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   7267篇
  免费   635篇
  国内免费   10篇
耳鼻咽喉   113篇
儿科学   245篇
妇产科学   238篇
基础医学   1090篇
口腔科学   212篇
临床医学   688篇
内科学   1200篇
皮肤病学   90篇
神经病学   503篇
特种医学   156篇
外科学   953篇
综合类   153篇
一般理论   1篇
预防医学   1360篇
眼科学   97篇
药学   506篇
中国医学   8篇
肿瘤学   299篇
  2019年   76篇
  2018年   114篇
  2017年   70篇
  2016年   76篇
  2015年   90篇
  2014年   154篇
  2013年   181篇
  2012年   259篇
  2011年   283篇
  2010年   154篇
  2009年   157篇
  2008年   255篇
  2007年   287篇
  2006年   250篇
  2005年   244篇
  2004年   230篇
  2003年   195篇
  2002年   220篇
  2001年   245篇
  2000年   259篇
  1999年   179篇
  1998年   118篇
  1997年   130篇
  1996年   141篇
  1995年   175篇
  1994年   81篇
  1993年   88篇
  1992年   203篇
  1991年   211篇
  1990年   180篇
  1989年   125篇
  1988年   139篇
  1987年   146篇
  1986年   132篇
  1985年   139篇
  1984年   135篇
  1983年   106篇
  1982年   95篇
  1981年   80篇
  1980年   88篇
  1979年   131篇
  1978年   94篇
  1977年   87篇
  1976年   67篇
  1974年   86篇
  1973年   87篇
  1972年   83篇
  1971年   90篇
  1970年   98篇
  1969年   80篇
排序方式: 共有7912条查询结果,搜索用时 15 毫秒
31.
PURPOSE: The presence of similar histologic subtypes of epithelial ovarian and endometrial cancers has long been noted, although the relevance of this finding to pathogenesis and clinical management is unclear. Despite similar clinical characteristics, histologic subtypes of cancers of the ovary and endometrium are treated according to organ of origin. This study compares the gene expression profiles of analogous histologic subtypes of cancers of the ovary and endometrium using the same genomic platform to determine the similarities and differences between these tumors. EXPERIMENTAL DESIGN: Gene expression profiles of 75 cancers (endometrioid, serous, and clear cell) of the ovary and endometrium, five renal clear cell cancers, and seven normal epithelial brushings were determined using a 11,000-element cDNA array. All images were analyzed using BRB ArrayTools. Validation was done using real-time PCR on select genes and immunohistochemical staining. RESULTS: Comparison across endometrial and ovarian cancers and serous and endometrioid tumors showed expression patterns reflecting their organ of origin. Clear cell tumors, however, showed remarkably similar expression patterns regardless of their origin, even when compared with renal clear cell samples. A set of 43 genes was common to comparisons of each of the three histologic subtypes of ovarian cancer with normal ovarian surface epithelium. CONCLUSIONS: The comparison of the gene expression profiles of endometrioid and serous subtypes of ovarian and endometrial cancer are largely unique to the combination of a particular subtype in a specific organ. In contrast, clear cell cancers show a remarkable similarity in gene expression profiles across organs (including kidney) and could not be statistically distinguished.  相似文献   
32.
33.
Various patterns of ankle fractures that are not accounted for by common classification systems have been the subject of case reports. The first difficulty with these variant patterns is recognizing all associated pathology, followed by the successful application of stable fixation. The purpose of this study was to describe the common morphologic features and ligamentous injuries of a unique variant fracture pattern, as well as the surgical treatment technique and the short-term functional and radiographic outcomes. Of 121 consecutive unstable ankle fractures over a 2-year period, 7 patients were found to have a similar constellation of injuries around the ankle. A vertical shear fracture of the posteromedial tibial rim was the main feature. Six of the 7 also had a fracture of the posterior malleolus. On magnetic resonance imaging, the deltoid and posterior tibiofibular ligaments were intact in all cases. Fractures were treated with open anatomic reduction of the posteromedial and posterior fragments with antiglide plate fixation. All fractures healed at 2 months without loss of reduction, fixation failure, or surgical complications. The average American Academy of Orthopaedic Surgeons lower extremity score was 79 at an average of 8 months' follow-up. The common radiographic and morphologic features associated with this posteromedial fracture indicate that it likely occurs through a common mechanism that involves hyperplantarflexion. The characteristics of this fracture pattern have not been fully described previously, but this ankle fracture variant may occur in up to 6% of cases. Unstable ankle fractures should be evaluated carefully for evidence of posteromedial involvement so appropriate treatment may proceed.  相似文献   
34.
The objectives of this study were: (a) to observe and describe the variability of bone healing in implant receptor sites which were prepared in rabbit femurs by use of different surgical methods; and (b) to determine if the animal model which was used was suitable for the detection of differences in healing reactions in implant receptor sites which were prepared by different surgical methods. Three 3-mm-wide implant receptor sites were prepared in the right and left femurs of four large New Zealand white rabbits. The surgical parameters used in preparation of the different sites included: low speed with no irrigation (LSO); low speed with internal irrigation only (LSI); low speed with external irrigation only (LSE); high speed with no irrigation (HSO); or high speed with external irrigation only (HSE). The sites were randomized so that each animal had one of each type of site in either the right or left femur. A non-treated control site was located in each animal for comparison with experimental sites. The animals were killed at 7, 14, 21, and 28 days post-operatively. The resultant samples were fixed, embedded, sectioned, and stained with basic fuchsin and toluidine blue. The results indicated that this was probably not a suitable animal model, since no discernible differences were detected in the various healed sites.  相似文献   
35.
Recall of eight childhood communicable diseases and other illnesses was validated among 95 adults by comparison to longitudinal childhood health records. Self-reports at age 50 of several illnesses were highly accurate; however, German measles was correctly recalled by only 34% of subjects. Similar levels of accuracy were consistently found among a subset who also completed health history interviews 8 and 20 years earlier. Over-reporting of some health events was common. Past exposure to viral or bacterial agents is sometimes assessed in case-control studies by self-reports. Misclassification of prior exposure due to faulty recall may distort true associations between childhood illness and chronic disease in later life.  相似文献   
36.
Ultrastructural aspects of St. Louis encephalitis virus infection of the major extraneutral organs and tissues of suckling hamsters were examined. In the pancreas, both the exocrine and endocrine portions were equally affected by the virus. A feature apparently unique to flaviviruses was the accumulation of virus particles in all types of secretory granules in this organ. Virus particles were seen within myocardial fibers and within the smooth muscle cells and endothelial cells of small blood vessels of the heart. In the intestines, the lamina propria was the most severely infected, with virus particles accumulated in all cell types.  相似文献   
37.
38.
Primary amyloidosis of the renal pelvis   总被引:1,自引:0,他引:1  
  相似文献   
39.
The functional activities of IgG and IgM anti-A and anti-B   总被引:3,自引:0,他引:3  
The rate constants for association and dissociation, and the equilibrium constants, were determined for 125I-labelled anti-A and anti-B of both IgG and IgM molecular types. The following results and conclusions were obtained:

