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   11433篇
  免费   668篇
  国内免费   49篇
耳鼻咽喉   169篇
儿科学   184篇
妇产科学   190篇
基础医学   1605篇
口腔科学   1445篇
临床医学   886篇
内科学   2184篇
皮肤病学   267篇
神经病学   862篇
特种医学   281篇
外科学   1064篇
综合类   41篇
一般理论   4篇
预防医学   1400篇
眼科学   190篇
药学   902篇
中国医学   129篇
肿瘤学   347篇
  2023年   104篇
  2022年   254篇
  2021年   431篇
  2020年   280篇
  2019年   394篇
  2018年   453篇
  2017年   311篇
  2016年   330篇
  2015年   388篇
  2014年   555篇
  2013年   653篇
  2012年   956篇
  2011年   972篇
  2010年   565篇
  2009年   415篇
  2008年   630篇
  2007年   639篇
  2006年   528篇
  2005年   485篇
  2004年   421篇
  2003年   345篇
  2002年   306篇
  2001年   235篇
  2000年   204篇
  1999年   159篇
  1998年   71篇
  1997年   49篇
  1996年   39篇
  1995年   31篇
  1994年   20篇
  1993年   29篇
  1992年   56篇
  1991年   91篇
  1990年   74篇
  1989年   76篇
  1988年   75篇
  1987年   65篇
  1986年   38篇
  1985年   47篇
  1984年   32篇
  1983年   23篇
  1982年   23篇
  1981年   23篇
  1980年   25篇
  1979年   27篇
  1978年   22篇
  1975年   19篇
  1974年   33篇
  1973年   17篇
  1971年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Two cases of double outlet right ventricle with restrictive ventricular septal defect are described. This is an uncommon presentation that causes left ventricular dysfunction because of left ventricular outflow tract obstruction. The presence of an intact atrial septum leads to severe pulmonary hypertension, which tends to aggravate the right ventricular output. In the presence of a normal left ventricle, the authors suggest the possibility of enlargement of the ventricular septal defect in order to perform a biventricular repair. The association of a supramitral valve ring in both cases, and the isolation of the left subclavian artery and an aortopulmonary fenestration in one of these cases, are also discussed. In addition we explore factors that cause restrictive ventricular septal defects as well as the mechanisms that may lead to spontaneous closure of ventricular septal defect in a double outlet right ventricle.  相似文献   
103.
Three cases of intravenous leiomyomatosis (IVL) of the uterus, a rare benign smooth-muscle tumor, are described. A preoperative diagnosis of IVL was not made in any of the patients, all of which presented with a pelvic mass with the presumptive diagnosis of leiomyoma. Surgical exploration confirmed the presence of uterine mass and two of the three cases showed extra-uterine extension into the ovarian or uterine veins. Histological examination demonstrated a fascicular pattern of bland spindle-shaped smooth-muscle cells, which extended to veins inside the myometrium or to extrauterine veins. This was confirmed by immunohistochemical stain for desmin and factor VIII. Despite their histological benignity, these lesions have a tendency to metastasize and are closely related to the conditions called “benign metastasizing leiomyoma” and “intracaval mass and cardiac extension”. The primary treatment of IVL is hysterectomy and excision of any extrauterine tumor, when technically feasible. Anti-estrogenic therapy has been suggested as potentially useful in controlling of unresectable tumor. According to the literature, the follow-up must be long and periodic postoperative ultrasonic or magnetic nuclear resonance imaging studies may be useful in detecting growth of residual intravascular tumor.  相似文献   
104.
In the mammalian CNS, glutamate and GABA are the principal neurotransmitters mediating excitatory and inhibitory synaptic events, respectively, and have been implicated in the neurobiology of seizures. Guanine-based purines, including the nucleoside guanosine and the nucleotide GMP, have been shown to antagonize glutamatergic activity at the receptor level and the other purine nucleoside adenosine is a well-known modulator of seizure threshold. In the present study we investigated the anticonvulsant effect of i. p. guanosine and GMP against seizures induced by the glutamate agonist quinolinic acid (QA) or the GABA(A) antagonist picrotoxin in mice. Animals were pretreated with an i.p. injection of saline, guanosine or GMP 30 min before either an i.c.v. injection of 4 microliter QA (36.8 nmol) or a subcutaneous injection of picrotoxin (3.2 mg/kg). All animals pretreated with vehicle followed by QA or picrotoxin presented seizures, which were completely prevented by the NMDA antagonist MK-801 and the GABA agonist phenobarbital, respectively. Guanosine and GMP dose-dependently protected against QA-induced seizures, up to 70 and 80% at 7.5 mg/kg, with ED(50)=2. 6+/-0.4 and 1.7+/-0.6 mg/kg, respectively. Conversely, neither guanosine, GMP nor MK-801 affected picrotoxin-induced seizures, indicating some degree of specificity towards the glutamatergic system. This study suggests anticonvulsant properties of i.p. guanosine and GMP, which may be related with antagonism of glutamate receptors.  相似文献   
105.
