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   8452篇
  免费   429篇
  国内免费   25篇
耳鼻咽喉   74篇
儿科学   167篇
妇产科学   99篇
基础医学   966篇
口腔科学   232篇
临床医学   571篇
内科学   2246篇
皮肤病学   138篇
神经病学   464篇
特种医学   218篇
外科学   1536篇
综合类   34篇
预防医学   206篇
眼科学   199篇
药学   679篇
中国医学   33篇
肿瘤学   1044篇
  2023年   34篇
  2022年   66篇
  2021年   133篇
  2020年   66篇
  2019年   102篇
  2018年   146篇
  2017年   96篇
  2016年   154篇
  2015年   155篇
  2014年   192篇
  2013年   262篇
  2012年   402篇
  2011年   367篇
  2010年   217篇
  2009年   197篇
  2008年   367篇
  2007年   395篇
  2006年   375篇
  2005年   406篇
  2004年   390篇
  2003年   379篇
  2002年   395篇
  2001年   419篇
  2000年   397篇
  1999年   345篇
  1998年   99篇
  1997年   90篇
  1996年   72篇
  1995年   71篇
  1994年   68篇
  1993年   62篇
  1992年   204篇
  1991年   179篇
  1990年   166篇
  1989年   170篇
  1988年   140篇
  1987年   150篇
  1986年   120篇
  1985年   132篇
  1984年   87篇
  1983年   74篇
  1979年   60篇
  1978年   34篇
  1977年   31篇
  1975年   35篇
  1974年   36篇
  1973年   33篇
  1972年   40篇
  1971年   45篇
  1969年   37篇
排序方式: 共有8906条查询结果,搜索用时 15 毫秒
21.
The cerebellar Purkinje cells in the hemizygote of the macular mutant mouse contain numerous abnormal mitochondria which show a marked decrease in cytochrome c oxidase activity. Using histochemical methods we studied the activity of other mitochondrial enzymes, such as NADH diaphorase and succinic dehydrogenase, in the cerebellar cortex of this mutant mouse. Such activities were markedly increased in the Purkinje cells, especially in the soma and stem dendrite, from 10 days after birth in the hemizygote as compared with findings in normal littermates. These results were considered to be due to an increased number of abnormal mitochondria.Supported by the Research Grants nos. 2A-5-03 and 3B-1-04 for Nervous and Mental Disorders from the Ministry of Health and Welfare, and by Grant no. 04670492 of the Ministry of Education of Japanese Government  相似文献   
22.
SPECT of the skull was performed on twelve patients with histologically proven nasopharyngeal carcinoma using newly developed three detectors SPECT system (Toshiba GCA 9300A) mounted with fan-beam collimators, for the purpose of early detection of skull base involvement of the disease. This SPECT system has extremely improved resolution with FWHM of 8 mm in the center, and it provides clear tomographic images of the skull which has anatomically complex structure. SPECT image was taken 3 hours after injection of 740 MBq (20 mCi) of 99mTc-MDP following whole body skeletal survey. In twelve patients with confirmed nasopharyngeal carcinoma, 8 patients showed positive findings on SPECT. Three of SPECT positive patients also showed destructive findings on CT. Other five positive patients did not show destructive findings on CT at their initial examinations, but in three of them CT findings turned to positive later. SPECT was superior to CT in early detection of skull base involvement. We believe that SPECT of the skull is a diagnostic tool for early detection of skull base involvement of nasopharyngeal carcinoma.  相似文献   
23.
Sixty-nine strains of Vibrio cholerae O1 isolated at different times were analysed to investigate if there were any differences among the O1 strains isolated before, during and after the advent of the O139 serogroup. Of the 69 O1 strains examined, 68 belonged to the Ogawa serotype while one belonged to the Inaba serotype. With the exception of one strain all other strains of V. cholerae O1 belonged to the eltor biotype. A single O1 strain isolated before the emergence of the O139 serogroup could not be classified as either eltor or classical biotype because it was resistant to both classical and eltor specific bacteriophages. Marked variations in the susceptibility to antibiotics of V. cholerae O1 isolated during the different periods were observed. In addition, strains of V. cholerae isolated after the epidemic of serogroup O139 in Calcutta showed an expanding R-type with resistance to a variety of drugs as compared to the O1 strains isolated before the advent of the O139 serogroup. From this study, it is clear that there is a substantial mobility in genetic elements of V. cholerae O1 which necessitates a continuous monitoring to keep abreast of the changing traits of the etiologic agent of cholera.  相似文献   
24.
25.
