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   22313篇
  免费   1745篇
  国内免费   87篇
耳鼻咽喉   331篇
儿科学   625篇
妇产科学   566篇
基础医学   3148篇
口腔科学   506篇
临床医学   2042篇
内科学   5097篇
皮肤病学   251篇
神经病学   2036篇
特种医学   677篇
外科学   3545篇
综合类   312篇
一般理论   17篇
预防医学   1665篇
眼科学   591篇
药学   1198篇
中国医学   41篇
肿瘤学   1497篇
  2023年   194篇
  2022年   402篇
  2021年   799篇
  2020年   421篇
  2019年   634篇
  2018年   762篇
  2017年   495篇
  2016年   500篇
  2015年   621篇
  2014年   814篇
  2013年   1067篇
  2012年   1551篇
  2011年   1580篇
  2010年   876篇
  2009年   736篇
  2008年   1307篇
  2007年   1278篇
  2006年   1276篇
  2005年   1213篇
  2004年   1110篇
  2003年   973篇
  2002年   969篇
  2001年   202篇
  2000年   162篇
  1999年   202篇
  1998年   186篇
  1997年   179篇
  1996年   144篇
  1995年   129篇
  1994年   129篇
  1993年   116篇
  1992年   120篇
  1991年   111篇
  1990年   124篇
  1989年   112篇
  1988年   122篇
  1987年   117篇
  1986年   84篇
  1985年   107篇
  1984年   106篇
  1983年   104篇
  1982年   136篇
  1981年   126篇
  1980年   164篇
  1979年   80篇
  1978年   89篇
  1977年   81篇
  1976年   84篇
  1975年   63篇
  1974年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Monocytoid B-cell lymphoma: a study of 36 cases   总被引:3,自引:0,他引:3  
We have studied 36 cases of monocytoid B-cell lymphoma (MBCL). We confirm the predilection for females (30 of 36; ratio, five women to one man). The median age was 65 years (range, 29 to 85 years). Monocytoid B-cell lymphoma characteristically involves peripheral lymph nodes (30 of 36) with a propensity for paraparotid or intraparotid nodes. Salivary glands were affected in five patients. Other extranodal sites of involvement included breast, thyroid, stomach, and soft tissue of chest wall. Eight patients manifested with Sj?gren's syndrome, one had systemic lupus erythematosus, one presented initially with Raynaud's phenomenon, and two had a monoclonal gammopathy. "Composite lymphomas" were encountered in seven patients. In addition, association with or progression to a higher-grade lymphoma, ie, mixed small and large cell (one) and large cell (six), was observed in seven patients and was associated with a more aggressive behavior of the lymphoma. Immunohistochemical studies performed on biopsy sections from 20 patients confirmed the B-cell nature of MBCL. An average reactivity of less than 10% of the monocytoid B cells with the proliferation marker Ki-67 was demonstrated, in keeping with the indolent behavior of MBCL. Despite our observation of follicular lymphomas frequently accompanying MBCL, the t(14;18) chromosomal translocation does not appear to play a pathogenetic role for MBCL, as determined by molecular studies for the t(14;18) chromosomal translocation and immunologic studies for the BCL2 protein. Our observations also provide support for the proposal that there is an overlap between MBCL and "MALT lymphomas" (those arising from mucosa-associated lymphoid tissue).  相似文献   
82.
The clinical laboratory is regarded as a component of the medical care system extending from physician to laboratory staff and back to physician. From this concept a computer-based system of laboratory information is derived, emphasizing: (1) total laboratory responsibility for the test and its request, and (2) physician-oriented output reports.  相似文献   
83.