BACKGROUND: Despite continued improvement in medical therapy, empyema remains a challenging problem for the surgeon. Multiple treatment options are available; however, the optimal therapeutic management has not been elucidated. METHODS: A retrospective review was performed of all adult patients admitted to Denver Health Medical Center between January 1, 1993, and December 31, 1998, with the diagnosis of empyema. Data tabulated included patient demographics, presentation, chest computed tomography (CT) findings, treatment, and outcome. RESULTS: Empyema was diagnosed in 58 patients, 45 cases of which were multiloculated at the time of presentation. Empyema was secondary to pneumonia is 41 patients and posttraumatic in 15. In addition to antibiotic therapy, initial treatment included chest tube drainage alone (n = 6), chest tube drainage with primary operation (n = 19), and chest tube drainage with intrapleural fibrinolytic therapy (n = 33). In 15 patients (45%), fibrinolytic therapy failed. Initial chest CT revealed a pleural peel in 5 patients treated with fibrinolytics and all failed. Multiloculation, however, was not a factor in failure of fibrinolysis. Moreover, chest CT missed the presence of a pleural peel in 17 of 31 patients documented to have a significant peel at the time of thoracotomy. CONCLUSION: Multiple therapeutic options are available for the management of empyema. Multiloculation is not a contraindication to an initial trial of chest tube drainage or fibrinolytic therapy. In contrast, CT evidence of a pleural peel uniformly predicted failure of nonoperative treatment.  相似文献   
106.
OBJECTIVES: To study HIV-positive women and women at risk of becoming infected with HIV who attended HIV prevention education group sessions at a university hospital in Brazil and to compare the use of the female condom and the male condom by these two groups of women. METHODS: The study subjects were 165 women participating in HIV prevention education group sessions at the Medical School Hospital of Ribeir?o Preto of the University of S?o Paulo, in the city of Ribeir?o Preto, S?o Paulo, Brazil. Women could be enrolled in the study from August 2000 to June 2001, and the follow-up observation time period was from August 2000 to July 2001. Male condoms and female condoms were freely distributed to all the participants at the end of each educational session and also at the end of each follow-up visit that the participants made. Each woman took part in an initial interview and was asked to return monthly. At each follow-up visit an additional short interview was carried out in order to investigate use of the male condom and of the female condom. Variables that were examined for the study included age, education, ethnic group, marital or relationship status, number of children, the women's use of male condoms and female condoms, commercial sex (whether the women had ever had sex in exchange for money, gifts, or favors), and previous knowledge of the female condom. RESULTS: The 165 women studied fell into the following three categories: 132 of them (80.0%) were HIV-positive, 26 of them (15.8%) had a sexually transmitted disease (STD) other than HIV and did not have an HIV-positive partner, and 7 of them (4.2%) had an HIV-positive partner but did not have HIV or any other STD. The women ranged in age from 15 to 64 years, with a mean of 30.3 years. Of the women in the study, 69.7% of them were married or were cohabitating, and 90.9% of them had a sexual partner. Just over two-thirds of the women had seven years of formal schooling or less. Out of 163 women, a total of 31 of them (19.0%) had never used the male condom with a partner, and 49 of the 163 (30.1%) had not used a male condom at the time of the last sexual intercourse. Out of the 165 women, 74 of them (44.8%) returned for at least one follow-up visit. Of these 74 women, 58 of them (78.3%) reported using the female condom between the initial interview and the first follow-up visit. The majority of the 74 women who returned for a visit liked using the female condom, and the women reported that their partners also generally accepted the female condom. In comparison to women at risk of HIV, HIV-positive women were more likely to have used the male condom with a partner before the initial interview. Women who continued returning over a longer follow-up period were more likely to have used the female condom at the time of the last sexual intercourse. No association was found between female condom use at the time of last sexual intercourse and the woman's HIV infection status. CONCLUSIONS: In comparison to the women at risk of HIV, the HIV-positive women in our study were more likely to use male condoms with their partners, to return for follow-up visits, and to have a longer follow-up period. The acceptance of the female condom among the HIV-positive women in this study, as reported at their first follow-up visit, appears to be similar to the acceptance of the female condom among women in general in Brazil.  相似文献   
107.
