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   31905篇
  免费   2621篇
  国内免费   180篇
耳鼻咽喉   320篇
儿科学   1101篇
妇产科学   714篇
基础医学   3725篇
口腔科学   645篇
临床医学   3029篇
内科学   6795篇
皮肤病学   559篇
神经病学   2507篇
特种医学   1023篇
外科学   4755篇
综合类   812篇
一般理论   16篇
预防医学   2188篇
眼科学   1323篇
药学   2359篇
  1篇
中国医学   131篇
肿瘤学   2703篇
  2023年   245篇
  2022年   396篇
  2021年   836篇
  2020年   525篇
  2019年   757篇
  2018年   865篇
  2017年   599篇
  2016年   687篇
  2015年   772篇
  2014年   1058篇
  2013年   1257篇
  2012年   2057篇
  2011年   2105篇
  2010年   1203篇
  2009年   1048篇
  2008年   1829篇
  2007年   1773篇
  2006年   1647篇
  2005年   1571篇
  2004年   1563篇
  2003年   1380篇
  2002年   1235篇
  2001年   1129篇
  2000年   1023篇
  1999年   878篇
  1998年   310篇
  1997年   237篇
  1996年   212篇
  1995年   213篇
  1994年   189篇
  1993年   168篇
  1992年   513篇
  1991年   479篇
  1990年   439篇
  1989年   402篇
  1988年   363篇
  1987年   336篇
  1986年   331篇
  1985年   328篇
  1984年   223篇
  1983年   206篇
  1982年   141篇
  1981年   107篇
  1980年   111篇
  1979年   161篇
  1978年   93篇
  1977年   104篇
  1976年   70篇
  1974年   85篇
  1973年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Burnout is a syndrome of emotional exhaustion, depersonalization, and reduced personal accomplishment that can occur among individuals who do "people work" of some kind. Health care providers, including dentists, are at high risk for burnout because their occupation often requires intense interaction with fearful, demanding patients on a daily basis. The purpose of this study was to assess the prevalence of burnout among Texas dentists using a standardized measurement device, the Maslach Burnout Inventory (MBI). Dentists attending the 1989 Texas Dental Association Annual Session were surveyed using the MBI. The respondents' results were analyzed and compared to each other as well as to the norms of medicine and to society (human service workers nationwide). Among the Texas sample, male dentists scored significantly higher for emotional exhaustion and depersonalization than did female dentists. When compared to the norms of medical workers, Texas dentists scored higher burnout in the depersonalization subscale, but lower burnout for personal accomplishment. The Texas sample again scored lower for burnout in the personal accomplishment subscale when compared to societal norms. At no time did the Texas sample fall into the high range of experienced burnout as defined by the survey instrument. Texas dentists did not appear "burned out" as a group and actually demonstrated an increased sense of personal accomplishment in their profession.  相似文献   
82.
The effect of axotomy on the expression of the 57 kDa neuronal intermediate filament (IF) protein in adult rat dorsal root ganglion (DRG) neurons was examined. This IF protein is known to have an exclusively neuronal localization but is considerably more limited in its distribution in the nervous system than the neurofilament (NF) triplet proteins. The 57 kDa neuronal IF protein is similar (and perhaps identical) to the protein "peripherin" and is known to be the product of a Type III IF gene. Since the down-regulated expression of NF proteins (products of type IV IF genes) has been well established, it was of interest to determine whether the novel 57 kDa IF protein was regulated in a similar or different manner from that of the NFs in axotomized neurons. In vitro pulse-labeling of DRGs with 35S-methionine: cysteine followed by 2-dimensional gel electrophoresis/fluorography revealed that the synthesis of the 57 kDa neuronal IF protein was increased 2 weeks after sciatic nerve crush. Immunocytochemical studies using a polyclonal antibody to the 57 kDa neuronal IF protein showed that the immunodetectable levels of this protein increased in DRG neurons after peripheral axotomy. In the normal DRG, staining was localized almost exclusively to small-sized neurons. At 2 weeks after axotomy, however, large- and medium-sized neurons also became immunoreactive; in addition, the overall level of staining in the DRG was greater than normal. Quantitative analysis of in situ hybridizations of DRG neurons with a 35S-labeled cDNA probe specific for the 57 kDa neuronal IF protein revealed a significant increase in the level of 57 kDa IF mRNA in the large-sized (greater than 1000 microns2) neurons 2 weeks after axotomy; the level of 57 kDa IF mRNA in the small neurons was not different from normal at that time. Finally, using a newly developed paradigm for examining the composition of regenerating axons by axonal transport, we determined that significant amounts of the 57 kDa neuronal IF protein were conveyed into the regrowing axonal sprouts of DRG neurons. When DRG neurons were conditioned by a previous axotomy (a crush axotomy of the distal sciatic nerve 2 weeks earlier) and then stimulated to regenerate axons by a second crush axotomy located very close to the DRG, the regenerating sprouts incorporated and conveyed significantly more 57 kDa IF protein by slow axonal transport than did those elaborated by unprimed DRG neurons.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
83.
