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   1879篇
  免费   94篇
  国内免费   14篇
耳鼻咽喉   17篇
儿科学   41篇
妇产科学   9篇
基础医学   214篇
口腔科学   11篇
临床医学   141篇
内科学   533篇
皮肤病学   4篇
神经病学   102篇
特种医学   60篇
外科学   333篇
综合类   4篇
预防医学   47篇
眼科学   23篇
药学   167篇
中国医学   3篇
肿瘤学   278篇
  2023年   5篇
  2022年   20篇
  2021年   29篇
  2020年   27篇
  2019年   23篇
  2018年   27篇
  2017年   22篇
  2016年   24篇
  2015年   24篇
  2014年   49篇
  2013年   62篇
  2012年   93篇
  2011年   97篇
  2010年   58篇
  2009年   38篇
  2008年   92篇
  2007年   122篇
  2006年   114篇
  2005年   102篇
  2004年   115篇
  2003年   120篇
  2002年   165篇
  2001年   27篇
  2000年   27篇
  1999年   36篇
  1998年   45篇
  1997年   45篇
  1996年   43篇
  1995年   37篇
  1994年   45篇
  1993年   33篇
  1992年   25篇
  1991年   14篇
  1990年   16篇
  1989年   16篇
  1988年   8篇
  1987年   14篇
  1986年   13篇
  1985年   12篇
  1984年   12篇
  1983年   12篇
  1982年   8篇
  1981年   14篇
  1980年   7篇
  1979年   8篇
  1978年   8篇
  1975年   6篇
  1973年   3篇
  1972年   5篇
  1967年   3篇
排序方式: 共有1987条查询结果,搜索用时 15 毫秒
71.
Solitary Fibrous Tumor in the Retroperitoneal Space: Report of a Case   总被引:2,自引:0,他引:2  
Solitary fibrous tumors (SFTs) are spindle-cell neoplasms originally described in the pleura. It is now known that these tumors can develop in many sites. This report describes the case of a well-circumscribed tumor located around the superior mesenteric artery (SMA), which was initially thought to be either a superior SMA aneurysm, a lymphoma, or a neurogenic tumor. Histological examination demonstrated the tumor to be composed of a cellular proliferation of ovoid to spindle cells with a fine collagenous matrix in the short fascicles. Immunohistochemical staining was strongly positive for CD34 and negative for factor VIII, cytokeratin, desmin, and muscle-specific actin (HHF-35). These findings suggested a diagnosis of SFT in the retroperitoneal space. To our knowledge, this is the first report of an SFT located around the SMA. Based on the above findings, it is important to include SFT in the differential diagnosis of retroperitoneal tumors located around the SMA. Received: August 13, 2001 / Accepted: March 5, 2002 Reprint requests to: M. Kume  相似文献   
72.
Although the antigen expression patterns of childhood acute lymphoblastic leukemia (ALL) are well known, little attention has been given to standardizing the diagnostic and classification criteria. We retrospectively analyzed the flow cytometric data from a large study of antigen expression in 1,774 children with newly diagnosed ALL in JPLSG. T- and B-lineage ALL accounted for 13 and 87% of childhood ALL cases, respectively. Cytoplasmic CD3 and CD7 antigens were positive in all T-ALL cases. More than 80% of T-ALL cases expressed CD2, CD5 and TdT. In B-lineage ALL, the frequencies of early pre-B, pre-B, transitional pre-B and B-ALL were 81, 15.5, 0.6 and 2.9%, respectively. More than 90% of early pre-B ALL cases expressed CD19, CD79a, CD22, CD10 and TdT. CD34 was expressed in three-fourths of early pre-B ALL cases. The frequencies of TdT and CD34 expression were lower in pre-B ALL than in early pre-B ALL. B-ALL showed less frequent expression of CD22, CD10, CD34 and TdT than other B-lineage ALL cases. Expression of CD13 and CD33, aberrant myeloid antigens, was significantly more frequently associated with B-lineage ALL than with T-ALL. Based on this retrospective study of antigen expression in 1,774 de novo childhood ALL cases in JPLSG, we propose standardized clinical guidelines for the immunophenotypic criteria for diagnosis and classification of pediatric ALL.  相似文献   
73.
