全文获取类型
收费全文 | 4186篇 |
免费 | 368篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 133篇 |
妇产科学 | 105篇 |
基础医学 | 583篇 |
口腔科学 | 34篇 |
临床医学 | 526篇 |
内科学 | 1100篇 |
皮肤病学 | 74篇 |
神经病学 | 287篇 |
特种医学 | 294篇 |
外科学 | 698篇 |
综合类 | 41篇 |
一般理论 | 1篇 |
预防医学 | 209篇 |
眼科学 | 28篇 |
药学 | 262篇 |
肿瘤学 | 179篇 |
出版年
2021年 | 54篇 |
2020年 | 37篇 |
2019年 | 53篇 |
2018年 | 63篇 |
2017年 | 63篇 |
2016年 | 56篇 |
2015年 | 64篇 |
2014年 | 99篇 |
2013年 | 146篇 |
2012年 | 180篇 |
2011年 | 209篇 |
2010年 | 125篇 |
2009年 | 117篇 |
2008年 | 165篇 |
2007年 | 192篇 |
2006年 | 195篇 |
2005年 | 178篇 |
2004年 | 161篇 |
2003年 | 160篇 |
2002年 | 139篇 |
2001年 | 140篇 |
2000年 | 140篇 |
1999年 | 125篇 |
1998年 | 61篇 |
1997年 | 68篇 |
1996年 | 44篇 |
1995年 | 41篇 |
1994年 | 48篇 |
1993年 | 41篇 |
1992年 | 84篇 |
1991年 | 79篇 |
1990年 | 67篇 |
1989年 | 87篇 |
1988年 | 77篇 |
1987年 | 72篇 |
1986年 | 68篇 |
1985年 | 80篇 |
1984年 | 46篇 |
1983年 | 42篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1979年 | 70篇 |
1978年 | 40篇 |
1977年 | 38篇 |
1976年 | 37篇 |
1975年 | 26篇 |
1974年 | 35篇 |
1973年 | 40篇 |
1972年 | 39篇 |
1971年 | 34篇 |
排序方式: 共有4581条查询结果,搜索用时 15 毫秒
1.
2.
3.
For many parents stopping life-sustaining medical treatment on their dying infant is psychologically impossible. Dostoevsky's insights into human behavior, particularly the fact that individuals do not want the anxiety and guilt associated with responsibility for making difficult decisions, might change the way physicians approach parents for permission to withdraw life-prolonging medical interventions on dying infants. 相似文献
4.
Confounders contributing to the reported associations of coffee or caffeine with disease 总被引:2,自引:0,他引:2
G B Schreiber M Robins C E Maffeo M N Masters A P Bond D Morganstein 《Preventive medicine》1988,17(3):295-309
The role of caffeine or coffee in causing or promoting the incidence of serious disease is equivocal. Two design factors may account for the discrepancies in reported findings on the effects of coffee drinking: (a) imprecision of measurement and (b) confounding variables. A study of 2,714 white U.S. adults disclosed that, of 32 risk factors analyzed by linear and logistic regression, only sex and cigarette smoking were found to be important potential confounders of caffeine and coffee intake. Partial R2 values of the other 30 risk factors were relatively small and were inconsistent for each sex. It is unlikely that any of these factors could explain any of the reported associations between caffeine or coffee consumption and certain diseases. However, certain weak associations with caffeine or coffee intake should be included in the study design when they are known to be risk factors of a disease under investigation. These factors for men are dietary fat intake, vitamin C intake, and body mass index; and for women are vitamin use, alcohol intake, stress, and perceived health status. 相似文献
5.
S S Schreiber S Maren G Tocco T J Shors R F Thompson 《Brain research. Molecular brain research》1991,11(1):89-91
In the present study we examined the relationship between the induction of long-term potentiation (LTP) in the dentate gyrus of anesthetized rats and activation of immediate early genes (IEGs; c-fos and zif/268) using several different high-frequency stimulation paradigms. Stimulation parameters that effectively induced LTP were not associated with IEG activation. Conversely, stimulation parameters that failed to induce LTP consistently resulted in IEG activation. These results suggest that there is a negative correlation between IEG activation and LTP, and that activation of IEGs is neither necessary nor sufficient for the induction of LTP. 相似文献
6.
H Atlan R Sigal H Hadar R Chisin I Cohen A Lanir M Soudry Y Machtey R Schreiber J Benmair 《Journal of nuclear medicine》1986,27(2):207-215
Thirty-two patients with diversified pathology were examined with a supraconductive NMR imager using spin echo with different TR and TE to obtain T1 and T2 weighted images. They included 20 tumors (12 primary, eight metastasis), six osteomyelitis, three fractures, two osteonecrosis, and one diffuse metabolic (Gaucher) disease. In all cases except for the stress fractures, the bone pathology was clearly visualized in spite of the normal lack of signal from the compact cortical bone. Nuclear magnetic resonance (NMR) imaging proved to be at least as sensitive as radionuclide scintigraphy but much more accurate than all other imaging procedures including computed tomography (CT) and angiography to assess the extension of the lesions, especially in tumors extended to soft tissue. This is due both to easy acquisition of sagittal and coronal sections and to different patterns of pathologic modifications of T1 and T2 which are beginning to be defined. It is hoped that more experience in clinical use of these patterns will help to discriminate between tumor extension and soft-tissue edema. We conclude that while radionuclide scintigraphy will probably remain the most sensitive and easy to perform screening test for bone pathology, NMR imaging, among noninvasive diagnostic procedures, appears to be at least as specific as CT. In addition, where the extension of the lesions is concerned, NMR imaging is much more informative than CT. In pathology of the spine, the easy visualization of the spinal cord should decrease the need for myelography. 相似文献
7.
