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   946篇
  免费   86篇
  国内免费   8篇
耳鼻咽喉   11篇
儿科学   15篇
妇产科学   21篇
基础医学   193篇
口腔科学   4篇
临床医学   103篇
内科学   215篇
皮肤病学   21篇
神经病学   121篇
特种医学   27篇
外科学   63篇
综合类   3篇
一般理论   1篇
预防医学   60篇
眼科学   29篇
药学   81篇
肿瘤学   72篇
  2023年   10篇
  2022年   27篇
  2021年   46篇
  2020年   19篇
  2019年   37篇
  2018年   24篇
  2017年   22篇
  2016年   24篇
  2015年   32篇
  2014年   40篇
  2013年   51篇
  2012年   76篇
  2011年   77篇
  2010年   31篇
  2009年   33篇
  2008年   72篇
  2007年   78篇
  2006年   76篇
  2005年   60篇
  2004年   54篇
  2003年   56篇
  2002年   23篇
  2001年   9篇
  2000年   3篇
  1999年   4篇
  1998年   6篇
  1997年   3篇
  1996年   5篇
  1994年   2篇
  1992年   2篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   4篇
  1986年   1篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1980年   1篇
  1979年   4篇
  1977年   2篇
  1976年   1篇
  1975年   4篇
  1973年   3篇
  1971年   2篇
  1970年   1篇
  1968年   2篇
  1938年   1篇
  1936年   1篇
  1930年   1篇
排序方式: 共有1040条查询结果,搜索用时 0 毫秒
41.
We have reported associations between human leukocyte antigen (HLA) homozygosity and low measles antibody levels after one dose of the measles, mumps, and rubella (MMR) vaccine. Here, we examined associations between HLA homozygosity and immune responses to MMR after two doses of vaccine. We examined associations between HLA homozygosity and measles antibody levels in a group of 178 children (cohort 1) as well as associations between homozygosity and antibody levels and lymphoproliferative responses to MMR in 346 children (cohort 2). In cohort 1, HLA homozygotes and heterozygotes had similar increases in measles antibody levels after a second dose of measles vaccine. In cohort 2, HLA homozygosity was not associated with measles immune measures after two doses of vaccine. Homozygosity at the DPB locus was associated with increased rubella antibody levels, and homozygosity at the class IA alleles was associated with lower mumps lymphoproliferative response. Homozygosity at increasing numbers of loci was also associated with lower mumps antibody levels and lymphoproliferative response. Therefore, two doses of the MMR vaccine appear to induce sufficient antibody levels and lymphoproliferative responses against measles and rubella, regardless of HLA homozygosity status. However, children who are HLA homozygous may be less protected against mumps compared with children who are heterozygous.  相似文献   
42.
BACKGROUND: In contrast to numerous epidemiological studies that explored the risk for cancer among persons with schizophrenic psychoses, analogous studies conducted on people with bipolar disorder are rarer, despite some commonalities in biological, treatment-related variables and unhealthy lifestyles. This study investigates the risk for cancer among psychiatric inpatients diagnosed with bipolar disorder. METHODS: Linkage analysis was conducted based on the psychiatric and the cancer national databases. Standardized incidence ratios (SIR) for both aggregated sites and for breast cancer were calculated by comparing the incidence rates among hospitalized patients with bipolar disorder with the incidence rates in the Jewish-Israeli general population. RESULTS: An enhanced cancer risk was found for bipolar disorder in both genders: men, SIR 1.59 (95% CI 1.01-2.17); women, SIR 1.75 (95% CI 1.31-2.18). The risk for breast cancer was higher, but not significantly, than in the general female population, SIR 1.70 (95% CI 0.99-2.41). LIMITATIONS: Our sample was derived from psychiatric inpatients, thus it is likely that the bipolar disorder cases had greater severity. Putative factors such as diet, smoking and medications were not investigated. CONCLUSIONS: Our study showed an enhanced risk for cancer among patients with bipolar disorder. Clinicians might note this risk for timely diagnosis and treatment.  相似文献   
43.
We present an analysis of rates and patterns of microevolutionary phenomena that have shaped the human, mouse, and rat genomes since their last common ancestor. We find evidence for a shift in the mutational spectrum between the mouse and rat lineages, with the net effect being a relative increase in GC content in the rat genome. Our estimate for the neutral point substitution rate separating the two rodents is 0.196 substitutions per site, and 0.65 substitutions per site for the tree relating all three mammals. Small insertions and deletions of 1-10 bp in length ("microindels") occur at approximately 5% of the point substitution rate. Inferred regional correlations in evolutionary rates between lineages and between types of sites support the idea that rates of evolution are influenced by local genomic or cell biological context. No substantial correlations between rates of point substitutions and rates of microindels are found, however, implying that the influences that affect these processes are distinct. Finally, we have identified those regions in the human genome that are evolving slowly, which are likely to include functional elements important to human biology. At least 5% of the human genome is under substantial constraint, most of which is noncoding.  相似文献   
44.
Our objective was to replicate previously reported associations between cytokine and cytokine receptor SNPs and humoral and CMI (cell-mediated immune) responses to measles vaccine. All subjects (n=758) received two doses of MMR (measles/mumps/rubella) vaccine. From these subjects, candidate cytokine and cytokine receptor SNPs were genotyped and analyzed in 29-30 subjects falling into one of four "extreme" humoral (Ab(high/low)) and CMI (CMI(high/low)) response quadrants. Associations between seven SNPs (out of 11 in the discovery study) and measles-specific neutralizing antibody levels and IFN-γ ELISPOT responses were evaluated using chi-square tests. We found one replicated association for SNP rs372889 in the IL12RB1 gene (P=0.03 for Ab(high)CMI(high) vs. Ab(low)CMI(low)). Our findings demonstrate the importance of replicating genotypic-phenotypic associations, which can be achieved using immunophenotypic extremes and smaller sample sizes. We speculate that IL12RB1 polymorphisms may affect IL-12 and IL-23 binding and downstream effects, which are critical cytokines in the CMI response to measles vaccine.  相似文献   
45.
