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   1002篇
  免费   53篇
  国内免费   40篇
耳鼻咽喉   11篇
儿科学   41篇
妇产科学   12篇
基础医学   128篇
口腔科学   83篇
临床医学   109篇
内科学   194篇
皮肤病学   27篇
神经病学   82篇
特种医学   92篇
外科学   107篇
综合类   8篇
预防医学   52篇
眼科学   11篇
药学   86篇
中国医学   7篇
肿瘤学   45篇
  2023年   9篇
  2022年   18篇
  2021年   30篇
  2020年   20篇
  2019年   18篇
  2018年   35篇
  2017年   23篇
  2016年   17篇
  2015年   40篇
  2014年   33篇
  2013年   48篇
  2012年   74篇
  2011年   74篇
  2010年   55篇
  2009年   52篇
  2008年   47篇
  2007年   70篇
  2006年   35篇
  2005年   38篇
  2004年   32篇
  2003年   30篇
  2002年   25篇
  2001年   19篇
  2000年   20篇
  1999年   9篇
  1998年   21篇
  1997年   20篇
  1996年   25篇
  1995年   12篇
  1994年   21篇
  1993年   13篇
  1992年   15篇
  1991年   8篇
  1990年   7篇
  1989年   13篇
  1988年   8篇
  1987年   5篇
  1986年   10篇
  1985年   9篇
  1984年   9篇
  1983年   4篇
  1982年   6篇
  1981年   6篇
  1980年   1篇
  1979年   1篇
  1978年   3篇
  1977年   3篇
  1975年   1篇
  1973年   1篇
  1967年   1篇
排序方式: 共有1095条查询结果,搜索用时 31 毫秒
1.
2.
3.
Beckmann  CF; Roth  RA; Luedke  MD 《Radiology》1986,159(3):643-645
In 44 patients with one or more calculi in the upper two-thirds of the ureter, single-stage percutaneous nephrolithotomy was performed through a middle or upper calyceal nephrostomy after cystoscopic placement of an occlusion balloon catheter distal to the calculus; in 42, the procedure was successful. The occlusion balloon catheter permitted retrograde opacification of all systems for enhanced renal puncture. In the last 30 patients an attempt was made either to push the calculus upward mechanically or to flush it upward into the renal pelvis with carbon dioxide or dilute contrast material. This was successful in 24 of these patients. Prior overnight occlusion of the ureter by means of ureteral dilatation further facilitates dislodgment of the calculus, which was successful in 12 of 13 patients.  相似文献   
4.
5.
6.
Protoplasts of the pathogenic plant fungus, Crinipellis perniciosa, were transformed to hygromycin B resistance using the pAN7-1 plasmid, which contains the Escherichia coli hph gene under the control of Aspergillus nidulans regulatory sequences. The pAN7-1 plasmid was introduced by PEG/CaCl(2) treatment. Transformation frequencies of 1.6-2.5 transformants/microg of DNA were achieved. About 54% of the transformants were abortive and 40 analyzed transformants were mitotically stable and showed different hygromycin B resistance levels. The presence of the hph gene was checked by PCR in five transformants and the integration of multiple plasmid copies into different genome sites was observed by Southern analysis. This is the first report of a C. perniciosa transformation system and represents an important step for further research into genetic manipulation of this fungal plant pathogen.  相似文献   
7.
Elevated blood pressure is an important risk factor for renal-, cerebro- and cardiovascular diseases. We used an efficient discordant sib-pair ascertainment scheme to investigate the impact of the distal end of the long arm of human chromosome 5 (chromosomal region 5q31.1-qter) containing genes for the alpha1B and beta2 adrenergic receptors and the dopamine receptor type 1A on variation of systolic blood pressure in young Caucasians. We measured eight highly polymorphic markers spanning this positional candidate gene-rich region in 427 individuals from 55 three-generation pedigrees containing 69 discordant sibling pairs, and calculated multipoint identity by descent (MIBD) probabilities. The results of genetic linkage and association tests indicate that the region between markers D5S2093 and D5S462 is significantly linked to one or more polymorphic genes influencing interindividual variation in systolic blood pressure levels. Since the alpha1B adrenergic receptor and dopamine receptor type 1A genes are located close to these markers, these data suggest that genetic variation in one or both of these G protein-coupled receptors, which participate in the control of vascular tone, plays an important role in influencing interindividual variation in systolic blood pressure levels.   相似文献   
8.
Sputum and serum from patients with active pulmonary tuberculosis (TB), healthy purified protein derivative-positive adults, and patients with bacterial pneumonia were collected to simultaneously assess local immunity in the lungs and peripheral blood. To determine whether cytokine profiles in sputum from TB patients and control subjects were a reflection of its cellular composition, cytospin slides were prepared in parallel and assessed for the presence of relative proportions of epithelial cells, neutrophils, macrophages, and T cells. Gamma interferon (IFN-γ) in sputum from TB patients was markedly elevated over levels for both control groups. With anti-TB therapy, IFN-γ levels in sputum from TB patients decreased rapidly and by week 4 of treatment were comparable to those in sputum from controls. Further, IFN-γ levels in sputum closely followed mycobacterial clearance. Although detected at fourfold-lower levels, IFN-γ immunoreactivities in serum followed kinetics in sputum. TNF-α, interleukin 8 (IL-8) and IL-6 also were readily detected in sputum from TB patients at baseline and responded to anti-TB therapy. In contrast to IFN-γ, however, TNF-α and IL-8 levels also were elevated in sputum from pneumonia controls. These data indicate that sputum cytokines correlate with disease activity during active TB of the lung and may serve as potential early markers for sputum conversion and response to anti-TB therapy.  相似文献   
9.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
10.
We developed a new device for respiratory revival in order to do it better than by using the auto inflating reanimation purse, which is common in this emergency situation. This is a portable equipment, handly operated, that controls a continuous flow of gas with until 100% of oxygen, that permits to define both peak inspiratory pressure and positive end expiratory pressure. Both inspiratory and expiratory time can be controlled by the operator during the revive process. All process can be effected using endotracheal tube or mask.  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