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   2915篇
  免费   160篇
  国内免费   84篇
耳鼻咽喉   29篇
儿科学   52篇
妇产科学   10篇
基础医学   372篇
口腔科学   180篇
临床医学   222篇
内科学   588篇
皮肤病学   56篇
神经病学   236篇
特种医学   405篇
外科学   220篇
综合类   62篇
预防医学   130篇
眼科学   56篇
药学   254篇
中国医学   20篇
肿瘤学   267篇
  2024年   2篇
  2023年   23篇
  2022年   71篇
  2021年   102篇
  2020年   57篇
  2019年   52篇
  2018年   61篇
  2017年   54篇
  2016年   73篇
  2015年   101篇
  2014年   149篇
  2013年   137篇
  2012年   185篇
  2011年   210篇
  2010年   136篇
  2009年   118篇
  2008年   133篇
  2007年   135篇
  2006年   135篇
  2005年   128篇
  2004年   91篇
  2003年   81篇
  2002年   57篇
  2001年   63篇
  2000年   34篇
  1999年   48篇
  1998年   61篇
  1997年   70篇
  1996年   61篇
  1995年   61篇
  1994年   39篇
  1993年   47篇
  1992年   29篇
  1991年   25篇
  1990年   28篇
  1989年   56篇
  1988年   42篇
  1987年   39篇
  1986年   25篇
  1985年   21篇
  1984年   12篇
  1983年   7篇
  1982年   15篇
  1981年   18篇
  1980年   19篇
  1979年   11篇
  1978年   5篇
  1977年   14篇
  1976年   10篇
  1975年   7篇
排序方式: 共有3159条查询结果,搜索用时 15 毫秒
11.
The nucleocapsid (N) protein of SARS-coronavirus (SARS-CoV) is the key protein for the formation of the helical nucleocapsid during virion assembly. This protein is believed to be more conserved than other proteins of the virus, such as spike and membrane glycoprotein. In this study, the N protein of SARS-CoV was expressed in Escherichia coli DHSalpha and identified with pooled sera from patients in the convalescence phase of SARS. A plasmid pCI-N, encoding the full-length N gene of SARS-CoV, was constructed. Expression of the N protein was observed in COS1 cells following transfection with pCI-N. The immune responses induced by intramuscular immunization with pCI-N were evaluated in a murine model. Serum anti-N immunoglobutins and splenocytes proliferative responses against N protein were observed in immunized BALB/c mice. The major immunoglobulin G subclass recognizing N protein was immunoglobulin G2a, and stimulated splenocytes secreted high levels of gamma interferon and IL-2 in response to N protein. More importantly, the immunized mice produced strong delayed-type hypersensitivity (DTH) and CD^8+ CTL responses to N protein.  相似文献   
12.
Colorectal cancer is a common cancer; generally, adults aged ≥ 50 years are screened using stool occult blood tests and colonoscopy. However, colorectal adenoma and cancer have been found in patients under the aged of 50, and studies on characteristics and risk factors in young patients are lacking. We evaluated the prevalence and risk factors of colorectal adenoma and cancer in young adults aged under 50 years.We retrospectively analyzed 570 individuals aged under 50 years who underwent colonoscopy at the Haeundae Paik Hospital, Korea, from January to June 2018. Logistic regression model was used to identify the risk factors for colorectal adenoma and colorectal cancer.The prevalence of colorectal adenoma in group of 19–29 years was 3.2% (1 of 31), 30–39 years was 13.8% (30 of 217) and in the group of 40–49 years was 21.1% (68 of 322) (P = .009). In multivariable analysis, age over 45 years (adjusted odds ratio [OR], 1.941; 95% confidence interval [CI], 1.187–3.172; P = .008) and male sex (adjusted OR, 1.711; 95% CI, 1.044–2.806; P = .033) were independent risk factors for colorectal neoplasia including cancer.The prevalence of colorectal adenoma increases as the age increased in young adults under 50 years of age, especially after the age of 45 years, the risk of colorectal neoplasia increases; hence, early screening should be considered before the age of 50 years.  相似文献   
13.
BackgroundAs the coronavirus disease 2019 (COVID-19) pandemic continues, there are concerns regarding waning immunity and the emergence of viral variants. The immunogenicity of Ad26.COV2.S against wild-type (WT) and variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) needs to be evaluated.MethodThis prospective cohort study was conducted between June 2021 and January 2022 at two university hospitals in South Korea. Healthy adults who were scheduled to be vaccinated with Ad26.COV2.S were enrolled in this study. The main outcomes included anti-spike (S) IgG antibody and neutralizing antibody responses, S-specific T-cell responses (interferon-γ enzyme-linked immunospot assay), solicited adverse events (AEs), and serious AEs.ResultsFifty participants aged ≥ 19 years were included in the study. Geometric mean titers (GMTs) of anti-S IgG were 0.4 U/mL at baseline, 5.2 ± 3.0 U/mL at 3–4 weeks, 55.7 ± 2.4 U/mL at 5–8 weeks, and 81.3 ± 2.5 U/mL at 10–12 weeks after vaccination. GMTs of 50% neutralizing dilution (ND50) against WT SARS-CoV-2 were 164.6 ± 4.6 at 3-4 weeks, 313.9 ± 3.6 at 5–8 weeks, and 124.4 ± 2.6 at 10–12 weeks after vaccination. As for the S-specific T-cell responses, the median number of spot-forming units/106 peripheral blood mononuclear cell was 25.0 (5.0–29.2) at baseline, 60.0 (23.3–178.3) at 5-8 weeks, and 35.0 (13.3–71.7) at 10–12 weeks after vaccination. Compared to WT SARS-CoV-2, ND50 against Delta and Omicron variants was attenuated by 3.6-fold and 8.2-fold, respectively. The most frequent AE was injection site pain (82%), followed by myalgia (80%), fatigue (70%), and fever (50%). Most AEs were grade 1–2, and resolved within two days.ConclusionSingle-dose Ad26.COV2.S was safe and immunogenic. NAb titer and S-specific T-cell immunity peak at 5–8 weeks and rather decrease at 10–12 weeks after vaccination. Cross-reactive neutralizing activity against the Omicron variant was negligible.  相似文献   