G Fitze J Cramer A Serra M Schreiber D Roesner H K Schackert 《Zeitschrift für Kinderchirurgie》2003,13(3):152-157
Hirschsprung disease (HSCR) is considered a model for a complex inheritance disorder. Several genes, including the major HSCR-susceptibility RET proto-oncogene, play an aetiological role in the development of HSCR. Genetic linkage analysis in familial HSCR with both long- and short-segment phenotypes has demonstrated a tight linkage to the RET locus, while the phenotype within a HSCR family is characterised by an incomplete penetrance or a variable extension of the aganglionosis. Therefore, additional genetic alterations of RET are postulated in the aetiology or modification of the HSCR phenotype. In this study, the coding region of all 21 exons of the RET proto-oncogene, including the flanking intronic sequences, were investigated by direct DNA sequencing in a HSCR population. We genotyped the c.135 G/A polymorphism and resolved haplotypes comprising the mutation locus and the c.135 G/A polymorphism. Twenty different mutations were detected in 18 of 76 HSCR patients. In ten families the mutations were inherited from the parents, while only four patients had a positive family history for the disease. Moreover, in all ten families an incomplete penetrance of the HSCR phenotype was observed. We have investigated the effect of the non-mutated wild-type allele as well as the c.135 G/A polymorphism on the phenotype within the HSCR families. Our findings support the notion that both RET alleles are involved in the pathogenesis of a subgroup of HSCR patients in a dose-dependent fashion. Additionally, we have shown a modifying effect of the c.135 G/A polymorphism on the HSCR phenotype within HSCR families. 相似文献
8.
Holger F. Boehm Felix Eckstein Caecilia Wunderer Volker Kuhn Eva-Maria Lochmueller Karin Schreiber Dirk Mueller Ernst J. Rummeny Thomas M. Link 《Journal of clinical densitometry》2005,8(4):488-494
We tested the hypothesis that bone mineral density (BMD) and bone mineral content (BMC) in proximal human femur specimens in the upper neck region of interest (ROI) and femoral neck axis length (FNAL) provide a significantly better prediction of femoral bone strength than standard ROIs in vitro. BMD and BMC were measured in 110 proximal femur specimens using a standard dual-energy X-ray absorptiometry (DXA) scanner. The analysis included a new ROI in the upper neck as well as the standard ROIs. FNAL was obtained from the scan images. The specimens' failure-load was measured in a mechanical loading device, simulating a fall on the greater trochanter. For the standard ROIs, correlations between failure-load and BMD ranged from R2 = 0.64 (shaft ROI) to R2 = 0.70, p < 0.001 (femoral neck). Prediction of strength by BMD did not significantly differ from those of BMC (R2 ranging from 0.65 to 0.75, p < 0.001). In the upper neck ROI, for both BMD and BMC correlations with failure-load were higher (R2 = 0.76 and 0.81, respectively; p < 0.001). A lower, yet still significant, correlation was found between FNAL and bone strength (R2 = 0.23, p < 0.001). Normalization of failure-load with respect to FNAL did not significantly increase the correlations with densitometric measures. This study provides in vitro evidence indicating that among the ROIs of the proximal femur the newly defined upper neck ROI provides the best prediction of bone strength. Only a weak association was observed between failure load and FNAL. 相似文献
9.
We describe a fluorescence method for screening and quantifying urinary porphyrins. New and effective approaches are used to oxidize prophyrinogens, correct the baseline, and ensure that uroporphyrin (uro) and coproporphyrin (copro) are equally detected, mole for mole. No preliminary purification is required. A 45-microL aliquot of urine is oxidized with 3 mmol/L iodine in 3 mol/L HCl to convert porphyrinogens to porphyrins, and then decolorized with 5 mL of 0.45 mmol/L sodium thiosulfate. An excitation scan is done from 350 nm to 440 nm, monitoring emission at 650 nm. Total porphyrin content is determined at the isosbestic point for uro and copro, and the mole fractions of uro and copro are estimated from the wavelength of the signal maximum. There is no interference from protein, glucose, bilirubin, or hemoglobin in high concentration. The limit of detection is less than 30 nmol/L and linearity is maintained up to 3200 nmol/L. Recoveries and precision are excellent. This is a rapid, sensitive screen for porphyrinuria as well as an accurate and precise quantitative method. We compared the method with existing methods and discuss some shortcomings common to many of them. 相似文献
10.