The bacterial strains isolated from 565 patients diagnosed as having urinary tract infections (UTIs) in 14 institutions in Japan were collected between August 2003 and July 2004. The susceptibilities of them to many kinds of antimicrobial agents were investigated. Of them, 701 strains were estimated as prophlogistic bacteria and used for the investigation. The strains consisted of 258 Gram-positive bacterial strains (36.8%) and 443 Gram-negative bacterial strains (63.2%). Against Staphylococcus aureus, vancomycin (VCM) showed the strongest activity and prevented the growth of all strains with 2 microg/mL. Against Streptococcus agalactiae, ampicillin (ABPC), cefozopran (CZOP), imipenem (IPM), and clarithromycin (CAM) showed a strong activity and the MIC90 was 0.125 microg/mL or less. Against Enterococcus faecalis, VCM, ABPC, and IPM showed a strong antibacterial activity. The antibacterial activity of cephems to Escherichia coli was generally good, and especially CZOP and cefpirome (CPR) showed the strongest activity (MIC90: < or = 0.125 microg/mL). Quinolone resistant E. coli [MIC of ciprofloxacin (CPFX): > or =4 microg/mL] was detected at frequency of 15.7%, which was higher than that in the last year. Against Klebsiella pneumoniae, meropenem (MEPM) showed the strongest activity and next, the antibacterial activity of CRMN and CZOP was good. The antibacterial activity of the other cephems, however, significantly decreased, compared with that evaluated in last year. Against Serratia marcescens, MEPM had the strongest antibacterial activity. Against Proteus mirabilis, MEPM and CRMN showed the strongest activity and prevented the growth of all strains with 0.125 microg/mL or less. Nest, cefmenoxime (CMX), ceftazidime (CAZ), cefixime (CFIX), cefpodoxime (CPDX), CPR, CZOP, and cefditoren (CDTR) showed a strong activity. The antibacterial activity of the drugs to Pseudomonas aeruginosa was generally low, and MIC90 of all the drugs was ranged from 32 to < or = 256 microg/mL except IPM and amikacin (AMK) having 16 microg/mL. The antibacterial activity of CZOP was relatively good (MIC50: 2 microg/mL).  相似文献   
74.
75.
A disintegrin and metalloproteinase 3 (ADAM3) is a sperm membrane protein critical for both sperm migration from the uterus into the oviduct and sperm primary binding to the zona pellucida (ZP). Here we show that the testis-specific protein disulfide isomerase homolog (PDILT) cooperates with the testis-specific calreticulin-like chaperone, calsperin (CALR3), in the endoplasmic reticulum and plays an indispensable role in the disulfide-bond formation and folding of ADAM3. Pdilt(-/-) mice were male infertile because ADAM3 could not be folded properly and transported to the sperm surface without the PDILT/CALR3 complex. Peculiarly we find that not only Pdilt(-/-), but also Adam3(-/-), spermatozoa effectively fertilize eggs when the eggs are surrounded in cumulus oophorus. These findings reveal that ADAM3 requires testis-specific private chaperones to be folded properly and that the principle role of ADAM3 is for sperm migration into the oviduct but not for the fertilization event. Moreover, the importance of primary sperm ZP binding, which has been thought to be a critical step in mammalian fertilization, should be reconsidered.  相似文献   
76.
Summary The carcinogenicity of 1,2-dimethylhydrazine dihydrochloride (DMH) by oral, intragastric and subcutaneous administration was examined in 339 BALB/c mice. Subcutaneous injection of DMH induced intestinal tumors in the lower colon of all mice. After oral administration it induced a high incidence of vascular tumors in the liver and soft tissues, but colon tumors were found in only 2 mice when given at a high dosage. On intragastric administration, it induced a fairly high incidence both of colon and vascular tumors. The sites and incidences of vascular tumors and squamous cell carcinomas of the perianal glands were also described.This work was supported in part by a Grant-in Aid for Cancer Research from the Ministry of Education, Japan.  相似文献   
77.