1. The equilibrium constants were within the range 06×108–13.0×108 l/mole, and were of the same order for both IgG and IgM antibodies.

2. The initial rate constants for association were in the range 2.1×105–4.8×105 l/mole/sec, and the energy of activation (Ea) 6700–9000 cal/mole. These results indicate that the rate of association is approaching the limit set by the rate of diffusion of the reactants.

3. The initial rate constants for dissociation were 1 × 10-4–5 × 10-4/sec and Ea = 20,000–36,000 cal/mole. These latter values suggest that more than one bond must be broken simultaneously during dissociation.

4. Ionic strength and pH changes have only a minor effect on the constants; this indicates absence of ionic groups on A and B antigen sites.

5. The changes in enthalpy were –5400 to –21,800 cal/mole; the reactions are mainly enthalpy driven and this accounts for the fact that anti-A and anti-B agglutination titres increase as the temperature is decresed.

6. There was heterogeneity of the values of the standard change in free energy, enthalpy and entropy within each example of antibody.

7. The approximate concentrations of antibody at the end-points of the agglutination titres were: for IgG antibody, 0.2 μg/ml; for IgM antibody, 0.01 μg/ml.

  相似文献   
40.
A further modification of the standard RPHA technique (Hepatest, Wellcome Reagents) for the detection of HBsAg is described. This modification does not require a centrifugation step which is required by the other modifications that have been described previously and consequently takes a little longer to perform. It does, however, retain the advantages of increased sensitivity and decreased costs which are also features of the other modifications. A series of 939 routine clinical specimens were used to evaluate the method described and to evaluate a new RIA kit for the detection of HBsAg (Hepatube, Wellcome Reagents). Of 53 specimens found to be positive for HBsAg by RIA, 50 (94% were detected by the modified Hepatest RPHA as opposed to 47 (89%) by the standard technique.  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