全文获取类型
收费全文 | 23995篇 |
免费 | 1304篇 |
国内免费 | 268篇 |
专业分类
耳鼻咽喉 | 473篇 |
儿科学 | 328篇 |
妇产科学 | 268篇 |
基础医学 | 4332篇 |
口腔科学 | 557篇 |
临床医学 | 1913篇 |
内科学 | 4543篇 |
皮肤病学 | 893篇 |
神经病学 | 1806篇 |
特种医学 | 1448篇 |
外科学 | 2947篇 |
综合类 | 163篇 |
现状与发展 | 1篇 |
一般理论 | 5篇 |
预防医学 | 1076篇 |
眼科学 | 450篇 |
药学 | 2093篇 |
中国医学 | 287篇 |
肿瘤学 | 1984篇 |
出版年
2023年 | 148篇 |
2022年 | 510篇 |
2021年 | 810篇 |
2020年 | 405篇 |
2019年 | 570篇 |
2018年 | 646篇 |
2017年 | 527篇 |
2016年 | 733篇 |
2015年 | 1086篇 |
2014年 | 1296篇 |
2013年 | 1442篇 |
2012年 | 2160篇 |
2011年 | 2045篇 |
2010年 | 1166篇 |
2009年 | 1051篇 |
2008年 | 1457篇 |
2007年 | 1339篇 |
2006年 | 1144篇 |
2005年 | 1008篇 |
2004年 | 867篇 |
2003年 | 756篇 |
2002年 | 650篇 |
2001年 | 574篇 |
2000年 | 472篇 |
1999年 | 396篇 |
1998年 | 193篇 |
1997年 | 144篇 |
1996年 | 101篇 |
1995年 | 106篇 |
1994年 | 74篇 |
1993年 | 60篇 |
1992年 | 143篇 |
1991年 | 150篇 |
1990年 | 117篇 |
1989年 | 131篇 |
1988年 | 112篇 |
1987年 | 118篇 |
1986年 | 106篇 |
1985年 | 101篇 |
1984年 | 67篇 |
1983年 | 63篇 |
1982年 | 48篇 |
1981年 | 45篇 |
1980年 | 39篇 |
1979年 | 48篇 |
1978年 | 58篇 |
1977年 | 49篇 |
1976年 | 36篇 |
1974年 | 30篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
123I-MIBG myocardial scintigraphy as a noninvasive screen for the diagnosis of coronary artery spasm
Jong-Won Ha Jong-Doo Lee Yangsoo Jang Namsik Chung June Kwan Se-Joong Rim Young-Joon Lee Won-Heum Shim Seung-Yun Cho Sung-Soon Kim 《Journal of nuclear cardiology》1998,5(6):591-597
Background It has been suggested that the sympathetic nervous system might play an important role in the development of coronary artery
spasm. However, no cardiac imaging modality has been able to demonstrate abnormal sympathetic innervation in patients with
coronary artery spasm. The purpose of this study was to assess the presence and location of abnormal sympathetic innervation
using iodine 123-metaiodobenzylguanidine (123I-MIBG) single photon emission computed tomography (SPECT) and to evaluate the clinical efficacy of 123I-MIBG SPECT as a noninvasive screening test in patients with coronary artery spasm.
Methods and Results Coronary arteriography and a provocative test with intravenous administration of ergonovine maleate were performed in 26 patients
(20 men, 6 women, mean age 48.2±12.0 years, range 20 to 67 years) who were suspected of having a coronary artery spasm. The
subjects were divided into 2 groups: group 1 (n=18) comprised subjects with negative provocative provocative test result,
and group 2 (n=8) comprised subjects with negative provocative test results. Ten healthy subjects served as controls. No abnormal
MIBG uptake was observed in the control subjects. Abnormal sympathetic nervous innervation using 123I-MIBG SPECT was observed either as a reduced uptake or a defective pattern in the perfused areas in 13 of the 18 regions
supplied by vessels of ergonovine-induced vasospasm. Normal sympathetic innervation, as evidenced by normal 123I-MIBG uptake, was noted in all of the 60 segments of normal vessel territories. Reduced uptake of 123I-MIBG was not detected in the perfused areas of 5 vasospasm-induced vessels (perfusion territory of left anterior descending
coronary artery [LAD] and the right coronary artery [RCA] in 2 and 3 patients, respectively). The sensitivity and specificity
of 123I-MIBG for detection of coronary artery spasm were 72.2% (95% confidence interval, [CI] 55% to 89%) and 100%, respectively.
The positive predictive and negative predictive values were 100% and 92.3% (95% CI 91% to 93%), respectively.
Conclusion
123I-MIBG SPECT is a feasible method to evaluate noninvasively and localize the territories of coronary arteries with spasm.
