全文获取类型
收费全文 | 32377篇 |
免费 | 470篇 |
国内免费 | 25篇 |
专业分类
教育 | 22322篇 |
科学研究 | 3963篇 |
各国文化 | 296篇 |
体育 | 2498篇 |
综合类 | 15篇 |
文化理论 | 237篇 |
信息传播 | 3541篇 |
出版年
2022年 | 218篇 |
2021年 | 331篇 |
2020年 | 487篇 |
2019年 | 763篇 |
2018年 | 1023篇 |
2017年 | 1001篇 |
2016年 | 851篇 |
2015年 | 543篇 |
2014年 | 813篇 |
2013年 | 6131篇 |
2012年 | 814篇 |
2011年 | 808篇 |
2010年 | 625篇 |
2009年 | 621篇 |
2008年 | 665篇 |
2007年 | 628篇 |
2006年 | 547篇 |
2005年 | 524篇 |
2004年 | 472篇 |
2003年 | 466篇 |
2002年 | 450篇 |
2001年 | 607篇 |
2000年 | 517篇 |
1999年 | 480篇 |
1998年 | 276篇 |
1997年 | 289篇 |
1996年 | 338篇 |
1995年 | 296篇 |
1994年 | 263篇 |
1993年 | 283篇 |
1992年 | 431篇 |
1991年 | 422篇 |
1990年 | 425篇 |
1989年 | 432篇 |
1988年 | 353篇 |
1987年 | 393篇 |
1986年 | 402篇 |
1985年 | 434篇 |
1984年 | 356篇 |
1983年 | 321篇 |
1982年 | 291篇 |
1981年 | 250篇 |
1980年 | 243篇 |
1979年 | 379篇 |
1978年 | 296篇 |
1977年 | 258篇 |
1976年 | 244篇 |
1975年 | 212篇 |
1974年 | 240篇 |
1971年 | 241篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
H.T. Chieh 《Journal of The Franklin Institute》1973,295(1):69-79
An effective way of constructing transforming matrix which similarly transforms a real square matrix to a quasi-diagonal form, is obtained. The transforming matrix as well as the quasi-diagonal form are real, regardless whether the given matrix has real eigenvalues or not. Formulas are included; they can be applied conveniently to evaluate a matrix function f(A) from the given scalar function f(λ). Three examples are given to illustrate the ease of application. These are the solutions of system differential equations of first and second order, and the determination of Nth root of a square matrix. 相似文献
992.
R Abraham M Joseph John R Calton J Dhanoa 《Indian journal of clinical biochemistry : IJCB》2006,21(1):95-100
Homocysteine(Hcy) has been implicated as a novel risk factor of Coronary Artery Disease (CAD) among Asian Indians, but many
studies done in India failed to reveal any direct correlation. It has also been reported that Folic acid and Vitamin B12 levels
inversely affect serum levels of homocysteine. In this study, we looked at the levels of homocysteine among patients with
CAD. The effect of Vitamin B12, Folate and other risk factors on homocysteine levels were also evaluated. Mean homocysteine
levels in cases (22.81±13.9, n=70) were significantly higher (p=<0.001) than the controls (7.77±7.3, n=70). However no statistically
significant correlation could be deduced between homocysteine Vitamin B12, and Folate. Cumulative analysis have indicated
an increase in homocysteine levels among patients with CAD with every additional risk factor. 相似文献
993.
Both structured and unstructured data, as well as structured data representing several different types of tuples, may be integrated into a single list for browsing or retrieval. Data may be arranged in the Gray code order of the features and metadata, producing optimal ordering for browsing. We provide several metrics for evaluating the performance of systems supporting browsing, given some constraints. Metadata and indexing terms are used for sorting keys and attributes for structured data, as well as for semi-structured or unstructured documents, images, media, etc. Economic and information theoretic models are suggested that enable the ordering to adapt to user preferences. Different relational structures and unstructured data may be integrated into a single, optimal ordering for browsing or for displaying tables in digital libraries, database management systems, or information retrieval systems. Adaptive displays of data are discussed. 相似文献
994.
995.
Knowledge Management Research & Practice - The definition and subsequent use of knowledge within and across organisational and social contexts has been a vibrant and evolving growth area over... 相似文献
996.
