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   40627篇
  免费   2826篇
  国内免费   1201篇
耳鼻咽喉   510篇
儿科学   471篇
妇产科学   496篇
基础医学   6332篇
口腔科学   601篇
临床医学   4004篇
内科学   7039篇
皮肤病学   1103篇
神经病学   3026篇
特种医学   2060篇
外国民族医学   5篇
外科学   4782篇
综合类   2511篇
现状与发展   7篇
一般理论   10篇
预防医学   2015篇
眼科学   985篇
药学   4024篇
  15篇
中国医学   1189篇
肿瘤学   3469篇
  2024年   64篇
  2023年   485篇
  2022年   1290篇
  2021年   1790篇
  2020年   1006篇
  2019年   1153篇
  2018年   1325篇
  2017年   1082篇
  2016年   1443篇
  2015年   2003篇
  2014年   2383篇
  2013年   2557篇
  2012年   3638篇
  2011年   3731篇
  2010年   2241篇
  2009年   1813篇
  2008年   2426篇
  2007年   2282篇
  2006年   1999篇
  2005年   1861篇
  2004年   1417篇
  2003年   1208篇
  2002年   1032篇
  2001年   723篇
  2000年   758篇
  1999年   600篇
  1998年   282篇
  1997年   239篇
  1996年   175篇
  1995年   173篇
  1994年   145篇
  1993年   105篇
  1992年   162篇
  1991年   175篇
  1990年   144篇
  1989年   109篇
  1988年   90篇
  1987年   85篇
  1986年   76篇
  1985年   52篇
  1984年   35篇
  1983年   40篇
  1982年   31篇
  1981年   22篇
  1980年   21篇
  1979年   35篇
  1978年   20篇
  1977年   18篇
  1975年   15篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background contextVertebral artery injuries (VAIs) are rare but serious complications of cervical spine surgery, with the potential to cause catastrophic bleeding, permanent neurologic impairment, and even death. The present literature regarding incidence of this complication largely comprises a single surgeon or small multicenter case series.PurposeWe sought to gather a large sample of high-volume surgeons to adequately characterize the incidence and risk factors for VAI, management strategies used, and patient outcomes after VAI.Study designThe study was constructed as a cross-sectional study comprising all cervical spine patients operated on by the members of the international Cervical Spine Research Society (CSRS).Patient sampleAll patients who have undergone cervical spine surgery by a current member of CSRS as of the spring of 2012.Outcome measuresFor each surgeon surveyed, we collected self-reported measures to include the number of cervical cases performed in the surgeon's career, the number of VAIs encountered, the stage of the case during which the injury occurred, the management strategies used, and the overall patient outcome after injury.MethodsAn anonymous 10-question web-based survey was distributed to the members of the CSRS. Statistical analysis was performed using Student t tests for numerical outcomes and chi-squared analysis for categorical variables.ResultsOne hundred forty-one CSRS members (of 195 total, 72%) responded to the survey, accounting for a total of 163,324 cervical spine surgeries performed. The overall incidence of VAI was 0.07% (111/163,324). Posterior instrumentation of the upper cervical spine (32.4%), anterior corpectomy (23.4%), and posterior exposure of the cervical spine (11.7%) were the most common stages of the case to result in an injury to the vertebral artery. Discectomy (9%) and anterior exposure of the spine (7.2%) were also common time points for an arterial injury. One-fifth (22/111) of all VAI involved an anomalous course of the vertebral artery. The most common management of VAI was by direct tamponade. The outcomes of VAIs included no permanent sequelae in 90% of patients, permanent neurologic sequelae in 5.5%, and death in 4.5%. Surgeons at academic and private centers had nearly identical rates of VAIs. However, surgeons who had performed 300 or fewer cervical spine surgeries in their career had a VAI incidence of 0.33% compared with 0.06% in those with greater than 300 lifetime cases (p=.028).ConclusionsThe overall incidence of VAI during cervical spine surgery reported from this survey was 0.07%. Less experienced surgeons had a higher rate of VAI compared with their more experienced peers. The results of VAI are highly variable, resulting in no permanent harm most of the time; however, permanent neurologic injury or death occur in 10% of cases.  相似文献   
992.
We engineered high aspect ratio Fe2O3 nanorods (with an aspect ratio of 17 : 1) coated with g-C3N4 using a sequential solvothermal method at very low temperature followed by a thermal evaporation method. Here, the high aspect ratio Fe2O3 nanorods were directly grown onto the FTO substrate under relatively low pressure conditions. The g-C3N4 was coated onto a uniform Fe2O3 nanorod film as the heterostructure, exhibiting rational band conduction and a valence band that engaged in surface photoredox reactions by a direct z-scheme mechanism. The heterostructures, particularly 0.75g-C3N4@Fe2O3 nanorods, exhibited outstanding photocatalytic activities compared to those of bare Fe2O3 nanorods. In terms of 4-nitrophenol degradation, 0.75g-C3N4@Fe2O3 nanorods degraded all of the organic pollutant within 6 h under visible irradiation at a kinetic constant of 12.71 × 10−3 min−1, about 15-fold more rapidly than bare Fe2O3. Further, the hydrogen evolution rate was 37.06 μmol h−1 g−1, 39-fold higher than that of bare Fe2O3. We suggest that electron and hole pairs are efficiently separated in g-C3N4@Fe2O3 nanorods, thus accelerating surface photoreaction via a direct z-scheme under visible illumination.

The engineered high aspect ratio of Fe2O3 nanorods coated with g-C3N4 demonstrates z-scheme mechanism, showing the best performance in 4-nitrophenol photodegradation and H2 evolution.  相似文献   
993.
994.
