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   29548篇
  免费   2313篇
  国内免费   71篇
耳鼻咽喉   254篇
儿科学   823篇
妇产科学   810篇
基础医学   4378篇
口腔科学   444篇
临床医学   3477篇
内科学   6006篇
皮肤病学   537篇
神经病学   3060篇
特种医学   719篇
外国民族医学   4篇
外科学   3536篇
综合类   276篇
一般理论   24篇
预防医学   3075篇
眼科学   386篇
药学   1875篇
中国医学   35篇
肿瘤学   2213篇
  2023年   253篇
  2022年   456篇
  2021年   903篇
  2020年   564篇
  2019年   875篇
  2018年   941篇
  2017年   637篇
  2016年   668篇
  2015年   815篇
  2014年   1084篇
  2013年   1392篇
  2012年   2012篇
  2011年   1973篇
  2010年   1075篇
  2009年   966篇
  2008年   1590篇
  2007年   1492篇
  2006年   1408篇
  2005年   1277篇
  2004年   1187篇
  2003年   1040篇
  2002年   937篇
  2001年   608篇
  2000年   639篇
  1999年   512篇
  1998年   224篇
  1997年   195篇
  1996年   178篇
  1995年   148篇
  1994年   159篇
  1993年   134篇
  1992年   383篇
  1991年   352篇
  1990年   372篇
  1989年   335篇
  1988年   344篇
  1987年   315篇
  1986年   322篇
  1985年   288篇
  1984年   214篇
  1983年   176篇
  1979年   164篇
  1978年   163篇
  1977年   139篇
  1975年   156篇
  1974年   182篇
  1973年   136篇
  1972年   137篇
  1971年   139篇
  1970年   121篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
S Storm  M D Weiss 《Muscle & nerve》2003,27(5):631-635
Tourniquet paralysis is an uncommon complication of surgery, and self-inflicted tourniquet paralysis has never been documented to our knowledge. We report a patient with bilateral self-induced tourniquet paralysis of the lower extremities, whose symptoms were initially attributed to an acute demyelinating sensorimotor polyneuropathy based on clinical presentation and electrodiagnostic study. After investigations failed to reveal a cause, he was found to have placed tourniquets on his legs because of a rare obsession with limb amputation known as apotemnophilia. Significant spontaneous partial resolution of clinical symptoms was noted after 6 weeks. Electrophysiologic evidence of segmental demyelination of multiple motor nerves localized to the same region may help to distinguish this condition from other forms of acute demyelinating polyneuropathy.  相似文献   
62.
63.
The catechol-O-methyltransferase (COMT) Val158Met polymorphism modulates executive functions and working memory and recent neuroimaging studies implicate an association with emotional processing. We examined the relationship between the COMT Val158Met polymorphism and facial emotion recognition and differentiation in 100 healthy individuals. Compared to Met homozygosity, Val homozygosity was associated with better and faster recognition of negative facial expressions such as anger and sad. Our study provides evidence for a possible influence of the COMT polymorphism on emotion recognition abilities in healthy subjects. Additional research is needed to further define the neurocognitive phenotypes associated with COMT polymorphisms.  相似文献   
64.
The distinction between seminoma and embryonal carcinoma based on morphology alone can sometimes be problematic, requiring the use of immunohistochemistry to facilitate diagnosis. D2-40 is a monoclonal antibody that reacts with an oncofetal antigen expressed by fetal germ cells and testicular germ cell tumors. The diagnostic value of D2-40 immunohistochemistry in distinguishing seminoma from embryonal carcinoma has not been determined. D2-40 immunoreactivity was evaluated in a series of testicular germ cell tumors and compared with that of KIT (CD117) and CD30, to assess the relative utility of this marker in discriminating between seminoma and embryonal carcinoma. Forty testicular germ cell neoplasms were examined, which included 19 seminomas, three embryonal carcinomas, three teratomas, one yolk sac tumor, and 14 mixed germ cell tumors. The 14 cases of mixed germ cell tumors contained components of seminoma (n=7), embryonal carcinoma (n=11), teratoma (n=10), yolk sac tumor (n=2), and choriocarcinoma (n=1). All cases of pure seminoma and the seminomatous components of mixed germ cell tumors exhibited positive immunoreactivity for D2-40. Focal positivity for D2-40 was also observed in 29% of the embryonal carcinoma samples. D2-40 immunoreactivity in seminomas was characterized by diffuse membrane staining, whereas for embryonal carcinomas, staining was focal and distributed along the apical surfaces of the neoplastic cells. Immunohistochemical staining for KIT was observed in 92% of the seminoma samples and in none of the embryonal carcinomas. Conversely, CD30 expression was identified in 93% of the embryonal carcinoma samples and in none of the seminomas. Other germ cell components showed no immunoreactivity for D2-40, KIT, or CD30. KIT and CD30 are effective immunohistochemical markers in separating seminoma from embryonal carcinoma. Although a highly sensitive marker for seminomas, D2-40 positivity was also observed in a subset of embryonal carcinomas, thus limiting the utility of this antibody for discriminating between these two malignancies.  相似文献   
65.