Salamatullah Quazi M. Mohiduzzaman Moududur R. Khan B. Nahar M. Mostafizur Rahman M. Nurul Islam M. Baquer Chandrakant S. Pandav Harun K. M. Yusuf 《Indian journal of clinical biochemistry : IJCB》1997,12(2):128-133
Urinary iodine levels in children (5–11 years) and in adult males and females (15–44 years) of three ecological zones (hilly, flood-prone and plains) of Bangladesh were analyzed to determine the status of biochemical iodine deficiency in the country. Data indicated that a large majority of the population all over Bangladesh have biochemical iodine deficiency urinary iodine excretion (UIE) less than the accepted cut-off level of 10 μg/dl. Adults were deficient to comparable degrees, 31.3% severely iodine deficient. The flood-prone zone was less affected: 71.7% children had iodine deficiency and 25% were severely deficient. Adults of this zone were less affected than the children. Iodine deficiency was least severe in the plain zone: 59.8% children were biochemically iodine deficient and of them 23.4% had UIE less than 2.0 μg/dl. In the case of the adults of this zone, 60.8% were biochemically iodine deficient and 20.6% had severe iodine deficiency. The results indicate that Bangladesh as a whole is an iodine deficient region, with the hilly zone being the most severely affected. Children were slightly more affected than the adults, and females were more affected than the males. 相似文献
997.
Guttelin JM 《Public understanding of science (Bristol, England)》2002,11(2):131-142
This paper addresses the issue of public perception of modern biotechnology in the Netherlands. Contrary to expectations, data from the 1999 Eurobarometer on biotechnology indicate that the position of the Dutch public in general is rather ambiguous, which is in contrast to many of its neighboring countries. The issue is described in terms of differences between the Netherlands and other European countries on political-economic, social-cultural, or media coverage indicators. On many indicators, the Dutch population differs from that of other European countries, and the Dutch opinion-leading media present a rather balanced perspective on modern biotechnology. 相似文献
998.
Winston Costa Pereira Muddanna S. Rao D. M. Vasudevan 《Indian journal of clinical biochemistry : IJCB》2003,18(2):161-168
Immunization with a proper dose of an antigenic stimulus leads to cell proliferation and antibody response of circulating
lymphocytes. We have previously observed that Secondary immunized spleenocytes resist ceramide-mediated apoptosisin vitro. Our present study is aimed at investigating thein vivo effect of immunization on apoptosis. Mice were subjected to either Primary or Secondary dose with Tetanus Toxoid. Unimmunized
spleenocytes served as controls. Unimmunized, Primary and Secondary immunized mice were later exposed to chemotherapeutic
drugs such as Etoposide/Methotrexate/Vincristine to induce apoptosis. Apoptosis was studied by using the Feulgen reaction
on 5μ thin parafin sections of spleen. It was observed that Secondary immunized mice showed a lower percentage of apoptosis
as compared to Primary or Unimmunized mice that was subjected to either of the chemotherapeutic drugs. It was thus concluded
that Secondary immunization inhibits the process of chemotherapeutic drug induced apoptosis in vivo. 相似文献
999.
Matthew Bernstein Linda Roney Meredith Kazer Elizabeth H. Boquet 《Health information and libraries journal》2020,37(3):240-244
This study explores how a three‐way collaboration between a University library, writing centre and faculty created avenues of training and support for students within a Doctor of Nursing Practice (DNP) program in an American University. The role of each partner involved in the collaboration is discussed alongside the profile of the DNP students. Lesson planning and classroom techniques for DNP information literacy classes are described and feedback from the partners and the students are discussed. The study confirms that collaboration is effective in improving research and writing skills. D.I. 相似文献
1000.
Albert KM 《Medical reference services quarterly》2007,26(3):1-19
Satisfying clinical information needs remains a major challenge in medicine, underscored by recent studies showing high medical error rates and suboptimal physician adherence to evidence-based practice guidelines. Advanced clinical decision support systems can improve practitioner performance and patient outcomes. Similarly, integrating online information resources into electronic health records (EHRs) shows great potential for positively impacting health care quality. This paper explores the evolution and current status of knowledge-based resource linkages within EHRs, including the benefits and drawbacks, as well as the important role librarians can play in this process. 相似文献