全文获取类型
收费全文 | 18573篇 |
免费 | 2113篇 |
国内免费 | 774篇 |
专业分类
耳鼻咽喉 | 107篇 |
儿科学 | 310篇 |
妇产科学 | 274篇 |
基础医学 | 1850篇 |
口腔科学 | 555篇 |
临床医学 | 1655篇 |
内科学 | 2856篇 |
皮肤病学 | 105篇 |
神经病学 | 1041篇 |
特种医学 | 800篇 |
外国民族医学 | 6篇 |
外科学 | 4134篇 |
综合类 | 2752篇 |
现状与发展 | 3篇 |
预防医学 | 1684篇 |
眼科学 | 428篇 |
药学 | 1295篇 |
3篇 | |
中国医学 | 659篇 |
肿瘤学 | 943篇 |
出版年
2024年 | 36篇 |
2023年 | 249篇 |
2022年 | 591篇 |
2021年 | 733篇 |
2020年 | 647篇 |
2019年 | 643篇 |
2018年 | 625篇 |
2017年 | 533篇 |
2016年 | 527篇 |
2015年 | 563篇 |
2014年 | 1081篇 |
2013年 | 1231篇 |
2012年 | 1002篇 |
2011年 | 1118篇 |
2010年 | 921篇 |
2009年 | 1013篇 |
2008年 | 1023篇 |
2007年 | 1041篇 |
2006年 | 966篇 |
2005年 | 983篇 |
2004年 | 842篇 |
2003年 | 723篇 |
2002年 | 617篇 |
2001年 | 535篇 |
2000年 | 483篇 |
1999年 | 396篇 |
1998年 | 301篇 |
1997年 | 296篇 |
1996年 | 244篇 |
1995年 | 213篇 |
1994年 | 158篇 |
1993年 | 149篇 |
1992年 | 132篇 |
1991年 | 105篇 |
1990年 | 86篇 |
1989年 | 53篇 |
1988年 | 62篇 |
1987年 | 53篇 |
1986年 | 40篇 |
1985年 | 76篇 |
1984年 | 66篇 |
1983年 | 63篇 |
1982年 | 49篇 |
1981年 | 54篇 |
1980年 | 45篇 |
1979年 | 24篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
141.
Rieko Matsuura Takumi Takeuchi Atsumi Yoshida 《Asian journal of andrology》2010,12(5):753-759
Appropriate semen processing and assessment are critical for successful infertility treatment. We investigated whether laboratory procedures including semen preparation and incubation affect sperm DNA integrity. A total of 153 infertile men were involved. Conventional semen parameters and sperm chromatin structure assay (SCSA) parameters, that is, DNA fragmentation index (%DFI) and high DNA stainability (%HDS), were assessed on the flesh ejaculated semen samples, which were treated and incubated under different conditions. Negative correlations were identified between the %DFI and sperm concentration, motility, progressive motility and morphology. A lower percentage of DFI was detected in spermatozoa when density gradient centrifugation (DGC) was followed by swimup treatment in comparison with DGC alone (P 〈 0.01). Although the %DFI increased in a time-dependent manner with incubation both at room temperature (RT) and at 37℃ in air, the %DFI after 24 h at RT was significantly lower than that at 37℃ (P 〈 0.05). Incubation with 5% CO2 was effective in maintaining sperm motility (P 〈 0.01); however, it induced further elevation of %DFI (P 〈 0.001). Thus, sperm DNA damage was associated with longer incubation periods. Interestingly, common culture conditions, such as maintaining pH and temperature, compromised the sperm DNA integrity. 相似文献
142.
目的探讨胰腺癌的胰实质期CT增强与病理分级、瘤体实质细胞处的微血管密度(microvessel den-sity,MVD)、血管内皮生长因子(vascular endothelial growth factor,VEGF)表达的相关性。方法选择经手术切除的胰腺癌患者30例,手术前均行CT增强扫描,观察胰腺癌胰实质期强化程度和形式;并对其手术标本行HE染色和免疫组化标记,对胰腺癌的CT强化状况、病理级别、瘤体实质细胞处的MVD和VEGF的表达行相关性分析。结果胰腺癌CT胰实质期瘤体强化程度、形式和其恶性度高低呈显著负相关(r=0.733,t=5.708,P0.001),和瘤体实质细胞处MVD计数显著负相关(r=0.778,t=6.551,P0.001);胰腺癌的病理分级和瘤体实质细胞处MVD计数正相关(r=0.437,t=7.574,P0.05),而与VEGF表达无关(r=-0.240,t=-1.306,P0.05)。VEGF阳性表达组MVD为57.7±11.1,VEGF阴性表达组MVD为44.6±12.2,两者差异有统计学意义(t=3.018,P0.05)。结论胰腺癌CT胰实质期增强程度高低能反映肿瘤的恶性程度及瘤体实质细胞处MVD计数。胰腺癌的恶性度高低、VEGF表达均与MVD计数密切相关。 相似文献
143.
