全文获取类型
收费全文 | 9073篇 |
免费 | 486篇 |
国内免费 | 45篇 |
专业分类
耳鼻咽喉 | 89篇 |
儿科学 | 152篇 |
妇产科学 | 87篇 |
基础医学 | 1205篇 |
口腔科学 | 292篇 |
临床医学 | 996篇 |
内科学 | 2020篇 |
皮肤病学 | 220篇 |
神经病学 | 946篇 |
特种医学 | 440篇 |
外科学 | 1296篇 |
综合类 | 37篇 |
预防医学 | 345篇 |
眼科学 | 186篇 |
药学 | 665篇 |
中国医学 | 45篇 |
肿瘤学 | 583篇 |
出版年
2023年 | 24篇 |
2022年 | 47篇 |
2021年 | 129篇 |
2020年 | 94篇 |
2019年 | 107篇 |
2018年 | 129篇 |
2017年 | 147篇 |
2016年 | 167篇 |
2015年 | 200篇 |
2014年 | 220篇 |
2013年 | 321篇 |
2012年 | 524篇 |
2011年 | 583篇 |
2010年 | 370篇 |
2009年 | 417篇 |
2008年 | 604篇 |
2007年 | 677篇 |
2006年 | 665篇 |
2005年 | 686篇 |
2004年 | 647篇 |
2003年 | 643篇 |
2002年 | 643篇 |
2001年 | 127篇 |
2000年 | 104篇 |
1999年 | 126篇 |
1998年 | 142篇 |
1997年 | 99篇 |
1996年 | 95篇 |
1995年 | 64篇 |
1994年 | 64篇 |
1993年 | 50篇 |
1992年 | 40篇 |
1991年 | 51篇 |
1990年 | 38篇 |
1989年 | 40篇 |
1988年 | 29篇 |
1987年 | 36篇 |
1986年 | 27篇 |
1985年 | 29篇 |
1984年 | 39篇 |
1983年 | 27篇 |
1982年 | 23篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1974年 | 20篇 |
1973年 | 23篇 |
排序方式: 共有9604条查询结果,搜索用时 15 毫秒
61.
Utility of Major Leukocyte Subpopulations for Monitoring Secondary Cytomegalovirus Infections in Renal-Allograft Recipients by PCR 总被引:2,自引:1,他引:2
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)
Peter Schfer Werner Tenschert Liana Cremaschi Kai Gutensohn Rainer Laufs 《Journal of clinical microbiology》1998,36(4):1008-1014
The feasibility of the major peripheral blood leukocyte (PBL) subsets for use in qualitative and quantitative PCR to monitor secondary cytomegalovirus (CMV) infection and ganciclovir therapy was assessed with 188 blood samples derived from 40 CMV immunoglobulin G-positive renal-allograft recipients. In pp65 antigen-positive patients all leukocyte fractions, but only 79.5% of plasma preparations, were PCR positive. In pp65 antigen-negative samples from patients after antiviral treatment only 7.3% of polymorphonuclear cell (PMNL) samples, but 81.8% of peripheral blood mononuclear cells (PBMC), and 10.9% of plasma samples remained PCR positive. Similarly, in patients with latent infections only 5.0% of PMNL, but 51.7% of PBMC preparations, and 8.0% of plasma samples were PCR positive. Regarding patients with active CMV infection, CMV DNA copy numbers in PMNL correlated significantly with pp65 antigen-positive cell counts before and after onset of ganciclovir therapy. Significant differences in CMV DNA copy numbers in PMNL and plasma were observed (i) between patients with symptomatic infection and those with asymptomatic infection and (ii) between patients with active infection and those with latent infection. In contrast, PBMC harbored equally low CMV DNA levels both in patients with active infection and those with latent infections, and no decline of CMV DNA load in PBMC was observed during antiviral treatment. We conclude that detection of CMV DNA in PMNL, not in PBMC, is associated with active infections and is more sensitive than detection of CMV DNA in plasma. Negative PCR results for PMNL after antiviral therapy indicate recovery, and fewer unwanted positive results occur compared to PBMC and plasma. Therefore, purified PMNL should be preferred for analysis by qualitative CMV PCR to avoid unwanted positive results. The CMV DNA load in PBMC compared with that in PMNL is negligible during active infection, so mixed PBL are sufficient for use in quantitative PCR. 相似文献
62.
