首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15191篇
  免费   889篇
  国内免费   54篇
耳鼻咽喉   188篇
儿科学   749篇
妇产科学   299篇
基础医学   1571篇
口腔科学   380篇
临床医学   1108篇
内科学   3410篇
皮肤病学   329篇
神经病学   955篇
特种医学   515篇
外国民族医学   1篇
外科学   2722篇
综合类   376篇
一般理论   9篇
预防医学   722篇
眼科学   401篇
药学   1313篇
中国医学   68篇
肿瘤学   1018篇
  2023年   125篇
  2022年   222篇
  2021年   613篇
  2020年   349篇
  2019年   413篇
  2018年   566篇
  2017年   395篇
  2016年   478篇
  2015年   461篇
  2014年   685篇
  2013年   835篇
  2012年   1239篇
  2011年   1239篇
  2010年   742篇
  2009年   622篇
  2008年   833篇
  2007年   875篇
  2006年   745篇
  2005年   670篇
  2004年   548篇
  2003年   440篇
  2002年   383篇
  2001年   225篇
  2000年   241篇
  1999年   209篇
  1998年   106篇
  1997年   75篇
  1996年   68篇
  1995年   65篇
  1994年   58篇
  1993年   43篇
  1992年   129篇
  1991年   118篇
  1990年   98篇
  1989年   113篇
  1988年   93篇
  1987年   87篇
  1986年   74篇
  1985年   90篇
  1984年   74篇
  1983年   68篇
  1982年   40篇
  1981年   33篇
  1979年   56篇
  1978年   34篇
  1977年   38篇
  1976年   35篇
  1974年   41篇
  1973年   40篇
  1969年   35篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.

Objectives

To investigate the incidence, risk factors, clinical course and outcomes of pregnancy-related group A streptococcus (GAS) infection.

Methods

A retrospective 13-year cohort study of culture-proven pregnancy-related GAS infection was performed at two university hospitals serving heterogeneous, multicultural, urban and rural populations.

Results

Of 124 women diagnosed with pregnancy-related GAS infection, 115 (93%) were in the puerperium, an incidence of 0.8 cases per 1000 live births (95% confidence interval, 0.7–0.9). A multivariate analysis showed primiparity and cesarean delivery to be independent protective factors against puerperal GAS infection (adjusted odds ratios (95% confidence interval), 0.60 (0.38, 0.97) and 0.44 (0.23, 0.81), respectively). Of the nine remaining patients, eight were diagnosed after first trimester abortions and one had an infected ectopic pregnancy. Among the entire cohort (n = 124), the predominant manifestations were fever and abdominal tenderness. Twenty-eight patients (23%) had severe GAS infections. All were treated with β-lactams, and most (n = 104, 84%) received clindamycin. Only four (3%) required surgical intervention; the rest fully recovered with conservative medical treatment including antibiotics. No recurrences, maternal deaths or neonatal complications were noted.