78.
Two cases of drug-eluting stent restenosis after percutaneous coronary intervention in the left main coronary artery and its bifurcation are presented. An off-pump coronary artery bypass grafting following in-stent restenosis was performed. Drug-eluting stents have shown a reduced frequency of in-stent restenosis and a good safety profile compared with bare metal stents. However, intervention with drug-eluting stents for left main coronary artery disease should be undertaken with care. It is also important to note that preoperative anti-platelet drug administration can increase the risk of major bleeding during and after emergent surgery.  相似文献   
79.
Dermatomyositis (DM) and polymyositis (PM) are often refractory to conventional therapy with corticosteroids sometimes combined with immune-suppressing agents and can lead to severe disability if these treatments are unsuccessful. In this prospective, open, non-randomized study, we examined the efficacy of tacrolimus (FK506), an immunosuppressant, in nine patients with DM (n?=?5) or PM (n?=?4) who did not respond to previous therapy. Outcomes included compound muscle strength, ambulatory status, and serum creatine kinase activity measured at intervals after starting tacrolimus. At 6?months after the introduction of tacrolimus, all five patients with DM and three patients with PM showed clinical improvements. Patients with a disease duration of <4?years and those with trough level of tacrolimus >5?ng/ml tended to have better outcomes than those with longer disease duration or lower trough levels. There were no side effects other than moderate hypertension and aggravation of diabetes mellitus. Tacrolimus was beneficial in the majority of patients with PM or DM refractory to corticosteroid therapy. It was also effective in four patients who were previously treated with other immunosuppressants or intravenous immunoglobulin combined with corticosteroids. These results warrant further studies as to the efficacy of tacrolimus compared to other immunosuppressing agents.  相似文献   
80.
CTX-M-19 is a recently identified ceftazidime-hydrolyzing extended-spectrum beta-lactamase, which differs from the majority of CTX-M-type beta-lactamases that preferentially hydrolyze cefotaxime but not ceftazidime. To elucidate the mechanism of ceftazidime hydrolysis by CTX-M-19, the beta-lactam MICs of a CTX-M-19 producer, and the kinetic parameters of the enzyme were confirmed. We reconfirmed here that CTX-M-19 is also stable at a high enzyme concentration in the presence of bovine serum albumin (20 micro g/ml). Under this condition, we obtained more accurate kinetic parameters and determined that cefotaxime (k(cat)/K(m), 1.47 x 10(6) s(-1) M(-1)), cefoxitin (k(cat)/K(m), 62.2 s(-1) M(-1)), and aztreonam (k(cat)/K(m), 1.34 x 10(3) s(-1) M(-1)) are good substrates and that imipenem (k(+2)/K, 1.20 x 10(2) s(-1) M(-1)) is a poor substrate. However, CTX-M-18 and CTX-M-19 exhibited too high a K(m) value (2.7 to 5.6 mM) against ceftazidime to obtain their catalytic activity (k(cat)). Comparison of the MICs with the catalytic efficiency (k(cat)/K(m)) of these enzymes showed that some beta-lactams, including cefotaxime, ceftazidime, and aztreonam showed a similar correlation. Using the previously reported crystal structure of the Toho-1 beta-lactamase, which belongs to the CTX-M-type beta-lactamase group, we have suggested characteristic interactions between the enzymes and the beta-lactams ceftazidime, cefotaxime, and aztreonam by molecular modeling. Aminothiazole-bearing beta-lactams require a displacement of the aminothiazole moiety due to a severe steric interaction with the hydroxyl group of Ser167 in CTX-M-19, and the displacement affects the interaction between Ser130 and the acidic group such as carboxylate and sulfonate of beta-lactams.  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