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   4728篇
  免费   133篇
  国内免费   2篇
电工技术   35篇
化学工业   567篇
金属工艺   50篇
机械仪表   58篇
建筑科学   65篇
矿业工程   1篇
能源动力   69篇
轻工业   378篇
水利工程   21篇
石油天然气   18篇
无线电   138篇
一般工业技术   410篇
冶金工业   2823篇
原子能技术   12篇
自动化技术   218篇
  2024年   4篇
  2023年   13篇
  2022年   31篇
  2021年   75篇
  2020年   52篇
  2019年   73篇
  2018年   64篇
  2017年   85篇
  2016年   82篇
  2015年   62篇
  2014年   99篇
  2013年   136篇
  2012年   98篇
  2011年   146篇
  2010年   101篇
  2009年   126篇
  2008年   101篇
  2007年   96篇
  2006年   70篇
  2005年   60篇
  2004年   65篇
  2003年   57篇
  2002年   44篇
  2001年   33篇
  2000年   51篇
  1999年   106篇
  1998年   914篇
  1997年   538篇
  1996年   330篇
  1995年   211篇
  1994年   176篇
  1993年   188篇
  1992年   34篇
  1991年   39篇
  1990年   52篇
  1989年   48篇
  1988年   43篇
  1987年   44篇
  1986年   48篇
  1985年   20篇
  1984年   8篇
  1983年   9篇
  1982年   11篇
  1981年   11篇
  1980年   22篇
  1979年   4篇
  1978年   9篇
  1977年   51篇
  1976年   114篇
  1975年   4篇
排序方式: 共有4863条查询结果,搜索用时 0 毫秒
1.
2.
The focus of posttransplant care and clinical research has been on the management of rejection and short-term side effects associated with immunosuppressive therapy. Long-term side effects have only recently been recognized as potential health problems in liver transplant recipients. The aim of this pilot study was to determine the feasibility of using the Healthier People Version 4.0 Health Risk Appraisal as a tool for identifying existing and potential risk factors for premature disease and death among asymptomatic liver transplant recipients and to describe health risks in adult liver transplant recipients. The sample consisted of 50 adult first-time liver transplant recipients. It was found that this tool highlights health risks affecting life expectancy and pinpoints risks that an individual can control. It also provides practitioners with information necessary to design appropriate prevention and health promotion strategies to assure better health and quality of life for patients following liver transplantation.  相似文献   
3.
The striatum receives excitatory input from virtually the entire cerebral cortex. In the adult, this input is segregated into two functionally distinct compartments of the striatum, the patch (striosome) and matrix regions. This study determined whether the patterning of corticostriatal afferents from the prelimbic cortex to the striatal patch compartment develops during the early period of collateral formation or instead at the time of peak synaptogenesis. Initial formation of corticostriatal axon collaterals was observed by embryonic day (E) 19. Quantification of corticostriatal collaterals revealed a significant increase in the number and complexity of collateral branches at postnatal day 6 as compared to E19. Concomitant with the increase in collateral branching, a heterogeneous pattern of collateralization consisting of parallel rows of corticostriatal collaterals was observed in the medial striatum. In addition to the rows, clusters of corticostriatal axons occurred more laterally. These clusters colocalized with patches of dense tyrosine hydroxylase-positive fibers, a marker for the striatal patch compartment in the neonatal mouse. Together, these data indicate that corticostriatal patterning occurs during the period of early axon collateralization resulting in a segregation of corticostriatal axon collaterals from the prelimbic cortex to the striatal patch compartment.  相似文献   
4.
5.
BACKGROUND: This study examined patients with a first-episode of affective psychosis during acute and compensated states in order to determine whether changes in attentional functioning over time were accompanied by changes in the severity of psychotic or affective symptoms. METHODS: Attentional performance was measured in patients (n = 27) using the degraded-stimulus continuous Performance Test (CPT) and symptoms were assessed at the time of index hospitalization, and 2 months after discharge. A comparison group of normal volunteers (n = 31) also performed the CPT two months apart. RESULTS: Patients performed significantly worse than controls at the initial testing but not at follow-up. The improvement in attentional performance significantly correlated with decreased severity of manic symptoms. CONCLUSIONS: Results suggest attentional dysfunction is a state-dependent characteristic of mania, and may provide an additional measure of clinical improvement following treatment.  相似文献   
6.
7.
8.
Integrating principles from a variety of theory has led to the development of a conceptual framework for reengineering in a clinical care delivery setting to improve the value of services provided to the customer. A conceptual framework involving the identification of three high level core processes to reengineer can provide clarity and focus for clinicians to begin directing reengineering efforts. Those core processes are: clinical management of the patient's medical needs, patient operational processes to support the clinical processes, and administrative decision-making processes to support the implementation of the clinical and operational processes. Improvement in any one of these areas has the potential to increase value, but the concurrent targeting of these core processes for reengineering has provided a synergy that has accelerated the achievement of the desired outcomes in the area of surgical services.  相似文献   
9.
Gyrotron coaxial resonators with a longitudinally slotted inner cylinder are examined analytically using a surface impedance model, from which expressions for the electromagnetic field, ohmic quality (Q) factor, and characteristic equation of the transverse eigenvalues χ m,p are obtained. The major attributes of such resonators are expressed by the dependence of χm,p on the parameter C-defined as the ratio of the outer to inner radii of the coaxial structure. In that connection, the effect of the corrugation parameters on χm,p is particularly investigated on the basis of an expression derived for the slope function dχm,p,p/dC. It is shown that the χm,p(C) curve may either exhibit oscillatory behavior or present a flat portion over a wide range of C depending on the corrugation parameters chosen. The theory is checked against experiment in which resonant frequencies and total Q factors were measured for TE modes operating in the range of 8-16 GHz in a coaxial cavity with 40 slots. Good agreement is found in that the magnitude of the relative error in frequency is less than 0.5%. Corrugated coaxial resonators prove to be relevant to megawatt gyrotrons where highly selective cavities are required to ensure high conversion efficiency  相似文献   
10.
Advances in genetic engineering and expression systems have led to a rapid progress in the development of immunoglobulins fused to other proteins. These 'antibody fusion proteins' have novel properties and include antibodies fused to the cytokine interleukin-2. In the present review we describe strategies for construction of these antibody-interleukin-2 fusion proteins and discuss their in vitro and in vivo properties. Antibody-interleukin-2 fusion proteins retain both antibody associated functions such as antigen binding, complement activation and Fc gamma receptor binding as well as interleukin-2 associated functions such as the stimulation of proliferation of CTLL2 cells. In vivo, they produce strong potentiation of the host immune response against any associated antigen. In addition, these novel molecules are able to target tumor cells and produce a specific and effective T cell response capable of eliminating the tumor. These properties suggest that antibody-interleukin-2 fusion proteins will be useful in the diagnosis and/or treatment of human cancer as well as in the potentiation of human response against any associated antigen.  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