全文获取类型
收费全文 | 3942篇 |
免费 | 318篇 |
国内免费 | 7篇 |
专业分类
4267篇 |
出版年
2023年 | 18篇 |
2022年 | 53篇 |
2021年 | 92篇 |
2020年 | 44篇 |
2019年 | 59篇 |
2018年 | 70篇 |
2017年 | 61篇 |
2016年 | 93篇 |
2015年 | 199篇 |
2014年 | 197篇 |
2013年 | 225篇 |
2012年 | 346篇 |
2011年 | 273篇 |
2010年 | 184篇 |
2009年 | 132篇 |
2008年 | 199篇 |
2007年 | 215篇 |
2006年 | 196篇 |
2005年 | 163篇 |
2004年 | 153篇 |
2003年 | 146篇 |
2002年 | 127篇 |
2001年 | 84篇 |
2000年 | 77篇 |
1999年 | 88篇 |
1998年 | 39篇 |
1997年 | 36篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 24篇 |
1993年 | 20篇 |
1992年 | 42篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 27篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 31篇 |
1982年 | 31篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1974年 | 17篇 |
1973年 | 23篇 |
排序方式: 共有4267条查询结果,搜索用时 15 毫秒
1.
Yi-Wen Chiu Sangwon Suh Stephan Pfister Stefanie Hellweg Annette Koehler 《The International Journal of Life Cycle Assessment》2012,17(1):16-24
Purpose
Though the development of biofuel has attracted numerous studies for quantifying potential water demand applying life cycle thinking, the impacts of biofuel water consumption still remain unknown. In this study, we aimed to quantify ecological impact associated with corn-based bioethanol water consumption in Minnesota in responding to different refinery expansion scenarios by applying a life cycle impact assessment method. 相似文献2.
Study of the posterior abdominal epidermis in hypophysectomized/thyroidectomized male and female tokays following surgery, and subsequent androgen therapy, indicates that, contrary to a previous model, all aspects of β-gland differentiation are under direct androgenic control. On the other hand, another epidermal specialization, the digital foot-pad, shows a pattern of histogenesis directly comparable to that of β-glands, but is unaffected by androgens. These data are discussed with respect to the evolution of glandular epidermal specializations in gekkonid lizards and the possible role of androgens in modifying the control of cell differentiation in lizard epidermis. 相似文献
3.
4.
5.
Human metallothionein genes: structure of the functional locus at 16q13 总被引:21,自引:0,他引:21
The functional human metallothionein (MT) genes are located on chromosome 16q13. We have physically mapped the functional human MT locus by isolation and restriction digest mapping of cloned DNA. The mapped region contains all sequences on chromosome 16 that hybridize to metallothionein gene probes and comprises 14 tightly linked MT genes, 6 of which have not been previously described. This analysis defines the genetic limits of metallothionein functional diversity in the human genome. 相似文献
6.
7.
8.
B R Seckel S E Ryan R G Gagne T H Chiu E Watkins 《Plastic and reconstructive surgery》1986,78(6):793-800
Nerve regeneration across a gap in peripheral nerve has been achieved through various nonneural nerve guides in both lower and primate species. This technique can only be useful if the regenerated nerve cable grows specifically to and reinnervates the appropriate distal target. In this study, the proximal peroneal fascicle of rat sciatic nerve was inserted into the proximal limb of a Y-shaped nerve guide. Distal peroneal and tibial fascicles were placed within the two distal limbs of the same Y. The proximal peroneal nerve grew preferentially by a 2:1 ratio to the appropriate distal peroneal fascicle suggesting that target-specific reinnervation is possible through a nerve guide. 相似文献
9.
Isabel J. Wajda Miriam Banay-Schwartz Isaac Manigault Abel Lajtha 《Neurochemical research》1986,11(7):949-957
In vivo effects of chronic lithium administration on dopaminergic and serotonergic receptor binding were studied in the striatum and cerebral cortex of the rat. [3H]Domperidone was used as the ligand for the dopaminergic receptor, and [3H]ketanserin for the serotonergic system. Long-term ingestion of lithium (2–3 months) resulted in high levels of lithium in the cerebral cortex and significantly higher potassium levels; the sodium content remained at normal levels. The kinetic constants (K
d andB
max) of [3H]domperidone binding sites measured in the striatum did not show any deviation from control values, but the receptor concentration (B
max) of [3H]ketanserin binding sites was significantly reduced in the cerebral cortex of lithium-treated rats. The apparent dissociation constant (K
d) was not changed. The results indicate that the serotonergic component of the [3H]spiperone binding site, which we had previously found to be affected by chronic lithium treatment and which was shown by Peroutka and Snyder (1) to be the 5-HT2 receptor, is selectively affected by lithium.Special Issue dedicated to Prof. Eduardo De Robertis. 相似文献
10.
Helen M. Blau Cecelia Webster Choy-Pik Chiu Susan Guttman Frances Chandler 《Experimental cell research》1983,144(2):495-503
The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation. 相似文献