全文获取类型
收费全文 | 3244篇 |
免费 | 85篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 28篇 |
综合类 | 18篇 |
化学工业 | 215篇 |
金属工艺 | 43篇 |
机械仪表 | 34篇 |
建筑科学 | 45篇 |
矿业工程 | 6篇 |
能源动力 | 55篇 |
轻工业 | 93篇 |
水利工程 | 22篇 |
石油天然气 | 22篇 |
无线电 | 200篇 |
一般工业技术 | 241篇 |
冶金工业 | 2141篇 |
原子能技术 | 8篇 |
自动化技术 | 178篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 38篇 |
2021年 | 76篇 |
2020年 | 55篇 |
2019年 | 45篇 |
2018年 | 58篇 |
2017年 | 46篇 |
2016年 | 49篇 |
2015年 | 29篇 |
2014年 | 45篇 |
2013年 | 85篇 |
2012年 | 54篇 |
2011年 | 73篇 |
2010年 | 48篇 |
2009年 | 61篇 |
2008年 | 53篇 |
2007年 | 51篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 17篇 |
2003年 | 28篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 87篇 |
1998年 | 653篇 |
1997年 | 383篇 |
1996年 | 250篇 |
1995年 | 148篇 |
1994年 | 134篇 |
1993年 | 156篇 |
1992年 | 27篇 |
1991年 | 29篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 35篇 |
1987年 | 32篇 |
1986年 | 21篇 |
1985年 | 21篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 26篇 |
1978年 | 6篇 |
1977年 | 66篇 |
1976年 | 116篇 |
1975年 | 10篇 |
1972年 | 3篇 |
排序方式: 共有3349条查询结果,搜索用时 31 毫秒
1.
Zakraoui Jezia Saleh Moutaz Al Ja’am Jihad 《Multimedia Tools and Applications》2019,78(16):22833-22859
Multimedia Tools and Applications - Text-to-picture systems attempt to facilitate high-level, user-friendly communication between humans and computers while promoting understanding of natural... 相似文献
2.
Radiochemistry - Azathioprine, an antitumor agent, was labeled with 99mTc using stannous chloride dihydrate as a reducing agent. Factors such as the amounts of the reducing agent and substrate, pH,... 相似文献
3.
MA Nowak AL Lloyd GM Vasquez TA Wiltrout LM Wahl N Bischofberger J Williams A Kinter AS Fauci VM Hirsch JD Lifson 《Canadian Metallurgical Quarterly》1997,71(10):7518-7525
Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus. 相似文献
4.
5.
The structural properties and hydrogen bonding of undoped and phosphorous doped polycrystalline silicon produced by step-by-step laser dehydrogenation and crystallization technique were investigated using Raman spectroscopy and hydrogen effusion measurements. At low laser fluences, EL, a two-layer system is created. This is accompanied by the change in hydrogen bonding. The intensity of the Si–H vibration mode at 2000 decreases faster than the one at 2100 cm−1. This is even more pronounced in phosphorous-doped specimens. The laser crystallization results in an increase of the hydrogen binding energy by approximately 0.2–0.3 eV compared to the amorphous starting materials. 相似文献
6.
7.
8.
Neonatal emergencies have become more common as increasingly sophisticated Neonatal Intensive Care Units graduate lower birth-weight babies born at younger gestational ages. These patients present a number of challenges to emergency physicians. They are often discharged with apnea monitors, which generate a high number of false alarms. Neonatal Intensive Care Unit graduates, however, are predisposed to a number of conditions that can result in true episodes of apnea. We present such a case and will discuss the unusual underlying cause of apnea, the utility of apnea monitors, and the need for emergency physicians to be prepared to evaluate and treat these potentially complicated patients. 相似文献
9.
Activation of the mitogen-activated protein (MAP) kinase pathway has been associated with both cell proliferation and differentiation. Constitutively activated forms of Mek (MAP kinase/Erk kinase) and Erk (MAP kinase) have been previously shown capable of inducing differentiation or proliferation in nonhematopoietic cells. To specifically examine the role of Erk activation in megakaryocytic growth and development, we activated the MAP kinase pathway by the transfection of constitutively activated Mek or Erk cDNA into a human megakaryoblastic cell line, CMK, by electroporation. The CMK transfectant clones that expressed constitutively activated Mek or Erk showed morphologic changes of differentiation. Transfected cells also showed expression of mature megakaryocytic cell surface markers. The MAP kinase pathway was also activated by treatment of the hematopoietic cells with a cytokine that activates Erk. The treatment of CMK cells with stem cell factor (SCF ) caused MAP kinase activation and induced differentiation by the expression of mature megakaryocytic cell surface markers. The effects of the SCF treatment were inhibited by pretreatment with a specific inhibitor of the MAP kinase pathway, PD98059. In this report, we conclude that activation of the MAP kinase pathway was both necessary and sufficient to induce differentiation in this megakaryoblastic cell line. 相似文献
10.
CM Haystead P Gailly AP Somlyo AV Somlyo TA Haystead 《Canadian Metallurgical Quarterly》1995,377(2):123-127
RATIONALE AND OBJECTIVES: We compared adverse reactions and image quality for hysterosalpingography (HSG) performed with ionic (diatrizoate meglumine combined with iodipamide meglumine [DM + IM]) and nonionic (iohexol) contrast media. METHODS: We performed a study of 95 patients who had HSG and were randomly selected to receive DM + IM or iohexol. Patients reported episodes of abdominal pain and other adverse reactions immediately and 24 hr after the procedure and categorized severity of symptoms on a subjective scale. Two radiologists evaluated image quality for diagnosis. RESULTS: Prevalence of abdominal pain and other reactions both immediately and 24 hr after HSG was lower in patients who received iohexol than in patients who received DM + IM. Moderate or severe abdominal pain was significantly lower in the iohexol group than in the DM + IM group (p < .05). Visualization of the uterine cavity and ampullary rugae was judged excellent with both contrast media (87% with iohexol and 92% with DM + IM). CONCLUSION: Iohexol and DM + IM are excellent contrast media for use during HSG; iohexol 300 may cause fewer episodes of more severe and prolonged abdominal pain. 相似文献