全文获取类型
收费全文 | 26359篇 |
免费 | 1330篇 |
国内免费 | 937篇 |
专业分类
耳鼻咽喉 | 155篇 |
儿科学 | 521篇 |
妇产科学 | 337篇 |
基础医学 | 3939篇 |
口腔科学 | 539篇 |
临床医学 | 1770篇 |
内科学 | 4051篇 |
皮肤病学 | 394篇 |
神经病学 | 2915篇 |
特种医学 | 491篇 |
外国民族医学 | 3篇 |
外科学 | 1614篇 |
综合类 | 3475篇 |
预防医学 | 1075篇 |
眼科学 | 236篇 |
药学 | 4762篇 |
3篇 | |
中国医学 | 1017篇 |
肿瘤学 | 1329篇 |
出版年
2023年 | 159篇 |
2022年 | 362篇 |
2021年 | 435篇 |
2020年 | 445篇 |
2019年 | 878篇 |
2018年 | 771篇 |
2017年 | 620篇 |
2016年 | 535篇 |
2015年 | 575篇 |
2014年 | 1042篇 |
2013年 | 1348篇 |
2012年 | 1137篇 |
2011年 | 1319篇 |
2010年 | 1262篇 |
2009年 | 1238篇 |
2008年 | 1303篇 |
2007年 | 1220篇 |
2006年 | 1124篇 |
2005年 | 920篇 |
2004年 | 964篇 |
2003年 | 933篇 |
2002年 | 743篇 |
2001年 | 729篇 |
2000年 | 613篇 |
1999年 | 620篇 |
1998年 | 512篇 |
1997年 | 438篇 |
1996年 | 384篇 |
1995年 | 298篇 |
1994年 | 274篇 |
1993年 | 226篇 |
1992年 | 172篇 |
1991年 | 171篇 |
1990年 | 136篇 |
1989年 | 151篇 |
1988年 | 100篇 |
1986年 | 107篇 |
1985年 | 460篇 |
1984年 | 622篇 |
1983年 | 489篇 |
1982年 | 459篇 |
1981年 | 443篇 |
1980年 | 351篇 |
1979年 | 321篇 |
1978年 | 227篇 |
1977年 | 173篇 |
1976年 | 193篇 |
1975年 | 188篇 |
1974年 | 152篇 |
1973年 | 143篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
51.
The serum levels of IgE, IgG, IgA, and IgM of 27 American-born Filipino children 5 to 17 years of age were measured and found to be significantly higher than those of a control group of 24 Caucasian children of similar age distribution and attending the same general pediatric clinics. The geometric mean of serum IgE of the Filipinos was 227 U. per milliliter and of the Caucasians, 69 U. per milliliter (p < 0.01). The geometric means of other serum immunoglobulin levels of the Filipinos by comparison with the Caucasians were: IgG, 1,303 and 1,010 mg. per 100 ml. (p < 0.01); IgA, 195 and 120 mg. per 100 ml. (p < 0.001); and IgM, 141 and 92 mg. per 100 ml. (p < 0.02), respectively. The incidence of atopic disease was higher in the Filipino study group (48 per cent) than in the Caucasian control group (25 per cent); eczema was especially prevalent in the Filipino group. Elevated serum IgE levels were associated with atopic disease in both racial groups; however, there was no correlation between serum level of IgG, IgA, or IgM and atopy. 相似文献
52.
Reuben P. Siraganian M.D. Ph.D. Ann L. Sandberg Ph.D. 《The Journal of allergy and clinical immunology》1979,63(6):435-442
The major allergens present in mouse skin, serum, and urine have been identified. Skin extracts, serum, and urine were chromatographed, and the activities of the fractions were monitored by histamine release from the leukocytes of individuals sensitive to mice. Fractionation of skin extracts revealed two major allergens. The large allergen has a molecular weight of approximately 67,000 daltons and by biochemical and immunochemical criteria appears to be identical to mouse albumin. The smaller molecular weight allergen is approximately 17,000 daltons. The same two allergens are also found in mouse serum and mouse urine. Histamine release by leukocytes of individuals allergic to mice demonstrated that some individuals react predominantly to the large allergen, some to the small allergen, and one group of patients reacts to both allergens. 相似文献
53.