B A Belli  C E Samuel 《Virology》1991,185(2):698-709
Polyclonal monospecific antibody was prepared against the reovirus serotype 1 Lang strain nonstructural sigma 1NS protein encoded by the S1 gene. The antibody was serotype-specific. The sigma 1NS protein of reovirus serotype 1, but not reovirus serotype 3, was recognized by the polyclonal antibody in both immunoprecipitation and Western immunoblot assays. The sigma 1NS protein expressed in vector-transfected COS cells was indistinguishable by immunoprecipitation and immunoblot analyses from the authentic sigma 1NS protein synthesized in virus-infected mouse L or monkey COS cells. The temporal appearance of sigma 1NS protein in virus-infected cells was similar to that of the other reovirus proteins. Both sigma 1NS and sigma 1, the two S1 gene products, were observed in the cytoplasm of COS cells by immunofluorescent microscopy, although their staining patterns were distinct from each other. However, sigma 1NS, but not sigma 1 or the other reovirion structural proteins, was also detected in the nucleoli of COS cells. These results suggest that sigma 1NS, like sigma 1, is a serotype-specific reovirus protein, but unlike sigma 1 is localized in part to the cell nucleus.  相似文献   
84.
How medical students are taught physical examination (PE) skills appears to have changed little since the 1950s. Textbooks are organized according to organ systems and describe methods of eliciting and recording history and PE data using a routine format. In many medical schools, the preclinical teaching programs for clinical examination skills similarly emphasize an orderly collection of data. Teaching students to use diagnostic reasoning is postponed until students have learned history-taking and PE skills. The authors propose three modifications to this educational approach. First, rather than performing the clinical examination using a routine format, students should be encouraged to form diagnostic hypotheses early on while listening to the patient's narrative, and conduct the subsequent search for history and PE data in a reflective way in order to confirm or refute these hypotheses. Second, the authors propose that interviewing patients and conducting the PE be taught by one-on-one tutoring until students achieve mastery. Last, they suggest that the PE be guided not only by students' diagnostic hypotheses, but also by patients' expectations. These modifications are consistent with current trends in medical education that encourage a reflective practice and problem-based learning (PBL), and they also introduce medical students to the precepts of clinical reasoning. The authors suggest that challenging students to seek specific physical findings may increase the likelihood of detecting findings when they are present, and may transform patient interviewing and conducting the PE from routine activities into intellectually exciting experiences.  相似文献   
85.
BACKGROUND: Aerosolization of fish proteins during seafood processing has been identified as a potential route for allergic sensitization and occupational asthma among workers involved in high-risk activities. The aim of this study was to develop immunological assays for the quantification of aerosolized fish antigens in a fish-processing factory. METHODS: Polyclonal antibodies to the main fish species processed in the factory (anchovy and pilchard) were generated in rabbits and compared by ELISA inhibition assay and immunoblotting. These antisera were utilized to develop ELISA assays for the detection of fish antigens. The ELISA inhibition assays were evaluated by analyzing environmental air samples collected from three areas in a fish-processing factory: pilchard canning, fish meal production and lobster processing. RESULTS: By immunoblotting, the rabbit polyclonal antibodies demonstrated IgG antibody binding patterns comparable with IgE antibodies of fish-sensitized patients, particularly in regard to the major fish allergens parvalbumins. The sensitivity of the fish-specific ELISA assays developed was 0.5 microg/ml. The ELISA inhibition assays were able to differentiate between the two different fish species of interest but did not recognize a crustacean species. Notable differences in exposure levels to canned pilchard and anchovy antigens were demonstrated in the three different working areas of the factory, with assays having a detection limit as low as 105 ng/m(3). CONCLUSION: These ELISA-based assays are sensitive and specific to quantify differential exposure levels to fish antigens produced during fish processing, making it possible to investigate exposure-disease response relationships among workers in this industry.  相似文献   
86.
An implementation trial of leukocyte-reduced transfusions in cardiac surgery (primary coronary artery bypass graft and valve replacement) was performed from July to December 1998; comparisons were made with data from the same period in 1997. Patients from both periods were similar in important preoperative and intraoperative variables (age, sex, weight, number of units of RBCs transfused, ejection fraction). The mean total number of complications was statistically significantly decreasedfrom 0.26 complications per patient in the non-leukocyte-reduced to 0.19 in the leukocyte-reduced recipients. Overall, the mean +/- ISD costs of care per patient decreasedfrom 1997 ($27,615 +/- $33,973) to 1998 ($27,038 +/- $24,107). Mean costs decreased $1,700 per patient for recipients of leukocyte-reduced blood in 1998 compared with recipients of non-leukocyte-reduced blood in 1997 Mean costs increased $4,000 per patient in patients who did not receive transfusions in 1998 compared with 1997. Hospitalization costs decreased when leukocyte-reduced transfusions were implemented for patients undergoing cardiac surgery in our institution. Implementation of leukocyte reduction may be cost neutral or cost saving in at least some settings.  相似文献   
87.
