全文获取类型
收费全文 | 7533篇 |
免费 | 837篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 118篇 |
儿科学 | 221篇 |
妇产科学 | 424篇 |
基础医学 | 1269篇 |
口腔科学 | 148篇 |
临床医学 | 991篇 |
内科学 | 1167篇 |
皮肤病学 | 108篇 |
神经病学 | 707篇 |
特种医学 | 311篇 |
外科学 | 793篇 |
综合类 | 228篇 |
一般理论 | 11篇 |
预防医学 | 781篇 |
眼科学 | 156篇 |
药学 | 448篇 |
中国医学 | 5篇 |
肿瘤学 | 490篇 |
出版年
2021年 | 103篇 |
2020年 | 79篇 |
2019年 | 91篇 |
2018年 | 125篇 |
2017年 | 81篇 |
2016年 | 133篇 |
2015年 | 99篇 |
2014年 | 150篇 |
2013年 | 233篇 |
2012年 | 344篇 |
2011年 | 403篇 |
2010年 | 195篇 |
2009年 | 181篇 |
2008年 | 347篇 |
2007年 | 310篇 |
2006年 | 330篇 |
2005年 | 335篇 |
2004年 | 340篇 |
2003年 | 289篇 |
2002年 | 283篇 |
2001年 | 267篇 |
2000年 | 274篇 |
1999年 | 226篇 |
1998年 | 93篇 |
1997年 | 72篇 |
1996年 | 79篇 |
1995年 | 97篇 |
1994年 | 95篇 |
1993年 | 77篇 |
1992年 | 190篇 |
1991年 | 162篇 |
1990年 | 186篇 |
1989年 | 180篇 |
1988年 | 165篇 |
1987年 | 144篇 |
1986年 | 123篇 |
1985年 | 111篇 |
1984年 | 116篇 |
1983年 | 80篇 |
1982年 | 61篇 |
1981年 | 52篇 |
1980年 | 63篇 |
1979年 | 116篇 |
1978年 | 88篇 |
1977年 | 62篇 |
1976年 | 67篇 |
1975年 | 56篇 |
1974年 | 81篇 |
1973年 | 59篇 |
1972年 | 67篇 |
排序方式: 共有8376条查询结果,搜索用时 750 毫秒
61.
Effect of cigarette smoking on the specific antibody response in pigeon fanciers. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Thorax》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Titres of circulating IgG antibodies to pigeon gammaglobulin and end expired carbon monoxide concentrations were measured in 86 pigeon fanciers attending the "Show of the Year." Antibody levels were significantly higher in non-smokers and in those with end expired carbon monoxide concentrations below 10 parts per million. 相似文献
62.
Desensitization of platelet-activating factor-stimulated protein phosphorylation in platelets 总被引:1,自引:0,他引:1
Treatment of 32P-labeled rabbit platelets with platelet-activating factor (PAF) caused a time- and dose-dependent phosphorylation of several proteins including five major phosphorylated proteins with apparent molecular weights of 20,000, 35,000, 40,000, 65,000, and 150,000. Both PAF and thrombin caused a rapid increase followed by a decrease in phosphorylation of proteins, indicating the occurrence of a phosphorylation-dephosphorylation process. Four separate PAF receptor antagonists, CV-3988, CV-6209, SRI-63-441, and SRI-63-675 drastically reduced the PAF-stimulated protein phosphorylation. The order of potency was SRI-63675 greater than SRI-63441 greater than or equal to CV-6209 greater than CV-3988. These antagonists had no effect on thrombin-stimulated protein phosphorylation. Pretreatment of platelets with PAF (0.1 nM) completely abolished any further protein phosphorylation by the same concentration of PAF. PAF pretreatment shifted the dose response of protein phosphorylation by about 2 log units, to the right. When platelets were treated with PAF (10 nM) for 10 min, this abolished phosphorylation of proteins by any concentration of PAF. These studies indicated a homologous desensitization of protein phosphorylation. Interestingly, PAF-pretreated platelets still exhibited phosphorylation of proteins by thrombin. On the other hand, a lack of protein phosphorylation by PAF or thrombin was observed in platelets preexposed to thrombin and this demonstrated a heterologous desensitization. It is concluded that phosphorylation of proteins by PAF is a PAF receptor-coupled event and that this process is desensitized in platelets preexposed to PAF. The fact that both the activation of phosphoinositide-specific phospholipase C and the phosphorylation of proteins are desensitized in PAF-pretreated platelets suggests that a close "regulatory" intercommunication between these processes exists. 相似文献
63.