Prostaglandin E1 (PGE1) has several potential therapeutic effects, including cytoprotection, vasodilation, and inhibition of platelet aggregation. This study investigates the protective action of PGE1 against hepatic ischemia/reperfusion injury in vivo using a complementary DNA microarray. PGE1 or saline was continuously administered intravenously to mice in which the left lobe of the liver was made ischemic for 30 minutes and then reperfused. Livers were harvested 0, 10, and 30 minutes postreperfusion. Messenger RNA was extracted, and the samples were labeled with two different fluorescent dyes and hybridized to the RIKEN set of 18,816 full-length enriched mouse complementary DNA microarrays. Serum alanine aminotransferase and aspartate aminotransferase levels at 180 minutes postreperfusion were significantly lower in the PGE1-treated group than in the saline-treated group. The cDNA microarray analysis revealed that the genes encoding heat-shock protein (HSP) 70, glucose-regulated protein 78, HSP86, and glutathione S-transferase were upregulated at the end of the ischemic period (0 minutes postreperfusion) in the PGE1 group. Our results suggested that PGE1 induces HSPs immediately after ischemia reperfusion. HSPs might therefore play an important role in the protective effects of PGE1 against ischemia/reperfusion injury of the liver.  相似文献   
26.
Thirty-five patients with T2–T4 invasive bladder cancer were treated with combined cisplatin and radiation therapy. In 18 patients radical cystectomy was performed after the combined therapy. In the other 17 patients radical cystectomy could not be performed for various reasons. Pathological examination of the cystectomy specimens showed down-staging in 66.7% and no residual tumour in 33.3%. These results suggest a synergistic action of cisplatin and radiation. Side effects were not severe and were well tolerated. This combined therapy of cisplatin and radiation is very effective for invasive bladder cancer.  相似文献   
27.
It has been known that clarithromycin (TE-031, A-56268), a new macrolide antibiotic (ML), achieves higher concentrations in blood, is better excreted into urine and is better distributed into various tissues than conventional MLs. We investigated the pharmacokinetics of TE-031 in children upon oral administration of the drug in the following method. TE-031 granular preparation with a potency of 100 mg/g was given to 6 boys (5 years 4 months-14 years 0 month) with dose levels of 5 mg/kg and 10 mg/kg for each 3 boys. A tablet preparation with each tablet containing 50 mg of TE-031 was administered to 4 boys and 2 girls (8 years 5 months-11 years 6 months) with dose level of 2 tablets (i.e., 100 mg) and 3 tablets (i.e., 150 mg) for each 3 children. All administrations were done at 30 minutes before meal. Then, to conduct a cross-over test, the granule preparation was given orally to the 3 children mentioned above who was given 2 tablets and the 1 of 3 cases that were given 3 tablets at the same dose levels (100 mg and 150 mg) respectively. A bioassay was used to determine concentrations in blood of active antibiotic compounds and an high performance liquid chromatography (HPLC) was used to determine unchanged TE-031 and its main metabolite, M-5. Urinary concentrations of active antibiotic compounds were also determined by the bioassay and the HPLC was used to determine concentrations and proportions of unchanged TE-031 and its metabolites, M-1, M-4, M-5, M-6 and M-7 to figure out the urinary recovery rate in the first 6 hours. The results of these experiments are summarized as follows. 1. As was mentioned above, TE-031 was administered orally to 2 groups of children at dose levels of 5 mg/kg and 10 mg/kg, respectively. Mean serum levels of total active antibiotic compounds reached their maximum in 1 and 2 hours for the 5 mg/kg and the 10 mg/kg dosage groups, respectively, at 1.28 and 3.62 micrograms/ml, respectively. Mean half lives of serum concentrations in the 2 groups were quite similar, with values of at 2.1 and 2.0 hours, respectively. Mean serum concentrations of unchanged TE-031 determined by the HPLC method reached their peaks in 1 hour after administration in either of the 5 and 10 mg/kg dosage groups at peak levels of 0.65 micrograms/ml and 2.67 micrograms/ml, respectively. Thus, dose-response relationships were observed with TE-031 and M-5.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
28.