Osteoporosis in men is recognised worldwide as an important and increasing public health problem. The causes are more heterogeneous than those in women. About 50% are diagnosed as secondary cases. In some secondary forms of osteoporosis the specific diagnosis results in additional therapeutic options (e.g. androgen therapy in proven hypogonadism). The basic therapy for osteoporosis in men is no different to that in postmenopausal women, namely recommendations for counteracting modifiable risk factors, especially with regard to diet, physical exercise, and calcium and vitamin D supplementation. Concerning specific drug medications, however, even today there is still a therapeutic dilemma in male osteoporosis. While older substances (e.g. calcitonin, fluoride, alfacalcidol) are approved for both sexes, all newer medications have primarily been approved for the treatment of postmenopausal osteoporosis. Health authorities request studies in purely male populations. For new drugs, fracture data are necessary while for new substances within a class (e.g. bisphosphonates), at the very least consistent effects on bone mineral density (BMD) and bone turnover markers are requested. Due to these regulatory rules, ibandronate, teriparatide and strontium ranelate are not approved in the European Union. Some years ago, alendronate was the first bisphosphonate that was approved for the treatment of men with osteoporosis, based on consistent results from two independent male studies using a daily 10 mg dosage. Very recently risedronate was approved by the FDA and EMEA. A randomised, placebo-controlled multicentre trial of 285 male patients showed, after 2 years, a 5.8% increase in lumbar spine BMD in the risedronate 35 mg once weekly group vs 1.2% in the placebo group. In a prospective controlled study on 316 men with primary or secondary osteoporosis we found, after 12 months, a lumbar spine BMD of +4.7% vs +1.0% in controls. The number of patients with one or more new vertebral fractures was 8 in the risedronate group and 20 in the placebo group (a fracture reduction of 60%). Furthermore, we found a significantly smaller decrease in height and a steeper decrease in back pain in the risedronate group. Risedronate is the first oral bisphosphonate available for men with the more comfortable once weekly dosage. 相似文献
144.
目的探讨体重、体重指数(BMI)等体成分指标对中老年健身运动女性骨密度的影响及体成分指标与骨代谢指标、骨密度指标的关系。方法94例成都市城区健身运动女性根据BMI不同分为三组:低体重组(BMI≤20kg/m2)、正常体重组(20kg/m225kg/m2),采用Osteospace超声骨密度仪测定跟骨的BUA、SOS、STI骨密度指标;全自动生化分析仪测定血清AKP含量;应用放射免疫法测定血清hCT、BGP、IL-6、E2、TNF含量。应用方差分析和偏相关方法进行统计学处理。结果不同BMI组的体重、体重指数、瘦体重和体脂百分比差异显著,低体重组T-score与正常体重组、超重组比较有极显著差异;低体重组SOS、STI骨密度指标显著低于正常体重组;BUA、SOS、STI骨密度指标与体重、体重指数、瘦体重和体脂百分比呈正相关,与hCT、IL-6、TNF、BGP、AKP呈正相关,与E2呈负相关。低体重组骨量减少、骨质疏松发生率最高。结论体重、体重指数等体成分指标是影响中老年健身运动女性BMD的重要因素,保持体重有利于防止骨丢失和预防骨质疏松发生。 相似文献
145.
降钙素对卵巢切除大鼠股骨骨折愈合的影响 总被引:1,自引:0,他引:1
目的观察降钙素对卵巢切除大鼠股骨骨折愈合的作用,为临床上治疗骨质疏松性骨折提供实验依据。方法50只雌性、14周龄SD大鼠共分成5组,每组10只。分成假手术组(Sham,G1),双侧卵巢切除术组(OVX,G2),假手术+骨折组(Sham+F,G3),卵巢切除术+骨折组(OVX+F,G4),卵巢切除+骨折+降钙素药物组(OVX+F+CT,G5),骨折组大鼠均采用右股骨中段横行骨折,髓内针固定;降钙素采用皮下给药,隔日1次(16IU·kg^-1)。所有大鼠于术后4周杀死,取右侧股骨标本。然后,分别进行CR摄片、组织形态学观察,并应用双能X线骨密度仪(DEXA)测量右股骨整体、远段和中段骨密度以及BMP-2免疫组化观察,并应用病理图像分析仪对BMP-2免疫组化进行光密度测量。结果(1)OVX组与Sham组比较,BMD显著下降。(2)OVX+F+CT组与OVX+F组比较:骨痂mBMD显著增高;BMP-2的表达无显著性差异。结论降钙素对OVX大鼠股骨骨折具有明显促进骨折愈合的作用,加速编织骨向板层骨的演变过程。 相似文献
146.
