全文获取类型
收费全文 | 2512篇 |
免费 | 207篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 25篇 |
儿科学 | 138篇 |
妇产科学 | 81篇 |
基础医学 | 375篇 |
口腔科学 | 22篇 |
临床医学 | 287篇 |
内科学 | 519篇 |
皮肤病学 | 82篇 |
神经病学 | 253篇 |
特种医学 | 54篇 |
外科学 | 244篇 |
综合类 | 14篇 |
一般理论 | 2篇 |
预防医学 | 292篇 |
眼科学 | 21篇 |
药学 | 131篇 |
中国医学 | 2篇 |
肿瘤学 | 179篇 |
出版年
2023年 | 22篇 |
2022年 | 23篇 |
2021年 | 71篇 |
2020年 | 38篇 |
2019年 | 72篇 |
2018年 | 77篇 |
2017年 | 74篇 |
2016年 | 70篇 |
2015年 | 57篇 |
2014年 | 101篇 |
2013年 | 133篇 |
2012年 | 203篇 |
2011年 | 180篇 |
2010年 | 110篇 |
2009年 | 90篇 |
2008年 | 123篇 |
2007年 | 149篇 |
2006年 | 152篇 |
2005年 | 152篇 |
2004年 | 117篇 |
2003年 | 111篇 |
2002年 | 127篇 |
2001年 | 34篇 |
2000年 | 47篇 |
1999年 | 44篇 |
1998年 | 26篇 |
1997年 | 15篇 |
1996年 | 8篇 |
1995年 | 20篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 30篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1968年 | 5篇 |
排序方式: 共有2721条查询结果,搜索用时 15 毫秒
1.
Few studies have examined the effects of parental incarceration (PI) on outcomes above and beyond other risk and adverse childhood experiences (ACEs). The objectives of this study were to (1) the associations between PI and mental health problems (attention, externalizing, internalizing, and total behavioral problems) and (2) the mediating role of current socioeconomic status and cumulative ACEs. An observational and cross-sectional design was employed. Analyses included hierarchical multivariable linear regression modeling. The analytic sample included 613 adolescents (11–17?years). On average, youth exposed to PI experienced three times as many ACEs compared with youth unexposed. Youth exposed to PI were more likely to have behavioral problems than their unexposed peers. The main effect for all models was attenuated by current economic hardship as well as exposure to increasing numbers of ACEs. Exposure to PI can be viewed as a marker of accumulative risk for intervention since youth impacted by PI are more likely to experience behavioral difficulties and associated adverse childhood experiences. Due to the associated adversity that impact youth exposed to PI, mental health providers need to be able to identify and screen for symptoms associated with trauma. 相似文献
2.
BACKGROUND: Studies have shown that alcoholics have smaller brain volumes than non-alcoholic cohorts, but an effect of family history (FH) of heavy drinking on brain volume has not been demonstrated. We examined the relationship between an FH of heavy drinking and both brain shrinkage as measured by the ratio of brain volumes to intracranial volume (ICV) as well as maximal brain growth as measured by ICV in early-onset and late-onset alcoholics. METHODS: With T1-weighted resonance imaging, we measured ICV, brain volume, and white and gray matter volume in adult treatment-seeking late-onset and early-onset alcoholics with either a positive or a negative FH of heavy alcohol use, and in healthy control subjects. We also calculated brain shrinkage using a ratio of soft tissue volumes to ICV. RESULTS: The FH positive alcoholic patients had significantly smaller ICVs than FH negative patients, suggesting smaller premorbid brain growth. Brain shrinkage did not correlate with FH. Late-onset alcoholics showed a greater difference in ICV between FH positive and FH negative patients than early-onset alcoholics. Late-onset FH positive patients also had significantly lower IQ scores than late-onset FH negative patients, and IQ scores were correlated with ICV. CONCLUSIONS: These data provide evidence that parental alcohol use might increase risk for alcoholism in offspring in part by a genetic and/or environmental effect that might be related to reduced brain growth. 相似文献
3.
4.
F. Giangaspero C. Doglioni M. T. Rivano S. Pileri J. Gerdes H. Stein 《Acta neuropathologica》1987,74(2):179-182
Summary The monoclonal antibody Ki-67, which reacts with cells in the active part of the cell cycle, was used to evaluate immunocytochemically the growth fraction in 22 primary brain neoplasms. The percentage of labelled cells reflected the histological grade of malignancy of each neoplasms. High percentage of Ki-67-positive cells were observed in one choroid plexus carcinoma (60%), one primary melanoma of meninges (40%), three medulloblastomas (40%–50%), one anaplastic astrocytoma and six glioblastomas (10%–40%). One ependymoma had 7% positive cells. Rare positive cells (1%) were present in one pilocytic astrocytoma and one ganglioglioma. Except one negative case, the meningiomas (five cases) had values of positivity ranging from 1% to 6%. Two acoustic schwannomas were negative. These results suggest that immunocytochemical staining with the Ki-67 may be a useful method for measuring the growth fraction in brain neoplasms.Supported in part by Associazione Italiana Ricerca sul Cancro and Ministero Italiano della Pubblica Istruzione 相似文献
5.
6.