Background and Study AimsEndoscopic submucosal dissection (ESD) is the most effective treatment for early gastric cancer or gastric adenoma. However, ESD results in iatrogenic ulcers and postoperative bleeding from ulcers. This study aimed to evaluate the effect of using a proton pump inhibitor (PPI) alone, a PPI + rebamipide combination therapy, and an H2 receptor antagonist (H2RA) + rebamipide combination therapy on ulcer healing after ESD.Patients and MethodsA total of 204 patients who underwent ESD from April 2014 to July 2017 at Dong-A University Hospital were randomly assigned to the following groups: PPI-alone group, PPI + rebamipide combination therapy group, and H2RA + rebamipide combination therapy group. However, only 156 patients were studied since we excluded those who were lost to follow-up or had diseases other than early gastric cancer or gastric adenoma. Twenty-eight days after ESD, we evaluated the ulcer residual ratio, S stage rates, ulcer bleeding ratio, and gastric pH.ResultsThis study included 156 patients (PPI-alone group: 52 patients; PPI + rebamipide group: 52 patients; H2RA + rebamipide group: 52 patients). The ulcer residual ratios were 24.3 ± 14.2%, 17.0 ± 12.1%, and 21.0 ± 13.8% in the PPI alone, PPI + rebamipide, and H2RA + rebamipide groups, respectively (P = 0.048).ConclusionsPPI + rebamipide was more effective in reducing the ulcer residual ratio after ESD. There was no statistical difference in ulcer stage and delayed bleeding after ESD among the groups. These findings showed that PPI + rebamipide had limited benefits after ESD.  相似文献   
995.
The administration of diluted bee venom (DBV) into an acupuncture point has been utilized traditionally in Eastern medicine to treat chronic pain. We demonstrated previously that DBV has a potent anti-nociceptive efficacy in several rodent pain models. The present study was designed to examine the potential anti-nociceptive effect of repetitive DBV treatment in the development of below-level neuropathic pain in spinal cord injury (SCI) rats. DBV was applied into the Joksamli acupoint during the induction and maintenance phase following thoracic 13 (T13) spinal hemisection. We examined the effect of repetitive DBV stimulation on SCI-induced bilateral pain behaviors, glia expression and motor function recovery. Repetitive DBV stimulation during the induction period, but not the maintenance, suppressed pain behavior in the ipsilateral hind paw. Moreover, SCI-induced increase in spinal glia expression was also suppressed by repetitive DBV treatment in the ipsilateral dorsal spinal cord. Finally, DBV injection facilitated motor function recovery as indicated by the Basso–Beattie–Bresnahan rating score. These results indicate that the repetitive application of DBV during the induction phase not only decreased neuropathic pain behavior and glia expression, but also enhanced locomotor functional recovery after SCI. This study suggests that DBV acupuncture can be a potential clinical therapy for SCI management.  相似文献   
996.
997.
Cordyceps species including Cordyceps bassiana are a notable anti-cancer dietary supplement. Previously, we identified several compounds with anti-cancer activity from the butanol fraction (Cb-BF) of Cordyceps bassiana. To expand the structural value of Cb-BF-derived anti-cancer drugs, we employed various chemical moieties to produce a novel Cb-BF-derived chemical derivative, KTH-13-amine-monophenyl [4-isopropyl-2-(1-phenylethyl) aniline (KTH-13-AMP)], which we tested for anti-cancer activity. KTH-13-AMP suppressed the proliferation of MDA-MB-231, HeLa, and C6 glioma cells. KTH-13-AMP also dose-dependently induced morphological changes in C6 glioma cells and time-dependently increased the level of early apoptotic cells stained with annexin V-FITC. Furthermore, the levels of the active full-length forms of caspase-3 and caspase-9 were increased. In contrast, the levels of total forms of caspases-3, caspase-8, caspase-9, and Bcl-2 were decreased in KTH-13-AMP treated-cells. We also confirmed that the phosphorylation of STAT3, Src, and PI3K/p85, which is linked to cell survival, was diminished by treatment with KTH-13-AMP. Therefore, these results strongly suggest that this compound can be used to guide the development of an anti-cancer drug or serve as a lead compound in forming another strong anti-proliferative agent.  相似文献   
998.
A chemical process was developed to prepare N-doped micro-nano carbon spheres with multi-scale pore structures via carbonization of N-PF/PMMA interpenetrating polymer networks, which contain melamine resin as the nitrogen source, PF as the carbon source, and polymethylmethacrylate (PMMA) as the pore-former. The N-content of N-doped micro-nano carbon spheres was controlled by adjusting the mass ratio of melamine and phenol before polymerization. The N-doped micro-nano carbon spheres as electrode materials possess appropriate pore size distribution, higher specific surface area (559 m2 g−1) and consistently dispersed nitrogen atoms with adjustable doping content. These distinct characteristics endow the prospective electrode materials with excellent performance in electrochemical capacitors. In particular, N-CS-IPN-4 exhibits the highest specific capacitance of 364 F g−1 at 0.5 A g−1 in 6 M KOH aqueous electrolyte in a three-electrode system. It also possesses superior rate capability (57.7% retention at current densities ranging from 0.5 to 50 A g−1) and excellent cycling performance at 2 A g−1 (100% retention after 10 000 cycles). All these results confirm that the N-doped micro-nano carbon spheres are promising electrochemical capacitor materials, which possesses the advantages of simple preparation procedure, multi-scale pore structures, higher specific surface areas, easy adjustment of N-content and excellent electrochemical properties.

The N-doped micro-nano carbon spheres with multi-scale pore structures was prepared via carbonization of N-PF/PMMA interpenetrating polymer networks, which contain melamine resin as nitrogen source, PF as carbon source, and PMMA as pore-former.  相似文献   
999.
1000.
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