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   4312篇
  免费   278篇
  国内免费   42篇
耳鼻咽喉   62篇
儿科学   136篇
妇产科学   100篇
基础医学   369篇
口腔科学   56篇
临床医学   433篇
内科学   904篇
皮肤病学   142篇
神经病学   300篇
特种医学   809篇
外科学   501篇
综合类   54篇
一般理论   2篇
预防医学   193篇
眼科学   241篇
药学   119篇
中国医学   5篇
肿瘤学   206篇
  2021年   29篇
  2019年   40篇
  2018年   52篇
  2017年   43篇
  2016年   42篇
  2015年   53篇
  2014年   65篇
  2013年   145篇
  2012年   134篇
  2011年   126篇
  2010年   103篇
  2009年   111篇
  2008年   130篇
  2007年   136篇
  2006年   159篇
  2005年   182篇
  2004年   159篇
  2003年   134篇
  2002年   145篇
  2001年   130篇
  2000年   124篇
  1999年   128篇
  1998年   134篇
  1997年   109篇
  1996年   98篇
  1995年   90篇
  1994年   89篇
  1993年   73篇
  1992年   82篇
  1991年   100篇
  1990年   87篇
  1989年   120篇
  1988年   111篇
  1987年   139篇
  1986年   109篇
  1985年   90篇
  1984年   67篇
  1983年   45篇
  1982年   43篇
  1981年   39篇
  1979年   61篇
  1978年   33篇
  1977年   45篇
  1976年   51篇
  1975年   45篇
  1974年   36篇
  1973年   41篇
  1972年   31篇
  1971年   34篇
  1970年   33篇
排序方式: 共有4632条查询结果,搜索用时 0 毫秒
91.
92.
93.

Background

Ambulation is an essential aspect of daily living and is often impaired after brain and spinal cord injuries. Despite the implementation of standard neurorehabilitative care, locomotor recovery is often incomplete.

Objective

In this randomized, sham-controlled, double-blind, parallel design study, we aimed to determine if anodal transcutaneous spinal direct current stimulation (anodal tsDCS) could improve training effects on locomotion compared to sham (sham tsDCS) in healthy subjects. Methods: 43 participants underwent a single backwards locomotion training (BLT) session on a reverse treadmill with concurrent anodal (n = 22) or sham (n = 21) tsDCS. The primary outcome measure was speed gain measured 24 h post-training. We hypothesized that anodal tsDCS + BLT would improve training effects on backward locomotor speed compared to sham tsDCS + BLT. A subset of participants (n = 31) returned for two additional training days of either anodal (n = 16) or sham (n = 15) tsDCS and underwent (n = 29) H-reflex testing immediately before, immediately after, and 30 min post-training over three consecutive days.

Results

A single session of anodal tsDCS + BLT elicited greater speed gain at 24 h relative to sham tsDCS + BLT (p = 0.008, two-sample t-test, adjusted for one interim analysis after the initial 12 subjects). Anodal tsDCS + BLT resulted in higher retention of the acquired skill at day 30 relative to sham tsDCS + BLT (p = 0.002) in the absence of significant group differences in online or offline learning over the three training days (p = 0.467 and p = 0.131). BLT resulted in transient down-regulation of H-reflex amplitude (Hmax/Mmax) in both test groups (p < 0.0001). However, the concurrent application of anodal-tsDCS with BLT elicited a longer lasting effect than sham-tsDCS + BLT (p = 0.050).

