全文获取类型
收费全文 | 15130篇 |
免费 | 208篇 |
国内免费 | 7篇 |
专业分类
教育 | 11057篇 |
科学研究 | 1251篇 |
各国文化 | 107篇 |
体育 | 1248篇 |
综合类 | 7篇 |
文化理论 | 93篇 |
信息传播 | 1582篇 |
出版年
2021年 | 119篇 |
2020年 | 198篇 |
2019年 | 307篇 |
2018年 | 420篇 |
2017年 | 427篇 |
2016年 | 395篇 |
2015年 | 240篇 |
2014年 | 322篇 |
2013年 | 2852篇 |
2012年 | 331篇 |
2011年 | 400篇 |
2010年 | 249篇 |
2009年 | 246篇 |
2008年 | 348篇 |
2007年 | 257篇 |
2006年 | 325篇 |
2005年 | 223篇 |
2004年 | 213篇 |
2003年 | 196篇 |
2002年 | 231篇 |
2001年 | 328篇 |
2000年 | 303篇 |
1999年 | 272篇 |
1998年 | 130篇 |
1997年 | 171篇 |
1996年 | 181篇 |
1995年 | 183篇 |
1994年 | 148篇 |
1993年 | 170篇 |
1992年 | 245篇 |
1991年 | 219篇 |
1990年 | 214篇 |
1989年 | 251篇 |
1988年 | 254篇 |
1987年 | 212篇 |
1986年 | 210篇 |
1985年 | 230篇 |
1984年 | 193篇 |
1983年 | 238篇 |
1982年 | 176篇 |
1981年 | 164篇 |
1980年 | 160篇 |
1979年 | 232篇 |
1978年 | 184篇 |
1977年 | 165篇 |
1976年 | 153篇 |
1975年 | 129篇 |
1974年 | 119篇 |
1973年 | 127篇 |
1971年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
991.
R. Kumar R. Kapoor B. Mittal A. Kumar R. D. Mittal 《Indian journal of clinical biochemistry : IJCB》2003,18(2):209-215
Metabolic abnormalities were investigated in 44 stone patients with first time (group 1) and 56 with 2 times stone formation
(group 2), and in 25 normal individuals. 24hr urine was analysed spectrophotometrically for oxalate, calcium, magnesium, citrate,
uric acid, phosphate and creatinine. Hypocitraturia and hyperoxaluria were the common abnormalities in the stone formers.
Stone patients had significantly higher urinary oxalate, calcium and uric acid and lower phosphate than normal individuals.
Citrate/calcium and magnesium/calcium ratio were significantly high in normal individuals than stone formers. Patients in
group 2 excreted significantly higher urinary calcium and lower citrate that patients in group 1. Citrate/calcium ratio was
higher in group 1 than group 2. Hypocitraturia, hyperoxaluria, hypercalciuria and increased citrate/calcium and magnesium/calcium
ratio seem to be an essential risk factor for stone formation. Patients with recurrent stone formation could be distinguished
from patients with first time stone formation on the basis of urinary calcium and citrate. 相似文献
992.
This year marks the 25th anniversary of the discovery of crown ethers by C. J. Pedersen (see Mary R. Truter and C. J. Pedersen Endeavour, 30, 142, 1971). This article reviews some new developments in this important field. New crown ether and related ligand systems that contain organometallic redoxactive groups can complex and electrochemically detect cations (metals, ammonium) and anions (halide, nitrate) in polar solvents. Thus, they represent prototypes of novel molecular sensory devices of the future. 相似文献
993.
994.
Adam D. Moore 《Ethics and Information Technology》2016,18(1):41-49
In the United States the ascendancy of speech protection is due to an expansive and unjustified view of the value or primacy of free expression and access to information. This is perhaps understandable, given that privacy has been understood as a mere interest, whereas speech rights have been seen as more fundamental. I have argued elsewhere that the “mere interest” view of privacy is false. Privacy, properly defined, is a necessary condition for human well-being or flourishing. The opening section of this article will provide an overview of this theory. Next, after a few remarks on speech absolutism, privacy absolutism, and balancing theories, I will sketch several of the dominant argument strands that have been offered in support of presumptively weighty speech rights. While these arguments, taken together, establish that free speech is important, they do not support the view that speech should nearly always trump privacy. In final section I will present and defend a way to balance free speech and privacy claims. 相似文献
995.
A general input-to-state stability (ISS)-type small-gain result is presented. It specializes to a small-gain theorem for ISS operators, and it also recovers the classical statement for ISS systems in state-space form. In addition, we highlight applications to incrementally stable systems, detectable systems, and to interconnections of stable systems. 相似文献
996.