Conclusions

Pregnancy-related GAS infection is not rare; it lacks specific signs and still carries significant morbidity. Primiparity, a presumable surrogate for diminished exposure to children and thus less GAS carriage, and cesarean delivery in which perioperative antibiotic prophylaxis was uniformly provided, appear as protective factors against puerperal GAS infection. This hints to the importance of community-acquired GAS and may support shifting efforts from infection-control–oriented nosocomial investigations to screening and prevention–driven policies.  相似文献   
92.
Adrenoleukodystrophy (ALD) is an X-linked disorder caused by a defect in the metabolism of long chain fatty acids leading to demyelination, neurodegeneration, and death. The disease typically presents in young boys and adolescent boys. Allogeneic bone marrow transplantation has been used to halt progression of the disease. However, many patients lack suitable HLA- matched related donors and must rely on unmatched donors for a source of stem cells. The purpose of this study was to evaluate outcomes of unrelated donor umbilical cord blood transplantation after chemotherapy-based myeloablative conditioning and retrospectively determine if baseline studies correlate and help predict outcome. Between November 22, 1996, and November 3, 2005, 12 boys with X-linked ALD who lacked HL- matched related donors were referred to Duke University Medical Center for transplantation. These children were conditioned with myeloablative therapy including busulfan, cyclophosphamide, and antithymocyte globulin before receiving umbilical cord-blood transplants from unrelated donors. Baseline studies of neurophysiologic, neuroimaging, and neurodevelopmental status were performed and patients were subsequently evaluated for survival, engraftment, graft-versus-host disease, and neurodevelopmental outcomes. A substudy evaluated whether baseline neuroimaging and neurophysiologic studies correlated with cognitive and motor function and if these studies were predictive of posttransplantation outcomes. The umbilical cord blood grafts had normal levels of very long chain fatty acids. They delivered a median of 6.98 x 10(7) nucleated cells per kilogram of recipient body weight and were discordant for up to 4 of 6 HLA markers. Neutrophil engraftment occurred at a median of 22.9 days after transplantation. Three patients had grade II-IV acute graft-versus-host disease; 2 had extensive chronic graft-versus-host disease. Cumulative incidence of overall survival of the group at 6 months is 66.7% (95% confidence interval 39.9-93.3%). Median follow-up was 3.3 years (range 12 days to 6.3 years). As previously reported with bone marrow transplantation, symptomatic patients faired poorly with lower survival and rapid deterioration of neurologic function. This study included 3 patients transplanted at a very young age (2.6-3.5 years) before the onset of clinical symptoms who continue to develop at a normal rate for 3-5 years posttransplant. Although baseline Loes scores correlated with cognitive and motor outcome, neurophysiologic studies failed to show statistically significant differences. Transplantation of boys with X-linked ALD using partial HLA-matched umbilical cord blood yields similar results to those previously reported after bone marrow transplantation. Superior outcomes were seen in neurologically asymptomatic boys less than 3.5 years of age at the time of transplantation. Baseline Loes scores were a strong predictor of cognitive and motor outcome.  相似文献   
93.
Gastrointestinal vascular anomalies are extremely uncommon. We describe a patient with Down syndrome who presented with acute abdominal pain due to a mixed capillary and venous vascular malformation involving the proximal jejunum.  相似文献   
94.
95.
Stress-induced analgesia: adaptive pain suppression   总被引:7,自引:0,他引:7  
Amit  Z.; Galina  Z. H. 《Physiological reviews》1986,66(4):1091-1120
In this paper we have examined the phenomenon of stress-induced analgesia. We have described the procedures used to measure analgesia and have suggested that the tests can be designed not only to indicate changes in pain threshold but also to allow for the determination of the capacity to execute adaptive behavior. Aside from enabling the analysis of responses, tests that induce reflexive as well as nonreflexive behavior may have the capacity to separate the more complex aspects of pain such as the possible presence of two components of pain, sensory/discriminative and motivational/affective. These components may be of fundamental importance for any attempt to understand the biological significance of SIA. Our examination of the neurotransmitter and neuropeptide systems has revealed that they are affected by the same manipulations that induce SIA. These amines and perhaps peptides play an integral role in learning, motivation, and performance. We conclude that the functional advantage of a reduction of pain during stressful situations is significant because it allows the animal to react in threatening and perhaps critical situations as if there were no pain. Once the pain system is inhibited, other systems modulate and mediate adaptive responses that expedite the survival of the animal.  相似文献   
