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   61059篇
  免费   2915篇
  国内免费   345篇
耳鼻咽喉   803篇
儿科学   1199篇
妇产科学   896篇
基础医学   7902篇
口腔科学   1549篇
临床医学   4133篇
内科学   15196篇
皮肤病学   863篇
神经病学   4708篇
特种医学   2228篇
外科学   10680篇
综合类   245篇
一般理论   2篇
预防医学   1936篇
眼科学   922篇
药学   4710篇
中国医学   115篇
肿瘤学   6232篇
  2023年   309篇
  2022年   537篇
  2021年   1220篇
  2020年   610篇
  2019年   907篇
  2018年   1112篇
  2017年   867篇
  2016年   1074篇
  2015年   1142篇
  2014年   1504篇
  2013年   1875篇
  2012年   3036篇
  2011年   3281篇
  2010年   1877篇
  2009年   1610篇
  2008年   2973篇
  2007年   3255篇
  2006年   3221篇
  2005年   3195篇
  2004年   3103篇
  2003年   3084篇
  2002年   3021篇
  2001年   1824篇
  2000年   1921篇
  1999年   1703篇
  1998年   773篇
  1997年   632篇
  1996年   597篇
  1995年   485篇
  1994年   455篇
  1993年   405篇
  1992年   1216篇
  1991年   1018篇
  1990年   982篇
  1989年   1009篇
  1988年   898篇
  1987年   867篇
  1986年   816篇
  1985年   800篇
  1984年   562篇
  1983年   445篇
  1982年   251篇
  1979年   491篇
  1978年   289篇
  1977年   265篇
  1975年   217篇
  1974年   231篇
  1971年   233篇
  1969年   232篇
  1968年   220篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Regional effects of craniotomy on cerebral circulation and metabolism, such as regional cerebral blood flow (rCBF), regional cerebral oxygen consumption (rCMRO2), regional oxygen extraction fraction (rOEF), and regional cerebral blood volume (rCBV) were examined by a PET (positron emission tomography) study concerning surgery that was performed on unruptured aneurysm patients. Eight patients with intracranial un-ruptured aneurysms were studied pre- and post-operatively by the 15O labelled-gas steady-state method, using HEADTOME-III. All patients underwent aneurysmal surgery performed by the transsylvian approach. There was a significant increase in the mean OEF values taken from the whole-brains of 8 patients, but there was not a significant change in CBF, CMRO2 or CBV. The increase in OEF was caused by decrease of O2 content, which was caused by post-operative decrease in the Hb value. So, this OEF increase was not the direct effect of craniotomy. In 2 patients, the rCBF and rCMRO2, in the fronto-temporal region (where craniotomy was performed) increased post-operatively. This regional effect suggests transient reactive hyperemia following compressive ischemia during the operative procedure, and metabolic demands for recovery of brain function. In 2 other patients, who had relatively low rCBFs during the pre-operative study, rCBF and rCMRO2 in the bi-frontal region had decreased more at the post-operative study. This change appears to have been caused by removal of cerebrospinal fluid and depression of the frontal lobe. From this study, it becomes evident that the regional effect of craniotomy on cerebral circulation and metabolism is not so great, when adequate microsurgical techniques are used.  相似文献   
32.
To investigate the role of cell-mediated immunity (CMI) in glomerulonephritis (GN), we identified the infiltrating immune cells both within the glomerulus and in the interstitium. Frozen sections from 103 patients with various forms of GN: 10 with minor glomerular abnormality (MGA) as control, 10 with minimal change nephrotic syndrome (MCNS), 10 with membranous nephropathy (MN), 9 with focal glomerulosclerosis (FGS), 30 with IgA nephropathy (IgAN), 22 with acute post streptococcal glomerulonephritis (APSGN), and 2 with rapidly progressive glomerulonephritis (RPGN) were examined using monoclonal antibodies (MoAb) by indirect immunoalkaline-phosphatase labelling. In most glomerulonephritis, monocyte/M phi and helper/inducer T cells were predominantly infiltrating in the interstitium, but intraglomerular infiltration was rare, except for APSGN. This interstitial infiltration increased proportionally to the level of serum creatinine, and was most prominent in RPGN. Apparently different distribution was seen in APSGN, that is, prominent increase in total number of intra-glomerular monocyte/M phi infiltration with slightly increased T cells. The change was correlated with time after onset; namely the more leucocytic infiltration was observed when the tissue was taken earlier. These data suggest that in APSGN, monocyte/M phi accumulate in glomeruli via cell mediated immunity in addition to humoral immune mechanism resulting in glomerular hypercellularity, whereas in most chronic glomerulonephritis interstitial leucocyte infiltration, particularly helper T cells and monocyte/M phi may play an important role in the progression of glomerulonephritis.  相似文献   
33.