BACKGROUND: Gut ischemia followed by reperfusion (I/R) is implicated as a prime initiating event in the mechanism of multiple organ failure after trauma and hemorrhagic shock. Several lines of evidence indicate that macrophages are involved in this prime event. Our purpose was to evaluate hydrogen peroxide (H2O2) and tumor necrosis factor (TNF) production and phagocytosis by lung macrophages in a gut I/R model of multiple organ failure in rats. METHODS: In the experimental group (I/R), Wistar rats (n = 35) were anesthetized and subjected to a median laparotomy, and the superior mesenteric artery was clamped for 45 minutes followed by 60 minutes of reperfusion. In the control group (LAP) (n = 37), animals underwent sham laparotomy. After the period of reperfusion, bronchoalveolar lavage (BAL) was performed and the resulting BAL cells were assayed for H2O2 production using the horseradish peroxidase-mediated red phenol oxidation method. TNF release was determined using the L929 cells bioassay. Zymosan phagocytosis by BAL macrophages was quantitated using phase microscopy. RESULTS: H2O2 release in BAL cells of I/R rats (19.90 +/- 7.98 nmol/L/2 x 10(5) cells) is statistically higher than in the LAP group (10.92 +/- 5.01 nmol/L per 2 x 10(5) cells) (p = 0.0155), and the TNF production by BAL cells of the I/R group (38.09 +/- 20.79 units per 10(6) cells) was significantly higher than that of LAP rats (17.16 +/- 13.35 units per 10(6) cells) (p = 0.0281). Phagocytic activity of BAL mac. Macrophages of I/R rats was not statistically different from LAP animals. CONCLUSION: These results suggest that BAL macrophage play a role in the mechanism of acute lung injury after trauma and hemorrhagic shock.  相似文献   
108.
The venom of the Neotropical social wasp Protopolybia exigua(Saussure) was fractionated by RP-HPLC resulting in the elution of 20 fractions. The homogeneity of the preparations were checked out by using ESI-MS analysis and the fractions 15, 17 and 19 (eluted at the most hydrophobic conditions) were enough pure to be sequenced by Edman degradation chemistry, resulting in the following sequences: Protopolybia MPI I-N-W-L-K-L-G-K-K-V-S-A-I-L-NH2 Protopolybia-MP II I-N-W-K-A-I-I-E-A-A-K-Q-A-L-NH2 Protopolybia-MP III I-N-W-L-K-L-G-K-A-V-I-D-A-L-NH2 All the peptides were manually synthesized on-solid phase and functionally characterized. Protopolybia-MP I is a hemolytic mastoparan, probably acting on mast cells by assembling in plasma membrane, resulting in pore formation; meanwhile, the peptides Protopolybia-MP II and -MP III were characterized as a non-hemolytic mast cell degranulator toxins, which apparently act by virtue of their binding to G-protein receptor, activating the mast cell degranulation.  相似文献   
109.
BACKGROUND: There is not univocal concordance for using high-dose sequential therapy (HDS) as first-line treatment for aggressive non-Hodgkin's lymphoma (NHL). We designed this study to evaluate the usefulness of HDS followed by high-dose therapy (HDT) with autologous stem cell transplantation as front-line treatment in different subsets of aggressive NHL. PATIENTS AND METHODS: Among 223 patients aged 15-60 years with aggressive, advanced stage NHL, 106 patients were randomized to VACOP-B (etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone, bleomycin) for 12 weeks (plus HDS/HDT in case of persistent disease) (arm A), and 117 patients to VACOP-B for 8 weeks plus upfront HDS/HDT (arm B). RESULTS: According to the intention-to-treat analysis, the complete response rate was 75% for arm A and 72.6% for arm B. With a median follow-up of 62 months there was no difference in 7-year probability of survival (60% and 57.8%; P = 0.5), disease-free survival (DFS) (62% and 71%; P = 0.2) and progression-free survival (PFS) (44.9% and 40.9%; P = 0.7) between the two arms. Subgroup analyses confirmed that the best results in terms of survival, DFS and PFS were achieved by patients with large B-cell NHL without bone marrow (BM) involvement, independently of the treatment arm. Results were poorer in other categories of patients and poorest in patients with BM involvement. CONCLUSIONS: Aggressive NHL patients do not benefit from upfront HDS/HDT.  相似文献   
110.
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