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   7017篇
  免费   356篇
  国内免费   216篇
耳鼻咽喉   32篇
儿科学   162篇
妇产科学   105篇
基础医学   949篇
口腔科学   111篇
临床医学   588篇
内科学   790篇
皮肤病学   106篇
神经病学   773篇
特种医学   89篇
外科学   760篇
综合类   754篇
现状与发展   1篇
预防医学   332篇
眼科学   34篇
药学   1241篇
中国医学   388篇
肿瘤学   374篇
  2024年   10篇
  2023年   90篇
  2022年   134篇
  2021年   200篇
  2020年   213篇
  2019年   197篇
  2018年   214篇
  2017年   215篇
  2016年   182篇
  2015年   194篇
  2014年   420篇
  2013年   478篇
  2012年   378篇
  2011年   430篇
  2010年   343篇
  2009年   369篇
  2008年   353篇
  2007年   358篇
  2006年   303篇
  2005年   282篇
  2004年   227篇
  2003年   187篇
  2002年   177篇
  2001年   135篇
  2000年   126篇
  1999年   85篇
  1998年   105篇
  1997年   94篇
  1996年   72篇
  1995年   89篇
  1994年   65篇
  1993年   38篇
  1992年   37篇
  1991年   47篇
  1990年   48篇
  1989年   30篇
  1988年   36篇
  1987年   33篇
  1986年   38篇
  1985年   77篇
  1984年   54篇
  1983年   66篇
  1982年   72篇
  1981年   58篇
  1980年   59篇
  1979年   54篇
  1978年   36篇
  1977年   28篇
  1976年   23篇
  1975年   12篇
排序方式: 共有7589条查询结果,搜索用时 31 毫秒
1.
肛直肠抑制反射时门静脉血中P物质变化   总被引:1,自引:0,他引:1  
目的探讨肛直肠抑制反射(RAIR)时门静脉血中P物质(SP)的变化规律及外源性内脏神经对其变化的影响。方法将实验大白鼠分为7组,其中6组先按去与不去直肠肛管外源性内脏神经支配而分为不去神经和去神经两大组,每组中又按Foley导管上气囊置入直肠腔中的位置分为2、4、6cm组;同时再设1个对照组,将Foley导管置入直肠腔中,但不注水扩张球囊。检测并比较在直肠腔内刺激后,各组门静脉血中的SP值及变化情况。结果去神经组中2、4cm组与不去神经组之间及对照组之间,门静脉血中SP值变化比较,P〉0.05,差异无统计学意义。不去神经组中的6cm组与对照组及去神经组中2cm和4cm组之间SP值比较,P〈0.01,差异有统计学意义;去神经组和不去神经组中的6cm组之间SP值比较,P〈0.01,差异有统计学意义。结论直肠腔内上部的刺激不引出RAIR可能与该部位的刺激使内括约肌兴奋性递质(SP)的释放有关;外源性内脏神经对RAIR中门静脉血的SP变化有调控作用。  相似文献   
2.
目的 :探讨联合菌苗防治肿瘤的作用。方法采用动物体内实验 ,动物为封闭群KM小鼠 ,菌株为 2 6 0 0 3- 2 1、4 482 4 - 3及 932 0 1- 3,瘤种为S180 。所有实验小鼠接种S180 后 ,按随机对照试验设计分成 5组 ,即三个不同的单价菌苗组、一个联合菌苗组及一个对照组 ,同期观察联合菌苗对S180 增长的影响。结果 :三个不同的单价菌苗组及联合菌苗组的平均瘤重均比对照组低 ,联合菌苗组的平均瘤重比单价菌苗组的更低 ,差异均有高度统计学意义 (P <0 .0 1~ 0 .0 0 1) ;三个不同单价菌苗组的抑瘤率分别为 5 0 .6 %、4 8.3%、4 5 .5 % ,联合菌苗组抑瘤率为 75 .0 %。结论 :实验所选用的菌苗能抑制S180 的增长 ,联合菌苗的效果更好  相似文献   
3.
目的 评价单克隆IgH基因重排检测在恶性淋巴瘤 (B NHL)临床中的应用价值。方法 用半巢式PCR检测单克隆IgH基因重排。病例组为B NHL ,包括 6 9例石蜡包埋组织切片、治疗前 16例骨髓和 2 9例外周血、阳性者治疗后复查骨髓和外周血 ;对照组为 10例慢性淋巴结炎、3例T NHL和 2例HD。结果 对照组均阴性。病例组 :切片中单克隆IgH基因重排阳性率为 6 3.8% (44 / 6 9) ;骨髓和外周血阳性率分别为 43 .8%(7/ 16 )和 41.4% (12 / 2 9) ,细胞形态学检查未见异常细胞者阳性率分别为 33 .3% (3/ 9)和 31.3% (5 / 16 )。 16例同时采集骨髓和外周血者 ,阳性率分别为 43 .8% (7/ 16 )和 37.5 % (6 / 16 ) ,两者无统计学差异。治疗前单克隆IgH重排阳性者 ,6例完全缓解 (CR)后转阴 ,处于持续缓解状态 ,1例临床缓解后 13个月仍阳性 ,现在继续随访中 ,另 1例CR后持续阳性者 ,6个月后复发。结论 切片、骨髓和外周血中检测单克隆IgH基因重排可以作为B NHL诊断和随访微小残留病灶的辅助手段  相似文献   
4.
Osteoclastogenesis inhibitory factor (OCIF) is a novel secreted protein that inhibits osteoclastogenesis both in vitro and in vivo. In this study, we examined the effects of OCIF on serum calcium (Ca) concentrations in normal mice and in hypercalcemic nude mice carrying tumors associated with humoral hypercalcemia of malignancy. In normal mice, a single intraperitoneal injection of OCIF reduced serum Ca levels in a dose-dependent manner. Significant decrease in serum Ca (by 1.6 ± 0.3 mg/dL, n = 5) was observed 2 h after the injection of OCIF at 20 mg/kg and the hypocalcemic