目的 探讨中国人过氧化物酶体增殖物激活受体γ(PPARγ)基因外显子6 C161T多态性与糖皮质激素性骨质疏松症(GIO)的相关关系。方法 应用聚合酶链反应-限制性片段长度多态性(PCR-RELP)方法测定208例正常健康人(Ⅰ组)、168例非GIO患者(Ⅱ组)和104例GIO患者(Ⅲ组)PPARγ基因外显子6 C161T的基因型。应用双能X线骨密度仪(DEXA)测定股骨、腰椎等部位的骨密度。 结果 外显子6 C161T有CC、CT、TT 3种基因型。GIO组CC基因型频率显著低于正常对照组;CT和TT基因型频率显著高于正常对照组。非GIO组、应用激素组(GIO组+非GIO组)与正常对照组比较,各基因型频率差异均无统计学意义。正常对照组C161T的CC基因型组各部位的骨密度有高于CT和TT基因型组的趋势,但差异无统计学意义。非GIO组和GIO组C161T的CC基因型组腰椎的骨密度明显高于CT和TT基因型组 (P < 0.05),分别为非GIO组CC型(1.04±0.17) g/cm2,CT+TT型(1.02±0.07) g/cm2;GIO组CC型(0.94±0.12) g/cm2,CT+TT型(0.83±0.08) g/cm2。经年龄、体重指数等因素校正后,差异仍有统计学意义(P < 0.05)。 结论 PPARγ基因C161T基因型在正常人和应用激素患者之间无明显差异,它可能与肾小球肾炎的发病无关。C161T基因型在GIO组和正常对照组之间差异有统计学意义,它可能与糖皮质激素性骨质疏松症的发病有关。PPARγ基因C161T多态性与应用糖皮质激素患者腰椎的骨密度有关。等位基因C可能是骨量的保护因子,它可能与应用糖皮质激素后骨量的丢失有关。 相似文献
147.
A. M. Valdes J. B. Richards J. P. Gardner R. Swaminathan M. Kimura L. Xiaobin A. Aviv T. D. Spector 《Osteoporosis international》2007,18(9):1203-1210
Summary Telomere length decreases with age and is associated with osteoblast senescence. In 2,150 unselected women, leukocyte telomere
length was significantly correlated with bone mineral density. Clinical osteoporosis was associated with shorter telomeres,
suggesting that telomere length can be used as a marker of bone aging.
Introduction The length of telomeres in proliferative cells diminishes with age. Telomere shortening and telomerase activity have been
linked to in vitro osteoblast senescence and to increased secretion of pro-inflammatory cytokines. We explored whether bone
mineral density correlates with telomere length in leukocytes.
Materials and methods The relationship between leukocyte telomere length, bone mineral density (BMD) and osteoporosis (as defined by the World Health
Organization) was examined in a cohort of 2,150 women from a population-based twin cohort aged 18–79.
Results After adjusting for age, body mass index, menopausal status, smoking, hormone replacement therapy status, telomere length
was positively correlated with BMD of the spine (p < 0.005), forearm (p < 0.013), but not the femoral neck (p < 0.06). Longer
telomeres were associated with reduced the risk of clinical OP at two or more sites (odds ratio = 0.594 95% CI 0.42–0.84 p < 0.003)
and in women over the age of 50, clinical osteoporosis was associated with 117 bp shorter telomere length (p < 0.02) equivalent
to 5.2 years of telomeric aging.
Conclusions Shortened leukocyte telomere length is independently associated with a decrease in BMD and the presence of osteoporosis in
women. Our data provide evidence that leukocyte telomere length could be a marker of biological aging of bone. 相似文献
148.
Relative contribution of body composition to bone mineral density at different sites in men and women of South Korea 总被引:4,自引:0,他引:4
Cui LH Shin MH Kweon SS Park KS Lee YH Chung EK Nam HS Choi JS 《Journal of bone and mineral metabolism》2007,25(3):165-171
We examined the relative contribution of body composition to bone mineral density (BMD) at various sites in 1406 Korean rural
men and women, aged 19–80 years, from July to August 2004. The BMD was measured at peripheral (distal forearm and calcaneus)
and central (lumbar spine at L1–L4, femoral neck, trochanter, and Ward's triangle) using dual-energy X-ray absorptiometry.