Task-specific neural activity in the primate prefrontal cortex 总被引:12,自引:0,他引:12
Real-world behavior is typically more complicated than a one-to-one mapping between a stimulus and response; the same stimulus can lead to different behaviors depending on the situation, or the same behavior may be cued by different stimuli. In such cases, knowledge of the formal demands of the task at hand is required. We found that in monkeys trained to alternate between three tasks, the activity of many neurons in the prefrontal cortex was task dependent. This included changes in overall firing rate, in firing-rate profiles (shape of responses over time), and in stimulus and response selectivity. These findings support the hypothesis that a major prefrontal function is the acquisition and implementation of task context and the "rules" used to guide behavior. 相似文献
63.
Beate M Herbert Olga Pollatos Rainer Schandry 《International journal of psychophysiology》2007,65(3):214-227
Theories of emotion consider the self-perception of visceral activity to play an important role in emotion. This study examined the relationship between interoceptive sensitivity and both the subjective emotional experience and the processing of emotional pictures. According to their results in a heartbeat detection task subjects were classified as good (N = 17) or poor (N = 20) heartbeat perceivers. Event-related potentials were recorded while subjects viewed pleasant, neutral and unpleasant pictures and SAM ratings were examined. Good heartbeat perceivers showed significantly greater P300 and slow wave amplitudes for emotional pictures at antero-inferior, medial and posterior electrode sites and experienced a greater arousal for emotional pictures compared to poor heartbeat perceivers. The heartbeat perception score correlated significantly positive both with emotional P300 and slow wave amplitudes as well as with the arousal ratings for emotional pictures. The results indicate that there is a significant and strong association between interoceptive sensitivity and the intensity of emotional experience as well as the central processing of emotional stimuli. 相似文献
64.
The first and second internal transcribed spacers (ITS1, ITS2) as well as the intervening 5.8S coding region of the rRNA
gene were characterized in eight Babesia canis isolates of differing geographic origin, vector specificity, and pathogenicity to dogs. The genotypes determined by sequencing
segregated into three clearly separated groups close to or near the species level and correspond to the previously proposed
subspecies B. canis canis, B. canis vogeli, and B. canis rossi. The three genotypes can be distinguished by Sau96I digestion of the polymerase chain reaction (PCR)-amplified rDNA target.
Received: 12 December 1997 / Accepted: 5 January 1998 相似文献
65.
Autoimmunity and inflammation due to a gain-of-function mutation in phospholipase C gamma 2 that specifically increases external Ca2+ entry 总被引:3,自引:0,他引:3
Yu P Constien R Dear N Katan M Hanke P Bunney TD Kunder S Quintanilla-Martinez L Huffstadt U Schröder A Jones NP Peters T Fuchs H de Angelis MH Nehls M Grosse J Wabnitz P Meyer TP Yasuda K Schiemann M Schneider-Fresenius C Jagla W Russ A Popp A Josephs M Marquardt A Laufs J Schmittwolf C Wagner H Pfeffer K Mudde GC 《Immunity》2005,22(4):451-465
The identification of specific genetic loci that contribute to inflammatory and autoimmune diseases has proved difficult due to the contribution of multiple interacting genes, the inherent genetic heterogeneity present in human populations, and a lack of new mouse mutants. By using N-ethyl-N-nitrosourea (ENU) mutagenesis to discover new immune regulators, we identified a point mutation in the murine phospholipase Cg2 (Plcg2) gene that leads to severe spontaneous inflammation and autoimmunity. The disease is composed of an autoimmune component mediated by autoantibody immune complexes and B and T cell independent inflammation. The underlying mechanism is a gain-of-function mutation in Plcg2, which leads to hyperreactive external calcium entry in B cells and expansion of innate inflammatory cells. This mutant identifies Plcg2 as a key regulator in an autoimmune and inflammatory disease mediated by B cells and non-B, non-T haematopoietic cells and emphasizes that by distinct genetic modulation, a single point mutation can lead to a complex immunological phenotype. 相似文献
66.
