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   2420篇
  免费   164篇
  国内免费   11篇
耳鼻咽喉   11篇
儿科学   38篇
妇产科学   45篇
基础医学   489篇
口腔科学   17篇
临床医学   155篇
内科学   545篇
皮肤病学   31篇
神经病学   276篇
特种医学   150篇
外科学   345篇
综合类   38篇
一般理论   1篇
预防医学   117篇
眼科学   11篇
药学   147篇
中国医学   3篇
肿瘤学   176篇
  2022年   27篇
  2021年   32篇
  2020年   27篇
  2019年   32篇
  2018年   34篇
  2017年   29篇
  2016年   42篇
  2015年   46篇
  2014年   54篇
  2013年   91篇
  2012年   149篇
  2011年   110篇
  2010年   103篇
  2009年   79篇
  2008年   128篇
  2007年   85篇
  2006年   106篇
  2005年   101篇
  2004年   92篇
  2003年   96篇
  2002年   74篇
  2001年   87篇
  2000年   76篇
  1999年   59篇
  1998年   38篇
  1997年   24篇
  1996年   25篇
  1995年   34篇
  1993年   19篇
  1992年   35篇
  1991年   38篇
  1990年   57篇
  1989年   35篇
  1988年   39篇
  1987年   53篇
  1986年   35篇
  1985年   40篇
  1984年   29篇
  1983年   31篇
  1981年   18篇
  1980年   29篇
  1979年   28篇
  1978年   20篇
  1977年   21篇
  1976年   25篇
  1975年   19篇
  1974年   15篇
  1973年   15篇
  1972年   16篇
  1971年   19篇
排序方式: 共有2595条查询结果,搜索用时 0 毫秒
111.
112.
113.
114.
The field of cardiac xenotransplantation has entered an exciting era due to recent advances in the field. Although several hurdles remain, the use of rapidly evolving transgenic technology has the potential to address current allogeneic donor pool constraints and mechanical circulatory system device limitations. The success of xenotransplantation will undoubtedly be dependent on specific patient selection criteria. Defining these particular indications for xenotransplantation is important as we approach the possibility of clinical applications.  相似文献   
115.
The authors report on two gonadotropic carcinomas of the adenohypophysis that occurred in a55-year-old man (Case 1) and a 53-year-old woman (Case 2), with signs of mass effect and amenorrhea, respectively. Both lesions were macroadenomas. The tumor in Case 1 metastasized to dura mater, skull, nasal sinus, and larynx 2 years after patient presentation, whereas that in Case 2 spread to vertebral bodies and ribs after a 19-year latency. Histologically, the primary, recurrent, and metastatic lesions in Case 1 featured brisk mitotic activity and high MIB-1 levels as well as p53 labeling indices. Immunoreactivity for HER-2/neu was assessable only in rare neoplastic cells of the second recurrence and in 80% of cells of the dural metastasis. Low-level HER-2/neu gene amplification was evident in the recurrent tumors and metastasis. The sellar and metastatic tumors in Case 2 resembled benign gonadotropic adenoma with oncocytic change; p53 accumulation, HER-2/neu overexpression, and HER-2/neu gene amplification were not present. The results indicate that low-level amplification of the HER-2/neu gene might be associated with pituitary carcinomas in which more aggressive behavior is seen. Further studies are needed to determine whether HER-2/neu plays a role in the pathogenesis of pituitary carcinoma.  相似文献   
116.
BACKGROUND: Anecdotal reports of port site tumor recurrence have dampened the enthusiasm for laparoscopic colectomy for cancer. We developed a rat model that creates a high incidence of port site metastasis following laparoscopic intervention. Our goal was to assess the feasibility of minimizing implantations using port site irrigation prior to wound closure. METHODS: Colon cancer carcinomatosis was established in 46 female BD9 rats using intraperitoneal injections of 10(6) DHD-K12-TRb rat colon cancer cells. This preparation yielded an 81% incidence of port site metastasis in a control group. Laparoscopic sham surgery was performed using four ports and a CO(2) pneumoperitoneum. Four treatment groups were studied by irrigating each port site as follows: Group I, sterile water; group II, normal saline; group III, heparin; group IV, 5-fluorouracil (5-FU). The animals were killed at 4 weeks, and the port sites were examined for tumors. RESULTS: There were no differences in port site metastasis between controls and groups I, II, and III. The 5-FU group showed a significant decrease (30% vs 81%) in metastasis. CONCLUSIONS: Port site irrigation with 5-FU at the time of laparoscopy reduces the incidence of port site tumor implantation in a rat colon cancer model. This finding may have utility in patients at high risk of such metastasis who undergo laparoscopy for colon cancer.  相似文献   
117.

Objective

Large-scale connectivity, especially interhemispheric connections, plays a crucial role for recovery after stroke. Here we used methods from information theory to characterize interhemispheric information flow in wake- and sleep-EEG after cerebral ischemia.

Methods

34 patients with unilateral ischemic stroke were included. Symbolic Transfer Entropy (STE) was applied between bipolar EEG signals on the left and the right cerebral hemisphere during polysomnographic recordings in the acute phase and 3?months after stroke.

Results

In the acute phase, we found a sleep stage-dependent preferred interhemispheric asymmetry: during non-REM sleep the information flow was predominantly directed from the contralesional toward the ipsilesional hemisphere. This effect was greatly reduced in a follow-up recording 3?months after stroke onset.

Conclusion

Our findings are consistent with functional imaging studies showing a transient hyperactivity of contralesional areas after stroke. We conclude that STE is a robust method for detecting post-stroke connectivity reorganizations, and that sleep stages have to be taken into account when assessing functional connectivity.

Significance

EEG is more widely available than functional MRI. Future studies will have to confirm whether EEG derived STE can be useful in a clinical setting during rehabilitation after stroke.  相似文献   
118.
neurogenetics - Monoamine neurotransmitter disorders present predominantly with neurologic features, including dystonic or dyskinetic cerebral palsy and movement disorders. Genetic conditions that...  相似文献   
119.
The GRADE approach to grading the quality of evidence and strength of recommendations provides a comprehensive and transparent approach for developing clinical recommendations about using diagnostic tests or diagnostic strategies. Although grading the quality of evidence and strength of recommendations about using tests shares the logic of grading recommendations for treatment, it presents unique challenges. Guideline panels and clinicians should be alert to these special challenges when using the evidence about the accuracy of tests as the basis for clinical decisions. In the GRADE system, valid diagnostic accuracy studies can provide high quality evidence of test accuracy. However, such studies often provide only low quality evidence for the development of recommendations about diagnostic testing, as test accuracy is a surrogate for patient-important outcomes at best. Inferring from data on accuracy that using a test improves outcomes that are important to patients requires availability of an effective treatment, improved patients' wellbeing through prognostic information, or – by excluding an ominous diagnosis – reduction of anxiety and the opportunity for earlier search for an alternative diagnosis for which beneficial treatment can be available. Assessing the directness of evidence supporting the use of a diagnostic test requires judgments about the relationship between test results and patient-important consequences. Well-designed and conducted studies of allergy tests in parallel with efforts to evaluate allergy treatments critically will encourage improved guideline development for allergic diseases.  相似文献   
120.
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