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   5052篇
  免费   304篇
  国内免费   27篇
耳鼻咽喉   68篇
儿科学   183篇
妇产科学   102篇
基础医学   428篇
口腔科学   107篇
临床医学   476篇
内科学   1065篇
皮肤病学   99篇
神经病学   222篇
特种医学   102篇
外科学   1095篇
综合类   105篇
一般理论   3篇
预防医学   221篇
眼科学   123篇
药学   422篇
中国医学   17篇
肿瘤学   545篇
  2024年   3篇
  2023年   53篇
  2022年   115篇
  2021年   260篇
  2020年   120篇
  2019年   170篇
  2018年   232篇
  2017年   156篇
  2016年   201篇
  2015年   195篇
  2014年   243篇
  2013年   306篇
  2012年   474篇
  2011年   457篇
  2010年   268篇
  2009年   185篇
  2008年   309篇
  2007年   330篇
  2006年   260篇
  2005年   226篇
  2004年   198篇
  2003年   171篇
  2002年   127篇
  2001年   41篇
  2000年   26篇
  1999年   40篇
  1998年   21篇
  1997年   11篇
  1996年   19篇
  1995年   20篇
  1994年   11篇
  1993年   6篇
  1992年   21篇
  1991年   12篇
  1990年   11篇
  1989年   7篇
  1988年   4篇
  1987年   9篇
  1986年   8篇
  1985年   7篇
  1984年   9篇
  1983年   5篇
  1981年   3篇
  1979年   3篇
  1973年   2篇
  1972年   2篇
  1970年   6篇
  1969年   5篇
  1968年   4篇
  1966年   3篇
排序方式: 共有5383条查询结果,搜索用时 15 毫秒
51.
The goal of this study was to determine the coefficient of permeability as well as the rate of carbonation of concrete constructed with rice husk ash (RHA) as a partial replacement for cement (i.e., 5%, 10%, and 15%) and two different concentrations of soap solutions (i.e., 1 percent and 2 percent). The microstructural studies of RHA, and carbonated samples have been conducted by using Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) analysis. According to this study, the carbonation depth of concrete made with 1% and 2% soap solution concentration and without rice husk ash decreased by 11.89% and 46.55%, respectively. From the results, it may also be observed that the carbonation depth of concrete made with up to 10% replacement of cement by rice husk ash led to maximum carbonation resistance, while more than 10% replacement of cement showed higher carbonation depth. It is also observed that the coefficient of permeability of concrete with 2% soap solution significantly decreased as compared to the 1% soap solution and control mix. It may be observed from the SEM images that 0% soap solution (M1) concrete has a very rough concrete surface which may indicate more voids. However, 2% soap solution concrete has a much smoother surface, which indicates a smaller number of voids. Furthermore, the SEM images showed that the soap solution helps in filling the voids of concrete which ultimately helps in reduction in permeability. Energy Dispersive X-Ray Analysis (EDX) of concrete with 0% (M1) and 2% (M6) soap solution disclosed that the concrete with 2% soap solution (M6) exhibited more silica element formation than the concrete with no soap solution (M1).  相似文献   
52.
Self‐reported measures of health, in the context of developed countries, are well‐researched and commonly regarded as reliable predictors of the underlying health of the population. However, the validity of these measures is under‐researched and questionable in the context of low‐ and middle‐income countries. The authors used Longitudinal Ageing Study in India (LASI) survey data from India to compare self‐reported hypertension with biometrically‐measured hypertension. The results are reported in terms of sensitivity, specificity, and kappa as a measure of agreement. Logistic regression was undertaken to examine the characteristics of those who were unaware of their hypertensive status. Our analysis showed a low sensitivity of 56% and a high specificity of 90.5%. Agreement between self‐reported data and biometric measurement of hypertension was observed to be moderate (κ = 0.48). Large variations were observed among states and sub‐groups. The odds of false negative reporting of hypertension were lower in the individuals with higher age, high education, and greater wealth status. The authors conclude that self‐reported hypertension has important limitations and may be a source of systematic bias. It is recommended that planning and policy‐making in India be based more on an objective assessment of hypertension.  相似文献   
53.
54.
The freshwater snails, Filopaludina bengalensis and Pila globosa are widely used for human consumption and as a feed in aquaculture in India and Bangladesh. The generation of shells as a waste product following meat extraction from the live snails incites their utilisation as a potential biomaterial. Shell dust was prepared from the dried shells of F. bengalensis (FSD) and P. globosa (PSD) and employed for phosphate adsorption from aqueous solutions. Batch adsorption experiments were performed to examine the effects of various experimental conditions, such as biosorbent dose, agitation speed, temperature, contact time, pH, initial concentration of phosphate ions, and presence of co-existing ions. SEM, EDS, ICP-OES, FTIR, and XRD results indicated that phosphate ions were adsorbed onto the surface of shell dust particles. The experimental data fitted with the Langmuir isotherm with a maximum adsorption capacity of 62.50 and 66.66 mg g−1 for FSD and PSD. The pseudo-second order kinetic model was well fitted, indicating the chemical adsorption process, and the thermodynamic parameters indicated that the adsorption mechanism of phosphate was spontaneous, feasible, and endothermic. Therefore, the results have established the potentiality of the waste shells of edible snails to be used as an eco-friendly and low-cost biosorbent for phosphate removal from wastewater.

