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   13198篇
  免费   824篇
  国内免费   79篇
耳鼻咽喉   183篇
儿科学   453篇
妇产科学   469篇
基础医学   1245篇
口腔科学   410篇
临床医学   1148篇
内科学   2799篇
皮肤病学   206篇
神经病学   645篇
特种医学   476篇
外科学   2478篇
综合类   464篇
现状与发展   1篇
一般理论   14篇
预防医学   892篇
眼科学   348篇
药学   1018篇
中国医学   83篇
肿瘤学   769篇
  2023年   135篇
  2022年   422篇
  2021年   620篇
  2020年   354篇
  2019年   442篇
  2018年   556篇
  2017年   334篇
  2016年   433篇
  2015年   453篇
  2014年   582篇
  2013年   773篇
  2012年   1035篇
  2011年   1012篇
  2010年   571篇
  2009年   446篇
  2008年   707篇
  2007年   767篇
  2006年   705篇
  2005年   607篇
  2004年   550篇
  2003年   459篇
  2002年   423篇
  2001年   140篇
  2000年   142篇
  1999年   119篇
  1998年   75篇
  1997年   60篇
  1996年   48篇
  1995年   44篇
  1994年   49篇
  1993年   31篇
  1992年   95篇
  1991年   62篇
  1990年   81篇
  1989年   65篇
  1988年   51篇
  1987年   56篇
  1986年   31篇
  1985年   50篇
  1984年   33篇
  1983年   47篇
  1982年   25篇
  1980年   23篇
  1979年   37篇
  1978年   23篇
  1977年   30篇
  1974年   37篇
  1973年   35篇
  1972年   27篇
  1967年   21篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The aim of this study was to assess cellular immunological changes in HIV infected and non-infected normal pregnancies. This was a cross-sectional study of women in the three trimesters of pregnancy and the postpartum period. All participants were asymptomatic. This study showed that absolute numbers of CD4 counts in the HIV infected group were significantly lower than that in the non-infected group, for all periods of gestation studied. The CD8 counts were found to increase postdelivery and may have clinical significance in relation to mother to child transmission. This needs further study with a larger sample size and a longitudinal design method of study.  相似文献   
72.
In this study we outline a method for constructing an inexpensive chamber used in the transfection of organotypic brain slices. This chamber differs from most commercially available chambers in that DNA-coated gold microcarriers are directly carried by a flow of helium at low pressure (26 psi). Most other chambers employ macrocarriers onto which DNA-coated gold is first loaded, and then released by a shock of helium onto the reverse side of the macrocarriers. This home constructed device has been successfully employed in the transfection of organotypic brain slices cultured using the air-medium interface method. Mammalian expression vectors containing cytomegalovirus (CMV) and simian virus (SV40) enhancers/promoters were used to express enhanced green fluorescence protein (EGFP). DNA was coated onto 0.6-microm gold microcarriers. Transfected cells were visualised under a fluorescence microscope and included identifiable neurones and oligodendrocytes. Also included in this study are step-by-step methods for the preparation of gold microcarriers and organotypic brain slices.  相似文献   
73.
PURPOSE: The objective of this study was to determine whether the addition of trastuzumab to chemotherapy in the neoadjuvant setting could increase pathologic complete response (pCR) rate in patients with human epidermal growth factor receptor 2 (HER2) -positive disease. PATIENTS AND METHODS: Forty-two patients with HER2-positive disease with operable breast cancer were randomly assigned to either four cycles of paclitaxel followed by four cycles of fluorouracil, epirubicin, and cyclophosphamide or to the same chemotherapy with simultaneous weekly trastuzumab for 24 weeks. The primary objective was to demonstrate a 20% improvement in pCR (assumed 21% to 41%) with the addition of trastuzumab to chemotherapy. The planned sample size was 164 patients. RESULTS: Prognostic factors were similar in the two groups. After 34 patients had completed therapy, the trial's Data Monitoring Committee stopped the trial because of superiority of trastuzumab plus chemotherapy. pCR rates were 25% and 66.7% for chemotherapy (n = 16) and trastuzumab plus chemotherapy (n = 18), respectively (P = .02). The decision was based on the calculation that, if study continued to 164 patients, there was a 95% probability that trastuzumab plus chemotherapy would be superior. Of the 42 randomized patients, 26% in the chemotherapy arm achieved pCR compared with 65.2% in the trastuzumab plus chemotherapy arm (P = .016). The safety of this approach is not established, although no clinical congestive heart failure was observed. A more than 10% decrease in the cardiac ejection fraction was observed in five and seven patients in the chemotherapy and trastuzumab plus chemotherapy arms, respectively. CONCLUSION: Despite the small sample size, these data indicate that adding trastuzumab to chemotherapy, as used in this trial, significantly increased pCR without clinical congestive heart failure.  相似文献   
74.