Invasive diagnostic coronary arteriography with ergonovine provocation test may be unnecessary for diagnosis of coronary artery
spasm in patients with typical resting pain, negative exercise test or normal thallium perfusion scan results, but showing
abnormalities in 123I-MIBG SPECT.
Presented in part at the European Association of Nuclear Medicine Congress, September 1996, Copenhagen, Denmark. 相似文献
42.
Genotype-phenotype correlation for nucleotide substitutions in the IgII- IgIII linker of FGFR2 总被引:6,自引:3,他引:3
43.
44.
Chest radiographs and chest computed tomography (CT) scans were compared in 203 patients with newly diagnosed Hodgkin disease. The incidence of positive findings was tabulated from six intrathoracic lymph node groups, lung parenchyma, pericardium, pleura, and chest wall. The discordant cases were assessed to determine impact on clinical management. The CT scans provided additional evidence of disease involvement, ranging from 0% to 15% at each of the designated anatomic sites. Treatment was altered in 9.4% of all patients (19 of 203), including 13.8% (nine of 65) of those undergoing radiation therapy alone and 8.2% (ten of 122) of those undergoing combined-modality treatment. We conclude that routine chest CT examinations are valuable in the clinical management of those patients for whom radiation therapy is planned. 相似文献
45.
Uroscopy in the 21st century: high-field NMR spectroscopy 总被引:1,自引:1,他引:0
Neild GH; Foxall PJ; Lindon JC; Holmes EC; Nicholson JK 《Nephrology, dialysis, transplantation》1997,12(3):404-417
From the experiments described, it can be seen that there are different
research approaches that can be taken and these are summarized in Table 1.
Whereas much scientific research is principally hypothesis led, there
remains, nevertheless, an important place for exploratory research. High
resolution NMR can measure, directly and simultaneously, a wide range of
endogenous metabolites in biological fluids and has the unique capability
of providing structural information on the metabolites detected. It has
proved to be a powerful research tool with which to study inherited
metabolic diseases, renal disease, drug metabolism, and toxicity, and can
be used to monitor the effects of drug therapy. For instance, by using a
library of experimental toxins one can map the metabolic profile of
site-specific nephron injury. With this approach in man one could
eventually take an unknown disease such as Balkan nephropathy and predict
the initial site of tubular injury, the mode of injury and therefore the
kind of toxin capable of producing that injury. NMR spectroscopic
techniques are still advancing rapidly, with ever increasing sensitivity
and sophistication of NMR pulse sequences to enhance structural elucidation
in complex mixtures. Given the advances in directly coupled HPLC-NMR and
even HPLC-NMR-mass spectroscopy it is likely that these technologies in
conjunction with pattern recognition will make major contribution to our
understanding of renal processes and provide new diagnostic insights in the
21st century.
相似文献
46.
Molecular characterization of the mosquito vitellogenin receptor reveals unexpected high homology to the Drosophila yolk protein receptor. 总被引:2,自引:0,他引:2 下载免费PDF全文
T W Sappington V A Kokoza W L Cho A S Raikhel 《Proceedings of the National Academy of Sciences of the United States of America》1996,93(17):8934-8939
The mosquito (Aedes aegypti) vitellogenin receptor (AaVgR) is a large membrane-bound protein (214 kDa when linearized) that mediates internalization of vitellogenin, the major yolk-protein precursor, by oocytes during egg development. We have cloned and sequenced two cDNA fragments encompassing the entire coding region of AaVgR mRNA, to our knowledge the first insect VgR sequence to be reported. The 7.3-kb AaVgR mRNA is present only in female germ-line cells and is abundant in previtellogenic oocytes, suggesting that the AaVgR gene is expressed early in oocyte differentiation. The deduced amino acid sequence predicts a 202.7-kDa protein before posttranslational processing. The AaVgR is a member of the low density lipoprotein receptor superfamily, sharing significant homology with the chicken (Gallus gallus) VgR and particularly the Drosophila melanogaster yolk protein receptor, in spite of a very different ligand for the latter. Distance-based phylogenetic analyses suggest that the insect VgR/yolk protein receptor lineage and the vertebrate VgR/low density lipoprotein receptor lineage diverged before the bifurcation of nematode and deuterostome lines. 相似文献
47.
