全文获取类型
收费全文 | 1931篇 |
免费 | 261篇 |
国内免费 | 19篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 105篇 |
妇产科学 | 60篇 |
基础医学 | 400篇 |
口腔科学 | 77篇 |
临床医学 | 200篇 |
内科学 | 306篇 |
皮肤病学 | 52篇 |
神经病学 | 103篇 |
特种医学 | 261篇 |
外科学 | 187篇 |
综合类 | 55篇 |
一般理论 | 1篇 |
预防医学 | 128篇 |
眼科学 | 18篇 |
药学 | 103篇 |
1篇 | |
肿瘤学 | 138篇 |
出版年
2021年 | 13篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 21篇 |
2017年 | 12篇 |
2016年 | 21篇 |
2015年 | 43篇 |
2014年 | 40篇 |
2013年 | 61篇 |
2012年 | 61篇 |
2011年 | 60篇 |
2010年 | 76篇 |
2009年 | 74篇 |
2008年 | 55篇 |
2007年 | 71篇 |
2006年 | 62篇 |
2005年 | 49篇 |
2004年 | 49篇 |
2003年 | 51篇 |
2002年 | 62篇 |
2001年 | 53篇 |
2000年 | 31篇 |
1999年 | 45篇 |
1998年 | 92篇 |
1997年 | 81篇 |
1996年 | 68篇 |
1995年 | 69篇 |
1994年 | 46篇 |
1993年 | 54篇 |
1992年 | 31篇 |
1991年 | 40篇 |
1990年 | 48篇 |
1989年 | 75篇 |
1988年 | 77篇 |
1987年 | 66篇 |
1986年 | 50篇 |
1985年 | 41篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 15篇 |
1972年 | 20篇 |
1968年 | 11篇 |
排序方式: 共有2211条查询结果,搜索用时 15 毫秒
991.
Nucleolar organiser regions in normal, cirrhotic, and carcinomatous livers. 总被引:4,自引:5,他引:4 下载免费PDF全文
A series of 54 liver biopsy specimens was studied by means of the argyrophil (AgNOR) technique for nucleolar organiser region (NOR)-associated proteins. These included normal livers and livers affected by chronic active hepatitis, cirrhosis, hepatocellular carcinoma and adenoma. Four of the cases of cirrhosis showed liver cell dysplasia. The mean numbers of NOR sites in normal, cirrhotic, and carcinomatous livers were significantly different: adenoma had similar mean counts to those in chronic active hepatitis (CAH). There was no overlap between the ranges of NOR counts in normal, cirrhotic, and malignant liver specimens. Where cirrhosis and hepatocellular carcinoma were present in the same specimen, the AgNOR counts were higher in the carcinomatous than cirrhotic areas. To investigate the prospective value of the method a further seven biopsy specimens were studied; in these it had not been possible to decide on a diagnosis between normality and cirrhosis or cirrhosis and hepatocellular carcinoma. In all seven specimens a repeat biopsy or necropsy gave results as predicted by AgNOR staining. It is therefore proposed that quantitation of staining for NOR-associated proteins is a diagnostically useful method in liver disease. 相似文献
992.
TGF-β1壳聚糖微球的制备及其缓释效果研究 总被引:4,自引:0,他引:4
目的:制备转化生长因子β1(TGF-β1)壳聚糖微球,并研究其体外缓释效果。方法:采用乳化交联的方法制备壳聚糖微球,然后吸附TGF-β1获得TGF-β1壳聚糖微球。利用酶联免疫吸附的方法(ELISA)动态检测7 d内TGF-β1壳聚糖微球的缓释效果,并绘制释放曲线。结果:壳聚糖微球形态较好,粒径为(8.6±2.8)μm。TGF-β1壳聚糖微球在缓释实验的前12 h内释放速度较快,随后释放趋于平稳。7 d内微球的TGF-β1释放率为42.6%。结论:TGF-β1壳聚糖微球的制备工艺简单可行,成球性好,具有良好的缓释效果。 相似文献
993.
Marian AJ Weterman Fred van Ruissen Marit de Wissel Lou Bordewijk Johnny PA Samijn W Ludo van der Pol Farid Meggouh Frank Baas 《European journal of human genetics : EJHG》2010,18(4):421-428
In several individuals with a Charcot–Marie–Tooth (CMT) phenotype, we found a copy number variation (CNV) on chromosome 17p12 in the direct vicinity of the peripheral myelin protein 22 (PMP22) gene. The exact borders and size of this CNV were determined by Southern blot analysis, MLPA, vectorette PCR, and microarray hybridization analyses. All patients from six apparently unrelated families carried an identical 186-kb duplication different from the commonly reported 1.5-Mb duplication associated with CMT1A. This ancestral mutation that was not reported in the human structural variation database was only detected in affected individuals and family members. It was absent in 2124 control chromosomes and 40 patients with a chronic inflammatory demyelinating polyneuropathy (CIDP) and therefore should be regarded as causative for the disease. This variant escapes most routine diagnostic screens for CMT1A, because copy numbers of PMP22 probes were all normal. No indications were found for the involvement of the genes that are located within this duplication. A possible association of this duplication with a mutation in the PMP22 coding regions was also excluded. We suggest that this CNV proximal of the PMP22 gene leads to CMT through an unknown mechanism affecting PMP22 expression. 相似文献
994.
