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   14255篇
  免费   687篇
  国内免费   90篇
耳鼻咽喉   185篇
儿科学   277篇
妇产科学   126篇
基础医学   1850篇
口腔科学   308篇
临床医学   835篇
内科学   3890篇
皮肤病学   185篇
神经病学   1211篇
特种医学   561篇
外科学   2561篇
综合类   53篇
一般理论   2篇
预防医学   351篇
眼科学   145篇
药学   834篇
中国医学   23篇
肿瘤学   1635篇
  2024年   15篇
  2023年   98篇
  2022年   201篇
  2021年   337篇
  2020年   173篇
  2019年   271篇
  2018年   344篇
  2017年   271篇
  2016年   334篇
  2015年   339篇
  2014年   421篇
  2013年   524篇
  2012年   876篇
  2011年   914篇
  2010年   591篇
  2009年   475篇
  2008年   893篇
  2007年   973篇
  2006年   917篇
  2005年   889篇
  2004年   925篇
  2003年   867篇
  2002年   861篇
  2001年   195篇
  2000年   180篇
  1999年   188篇
  1998年   237篇
  1997年   147篇
  1996年   156篇
  1995年   101篇
  1994年   107篇
  1993年   107篇
  1992年   107篇
  1991年   102篇
  1990年   98篇
  1989年   86篇
  1988年   75篇
  1987年   79篇
  1986年   69篇
  1985年   58篇
  1984年   60篇
  1983年   58篇
  1982年   33篇
  1981年   33篇
  1980年   35篇
  1979年   26篇
  1978年   30篇
  1977年   24篇
  1976年   20篇
  1975年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We investigated the relationship between the antinociceptive effect of the opiate agonist loperamide at the spinal level and its inhibitory effect on calcium influx. Intrathecal administration of loperamide showed a significant antinociceptive effect in the formalin test, which was not prevented by naloxone. On the other hand, no significant effects were observed by nicardipine, an L-type specific blocker, or by BAY K8644, an L-type specific agonist, suggesting no significant role of L-type calcium channels in nociceptive signal transduction. Loperamide suppressed the calcium influx in dorsal root ganglion neurons. As the antinociceptive effect of loperamide was not affected by naloxone or other calcium channel blocking toxins, and loperamide showed a direct inhibitory effect on calcium-influx, the analgesic effect of intrathecally injected loperamide might be due to its blockade of the voltage-dependent calcium channels at the terminals of the primary afferent fibers.  相似文献   
62.
A series of pseudo-peptide analogs of the Arg-Gly-Asp (RGD) sequence of fibronectin have been synthe-sized, and their anti-metastatic effects in mice and inhibitory effects on tumor cell invasion in vitro have been examined. The partially modified retro pseudo-peptide of RGD, Rrev-COCH2CO-D (FC-63), was more effective in inhibiting tumor metastasis than the original RGDS peptide. Replacement of the malonyl moiety of FC-63 with a carboxyethylene linkage (Rrev-COCH2CH2-D, FC-303 ) achieved more potent inhibition of lung metastasis of melanoma cells than FC-63. Among the analogs, FC-336, a p-xylylendiamine derivative having two FC-303 moieties, showed the most potent inhibitory effect on experimental lung metastasis produced by i.v. co-injection with B16-BL6 melanoma or colon 26 M3.1 cells in a dose-dependent manner. Multiple administrations of FC-336 after tumor inoculation also showed efficient therapeutic potency against spontaneous lung metastasis of B16-BL6 melanoma in mice. Furthermore, FC-336 effectively inhibited the invasion, migration and adhesion of tumor cells in vitro, but its inhibitory effects were not more than those of RGDS peptide. Zymography analysis revealed that FC-336 inhibited the degradation of gelatin substrate by matrix metalloproteinases (MMPs) produced by tumor cells, while the RGDS peptide did not affect the enzymatic degradation. These findings indicate that the pseudo-peptides of the RGD sequence, possessing the inhibitory property of the degradation by MMPs differently from original RGD-containing peptides, may be advantageous and useful in preventing tumor metastasis. © Rapid Science 1998  相似文献   
63.
IL-5, IL-10 and lipopolysaccharide (LPS) are known to activateB-1 cells in vivo in normal mice and anti-red blood cell autoantibodytransgenic mice (HL mice). To assess the exact role of IL-5in proliferation and activation of peritoneal B-1 cells, weanalyzed IL-5 receptor chain-deficient HL (IL-5R–/–x HL) mice generated by the cross between IL-5R–/–and HL mice. In IL-5R–/– x HL mice, Ig-producingB-1 cells in the peritoneal cavity were negligible, althoughthe total number of B-1 cells in the peritoneal cavity wereas many as 30% of that in HL mice. Moreover, LPS- or IL-10-induceddifferentiation of B-1 cells into antibody-producing cells wasseverely impaired in IL-5R–/– x HL mice. We alsoused in vivo 5-bromo-2'-deoxyuridine labeling to estimate theproliferation of B-1 cells in IL-5R–/– mice. Theabsence of IL-5R did not affect spontaneous proliferation ofperitoneal B-1 cells. However, induced proliferation of peritorealB-1 cells by oral administration of LPS was markedly impairedin IL-5R–/– mice. These results suggest that IL-5is required for activation-associated proliferation of B-1 cellsbut not for their spontaneous proliferation and support theidea that IL-5 plays an important role on the induction of autoantibodyproduction from B-1 cells.  相似文献   
64.
Avulsion fractures of the calcaneal tuberosity, although relatively uncommon, occur more frequently in patients with osteoporosis and in the elderly. The results of closed manipulation are poor in these fractures, usually requiring open reduction and internal fixation. However, it is difficult to fix the bone fragment rigidly, because the avulsed bone fragment is small and thin, and the bone quality of the calcaneal body in the elderly is poor. Hence, it is necessary to limit prolonged weight-bearing after the operation. We performed an innovative surgical procedure of suture fixation to the anchor screw in four cases, following which earlier postoperative rehabilitation with full weight-bearing walking and range of motion exercises was possible, and bony union was achieved without repeated displacement of the fragment in all patients. We believe this technique would prove useful in surgical management of calcaneal tuberosity avulsion fractures.  相似文献   