A simple high throughput micro-fluorescence in situ hybridisation technique (FISH) was used to detect chromosome 13 deletions (delta13), immunoglobulin heavy chain (IgH) rearrangements, t(11;14)(q13;q32), t(4;14)(p16;q32), t(14;16)(q23;q32), p53 loss, and numerical changes of chromosomes 3, 6, 7, 9, 10, 11 and 17 in 228 cases of multiple myeloma (MM), including 33 asymptomatic/smouldering MM (SMM). The patients were not part of a clinical trial and were from 30 different hospitals. In all, 98.4% of cases were abnormal, with 43% having IgH rearrangements and 42% Delta13. The low incidence of IgH rearrangements was due to a decrease in this finding with age (P = 0.001) and the relatively high proportion of elderly patients in our study population (41% >70 years old). The incidence of specific IgH translocations was t(4;14) 11%, t(11;14) 16% and t(14;16) 3%. Univariate statistical testing showed delta13 (P = 0.002), and t(14;16) (P = 0.005) to be associated with shorter survival. This effect was exaggerated for patient's aged 70 years or under but no effect on survival was seen for those over 70 years. In younger patients t(4;14) (P = 0.044) and p53 deletion (P < 0.001) were also significant poor prognostic indicators. Multivariate analysis showed delta13 and t(14;16) to be independent prognostic variables when considered with age and clinical parameters.  相似文献   
75.
Between January 1993 and December 2000, an unrelated donor search (UDS) was initiated for 97 consecutive patients [46 acute lymphoblastic leukemia (ALL) and 51 acute myeloid leukemia (AML)]. Leukemia was considered to be of poor prognosis in cases of refractory disease (n=70), unfavourable karyotype (n=22) or miscellaneous (n=5). All patients had previously received various chemotherapies and 9 had undergone an autologous stem cell transplantation (SCT). The median age at UDS initiation was 25 (range 2.7-55) years. The median time to identify a suitable living donor or cord blood (CB) was 60 days. Eventually, 33 patients received unrelated allo-SCT (including 9 CB), 12 auto-SCT, 39 chemotherapy and 13 palliative treatment. At a median of 54 months, 18 patients were alive, including 15 in remission. The 4-year overall survival rates were 32%, 37%, 15% and 0% for allo-SCT, auto-SCT, chemotherapy or palliative treatment, respectively. Patients who received either allo- or auto-SCT had better survival than those who did not (P<0.0001). For ALL, only allo-SCT significantly improved survival (P<0.007). Finally, patients who received allo-SCT died less often of relapse than patients who did not (P<0.0001). Unrelated allo-SCT gives a substantial long-term survival and cure in patients with high-risk acute leukemia. For patients who achieve remission and for whom UDS fails, auto-SCT may prove to be a good approach. For patients who fail to enter into remission, intensive salvage chemotherapy has a very limited effect.  相似文献   
76.
PURPOSE: To determine the efficacy and safety of a newly developed concomitant administration of fludarabine and alemtuzumab (FluCam) in patients with relapsed or refractory B-cell chronic lymphocytic leukemia (B-CLL). PATIENTS AND METHODS: A total of 36 patients were treated in this phase II study (median age, 61.47 years; mean number of prior chemotherapies, 2.6; Binet stage C, n = 28). After an initial dose escalation of alemtuzumab over 3 days, alemtuzumab 30 mg and fludarabine 30 mg/m2 were administered on 3 consecutive days. Treatment was repeated after 28 days for up to six cycles. Restaging (following National Cancer Institute criteria) was carried out after cycles 2 and 4 and 1 month after the end of treatment. RESULTS: The overall response rate was 83% (11 complete responses, 19 partial responses, one stable disease, and five progressive diseases). Two patients with progressive disease developed fungal pneumonias, and one patient died as a result of Escherichia coli sepsis. Two subclinical cytomegalovirus reactivations occurred. CONCLUSION: The new FluCam regimen is effective and feasible in patients with relapsed and refractory B-CLL.  相似文献   
77.
