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   10763篇
  免费   343篇
  国内免费   49篇
电工技术   213篇
综合类   20篇
化学工业   1646篇
金属工艺   161篇
机械仪表   184篇
建筑科学   238篇
矿业工程   8篇
能源动力   511篇
轻工业   766篇
水利工程   91篇
石油天然气   154篇
武器工业   4篇
无线电   942篇
一般工业技术   1357篇
冶金工业   3538篇
原子能技术   78篇
自动化技术   1244篇
  2024年   17篇
  2023年   178篇
  2022年   422篇
  2021年   524篇
  2020年   373篇
  2019年   372篇
  2018年   480篇
  2017年   334篇
  2016年   377篇
  2015年   234篇
  2014年   357篇
  2013年   589篇
  2012年   389篇
  2011年   443篇
  2010年   282篇
  2009年   240篇
  2008年   228篇
  2007年   209篇
  2006年   174篇
  2005年   157篇
  2004年   128篇
  2003年   108篇
  2002年   120篇
  2001年   62篇
  2000年   67篇
  1999年   188篇
  1998年   1126篇
  1997年   696篇
  1996年   441篇
  1995年   255篇
  1994年   235篇
  1993年   230篇
  1992年   63篇
  1991年   36篇
  1990年   47篇
  1989年   65篇
  1988年   72篇
  1987年   47篇
  1986年   43篇
  1985年   59篇
  1984年   50篇
  1983年   47篇
  1982年   47篇
  1981年   38篇
  1980年   50篇
  1979年   24篇
  1978年   25篇
  1977年   105篇
  1976年   190篇
  1975年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
PURPOSE: To assess the role postoperative mydriatics play after extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens (IOL) implantation in causing iris modifications and in controlling inflammation. SETTING: Outpatients Department, Ninewells Hospital, Dundee, Scotland. METHODS: The prospective study comprised 136 patients who had standardized ECCE. Half the patients used a mydriatic for 2 weeks postoperatively. Anterior chamber activity, pain, and eye redness were evaluated at 2 weeks postoperatively; pupil shape, peripheral anterior synechias, IOL position, and iris adhesions, at 6 weeks. RESULTS: Iris-lens adhesions were significantly more common in the group using a mydriatic. There was no difference between the two groups in postoperative inflammation. CONCLUSION: Mydriatics should not be used routinely after ECCE with posterior chamber IOL implantation.  相似文献   
2.
This review is written to evaluate the stereoselectivity in cutaneous hydrolysis and transdermal transport of propranolol prodrug. This discussion will be useful in the development of knowledge about stereoselective cutaneous hydrolysis and its influence on stereoselective transdermal transport of many other chiral prodrugs and drugs. Propranolol prodrugs undergo stereoselective hydrolysis in hairless mouse skin homogenate and in excised skin samples during permeation; the stereoselectivity is markedly biased towards hydrolysis of the (R) isomer. Unlike the liver, the esterase activity of the skin is high in its cytosolic fraction. Most of the lipophilic propranolol prodrugs cause stereoselective permeation across hairless mouse skin. A mechanism of stereoselective permeation of propranolol prodrug across the skin has been proposed, which indicates that the stereoselectivity in permeation is resulted from the stereoselective hydrolysis of lipophilic prodrug during permeation.  相似文献   
3.
4.
5.
An assessment is made of the technical contents of flight-vehicle structures curricula at 41 U.S. universities with accredited aerospace engineering programs. The assessment is based on the technical needs for the new and projected aeronautical and space systems as well as on the likely characteristics of the aerospace engineering work environment. A number of deficiencies and areas of concern are identified and recommendations are presented for enhancing the effectiveness of flight-vehicle structures education. A number of government supported programs that can help aerospace engineering education are listed in the appendix.  相似文献   
6.
