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   3244篇
  免费   150篇
  国内免费   19篇
耳鼻咽喉   35篇
儿科学   41篇
妇产科学   55篇
基础医学   380篇
口腔科学   75篇
临床医学   223篇
内科学   873篇
皮肤病学   64篇
神经病学   274篇
特种医学   188篇
外科学   461篇
综合类   13篇
一般理论   1篇
预防医学   166篇
眼科学   33篇
药学   213篇
中国医学   3篇
肿瘤学   315篇
  2023年   32篇
  2022年   75篇
  2021年   119篇
  2020年   48篇
  2019年   47篇
  2018年   93篇
  2017年   61篇
  2016年   73篇
  2015年   75篇
  2014年   107篇
  2013年   126篇
  2012年   229篇
  2011年   228篇
  2010年   100篇
  2009年   113篇
  2008年   190篇
  2007年   201篇
  2006年   174篇
  2005年   203篇
  2004年   165篇
  2003年   164篇
  2002年   161篇
  2001年   60篇
  2000年   53篇
  1999年   54篇
  1998年   39篇
  1997年   25篇
  1996年   19篇
  1995年   20篇
  1994年   14篇
  1993年   9篇
  1992年   21篇
  1991年   18篇
  1990年   32篇
  1989年   16篇
  1988年   29篇
  1987年   24篇
  1986年   25篇
  1985年   18篇
  1984年   21篇
  1983年   14篇
  1981年   8篇
  1980年   6篇
  1979年   10篇
  1978年   8篇
  1977年   8篇
  1976年   9篇
  1975年   8篇
  1974年   9篇
  1973年   8篇
排序方式: 共有3413条查询结果,搜索用时 15 毫秒
121.

Background

Although schizophrenia and major depressive disorder (MDD) differ on a variety of neuroanatomical measures, a diagnostic tool to discriminate these disorders has not yet been established. We tried to identify structural changes of the brain that best discriminate between schizophrenia and MDD on the basis of gray matter volume, ventricle volume, and diffusion tensor imaging (DTI).

Method

The first exploration sample consisted of 25 female patients with schizophrenia and 25 females with MDD. Regional brain volumes and fractional anisotropy (FA) values were entered into a discriminant analysis. The second validation sample consisted of 18 female schizophrenia and 16 female MDD patients.

Results

The stepwise discriminant analysis resulted in correct classification rates of 0.80 in the schizophrenic group and 0.76 in MDD. In the second validation sample, the obtained model yielded correct classification rates of 0.72 in the schizophrenia group and 0.88 in the MDD group.

Conclusion

Our results suggest that schizophrenia and MDD have differential structural changes in the examined brain regions and that the obtained discriminant score may be useful to discriminate the two disorders.  相似文献   
122.
To identify fetuses at high risk of poor neurological outcomes using a novel ultrasound evaluation system. We assessed an ultrasound evaluation system based on our previous findings, consisting of screening for decreased or lack of fetal movements, abnormal patterns of fetal heart rate, congenital CNS malformations, polyhydramnios of unknown cause, and a “brief ultrasound evaluation” of fetal brain functions, including movement of extremities, breathing movements, ultradian rhythm, REM period, and NREM period. We then assessed the correlation between fetal brain functions and neurological outcomes in infancy (MR, CP, and low Developmental Quotient). During screening, we prospectively evaluated 4978 fetuses receiving prenatal and intrapartum management between January 2000 and December 2009 in our hospital that were later delivered between 32 and 41 weeks’ gestation and identified 93 cases as suspicious for impairment. Of the 93 fetuses, 26 underwent the second step of brief ultrasound examination at 35–40 weeks’ gestation. Our findings revealed that this method was adequately sensitive (80%) and specific (88%) in identifying neurological impairment. We concluded that this method was mainly useful in the clinical setting for establishing the first indication for fetal CNS examination for functional impairment, rendering it suitable for clinical application.  相似文献   
123.
124.

Purpose

We devised a simple dichotomous classification system and showed sufficient reproducibility to indicate treatment strategies for peritoneal metastasis of colorectal cancer.

Methods

We included 67 patients with peritoneal metastasis of colorectal cancer and classified them according to the largest lesion size, number of lesions and number of regional peritoneal metastases. The oncological data were recorded and compared.