Camus Kar Man Choy Pauline Cho Wai-Yuen Chung Iris F F Benzie 《Optometry and vision science》2003,80(9):632-636
BACKGROUND: Tear ascorbate is important for corneal health. A rapid and simple method for measurement of ascorbate in tears is needed, and adequate knowledge of physiological variation of tear ascorbate is important to facilitate comparative studies of the effect of, for example, contact lens wear and environmental conditions and stresses. However, there are currently no data on physiological variation of tear ascorbate. This study validated a simple and speedy method for tear ascorbate and investigated between-eye and between-day variation in tear ascorbate in healthy young adults. METHODS: Yawn-induced reflex tears were collected from 32 healthy Hong Kong Chinese subjects and measured by both high-performance liquid chromatography (HPLC) and by an enzyme-linked colorimetric method known as FRASC (total ferric reducing (antioxidant) activity and ascorbate concentration measurement). For between-eye variation, yawn reflex tears were collected from each eye of the same 32 healthy subjects, and ascorbate was measured using HPLC; in a separate experiment for between-day variation, tears were collected on two separate days from 14 subjects, and ascorbate was measured by FRASC. RESULTS: Both HPLC and FRASC showed high precision, and results obtained using FRASC were not statistically different from those using HPLC; mean +/- SD were, respectively, 18.5 +/- 4.4 microM and 18.5 +/- 4.8 microM for HPLC and FRASC methods (p = 0.943). No significant between-eye difference in tear ascorbate was found (p = 0.386), and no significant between-day variation was found overall: mean +/- SD ascorbate was 20.0 +/- 6.2 microM on day 1 and 19.3 +/- 6.8 microM on day 2 (p = 0.772). However, between-day variation was large in seven of 14 subjects. CONCLUSION: FRASC is an acceptable alternative to HPLC for measurement of tear ascorbate. Tears for ascorbate investigation can be collected from either eye or, if necessary, from both eyes and pooled. However, tear ascorbate may vary widely from day to day in the same individual. The reasons for this variation require further study but may relate to differences in ascorbate supply or demand within the precorneal tear layer. 相似文献
48.
A 12-year-old girl with a history of fast myopia progression underwent advanced orthokeratology (ortho-k) treatment and suffered from recurrent lens binding and central corneal staining. The problem could not be fixed by lens fenestration and refitting with a less aggressive lens (three-zone ortho-k) design. After refitting with a lower target advanced ortho-k lens, these complications were no longer occurring, and the amount of power reduction was greater than expected considering the target designed for the refitted lenses. During the following 15 months of ortho-k lens wear, there was no clinically significant change to her refractive error. The patient and her parents were happy with the outcome, although the refractive error was not totally eliminated and she still needed to wear spectacles for clear vision. Possible etiologies of the complications are discussed. 相似文献
49.
Persistence of the sciatic artery (SA) is a rare vascular anomaly, resulting from lack of regression of an embryonal artery to the lower extremity. Forty-nine cases have been published in the world literature since 1832. The persistent sciatic artery (PSA) is particularly prone to undergo aneurysm formation or atherosclerosis. It originates from the internal iliac artery, courses in close proximity to the sciatic nerve, and provides the main supply to the popliteal artery because a hypoplastic superficial femoral artery (SFA), contributing only collaterals to the knees, is usually associated with a PSA. This anomaly should be kept in mind in the clinical assessment of a pulsatile gluteal mass. It also presents a potential hazard during hip and renal transplant surgery. 相似文献
50.
Introduction : Hypertrophic scar is a devastating sequel to burns and other tangential skin injuries. It follows deep dermal injuries and does not occur after superficial injuries. Nitric oxide (NO) plays many important roles in wound healing from inflammation to scar remodeling. Studies have shown that expression of nitric oxide synthase and nitric oxide production are decreased in human hypertrophic scar. However little is known about NO involvement in the early stages of hypertrophic scarring, because of the lack of an animal model. It was recently reported that the female red Duroc pig (FRDP) makes thick scar, which is similar to human hypertrophic scar. We hypothesized that NO production in wounds on the female, red Duroc pig is similar to that of human hypertrophic scar and that NO involvement in deep wounds is different from that in superficial wounds. Methods : Superficial (0.015” to 0.030”) and deep (0.045” to 0.060”) wounds were created on the backs of four FRDPs. Biopsies were collected at weeks 1.5, 4, 8 and 21 post wounding including samples of uninjured skin. Nitric oxide levels were measured with the Griess reaction assay and normalized with tissue protein level. Results : Superficial wounds healed with an invisible scar whereas the deep wounds healed with scar resembling mild hypertrophic scar. The thickness of the scars from the deep wounds was significantly greater than uninjured skin and healed superficial wounds (p < 0.01). NO levels were increased at 1.5 weeks in deep wounds compared to superficial wounds and uninjured skin (p < 0.05). At 8 weeks, NO levels in deep wounds had returned to the level of uninjured tissue and superficial wounds. By 21 weeks, NO levels had decreased significantly when compared to superficial wounds (p < 0.01). There were no differences in NO levels between uninjured skin and superficial wounds at any time point (p > 0.05). Conclusions : NO production is similar in late, deep wounds on the female, red Duroc pig to that reported in the literature for human hypertrophic scar further validating this animal model. NO production is quite different after deep wounds as compared to superficial wounds in the FRDP. Early elevation in nitric oxide production might account for excessive inflammation in deep wounds that become thick scars in the FRDP. Nitric oxide regulators and effects at early stages of scar formation should be elucidated further and the FRDP appears to be a useful model. 相似文献