Serum beta2-microglobulin, the light chain of the HLA class I molecular complex, remains one of the best survival prognostic factors in multiple myeloma, but other HLA class I molecules might be of interest in monoclonal gammopathies. In this study, we evaluate total soluble HLA class I (HLA-Is) and soluble HLA-G (HLA-Gs) in 103 patients with newly diagnosed multiple myeloma, 30 patients with monoclonal gammopathy of undetermined significance (MGUS), and 30 healthy subjects, studying their prognostic value in multiple myeloma. In multiple myeloma patients, HLA-Is and HLA-Gs median values were 0.8 microg/mL and 28 ng/mL, respectively. Median HLA-Is concentration was higher in stage II and III multiple myeloma patients than in stage I multiple myeloma, MGUS, and control patients. Median HLA-Gs was significantly lower in healthy controls than in MGUS and multiple myeloma patients. A high level of HLA-Is (> or =2.1 microg/mL) was predictive of short survival (P = 0.017). For each given level of beta2-microglobulin, the relative risk of death was higher for patients with HLA-Is > or = 2.1 microg/mL than in patients with a lower level (P = 0.047). HLA-Gs, a marker of monoclonal gammopathy, was of no prognostic value, but the addition of HLA-Is to beta2-microglobulin produced an efficient prognostic score (P < 0.0001). HLA-Is is a new marker of multiple myeloma tumor load and provides additional survival prognostic information to beta2-microglobulin.  相似文献   
78.
Objective: To assess the pharmaceutical sector to know whether people have access to essential medicines. Setting: The study was conducted in 20 public health clinics, five public district drug stores and 20 private retail pharmacies selected randomly in five different areas randomly selected (four states and a federal territory). Method: The methodology used was adopted from the World Health Organization study protocol. The degree of attainment of the strategic pharmaceutical objectives of improved access is measured by a list of tested indicators. Access is measured in terms of the availability and affordability of essential medicines, especially to the poor and in the public sector. The first survey in the public health clinics and public district drug stores gathered information about current availability of essential medicines, prevalence of stock-outs and affordability of treatment (except drug stores). The second survey assessed affordability of treatment in public health clinics and private retail pharmacies. Main Outcome Measure Availability, stock-out duration, percent of medicines dispensed, accessibility and affordability of key medicines. Results The average availability of key medicines in the public health clinics for the country was 95.4%. The average stock-out duration of key medicines was 6.5 days. However, average availability of key medicines in the public district drug stores was 89.2%; with an average stock-out duration of 32.4 days. Medicines prescribed were 100% dispensed to the patients. Average affordability for public health clinics was 1.5 weeks salary and for the private pharmacies, 3.7 weeks salary. Conclusions: The present pharmaceutical situation in the context of essential medicines list implementation reflected that the majority of the population in Malaysia had access to affordable essential medicines. If medicines need to be obtained from the private sector, they are hardly affordable. Although the average availability of essential medicines in Malaysia was high being more than 95.0%, in certain areas in Sabah availability was less than 80.0% and still a problem.  相似文献   
79.
Label-free metabolic imaging of non-alcoholic fatty liver disease (NAFLD) mouse liver is demonstrated ex vivo by dynamic optical coherence tomography (OCT). The NAFLD mouse is a methionine choline-deficient (MCD)-diet model, and two mice fed the MCD diet for 1 and 2 weeks are involved in addition to a normal-diet mouse. The dynamic OCT is based on repeating raster scan and logarithmic intensity variance (LIV) analysis that enables volumetric metabolic imaging with a standard-speed (50,000 A-lines/s) OCT system. Metabolic domains associated with lipid droplet accumulation and inflammation are clearly visualized three-dimensionally. Particularly, the normal-diet liver exhibits highly metabolic vessel-like structures of peri-vascular hepatic zones. The 1-week MCD-diet liver shows ring-shaped highly metabolic structures formed with lipid droplets. The 2-week MCD-diet liver exhibits fragmented vessel-like structures associated with inflammation. These results imply that volumetric LIV imaging is useful for visualizing and assessing NAFLD abnormalities.  相似文献   
80.
目的分析神香草药材中挥发油的化学组分。方法用气相色谱-质谱联用技术系统分析神香草中挥发油的成分,每一组分根据峰面积归一法计算其含量。结果共鉴定出36种成分,占总油量的96%,其中D-大叶香根烯的含量最高,达18.67%。结论D-大叶香根烯可作为同属植物鉴别的依据。  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