effect continued for up to 12 h. Serum phosphate (Pi) concentrations also decreased in response to OCIF. Urinary excretion of Ca, Pi, and creatinine did not change significantly after injection of OCIF or vehicle. In hypercalcemic, tumor-bearing nude mice, a single intraperitoneal injection of OCIF at 20 mg/kg resulted in a dramatic decrease in serum Ca (maximal decrease 2.8 ± 0.37 mg/dL, n = 11), which continued for up to 24 h. The results suggest that OCIF decreased serum Ca through its inhibitory effect on bone resorption. Furthermore, it is suggested that OCIF has therapeutic potential for the treatment of hypercalcemic conditions such as malignancy-associated hypercalcemia.  相似文献   
5.
These experiments examined the effects, on retention, of posttraining intra-amygdala administration of norepinephrine (NE), and propranolol. Rats were trained on a one-trial step-through inhibitory avoidance task and tested for retention 24 h later. Injections were administered bilaterally (1.0 microliter/injection) through chronically-implanted cannulae. Low doses of NE (0.1 or 0.3 microgram) administered shortly after training enhanced retention while higher doses (1.0 or 5.0 micrograms) were ineffective. Retention was not affected by NE administered 3 h after training. The effect of intra-amygdala NE on retention is blocked by simultaneous administration of propranolol (0.2 microgram). This finding suggests that the memory-enhancing effect of NE may be mediated by beta-receptors. Posttraining intra-amygdala NE also attenuated the retention deficit produced by adrenal demedullation. Further, intra-amygdala injections of propranolol (0.2 microgram) blocked the enhancing effect, on retention, of posttraining s.c. injections of epinephrine. These findings suggest that activation of noradrenergic receptors in the amygdala may be involved in memory processing and may play a role in the memory-modulating effect of peripheral epinephrine.  相似文献   
6.
This paper outlines the impact of granulocyte‐colony stimulating factor (G‐CSF) used as a single modality therapy in 17 patients with secondary autoimmune neutropenia (S‐AIN) who had been treated a multiple number of times previously. Fifteen of these patients had demonstrable antineutrophil antibodies and two had cellular S‐AIN with haemopoietic inhibitory T‐cells present in the marrow. Prior to treatment, all had had problems with infection. All patients responded within 7 days of commencement of treatment. Provided G‐CSF neutrophil counts were maintained above 1 × 109/l, no further infections occurred. This was achievable by using G‐CSF administered as infrequently as once every 8 days. Eight of the 17 patients remained on G‐CSF, although five switched to the glycosylated form because of side‐effects. None have developed osteoporosis despite 47.29 patient years of total experience with G‐CSF. In conclusion both glycosylated and nonglycosylated G‐CSF can be used effectively in treating AIN on a long‐term basis.  相似文献   
7.