The effect of bacterial lipopolysaccharide (LPS) on histamine release from human basophils. I. Enhancement of immunologic release by LPS 总被引:2,自引:0,他引:2
Preincubation of human basophils with bacterial lipopolysaccharide (LPS) purified from the heptose-deficient mutant Salmonella minnesota R595 enhanced by an average of sixfold the response of peripheral blood basophils obtained from allergic donors to several allergens in vitro as judged by release of histamine. Enhancement occurred at suboptimal, optimal, and supraoptimal concentrations of antigen. No effect was seen if basophils were from a nonallergic donor, and LPS by itself rarely caused histamine release from any preparation of basophils. However, histamine release in basophils from nonallergic donors induced by antibody directed against IgE (anti-IgE) also was enhanced by LPS. Potentiation of histamine release occurred if basophils were pretreated with LPS before addition of anti-IgE for as little as 5 min; there was no increase in release if anti-IgE and LPS were added simultaneously to cells. LPS enhanced the rate of release without altering duration of the release response. LPS potentiation of release of histamine by F(ab')2 fragments of anti-IgE was equivalent to its effect on release triggered by the intact antibody molecule, confirming that the effect of LPS is not due solely to its interaction with the Fc component of the anti-IgE. These data thus provide evidence for modulation of basophil response to IgE-mediated stimuli by LPS, resulting in a significant enhancement of response. Enhancement by LPS appears to be independent of the stimulus which triggers the IgE receptor. The contribution of this mechanism to allergic disease or asthma remains to be determined. 相似文献
64.
The canine's olfactory acuity is legendary, but neither its main olfactory system nor its vomeronasal system has been described in much detail. We used immunohistochemistry on paraffin-embedded sections of male and female adult dog vomeronasal organ (VNO) to characterize the expression of proteins known to be expressed in the VNO of several other mammals. Basal cell bodies were more apparent in each section than in rodent VNO and expressed immunoreactivity to anticytokeratin and antiepidermal growth factor receptor antibodies. The thin layer of neurone cell bodies in the sensory epithelium and axon fascicles in the lamina propria expressed immunoreactivity to neurone cell adhesion molecule, neurone-specific beta tubulin and protein gene product 9.5. Some neurones expressed growth-associated protein 43 (GAP43): and a number of those also expressed neurone-specific beta tubulin-immunoreactivity. Some axon fascicles were double labelled for those two proteins. The G-protein alpha subunits Gi and Go, involved in the signal transduction pathway, showed immunoreactivity in the sensory cell layer. Our results demonstrate that the canine vomeronasal organ contains a population of cells that expresses several neuronal markers. Furthermore, GAP43 immunoreactivity suggests that the sensory epithelium is neurogenic in adult dogs. 相似文献
65.
Rapid identification of Candida species in blood cultures by a clinically useful PCR method. 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Widespread use of fluconazole for the prophylaxis and treatment of candidiasis has led to a reduction in the number of cases of candidemia caused by Candida albicans but has also resulted in the emergence of candidemias caused by innately fluconazole-resistant, non-C. albicans Candida species. Given the fulminant and rapidly fatal outcome of acute disseminated candidiasis, rapid identification of newly emerging Candida species in blood culture is critical for the implementation of appropriately targeted antifungal drug therapy. Therefore, we used a PCR-based assay to rapidly identify Candida species from positive blood culture bottles. This assay used fungus-specific, universal primers for DNA amplification and species-specific probes to identify C. albicans, C. krusei, C. parapsilosis, C. tropicalis, or C. glabrata amplicons. It also used a simpler and more rapid (1.5-h) sample preparation technique than those described previously and used detergent, heat, and mechanical breakage to recover Candida species DNA from blood cultures. A simple and rapid (3.5-h) enzyme immunosorbent assay (EIA)-based format was then used for amplicon detection. One hundred fifty blood culture bottles, including 73 positive blood culture bottle sets (aerobic and anaerobic) from 31 patients with candidemia, were tested. The combined PCR and EIA methods (PCR-EIA) correctly identified all Candida species in 73 blood culture bottle sets, including bottles containing bacteria coisolated with yeasts and 3 cultures of samples from patients with mixed candidemias originally identified as single-species infections by routine phenotypic identification methods. Species identification time was reduced from a mean of 3.5 days by routine phenotypic methods to 7 h by the PCR-EIA method. No false-positive results were obtained for patients with bacteremias (n = 18), artificially produced non-Candida fungemias (n = 3), or bottles with no growth (n = 20). Analytical sensitivity was 1 cell per 2-microl sample. This method is simpler and more rapid than previously described molecular identification methods, can identify all five of the most medically important Candida species, and has the potential to be automated for use in the clinical microbiology laboratory. 相似文献
66.