Ali RR; Reichel MB; Thrasher AJ; Levinsky RJ; Kinnon C; Kanuga N; Hunt DM; Bhattacharya SS 《Human molecular genetics》1996,5(5):591-594
Gene transfer to photoreceptor cells may provide a means for arresting the
retinal degeneration that is characteristic of many inherited causes of
blindness, including retinitis pigmentosa (RP). However, transduction of
photoreceptors has to date been inefficient, and further limited by
toxicity and immune responses directed against vector-specific proteins. An
alternative vector system based on adeno- associated virus (AAV) may
obviate these problems, and may be useful for transduction of neuronal
cells. In this study we have demonstrated successful transduction of all
layers of the neuroretina as well as the retinal pigment epithelium (RPE)
following subretinal injection of recombinant AAV particles encoding lac Z.
Furthermore, the efficiency of transduction of photoreceptors is
significantly higher than that achieved with an equivalent adenoviral
vector. This is the first report showing that AAV is capable of transducing
photoreceptor cells and supports the use of this vector system for gene
therapy of retinal diseases such as RP.
相似文献
995.
Microsatellite instability and mutation analysis of hMSH2 and hMLH1 in patients with sporadic, familial and hereditary colorectal cancer 总被引:17,自引:0,他引:17
Moslein G; Tester DJ; Lindor NM; Honchel R; Cunningham JM; French AJ; Halling KC; Schwab M; Goretzki P; Thibodeau SN 《Human molecular genetics》1996,5(9):1245-1252
To date, at least four genes involved in DNA mismatch repair, hMSH2, hMLH1,
hPMS1 and hPMS2, have been demonstrated to be altered in the germline of
patients with hereditary nonpolyposis colorectal cancer (HNPCC).
Additionally, defective mismatch repair is thought to account for the
observation of microsatellite instability (MIN) in tumors from these
patients. The genetic defect responsible for the MIN+ phenotype in sporadic
colorectal cancer, however, has yet to be clearly delineated. In order to
better understand the role of somatic and germline alterations within hMSH2
and hMLH1 in the process of colorectal tumorigenesis, we examined the
entire coding regions of both of these genes in seven patients with MIN+
sporadic colorectal cancer, 19 patients with familial colorectal cancer,
and 20 patients meeting the strict Amsterdam criteria for HNPCC. Thirteen
germline, two somatic, and four neutral alterations were identified. The
two somatic mutations occurred in patients having familial cancer, while
the germline mutations were distributed among one sporadic (14%), three
familial (16%), and nine HNPCC (45%) cases. All patients with identified
mutations in the mismatch repair genes, whose tumors were available for
analysis, demonstrated MIN. On the other hand, we could not identify
mutations in the subset of clinically defined HNPCC patients with MIN
negative tumors nor in the majority (6/7) of MIN+ sporadic tumors.
相似文献
996.
Tissue inhibitors of metalloproteinases (TIMPs) are pleiotropic extracellular proteins. TIMPs are recognized as endogenous regulators of matrix metalloproteinases (MMPs), a large family of extracellular enzymes with proteolytic activities that participate in cellular homeostasis, adaptation, and tissue remodeling. In addition to their roles as endogenous potent MMP inhibitors, accumulating evidence indicates important physiological roles for TIMPs that are independent of their ability to block MMP activities. For instance, MMP-independent actions of TIMP-1 in the central nervous system have been implicated in synaptic plasticity, neuroprotection, oncogenesis, and oligodendrocyte differentiation. Expression of TIMP-1 is dramatically increased in response to a variety of injurious and inflammatory insults. In the context of disease pathogenesis, MMP and TIMP expression are interpreted with respect to the proteolytic consequences of increased MMP/TIMP ratios. Here, we provide an alternative perspective on the homeostatic balance of TIMP and MMP proteins, whereby consideration is given to the possible role of MMPs as cognate inhibitors of the signaling functions of TIMPs. Thus, MMPs may regulate the receptor-mediated actions of TIMPs, inasmuch as TIMPs are themselves inhibitors of MMP-mediated proteolytic activities. This broader view reflects our emerging understanding that TIMP signaling and MMP inhibition represent two important functions of TIMPs that have the potential to affect tissue pathology. 相似文献
997.