14.
用Boc-和Tos-基团分别保护氨基和侧链胍基,以1%交联度聚苯乙烯二苯甲氨基树脂为载体,用DCC固相法合成肽,HF断裂肽树脂键和去除侧链保护基团,粗产物经高效液相层析纯化,合成了心肌兴奋肽Phe-Met-Arg-Phe-NH_2及其类似物Phe-Pro-Arg-Phe-NH_2,并观察了此二种肽对大鼠血压和心率的影响。  相似文献   
15.
PurposeInterleukin (IL)-17A has been suggested to play a role in the growth and organization of thrombi. We examined whether IL-17A plays a role in the early stages of thrombosis and whether there are sex differences in the effects of IL-17A.Materials and MethodsWe performed a blinded, randomized, placebo-controlled study to compare time to thrombotic occlusion and sex differences therein between mice treated with IL-17A and those treated with saline using a ferric chloride-induced model. We also assessed thrombus histology, blood coagulation, and plasma levels of coagulation factors.ResultsTime to occlusion values did not differ between the IL-17A group and the control group (94.6±86.9 sec vs. 121.0±84.4 sec, p=0.238). However, it was significantly shorter in the IL-17A group of female mice (74.6±57.2 sec vs. 130.0±76.2 sec, p=0.032). In rotational thromboelastometry, the IL-17A group exhibited increased maximum clot firmness (71.3±4.5 mm vs. 66.7±4.7 mm, p=0.038) and greater amplitude at 30 min (69.7±5.2 mm vs. 64.5±5.3 mm, p=0.040) than the control group. In Western blotting, the IL-17A group showed higher levels of coagulation factor XIII (2.2±1.5 vs. 1.0±0.9, p=0.008), monocyte chemoattractant protein-1 (1.6±0.6 vs. 1.0±0.4, p=0.023), and tissue factor (1.5±0.6 vs. 1.0±0.5, p=0.003).ConclusionIL-17A plays a role in the initial st ages of arterial thrombosis in mice. Coagulation factors and monocyte chemoattractant protein-1 may be associated with IL-17A-mediated thrombosis.  相似文献   
16.
To investigate the adverse effects of clozapine on cardiovascular ion channels, we examined the inhibitory effect of clozapine on voltage-dependent K+ (Kv) channels in rabbit coronary arterial smooth muscle cells. Clozapine-induced inhibition of Kv channels occurred in a concentration-dependent manner with an half-inhibitory concentration value of 7.84 ± 4.86 µM and a Hill coefficient of 0.47 ± 0.06. Clozapine did not shift the steady-state activation or inactivation curves, suggesting that it inhibited Kv channels regardless of gating properties. Application of train pulses (1 and 2 Hz) progressively augmented the clozapine-induced inhibition of Kv channels in the presence of the drug. Furthermore, the recovery time constant from inactivation was increased in the presence of clozapine, suggesting that clozapine-induced inhibition of Kv channels is use (state)-dependent. Pretreatment of a Kv1.5 subtype inhibitor decreased the Kv current amplitudes, but additional application of clozapine did not further inhibit the Kv current. Pretreatment with Kv2.1 or Kv7 subtype inhibitors partially blocked the inhibitory effect of clozapine. Based on these results, we conclude that clozapine inhibits arterial Kv channels in a concentration- and use (state)-dependent manner. Kv1.5 is the major subtype involved in clozapine-induced inhibition of Kv channels, and Kv2.1 and Kv7 subtypes are partially involved.  相似文献   
17.
In this article, we report the effect of a Li6.75La3Zr2Al0.25O12 (LLZAO) composite Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode material on the performance of all-solid-state batteries (ASSBs) with oxide-based organic/inorganic hybrid solid electrolytes. The layered structure of Ni-rich cathode material Li(NixCo(1−x)/2Mn(1−x)/2)O2 (x > 0.6) (NCM) exhibiting a high specific capacity is among the suitable cathode materials for next-generation energy storage systems, particularly electric vehicles and portable devices for all-solid-state batteries. However, the ASSBs present a problem—the resistance at the interface between a cathode and solid electrolyte is larger than that with a liquid electrolyte because of point contact. To solve this problem, using a simultaneous co-precipitation method, we composited various amounts of LLZAO material and an ion conducting material on the cathode material''s surface. Therefore, to optimize the value of the LLZAO material in the composite cathode material, the structure, cycling stability, and rate performance of the NCM–LLZAO composite cathode material in ASSBs with oxide-based inorganic/organic-hybrid electrolytes were investigated using powder X-ray diffraction analysis, field-emission scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic measurements.