Poly(norbornene)s with pendant imidazolium moieties and three different counter anions, i.e. poly[exo,endo‐5‐norbornene‐2‐yl‐carboxyethyl‐3‐ethylimidazolium bis(trifluoromethyl‐sulfonyl)imide], poly(exo,endo‐5‐norbornene‐2‐yl‐carboxyethyl‐3‐ethylimidazolium tetrafluoroborate), and poly(exo,endo‐5‐norbornene‐2‐yl‐carboxyethyl‐3‐ethylimidazolium hexafluorophosphate) were prepared via ROMP using ionic liquids as the reaction medium. The ionic polymers possessed in the range 8.1–44 × 103 and ionic conductivity up to 1.13 × 10−5 and 1.44 × 10−4 S · cm−1 at 20 and 50 °C, respectively. The solubility of the new polymeric ionic liquids, their thermal stability and their glass transition temperatures were investigated in detail. Ionic conductivities were found to depend on the nature of the counter‐anion and on the polymers' glass transition temperature rather than its molecular weight.

  相似文献   

46.
The protective effect of measles immunization is due to humoral and cell-mediated immune responses. Little is known about cell-mediated immunity (CMI) to measles vaccine virus, the relative contribution of CD4(+) and CD8(+) T cells to variability in such immune responses, and the immunologic longevity of the CMI after measles vaccination in humans. Our study characterizes cellular immune response in subjects seronegative or highly seropositive for measles vaccine immunoglobulin G-specific antibody, aged 15 to 25 years, previously immunized with two doses of measles-mumps-rubella II vaccine. We evaluated the ability of subjects to respond to measles vaccine virus by measuring measles virus-specific T-cell proliferation. We examined the frequencies of measles virus-specific memory Th1 and Th2 cells by an ELISPOT assay. Our results demonstrated that proliferation of T cells in seronegative subjects was significantly lower than that for highly seropositive subjects (P = 0.003). Gamma interferon (IFN-gamma) secretion predominated over interleukin 4 (IL-4) secretion in response to measles virus in both groups. The median frequency of measles virus-reactive CD8(+) T cells secreting IFN-gamma was 0.09% in seronegative subjects and 0.43% in highly seropositive subjects (P = 0.04). The median frequency of CD4(+) T cells secreting IL-4 in response to measles virus was 0.03% in seronegative subjects and 0.09% in highly seropositive subjects (P = 0.005). These data confirm the presence of measles virus-specific cellular immune responses post-measles vaccine immunization in humans. The detection of measles virus-induced IFN-gamma and IL-4 production by ELISPOT can be used to identify measles virus-specific low-frequency memory T cells in subjects immunized with measles vaccine. These differences agree in directionality with the observed antibody response phenotype.  相似文献   
47.
Klebsiella pneumoniae carbapenemase (KPC) 3–producing Escherichia coli was isolated from a carrier of KPC-3–producing K. pneumoniae. The KPC-3 plasmid was identical in isolates of both species. The patient''s gut flora contained a carbapenem-susceptible E. coli strain isogenic with the KPC-3–producing isolate, which suggests horizontal interspecies plasmid transfer.  相似文献   
48.
PurposeTo study whether the application of femtosecond laser pulses for zona pellucida (ZP) drilling of blastocysts at the embryonic or abembryonic poles can promote hatching to start immediately through the hole formed and ensure high hatching rates and embryo viability.MethodsMouse blastocyst (E3.5) ZP were microdissected with femtosecond laser pulses (514-nm wavelength, 280-fs pulse duration, 2.5-kHz repetition rate) close to the trophoblast or inner cell mass (ICM). The sizes of the holes formed were in the range of 4.5–8.5 μm. Additional longitudinal incisions (5–7-μm long) on either side of the hole were created to determine whether hatching had started at the correct position. Embryos post-laser-assisted ZP drilling and intact embryos were cultured under standard conditions for 2 days; embryo quality was assessed twice daily. The hatching rates and in vitro and in vivo implantation rates (only for embryos with ZP dissected close to the ICM) were estimated.ResultsFemtosecond laser–assisted ZP drilling at the early blastocyst stage facilitated embryo hatching to start at the artificial opening with probability approaching 100%. Despite the artificial opening’s small size, no embryo trapping during hatching was observed. Both experimental groups had higher hatching rates than the control groups (93.3–94.7% vs. 83.3–85.7%, respectively). The in vitro implantation rate was comparable with that of the control group (92.3% vs. 95.4%). No statistically significant differences were obtained in the in vivo implantation rates between the experimental and control groups.ConclusionsBlastocyst-stage femtosecond laser microsurgery of ZP is fast and delicate and enables the hatching process to be initiated in a controlled manner through a relatively small opening, with no embryo trapping.  相似文献   
49.
50.
The epidemiology of the mental and physical health of children and adolescents the world over reflects: the genomes they inherit (and the modifications those genes undergo in utero); the pregnancies that led to their births, whether their mothers survive those pregnancies, and whether their births were welcome; the parents, the neighbors, and the neighborhoods they 'inherit' along with their genomes; when and where they live (by cohort, by country, and by province); the air they breathe; the water they drink; what and how much they eat; the schools they attend (and by whom they are taught what and for how long); the energy they expend; the family status in the social order; the friends they have; and last but not least, the amount and kind of medical and psychiatric care they receive.  相似文献   
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