Conclusion

tsDCS improved locomotor skill acquisition and retention in healthy subjects and prolonged the physiological exercise-mediated downregulation of excitability of the alpha motoneuron pool. These results suggest that this strategy is worth exploring in neurorehabilitation of locomotor function.  相似文献   
94.
Du  X; Beutler  L; Ruan  C; Castaldi  PA; Berndt  MC 《Blood》1987,69(5):1524-1527
Two new murine monoclonal antibodies, AK 1 and SZ 1, reactive with the human platelet glycoprotein (GP) Ib-IX complex have been produced by the hybridoma technique. Both AK 1 and SZ 1 immunoprecipitated the GP Ib-IX complex from Triton X-100-solubilized, periodate-labeled platelets. With trypsinized, labeled platelets, AK 1, SZ 1, and FMC 25 (epitope on GP IX) immunoprecipitated a membrane-bound proteolytic fragment of the GP Ib-IX complex consisting of GP IX and an congruent to 25,000 mol wt remnant of the alpha-chain of GP lb disulfide-linked to the beta-subunit. Unexpectedly, although AK 1 and SZ 1 immunoprecipitated purified GP Ib-IX complex, neither antibody immunoprecipitated the individual components of this complex, GP Ib or GP IX. When GP Ib and GP IX were recombined, however, AK 1 and SZ 1 again immunoprecipitated the reformed complex, strongly suggesting that both antibodies were recognizing an epitope present only on the intact complex. Cross-blocking studies indicated that AK 1 and SZ 1 recognized a very similar or identical epitope that was proximal to the epitope for FMC 25. Both AK 1 and SZ 1 bound to a similar number of binding sites (congruent to 25,000) on intact platelets as monoclonal antibodies directed against either GP lb or GP IX. The combined data suggests that GP lb and GP IX are fully complexed in the intact platelet membrane.  相似文献   
95.
Using data from The Collaborative Study on the Genetics of Alcoholism, we compare direct interview diagnoses of alcohol dependence to those obtained by history from family members. Using a requirement of three or more positive implications by history, the specificity, sensitivity, and positive predictive values are 98%, 39%, and 45%, respectively.
A logistic analysis found the gender of the relative and alcoholism in the informant to be significant, but not the gender of the informant. The partial odds ratio of a diagnosis at interview associated with a positive family history diagnosis was 13.6. The relationship between the informant and relative was significant, with negative reports from an offspring or mate more influential than a negative report from a parent or second-degree relative.
We derived a recursive equation to combine a variable number of family history reports, wherein the probabilities associated with a single report are computed from the logistic analysis. This permits the use of family history information both as a proxy for an uninterviewed relative, as well as a second source of information to be used in the analysis of genetic family data.  相似文献   
96.
The myeloproliferative syndrome induced by the myeloproliferative sarcoma virus (MPSV) in DBA/2 mice stimulates the proliferation of pluripotent hemopoietic stem cells (HSC) and of progenitors committed toward granulomacrophagic and erythroid cell lines. This stimulation may result from a direct effect of the MPSV on HSC or from an indirect effect via locally secreted factors. Normal isogenic bone marrow cells were incubated in the mixed colony-forming unit system in semisolid medium supplemented with conditioned media obtained after incubating neoplastic spleen cells for 3 days at 37 degrees C. These spleen conditioned media contain an activity that is physically separable from MPSV by ultracentrifugation and which, in the presence of a very low quantity of erythropoietin, can induce in vitro the proliferation and differentiation of pluripotent HSC, detected by this Mix-CFU technique. We termed this activity mixed-colonies promoting activity (MPA). These results suggest that the hyperplasia of the nonlymphoid hematopoietic system in the neoplastic spleen results from an indirect effect of the MPSV on pluripotent HSC via locally secreted factors.  相似文献   
97.
OBJECTIVE: Adenosine exerts antiinflammatory effects via activation of the A3 adenosine receptor (A3AR), a Gi protein-associated cell-surface receptor, overexpressed in synovial tissue and peripheral blood mononuclear cells (PBMC) in patients with active rheumatoid arthritis (RA). CF101 is a highly specific orally bioavailable A3AR agonist. METHODS: This was a multicenter study, blinded to dose, designed to assess the clinical activity and safety of CF101 in active RA. Seventy-four patients were randomized to receive 0.1, 1.0, or 4.0 mg CF101 bid for 12 weeks. The primary efficacy endpoint was American College of Rheumatology 20% response (ACR20) at Week 12. A3AR expression levels were analyzed in PBMC from 18 patients. RESULTS:. Maximal responses were observed with 1.0 mg bid, lower at 0.1 and 4.0 mg bid. At 12 weeks, 55.6%, 33.3%, and 11.5% of the patients receiving 1.0 mg CF101 achieved ACR20%, 50%, and 70% responses, respectively. CF101 was generally well tolerated, with mild headache (4.1%), nausea (2.7%), and rash (2.7%) being the most common treatment-related adverse events. Statistically significant correlations between A3AR overexpression at baseline and ACR50 and ACR70 responses were observed. CONCLUSION: CF101 administered bid for 12 weeks resulted in improvement in signs and symptoms of RA that did not achieve statistical significance, and was safe and well tolerated. The expression level of A3AR was directly correlated with patient responses to CF101, suggesting its utilization as a biomarker for the pharmacodynamic and therapeutic effects of this novel agent. These findings require confirmation in a double-blind randomized placebo-controlled trial, currently under way.  相似文献   
98.
99.
In an attempt to immortalize the gene products of single neurons, somatic cell hybrids were produced by fusion of embryonic rat dorsal root ganglion (DRG) neurons with mouse neuroblastoma cells. Embryonic day 13 rat DRGs were fused with mouse neuroblastoma cells deficient in hypoxanthine phosphoribosyltransferase (HPRT; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8). The hybrid cells were selected in medium with 100 microM hypoxanthine/1 microM aminopterin/12 microM thymidine to eliminate the neuroblastoma cells and with cis-hydroxyproline to retard fibroblast growth. Of the 17 lines derived, 4 manifested neuronal properties and were cloned. These lines retain both rat and mouse chromosomes and synthesize characteristic rat and mouse isoenzymes. Neuronal gangliosides, action potentials, and extensive neurite-like processes are exhibited by these hybrid cells, properties characteristic of DRG neurons but not of the neuroblastoma parent. Each line manifests a unique combination of action-potential properties and cell-surface markers, suggesting the selective expression of subsets of DRG neuronal genes. All of these neuronal properties are expressed constitutively, without the need for chemical induction or mitotic inhibition, and stably, without diminution after at least 5 months in culture. These lines may prove useful in the identification and isolation of gene products that characterize individual or small subsets of DRG neurons.  相似文献   
100.

Purpose of Review

The purpose of this review is to evaluate and explain our current understanding of the clinical use of buprenorphine in the treatment of chronic pain.

Recent Findings

There has been few high-quality, unbiased studies performed on the use of buprenorphine in the treatment of chronic pain.

Summary

Buprenorphine is an effective and safe analgesic that is tolerated at least as well, if not better, than other opioids. Given its safety and mechanistic advantages, the authors believe there is an important role for buprenorphine in the treatment of chronic pain severe enough to warrant the use of an opioid analgesic. Though data is lacking for superiority in chronic pain states, the other advantages of the molecule make it the preferential first-line opioid for around-the-clock pain in our practice.
  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