C A Mathis J M Gerdes J D Enas J M Whitney S E Taylor Y Zhang D J McKenna S Havlik S J Peroutka 《The Journal of pharmacy and pharmacology》1992,44(10):801-805
The in-vitro inhibition constants (Ki) of 14 structural analogues of the potent 5-hydroxytryptamine (5-HT)-uptake inhibitor paroxetine were determined to assess the structure-affinity relationship of these derivatives. A goal of these studies was to determine those positions on paroxetine which could be derivatized without significantly decreasing the affinity of the drug for the binding site, so that radiolabels such as [18F]fluoroalkyl groups might be appended for future in-vivo imaging studies of the 5-HT uptake system. Using the methyl moiety as a steric probe for these studies, it was found that the rank order of potency of various methyl-substituted paroxetine analogues for inhibiting the binding of [3H]paroxetine to the 5-HT re-uptake site was: 4'-approximately equal to 3'-approximately equal to 2'- > 2'-approximately equal to 1- > 5'- > 6'-methyl. The in-vitro equipotent molar ratios (EPMR, Ki(analogue)/Ki(paroxetine)) of the analogues were determined, and the EPMRs of the 4'-, 3'-, and 2'-methyl derivatives were 1.9, 2.2 and 2.2, respectively. The 4'- and 2'-fluoromethyl and -fluoroethyl analogues were synthesized, and the EPMRs of the 4'- and 2'-fluoromethyl derivatives were determined to be 2.0 and 3.5, and those of the 4'- and 2'-fluoroethyl analogues were 5.2 and 6.2, respectively. The 2'-fluoromethyl analogue was unstable in aqueous solutions, and it is not a promising ligand for in-vivo studies.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
Determination of the growth fraction in monoclonal gammopathy with the monoclonal antibody Ki-67 总被引:3,自引:0,他引:3
Henk M. Lokhorst Saskia E. Boom Wim Terpstra Paul Roholl Johannes Gerdes Bert J. E. G. Bast 《British journal of haematology》1988,69(4):477-481
The monoclonal antibody Ki-67 reacts with a nuclear antigen that is present only in proliferating cells. The proportion of Ki-67 positive cells may therefore serve as a reliable measurement for the growth fraction in normal and neoplasmic cell populations. We have tested the significance of the MoAb Ki-67 in the classification of monoclonal gammopathy and compared the results with the plasma cell labelling index. In benign monoclonal gammopathy the percentage of Ki-67 positive plasma cells (median 1.6%) was significantly lower than in untreated multiple myeloma (median 9.6). Among the patients with more than 10% Ki-67 positive plasma cells there were some very short survivors. The largest growth fractions (median 41.8%) were found in patients with relapsing multiple myeloma indicating here a different growth pattern more resembling the high-grade lymphomas. A linear correlation between the proportion of Ki-67 positive plasma cells and the labelling index was not found. Determination of the plasma cell growth fraction with the monoclonal antibody Ki-67 in monoclonal gammopathy may help to discriminate benign monoclonal gammopathy from multiple myeloma and will probably identify a subgroup of multiple myeloma patients with a poor prognosis, including those with relapsing multiple myeloma. 相似文献
8.
9.
B Flott-Rahmel W Gerdes P A Pechan W Brysch K H Schlingensiepen W Seifert 《Neuroreport》1992,3(12):1077-1080
Basic FGF mRNA induction by bFGF was investigated in cell cultures from rat brain, i.e. postnatal day 2 cortex and embryonic day 18 hippocampus. In situ hybridization shows that after bFGF treatment (10(-10) M) for 14 h neurones and glial cells show a remarkable increase in bFGF mRNA production. Incubation of astrocytes with antisense bFGF phosphorothioate oligodeoxynucleotides (bFGF-PTOs) resulted in an inhibition of both bFGF induced and serum induced proliferation. The results indicate that bFGF is capable of inducing its own mRNA production. This induction, i.e. new synthesis of bFGF mRNA, seems to be essential for the mitogenic effect of both bFGF and serum components. 相似文献
10.
Suzanne C. Tough David W. Johnston Jodi E. Siever Gayleen Jorgenson Linda Slocombe Carolyn Lane Margaret Clarke 《分娩》2006,33(3):183-194
ABSTRACT: Background: The addition of supplementary prenatal support may improve the health and well‐being of high‐risk women and families. The objective of this randomized controlled trial was to examine the impact of supplementary prenatal care on resource use among a community‐based population of pregnant women. Methods: Pregnant women from three urban maternity clinics were randomized (a) to current standard of physician care, (b) to current standard of care plus consultation with a nurse, or (c) to (b) plus consultation with a home visitor. Participants were 1,352 women who received 3 telephone interviews. The primary outcome was resource use (e.g., attended prenatal classes, used nutritional counseling). Results: Overall, those in the nurse intervention group were more likely to attend an “Early Bird” prenatal class and parenting classes, and to use nutrition counseling and agencies that assist with child care. Women provided with extra nursing and home visitation supports were more likely to use a written resource guide, nutrition counseling, and agencies that assist with child care. Among women at higher risk (e.g., language barriers, young maternal age, low income), the nurse intervention significantly increased use of early prenatal classes, whereas the nurse and home visitor intervention significantly increased use of the written resource guide and nutrition counseling. The intervention substantially increased the amount of information received on numerous pregnancy‐related topics but had little impact on resource use for mental health and poverty‐related needs. Among those with added support, resource use among low‐risk women was generally greater than among high‐risk women. Conclusions: Additional support provided by nurses, or nurses and home visitors, can successfully address informational needs and increase the likelihood that women will use existing community‐based resources. This finding was true even for high‐risk women, although this intervention did not reduce the difference in resource use between high‐ and low‐risk women. (BIRTH 33:3 September 2006) 相似文献