Arterial spasm was induced by application of calcium chloride to the adventitial surface of the rabbit common carotid artery in vivo. Sodium chloride (NaCl) was applied to the contralateral vessel as control. Vessels were fixed in situ by intravascular perfusion after 15 min, 1 hr, or 24 hr and prepared for light and scanning electron microscopy (SEM). With SEM, the luminal surface at the site of calcium application showed severe longitudinal folding accompanied by endothelial desquamation with extensive platelet deposition on exposed subendothelium. The luminal cross-sectional area was reduced by 53 +/- 19.5% after 15 min and by 44 +/- 12% after 1 hr as compared with the contralateral control. Furthermore, the luminal area at the site of calcium application was found to be reduced by 42 +/- 8% after 1 hr when compared with segments of the same vessel distal to the site of calcium application. Blood flow rate, as measured by electromagnetic flow probe, was not reduced. Vessels examined after 24 hr showed a significant increase in luminal cross-sectional area as compared with contralateral control vessels (136 +/- 70%). Control vessels (NaCl) showed no significant change in luminal cross-sectional area and no endothelial desquamation or platelet deposition after 15 min, 1 hr, or 24 hr. Examination of histologic sections showed calcium precipitation within the attached thrombus after 15 min with calcium deposits also adherent to the adjacent luminal aspect of the internal elastic lamina (IEL). By 24 hr, this precipitation extended throughout the media. Marked deposition of leukocytes was seen after 24 hr which showed a preferential attachment for areas of endothelial damage and discontinuity of IEL. 相似文献
54.
Narayan P. Verma Cynthia D. Nichols Manfred F. Greiffenstein Rajinder P. Singh Deborah Hurst-Gordon 《Brain topography》1989,1(3):183-191
Summary Thirty subjects (normal controls, patients with putative subcortical dementia and non-demented patient controls) were studied using advanced neurophysiological (16 scalp-electrode positions, computer-assisted brain electrical activity mapping, auditory oddball paradigm) and neuropsychological techniques. Our study suggests that waves earlier than P3 (N1, P2 and N2) are all correlated with global measures of cognitive functions. They are, however, differentially correlated with specific measures of cognitive functions, N1 and P2 with mental speed and N2 with short-term memory. The abnormalities of these waves (earlier than P3) may be an electrophysiologic marker of dementia in patients with putative subcortical states. 相似文献
55.
The biologically active substance P (SP) N-terminal metabolite SP1–7 has been reported to modulate several neural processes such as learning, locomotor activity and reaction to opioid withdrawal. Although all these processes are believed to be associated with dopaminergic transmission no evidence of an interaction between SP1–7 and dopamine in the case of morphine withdrawal has so far been reported. Therefore, in this work we applied in vivo microdialysis to investigate the effect of SP1–7 injection into the ventral tegmental area on dopamine release in nucleus accumbens of male rats during naloxone precipitated morphine withdrawal. The result showed that the heptapeptide enhances dopamine release and also elevates the level of the dopamine metabolite dihydroxyphenylacetic acid in this brain area. It was suggested that the observed action of the SP fragment on the dopamine system represents the underlying mechanism for a previously observed ability of SP1–7 to counteract the aversion response to morphine withdrawal. 相似文献
56.
C Arbesman I L Bernstein C W Bierman J S Bocles R Katz P L Lieberman K Mattucci E O Meltzer E Middleton J Noyes D S Pearlman H L Pence R G Slavin S L Spector 《The Journal of allergy and clinical immunology》1983,71(6):597-603
Fluocortin butyl (FCB) is a newly synthesized corticosteroid with a high ratio of topical to systemic activity. FCB was studied in a multi-center, double-blind, placebo-controlled trial of therapy of perennial rhinitis. The study was conducted between January and May 1981. Patients evaluated suffered from either chronic allergic or chronic nonallergic rhinitis or both. A total of 306 patients from 16 investigative centers were evaluated by comparing FCB to placebo. Three separate dosage regimens were employed. Patients received a total daily dose of 2, 4, or 8 mg. FCB was found to be an effective therapeutic agent. It reduced symptoms of nasal congestion, rhinorrhea, postnasal drainage, and sneezing. It also markedly reduced the use of concomitant medications (chlorpheniramine maleate and/or pseudoephedrine). Relief of symptoms was noted as early as the first week of therapy, and the degree of improvement increased progressively during the study. There was little difference between the relief produced by the 4 mg and 8 mg regimens. Both of these were superior to the 2 mg regimen. The drug was well tolerated; no significant side effects were noted. 相似文献
57.