Results

According to the univariate analyses, the prognoses were significantly better in patients with ≤3 disseminated lesions than in those with ≥4, and in patients with disseminated lesions in only one region than in those with ≥2 lesions. A multivariate analysis showed that primary tumor resection and the presence of peritoneal metastases in only one region were favorable factors for the patient survival. Patients with disseminated lesions in only one region (localized group) and those with nonlocalized lesions had three-year survival rates of 45.6 and 12.2 %, respectively. Finally, primary tumor resection improved the prognoses in both the localized and nonlocalized groups.

Conclusions

Colorectal cancer patients were categorized into localized and nonlocalized groups according to the number of regions with peritoneal metastasis, and significant prognostic associations were demonstrated. Subsequent analyses of the oncological data suggested that primary tumor resection contributes to an improved prognosis in all patients with synchronous peritoneal metastases.
  相似文献   
125.
126.
127.
Cysteine peptidases have potent activities in the pathogenesis of various parasitic infections. Two cDNA clones encoding cysteine peptidases were isolated from Echinococcus multilocularis metacestode (EmCLP1 and EmCLP2). EmCLP1 and EmCLP2 shared high similarity to the cathepsin L-like peptidases. Immunoblot analyses demonstrated that native EmCLP1 and EmCLP2 were present in excretory/secretory products and extracts of E. multilocularis metacestodes. By immunohistochemistry, native EmCLP1 and EmCLP2 were shown to localize to the germinal layer, the brood capsule and the protoscolex. Recombinant EmCLP1 and EmCLP2 expressed in Saccharomyces cerevisiae exhibited substrate specificity against synthetic peptidyl substrates, Z-Leu-Arg-MCA and Z-Phe-Arg-MCA. Furthermore, recombinant enzymes degraded IgG, albumin, type I and IV collagens, and fibronectin, which suggested those key roles in parasite-host interactions. This is the first report of cysteine peptidases from E. multilocularis, and would contribute to control E. multilocularis infections by chemotherapeutic drugs and/or immunoprophylaxis.  相似文献   
128.
In the past few years, the plasticity of the regional specification of the CNS has been widely debated on the results from in utero transplantation. Two different results are reported with this transplantation method. One is that the distribution of transplanted cells is dependent on the donor origin, and the other is that the distribution is independent on the donor cell origin. The present study attempted to examine closely the plasticity of the regional specification by in utero transplantation method with clonal neural cell lines, 2Y-3t and 2Y-5o2b. These lines were established from a cerebellum of an adult p53-deficient mouse. Our results showed that transplanted cells migrated into various regions of the CNS and supported the independent distribution. Moreover, different distribution patterns of transplanted cells were observed between host sexes. Labeled cells were localized around the ventricle of neonatal host brains, where they were undifferentiated. In 2-3 weeks after birth, labeled cells were found in the brain parenchyma and some of them took neuronal morphology. In the rostral migratory stream (RMS), cells with unipolar or bipolar morphology were still undifferentiated. In other regions, labeled cells were often associated with blood vessels; the soma were on the surface of vessels, extending processes or neurites into surrounding brain parenchyma. Time-lapse imaging demonstrated that they were migrating with blood vessels.  相似文献   
129.
Angiogenesis is essential for bone formation and several bone morphogenetic proteins (BMPs) have been shown to induce angiogenesis through osteoblast-derived vascular endothelial growth factor (VEGF)-A. Growth differentiation factor-5 (GDF-5) is a member of the BMP family expressed in bone and known to induce angiogenesis in vivo. In this study, the effects of GDF-5 on osteogenic differentiation and expression of VEGF-related genes were determined using rat bone marrow stromal cells. GDF-5 stimulated osteogenic differentiation. It also upregulated the expression of VEGF-A after 3 hr, accompanied by a trend of decrease in its receptor VEGFR-2 at 6 and 24 hr. VEGF-D and its receptor VEGFR-3 showed peak expression at later time points. This regulation may be further controlled by neuropilin 2 that exhibited a parallel profile to VEGF-D. These observations indicate that GDF-5 stimulates osteogenic differentiation and has a potential to induce angiogenesis through osteoblast-derived VEGF-A in bone.  相似文献   
130.
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