W.D. Reekie 《Research Policy》1973,2(3):246-264
In this paper the patenting activity of the international pharmaceutical industry in London between 1900 and 1966 is analysed. Although patent data as a measure of industrial activity is not without defects it can be used both as an adjunct to and as a surrogate for more conventional yardsticks such as concentration ratios, sales statistics and so on. The results indicate that patenting activity can be used as both an absolute and relative indicator of an industry's pace of technological change. They help pinpoint the international distribution of pharmaceutical research and development. If analysed by product or process they can aid in the understanding of why an industry's competitive behaviour is or is not primarily one of price rivalry. Finally, they illustrate the continuing role of the individual inventor. 相似文献
997.
While there is no universal logic of induction, the probabilitycalculus succeeds as a logic of induction in many contexts throughits use of several notions concerning inductive inference. Theyinclude Addition, through which low probabilities representdisbelief as opposed to ignorance; and Bayes property, whichcommits the calculus to a refute and rescale dynamicsfor incorporating new evidence. These notions are independentand it is urged that they be employed selectively accordingto needs of the problem at hand. It is shown that neither isadapted to inductive inference concerning some indeterministicsystems.
- 1 Introduction
- 2 Failure of demonstrations of universality
- 2.1 Working backwards
- 2.2 The surface logic
- 3 Framework
- 3.1 The properties
- 3.2 Boundaries
- 3.2.1 Universalcomparability
- 3.2.2 Transitivity
- 3.2.3 Monotonicity
- 3.2.2 Transitivity
- 3.2 Boundaries
- 4 Addition
- 4.1 The property: disbelief versus ignorance
- 4.2Boundaries
- 5 Bayes property
- 5.1 The property
- 5.2 Bayes' theorem
- 5.3Boundaries
- 5.3.1 Dogmatism of the priors
- 5.3.2 Impossibilityof prior ignorance
- 5.3.3 Accommodation of virtues
- 5.3.2 Impossibilityof prior ignorance
- 5.2 Bayes' theorem
- 6Real values
- 7 Sufficiency and independence
- 8 Illustrations
- 8.1 All properties retained
- 8.2 Bayes propertyonly retained
- 8.3 Induction without additivity and Bayes property
- 8.2 Bayes propertyonly retained
- 9Conclusion
- 2 Failure of demonstrations of universality
998.
R. Shukia S. B. Sharma D. Puri K. M. Prabhu P. S. Murthy 《Indian journal of clinical biochemistry : IJCB》2000,15(1):169-177
Many plants have been used for the treatment of diabetes mellitus in Indian system of medicine and in other ancient systems of the world. Out of these only a few have been evaluated as per modern system of medicine. From many such plants only extracts have been prepared and their usefulness evaluated in experimental diabetes in animals. In some plants likeAllium cepa, Allium sativum, Ficus bengalensis, Gymnema sylvestre, Pterocarpus marsupium etc. active hypoglycemic principles have been isolated and their mechanism of action studied. Most of them seem to act directly on pancreas (pancreatic effect) and stimulate insulin level in blood. Some have extra pancreatic effect also by acting directly on tissues like liver, muscle etc. and alter favourably the activities of the regulatory enzymes of glycolysis, gluconeogenesis and other pathways. Since the plant products have less side effects, they have the potential as good hypoglycemic drugs. They may also provide clues for the development of new and better oral drugs for diabetes. 相似文献
999.
Globalization has contributed to the dismantling of national boundaries, which have enabled firms to compete and conduct business on a wider scale [Held, D., McGrew, A., Goldblatt, D., & Perraton, J. (1999). Global transformations. Politics, economics and culture. Cambridge: Polity Press]. Firms can move freely between different markets using Internet-based technology. While access to such markets can provide firms with greater choice of suppliers and cost efficiencies, they need to be aware of challenges that can influence their business performance. With this in mind, we examine how these factors influenced Alcoa Alumina's drive to a global procurement platform through a global marketplace. The staged adoption process experienced at Alcoa Alumina offers a learning opportunity for other firms considering the transition to global marketplace. 相似文献
1000.
Rinchen D Bhutia Bhumika Upadhyay M Maneesh 《Indian journal of clinical biochemistry : IJCB》2006,21(2):39-41
The present study was designed to determine the association between extent of hepatocellular injury and plasma level of thiobarbituric
acid reactive substances (TBARS) in pre term infants with cholestasis. Preterm infants (<35 weeks gestation) admitted to the
neonatal intensive care unit were enrolled (with their parents informed consent) in either the ‘cholestasis’ group (if their
direct bilirubin was >2 mg/dl) (n=25) or in the control group (n=16). Blood samples for measurement of TBARS, direct bilirubin
and transaminases were obtained with-in 24 hours of enrollment. The cholestasis and control groups were comparable with respect
to gestational age, birth weight and Apgar score. Serum direct bilirubin, SGOT (EC 2.6.1.1) and SGPT (EC 2.6.1.2) levels were
significantly high in the cholestasis group. Plasma levels of TBARS in cholestasis group were correlated with SGOT (F=276.92;
P<0.0001) and SGPT (F=355.17; P<0.0001) and differed significantly between cholestatic and control infants. Our findings suggest
that oxidative stress in preterm infants with cholestasis is associated with hepatocellular injury. 相似文献