A composite cathode material contributes to the improvement of interfacial resistance between cathode material and solid electrolyte in the all-solid-state batteries.  相似文献   
18.

Background  

Inverted nipples are associated with aesthetic, functional, and psychological problems. In moderate to severe cases, triangular areolar dermal flap-based methods can effectively correct the condition. A triangular areolar dermal flap supports the nipple base as a result of a hammock-like action and fills the dead space beneath the nipple. However, these flaps leave visible scars on or deform the areola.  相似文献   
19.
20.

Background:

The treatment of pressure sores represents a significant challenge to health care professionals. Although, pressure wound management demands a multidisciplinary approach, soft tissue defects requiring reconstruction are often considered for surgical management. Myocutaneous and fasciocutaneous flaps can provide stable coverage of pressure sores.

Purpose:

Here, we describe our experience using a recent fasciocutaneous flap, which is named ‘reading man’ flap, in sacral, ischial, and trochanteric pressure sores.

Materials and Methods:

During a period of 1 year the authors operated 16 patients, 11 men, and 5 women, using the reading man flap. The ages of the patients ranged from 24 to 78 years. The location of pressure sores was 8 sacral, 5 ischial, and 3 trochanteric pressure sores. The mean size of pressure sores was 8 cm × 9 cm.

Results:

All pressure sores covered bt the Reading Man flap healed asymptomatically. After follow-up of 2-8 months, no recurrences were encountered and no further surgical intervention was required.

Conclusion:

The reading man flap was found to be a useful technique for the closure of pressure sore in different anatomic locations. The advantage of tension-free closure and the minimal additional healthy skin excision made this flap a useful tool in pressure sore reconstructions.KEY WORDS: Local flap, pressure sore, ‘reading man’ flap  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