J W Larrick C E Buckley C E Machamer G D Schlagel J A Yost J Blessing-Moore D Levy 《The Journal of allergy and clinical immunology》1983,71(2):184-188
The Waorani Indians of eastern Ecuador have the highest blood concentration of IgE reported in a human population. Evidence obtained by medical history, physical examination, and immediate hypersensitivity skin tests suggests that pollen allergy and other atopic diseases are rare among the Waorani. A similar association between parasite-induced hyperimmunoglobulinemia-E and a low prevalence of conventional atopic disease has been reported in numerous other tropical populations. Saturation of mast cell IgE receptors with antibodies directed to the parasite and/or other antigens and competitive inhibition of passive binding of pollen allergen-specific IgE is one hypothetical cause of this association. We have tested this interesting conjecture by passively sensitizing the skin of Waorani Indians with serum containing pollen allergen-specific IgE antibodies. Waorani Indians with hyperimmunoglobulinemia-E can be adoptively sensitized with human ragweed or rye grass hyperimmune IgE antisera. This suggests that the cutaneous mast cells of healthy Waorani have active IgE receptors. The high circulating plasma concentrations of IgE in the Waorani do not prevent adoptive cutaneous sensitization with pollen-specific IgE antibodies. 相似文献
58.
All-night sleep EEG and auditory evoked responses (AERs) were recorded in 8 children whose ages ranged from 27 to 60 months. EEG intensity was measured by means of a Drohocki-type integrator. Two measures of evoked response amplitude were calculated: the peak-to-peak amplitude of the P2N2 component, and a multiple-component amplitude measure of the first 500 msec of the response. Both amplitude measurements were found to correlate well with each other. Changes in EEG intensity between subjects were not correlated with changes in AER amplitude, but a number of correlations between AER amplitude and EEG intensity were found within individual subjects. Further analysis suggested the latter finding might be a result of the presence of “unaveraged’EEG in individual AER plots. It is concluded that little correlation exists between AER amplitude and EEG intensity in children during sleep. 相似文献
59.
Purification of P-selectin (CD62P) from human platelets 总被引:1,自引:0,他引:1
Summary A method is described for immunoaffinity purification of P-selectin from outdated human platelets. 相似文献
60.
Chen T Mittelstaedt RA Aidoo A Hamilton LP Beland FA Casciano DA Heflich RH 《Environmental and molecular mutagenesis》2001,37(3):195-202
N-Hydroxy-2-acetylaminofluorene (N-OH-AAF) is the proximate carcinogenic metabolite of the powerful rat liver carcinogen 2-acetylaminofluorene. In this study, transgenic Big Blue(R) rats were used to examine the relationship between in vivo mutagenicity and DNA adduct formation by N-OH-AAF in the target liver compared with that in nontarget tissues. Male rats were given one, two, or four doses of 25 mg N-OH-AAF/kg body weight by i.p. injection at 4-day intervals, and groups of treated and control rats were euthanized up to 10 weeks after beginning the dosing. Mutant frequencies were measured in the spleen lymphocyte hprt gene, and lacI mutant frequencies were determined in the liver and spleen lymphocytes. At 6 weeks after beginning the dosing, the hprt mutant frequency in spleen lymphocytes from the four-dose group was 16.5 x 10(-6) compared with 3.2 x 10(-6) in control animals. Also at 6 weeks, rats given one, two, or four doses of N-OH-AAF had lacI mutant frequencies in the liver of 97.6, 155.6, and 406.8 x 10(-6), respectively, compared with a control frequency of 25.7 x 10(-6); rats given four doses had lacI mutant frequencies in spleen lymphocytes of 55.8 x 10(-6) compared with a control frequency of 20.4 x 10(-6). Additional rats were evaluated for DNA adduct formation in the liver, spleen lymphocytes, and bone marrow by (32)P-postlabeling. Adduct analysis was conducted 1 day after one, two, and four treatments with N-OH-AAF, 5 days after one treatment, and 9 days after two treatments. N-(Deoxyguanosin-8-yl)-2-aminofluorene was the major DNA adduct identified in all the tissues examined. Adduct concentrations increased with total dose to maximum values in samples taken 1 day after two doses, and remained essentially the same after four doses. In samples taken after four doses, adduct levels were 103, 28, and 7 fmol/microg of DNA in liver, spleen lymphocytes, and bone marrow, respectively. The results indicate that the extent of both DNA adduct formation and mutant induction correlates with the organ specificity for N-OH-AAF carcinogenesis in the rat. Environ. Mol. Mutagen. 37:195-202, 2001. Published 2001 Wiley-Liss, Inc. 相似文献