This is a retrospective study of the outcome of surgical procedures in patients who were Jehovah's Witnesses. Over a 75-month period, 58 Jehovah's Witness patients had 78 surgical procedures at the Vancouver General Hospital. Three patients had preexisting anaemia of less than 100 g.L-1 haemoglobin. Postoperative haemoglobin concentration decreased below 50 g.L-1 in three patients. One patient had a postoperative haemoglobin of 34 g.L-1 (haematocrit 10.1 per cent) and survived. One patient died from uncontrollable postoperative haemorrhage. Perioperative morbidity was not uncommon, including significant hypotension (eight cases), cardiac arrhythmias (six), myocardial ischaemia (three), excessive bleeding (four), postoperative nausea or syncope (four), and wound or urinary tract infection (four).  相似文献   
84.
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   
85.
Abortive neovascular outgrowths from the retina were identified in 13 out of 34 eyes (38%) undergoing vitrectomy for diabetic vitreous haemorrhage. Postoperatively, fluorescein angiography of the lesions demonstrated a characteristic smoke-stack pattern of dye leakage. Each outgrowth appears to represent a focal variant of preretinal neovascularisation complicating retinal capillary non-perfusion and inner retinal ischaemia, their distinctive features being determined primarily by the absence of a cortical vitreous scaffold on the retinal surface at the time of vasoproliferation.  相似文献   
86.
In this article the merits of current liquid chromatography (LC) columns and techniques are reviewed, to include the following topics: (1) a brief introduction to rational therapeutic drug monitoring (TDM) to justify drug measurements; (2) selected recent survey results from the College of American Pathologists (CAP) to establish the current utilization pattern of LC for TDM in the USA; (3) LC analyses of major classes of drugs--antiarrhythmics, antidepressants, antiepileptics, antimicrobials, cyclosporine, and others--with emphasis on analysis of these drugs in human serum or plasma, by focusing on the less usual, reversed-phase functional groups such as CN and phenyl, and by the use of "mini" columns, silica and polymeric columns, the emphasis being reduced on the well-established C-18 columns; (4) high-speed LC; (5) various approaches of direct sample analysis--solvent extraction, automated sample processing, column switching, micro-injections, micellar chromatography, electrochemical detection with photolytic derivation, and the internal surface reversed-phase column of Pinkerton; (6) microbore LC drug analysis; (7) clinical chiral separation; and (8) overall conclusions.  相似文献   
87.
Trisomy 22 is an uncommon chromosomal abnormality in acute myeloid leukemia. Recent studies, however, have shown an association between trisomy 22 and acute myeloid leukemia with a monocytic component, and in particular, acute myelomonocytic leukemia with marrow eosinophilia. Furthermore, it has also been suggested that trisomy 22 was in fact only a secondary chromosomal change occurring in acute myeloid leukemia with inv(16). In this report, we analyze the morphological, cytogenetic, and molecular findings of three cases of acute myeloid leukemia with trisomy 22 but without cytogenetic evidence of inv(16). The results indicate a consistent association between trisomy 22 and inv(16), the latter being cytogenetically cryptic in some cases. This finding is of potential diagnostic and therapeutic significance.  相似文献   
88.
89.
1. The sodium-dependent oxygen consumption of pieces of toad bladder (Bufo marinus) has been investigated using an oxygen electrode.2. The effect of polyvalent cations (Ca(2+), Sr(2+), Mg(2+), Eu(3+), La(3+) and Mn(2+)) on sodium-dependent oxygen consumption has been measured. All cations inhibited oxygen consumption, the order of effectiveness being Ca(2+) > Sr(2+) > Mg(2+) > Mn(2+) > Eu(3+) > La(3+).3. Treatment of bladder pieces with antidiuretic hormone (50 m-u./ml.) decreased the effectiveness of Ca(2+) and Sr(2+) as inhibitors of sodium-dependent oxygen consumption. Mn(2+), Eu(2+) and La(2+) were more effective after hormonal treatment, while the effectiveness of Mg(2+) was unaltered.4. The results have been interpreted in terms of a model in which sodium entry to the transporting mechanisms of the epithelium is controlled by Ca(2+), and in which antidiuretic hormone alters Ca(2+) binding and so affects sodium transport.  相似文献   
90.
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