Sandra Vosbergen Eva K Laan Ersen B Colkesen Maurice AJ Niessen Roderik A Kraaijenhagen Marie-Louise Essink-Bot Niels Peek 《Journal of medical Internet research》2012,14(5)
Background
Web technology is increasingly being used to provide individuals with health risk assessments (HRAs) with tailored feedback. End-user satisfaction is an important determinant of the potential impact of HRAs, as this influences program attrition and adherence to behavioral advice.Objective
The aim of this study was to evaluate end-user satisfaction with a web-based HRA with tailored feedback applied in worksite settings, using mixed (quantitative and qualitative) methods.Methods
Employees of seven companies in the Netherlands participated in a commercial, web-based, HRA with tailored feedback. The HRA consisted of four components: 1) a health and lifestyle assessment questionnaire, 2) a biometric evaluation, 3) a laboratory evaluation, and 4) tailored feedback consisting of a personal health risk profile and lifestyle behavior advice communicated through a web portal. HRA respondents received an evaluation questionnaire after six weeks. Satisfaction with different parts of the HRA was measured on 5-point Likert scales. A free-text field provided the opportunity to make additional comments.Results
In total, 2289 employees participated in the HRA program, of which 637 (27.8%) completed the evaluation questionnaire. Quantitative analysis showed that 85.6% of the respondents evaluated the overall HRA positively. The free-text field was filled in by 29.7 % of the respondents (189 out of 637), who made 315 separate remarks. Qualitative evaluation of these data showed that these respondents made critical remarks. Respondents felt restricted by the answer categories of the health and lifestyle assessment questionnaire, which resulted in the feeling that the corresponding feedback could be inadequate. Some respondents perceived the personal risk profile as unnecessarily alarming or suggested providing more explanations, reference values, and a justification of the behavioral advice given. Respondents also requested the opportunity to discuss the feedback with a health professional.Conclusions
Most people were satisfied with the web-based HRA with tailored feedback. Sources of dissatisfaction were limited opportunities for providing additional health information outside of the predefined health and lifestyle assessment questionnaire and insufficient transparency on the generation of the feedback. Information regarding the aim and content of the HRA should be clear and accurate to prevent unrealistic expectations among end-users. Involving trusted health professionals in the implementation of web-based HRAs may enhance the use of and confidence in the HRA. 相似文献998.
目的对Crocker等人编制的人际交往目标量表进行修订,并检验修订量表的信效度。方法采用翻译后的人际交往目标量表对432名大学生进行施测。结果信度检验:修订后的总量表、自我形象目标、关爱他人目标维度的内部一致性系数分别为0.852、0.787、0.789,分半信度分别为0.770、0.783、0.745;效度检验:探索性因素分析产生的2个因子共解释38.54%的总方差;验证性因素分析结果显示,模型对于数据的拟合程度良,χ2/df=2.06,RMSEA=0.068,NFI=0.805,CFI=0.887,IFI=0.889,TLI=0.867。结论修订后的人际交往目标量表具有良好的信度和效度,可以在未来的相关领域研究中应用。 相似文献
999.
Human minisatellite MS32 (D1S8) shows instability both in the germline and,
at much lower levels, in somatic DNA. To investigate factors that influence
somatic and germline mutation, large cosmid-based constructs containing
MS32 were introduced into mice, bred to homozygosity and tested for
instability in blood and sperm. Analysis of single copy and multicopy
transgenic lines revealed somatic mutants occurring at a frequency
comparable with that seen in man. As in humans, these mutants arose mainly
by simple intra-allelic duplications and deletions. In contrast, analysis
of sperm DNA from four different transgenic lines showed no trace of the
complex recombination-based germline instability seen in man, even using
PCR-based approaches capable of detecting very rare mutants. These data
provide further evidence that germline and somatic mutation at human
minisatellite MS32 occur via distinct pathways, that a major barrier exists
to the transfer of germline instability from humans to mice and that the
mouse germline appears to be protected from mitotic instability of the type
seen in blood.
相似文献
1000.
In this longitudinal study, we investigated the relationship of birth order
and the age of mother and father to the gender of 1795 newborns (mean +/-
SD 12.5 +/- 1.6 per mother) of 143 grand grand multiparous (i.e women who
have had >10 deliveries). The frequency of boys was 52.2% in the group
of 1st to 9th paras and 46.2% in the group of 10th to 20th paras (P =
0.022). Mothers aged > or =35 years had 7.0% more female than male
newborns (P = 0.024). The respective figure for fathers was 5.6% (P =
0.023). The interpregnancy interval evaluated for 96 mothers with 1091
deliveries had no correlation with the gender of the infants. In the
stepwise logistic regression analysis, the age of the mothers remained the
only significant independent factor for the shift from a male to a female
majority in the newborns (P = 0.0389). The present data thus indicate that
the age of the mother is the factor which explains why grand grand
multiparous women deliver more girls than boys.
相似文献