In multivariate analyses, the linear regression models were adjusted for relevant covariates. In premenopausal women, only
lean mass had a significant positive correlation with BMD at all sites. In postmenopausal women, fat mass was significantly
positively correlated with BMD at all sites, except the Ward's triangle; fat mass was the only determinant of BMD at the lumbar,
distal forearm, and calcaneus sites, whereas both lean and fat mass contributed to BMD at the hip, with the effect of lean
mass being slightly greater than that of fat mass. In younger men, lean mass had a significant positive contribution to BMD
at all sites, whereas fat mass appeared to contribute negatively to BMD at all sites, except the calcaneus. In older men,
lean mass made a significant positive contribution to the BMD at all sites; fat mass also made a significant positive contribution
to the BMD at the forearm and calcaneus. These data indicate that in the Korean rural population, lean mass may be an important
determinant of the BMD, whereas fat mass may contribute positively to BMD only in postmenopausal women and older men. 相似文献
149.
Summary The prevalence of osteoporosis was statistically significantly higher among female Holocaust survivors than among those who
were not exposed to the Holocaust. These findings support the importance of nutrition and environmental conditions during
childhood and adolescence on BMD in older adults.
Introduction Holocaust survivors during childhood and adolescence experienced undernutrition and lack of exercise and sunlight. The study
aimed to establish if Holocaust survivors have higher prevalence of osteoporosis than subjects who were not Holocaust survivors.
Methods Seventy-three female Jewish Holocaust survivors ≥ 60 years old and 60 female European-born Jews ≥60 years old who were not
in the Holocaust were examined. BMD was measured using DXA of the lumbar spine and hips. The Cochran-Armitage trend test was
used to test for an increasing trend in decreased BMD in the Holocaust survivors versus controls.
Results Among Holocaust survivors 54.8% had osteoporosis, 39.7% osteopenia, and 5.5% normal BMD, whereas among controls 25.0% had
osteoporosis, 55.0% osteopenia, and 20.0% normal BMD (p = 0.0001). In those who were <17 years old in 1945, among Holocaust survivors 58.0% had osteoporosis, 34.0% osteopenia, and
8.0% normal BMD, whereas among controls 20.0% had osteoporosis, 57.8% osteopenia, and 22.2% normal BMD (p = 0.0003). In those ≥17 years old in 1945, among Holocaust survivors 47.8% had osteoporosis, 52.2% osteopenia and none had
normal BMD, whereas among controls 40.0% had osteoporosis, 46.7% osteopenia, and 13.3% normal BMD (p = 0.28).
Conclusion The prevalence of osteoporosis was significantly higher among Holocaust survivors. 相似文献
150.
Konrad Seller Dieter Wahl Alexander Wild Rüdiger Krauspe Erich Schneider Berend Linke 《European spine journal》2007,16(7):1047-1054
A lot of new implant devices for spine surgery are coming onto the market, in which vertebral screws play a fundamental role.
The new screws developed for surgery of spine deformities have to be compared to established systems. A biomechanical in vitro
study was designed to assess the bone–screw interface fixation strength of seven different screws used for correction of scoliosis
in spine surgery. The objectives of the current study were twofold: (1) to evaluate the initial strength at the bone–screw
interface of newly developed vertebral screws (Universal Spine System II) compared to established systems (product comparison)
and (2) to evaluate the influence of screw design, screw diameter, screw length and bone mineral density on pullout strength.
Fifty-six calf vertebral bodies were instrumented with seven different screws (USS II anterior 8.0 mm, USS II posterior 6.2 mm,
KASS 6.25 mm, USS II anterior 6.2 mm, USS II posterior 5.2 mm, USS 6.0 mm, USS 5.0 mm). Bone mineral density (BMD) was determined
by quantitative computed tomography (QCT). Failure in axial pullout was tested using a displacement-controlled universal test
machine. USS II anterior 8.0 mm showed higher pullout strength than all other screws. The difference constituted a tendency
(P = 0.108) when compared to USS II posterior 6.2 mm (+19%) and was significant in comparison to the other screws (+30 to +55%,
P < 0.002). USS II posterior 6.2 mm showed significantly higher pullout strength than USS 5.0 mm (+30%, P = 0.014). The other screws did not differ significantly in pullout strength. Pullout strength correlated significantly with
BMD (P = 0.0015) and vertebral body width/screw length (P < 0.001). The newly developed screws for spine surgery (USS II) show higher pullout strength when compared to established
systems. Screw design had no significant influence on pullout force in vertebral body screws, but outer diameter of the screw,
screw length and BMD are good predictors of pullout resistance. 相似文献