It has been suggested that a critically high body core temperature may impair central neuromuscular activation and cause fatigue. We investigated the effects of passive hyperthermia on maximal isometric force production (MVC) and voluntary activation (VA) to determine the relative roles of skin (Tsk) and body core temperature (Tc) on these factors. Twenty-two males [O2max=64.2 (8.9) ml kg–1 min–1, body fat=8.2 (3.9)%] were seated in a knee-extension myograph, then passively heated from 37.4 to 39.4°C rectal temperature (Tre) and then cooled back to 37.4oC using a liquid conditioning garment. Voluntary strength and VA (interpolated twitch) were examined during an isometric 10-s MVC at 0.5°C intervals during both heating and cooling. Passive heating to a Tc of 39.4oC reduced VA by 11 (11)% and MVC by 13 (18)% (P<0.05), but rapid skin cooling, with a concomitant reduction in cardiovascular strain [percentage heart rate reserve decreased from 64 (11)% to 29 (11)%] and psychophysical strain did not restore either of these measures to baseline. Only when cooling lowered Tc back to normal did VA and MVC return to baseline (P<0.05). We conclude that an elevated Tc reduces VA during isometric MVC, and neither Tsk nor cardiovascular or psychophysical strain modulates this response. Results are given as mean (SD) unless otherwise stated. 相似文献
67.
Quantitation of Ergosterol Content: Novel Method for Determination of Fluconazole Susceptibility of Candida albicans
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Beth A. Arthington-Skaggs Hoda Jradi Tejal Desai Christine J. Morrison 《Journal of clinical microbiology》1999,37(10):3332-3337
MIC end points for the most commonly prescribed azole antifungal drug, fluconazole, can be difficult to determine because its fungistatic nature can lead to excessive "trailing" of growth during susceptibility testing by National Committee for Clinical Laboratory Standards broth macrodilution and microdilution methods. To overcome this ambiguity, and because fluconazole acts by inhibiting ergosterol biosynthesis, we developed a novel method to differentiate fluconazole-susceptible from fluconazole-resistant isolates by quantitating ergosterol production in cells grown in 0, 1, 4, 16, or 64 microg of fluconazole per ml. Ergosterol was isolated from whole yeast cells by saponification, followed by extraction of nonsaponifiable lipids with heptane. Ergosterol was identified by its unique spectrophotometric absorbance profile between 240 and 300 nm. We used this sterol quantitation method (SQM) to test 38 isolates with broth microdilution end points of =8 microg/ml (susceptible), 16 to 32 microg/ml (susceptible dose-dependent [SDD]), or >/=64 microg/ml (resistant) and 10 isolates with trailing end points by the broth microdilution method. No significant differences in mean ergosterol content were observed between any of the isolates grown in the absence of fluconazole. However, 18 susceptible isolates showed a mean reduction in ergosterol content of 72% after exposure to 1 microg of fluconazole/ml, an 84% reduction after exposure to 4 microg/ml, and 95 and 100% reductions after exposure to 16 and 64 microg of fluconazole/ml, respectively. Ten SDD isolates showed mean ergosterol reductions of 38, 57, 73, and 99% after exposure to 1, 4, 16, and 64 microg of fluconazole/ml, respectively. In contrast, 10 resistant isolates showed mean reductions in ergosterol content of only 25, 38, 53, and 84% after exposure to the same concentrations of fluconazole. The MIC of fluconazole, by using the SQM, was defined as the lowest concentration of the drug which resulted in 80% or greater inhibition of overall mean ergosterol biosynthesis compared to that in the drug-free control. Of 38 isolates which gave clear end points by the broth microdilution method, the SQM MIC was within 2 dilutions of the broth microdilution MIC for 33 (87%). The SQM also discriminated between resistant and highly resistant isolates and was particularly useful for discerning the fluconazole susceptibilities of 10 additional isolates which gave equivocal end points by the broth microdilution method due to trailing growth. In contrast to the broth microdilution method, the SQM determined trailing isolates to be susceptible rather than resistant, indicating that the SQM may predict clinical outcome more accurately. The SQM may provide a means to enhance current methods of fluconazole susceptibility testing and may provide a better correlation of in vitro with in vivo results, particularly for isolates with trailing end points. 相似文献
68.