65.
Pharyngeal cancer patients treated with intensity-modulated proton therapy (IMPT) using a model-based approach were retrospectively reviewed, and acute toxicities were analyzed. From June 2016 to March 2019, 15 pharyngeal (7 naso-, 5 oro- and 3 hypo-pharyngeal) cancer patients received IMPT with robust optimization. Simulation plans for IMPT and intensity-modulated X-ray therapy (IMXT) were generated before treatment. We also reviewed 127 pharyngeal cancer patients with IMXT in the same treatment period. In the simulation planning comparison, all of the normal-tissue complication probability values for dysphagia, dysgeusia, tube-feeding dependence and xerostomia were lower for IMPT than for IMXT in the 15 patients. After completing IMPT, 13 patients completed the evaluation, and 12 of these patients had a complete response. The proportions of patients who experienced grade 2 or worse acute toxicities in the IMPT and IMXT cohorts were 21.4 and 56.5% for dysphagia (P < 0.05), 46.7 and 76.3% for dysgeusia (P < 0.05), 73.3 and 62.8% for xerostomia (P = 0.43), 73.3 and 90.6% for mucositis (P = 0.08) and 66.7 and 76.4% for dermatitis (P = 0.42), respectively. Multivariate analysis revealed that IMPT was independently associated with a lower rate of grade 2 or worse dysphagia and dysgeusia. After propensity score matching, 12 pairs of IMPT and IMXT patients were selected. Dysphagia was also statistically lower in IMPT than in IMXT (P < 0.05). IMPT using a model-based approach may have clinical benefits for acute dysphagia.  相似文献   
66.
Delayed single-photon emission tomograpic (SPET) images after an intravenous bolus injection of iodine-123 iomazenil have been used as a relative map of benzodiazepine receptor binding. We determined the optimal scan time for obtaining such a map and assessed the errors of the map. SPET and blood data from six healthy volunteers and five patients were used. A three-compartment kinetic model was employed in simulation studies and analyses of actual data. The simulation studies suggested that, in the normal brain, the scan time at which a single SPET image best represented the relative receptor binding was 3.0–3.5 h post-injection. This finding was supported by actual data from the volunteers. The simulation studies also suggested that the optimal scan time was not greatly changed by the variability of the input functions, and that the error in the SPET image contrast in the vicinity of the optimal scan time was not increased by changes in the tracer kinetics in the entire brain. The SPET image contrast in the patients at 3.0 h post-injection agreed well with the reference receptor binding estimated by kinetic analysis, with a mean error of 3.6%. These findings support the use of a single SPET image after bolus injection of [123I]iomazenil as a relative map of benzodiazepine receptor binding. For this purpose, a SPET scan time of 3.0-3.5 h post-injection is recommended.  相似文献   
67.
This review reassesses the role of hormonal therapy in breast cancer specifically the sequential or concurrent use of endocrine therapy and the combined use of chemotherapy with endocrine therapy. In advanced disease the sequential use of hormone therapies is generally recommended rather than the combined use of various hormonal agents, though combination hormonal therapy offers advantages in certain subsets of patients. The efficacy of combined chemo-endocrine therapy is questionable. Chemotherapy with estrogenic recruitment is an attractive but still experimental concept. However, in an adjuvant setting there is evidence that combined chemo-endocrine therapy causes a significant increase in disease-free and/or overall survival, particularly in postmenopausal patients with estrogen receptor (Expositive tumors. While hormonal treatment strategies have clearly benefitted from randomized studies, data regarding optimal endocrine therapy are still insufficient.  相似文献   
68.
69.
70.
Objective: To evaluate the effect of prednisolone plus low-dose aspirin (PSL/LDA) in women with autoimmune conditions who were enrolled in an IVF-ET program.

Design: A retrospective clinical study.

Setting: In vitro fertilization unit, Niigata University Hospital, Niigata, Japan.

Patient(s): Three hundred seven women who underwent IVF-ET between January 1996 and December 1997.

Intervention(s): Prednisolone (10 mg/d) and aspirin (81 mg/d) were administered to the women with autoantibodies who chose to participate.

Main Outcome Measure(s): Pregnancy and implantation rates with IVF-ET.

Result(s): Women undergoing IVF who had positive antinuclear antibodies, with or without antiphospholipid antibodies, had significantly lower pregnancy and implantation rates than did women without autoantibodies (14.8% versus 21.7% and 6.8% versus 10.4%, respectively). The administration of PSL/LDA to women with antinuclear antibodies significantly improved the outcome of IVF-ET (40.6% pregnancy rate and 20.3% implantation rate).

Conclusion(s): A high proportion of women who are undergoing IVF-ET have autoantibodies, which are associated with poor IVF outcomes. The administration of PSL/LDA to these women may improve their implantation rate.  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