PURPOSE: The purpose of this analysis was to appreciate the management of visually handicaped children outside specialized structures. We also assessed relays between primary physicians, hospitals and specialized structures. METHOD: A 12-question survey was sent to 144 liberal ophthalmologists of the North of France. The questionnary included 12 questions. We compared the results to litterature. RESULTS: The response-rate was 59.6%. This study indicated that the observed children by the liberal ophtalmologists had more simple diseases than in specialized structures. In hospitals, it seemed that the ophtalmologists diagnosed more severe diseases. These practitioners diagnosed some of these diseases. However some of diagnosis were to late. This study showed that specialized structures were not enough known by the practitioners who detected this handicap and that the families prefered the taking in charge near their home. CONCLUSION: We demonstrated the necessary organisation of precocious and systematic detection, and the necessary information to all practitioners on specialized structures.  相似文献   
7.
Flow cytometry is a unique technology useful in the examination of effects of immunotoxic agents on target cells of the immune system. The purpose of this workshop was to provide an overview of the use of flow cytometry in new and established models of immunotoxicity, with emphasis on the potential applications, assay validation, and potential pitfalls. This overview begins with a discussion of methods useful in the assessment of Ca2+-dependent mechanisms of lymphoid cell activation in surface marker-defined human B cells, T cells, and monocytes. A discussion of the use of flow cytometry in analysis of apoptosis is also presented in this paper. The second paper presents data on the development and use of flow cytometry as an alternative to a Cr51 release assay for an assessment of cytotoxic T cell activation. The use of surface markers for characterizing and distinguishing the effects of chemical irritants from sensitizers is next presented, followed by an overview of the use of fluorescent probes to assess cell thiol status and overall oxidant-induced injury to lymphoid cells. Finally, an interlaboratory study designed to compare and evaluate the use of flow cytometry procedures in rat splenic cell subtyping is presented. Overall, these studies demonstrate the utility of flow cytometry assays in immunotoxicologic research, but further efforts are needed in the validation of many of these assays for routine use in immunotoxicologic testing.  相似文献   
8.
Factor V Leiden mutation was initially detected in thrombophilic patients and relatives by PCR RFLP (Restriction Fragment Length Polymorphism) according to Bertina (1). This technique presents some drawbacks and the current trend is to simplify the diagnosis. We describe a technique of Allele Specific Amplification (ASA) which is optimized in terms of reliability: an additional mismatch in antepenultimate position enables to obtain the same specificity as PCR RFLP. Furthermore, coamplification of internal control warrants an optimal sensitivity. All the PCR have been simplified: the DNA extraction improvement allows to analyse the genotype with only a few microliters of whole blood whatever the anticoagulant and the procedure of preservation (freezing, dried blood spots, storage at +4 degrees C for several days). This technique saves time. Moreover, full automation of the ASA technique may be shortened thanks to the lack of extraction and the positive/negative reading of the PCR signal.  相似文献   
9.
10.
PURPOSE: Despite aggressive surgery and postoperative radiation therapy, only 30% of patients who have advanced, potentially resectable carcinomas of the head and neck survive for 5 years. In the hope of improving this situation we studied the effect of postoperative radiotherapy delivered concurrently with cisplatin. METHODS AND MATERIALS: Patients who had Stage IV tumors and/or involved surgical margins received 60 Gy in 30 fractions over 6 weeks plus 100 mg/m2 of cisplatin on radiotherapy days 1, 23 and 43. Fifty-two patients participated in this trial and 51 were evaluated. Forty-three (84%) patients had pathologic T3 or T4 disease, 43 (84%) had Stage IV disease, and 27 (53%) had histologically involved surgical margins. RESULTS: Severe and life-threatening toxicities occurred in 20% and 12% of patients, respectively; the most common drug-related toxicities were leukopenia, anemia, nausea, and vomiting. Seventeen patients (43%) remain alive with no evidence of disease. Four patients (8%) died with no evidence of neoplastic disease, and one patient has died of a second independent malignancy. By actuarial analysis at 3 years, 48% of patients are alive, 81% have locoregional control of disease, and 57% are free of distant metastases. CONCLUSIONS: Based on comparison with similar patients treated in a prior Radiation Therapy Oncology Group/Intergroup trial (RTOG), we conclude that postoperative radiotherapy with concurrent cisplatin may improve locoregional control rates and should be prospectively tested.  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