Properties and regulation of chloride channels in cystic fibrosis and normal airway cells 总被引:4,自引:0,他引:4
Karl Kunzelmann Hermann Pavenstädt Rainer Greger 《Pflügers Archiv : European journal of physiology》1989,415(2):172-182
The present study examines the properties of Cl–channels in cultured respiratory cells of cystic fibrosis (CF) patients and normal (N) individuals. In excised membrane patches the conductances for CF and N Cl– channels were larger at positive as compared to negative clamp voltages (V
c): 74±2.6 (V
c > 0) and 47±2.0 pS (V
c < 0) for CF (n= 57) and 69±3.6 (V
c > 0) and 45±2.3 pS (V
c < 0) for N (n=35). The open probability (P
o) of the channel increased markedly with depolarization. Both the voltage dependence of the conductance and of P
o contribute to the outward rectification of the channel. The time histogram analysis reveals two open and two closed time constants. The selectivity of the channel was Cl–=Br– =I– > NO
3
–
gluconate. The channel was inhibited reversibly by 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) at 10–7 mol/l to 10–5 mol/l. While Cl– channels were present in cell attached patches of N cells, they were absent in those of CF cells. The mean conductance for cell attached (N) Cl– channels was 76±3.2 pS for positive clamp voltages (V
c) and 46±3.9 pS for negative V
c (n=8). When the membrane patches were excised from CF cells Cl– currents appeared spontaneously (n=19). The immediate appearance (within 1 s) of Cl– channels after excision was observed at positive (n=6) as well as at negative clamp voltage (n=13). Excision activation of CF Cl– channels was observed at low (< 10–9 mol/l) or high (10–3 mol/l) calcium activities on the cytosolic side of the excised patch. Variation of the Ca+ activity (< 10–9–10–3 mol/l) or pH (6.5–8.5) on the cytosolic side exerted no effects on these Cl– channels. These results suggest that Cl– channels are present in the apical membrane of CF and N respiratory cells but they seem to be inhibited in intact CF cells. Excision of the patch and hence removal of the cytosolic inhibitor leads to an activation of Cl– channels. The Cl– channels in excised patches of N and CF cells have identical properties. 相似文献
67.
Acute and long-term humoral immunity following active immunization of rabbits with inacctivated spores of various Encephalitozoon species 总被引:1,自引:0,他引:1
Sobottka I Iglauer F Schüler T Schmetz C Visvesvara GS Albrecht H Schwartz DA Pieniazek NJ Bartscht K Laufs R Schottelius J 《Parasitology research》2001,87(1):1-6
Microsporidia of the genus Encephalitozoon are increasingly being reported as a cause of severe, often disseminated infections, mainly in patients with acquired immunodeficiency
syndrome (AIDS). Immunological identification of each of the three recognized species (E. cuniculi, E. hellem, and E. intestinalis) requires the availability of specific immune sera. All sera available thus far have been generated by direct inoculation
of rabbits with virulent microsporidian spores. This study demonstrates for the first time that subcutaneous immunization
with inactivated spores of E. cuniculi, E. hellem, or E. intestinalis is capable of generating highly active rabbit hyperimmune sera to the homologous antigens, with maximal titers being 1:5,120,
1:1,280, and 1:2,560, respectively, as determined by the indirect immunofluorescence technique (IIF). Broad cross-reactivity
of the rabbit antisera with all heterologous Encephalitozoon antigens was determined by IIF and immunogold electron microscopy; however, only the E. hellem immune serum strongly cross-reacted with spores of Enterocytozoon bieneusi. During the 35-month follow-up period the antibody titers to the homologous antigens declined to 1:640, 1:160, and 1:320,
respectively. The observed decay curves for antibody titers against E. cuniculi, E. hellem, and E. intestinalis were fitted using mathematical modeling, resulting in a predicted duration for specific immune responses of about 7 years
on average. Knowledge of the magnitude and duration of specific immune responses is a prerequisite for further evaluation
of the concept of using inactivated microsporidian spores in the quest for vaccines against microsporidian infections.