The waste shells of Filopaludina bengalensis and Pila globosa can be used as an eco-friendly and low-cost biosorbent for phosphate removal from eutrophicated water or industrial wastewater.  相似文献   
55.

Ethnopharmacological relevance

Roots of Asparagus racemosus Willd (Shatavari in vernacular) are widely used in Ayurveda as Rasayana for immunostimulation, galactogogue as also in treatment of conditions like ulcers and cancer. Various studies have indicated immunomodulatory properties of Shatavari root extracts and formulations.

Aim of the study

To study the effect of standardized Asparagus racemosus root aqueous extract (ARE) on systemic Th1/Th2 immunity of SRBC sensitized animals.

Materials and methods

We used HPTLC to quantify steroidal saponins (Shatavarin IV, Immunoside®) and flow cytometry to study effects of ARE on Th1/Th2 immunity. SRBC specific antibody titres and DTH responses were also monitored as markers of Th2 and Th1 responses, respectively. We also studied lymphocyte proliferation. Cyclosporin, cyclophosphamide and levamisole were used as controls.

Results

Treatment with ARE (100 mg/(kg b.w. p.o.)) resulted in significant increase of CD3+ and CD4/CD8+ percentages suggesting its effect on T cell activation. ARE treated animals showed significant up-regulation of Th1 (IL-2, IFN-g) and Th2 (IL-4) cytokines suggesting its mixed Th1/Th2 adjuvant activity. Consistent to this, ARE also showed higher antibody titres and DTH responses. ARE, in combination with LPS, Con A or SRBC, produced a significant proliferation suggesting effect on activated lymphocytes.

Conclusion

The study suggests mixed Th1/Th2 activity of ARE supports its immunoadjuvant potential.  相似文献   
56.
Almost 19 members of the tumor necrosis factor (TNF) superfamily have been identified that interact with 29 different receptors. Whether these receptors communicate with each other is not understood. Recently, we have shown that receptor activator of NF-kappaB ligand signaling is modulated by genetic deletion of the TNF receptor. In the current report, we investigated the possibility of a cross-talk between Fas and TNF-alpha signaling pathway in macrophage cell lines derived from wild-type (WT) mice and from mice with genetic deletion of the type 1 TNF receptor (p60(-/-)), the type 2 TNF receptor (p80(-/-)), or both receptors (p60(-/-)p80(-/-)). We found that the macrophages expressing TNF receptors were highly sensitive to apoptosis induced by anti-Fas. The genetic deletion of TNF receptors, however, made the cells resistance to anti-Fas-induced apoptosis. Anti-Fas induced activation of caspase-3 and PARP cleavage in WT cells but not in TNF receptor-deleted cells. This difference was found to be independent of the expression of Fas, Fas-associated protein with death domain (FADD) or TNF receptor-associated death domain (TRADD). We found that anti-Fas induced recruitment of TNFR1 into Fas-complex. We also found that TRADD, which mediates TNF signaling, was constitutively bound to Fas receptor in TNF receptor-deleted cells but not in wild-type cells. Transient transfection of TNFR1 in TNFR1-deleted cells sensitized them to anti-Fas-induced apoptosis. Overall our results demonstrate that Fas signaling is modulated by the TNF receptors and thus provide the evidence of cross-talk between the receptors of two cytokines.  相似文献   
57.
58.
ObjectiveThe aim of the study is to evaluate the effect of deferred androgen deprivation therapy on biochemical recurrence (BCR) and other survival parameters in node-positive prostate cancer patients after robot-assisted radical prostatectomy with bilateral extended pelvic lymph node dissection (RARP + EPLND).Materials and methodsOf the 453 consecutive RARP procedures performed from 2011 to 2018, 100 patients with no prior use of androgen deprivation therapy were found to be lymph node (LN) positive and were observed, with initiation of salvage treatment at the time of BCR only. Patients were divided into 1 or 2 LNs (67)—and more than 2 LNs (33)—positive groups to assess survival outcomes.ResultsAt a median follow-up of 21 months (1–70 months), the LN group (p < 0.000), preoperative prostate-specific antigen (PSA, p = 0.013), tumor volume (TV, p = 0.031), and LND (p = 0.004) were significantly associated with BCR. In multivariate analysis, only the LN group (p = 0.035) and PSA level (p = 0.026) were statistically significant. The estimated BCR-free survival rates in the 1/2 LN group were 37.6% (27%–52.2%), 26.5% (16.8%–41.7%), and 19.9% (9.6%–41.0%) at 1, 3, and 5 years, respectively, with a hazard of developing BCR of 0.462 (0.225–0.948) compared with the more than 2 LN-positive group. Estimated 5-year overall survival, cancer-specific, metastasis-free, and local recurrence-free survival rates were 88.4% (73.1%–100%), 89.5% (74%–100%), 65.1% (46.0%–92.1%), and 94.8% (87.2%–100.0%), respectively, for which none of the factors were significant. Based on cutoff values for PSA, TV, and LND of 30 ng/mL, 30%, and 10%, respectively, the 1/2 LN group was substratified, wherein the median BCR-free survival for the low- and intermediate-risk groups was 40 and 12 months, respectively.ConclusionsNearly one fourth and one fifth of 1/2 node-positive patients were BCR-free at 3 and 5 years after RARP + EPLND. Further substratification using PSA, TV, and LN density may help in providing individualized care regarding the initiation of adjuvant therapy.  相似文献   
59.
60.
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