Objectives

For individuals not on antiretroviral therapy, the risk of heterosexual transmission of HIV appears negligible when blood plasma (BP) viral loads are <1500 HIV‐1 RNA copies/mL. It is not clear whether this observation can be extrapolated to individuals on highly active antiretroviral therapy (HAART). Because of differential tissue penetration, antiretroviral drug concentrations may be sufficient to maintain an undetectable viral load in the BP yet not achieve adequate levels to suppress HIV in the genital tract. Therefore, we wanted to correlate HIV viral loads and drug concentrations in semen plasma (SP) and BP.

Methods

Thirty‐three men were included. All were on combination antiretroviral therapy with an undetectable BP viral load for at least 1 year. Blood and semen samples were collected within 2 h of each other and tested for HIV RNA by the NucliSens QT (bioMerieux, St Laurent, QC, Canada) method; drug concentrations were determined by liquid chromatography tandem mass spectrometry.

Results

Two of the 33 patients (6.1%) with BP viral loads below detection had time‐matched HIV viral loads in SP ≥700 copies/mL. Both patients were on efavirenz, the SP concentrations of which were ≤10% of the levels in BP and well below the minimal therapeutic drug monitoring target concentration required to suppress HIV.

Conclusions

Because, at least in part, of poor drug penetration into the genital tract, an undetectable HIV viral load in the BP does not guarantee an undetectable viral load in semen. In view of this, caution should be taken in concluding that patients on HAART with suppressed viraemia are sexually non‐infectious.  相似文献   
8.
目的:探讨P物质抑制剂-辣椒素及bFGF抗体单独或联合使用对体外培养的人体增生性瘢痕成纤维细胞增殖的影响。方法:体外培养12例增生性瘢痕组织的成纤维细胞,分别加入不同浓度的辣椒素或/和bFGF抗体,培养24h后观察细胞形态学变化,并用MTT法检测细胞增殖抑制率。结果:所有不同浓度的辣椒素(2.5,5,20,40,60,80mg/L)均能使细胞皱缩、坏死,抑制细胞增殖,其抑制作用随剂量增大而增加。中高浓度bFGF抗体(40,80mg/L)也可促使细胞皱缩、坏死,抑制细胞增殖,其抑制作用也随剂量增大而增加。辣椒素与bFGF抗体联合应用对成纤维细胞抑制作用较单独使用效果更显著(P﹤0.05)。结论:辣椒素及bFGF抗体可抑制增生性瘢痕成纤维细胞增殖,其抑制作用随浓度增加而增加,两者联合使用有协调作用,本研究结果可能在增生性瘢痕的治疗提供新的思路和手段。  相似文献   
9.
蜂王浆冻干粉对小鼠肿瘤的抑制作用   总被引:4,自引:0,他引:4  
目的研究蜂王浆冻干粉对小鼠肿瘤的抑制作用.方法按每公斤体重0g、0.25g、0.50g、0.75g设对照及低、中、高3个剂量组,经口给予蜂王浆冻干粉30d后,接种小鼠肉瘤180(S180)和艾氏癌腹水型(EAC)两个瘤种.结果在两次重复的小鼠S180和EAC抑瘤试验中发现中剂量组瘤重明显低于阴性对照组(P<0.05),抑制率可达34%;中剂量组荷瘤小鼠平均生存时间均明显高于对照组(P<0.05).结论蜂王浆冻干粉具有抑制肿瘤的作用.  相似文献   
10.
探讨老年人微小病变性(MC)特发性肾病综合征(PNS)的临床特征及预后。方法 观察成人MC性PNS118例,其中老年患者18例,占15.2%。结果 发现老年患者NS的临床表现与成年组相似;但血尿发病率较低,22%比38%;高血压和肾功能不全的发病率明显增高,38.9%比16%和33.3%比19%(P<0.01)。老年组对激素治疗的敏感性略差;但NS复发率明显减少,11.1%比43%。结论 尽管NS的复发和对激素依赖使治疗有一定困难,但激素、细胞毒性药物和环孢素A对于消除蛋白尿,延缓肾功能不全是有助的。  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