage of micronucleated cells was observed in the colon of rats treated with the two pyrogenic SAS at the lowest dose (5 mg/kg b.w./day). Additional data are required to confirm this result, considering in particular, the role of agglomeration/aggregation of SAS NMs in their uptake by intestinal cells. Environ. Mol. Mutagen. 56:218–227, 2015. © 2014 Wiley Periodicals, Inc. 相似文献
4.
Grulois Daphné Tiavouane Josina Dumas Pascal Paul Fauvelot Cécile 《Conservation Genetics Resources》2015,7(1):73-75
Conservation Genetics Resources - Fifteen polymorphic microsatellite markers were developed for Tridacna maxima in order to assess self-recruitment and larval dispersal within and among MPAs in New... 相似文献
5.
R Mandeville F Dumas A Amarouch S Sidrac-Ghali M C Walker M Zelechowska I Ajdukovic B Grouix 《Hybridoma》1987,6(5):441-451
This study reports the purification and characterization of a high molecular weight human breast cancer-associated antigen identified by a previously described (1,2) murine monoclonal antibody, BCD-B4. Immunohistochemical analysis indicated that BCD-B4 recognizes an antigen expressed in an altered form on the human breast carcinoma cell line, BT-20, compared to the non-malignant human mammary epithelial cell line, HBL-100. Chemical treatments and enzymatic digestions suggested that the recognized moiety was a protein. The antigenic determinant was resistant to neuraminidase and periodate treatments but was sensitive to trypsin and proteinase K. The antigen was purified by affinity chromatography and its molecular weight, determined by SDS-PAGE analysis under non-reducing conditions, was proven to be 250 Kd. Under reducing conditions, the molecule dissociated into two polypeptides of 125 and 45 Kd, respectively. Both subunits could be isolated from normal HBL-100 and neoplastic BT-20 cellular protein extracts by affinity chromatography. The higher molecular weight subunit showed; however, qualitative and quantitative differences between the two cell lines: it was expressed in greater quantity on BT-20 cells and its molecular weight was 15 Kd higher. Both subunits could also be identified by immunoblots of BT-20 cells. 相似文献
6.
The effect of imipramine, desipramine, ketanserin and lithium on Type II glucocorticoid receptor (GR) mRNA levels was studied in rat brain regions involved in the control of the hypothalamo-pituitary-adrenal (HPA) axis, the dysregulation of which has been implicated in the pathophysiology of major depression. Northern blot analysis of Type II GR mRNA showed that treatment of male rats with either desipramine or imipramine increased hypothalamic and hippocampal GR mRNA levels. Upregulation of GR mRNA following administration of imipramine was found in brain regions of female rats, while desipramine had no effect. Ketanserin increased levels of GR mRNA in hippocampus of male, but not female, rats. Lithium also was able to induce important increases rat brain GR mRNA; this effect was particularly marked in females.
We conclude that desipramine, imipramine, ketanserin and lithium can modulate GR mRNA in regions of rat brain involved in the control of the HPA axis and may have a common mechanism of action at the level of the GR gene. Sexual dimorphism for drug regulation of brain GR mRNA content was shown and may be related to sex differences in the prevalence of certain affective disorders. 相似文献
7.
8.
Injections of the retrograde fluorescent tracer fast blue in the striatum (STR) and nuclear yellow in the internal segment of the globus pallidus (GPi) in the squirrel monkey (Saimiri sciureus) revealed a nigropallidal projection whose cellular origin was largely distinct from that of the nigrostriatal pathway. Neurons containing the tracer injected in GPi were scattered throughout the substantia nigra-ventral tegmental area complex where they formed approximately 20-25% of the total number of retrogradely labeled cells. Only about 5-10% of all positive neurons were double-labeled after STR-GPi injections. In experiments combining the use of the fluorescent tracer propidium iodide with immunofluorescence, the majority of neurons projecting to GPi displayed tyrosine hydroxylase immunoreactivity. Hence, in addition to their important role at striatal level, midbrain dopaminergic neurons may influence directly the output neurons of the basal ganglia at pallidal level in primates. 相似文献
9.
10.
We focus on the Fisher information matrix used for design evaluation and optimization in nonlinear mixed effects multiple response models. We evaluate the appropriateness of its expression computed by linearization as proposed for a single response model. Using a pharmacokinetic–pharmacodynamic (PKPD) example, we first compare the computation of the Fisher information matrix with approximation to one derived from the observed matrix on a large simulation using the stochastic approximation expectation–maximization algorithm (SAEM). The expression of the Fisher information matrix for multiple responses is also evaluated by comparison with the empirical information obtained through a replicated simulation study using the first‐order linearization estimation methods implemented in the NONMEM software (first‐order (FO), first‐order conditional estimate (FOCE)) and the SAEM algorithm in the MONOLIX software. The predicted errors given by the approximated information matrix are close to those given by the information matrix obtained without linearization using SAEM and to the empirical ones obtained with FOCE and SAEM. The simulation study also illustrates the accuracy of both FOCE and SAEM estimation algorithms when jointly modelling multiple responses and the major limitations of the FO method. This study highlights the appropriateness of the approximated Fisher information matrix for multiple responses, which is implemented in PFIM 3.0, an extension of the R function PFIM dedicated to design evaluation and optimization. It also emphasizes the use of this computing tool for designing population multiple response studies, as for instance in PKPD studies or in PK studies including the modelling of the PK of a drug and its active metabolite. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献