To evaluate pharmacokinetics of amikacin (AMK), one of the aminoglycoside antibiotics, children with ages from 2 days to 11 years were treated with various doses by various administration routes, and both plasma and urinary levels of AMK were determined. The following is a summary of the results obtained: 1. Of 6 children, three were treated with 2.0 mg/kg of AMK by a 30-minute intravenous drip infusion, and the other 3 with 4.0 mg/kg by a 60-minute. Peaks of average plasma levels were observed at the ends of the infusions in both cases, and their levels were 9.23 and 13.67 micrograms/ml, respectively, showing a dose-dependency. Both half-lives and areas under plasma concentration-time curves (AUCs) were similar to those of adults. However, the volume of distribution (Vd) showed a lower value than that of adults. Peaks of average urine levels were 149.3 micrograms/ml with 2.0 mg/kg in 0-2 hours after the start of the infusion and 223.3 micrograms/ml with 4.0 mg/kg in 2-4 hours. Average urinary recovery rates within 6 hours after the start of the infusion were 95.4% with 2.0 mg/kg and 85.7% with 4.0 mg/kg. These recoveries were equal to or higher than that of adults. 2. When 3.0, 4.0 and 6.0 mg/kg of AMK were administered to 3 groups of mature or premature babies by intramuscular injection, average peak levels of AMK in plasma were 6.26, 8.61 and 12.60 micrograms/ml, respectively, at 30 minutes after the injection, showing dose-dependency. In these groups, the younger the day age after birth was, the longer the half-life became. The AUCs were larger as the half-life became longer. The Vd was larger than that in the intravenous drip infusion group, but, any particular was not observed. Average peak levels of AMK in urine were 78.83 micrograms/ml at 4-6 hours with a dose level of 3.0 mg/kg, 99.17 micrograms/ml at 2-4 hours with 4.0 mg/kg and 139.20 micrograms/ml at 0-2 hours with 6.0 mg/kg. Average urinary recovery rates within 6 hours were 36.57% with 3.0 mg/kg, 34.67% with 4.0 mg/kg and 43.77% with 6.0 mg/kg. These recovery rates were markedly lower than those observed in adults and children. One of the causes of this low recovery is that mature and premature babies have immature renal functions. 3. When 3.0 mg/kg of AMK was administered to three premature babies by a 30-minute intravenous drip infusion, the average peak plasma levels was 7.61 micrograms/ml at the end of the drip infusion.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
29.
Treatment strategies for hepatic metastasis from colorectal cancer   总被引:3,自引:0,他引:3  
Hepatic micrometastases of the parenchyma adjacent to a macroscopic lesion were detected in 17 of 31 resected liver metastases. Fifty-nine micrometastatic lesions were detected in total; 26 lesions were situated in the portal vein (PV), 22 in the central vein (CV), 5 in the bile duct (BD), and 6 in the sinusoid (SS). A histological study confirmed the direct invasion of the macrometastatic cancer cells into the adjacent PV, CV, BD, and SS. According to the tumor doubling time, the mean diameter of the macrometastases in 19 remnant livers was calculated to have been 0.57±0.87 cm at the time of the primary resection. The calculated diameter of 3 of these 19 macrometastases was found to be less than 0.01 cm, the minimum implantable size, indicating that the cancer recurrence in these specimens may have developed from macroscopic metastatic lesions as a satellite, and not from the primary tumor. In 13 patients who received doses of 5250 mg or more of 5 fluorouracil (FU) via the hepatic artery, the cumulative disease-free rate 2 years postoperatively was 100%; this value was 47.6% in 11 patients who received less than 5250 mg of 5 FU via the hepatic artery, and 0% in 39 patients who received no chemotherapy (P<0.005). These results suggest that anatomical hepatic resection for satellite lesions, combined with prophylactic hepatic arterial chemotherapy for micrometastases, decreases the recurrence rate of hepatic metastases in the remnant liver.  相似文献   
30.
Graft-versus-host disease (GVHD) has been evaluated in partially inbred miniature swine in order to study this complication of allogeneic bone marrow transplantation (BMT) in a major histocompatibility complex (MHC) genetically defined large animal model. Bone marrow from MHC homozygous ("parental") swine was injected into irradiated (900 rads total-body irradiation) MHC heterozygous ("F1") swine that shared one haplotype with the donor. All 18 animals successfully engrafted with donor bone marrow, and 17 of these developed skin rash of varying intensity depending on the extent of T cell depletion of infused marrow. Of 18 animals, 8 received undepleted bone marrow from exsanguinated donors and 2 also received additional peripheral blood lymphocytes (PBL) as a source of mature T cells. All 8 showed a moderate-to-severe rash, and the 2 pigs that received additional donor PBL developed the most severe rash. The cutaneous eruption seen in this model clinically, histologically, and immunologically resembled human GVHD. Two protocols of T cell depletion of donor bone marrow by antiporcine T cell monoclonal antibodies plus complement were tested for their effect on development of GVHD. The combination of two monoclonal antibodies, 74-12-4 (PT4) and 76-2-11 (PT8), had a marginal effect on the subsequent development of cutaneous manifestations of GVHD. However, treatment of the donor marrow by a combination of three monoclonal antibodies--PT4, PT8, and MSA4 (PT11)--effectively decreased the severity of the GVHD skin rash. These results indicate that (1) the GVHD associated with allogeneic bone marrow transplantation in swine is dependent on T cells in the marrow; (2) effective T cell depletion of donor marrow by monoclonal antibodies and complement does not prevent engraftment; and (3) this swine GVHD model, which allows study with F1 and homozygous parental combinations in an MHC genetically defined large animal, is particularly useful for the understanding of GVHD pathogenesis, prevention, and treatment.  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