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   43806篇
  免费   4535篇
  国内免费   2876篇
耳鼻咽喉   317篇
儿科学   566篇
妇产科学   515篇
基础医学   4952篇
口腔科学   895篇
临床医学   5774篇
内科学   6236篇
皮肤病学   457篇
神经病学   1888篇
特种医学   1536篇
外国民族医学   17篇
外科学   4438篇
综合类   7760篇
现状与发展   12篇
一般理论   15篇
预防医学   3446篇
眼科学   1362篇
药学   4373篇
  57篇
中国医学   2759篇
肿瘤学   3842篇
  2024年   165篇
  2023年   776篇
  2022年   1850篇
  2021年   2427篇
  2020年   1813篇
  2019年   1524篇
  2018年   1560篇
  2017年   1465篇
  2016年   1355篇
  2015年   2056篇
  2014年   2580篇
  2013年   2475篇
  2012年   3495篇
  2011年   3838篇
  2010年   2581篇
  2009年   2142篇
  2008年   2501篇
  2007年   2434篇
  2006年   2410篇
  2005年   2016篇
  2004年   1430篇
  2003年   1225篇
  2002年   988篇
  2001年   862篇
  2000年   819篇
  1999年   820篇
  1998年   521篇
  1997年   478篇
  1996年   368篇
  1995年   321篇
  1994年   325篇
  1993年   186篇
  1992年   236篇
  1991年   188篇
  1990年   152篇
  1989年   195篇
  1988年   133篇
  1987年   137篇
  1986年   63篇
  1985年   71篇
  1984年   46篇
  1983年   30篇
  1982年   26篇
  1981年   26篇
  1980年   19篇
  1979年   26篇
  1978年   11篇
  1977年   5篇
  1975年   9篇
  1974年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
我国人体首次发现圆圃棘口吸虫病例及虫体形态观察   总被引:4,自引:0,他引:4  
1988年7月6日,我们在一患者便内发现似姜片虫卵的大型虫卵。临床表现为头昏无力、食欲不振,上腹痛和贫血。因病人20天前有吞食活泥鳅史,故疑其为棘口吸虫病。服药后获虫体70条,经形态学研究,鉴定为圆圃棘口吸虫(Echinostoma hortense Asada,1926)。  相似文献   
122.
A prospective randomised clinical trial was conducted to examine the efficacy of 2 weeks pre-operative parenteral nutrition (PPN) for the prevention of complications following surgery for oesophageal cancer. Forty patients were studied, the diet of twenty being supplemented by pre-operative parenteral nutrition. There were no significant differences in age, nutritional status, tumour staging and histology between the two groups of patients. The use of PPN resulted in a significant gain in body weight and nitrogen but failed to produce an overall reduction in post-operative morbidity and mortality rates. However patients receiving PPN exhibited two types of changes in serum albumin levels. Those with a fall in serum albumin levels associated with an increase in body weight (indicating an expansion of extracellular volume) had a significantly higher incidence of post-operative pulmonary complications than the group exhibiting a rise in serum albumin levels concomitant with increase in body weight. These data suggested that two weeks PPN might not be adequate in certain patients and a longer period of PPN is required. They also show no clinical benefit from the routine use of pre-operative parenteral nutrition in all patients, but do not exclude benefit in selected groups.  相似文献   
123.
Mosaicism for an FMR1 gene deletion in a fragile X female   总被引:2,自引:0,他引:2  
Most cases of fragile X syndrome result from expansion of CGG repeats in the FMR1 gene; deletions and point mutations of FMR1 are much less common. Mosaicism for an FMR1 full mutation with a deletion or with a normal allele has been reported in fragile X males. Here we report on a fragile X female who is mosaic for an FMR1 full mutation and an intragenic deletion. The patient is a 4-year-old girl with developmental delay, autistic-like behaviors, and significant speech and language abnormalities. Southern blotting demonstrated the presence of a methylated full mutation, a normal allele in methylated and unmethylated forms, and an additional fragment smaller than the normal methylated allele. This result indicates that the patient is mosaic for a full mutation and a deletion, in the presence of a normal allele. By DNA sequence analysis, we mapped the 5' breakpoint 63/65 bp upstream from the CGG repeat region and the 3' breakpoint 86/88 bp downstream of the CGG repeats within the FMR1 gene. The deletion removed 210 bp, including the entire CGG repeat region. The full mutation was inherited from a premutation in the patient's mother. The deletion, which remained methylated at the Eag I and Nru I sites, was probably derived from the full mutation allele. Mosaicism of this type is rare in females with a fragile X mutation but should be kept in mind in the interpretation of Southern blots.  相似文献   
124.