Biological Activity of a Mouse-Human Chimeric Immunoglobulin G2 Antibody to Cryptococcus neoformans Polysaccharide
下载免费PDF全文
![点击此处可从《Clinical and Vaccine Immunology : CVI》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Katherine Westin Kwon Nikoletta Lendvai Sherie Morrison K. Ryan Trinh Arturo Casadevall 《Clinical and Vaccine Immunology : CVI》2002,9(1):201-204
The variable regions of the heavy and light chains of the protective murine monoclonal antibody (MAb) 2H1 (m2H1) were expressed with the human constant region genes for immunoglobulin G2 (IgG2) and kappa, respectively, to construct a chimeric antibody (ch2H1). ch2H1 retains the specificity of the parent MAb, exhibits biological activity, and lacks the toxicity of the parent murine IgG1 in chronically infected mice. 相似文献
69.
70.
Cortical and sub-cortical lesions in the rat were used to analyze the intracortical trajectory of the noradrenergic axons, which were visualized by aldehyde-induced catecholamine histofluorescence and by immunohistochemistry using an antibody directed against rat dopamine-β-hydroxylase. Following subcortical lesions there is a slowly progressive reduction in the density of cortical noradrenergic axons, indicating that they undergo asynchronous anterograde degeneration. By 2 weeks after transection of the dorsal noradrenergic bundle, no dopamine β-hydroxylase-immunoreactive fibers are detectable in the ipsilateral cortex. Neither transection of the cingulum bundle, nor parasagittal incisions through the dorsal cortex lateral to the cingulum, diminished the noradrenergic innervation of medial or dorso-lateral cortex. A cortical lesion medial to the cingulum bundle markedly reduced the density of noradrenergic fibers in cingulate cortex caudal to the lesion, but did not affect the innervation of dorso-lateral cortex. In contrast, dorso-lateral frontal incisions and decortication (frontal lobotomy) produced a marked ipsilateral decrease in the noradrenergic fiber density throughout the remaining dorso-lateral cortex, while sparing the innervation of cingulate and infra-rhinal cortex.These results demonstrate that the dorso-lateral cortex is innervated by noradrenergic fibers in the medial forebrain bundle that reach the frontal pole, turn dorsally over the anterior portion of the forceps minor and continue caudally within the deep layers of frontal and dorso-lateral cortex, supplying the noradrenergic innervation throughout their trajectory. The medial cortex is innervated by a separate group of noradrenergic fibers that ascend through the septum, curve over the genu of the corpus callosum, and run caudally in the supracallosal stria.The present results show that the cingulum bundle is not a major intra-cortical noradrenergic pathway and does not provide branches that contribute significantly to the innervation of dorsal or lateral cortex. Thus the medial and lateral cortex can be selectively and differentially denervated of noradrenergic fibers and a coarse topographic order exists in the noradrenergic innervation of cortex. Since noradrenergic fibers travel long distances within the cortical grey matter, a small lesion of frontal cortex can have far-reaching effects on the innervation of distant, more caudal regions of cortex. The coeruleocortical projection has properties that differ from those of the best characterized cortical afferents and may be a useful model for the study of other ascending monoamine systems. The tangential, intracortical trajectory of the noradrenergic fibers would confer upon the coeruleo-cortical system the capacity to modulate neuronal activity simultaneously through a vast expanse of neocortex. A formulation of cortical organization is presented which integrates the tangential organization of the coeruleo-cortical projection with the concept of columnar organization of cortex. 相似文献