We have previously described the isolation and initial characterization of 15 kDa protein isoforms (p15s) from rabbit polymorphonuclear leukocytes (PMN) that bind toEscherichia coli and modulate the antibacterial actions of other leukocyte proteins on this gram negative organism. We now report that the p15s differ in primary structure. The cloning and sequencing of two distinct p15 cDNAs from a rabbit bone marrow library reveal that two of the isoforms are closely similar in primary structure differing at only two amino acid positions. The p15 cDNAs encode putative signal sequences suggesting a granule-associated localization for these proteins. Analysis of the derived p15 primary structures reveals homology to two leukocyte proteins: CAP-18, an 18 kD lipopolysaccharide (LPS) binding protein from rabbit PMN and cathelin, an 11 kD cysteine protease inhibitor from porcine leukocytes. This structural similarity suggests the existence of a novel family of low molecular weight leukocyte proteins with potential roles in inflammation.  相似文献   
66.
Two tests, components of an Anxiety/Defense Test Battery, have been designed to measure risk assessment, inhibition of nondefensive behaviors, and movement arrest, all of which occur in the natural defense patterns of rats to threatening stimuli. In these tests, which used a nonpainful threat stimulus (a cat), ethanol (0.6 and 1.2 g/kg) increased two risk assessment behaviors on an initial test day, and produced a wider pattern of changes in all three patterns on a retest (no cat) day, 5 days later. The pattern of results obtained is compatible with a view that defensive behaviors occur in a fixed sequence with the decreasing intensity of threat an important factor in the transition from one defensive behavior to the next, and with ethanol at these doses producing a mild and relatively nonspecific anxiolytic effect. Comparison of male and female subjects on these tasks also suggested that females are more defensive than males, a finding which agrees with a variety of human anxiety studies but is at variance with previous rodent literature.  相似文献   
67.
A malignant fibrous histiocytoma of the sacrum complicating the course of radiation therapy for endometrial carcinoma is presented. Although the tumor fulfilled the clinical, radiologic, and histologic criteria for a postirradiation malignant fibrous histiocytoma of bone, it also expressed cytokeratin. That this immunoreactivity reflected keratin synthesis by the tumor and not an unusual pattern of cross-reactivity with another intermediate filament such as vimentin is strongly suggested by the reproducibility of the immunoreactivity utilizing both polyclonal and monoclonal antibodies and extinction of the immunoreactivity following absorption of the primary antiserum with keratin proteins. This is the first reported instance of keratin expression by a malignant fibrous histiocytoma; it indicates that sarcomas apart from synovial sarcoma and epithelioid sarcoma may sometimes express this protein.  相似文献   
68.
69.
Topotecan (SK&F 104864) is a novel antitumor agent whose mechanism of action is inhibition of the DNA unwinding protein topoisomerase I. An analog of camptothecin, topotecan was designed to be more water soluble in an effort to decrease the severe and sporadic toxicities experienced during phase I/II trials of the parent compound. In this phase I clinical and pharmacological trial, topotecan was given as a bolus intravenous (i.v.) infusion over 30 min every 21 days. A total of 42 patients entered the study, receiving doses ranging from 2.5 to 22.5 mg/m2. The maximum tolerated dose (MTD) of topotecan given in this schedule was 22.5 mg/m2. Myelosuppression, primarily neutropenia, was dose-limiting. The extent of prior therapy did not predict for more severe neutropenia. Non-hematologic toxicities were mild and included low-grade to moderate fever, nausea, vomiting, alopecia, diarrhea and skin rashes. There were no objective partial or complete responses, although there was a suggestion of antitumor activity in three patients. Topotecan undergoes pH-dependent hydrolysis of the lactone ring; only the closed, lactone form is active. The lactone form predominated during infusion, with hydrolysis occurring rapidly following the end of infusion. There were linear relationships between dose administered and peak plasma lactone concentrations as well as AUC lactone to AUC total. The lactone was rapidly cleared from plasma with a total body clearance of 25.7 (+/- 6.7) l/h/m2. The plasma lactone concentration declined rapidly with a harmonic mean terminal half-life of 3.4 (+/- 1.1)h. Lactone hydrolysis and renal excretion were the major routes of elimination.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
70.
The incidence of group A Streptococcus (GAS) invasive infections has been increasing worldwide, and there is no obvious explanation for this phenomenon. In 1993, a working group on severe GAS infections was established to define accurately what constitutes an invasive infection. Three types of infection are particularly feared: necrotizing fasciitis, myositis and a newly defined entity, named streptococcal toxic shock syndrome (STSS) because of a certain analogy with its staphylococcal counterpart. GAS produces many toxins responsible for its clinical manifestations. Some of them, labelled streptococcal pyrogenic exotoxins, have been characterized as superantigens. These proteins play a key role in initiating the immune response to GAS and are mostly responsible for the precipitous course of invasive infections. Death rates are high in streptococcal invasive infections, ranging from about 20% for necrotizing fasciitis to almost 100% for myositis. Therapy consists mainly of high doses of antibiotic combinations, aggressive surgery, and intravenous administration of immunoglobulins for STSS.  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