PROBLEM and METHOD: Early pregnancy factor (EPF), an Immunosuppressive substance, which appears in pregnant women's sera 48 h after fertilization, is a kind of pregnancy-specific protein. To determine whether the EPF activity could be a super early indicator of pregnancy, we used rosette inhibition assay to detect EPF activity in the sera, collected from 70 women 2–7 days after ovulation intending to conceive monitored by ultrasonography. Simultaneously we selected 40 non-pregnant sera and 12 early-pregnant sera as negative control and positive control, respectively. RESULTS: The results of this study demonstrated that EPF activity is detected in 35 women's sera out of 70 women within 2–7 days after ovulation, and 28 women out of the 35 were pregnant, which was known by follow-up, and 7 were not pregnant, possibly due to either false positive results or embryo loss because of preimplantation failure, thus causing no pregnancy. The other 35 out of 70 had no EPF activity and 34 of them were not pregnant, which was known by follow-up, but one case became pregnant, which was false negative result. Our study showed that diagnosis of the super early pregnancy could be made by detecting EPF activity in maternal serum within the time of preimplantation. The accuracy of pregnancy diagnosis by this method is 88.6%, with a false negative rate of 3.4% and a false positive rate of 17.1%. The β-HCG level was measured from the above 70 women's sera in order to contrast EPF activity. All of the sera collected 2–6 days following ovulation indicated that there were lower β-HCG values in very early pregnancy (≥a5 mIU/ml). On the seventh day after ovulation, EPF activity was detected in 11 out of 15 sera with only 2 of them with a b-HCG level that reached or slightly surpassed that of the early pregnancy diagnosis (5 mIU/ml and 5.4 mIU/ml, respectively). This demonstrated that β-HCG is not the earliest signal of pregnancy; otherwise the EPF activity is one that appears 2–6 days earlier than β-HCG appears. We measured the progesterone level of the 48 sera from the 70 collected above within 2–7 days postovulation and found most of them reached the level of progesterone in the luteal phase (7.5–98.3 nmol/L). This indicated that ovulation had taken place in these women, which was in accordance with observations by ultrasonography. CONCLUSIONS: Our study showed that diagnosis (of 88.6%) of super early pregnancy could be made with an accuracy of 88.6% by detecting EPF activity in maternal serum within 2-days after ovulation. This offers a basis for pregnancy diagnosis for the women who attempt to terminate their pregnancy safely or who conceive unexpectedly, and it contributes to family-planning.  相似文献   
125.
126.
In this paper, we investigate variance component models of both linkage analysis and high resolution linkage disequilibrium (LD) mapping for quantitative trait loci (QTL). The models are based on both family pedigree and population data. We consider likelihoods which utilize flanking marker information, and carry out an analysis of model building and parameter estimations. The likelihoods jointly include recombination fractions, LD coefficients, the average allele substitution effect and allele dominant effect as parameters. Hence, the model simultaneously takes care of the linkage, LD or association and the effects of the putative trait locus. The models clearly demonstrate that linkage analysis and LD mapping are complementary, not exclusive, methods for QTL mapping. By power calculations and comparisons, we show the advantages of the proposed method: (1) population data can provide information for LD mapping, and family pedigree data can provide information for both linkage analysis and LD mapping; (2) using family pedigree data and a sparse marker map, one may investigate the prior suggestive linkage between trait locus and markers to obtain low resolution of the trait loci, because linkage analysis can locate a broad candidate region; (3) with the prior knowledge of suggestive linkage from linkage analysis, both population and family pedigree data can be used simultaneously in high resolution LD mapping based on a dense marker map, since LD mapping can increase the resolution for candidate regions; (4) models of high resolution LD mappings using two flanking markers have higher power than that of models of using only one marker in the analysis; (5) excluding the dominant variance from the analysis when it does exist would lose power; (6) by performing linkage interval mappings, one may get higher power than by using only one marker in the analysis.  相似文献   
127.
128.
Scabies, infection with Sarcoptes scabiei, is known to be predisposed to by poor body hygiene, environmental exposure, and systemic immunodeficiency. We report the case of an 83-year-old man with Sezary's syndrome who developed scabies limited to the skin of the upper chest, the same location where he had previously received electron beam radiation treatments for cutaneous T-cell lymphoma. Histologic and immunohistochemical studies demonstrated that sections of the previously irradiated right and left chest skin, compared to non-irradiated chest, abdominal, and leg skin, had infestation by scabies, diminished involvement by T-cell lymphoma, and notably reduced numbers of Langerhans cells. These findings suggest that the development of scabies may be predisposed to by local cutaneous radiation therapy, and that it may be mediated by local cutaneous immunodeficiency secondary to reduced numbers of Langerhans cells.  相似文献   
129.
为解决细胞内抗原应用免疫金银法染色时背景过重的问题,建立了甘氨酸二次阻断的处理方法,效果较好。  相似文献   
130.
猫前脑和脑干向中缝背核的纤维投射   总被引:4,自引:0,他引:4  
中缝背核在针剌镇痛过程中起重要作用。本文用HRP法,对猫前脑和脑干向中缝背核的纤维投射,作了进一步的研究。 HRP注入中缝背核吻侧部后,在前脑双侧先导回皮质和梨状前区皮质V层出现较多被标记的锥体细胞;缰外侧核出现较密集且形态不一的标记细胞;下丘脑各区(视前区、外侧区、内侧区和后区)也出现散在的标记细胞。 HRP注入中缝背核尾侧部后,除前脑出现标记细胞的部位与HRP注入吻侧部者相同外,在脑干中脑导水管周围灰质、蓝斑,其他中缝核(中央上核,中缝线形核和中缝大核)、臂旁内、外侧核及脑干网状结构等处,也观察到标记细胞。结果表明前脑皮质、缰外侧核、下丘脑各区均有纤维直接投射到中缝背核。中缝背核也接受来自中脑水管周围灰质、蓝斑、其他中缝核等核团的纤维投射;中缝背核吻侧部和尾侧部的传入投射,存在一定的局部定位关系,即中缝背核吻侧部只接受来自前脑的纤维投射,其尾侧部既接受来自前脑的纤维投射,也接受来自脑干的纤维投射。  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