1 Contractile responses of canine intestinal circular and longitudinal muscles to field stimulation (20 Hz, 1 ms, 30 V/cm, for 5 s) were inhibited by treatment with atropine (0.1 microgram/ml), indicating that the response to field stimulation was mediated by acetylcholine (ACh). 2 Prostaglandins E1 (PGE1), PGE2 and PGF2 alpha inhibited the response of circular but not longitudinal muscle to field stimulation, although PGF2 alpha was less effective than PGE1 and E2. 3 PGE1 was much less active in inhibiting the response of circular muscle to ACh than to field stimulation, suggesting that prostaglandins might act predominantly at prejunctional sites to prevent the release of ACh. 4 Indomethacin (1 microgram/ml) potentiated the response of circular muscle but not longitudinal muscle to field stimulation. 5 Release of PGE-like compounds from circular muscle only, was increased by field stimulation at 20 Hz (total of 1000 pulses) and ACh (10 micrograms/ml), but not by a lower frequency (2 Hz, total of 2400 pulses) which produced only a slight contraction. This finding may indicate that prostaglandins were released predominantly from the muscle. 6 Prostaglandins may exert a negative feedback mechanism of excitatory transmission in circular muscle but not in longitudinal muscle of canine small intestine.  相似文献   
34.
The effects of clinically successful periodontal therapy were studied in juvenile periodontitis (JP) and rapidly progressive periodontitis (RP) patients and compared with periodontally healthy subjects (HS). Serum samples were obtained in 35 HS prior to the study and in 12 of these subjects 3-4 years later. Serum samples were obtained from 50 JP patients initially, 9 subjects immediately following surgical therapy and 29 of these subjects 3-4 years later. RP patients provided 46 initial serum samples, 9 following therapy and 27 samples 3-4 years later. Antibody levels were determined utilizing a standardized enzyme-linked immunosorbent assay with Bacteroides gingivalis, B. ochracea, Fusobacterium nucleatum and Actinobacillus actinomycetemcomitans serving as antigens. The JP patients showed an initial rise in antibody levels immediately following therapy followed by a significant decrease in antibody levels 3 to 4 years later. The RP patients did not show an early change in antibody levels but by 3 to 4 years post-therapy, antibody levels had significantly decreased. However, during this study, the antibody levels of JP and RP patients remained significantly higher when compared with HS patients.  相似文献   
35.
MK-0787 (Imipenem)/MK-0791 (Cilastatin sodium), a new compound of Thienamycin, was administered in treatment of 35 patients (36 cases) with chronic complicated UTI or for prevention of serious infections with much complicated factors. The patients were principally treated at a daily dose of 1 g for over 10 days. The efficacy rate of 26 patients who were evaluable in the early phase (4-7 days) was 88.5%, while it became up to 92.3% in the final phase judgment. As for clinical usefulness, the result was obtained to be as high as that of the clinical efficacy. In bacteriological study, 35 strains were clinically isolated including 7 strains of P. aeruginosa from UTI. All the strains disappeared with an eradication rate of 100% after treatment. Strains appearing after Imipenem/Cilastatin sodium treatment mainly consisted of fungi. Usefulness judgements tended to be greater in the final phase than in the early phase. As for side effects, vomiting was recorded in one case, in which the administration was discontinued. In laboratory findings there were 3 cases with elevated GPT, 2 cases with elevated GOT, one case with elevated gamma-GTP, one with thrombocytopenia, and one with eosinophilia each, but these abnormal values were slight and transient. In summary our clinical study showed that Imipenem/Cilastatin sodium was a very effective antibiotic in treatment on moderate or serious UTI or preventive use for infections in compromised hosts. Considering the features of this agent, it might be more effective and useful for clinical use in treatment on polymicrobial infections including stubborn organisms than any other antimicrobial compounds. Furthermore, it was safe and well tolerable in a long term treatment.  相似文献   
36.
We examined the mechanisms of the inhibition of DNA synthesis by a new platinum compound, (-)-( R )-2-aminomethylpyrrolidine(1,1-cyclobutane-dicarboxylato)-2-platinum(II) monohydrate (DWA-2114R), a derivative of the antitumor drug cis- diamminedichloroplatinum(II) (CDDP), using prokaryotic and eukaryotic DNA polymerases. Preincubating activated DNA with CDDP or DWA-2114R reduced its template activity for prokaryotic and eukaryotic DNA polymerases in a dose-dependent manner. DWA2114R required six times greater drug concentration and two times longer incubation time to show the same decrease of the template activity compared to CDDP. Treatment of primed pUC118 ssDNA templates with the two drugs followed by second-strand synthesis by prokaryotic and eukaryotic DNA polymerases revealed that DWA2114R bound to DNA in a similar manner to CDDP and these adducts blocked DNA elongation by DNA polymerases of eukaryotes as well as of prokaryotes. With these two drugs, the elongations by E. coli DNA polymerase I (Klenow fragment), T7 DNA polymerase and calf thymus DNA polymerase α were strongly arrested at guanine-guanine sequences (GG). Stop bands were also observed at adenine-guanine sequences (AG) guanine-adenine-guanine sequences (GAG) and mono-guanine sequence (G). Calf testis DNA polymerase β was also arrested efficiently at AG, GAG and G, but much more weakly at GG. This pattern was common to DWA2114R and CDDP.  相似文献   
37.
38.
Correlation of fetal posture and congenital dislocation of the hip   总被引:1,自引:0,他引:1  
A statistical study was carried out on the incidence of CDH associated with mechanical factors in the uterus, including congenital genu recurvatum. There were 72 cases of CDH among 6559 infants (1.1 per cent). The incidence of CDH was 0.7 per cent in cephalic presentation, 2 per cent in footling presentation and 20 per cent in single-breech presentation. In another series, CDH was found in six of seven infants with congenital genu recurvatum. These findings suggest that a fetal posture with the hip flexed and the knee extended predisposes to the development of CDH.  相似文献   
39.
40.
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