96.
The gene PTPN22 is located on chromosome 1p13 and encodes a protein tyrosine phosphatase called the lymphoid-specific phosphatase (Lyp). Lyp is expressed in lymphocytes, where it physically associates through its proline-rich motif (called P1) with the SH3 domain of the protein tyrosine kinase Csk, an important suppressor of the Src family of kinases Lck and Fyn, which mediate TCR signaling. Therefore, it is said that interaction between Lyp and Csk enables these effectors to inhibit T-cell activation synergistically. It was reported that a missense single nucleotide polymorphism , R620W (rs2476601), 1858C->T encodes an amino-acid change in the P1 proline-rich motif of the gene PTPN22 and is associated with SLE in North American white individuals. PTPN22 gene polymorphisms were genotyped in 571 Swedish SLE patients and 1042 healthy controls using TaqMan SNP Genotyping Assay. Differences were observed between cases and control subjects at both the allele (chi(2)=11.2895;P=0.0007,1df) and genotype (chi(2)=10.2243;P=0.0013, 1df) levels. We also found evidence of a genetic association between PTPN22 and renal disorder (chi(2)=9.5660;P=0.0019). We then analyzed if in patients with renal disorder associations with PDCD1 and PTPN22 were independent. Our data suggest that this appears to be the case although we observed some degree of interaction.  相似文献   
97.
By functional complementation of a PDR5 null mutant of Saccharomyces cervisiae, we have cloned and sequenced the multidrug-resistance gene CDR1 of Candida albicans. Transformation by CDR1 of a PDR5-disrupted host hypersensitive to cycloheximide and chloramphenicol resulted in resistance to cycloheximide, chloramphenicol and other drugs, such as the antifungal miconazole, with collateral hypersensitivity to oligomycin, nystatin and 2,4 dinitrophenol. Our results also demonstrate the presence of several PDR5 complementing genes in C. albicans, displaying multidrug-resistance patterns different from PDR5 and CDR1. The nucleotide sequence of CDR1 revealed that, like PDR5, it encodes a putative membrane pump belonging to the ABC (ATP-binding cassette) superfamily. CDR1 encodes a 1501-residue protein of 169.9 kDa whose predicted structural organization is characterized by two homologous halves, each comprising a hydrophobic region with a set of six transmembrane stretches, preceded by a hydrophilic nucleotide binding fold.  相似文献   
98.
To understand the mechanism(s) of appetite modulation by DHEA, we have undertaken a series of studies to examine the effects of DHEA on neurotransmitters and neuropeptides known to affect appetitive behavior. Here, we report the effect of DHEA on serum enterostatin-VPDPR or E, a pentapeptide known to cause selective diminution in fat intake. Four-week-old lean (fa/+) and obese (fa/fa) Zucker rats were divided into control and treatment groups. DHEA-treated groups received powdered chow containing 0.6% DHEA ad lib for 16 weeks. Another group of obese rats was pair fed to match the intake of the obese DHEA-treated rats. At the end of this period, trunk blood was collected from fasted rats for assay of E-like immunoreactivity (E-LI) by ELISA. DHEA treatment caused a significant diminution in circulating E-LI in both lean (control: 2030 +/- 226; treated: 752 +/- 145 ng/mL; n = 10, p < 0.0001) and obese (control: 2489 +/- 391, n = 6; treated: 1123 +/- 185 ng/mL, n = 7; p = 0.0003) rats. Because DHEA treatment decreases caloric intake and body weight, we examined the effect of caloric intake and body weight on E-LI levels. Serum ELI levels were lower in the obese DHEA-treated group compared to that of obese pair fed (pair fed: 1589 +/- 313, n = 6; DHEA: 1123 +/- 185 ng/mL, n = 7), but the differences were statistically insignificant (p = 0.185). Also, both weight-matched lean and obese control rats had significantly (p < 0.008) higher E-LI than their DHEA-treated counterparts. To examine whether the decrease in serum E-LI following DHEA treatment could be due to increased peptide metabolism, the rate of disappearance of endogenous E-LI from serum (obese control and DHEA-treated) at 37 degrees C was evaluated. The results show an attenuation of peptide metabolism in serum from DHEA-treated rats, a finding contrary to our expectations. In summary, DHEA treatment lowers serum E-LI levels both in lean and obese Zucker rats. This decrement in peptide level is not secondary to changes in body weight or caloric intake due to DHEA, or due to altered serum peptide metabolism. Although DHEA appears to be a potent modulator of E-LI levels, the relationship between DHEA and E-LI in relation to appetitive behavior remains to be clarified.  相似文献   
99.
100.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号