全文获取类型
收费全文 | 360篇 |
免费 | 42篇 |
出版年
2022年 | 4篇 |
2020年 | 3篇 |
2018年 | 5篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 13篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 19篇 |
2010年 | 8篇 |
2009年 | 11篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 15篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 11篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1969年 | 5篇 |
1967年 | 3篇 |
1963年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有402条查询结果,搜索用时 31 毫秒
1.
The heart rate and respiratory patterns in hypoxia are not well documented in unanaesthetized intact newborn animals. We studied heart rate and respiratory patterns during quiet sleep in 17% inspired O2 in 31 unanaesthetized newborns of five species: lamb, piglet, puppy, kitten, and rabbit. There was no significant change in mean heart rate and respiratory rate with hypoxia for any species. Brief apneas greater than 5 s were frequent (5-8/h), both in 21 and 17% O2 only in lambs and puppies. No sustained periodic breathing was induced by hypoxia. Thus, mild hypoxia has little steady-state effect on heart rate and respiratory rate and pattern in these unanaesthetized newborns. These findings are compatible with depressed chemoreceptor threshold, but indicate a remarkably mature respiratory pattern in full-term newborns of these species. 相似文献
2.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献3.
V Gaponenko E Abusamhadneh M B Abbott N Finley G Gasmi-Seabrook R J Solaro M Rance P R Rosevear 《The Journal of biological chemistry》1999,274(24):16681-16684
Conformational exchange has been demonstrated within the regulatory domain of calcium-saturated cardiac troponin C when bound to the NH2-terminal domain of cardiac troponin I-(1-80), and cardiac troponin I-(1-80)DD, having serine residues 23 and 24 mutated to aspartate to mimic the phosphorylated form of the protein. Binding of cardiac troponin I-(1-80) decreases conformational exchange for residues 29, 32, and 34. Comparison of average transverse cross correlation rates show that both the NH2- and COOH-terminal domains of cardiac troponin C tumble with similar correlation times when bound to cardiac troponin I-(1-80). In contrast, the NH2- and COOH-terminal domains in free cardiac troponin C and cardiac troponin C bound cardiac troponin I-(1-80)DD tumble independently. These results suggest that the nonphosphorylated cardiac specific NH2 terminus of cardiac troponin I interacts with the NH2-terminal domain of cardiac troponin C. 相似文献
4.
It is generally perceived that landscape patterns or textures in a given protected area are spatially stationary. The findings
of this study suggest that this common perception is only partially correct. Over the course of 52 years, equilibrium in landscape
shifting was detected using digital data for the Lassen Volcanic National Park (USA). Vertical aerial photographs taken of
the park in 1941 were geo-referenced with the digital orthophoto quarter quadrangle (DOQQ) images of the same area from 1993
to identify landscape compositions and to measure change. Spatial analysis was used to observe pattern changes over time.
The results suggested that landscape development maintained equilibrium while patches were in various stages of a successional
sequence. The total area of each landscape component held steady, although over time patches throughout the landscape changed—a
shifting-mosaic steady state (SMSS). These findings reflect the limitations of contemporary environmental conservation theory.
They also suggest the importance of considering landscape change in policies that currently govern park planning and management. 相似文献
5.
Summary The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals. 相似文献
6.
This investigation was conducted to assess the effects of mouse serum on chick skeletal muscle cell differentiation. In light of earlier findings of altered membrane phospholipid metabolism following mouse serum treatment of Friend erythroleukemic and chick chondrogenic cells, it was of interest to determine whether similar changes would modulate the fusion of mononucleated myoblasts, which is necessary for the formation of multinucleated skeletal muscle fibers. When mouse serum is added to low density cultures of enriched chick myoblasts shortly following cell attachment to the substratum, fusion is inhibited and neutral lipid accumulation ensues. There is an early inhibitory effect on DNA synthesis but not on protein synthesis. There is no increase in the uptake of 2-deoxyglucose following insulin stimulation of the cells, which suggests that while the cells are accumulating large amounts of lipid, they are not being converted into typical adipocytes. Finally, even in cultures of mouse serum-treated cells that undergo significant fusion, one observes thinner myotubes that do not spontaneously contract as do those of control cultures, as well as a disorganization of fluorescently stained actin and myosin myofilaments. These findings demonstrate that mouse serum acts in a dose-dependent manner, is not cytotoxic to the cells, but is capable of modulating normal developmental events of myoblasts as reported for other cell and tissue types. 相似文献
7.
8.
R A Mustard C Lipohar R J Finley J H Duff J Radziuk C Nohr 《Laboratory animal science》1986,36(4):393-395
Reliable short-term blood access in conscious swine was provided by implanting multiple silastic catheters. Catheters were inserted into the aorta, hepatic vein, portal vein, and inferior vena cava through a midline laparotomy incision. Multiple catheters also were placed into the external jugular vein through a separate cervical incision. Catheter patency rates for blood withdrawal on the sixth post-operative day were: arterial 100%, hepatic 91%, portal 86%, inferior vena cava 71%. No animal had major wound or catheter infection on the seventh post-operative day. The methods described allow metabolic studies, including measurements of splanchnic blood flow, to be carried out either acutely or for up to at least 7 days post-operatively. 相似文献
9.
I D Craig D T Shum P Desrosiers C McLeod M S Lefcoe N A Paterson R J Finley B Woods R J Anderson 《Acta cytologica》1983,27(6):647-650
A case of choriocarcinoma metastatic to the lung following a previous hydatidiform mole is presented. It was possible to make definitive identification of trophoblastic elements on a needle aspiration biopsy using an immunoperoxidase staining technique, thus avoiding diagnostic thoracotomy prior to therapeutic intervention. A method of immunoperoxidase staining of previously fixed and Papanicolaou-stained needle aspiration biopsy specimens is also described, and other uses of the immunoperoxidase technique on needle biopsy specimens are discussed. 相似文献