Received: 10 April 2000 / Accepted: 18 July 2000 相似文献
68.
Schwarz C Hauser P Steininger R Regele H Heinze G Mayer G Oberbauer R 《Laboratory investigation; a journal of technical methods and pathology》2002,82(7):941-948
SUMMARY: In renal transplantation, postischemic acute renal failure (ARF) develops in more than 20% of patients. We investigated whether tubular epithelial cells obtained from donor kidneys without subsequent ARF express a different pattern of survival genes, compared with cells from kidneys exhibiting ARF. Donor kidney biopsy specimens were obtained before transplantation from eight recipients of cadaveric kidneys with primary graft function (CAD-PF), eight patients with biopsy-proven ARF without rejection (CAD-ARF), and eight recipients of living donor kidneys with primary graft function (LIV). One thousand proximal tubular epithelial cells per biopsy specimen were isolated by laser capture microdissection. Quantitative analysis of apoptosis and the apoptosis regulatory genes Bcl-2, Bcl-xL, and Bax were performed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling staining and real-time PCR, respectively. Primary cultures of human proximal tubular epithelial cells served as calibrator. The number of apoptotic cells was significantly higher in CAD-ARF compared with LIV and CAD-PF (1.5 +/- 1.1% [p < 0.05] vs. 0.3 +/- 0.2% vs. 0.4 +/- 0.2%; mean +/- SD). The apoptosis inhibitors Bcl-2 and Bcl-xL were significantly up-regulated in renal tubular cells of recipients without ARF compared with CAD-ARF. The ratios of Bcl-2/GAPDH normalized to calibrator were as follows: LIV 48 +/- 30, CAD-PF 38 +/- 55, and CAD-ARF 5 +/- 7 (p < 0.05). The corresponding ratios for Bcl-xL were as follows: LIV 6 +/- 6, CAD-PF 5 +/- 3, and CAD-ARF 1 +/- 1 (p < 0.05). No difference in the expression of the proapoptotic Bax could be observed. These data suggest that failure of proximal tubular cells to respond to injury by up-regulation of survival factors from the Bcl-2 family contributes to postischemic ARF in patients after cadaveric renal transplantation. 相似文献
69.
70.
Hans Oberleithner Florian Lang Rainer Greger Hans Sporer 《Pflügers Archiv : European journal of physiology》1979,379(1):37-41
In previous studies it has been demonstrated that a decline of plasma calcium concentration accounts for the decrease of phosphate reabsorption in thyroparathyroidectomized (TPTX) rats undergoing phosphate loading.Microinfusion studies were performed in TPTX rats in order to discriminate between a systemic effect of calcium an a direct renal effect.Thyroparathyroidectomized animals were infused with a phosphate solution continuously. When plasma calcium concentration fell below 1.30 mmol/l, proximal convoluted tubules were microinfused with a phosphate tracer solution for 42 min. After 18 min a calcium chloride-containing solution was applied superficially (superfused) to the area of the microinfused tubule. This elevation of peritubular calcium concentration led to an immediate increase of phosphate reabsorption up to 12% of the microinfused phosphate load within 24 min.In another series of experiments, the calcium specific ionophore A 23187 — a substance which is known to increase intracellular calcium — was superfused on the microinfused tubule. This resulted again in an increase of fractional phosphate reabsorption of about 15% after 24 min. In contrast, when calcium chloride-free as well as ionophore-free solutions were superfused fractional phosphate reabsorption decreased (7%).From these data we conclude that 1. calcium has a direct renal effect on phosphate reabsorption in the absence of parathyroid hormone and 2. intracellular calcium appears to be a major parameter in the regulation of renal phosphate transport under these conditions.This study was supported by Dr. Legerlotz StiftungParts of this study were presented at the fall meeting of the Nephrologische Gesellschaft in Bonn, 1977 and at the spring meeting of the Deutsche Physiologische Gesellschaft in Göttingen, 1978 相似文献