Spoerke ED  Stupp SI 《Biomaterials》2005,26(25):5120-5129
Titanium has been a successful implant material owing to its excellent strength to weight ratio, toughness, and bioinert oxide surface. Significant progress has been made on the improvement of titanium's bioactivity by coating its oxide surface with calcium phosphates and bioactive molecules. Here, we report on the coating of titanium with a poly(L-lysine)-calcium phosphate hybrid material with a nanoscale texture. This hybrid coating was grown by first nucleating seed crystals of calcium phosphate, directly on the Ti surface and then exposing this surface to solutions containing Ca(2+), PO(4)(3-), and poly(L-lysine). The resultant hybrid coating was characterized by electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and elemental analysis. This material contained 14% by weight poly(L-lysine), and this organic component decreased greatly the dimensions of the surface features, thus enhancing surface area relative to the inorganic control. The highly textured hybrid material was more susceptible than the control to acidic and enzymatic degradation. The amino acid cysteine was covalently linked to the hybrid material, demonstrating the potential of this coating for further functionalization. These hybrid coatings may prove useful in enhancing the bioactivity of titanium.  相似文献   
88.
Severe bronchiectasis   总被引:6,自引:0,他引:6  
Bronchiectasis is primarily the result of airway injury and remodeling attributable to recurrent or chronic inflammation and infection. The underlying etiologies include autoimmune diseases, severe infections, genetic abnormalities, and acquired disorders. Recurrent airway inflammation and infection may also be the result of allergic or immunodeficiency states such as allergic bronchopulmonary mycoses or HIV/AIDS. Bronchiectasis should be included in the differentiation diagnosis of any patient with chronic respiratory complaints such as cough and sputum production. Early clinical manifestations may be subtle. Hallmarks of severe bronchiectasis include fetid breath, chronic cough, and sputum production. The associated chronic respiratory infections and airway sepsis are punctuated by episodes of acute exacerbation. Prompt recognition and treatment of bronchiectasis may allow for prevention of disease progression and irreversible loss of lung function. This review of severe non-cystic fibrosis bronchiectasis describes the current pathophysiology, clinical presentations, and management of bronchiectasis. We review how impaired airway clearance and the inability to resolve infection and inflammation creates a vicious cycle of recurrent injury. The common clinical features of bronchiectasis and findings are presented and illustrated by radiographic images. The common species and significance of various organisms often recovered from the distal airways including: tuberculous and environmental mycobacteria, aspergillus, and bacteria such as Pseudomonas aeruginosa will be covered. Management strategies including sputum surveillance, sputum clearance, antimicrobial therapy including antifungal and antimyobacterial agents as well as the evidence for the use of inhalational and anti-inflammatory therapies such as corticosteroids are also discussed. Recommendations for the work-up and therapy of complications including hemoptysis and respiratory failure are presented.  相似文献   
89.
90.
The concurrent and predictive validity of 2 different methods of Millon Clinical Multiaxial Inventory-III subtyping (protocol sorting, cluster analysis) was evaluated in 125 recently detoxified opioid-dependent outpatients in a 12-week randomized clinical trial. Participants received naltrexone and relapse prevention group counseling and were assigned to 1 of 3 intervention conditions: (a) no-incentive vouchers, (b) incentive vouchers alone, or (c) incentive vouchers plus relationship counseling. Affective disturbance was the most common Axis I protocol-sorted subtype (66%), antisocial-narcissistic was the most common Axis II subtype (46%), and cluster analysis suggested that a 2-cluster solution (high vs. low psychiatric severity) was optimal. Predictive validity analyses indicated less symptom improvement for the higher problem subtypes, and patient treatment matching analyses indicated that some subtypes had better outcomes in the no-incentive voucher conditions.  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